bd: backup 2026-03-04 17:07

feat(dfu): add firmware update controls to device page
bd: backup 2026-03-03 16:11
2026-03-04 18:07:18 +01:00 · 2026-03-04 18:07:12 +01:00 · 2026-03-03 17:11:51 +01:00 · 2026-03-03 17:11:47 +01:00 · 2026-03-03 17:06:54 +01:00 · 2026-03-03 17:00:37 +01:00
38 changed files with 3555 additions and 144 deletions
--- a/.beads/.gitignore
+++ b/.beads/.gitignore
@ -0,0 +1,49 @@
+# Dolt database (managed by Dolt, not git)
+dolt/
+dolt-access.lock
+
+# Runtime files
+bd.sock
+bd.sock.startlock
+sync-state.json
+last-touched
+
+# Local version tracking (prevents upgrade notification spam after git ops)
+.local_version
+
+# Worktree redirect file (contains relative path to main repo's .beads/)
+# Must not be committed as paths would be wrong in other clones
+redirect
+
+# Sync state (local-only, per-machine)
+# These files are machine-specific and should not be shared across clones
+.sync.lock
+export-state/
+
+# Ephemeral store (SQLite - wisps/molecules, intentionally not versioned)
+ephemeral.sqlite3
+ephemeral.sqlite3-journal
+ephemeral.sqlite3-wal
+ephemeral.sqlite3-shm
+
+# Dolt server management (auto-started by bd)
+dolt-server.pid
+dolt-server.log
+dolt-server.lock
+
+# Legacy files (from pre-Dolt versions)
+*.db
+*.db?*
+*.db-journal
+*.db-wal
+*.db-shm
+db.sqlite
+bd.db
+daemon.lock
+daemon.log
+daemon-*.log.gz
+daemon.pid
+# NOTE: Do NOT add negation patterns here.
+# They would override fork protection in .git/info/exclude.
+# Config files (metadata.json, config.yaml) are tracked by git by default
+# since no pattern above ignores them.
--- a/.beads/README.md
+++ b/.beads/README.md
@ -0,0 +1,81 @@
+# Beads - AI-Native Issue Tracking
+
+Welcome to Beads! This repository uses **Beads** for issue tracking - a modern, AI-native tool designed to live directly in your codebase alongside your code.
+
+## What is Beads?
+
+Beads is issue tracking that lives in your repo, making it perfect for AI coding agents and developers who want their issues close to their code. No web UI required - everything works through the CLI and integrates seamlessly with git.
+
+**Learn more:** [github.com/steveyegge/beads](https://github.com/steveyegge/beads)
+
+## Quick Start
+
+### Essential Commands
+
+```bash
+# Create new issues
+bd create "Add user authentication"
+
+# View all issues
+bd list
+
+# View issue details
+bd show <issue-id>
+
+# Update issue status
+bd update <issue-id> --claim
+bd update <issue-id> --status done
+
+# Sync with Dolt remote
+bd dolt push
+```
+
+### Working with Issues
+
+Issues in Beads are:
+- **Git-native**: Stored in `.beads/issues.jsonl` and synced like code
+- **AI-friendly**: CLI-first design works perfectly with AI coding agents
+- **Branch-aware**: Issues can follow your branch workflow
+- **Always in sync**: Auto-syncs with your commits
+
+## Why Beads?
+
+✨ **AI-Native Design**
+- Built specifically for AI-assisted development workflows
+- CLI-first interface works seamlessly with AI coding agents
+- No context switching to web UIs
+
+🚀 **Developer Focused**
+- Issues live in your repo, right next to your code
+- Works offline, syncs when you push
+- Fast, lightweight, and stays out of your way
+
+🔧 **Git Integration**
+- Automatic sync with git commits
+- Branch-aware issue tracking
+- Intelligent JSONL merge resolution
+
+## Get Started with Beads
+
+Try Beads in your own projects:
+
+```bash
+# Install Beads
+curl -sSL https://raw.githubusercontent.com/steveyegge/beads/main/scripts/install.sh | bash
+
+# Initialize in your repo
+bd init
+
+# Create your first issue
+bd create "Try out Beads"
+```
+
+## Learn More
+
+- **Documentation**: [github.com/steveyegge/beads/docs](https://github.com/steveyegge/beads/tree/main/docs)
+- **Quick Start Guide**: Run `bd quickstart`
+- **Examples**: [github.com/steveyegge/beads/examples](https://github.com/steveyegge/beads/tree/main/examples)
+
+---
+
+*Beads: Issue tracking that moves at the speed of thought* ⚡
--- a/.beads/backup/backup_state.json
+++ b/.beads/backup/backup_state.json
@ -0,0 +1,13 @@
+{
+  "last_dolt_commit": "mf3is3p9ve79on2q1achdjp8v50rq6s3",
+  "last_event_id": 0,
+  "timestamp": "2026-03-04T17:07:18.317614374Z",
+  "counts": {
+    "issues": 10,
+    "events": 24,
+    "comments": 0,
+    "dependencies": 21,
+    "labels": 0,
+    "config": 11
+  }
+}
--- a/.beads/backup/comments.jsonl
+++ b/.beads/backup/comments.jsonl
--- a/.beads/backup/config.jsonl
+++ b/.beads/backup/config.jsonl
@ -0,0 +1,11 @@
+{"key":"auto_compact_enabled","value":"false"}
+{"key":"compact_batch_size","value":"50"}
+{"key":"compact_parallel_workers","value":"5"}
+{"key":"compact_tier1_days","value":"30"}
+{"key":"compact_tier1_dep_levels","value":"2"}
+{"key":"compact_tier2_commits","value":"100"}
+{"key":"compact_tier2_days","value":"90"}
+{"key":"compact_tier2_dep_levels","value":"5"}
+{"key":"compaction_enabled","value":"false"}
+{"key":"issue_prefix","value":"abawo_bt_app"}
+{"key":"schema_version","value":"6"}
--- a/.beads/backup/dependencies.jsonl
+++ b/.beads/backup/dependencies.jsonl
@ -0,0 +1,21 @@
+{"created_at":"2026-03-03T16:38:33Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.1","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:10Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.2","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.1","issue_id":"abawo_bt_app-20q.2","type":"blocks"}
+{"created_at":"2026-03-03T16:39:10Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.3","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.4","issue_id":"abawo_bt_app-20q.3","type":"blocks"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.7","issue_id":"abawo_bt_app-20q.3","type":"blocks"}
+{"created_at":"2026-03-03T16:39:10Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.4","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:10Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.5","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.7","issue_id":"abawo_bt_app-20q.5","type":"blocks"}
+{"created_at":"2026-03-03T16:39:10Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.6","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.3","issue_id":"abawo_bt_app-20q.6","type":"blocks"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.5","issue_id":"abawo_bt_app-20q.6","type":"blocks"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.9","issue_id":"abawo_bt_app-20q.6","type":"blocks"}
+{"created_at":"2026-03-03T16:39:17Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.7","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.1","issue_id":"abawo_bt_app-20q.7","type":"blocks"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.2","issue_id":"abawo_bt_app-20q.7","type":"blocks"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.8","issue_id":"abawo_bt_app-20q.7","type":"blocks"}
+{"created_at":"2026-03-03T16:39:23Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.8","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.1","issue_id":"abawo_bt_app-20q.8","type":"blocks"}
+{"created_at":"2026-03-03T16:39:28Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q","issue_id":"abawo_bt_app-20q.9","type":"parent-child"}
+{"created_at":"2026-03-03T16:39:47Z","created_by":"Yandrik","depends_on_id":"abawo_bt_app-20q.7","issue_id":"abawo_bt_app-20q.9","type":"blocks"}
--- a/.beads/backup/events.jsonl
+++ b/.beads/backup/events.jsonl
@ -0,0 +1,24 @@
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:37:50Z","event_type":"created","id":1,"issue_id":"abawo_bt_app-20q","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:38:33Z","event_type":"created","id":2,"issue_id":"abawo_bt_app-20q.1","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:10Z","event_type":"created","id":3,"issue_id":"abawo_bt_app-20q.2","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:10Z","event_type":"created","id":5,"issue_id":"abawo_bt_app-20q.3","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:10Z","event_type":"created","id":7,"issue_id":"abawo_bt_app-20q.4","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:10Z","event_type":"created","id":9,"issue_id":"abawo_bt_app-20q.5","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:10Z","event_type":"created","id":10,"issue_id":"abawo_bt_app-20q.6","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:17Z","event_type":"created","id":11,"issue_id":"abawo_bt_app-20q.7","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:23Z","event_type":"created","id":12,"issue_id":"abawo_bt_app-20q.8","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:39:28Z","event_type":"created","id":13,"issue_id":"abawo_bt_app-20q.9","new_value":"","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:43:26Z","event_type":"claimed","id":14,"issue_id":"abawo_bt_app-20q.1","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.1\",\"title\":\"Add DFU protocol constants and domain models\",\"description\":\"Add protocol surface in app code for DFU support.\\n\\nWork:\\n- Add UUID constants for dfu_control (...40008), dfu_data (...40009), dfu_ack (...4000a)\\n- Add opcode/frame constants (START=0x01, FINISH=0x02, ABORT=0x03, frame size 64, payload size 63)\\n- Add flags constants and typed update-state/progress models used by service/UI\\n- Remove future magic numbers by centralizing constants\",\"acceptance_criteria\":\"- All protocol constants match spec exactly\\n- No duplicated literal DFU UUID/opcode values across services/UI\\n- Domain models compile and are ready for transfer engine integration\",\"status\":\"open\",\"priority\":1,\"issue_type\":\"task\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:38:34Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:38:34Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:45:19Z","event_type":"closed","id":15,"issue_id":"abawo_bt_app-20q.1","new_value":"Implemented DFU constants, flags, opcodes, and typed progress models in shifter_types.dart","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:45:29Z","event_type":"claimed","id":16,"issue_id":"abawo_bt_app-20q.2","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.2\",\"title\":\"Implement DFU packet codec and CRC32 utilities with tests\",\"description\":\"Implement pure protocol helpers.\\n\\nWork:\\n- Build START payload (11 bytes, LE fields)\\n- Build FINISH/ABORT payloads\\n- Build/segment DATA frames (seq + 63-byte payload)\\n- Implement ACK/sequence helpers including wrapping behavior\\n- Implement CRC32 (ISO-HDLC reflected polynomial 0xEDB88320, init/final xor FFFFFFFF)\",\"acceptance_criteria\":\"- CRC test vector passes: \\\"123456789\\\" =\\u003e 0xCBF43926\\n- START/FINISH/ABORT encoders produce exact lengths/byte layout\\n- Frame segmentation handles final partial payload correctly\\n- Seq wrap and ack+1 rewind helpers covered by tests\",\"status\":\"open\",\"priority\":1,\"issue_type\":\"task\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:39:10Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:39:10Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:48:57Z","event_type":"closed","id":17,"issue_id":"abawo_bt_app-20q.2","new_value":"Added DFU protocol codec/CRC utilities with unit tests for payloads, frames, and sequence helpers","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:49:06Z","event_type":"claimed","id":18,"issue_id":"abawo_bt_app-20q.8","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.8\",\"title\":\"Add BLE DFU preflight checks (MTU and connection readiness)\",\"description\":\"Add runtime guards required for protocol correctness.\\n\\nWork:\\n- Ensure active connection to target button before DFU start\\n- Request elevated MTU (e.g. 128/247) before upload\\n- Validate negotiated MTU supports 64-byte data writes (ATT payload requirement)\\n- Fail early with actionable message when transport preconditions are not met\",\"acceptance_criteria\":\"- Upload start is blocked when MTU/connection preconditions fail\\n- Error messages explain what failed and next step\\n- Preflight result is exposed for transfer start path\",\"status\":\"open\",\"priority\":1,\"issue_type\":\"task\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:39:24Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:39:24Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:55:10Z","event_type":"closed","id":19,"issue_id":"abawo_bt_app-20q.8","new_value":"Implemented DFU preflight checks for connection state and negotiated MTU with typed results and tests","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T16:55:19Z","event_type":"claimed","id":20,"issue_id":"abawo_bt_app-20q.7","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.7\",\"title\":\"Implement BLE DFU transfer engine with cumulative ACK retransmit\",\"description\":\"Build the runtime transfer engine used by UI.\\n\\nWork:\\n- Subscribe to dfu_ack indications before START\\n- Send START and require initial ACK 0xFF\\n- Stream dfu_data using write without response in windows (configurable, default 8)\\n- Track cumulative ACK; on stall/timeout rewind to ack+1 (wrapping aware)\\n- Handle invalid/no-progress scenarios with bounded retries\\n- Send FINISH after full acked upload\\n- Support ABORT for cancellation and terminal error cleanup\\n- Emit state/progress stream for UI\",\"acceptance_criteria\":\"- Happy path reaches done with full ACKed transfer\\n- Loss/stall path retransmits and recovers correctly\\n- Cancel triggers ABORT and returns to idle cleanly\\n- Engine surfaces explicit error reasons for UI\",\"status\":\"open\",\"priority\":1,\"issue_type\":\"feature\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:39:18Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:39:18Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T17:00:44Z","event_type":"closed","id":21,"issue_id":"abawo_bt_app-20q.7","new_value":"Implemented firmware transfer engine with preflight, cumulative ACK handling, retries, cancel ABORT, and unit tests","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T17:01:01Z","event_type":"claimed","id":22,"issue_id":"abawo_bt_app-20q.4","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.4\",\"title\":\"Add firmware file selection and binary validation flow\",\"description\":\"Implement local firmware artifact input for v1.\\n\\nWork:\\n- Integrate file picker for local firmware .bin\\n- Read bytes safely and validate non-empty payload\\n- Guard against malformed selections and unsupported files\\n- Compute total_len and crc32 from selected bytes\\n- Generate per-session session_id and set flags=0x00 for v1\",\"acceptance_criteria\":\"- User can select .bin and app obtains byte payload\\n- Validation errors are explicit and user-facing\\n- Metadata (size/crc/session) is available to transfer engine\",\"status\":\"open\",\"priority\":2,\"issue_type\":\"task\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:39:10Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:39:10Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T17:04:51Z","event_type":"closed","id":23,"issue_id":"abawo_bt_app-20q.4","new_value":"Completed","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T17:07:21Z","event_type":"claimed","id":24,"issue_id":"abawo_bt_app-20q.9","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.9\",\"title\":\"Handle post-FINISH disconnect/reboot and reconnect verification\",\"description\":\"Implement robust completion handling around expected device reset.\\n\\nWork:\\n- Treat disconnect after successful FINISH as expected behavior\\n- Reconnect with update-specific timeout strategy\\n- Verify device is reachable/readable after reconnect\\n- Surface success only after reconnect verification path\\n- Document limitation: no strict firmware version compare until firmware exposes version characteristic\",\"acceptance_criteria\":\"- Expected reset does not appear as generic failure\\n- Reconnect path is attempted and result is surfaced\\n- Completion criteria are consistent with v1 definition\",\"status\":\"open\",\"priority\":1,\"issue_type\":\"task\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:39:28Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:39:28Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T17:12:02Z","event_type":"closed","id":25,"issue_id":"abawo_bt_app-20q.9","new_value":"Added post-FINISH reset disconnect, reconnect, and reachability verification before marking update complete","old_value":""}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-03T17:12:17Z","event_type":"claimed","id":26,"issue_id":"abawo_bt_app-20q.3","new_value":"{\"assignee\":\"Yandrik\",\"status\":\"in_progress\"}","old_value":"{\"id\":\"abawo_bt_app-20q.3\",\"title\":\"Integrate firmware update UI into device details page\",\"description\":\"Add user-facing update controls and status presentation.\\n\\nWork:\\n- Add update card with Select Firmware, Start Update, Cancel\\n- Show phase text, progress %, bytes sent/acked, and retry status\\n- Disable conflicting actions (gear writes / connect button-to-bike) during DFU\\n- Show explicit reboot expectation after FINISH\\n- Persist/clear transient state correctly on page lifecycle changes\",\"acceptance_criteria\":\"- UI can run full update flow start-to-finish\\n- Progress/state transitions are visible and consistent\\n- Conflicting controls are disabled during active transfer\\n- Failures and cancellations are clearly shown\",\"status\":\"open\",\"priority\":1,\"issue_type\":\"feature\",\"owner\":\"me@yandrik.dev\",\"created_at\":\"2026-03-03T15:39:10Z\",\"created_by\":\"Yandrik\",\"updated_at\":\"2026-03-03T15:39:10Z\"}"}
+{"actor":"Yandrik","comment":null,"created_at":"2026-03-04T18:07:17Z","event_type":"closed","id":27,"issue_id":"abawo_bt_app-20q.3","new_value":"Integrated firmware file selection, update controls, progress display, and DFU state handling into device details page","old_value":""}
--- a/.beads/backup/issues.jsonl
+++ b/.beads/backup/issues.jsonl
@ -0,0 +1,10 @@
+{"acceptance_criteria":"- User can select a firmware .bin and complete upload end-to-end\n- Upload follows protocol and handles packet loss via retransmit\n- App shows clear progress and failure states\n- Device reconnects after reboot and is reachable","actor":"","agent_state":"","assignee":null,"await_id":"","await_type":"","close_reason":"","closed_at":null,"closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"c3bd8fa9b5b9d51b04cde5e11c2d8cdedaca29e049a64e8521172a69093b4ba3","created_at":"2026-03-03T15:37:50Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Implement the firmware update flow defined in universal-shifters/update-process.md for the Flutter app.\n\nScope:\n- Manual local .bin selection and upload over BLE GATT\n- START/DATA/FINISH/ABORT protocol support\n- Cumulative ACK handling with retransmit\n- Expected reboot/disconnect handling and reconnect check\n\nOut of scope for v1:\n- Hosted firmware distribution/backend\n- Cryptographic signature verification in app\n- Encrypted payload transport mode","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q","is_template":0,"issue_type":"epic","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"open","target":"","timeout_ns":0,"title":"Implement Universal Shifters BLE DFU v1 in app (manual .bin upload)","updated_at":"2026-03-03T15:37:50Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- All protocol constants match spec exactly\n- No duplicated literal DFU UUID/opcode values across services/UI\n- Domain models compile and are ready for transfer engine integration","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Implemented DFU constants, flags, opcodes, and typed progress models in shifter_types.dart","closed_at":"2026-03-03T15:45:20Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"d471157a1af6199f0ac0a1565b05b28d1a477e66d9166a3865edb42ea1e8c2ae","created_at":"2026-03-03T15:38:34Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Add protocol surface in app code for DFU support.\n\nWork:\n- Add UUID constants for dfu_control (...40008), dfu_data (...40009), dfu_ack (...4000a)\n- Add opcode/frame constants (START=0x01, FINISH=0x02, ABORT=0x03, frame size 64, payload size 63)\n- Add flags constants and typed update-state/progress models used by service/UI\n- Remove future magic numbers by centralizing constants","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.1","is_template":0,"issue_type":"task","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Add DFU protocol constants and domain models","updated_at":"2026-03-03T15:45:20Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- CRC test vector passes: \"123456789\" =\u003e 0xCBF43926\n- START/FINISH/ABORT encoders produce exact lengths/byte layout\n- Frame segmentation handles final partial payload correctly\n- Seq wrap and ack+1 rewind helpers covered by tests","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Added DFU protocol codec/CRC utilities with unit tests for payloads, frames, and sequence helpers","closed_at":"2026-03-03T15:48:57Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"9ba609e63c9e2f8a4e95de6795dace11c610aa9c13908b5dab7aa6cb83ab58d4","created_at":"2026-03-03T15:39:10Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Implement pure protocol helpers.\n\nWork:\n- Build START payload (11 bytes, LE fields)\n- Build FINISH/ABORT payloads\n- Build/segment DATA frames (seq + 63-byte payload)\n- Implement ACK/sequence helpers including wrapping behavior\n- Implement CRC32 (ISO-HDLC reflected polynomial 0xEDB88320, init/final xor FFFFFFFF)","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.2","is_template":0,"issue_type":"task","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Implement DFU packet codec and CRC32 utilities with tests","updated_at":"2026-03-03T15:48:57Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- UI can run full update flow start-to-finish\n- Progress/state transitions are visible and consistent\n- Conflicting controls are disabled during active transfer\n- Failures and cancellations are clearly shown","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Integrated firmware file selection, update controls, progress display, and DFU state handling into device details page","closed_at":"2026-03-04T17:07:18Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"e8d2f905536263a05de5e7e86bf8f02fa0491d7129e30f36f2c4dd09acab1882","created_at":"2026-03-03T15:39:10Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Add user-facing update controls and status presentation.\n\nWork:\n- Add update card with Select Firmware, Start Update, Cancel\n- Show phase text, progress %, bytes sent/acked, and retry status\n- Disable conflicting actions (gear writes / connect button-to-bike) during DFU\n- Show explicit reboot expectation after FINISH\n- Persist/clear transient state correctly on page lifecycle changes","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.3","is_template":0,"issue_type":"feature","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Integrate firmware update UI into device details page","updated_at":"2026-03-04T17:07:18Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- User can select .bin and app obtains byte payload\n- Validation errors are explicit and user-facing\n- Metadata (size/crc/session) is available to transfer engine","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Completed","closed_at":"2026-03-03T16:04:51Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"be8d8646593e4fc6c269383efb41808c40ffdfb3103e58a90acc0142e32f4711","created_at":"2026-03-03T15:39:10Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Implement local firmware artifact input for v1.\n\nWork:\n- Integrate file picker for local firmware .bin\n- Read bytes safely and validate non-empty payload\n- Guard against malformed selections and unsupported files\n- Compute total_len and crc32 from selected bytes\n- Generate per-session session_id and set flags=0x00 for v1","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.4","is_template":0,"issue_type":"task","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":2,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Add firmware file selection and binary validation flow","updated_at":"2026-03-03T16:04:51Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- Tests cover success and critical failure/retry paths\n- Wrap-around and ack rewind behavior is validated\n- Regressions in sequencing/CRC are caught automatically","actor":"","agent_state":"","assignee":null,"await_id":"","await_type":"","close_reason":"","closed_at":null,"closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"f784095261bfc41eed5544a567f667bb2ba4816433f1d5d6ae21ea4616c7109a","created_at":"2026-03-03T15:39:10Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Add targeted tests for protocol and engine behavior.\n\nWork:\n- Unit tests for codec + CRC + sequence helpers\n- Engine tests with mocked BLE ack stream for:\n  - happy path\n  - dropped frame / stalled ACK and rewind\n  - timeout and bounded retry fail\n  - cancel/abort cleanup\n- Ensure deterministic tests for wrap-around sequence scenarios","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.5","is_template":0,"issue_type":"task","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"open","target":"","timeout_ns":0,"title":"Add DFU test suite for happy path, loss, stalls, and cancel","updated_at":"2026-03-03T15:39:10Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- Team can execute update and triage failures from docs\n- v1 limitations are explicit and not ambiguous\n- QA checklist is actionable and complete","actor":"","agent_state":"","assignee":null,"await_id":"","await_type":"","close_reason":"","closed_at":null,"closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"3a5dd3fd4d901ae53a80b3c7b488b41db5e09f7cc50da0e6c185c075b8ad7e51","created_at":"2026-03-03T15:39:10Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Document how to use and support the new updater.\n\nWork:\n- Add app-side DFU flow docs (select/start/progress/reboot/reconnect)\n- Add troubleshooting matrix for common failures (MTU, stalled ACK, reconnect timeout, CRC mismatch)\n- Record explicit v1 limitations and future security/version-verification roadmap\n- Add manual QA checklist for release validation","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.6","is_template":0,"issue_type":"chore","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":2,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"open","target":"","timeout_ns":0,"title":"Document DFU v1 operator flow, troubleshooting, and constraints","updated_at":"2026-03-03T15:39:10Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- Happy path reaches done with full ACKed transfer\n- Loss/stall path retransmits and recovers correctly\n- Cancel triggers ABORT and returns to idle cleanly\n- Engine surfaces explicit error reasons for UI","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Implemented firmware transfer engine with preflight, cumulative ACK handling, retries, cancel ABORT, and unit tests","closed_at":"2026-03-03T16:00:45Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"042d39f373b05c758d2d2724c757a7e790de522c2def68f8f12e9f2fbbb70dc6","created_at":"2026-03-03T15:39:18Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Build the runtime transfer engine used by UI.\n\nWork:\n- Subscribe to dfu_ack indications before START\n- Send START and require initial ACK 0xFF\n- Stream dfu_data using write without response in windows (configurable, default 8)\n- Track cumulative ACK; on stall/timeout rewind to ack+1 (wrapping aware)\n- Handle invalid/no-progress scenarios with bounded retries\n- Send FINISH after full acked upload\n- Support ABORT for cancellation and terminal error cleanup\n- Emit state/progress stream for UI","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.7","is_template":0,"issue_type":"feature","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Implement BLE DFU transfer engine with cumulative ACK retransmit","updated_at":"2026-03-03T16:00:45Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- Upload start is blocked when MTU/connection preconditions fail\n- Error messages explain what failed and next step\n- Preflight result is exposed for transfer start path","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Implemented DFU preflight checks for connection state and negotiated MTU with typed results and tests","closed_at":"2026-03-03T15:55:11Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"558fa59b42c42b122eefc43d3483d1a61bdd995464dbc36d166f763f42366e87","created_at":"2026-03-03T15:39:24Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Add runtime guards required for protocol correctness.\n\nWork:\n- Ensure active connection to target button before DFU start\n- Request elevated MTU (e.g. 128/247) before upload\n- Validate negotiated MTU supports 64-byte data writes (ATT payload requirement)\n- Fail early with actionable message when transport preconditions are not met","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.8","is_template":0,"issue_type":"task","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Add BLE DFU preflight checks (MTU and connection readiness)","updated_at":"2026-03-03T15:55:11Z","waiters":"","wisp_type":"","work_type":""}
+{"acceptance_criteria":"- Expected reset does not appear as generic failure\n- Reconnect path is attempted and result is surfaced\n- Completion criteria are consistent with v1 definition","actor":"","agent_state":"","assignee":"Yandrik","await_id":"","await_type":"","close_reason":"Added post-FINISH reset disconnect, reconnect, and reachability verification before marking update complete","closed_at":"2026-03-03T16:12:02Z","closed_by_session":"","compacted_at":null,"compacted_at_commit":null,"compaction_level":0,"content_hash":"024e8aa245b93098013fbd66102a621c9ecd58a1dda9fc276c74cd278bdd3512","created_at":"2026-03-03T15:39:28Z","created_by":"Yandrik","crystallizes":0,"defer_until":null,"description":"Implement robust completion handling around expected device reset.\n\nWork:\n- Treat disconnect after successful FINISH as expected behavior\n- Reconnect with update-specific timeout strategy\n- Verify device is reachable/readable after reconnect\n- Surface success only after reconnect verification path\n- Document limitation: no strict firmware version compare until firmware exposes version characteristic","design":"","due_at":null,"ephemeral":0,"estimated_minutes":null,"event_kind":"","external_ref":null,"hook_bead":"","id":"abawo_bt_app-20q.9","is_template":0,"issue_type":"task","last_activity":null,"metadata":"{}","mol_type":"","notes":"","original_size":null,"owner":"me@yandrik.dev","payload":"","pinned":0,"priority":1,"quality_score":null,"rig":"","role_bead":"","role_type":"","sender":"","source_repo":"","source_system":"","spec_id":"","status":"closed","target":"","timeout_ns":0,"title":"Handle post-FINISH disconnect/reboot and reconnect verification","updated_at":"2026-03-03T16:12:02Z","waiters":"","wisp_type":"","work_type":""}
--- a/.beads/backup/labels.jsonl
+++ b/.beads/backup/labels.jsonl
--- a/.beads/config.yaml
+++ b/.beads/config.yaml
@ -0,0 +1,55 @@
+# Beads Configuration File
+# This file configures default behavior for all bd commands in this repository
+# All settings can also be set via environment variables (BD_* prefix)
+# or overridden with command-line flags
+
+# Issue prefix for this repository (used by bd init)
+# If not set, bd init will auto-detect from directory name
+# Example: issue-prefix: "myproject" creates issues like "myproject-1", "myproject-2", etc.
+# issue-prefix: ""
+
+# Use no-db mode: load from JSONL, write back after each command
+# When true, bd will use .beads/issues.jsonl as the source of truth
+# instead of the Dolt database
+# no-db: false
+
+# Enable JSON output by default
+# json: false
+
+# Feedback title formatting for mutating commands (create/update/close/dep/edit)
+# 0 = hide titles, N > 0 = truncate to N characters
+# output:
+#   title-length: 255
+
+# Default actor for audit trails (overridden by BD_ACTOR or --actor)
+# actor: ""
+
+# Export events (audit trail) to .beads/events.jsonl on each flush/sync
+# When enabled, new events are appended incrementally using a high-water mark.
+# Use 'bd export --events' to trigger manually regardless of this setting.
+# events-export: false
+
+# Multi-repo configuration (experimental - bd-307)
+# Allows hydrating from multiple repositories and routing writes to the correct JSONL
+# repos:
+#   primary: "."  # Primary repo (where this database lives)
+#   additional:   # Additional repos to hydrate from (read-only)
+#     - ~/beads-planning  # Personal planning repo
+#     - ~/work-planning   # Work planning repo
+
+# JSONL backup (periodic export for off-machine recovery)
+# Auto-enabled when a git remote exists. Override explicitly:
+# backup:
+#   enabled: false     # Disable auto-backup entirely
+#   interval: 15m      # Minimum time between auto-exports
+#   git-push: false    # Disable git push (export locally only)
+#   git-repo: ""       # Separate git repo for backups (default: project repo)
+
+# Integration settings (access with 'bd config get/set')
+# These are stored in the database, not in this file:
+# - jira.url
+# - jira.project
+# - linear.url
+# - linear.api-key
+# - github.org
+# - github.repo
--- a/.beads/dolt-monitor.pid
+++ b/.beads/dolt-monitor.pid
@ -0,0 +1 @@
+48179
--- a/.beads/dolt-server.activity
+++ b/.beads/dolt-server.activity
@ -0,0 +1 @@
+1772550918
--- a/.beads/dolt-server.port
+++ b/.beads/dolt-server.port
@ -0,0 +1 @@
+13365
--- a/.beads/hooks/post-checkout
+++ b/.beads/hooks/post-checkout
@ -0,0 +1,9 @@
+#!/usr/bin/env sh
+# --- BEGIN BEADS INTEGRATION v0.57.0 ---
+# This section is managed by beads. Do not remove these markers.
+if command -v bd >/dev/null 2>&1; then
+  export BD_GIT_HOOK=1
+  bd hooks run post-checkout "$@"
+  _bd_exit=$?; if [ $_bd_exit -ne 0 ]; then exit $_bd_exit; fi
+fi
+# --- END BEADS INTEGRATION ---
--- a/.beads/hooks/post-merge
+++ b/.beads/hooks/post-merge
@ -0,0 +1,9 @@
+#!/usr/bin/env sh
+# --- BEGIN BEADS INTEGRATION v0.57.0 ---
+# This section is managed by beads. Do not remove these markers.
+if command -v bd >/dev/null 2>&1; then
+  export BD_GIT_HOOK=1
+  bd hooks run post-merge "$@"
+  _bd_exit=$?; if [ $_bd_exit -ne 0 ]; then exit $_bd_exit; fi
+fi
+# --- END BEADS INTEGRATION ---
--- a/.beads/hooks/pre-commit
+++ b/.beads/hooks/pre-commit
@ -0,0 +1,9 @@
+#!/usr/bin/env sh
+# --- BEGIN BEADS INTEGRATION v0.57.0 ---
+# This section is managed by beads. Do not remove these markers.
+if command -v bd >/dev/null 2>&1; then
+  export BD_GIT_HOOK=1
+  bd hooks run pre-commit "$@"
+  _bd_exit=$?; if [ $_bd_exit -ne 0 ]; then exit $_bd_exit; fi
+fi
+# --- END BEADS INTEGRATION ---
--- a/.beads/hooks/pre-push
+++ b/.beads/hooks/pre-push
@ -0,0 +1,9 @@
+#!/usr/bin/env sh
+# --- BEGIN BEADS INTEGRATION v0.57.0 ---
+# This section is managed by beads. Do not remove these markers.
+if command -v bd >/dev/null 2>&1; then
+  export BD_GIT_HOOK=1
+  bd hooks run pre-push "$@"
+  _bd_exit=$?; if [ $_bd_exit -ne 0 ]; then exit $_bd_exit; fi
+fi
+# --- END BEADS INTEGRATION ---
--- a/.beads/hooks/prepare-commit-msg
+++ b/.beads/hooks/prepare-commit-msg
@ -0,0 +1,9 @@
+#!/usr/bin/env sh
+# --- BEGIN BEADS INTEGRATION v0.57.0 ---
+# This section is managed by beads. Do not remove these markers.
+if command -v bd >/dev/null 2>&1; then
+  export BD_GIT_HOOK=1
+  bd hooks run prepare-commit-msg "$@"
+  _bd_exit=$?; if [ $_bd_exit -ne 0 ]; then exit $_bd_exit; fi
+fi
+# --- END BEADS INTEGRATION ---
--- a/.beads/interactions.jsonl
+++ b/.beads/interactions.jsonl
--- a/.beads/metadata.json
+++ b/.beads/metadata.json
@ -0,0 +1,6 @@
+{
+  "database": "dolt",
+  "backend": "dolt",
+  "dolt_mode": "server",
+  "dolt_database": "abawo_bt_app"
+}
--- a/.gitignore
+++ b/.gitignore
@ -44,3 +44,7 @@ app.*.map.json
 /android/app/profile
 /android/app/release
 .aider*
+
+# Dolt database files (added by bd init)
+.dolt/
+*.db
--- a/AGENTS.md
+++ b/AGENTS.md
@ -0,0 +1,150 @@
+# Agent Instructions
+
+This project uses **bd** (beads) for issue tracking. Run `bd onboard` to get started.
+
+## Quick Reference
+
+```bash
+bd ready              # Find available work
+bd show <id>          # View issue details
+bd update <id> --claim  # Claim work atomically
+bd close <id>         # Complete work
+bd sync               # Sync with git
+```
+
+## Non-Interactive Shell Commands
+
+**ALWAYS use non-interactive flags** with file operations to avoid hanging on confirmation prompts.
+
+Shell commands like `cp`, `mv`, and `rm` may be aliased to include `-i` (interactive) mode on some systems, causing the agent to hang indefinitely waiting for y/n input.
+
+**Use these forms instead:**
+```bash
+# Force overwrite without prompting
+cp -f source dest           # NOT: cp source dest
+mv -f source dest           # NOT: mv source dest
+rm -f file                  # NOT: rm file
+
+# For recursive operations
+rm -rf directory            # NOT: rm -r directory
+cp -rf source dest          # NOT: cp -r source dest
+```
+
+**Other commands that may prompt:**
+- `scp` - use `-o BatchMode=yes` for non-interactive
+- `ssh` - use `-o BatchMode=yes` to fail instead of prompting
+- `apt-get` - use `-y` flag
+- `brew` - use `HOMEBREW_NO_AUTO_UPDATE=1` env var
+
+<!-- BEGIN BEADS INTEGRATION -->
+## Issue Tracking with bd (beads)
+
+**IMPORTANT**: This project uses **bd (beads)** for ALL issue tracking. Do NOT use markdown TODOs, task lists, or other tracking methods.
+
+### Why bd?
+
+- Dependency-aware: Track blockers and relationships between issues
+- Git-friendly: Auto-syncs to JSONL for version control
+- Agent-optimized: JSON output, ready work detection, discovered-from links
+- Prevents duplicate tracking systems and confusion
+
+### Quick Start
+
+**Check for ready work:**
+
+```bash
+bd ready --json
+```
+
+**Create new issues:**
+
+```bash
+bd create "Issue title" --description="Detailed context" -t bug|feature|task -p 0-4 --json
+bd create "Issue title" --description="What this issue is about" -p 1 --deps discovered-from:bd-123 --json
+```
+
+**Claim and update:**
+
+```bash
+bd update <id> --claim --json
+bd update bd-42 --priority 1 --json
+```
+
+**Complete work:**
+
+```bash
+bd close bd-42 --reason "Completed" --json
+```
+
+### Issue Types
+
+- `bug` - Something broken
+- `feature` - New functionality
+- `task` - Work item (tests, docs, refactoring)
+- `epic` - Large feature with subtasks
+- `chore` - Maintenance (dependencies, tooling)
+
+### Priorities
+
+- `0` - Critical (security, data loss, broken builds)
+- `1` - High (major features, important bugs)
+- `2` - Medium (default, nice-to-have)
+- `3` - Low (polish, optimization)
+- `4` - Backlog (future ideas)
+
+### Workflow for AI Agents
+
+1. **Check ready work**: `bd ready` shows unblocked issues
+2. **Claim your task atomically**: `bd update <id> --claim`
+3. **Work on it**: Implement, test, document
+4. **Discover new work?** Create linked issue:
+   - `bd create "Found bug" --description="Details about what was found" -p 1 --deps discovered-from:<parent-id>`
+5. **Complete**: `bd close <id> --reason "Done"`
+
+### Auto-Sync
+
+bd automatically syncs with git:
+
+- Exports to `.beads/issues.jsonl` after changes (5s debounce)
+- Imports from JSONL when newer (e.g., after `git pull`)
+- No manual export/import needed!
+
+### Important Rules
+
+- ✅ Use bd for ALL task tracking
+- ✅ Always use `--json` flag for programmatic use
+- ✅ Link discovered work with `discovered-from` dependencies
+- ✅ Check `bd ready` before asking "what should I work on?"
+- ❌ Do NOT create markdown TODO lists
+- ❌ Do NOT use external issue trackers
+- ❌ Do NOT duplicate tracking systems
+
+For more details, see README.md and docs/QUICKSTART.md.
+
+<!-- END BEADS INTEGRATION -->
+
+## Landing the Plane (Session Completion)
+
+**When ending a work session**, you MUST complete ALL steps below. Work is NOT complete until `git push` succeeds.
+
+**MANDATORY WORKFLOW:**
+
+1. **File issues for remaining work** - Create issues for anything that needs follow-up
+2. **Run quality gates** (if code changed) - Tests, linters, builds
+3. **Update issue status** - Close finished work, update in-progress items
+4. **PUSH TO REMOTE** - This is MANDATORY:
+   ```bash
+   git pull --rebase
+   bd sync
+   git push
+   git status  # MUST show "up to date with origin"
+   ```
+5. **Clean up** - Clear stashes, prune remote branches
+6. **Verify** - All changes committed AND pushed
+7. **Hand off** - Provide context for next session
+
+**CRITICAL RULES:**
+- Work is NOT complete until `git push` succeeds
+- NEVER stop before pushing - that leaves work stranded locally
+- NEVER say "ready to push when you are" - YOU must push
+- If push fails, resolve and retry until it succeeds
--- a/lib/controller/bluetooth.dart
+++ b/lib/controller/bluetooth.dart
@ -299,11 +299,20 @@ class BluetoothController {

  Future<Result<void>> requestMtu(String deviceId,
      {int mtu = defaultMtu}) async {
+    final result = await requestMtuAndGetValue(deviceId, mtu: mtu);
+    if (result.isErr()) {
+      return bail(result.unwrapErr());
+    }
+    return Ok(null);
+  }
+
+  Future<Result<int>> requestMtuAndGetValue(String deviceId,
+      {int mtu = defaultMtu}) async {
    try {
      final negotiatedMtu = await _ble.requestMtu(deviceId: deviceId, mtu: mtu);
      log.info(
          'MTU negotiated for $deviceId: requested $mtu, got $negotiatedMtu');
-      return Ok(null);
+      return Ok(negotiatedMtu);
    } catch (e) {
      return bail('Error requesting MTU $mtu for $deviceId: $e');
    }
--- a/lib/model/firmware_file_selection.dart
+++ b/lib/model/firmware_file_selection.dart
@ -0,0 +1,70 @@
+import 'dart:typed_data';
+
+class DfuV1FirmwareMetadata {
+  const DfuV1FirmwareMetadata({
+    required this.totalLength,
+    required this.crc32,
+    required this.sessionId,
+    required this.flags,
+  });
+
+  final int totalLength;
+  final int crc32;
+  final int sessionId;
+  final int flags;
+}
+
+class DfuV1PreparedFirmware {
+  const DfuV1PreparedFirmware({
+    required this.fileName,
+    required this.fileBytes,
+    required this.metadata,
+    this.filePath,
+  });
+
+  final String fileName;
+  final String? filePath;
+  final Uint8List fileBytes;
+  final DfuV1FirmwareMetadata metadata;
+}
+
+enum FirmwareSelectionFailureReason {
+  canceled,
+  malformedSelection,
+  unsupportedExtension,
+  emptyFile,
+  readFailed,
+}
+
+class FirmwareSelectionFailure {
+  const FirmwareSelectionFailure({
+    required this.reason,
+    required this.message,
+  });
+
+  final FirmwareSelectionFailureReason reason;
+  final String message;
+}
+
+class FirmwareFileSelectionResult {
+  const FirmwareFileSelectionResult._({
+    this.firmware,
+    this.failure,
+  });
+
+  final DfuV1PreparedFirmware? firmware;
+  final FirmwareSelectionFailure? failure;
+
+  bool get isSuccess => firmware != null;
+
+  bool get isCanceled =>
+      failure?.reason == FirmwareSelectionFailureReason.canceled;
+
+  static FirmwareFileSelectionResult success(DfuV1PreparedFirmware firmware) {
+    return FirmwareFileSelectionResult._(firmware: firmware);
+  }
+
+  static FirmwareFileSelectionResult failed(FirmwareSelectionFailure failure) {
+    return FirmwareFileSelectionResult._(failure: failure);
+  }
+}
--- a/lib/model/shifter_types.dart
+++ b/lib/model/shifter_types.dart
@ -10,14 +10,163 @@ const String universalShifterCommandCharacteristicUuid =
    '0993826f-0ee4-4b37-9614-d13ecba40005';
 const String universalShifterGearRatiosCharacteristicUuid =
    '0993826f-0ee4-4b37-9614-d13ecba40006';
+const String universalShifterDfuControlCharacteristicUuid =
+    '0993826f-0ee4-4b37-9614-d13ecba40008';
+const String universalShifterDfuDataCharacteristicUuid =
+    '0993826f-0ee4-4b37-9614-d13ecba40009';
+const String universalShifterDfuAckCharacteristicUuid =
+    '0993826f-0ee4-4b37-9614-d13ecba4000a';
 const String ftmsServiceUuid = '00001826-0000-1000-8000-00805f9b34fb';

+const int universalShifterDfuOpcodeStart = 0x01;
+const int universalShifterDfuOpcodeFinish = 0x02;
+const int universalShifterDfuOpcodeAbort = 0x03;
+
+const int universalShifterDfuFrameSizeBytes = 64;
+const int universalShifterDfuFramePayloadSizeBytes = 63;
+const int universalShifterAttWriteOverheadBytes = 3;
+const int universalShifterDfuMinimumMtu =
+    universalShifterDfuFrameSizeBytes + universalShifterAttWriteOverheadBytes;
+const int universalShifterDfuPreferredMtu = 128;
+
+const int universalShifterDfuFlagEncrypted = 0x01;
+const int universalShifterDfuFlagSigned = 0x02;
+const int universalShifterDfuFlagNone = 0x00;
+
 const int errorSequence = 1;
 const int errorFtmsMissing = 2;
 const int errorPairingAuth = 3;
 const int errorPairingEncrypt = 4;
 const int errorFtmsRequiredCharMissing = 5;

+enum DfuUpdateState {
+  idle,
+  starting,
+  waitingForAck,
+  transferring,
+  finishing,
+  completed,
+  aborted,
+  failed,
+}
+
+class DfuUpdateFlags {
+  const DfuUpdateFlags({
+    this.encrypted = false,
+    this.signed = false,
+  });
+
+  final bool encrypted;
+  final bool signed;
+
+  int get rawValue {
+    var value = 0;
+    if (encrypted) {
+      value |= universalShifterDfuFlagEncrypted;
+    }
+    if (signed) {
+      value |= universalShifterDfuFlagSigned;
+    }
+    return value;
+  }
+
+  static DfuUpdateFlags fromRaw(int rawValue) {
+    return DfuUpdateFlags(
+      encrypted: (rawValue & universalShifterDfuFlagEncrypted) != 0,
+      signed: (rawValue & universalShifterDfuFlagSigned) != 0,
+    );
+  }
+}
+
+class DfuUpdateProgress {
+  const DfuUpdateProgress({
+    required this.state,
+    required this.totalBytes,
+    required this.sentBytes,
+    required this.lastAckedSequence,
+    required this.sessionId,
+    required this.flags,
+    this.errorMessage,
+  });
+
+  final DfuUpdateState state;
+  final int totalBytes;
+  final int sentBytes;
+  final int lastAckedSequence;
+  final int sessionId;
+  final DfuUpdateFlags flags;
+  final String? errorMessage;
+
+  double get fractionComplete {
+    if (totalBytes <= 0) {
+      return 0;
+    }
+    return sentBytes.clamp(0, totalBytes) / totalBytes;
+  }
+
+  int get percentComplete => (fractionComplete * 100).round();
+
+  bool get isTerminal =>
+      state == DfuUpdateState.completed ||
+      state == DfuUpdateState.aborted ||
+      state == DfuUpdateState.failed;
+}
+
+enum DfuPreflightFailureReason {
+  deviceNotConnected,
+  wrongConnectedDevice,
+  mtuRequestFailed,
+  mtuTooLow,
+}
+
+class DfuPreflightResult {
+  const DfuPreflightResult._({
+    required this.requestedMtu,
+    required this.requiredMtu,
+    required this.negotiatedMtu,
+    required this.failureReason,
+    required this.message,
+  });
+
+  final int requestedMtu;
+  final int requiredMtu;
+  final int? negotiatedMtu;
+  final DfuPreflightFailureReason? failureReason;
+  final String? message;
+
+  bool get canStart => failureReason == null;
+
+  static DfuPreflightResult ready({
+    required int requestedMtu,
+    required int negotiatedMtu,
+    int requiredMtu = universalShifterDfuMinimumMtu,
+  }) {
+    return DfuPreflightResult._(
+      requestedMtu: requestedMtu,
+      requiredMtu: requiredMtu,
+      negotiatedMtu: negotiatedMtu,
+      failureReason: null,
+      message: null,
+    );
+  }
+
+  static DfuPreflightResult failed({
+    required int requestedMtu,
+    required DfuPreflightFailureReason failureReason,
+    required String message,
+    int requiredMtu = universalShifterDfuMinimumMtu,
+    int? negotiatedMtu,
+  }) {
+    return DfuPreflightResult._(
+      requestedMtu: requestedMtu,
+      requiredMtu: requiredMtu,
+      negotiatedMtu: negotiatedMtu,
+      failureReason: failureReason,
+      message: message,
+    );
+  }
+}
+
 class ShifterErrorInfo {
  const ShifterErrorInfo({
    required this.code,
@ -112,6 +261,7 @@ enum TrainerConnectionState {
  idle,
  connecting,
  pairing,
+  connected,
  discoveringFtms,
  ftmsReady,
  error,
@ -131,6 +281,8 @@ class TrainerStatus {
        return 'Connecting';
      case TrainerConnectionState.pairing:
        return 'Pairing';
+      case TrainerConnectionState.connected:
+        return 'Connected';
      case TrainerConnectionState.discoveringFtms:
        return 'Discovering FTMS';
      case TrainerConnectionState.ftmsReady:
@ -148,9 +300,11 @@ class TrainerStatus {
        case 2:
          return const TrainerStatus(state: TrainerConnectionState.pairing);
        case 3:
+          return const TrainerStatus(state: TrainerConnectionState.connected);
+        case 4:
          return const TrainerStatus(
              state: TrainerConnectionState.discoveringFtms);
-        case 4:
+        case 5:
          return const TrainerStatus(state: TrainerConnectionState.ftmsReady);
        default:
          return const TrainerStatus(state: TrainerConnectionState.idle);
@ -160,7 +314,7 @@ class TrainerStatus {
    if (raw is List && raw.isNotEmpty) {
      final variant = raw.first;
      final value = raw.length > 1 ? raw[1] : null;
-      if (variant is int && variant == 5) {
+      if (variant is int && (variant == 5 || variant == 6)) {
        return TrainerStatus(
          state: TrainerConnectionState.error,
          errorCode: value is int ? value : null,
@ -173,7 +327,7 @@ class TrainerStatus {
      if (entry != null) {
        final key = entry.key;
        final value = entry.value;
-        if ((key is int && key == 5) ||
+        if ((key is int && (key == 5 || key == 6)) ||
            (key is String && key.toLowerCase().contains('error'))) {
          return TrainerStatus(
            state: TrainerConnectionState.error,
@ -191,6 +345,9 @@ class TrainerStatus {
      if (normalized.contains('pairing')) {
        return const TrainerStatus(state: TrainerConnectionState.pairing);
      }
+      if (normalized.contains('connected')) {
+        return const TrainerStatus(state: TrainerConnectionState.connected);
+      }
      if (normalized.contains('discover')) {
        return const TrainerStatus(
            state: TrainerConnectionState.discoveringFtms);
--- a/lib/pages/device_details_page.dart
+++ b/lib/pages/device_details_page.dart
@ -1,6 +1,9 @@
 import 'dart:async';

+import 'package:abawo_bt_app/model/firmware_file_selection.dart';
 import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/firmware_file_selection_service.dart';
+import 'package:abawo_bt_app/service/firmware_update_service.dart';
 import 'package:abawo_bt_app/service/shifter_service.dart';
 import 'package:abawo_bt_app/widgets/bike_scan_dialog.dart';
 import 'package:abawo_bt_app/widgets/gear_ratio_editor_card.dart';
@ -62,10 +65,48 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
  bool _hasLoadedGearRatios = false;
  String? _gearRatiosError;
  List<double> _gearRatios = const [];
+  int _defaultGearIndex = 0;
+
+  late final FirmwareFileSelectionService _firmwareFileSelectionService;
+  FirmwareUpdateService? _firmwareUpdateService;
+  StreamSubscription<DfuUpdateProgress>? _firmwareProgressSubscription;
+  DfuV1PreparedFirmware? _selectedFirmware;
+  DfuUpdateProgress _dfuProgress = const DfuUpdateProgress(
+    state: DfuUpdateState.idle,
+    totalBytes: 0,
+    sentBytes: 0,
+    lastAckedSequence: 0xFF,
+    sessionId: 0,
+    flags: DfuUpdateFlags(),
+  );
+  bool _isSelectingFirmware = false;
+  bool _isStartingFirmwareUpdate = false;
+  String? _firmwareUserMessage;
+
+  bool get _isFirmwareUpdateBusy {
+    if (_isStartingFirmwareUpdate) {
+      return true;
+    }
+    switch (_dfuProgress.state) {
+      case DfuUpdateState.starting:
+      case DfuUpdateState.waitingForAck:
+      case DfuUpdateState.transferring:
+      case DfuUpdateState.finishing:
+        return true;
+      case DfuUpdateState.idle:
+      case DfuUpdateState.completed:
+      case DfuUpdateState.aborted:
+      case DfuUpdateState.failed:
+        return false;
+    }
+  }

  @override
  void initState() {
    super.initState();
+    _firmwareFileSelectionService = FirmwareFileSelectionService(
+      filePicker: LocalFirmwareFilePicker(),
+    );
    _connectionStatusSubscription =
        ref.listenManual<AsyncValue<(ConnectionStatus, String?)>>(
      connectionStatusProvider,
@ -87,6 +128,8 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
    _connectionStatusSubscription?.close();
    _statusSubscription?.cancel();
    _shifterService?.dispose();
+    _firmwareProgressSubscription?.cancel();
+    unawaited(_firmwareUpdateService?.dispose() ?? Future<void>.value());
    super.dispose();
  }

@ -99,6 +142,9 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
    _isExitingPage = true;
    _reconnectTimeoutTimer?.cancel();

+    await _firmwareUpdateService?.cancelUpdate();
+    await _disposeFirmwareUpdateService();
+
    final bluetooth = ref.read(bluetoothProvider).value;
    await bluetooth?.disconnect();
    await _stopStatusStreaming();
@ -126,11 +172,13 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {

    if (_wasConnectedToCurrentDevice &&
        !_isReconnecting &&
-        status == ConnectionStatus.disconnected) {
+        status == ConnectionStatus.disconnected &&
+        !_isFirmwareUpdateBusy) {
      _startReconnect();
    }

-    if (!isCurrentDevice || status == ConnectionStatus.disconnected) {
+    if ((!isCurrentDevice || status == ConnectionStatus.disconnected) &&
+        !_isFirmwareUpdateBusy) {
      _stopStatusStreaming();
    }
  }
@ -160,6 +208,13 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {

  Future<void> _startStatusStreamingIfNeeded() async {
    if (_shifterService != null) {
+      _statusSubscription ??= _shifterService!.statusStream.listen((status) {
+        if (!mounted) {
+          return;
+        }
+        _recordStatus(status);
+      });
+      _shifterService!.startStatusNotifications();
      if (!_hasLoadedGearRatios && !_isGearRatiosLoading) {
        unawaited(_loadGearRatios());
      }
@ -215,13 +270,26 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
  Future<void> _stopStatusStreaming() async {
    await _statusSubscription?.cancel();
    _statusSubscription = null;
+
+    if (_isFirmwareUpdateBusy) {
+      return;
+    }
+
+    await _disposeFirmwareUpdateService();
    await _shifterService?.dispose();
    _shifterService = null;
  }

+  Future<void> _disposeFirmwareUpdateService() async {
+    await _firmwareProgressSubscription?.cancel();
+    _firmwareProgressSubscription = null;
+    await _firmwareUpdateService?.dispose();
+    _firmwareUpdateService = null;
+  }
+
  Future<void> _loadGearRatios() async {
    final shifter = _shifterService;
-    if (shifter == null || _isGearRatiosLoading) {
+    if (shifter == null || _isGearRatiosLoading || _isFirmwareUpdateBusy) {
      return;
    }

@ -245,20 +313,32 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
    }

    setState(() {
-      _gearRatios = result.unwrap();
+      final data = result.unwrap();
+      _gearRatios = data.ratios;
+      _defaultGearIndex = data.defaultGearIndex;
      _isGearRatiosLoading = false;
      _hasLoadedGearRatios = true;
      _gearRatiosError = null;
    });
  }

-  Future<String?> _saveGearRatios(List<double> ratios) async {
+  Future<String?> _saveGearRatios(
+      List<double> ratios, int defaultGearIndex) async {
+    if (_isFirmwareUpdateBusy) {
+      return 'Gear ratio changes are disabled during firmware update.';
+    }
+
    final shifter = _shifterService;
    if (shifter == null) {
      return 'Status channel is not ready yet.';
    }

-    final result = await shifter.writeGearRatios(ratios);
+    final result = await shifter.writeGearRatios(
+      GearRatiosData(
+        ratios: ratios,
+        defaultGearIndex: defaultGearIndex,
+      ),
+    );
    if (result.isErr()) {
      return 'Could not save gear ratios: ${result.unwrapErr()}';
    }
@ -269,6 +349,9 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {

    setState(() {
      _gearRatios = List<double>.from(ratios);
+      _defaultGearIndex = ratios.isEmpty
+          ? 0
+          : defaultGearIndex.clamp(0, ratios.length - 1).toInt();
      _hasLoadedGearRatios = true;
      _gearRatiosError = null;
    });
@ -277,6 +360,15 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
  }

  Future<void> _connectButtonToBike() async {
+    if (_isFirmwareUpdateBusy) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(
+          content: Text('Connect to bike is disabled during firmware updates.'),
+        ),
+      );
+      return;
+    }
+
    final selectedBike = await BikeScanDialog.show(
      context,
      excludedDeviceId: widget.deviceAddress,
@ -316,6 +408,177 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
    );
  }

+  Future<FirmwareUpdateService?> _ensureFirmwareUpdateService() async {
+    final shifter = _shifterService;
+    if (shifter == null) {
+      return null;
+    }
+    if (_firmwareUpdateService != null) {
+      return _firmwareUpdateService;
+    }
+
+    final asyncBluetooth = ref.read(bluetoothProvider);
+    final bluetooth = asyncBluetooth.valueOrNull;
+    if (bluetooth == null) {
+      return null;
+    }
+
+    final service = FirmwareUpdateService(
+      transport: ShifterFirmwareUpdateTransport(
+        shifterService: shifter,
+        bluetoothController: bluetooth,
+        buttonDeviceId: widget.deviceAddress,
+      ),
+    );
+
+    _firmwareProgressSubscription = service.progressStream.listen((progress) {
+      if (!mounted) {
+        return;
+      }
+      setState(() {
+        _dfuProgress = progress;
+        if (progress.state == DfuUpdateState.failed &&
+            progress.errorMessage != null) {
+          _firmwareUserMessage = progress.errorMessage;
+        }
+        if (progress.state == DfuUpdateState.completed) {
+          _firmwareUserMessage =
+              'Firmware update completed. The button rebooted and reconnected.';
+        }
+        if (progress.state == DfuUpdateState.aborted) {
+          _firmwareUserMessage = 'Firmware update canceled.';
+        }
+      });
+    });
+
+    _firmwareUpdateService = service;
+    return service;
+  }
+
+  Future<void> _selectFirmwareFile() async {
+    if (_isFirmwareUpdateBusy || _isSelectingFirmware) {
+      return;
+    }
+
+    setState(() {
+      _isSelectingFirmware = true;
+      _firmwareUserMessage = null;
+    });
+
+    final result = await _firmwareFileSelectionService.selectAndPrepareDfuV1();
+    if (!mounted) {
+      return;
+    }
+
+    setState(() {
+      _isSelectingFirmware = false;
+      if (result.isSuccess) {
+        _selectedFirmware = result.firmware;
+        _firmwareUserMessage =
+            'Selected ${result.firmware!.fileName}. Ready to start update.';
+      } else if (!result.isCanceled) {
+        _firmwareUserMessage = result.failure?.message;
+      }
+    });
+  }
+
+  Future<void> _startFirmwareUpdate() async {
+    if (_isFirmwareUpdateBusy || _isSelectingFirmware) {
+      return;
+    }
+
+    final firmware = _selectedFirmware;
+    if (firmware == null) {
+      setState(() {
+        _firmwareUserMessage =
+            'Select a firmware .bin file before starting the update.';
+      });
+      return;
+    }
+
+    await _startStatusStreamingIfNeeded();
+    final updater = await _ensureFirmwareUpdateService();
+    if (!mounted) {
+      return;
+    }
+    if (updater == null) {
+      setState(() {
+        _firmwareUserMessage =
+            'Firmware updater is not ready. Ensure the button is connected.';
+      });
+      return;
+    }
+
+    setState(() {
+      _isStartingFirmwareUpdate = true;
+      _firmwareUserMessage =
+          'Starting update. Keep this screen open and stay near the button.';
+    });
+
+    final result = await updater.startUpdate(
+      imageBytes: firmware.fileBytes,
+      sessionId: firmware.metadata.sessionId,
+      flags: DfuUpdateFlags.fromRaw(firmware.metadata.flags),
+    );
+
+    if (!mounted) {
+      return;
+    }
+
+    setState(() {
+      _isStartingFirmwareUpdate = false;
+      if (result.isErr()) {
+        _firmwareUserMessage = result.unwrapErr().toString();
+      }
+    });
+  }
+
+  Future<void> _cancelFirmwareUpdate() async {
+    final updater = _firmwareUpdateService;
+    if (updater == null || !_isFirmwareUpdateBusy) {
+      return;
+    }
+    setState(() {
+      _firmwareUserMessage = 'Canceling firmware update...';
+    });
+    await updater.cancelUpdate();
+  }
+
+  String _dfuPhaseText(DfuUpdateState state) {
+    switch (state) {
+      case DfuUpdateState.idle:
+        return 'Idle';
+      case DfuUpdateState.starting:
+        return 'Sending START command';
+      case DfuUpdateState.waitingForAck:
+        return 'Waiting for ACK from button';
+      case DfuUpdateState.transferring:
+        return 'Transferring firmware frames';
+      case DfuUpdateState.finishing:
+        return 'Finalizing update and waiting for reboot/reconnect';
+      case DfuUpdateState.completed:
+        return 'Update completed';
+      case DfuUpdateState.aborted:
+        return 'Update canceled';
+      case DfuUpdateState.failed:
+        return 'Update failed';
+    }
+  }
+
+  String _formatBytes(int bytes) {
+    if (bytes < 1024) {
+      return '$bytes B';
+    }
+    if (bytes < 1024 * 1024) {
+      return '${(bytes / 1024).toStringAsFixed(1)} KB';
+    }
+    return '${(bytes / (1024 * 1024)).toStringAsFixed(2)} MB';
+  }
+
+  String _hexByte(int value) {
+    return '0x${(value & 0xFF).toRadixString(16).padLeft(2, '0').toUpperCase()}';
+  }
+
  Future<void> _terminateConnectionAndGoHome(String toastMessage) async {
    await _disconnectOnClose();

@ -453,6 +716,13 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
    final isCurrentConnected = connectionData != null &&
        connectionData.$1 == ConnectionStatus.connected &&
        connectionData.$2 == widget.deviceAddress;
+    final canSelectFirmware =
+        isCurrentConnected && !_isSelectingFirmware && !_isFirmwareUpdateBusy;
+    final canStartFirmware = isCurrentConnected &&
+        !_isSelectingFirmware &&
+        !_isFirmwareUpdateBusy &&
+        _selectedFirmware != null;
+    final canCancelFirmware = _isFirmwareUpdateBusy;

    return PopScope(
      canPop: false,
@ -493,30 +763,57 @@ class _DeviceDetailsPageState extends ConsumerState<DeviceDetailsPage> {
                            },
                    ),
                    const SizedBox(height: 16),
-                    GearRatioEditorCard(
-                      ratios: _gearRatios,
-                      isLoading: _isGearRatiosLoading,
-                      errorText: _gearRatiosError,
-                      onRetry: _loadGearRatios,
-                      onSave: _saveGearRatios,
-                      presets: const [
-                        GearRatioPreset(
-                          name: 'KeAnt Classic',
-                          description:
-                              '17-step baseline from KeAnt cross app gearing.',
-                          ratios: _keAntRatios,
-                        ),
-                      ],
-                    ),
-                    const SizedBox(height: 16),
                    SizedBox(
                      width: double.infinity,
                      child: FilledButton.icon(
-                        onPressed: _connectButtonToBike,
+                        onPressed:
+                            _isFirmwareUpdateBusy ? null : _connectButtonToBike,
                        icon: const Icon(Icons.link),
                        label: const Text('Connect Button to Bike'),
                      ),
                    ),
+                    const SizedBox(height: 16),
+                    _FirmwareUpdateCard(
+                      selectedFirmware: _selectedFirmware,
+                      progress: _dfuProgress,
+                      isSelecting: _isSelectingFirmware,
+                      isStarting: _isStartingFirmwareUpdate,
+                      canSelect: canSelectFirmware,
+                      canStart: canStartFirmware,
+                      canCancel: canCancelFirmware,
+                      phaseText: _dfuPhaseText(_dfuProgress.state),
+                      statusText: _firmwareUserMessage,
+                      formattedProgressBytes:
+                          '${_formatBytes(_dfuProgress.sentBytes)} / ${_formatBytes(_dfuProgress.totalBytes)}',
+                      onSelectFirmware: _selectFirmwareFile,
+                      onStartUpdate: _startFirmwareUpdate,
+                      onCancelUpdate: _cancelFirmwareUpdate,
+                      ackSequenceHex: _hexByte(_dfuProgress.lastAckedSequence),
+                    ),
+                    const SizedBox(height: 16),
+                    Opacity(
+                      opacity: _isFirmwareUpdateBusy ? 0.6 : 1,
+                      child: AbsorbPointer(
+                        absorbing: _isFirmwareUpdateBusy,
+                        child: GearRatioEditorCard(
+                          ratios: _gearRatios,
+                          defaultGearIndex: _defaultGearIndex,
+                          isLoading: _isGearRatiosLoading,
+                          errorText: _gearRatiosError,
+                          onRetry:
+                              _isFirmwareUpdateBusy ? null : _loadGearRatios,
+                          onSave: _saveGearRatios,
+                          presets: const [
+                            GearRatioPreset(
+                              name: 'KeAnt Classic',
+                              description:
+                                  '17-step baseline from KeAnt cross app gearing.',
+                              ratios: _keAntRatios,
+                            ),
+                          ],
+                        ),
+                      ),
+                    ),
                  ],
                ],
              ),
@ -570,6 +867,159 @@ class _StatusHistoryEntry {
  final CentralStatus status;
 }

+class _FirmwareUpdateCard extends StatelessWidget {
+  const _FirmwareUpdateCard({
+    required this.selectedFirmware,
+    required this.progress,
+    required this.isSelecting,
+    required this.isStarting,
+    required this.canSelect,
+    required this.canStart,
+    required this.canCancel,
+    required this.phaseText,
+    required this.statusText,
+    required this.formattedProgressBytes,
+    required this.ackSequenceHex,
+    required this.onSelectFirmware,
+    required this.onStartUpdate,
+    required this.onCancelUpdate,
+  });
+
+  final DfuV1PreparedFirmware? selectedFirmware;
+  final DfuUpdateProgress progress;
+  final bool isSelecting;
+  final bool isStarting;
+  final bool canSelect;
+  final bool canStart;
+  final bool canCancel;
+  final String phaseText;
+  final String? statusText;
+  final String formattedProgressBytes;
+  final String ackSequenceHex;
+  final Future<void> Function() onSelectFirmware;
+  final Future<void> Function() onStartUpdate;
+  final Future<void> Function() onCancelUpdate;
+
+  bool get _showProgress {
+    return progress.totalBytes > 0 ||
+        progress.sentBytes > 0 ||
+        progress.state != DfuUpdateState.idle;
+  }
+
+  bool get _showRebootExpectation {
+    return progress.state == DfuUpdateState.finishing ||
+        progress.state == DfuUpdateState.completed;
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final colorScheme = theme.colorScheme;
+
+    return Container(
+      decoration: BoxDecoration(
+        borderRadius: BorderRadius.circular(16),
+        color: colorScheme.surfaceContainerHighest.withValues(alpha: 0.55),
+        border: Border.all(
+          color: colorScheme.outlineVariant.withValues(alpha: 0.6),
+        ),
+      ),
+      padding: const EdgeInsets.fromLTRB(14, 12, 14, 14),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          const Text(
+            'Firmware Update',
+            style: TextStyle(fontSize: 17, fontWeight: FontWeight.w700),
+          ),
+          const SizedBox(height: 10),
+          Wrap(
+            spacing: 8,
+            runSpacing: 8,
+            children: [
+              OutlinedButton.icon(
+                onPressed: canSelect ? onSelectFirmware : null,
+                icon: isSelecting
+                    ? const SizedBox(
+                        width: 16,
+                        height: 16,
+                        child: CircularProgressIndicator(strokeWidth: 2),
+                      )
+                    : const Icon(Icons.upload_file),
+                label: const Text('Select Firmware'),
+              ),
+              FilledButton.icon(
+                onPressed: canStart ? onStartUpdate : null,
+                icon: isStarting
+                    ? const SizedBox(
+                        width: 16,
+                        height: 16,
+                        child: CircularProgressIndicator(strokeWidth: 2),
+                      )
+                    : const Icon(Icons.system_update_alt),
+                label: const Text('Start Update'),
+              ),
+              TextButton.icon(
+                onPressed: canCancel ? onCancelUpdate : null,
+                icon: const Icon(Icons.stop_circle_outlined),
+                label: const Text('Cancel Update'),
+              ),
+            ],
+          ),
+          const SizedBox(height: 10),
+          Text(
+            selectedFirmware == null
+                ? 'Selected file: none'
+                : 'Selected file: ${selectedFirmware!.fileName}',
+            style: theme.textTheme.bodyMedium,
+          ),
+          if (selectedFirmware != null) ...[
+            const SizedBox(height: 4),
+            Text(
+              'Size: ${selectedFirmware!.fileBytes.length} bytes  |  Session: ${selectedFirmware!.metadata.sessionId}  |  CRC32: 0x${selectedFirmware!.metadata.crc32.toRadixString(16).padLeft(8, '0').toUpperCase()}',
+              style: theme.textTheme.bodySmall,
+            ),
+          ],
+          const SizedBox(height: 10),
+          Text('Phase: $phaseText', style: theme.textTheme.bodyMedium),
+          if (_showProgress) ...[
+            const SizedBox(height: 8),
+            LinearProgressIndicator(
+              value: progress.totalBytes > 0 ? progress.fractionComplete : 0,
+            ),
+            const SizedBox(height: 6),
+            Text(
+              '${progress.percentComplete}%  •  $formattedProgressBytes  •  Last ACK $ackSequenceHex',
+              style: theme.textTheme.bodySmall,
+            ),
+          ],
+          if (_showRebootExpectation) ...[
+            const SizedBox(height: 8),
+            Text(
+              'Expected behavior: the button reboots after FINISH, disconnects briefly, then reconnects.',
+              style: theme.textTheme.bodySmall?.copyWith(
+                color: colorScheme.primary,
+                fontWeight: FontWeight.w600,
+              ),
+            ),
+          ],
+          if (statusText != null && statusText!.trim().isNotEmpty) ...[
+            const SizedBox(height: 8),
+            Text(
+              statusText!,
+              style: theme.textTheme.bodySmall?.copyWith(
+                color: progress.state == DfuUpdateState.failed
+                    ? colorScheme.error
+                    : theme.textTheme.bodySmall?.color,
+              ),
+            ),
+          ],
+        ],
+      ),
+    );
+  }
+}
+
 class _StatusBanner extends StatelessWidget {
  const _StatusBanner({
    required this.status,
--- a/lib/service/dfu_protocol.dart
+++ b/lib/service/dfu_protocol.dart
@ -0,0 +1,137 @@
+import 'dart:typed_data';
+
+import 'package:abawo_bt_app/model/shifter_types.dart';
+
+const int _startPayloadLength = 11;
+
+class DfuStartPayload {
+  const DfuStartPayload({
+    required this.totalLength,
+    required this.imageCrc32,
+    required this.sessionId,
+    required this.flags,
+  });
+
+  final int totalLength;
+  final int imageCrc32;
+  final int sessionId;
+  final int flags;
+}
+
+class DfuDataFrame {
+  const DfuDataFrame({
+    required this.sequence,
+    required this.offset,
+    required this.payloadLength,
+    required this.bytes,
+  });
+
+  final int sequence;
+  final int offset;
+  final int payloadLength;
+  final Uint8List bytes;
+}
+
+class DfuProtocol {
+  const DfuProtocol._();
+
+  static Uint8List encodeStartPayload(DfuStartPayload payload) {
+    final data = ByteData(_startPayloadLength);
+    data.setUint8(0, universalShifterDfuOpcodeStart);
+    data.setUint32(1, payload.totalLength, Endian.little);
+    data.setUint32(5, payload.imageCrc32, Endian.little);
+    data.setUint8(9, payload.sessionId);
+    data.setUint8(10, payload.flags);
+    return data.buffer.asUint8List();
+  }
+
+  static Uint8List encodeFinishPayload() {
+    return Uint8List.fromList([universalShifterDfuOpcodeFinish]);
+  }
+
+  static Uint8List encodeAbortPayload() {
+    return Uint8List.fromList([universalShifterDfuOpcodeAbort]);
+  }
+
+  static List<DfuDataFrame> buildDataFrames(
+    List<int> imageBytes, {
+    int startSequence = 0,
+  }) {
+    final frames = <DfuDataFrame>[];
+    var seq = _asU8(startSequence);
+    var offset = 0;
+    while (offset < imageBytes.length) {
+      final remaining = imageBytes.length - offset;
+      final chunkLength = remaining < universalShifterDfuFramePayloadSizeBytes
+          ? remaining
+          : universalShifterDfuFramePayloadSizeBytes;
+
+      final frame = Uint8List(universalShifterDfuFrameSizeBytes);
+      frame[0] = seq;
+      frame.setRange(1, 1 + chunkLength, imageBytes, offset);
+
+      frames.add(
+        DfuDataFrame(
+          sequence: seq,
+          offset: offset,
+          payloadLength: chunkLength,
+          bytes: frame,
+        ),
+      );
+
+      offset += chunkLength;
+      seq = nextSequence(seq);
+    }
+
+    return frames;
+  }
+
+  static int nextSequence(int sequence) {
+    return _asU8(sequence + 1);
+  }
+
+  static int rewindSequenceFromAck(int acknowledgedSequence) {
+    return nextSequence(acknowledgedSequence);
+  }
+
+  static int sequenceDistance(int from, int to) {
+    return _asU8(to - from);
+  }
+
+  static int parseAckPayload(List<int> payload) {
+    if (payload.length != 1) {
+      throw const FormatException('ACK payload must be exactly 1 byte.');
+    }
+    return _asU8(payload.first);
+  }
+
+  static const int crc32Initial = 0xFFFFFFFF;
+  static const int _crc32PolynomialReflected = 0xEDB88320;
+
+  static int crc32Update(int crc, List<int> bytes) {
+    var next = crc & 0xFFFFFFFF;
+    for (final byte in bytes) {
+      next ^= byte;
+      for (var bit = 0; bit < 8; bit++) {
+        if ((next & 0x1) != 0) {
+          next = (next >> 1) ^ _crc32PolynomialReflected;
+        } else {
+          next >>= 1;
+        }
+      }
+    }
+    return next & 0xFFFFFFFF;
+  }
+
+  static int crc32Finalize(int crc) {
+    return (crc ^ 0xFFFFFFFF) & 0xFFFFFFFF;
+  }
+
+  static int crc32(List<int> bytes) {
+    return crc32Finalize(crc32Update(crc32Initial, bytes));
+  }
+
+  static int _asU8(int value) {
+    return value & 0xFF;
+  }
+}
--- a/lib/service/firmware_file_selection_service.dart
+++ b/lib/service/firmware_file_selection_service.dart
@ -0,0 +1,154 @@
+import 'dart:io';
+import 'dart:math';
+import 'dart:typed_data';
+
+import 'package:abawo_bt_app/model/firmware_file_selection.dart';
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/dfu_protocol.dart';
+import 'package:file_picker/file_picker.dart';
+
+typedef SessionIdGenerator = int Function();
+
+class FirmwarePickerSelection {
+  const FirmwarePickerSelection({
+    required this.fileName,
+    required this.fileBytes,
+    this.filePath,
+  });
+
+  final String fileName;
+  final Uint8List fileBytes;
+  final String? filePath;
+}
+
+abstract interface class FirmwareFilePicker {
+  Future<FirmwarePickerSelection?> pickFirmwareFile();
+}
+
+class LocalFirmwareFilePicker implements FirmwareFilePicker {
+  @override
+  Future<FirmwarePickerSelection?> pickFirmwareFile() async {
+    final pickResult = await FilePicker.platform.pickFiles(
+      allowMultiple: false,
+      withData: true,
+      type: FileType.custom,
+      allowedExtensions: const ['bin'],
+    );
+    if (pickResult == null) {
+      return null;
+    }
+    if (pickResult.files.isEmpty) {
+      return FirmwarePickerSelection(
+        fileName: '',
+        fileBytes: Uint8List(0),
+      );
+    }
+
+    final selected = pickResult.files.first;
+    final bytes = selected.bytes ?? await _readFromPath(selected.path);
+
+    return FirmwarePickerSelection(
+      fileName: selected.name,
+      filePath: selected.path,
+      fileBytes: bytes,
+    );
+  }
+
+  Future<Uint8List> _readFromPath(String? path) async {
+    if (path == null || path.trim().isEmpty) {
+      throw const FileSystemException(
+        'Selected file did not contain readable bytes or a valid path.',
+      );
+    }
+    final file = File(path);
+    return file.readAsBytes();
+  }
+}
+
+class FirmwareFileSelectionService {
+  FirmwareFileSelectionService({
+    required FirmwareFilePicker filePicker,
+    SessionIdGenerator? sessionIdGenerator,
+  })  : _filePicker = filePicker,
+        _sessionIdGenerator = sessionIdGenerator ?? _randomSessionId;
+
+  final FirmwareFilePicker _filePicker;
+  final SessionIdGenerator _sessionIdGenerator;
+
+  Future<FirmwareFileSelectionResult> selectAndPrepareDfuV1() async {
+    final FirmwarePickerSelection? selection;
+    try {
+      selection = await _filePicker.pickFirmwareFile();
+    } catch (error) {
+      return FirmwareFileSelectionResult.failed(
+        FirmwareSelectionFailure(
+          reason: FirmwareSelectionFailureReason.readFailed,
+          message: 'Could not read selected firmware file: $error',
+        ),
+      );
+    }
+
+    if (selection == null) {
+      return FirmwareFileSelectionResult.failed(
+        const FirmwareSelectionFailure(
+          reason: FirmwareSelectionFailureReason.canceled,
+          message: 'Firmware selection canceled.',
+        ),
+      );
+    }
+
+    final fileName = selection.fileName.trim();
+    if (fileName.isEmpty) {
+      return FirmwareFileSelectionResult.failed(
+        const FirmwareSelectionFailure(
+          reason: FirmwareSelectionFailureReason.malformedSelection,
+          message: 'Selected firmware file is missing a valid name.',
+        ),
+      );
+    }
+
+    if (!_hasBinExtension(fileName)) {
+      return FirmwareFileSelectionResult.failed(
+        FirmwareSelectionFailure(
+          reason: FirmwareSelectionFailureReason.unsupportedExtension,
+          message:
+              'Unsupported firmware file "$fileName". Please select a .bin file.',
+        ),
+      );
+    }
+
+    if (selection.fileBytes.isEmpty) {
+      return FirmwareFileSelectionResult.failed(
+        FirmwareSelectionFailure(
+          reason: FirmwareSelectionFailureReason.emptyFile,
+          message:
+              'Selected firmware file "$fileName" is empty. Choose a non-empty .bin file.',
+        ),
+      );
+    }
+
+    final metadata = DfuV1FirmwareMetadata(
+      totalLength: selection.fileBytes.length,
+      crc32: DfuProtocol.crc32(selection.fileBytes),
+      sessionId: _sessionIdGenerator() & 0xFF,
+      flags: universalShifterDfuFlagNone,
+    );
+
+    return FirmwareFileSelectionResult.success(
+      DfuV1PreparedFirmware(
+        fileName: fileName,
+        filePath: selection.filePath,
+        fileBytes: selection.fileBytes,
+        metadata: metadata,
+      ),
+    );
+  }
+
+  bool _hasBinExtension(String fileName) {
+    return fileName.toLowerCase().endsWith('.bin');
+  }
+
+  static int _randomSessionId() {
+    return Random.secure().nextInt(256);
+  }
+}
--- a/lib/service/firmware_update_service.dart
+++ b/lib/service/firmware_update_service.dart
@ -0,0 +1,690 @@
+import 'dart:async';
+
+import 'package:abawo_bt_app/controller/bluetooth.dart';
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/dfu_protocol.dart';
+import 'package:abawo_bt_app/service/shifter_service.dart';
+import 'package:anyhow/anyhow.dart';
+
+const int _initialAckSequence = 0xFF;
+
+class FirmwareUpdateService {
+  FirmwareUpdateService({
+    required FirmwareUpdateTransport transport,
+    this.defaultWindowSize = 8,
+    this.maxNoProgressRetries = 5,
+    this.defaultAckTimeout = const Duration(milliseconds: 800),
+    this.defaultPostFinishResetTimeout = const Duration(seconds: 8),
+    this.defaultReconnectTimeout = const Duration(seconds: 12),
+    this.defaultVerificationTimeout = const Duration(seconds: 5),
+  }) : _transport = transport;
+
+  final FirmwareUpdateTransport _transport;
+  final int defaultWindowSize;
+  final int maxNoProgressRetries;
+  final Duration defaultAckTimeout;
+  final Duration defaultPostFinishResetTimeout;
+  final Duration defaultReconnectTimeout;
+  final Duration defaultVerificationTimeout;
+
+  final StreamController<DfuUpdateProgress> _progressController =
+      StreamController<DfuUpdateProgress>.broadcast();
+
+  DfuUpdateProgress _currentProgress = const DfuUpdateProgress(
+    state: DfuUpdateState.idle,
+    totalBytes: 0,
+    sentBytes: 0,
+    lastAckedSequence: _initialAckSequence,
+    sessionId: 0,
+    flags: DfuUpdateFlags(),
+  );
+
+  StreamSubscription<List<int>>? _ackSubscription;
+  Completer<void>? _ackSignal;
+  Completer<void>? _cancelSignal;
+  int _ackEventCount = 0;
+  String? _ackStreamError;
+  bool _isRunning = false;
+  bool _cancelRequested = false;
+  int _latestAckSequence = _initialAckSequence;
+  int _ackedFrames = 0;
+  int _totalFrames = 0;
+  int _totalBytes = 0;
+
+  Stream<DfuUpdateProgress> get progressStream => _progressController.stream;
+
+  DfuUpdateProgress get currentProgress => _currentProgress;
+
+  bool get isUpdating => _isRunning;
+
+  Future<Result<void>> startUpdate({
+    required List<int> imageBytes,
+    required int sessionId,
+    DfuUpdateFlags flags = const DfuUpdateFlags(),
+    int requestedMtu = universalShifterDfuPreferredMtu,
+    int? windowSize,
+    Duration? ackTimeout,
+    int? noProgressRetries,
+    Duration? postFinishResetTimeout,
+    Duration? reconnectTimeout,
+    Duration? verificationTimeout,
+  }) async {
+    if (_isRunning) {
+      return bail(
+          'Firmware update is already running. Cancel or wait for completion before starting a new upload.');
+    }
+    if (imageBytes.isEmpty) {
+      return bail(
+          'Firmware image is empty. Select a valid .bin file and retry.');
+    }
+
+    final effectiveWindowSize = windowSize ?? defaultWindowSize;
+    final effectiveAckTimeout = ackTimeout ?? defaultAckTimeout;
+    final effectiveNoProgressRetries =
+        noProgressRetries ?? maxNoProgressRetries;
+    final effectivePostFinishResetTimeout =
+        postFinishResetTimeout ?? defaultPostFinishResetTimeout;
+    final effectiveReconnectTimeout =
+        reconnectTimeout ?? defaultReconnectTimeout;
+    final effectiveVerificationTimeout =
+        verificationTimeout ?? defaultVerificationTimeout;
+
+    if (effectiveWindowSize <= 0) {
+      return bail(
+          'DFU window size must be at least 1 frame. Got $effectiveWindowSize.');
+    }
+    if (effectiveNoProgressRetries < 0) {
+      return bail(
+          'No-progress retry limit cannot be negative. Got $effectiveNoProgressRetries.');
+    }
+
+    _isRunning = true;
+    _cancelRequested = false;
+    _cancelSignal = Completer<void>();
+    _ackSignal = null;
+    _ackEventCount = 0;
+    _ackStreamError = null;
+    _latestAckSequence = _initialAckSequence;
+    _ackedFrames = 0;
+    _totalFrames =
+        (imageBytes.length + universalShifterDfuFramePayloadSizeBytes - 1) ~/
+            universalShifterDfuFramePayloadSizeBytes;
+    _totalBytes = imageBytes.length;
+
+    final normalizedSessionId = sessionId & 0xFF;
+    final crc32 = DfuProtocol.crc32(imageBytes);
+    final frames = DfuProtocol.buildDataFrames(imageBytes);
+    var shouldAbortForCleanup = false;
+
+    _emitProgress(
+      state: DfuUpdateState.starting,
+      totalBytes: imageBytes.length,
+      sentBytes: 0,
+      lastAckedSequence: _initialAckSequence,
+      sessionId: normalizedSessionId,
+      flags: flags,
+    );
+
+    try {
+      final preflightResult = await _transport.runPreflight(
+        requestedMtu: requestedMtu,
+      );
+      if (preflightResult.isErr()) {
+        throw _DfuFailure(
+          'DFU preflight check failed due to transport error: ${preflightResult.unwrapErr()}',
+        );
+      }
+      final preflight = preflightResult.unwrap();
+      if (!preflight.canStart) {
+        throw _DfuFailure(
+          preflight.message ??
+              'DFU preflight failed. Ensure button connection and MTU are ready, then retry.',
+        );
+      }
+
+      await _ackSubscription?.cancel();
+      _ackSubscription = _transport.subscribeToAck().listen(
+        _handleAckPayload,
+        onError: (Object error) {
+          _ackStreamError =
+              'ACK indication stream failed: $error. Reconnect and retry the update.';
+          _signalAckWaiters();
+        },
+      );
+
+      _emitProgress(state: DfuUpdateState.waitingForAck);
+      final startEventCount = _ackEventCount;
+      final startWriteResult = await _transport.writeControl(
+        DfuProtocol.encodeStartPayload(
+          DfuStartPayload(
+            totalLength: imageBytes.length,
+            imageCrc32: crc32,
+            sessionId: normalizedSessionId,
+            flags: flags.rawValue,
+          ),
+        ),
+      );
+      if (startWriteResult.isErr()) {
+        throw _DfuFailure(
+          'Failed to send DFU START command: ${startWriteResult.unwrapErr()}',
+        );
+      }
+      shouldAbortForCleanup = true;
+
+      final initialAck = await _waitForInitialAck(
+        afterEventCount: startEventCount,
+        timeout: effectiveAckTimeout,
+      );
+      if (initialAck != _initialAckSequence) {
+        throw _DfuFailure(
+          'Device did not acknowledge START correctly (expected ACK 0xFF, got 0x${initialAck.toRadixString(16).padLeft(2, '0').toUpperCase()}). Send ABORT, reconnect if needed, and retry.',
+        );
+      }
+
+      _emitProgress(state: DfuUpdateState.transferring);
+
+      var nextFrameIndex = 0;
+      var retriesWithoutProgress = 0;
+
+      while (_ackedFrames < _totalFrames) {
+        _throwIfCancelled();
+        _throwIfAckStreamErrored();
+
+        final ackedBeforeWindow = _ackedFrames;
+        final endExclusive =
+            (nextFrameIndex + effectiveWindowSize).clamp(0, frames.length);
+
+        for (var frameIndex = nextFrameIndex;
+            frameIndex < endExclusive;
+            frameIndex++) {
+          _throwIfCancelled();
+          final writeResult =
+              await _transport.writeDataFrame(frames[frameIndex].bytes);
+          if (writeResult.isErr()) {
+            throw _DfuFailure(
+              'Failed sending DFU data frame #$frameIndex (seq 0x${frames[frameIndex].sequence.toRadixString(16).padLeft(2, '0').toUpperCase()}): ${writeResult.unwrapErr()}',
+            );
+          }
+        }
+
+        nextFrameIndex = endExclusive;
+
+        if (_ackedFrames > ackedBeforeWindow) {
+          retriesWithoutProgress = 0;
+          nextFrameIndex = _ackedFrames;
+          continue;
+        }
+
+        final gotProgress = await _waitForAckProgress(
+          ackedFramesBeforeWait: ackedBeforeWindow,
+          timeout: effectiveAckTimeout,
+        );
+
+        if (gotProgress) {
+          retriesWithoutProgress = 0;
+          nextFrameIndex = _ackedFrames;
+          continue;
+        }
+
+        retriesWithoutProgress += 1;
+        if (retriesWithoutProgress > effectiveNoProgressRetries) {
+          throw _DfuFailure(
+            'Upload stalled: no ACK progress after $retriesWithoutProgress retries (last ACK 0x${_latestAckSequence.toRadixString(16).padLeft(2, '0').toUpperCase()}). Check BLE signal quality and retry.',
+          );
+        }
+
+        nextFrameIndex = _ackedFrames;
+      }
+
+      _emitProgress(
+          state: DfuUpdateState.finishing, sentBytes: imageBytes.length);
+      final finishResult =
+          await _transport.writeControl(DfuProtocol.encodeFinishPayload());
+      if (finishResult.isErr()) {
+        throw _DfuFailure(
+          'Failed to send DFU FINISH command: ${finishResult.unwrapErr()}',
+        );
+      }
+
+      await _ackSubscription?.cancel();
+      _ackSubscription = null;
+
+      final resetDisconnectResult =
+          await _transport.waitForExpectedResetDisconnect(
+        timeout: effectivePostFinishResetTimeout,
+      );
+      if (resetDisconnectResult.isErr()) {
+        throw _DfuFailure(
+          'Device did not perform the expected post-FINISH reset disconnect: ${resetDisconnectResult.unwrapErr()}',
+        );
+      }
+
+      final reconnectResult = await _transport.reconnectForVerification(
+        timeout: effectiveReconnectTimeout,
+      );
+      if (reconnectResult.isErr()) {
+        throw _DfuFailure(
+          'Device did not reconnect after DFU reset: ${reconnectResult.unwrapErr()}',
+        );
+      }
+
+      final verificationResult = await _transport.verifyDeviceReachable(
+        timeout: effectiveVerificationTimeout,
+      );
+      if (verificationResult.isErr()) {
+        throw _DfuFailure(
+          'Device reconnected but post-update verification failed: ${verificationResult.unwrapErr()} '
+          'Firmware version cannot be compared yet because the device does not expose a version characteristic.',
+        );
+      }
+
+      shouldAbortForCleanup = false;
+      _emitProgress(
+          state: DfuUpdateState.completed, sentBytes: imageBytes.length);
+      return Ok(null);
+    } on _DfuCancelled {
+      if (shouldAbortForCleanup) {
+        await _sendAbortForCleanup();
+      }
+      _emitProgress(state: DfuUpdateState.aborted);
+      return bail('Firmware update canceled by user.');
+    } on _DfuFailure catch (failure) {
+      if (shouldAbortForCleanup) {
+        await _sendAbortForCleanup();
+      }
+      _emitProgress(
+          state: DfuUpdateState.failed, errorMessage: failure.message);
+      return bail(failure.message);
+    } catch (error) {
+      if (shouldAbortForCleanup) {
+        await _sendAbortForCleanup();
+      }
+      final message =
+          'Firmware update failed unexpectedly: $error. Reconnect to the button and retry.';
+      _emitProgress(state: DfuUpdateState.failed, errorMessage: message);
+      return bail(message);
+    } finally {
+      await _ackSubscription?.cancel();
+      _ackSubscription = null;
+      _isRunning = false;
+      _cancelRequested = false;
+      _cancelSignal = null;
+      _ackSignal = null;
+      _ackEventCount = 0;
+      _ackStreamError = null;
+      _latestAckSequence = _currentProgress.lastAckedSequence;
+      _ackedFrames = 0;
+      _totalFrames = 0;
+      _totalBytes = 0;
+    }
+  }
+
+  Future<void> cancelUpdate() async {
+    if (!_isRunning || _cancelRequested) {
+      return;
+    }
+    _cancelRequested = true;
+    _cancelSignal?.complete();
+    _signalAckWaiters();
+  }
+
+  Future<void> dispose() async {
+    await cancelUpdate();
+    await _ackSubscription?.cancel();
+    _ackSubscription = null;
+    await _progressController.close();
+  }
+
+  void _handleAckPayload(List<int> payload) {
+    try {
+      final sequence = DfuProtocol.parseAckPayload(payload);
+      final previousAck = _latestAckSequence;
+      _latestAckSequence = sequence;
+
+      if (_totalFrames > 0 &&
+          _currentProgress.state == DfuUpdateState.transferring) {
+        final delta = DfuProtocol.sequenceDistance(previousAck, sequence);
+        if (delta > 0) {
+          _ackedFrames = (_ackedFrames + delta).clamp(0, _totalFrames);
+        }
+
+        _emitProgress(
+          lastAckedSequence: sequence,
+          sentBytes:
+              _ackedBytesFromFrames(_ackedFrames, _totalFrames, _totalBytes),
+        );
+      } else {
+        _emitProgress(lastAckedSequence: sequence);
+      }
+    } on FormatException catch (error) {
+      _ackStreamError =
+          'Received malformed ACK indication: $error. Reconnect and retry.';
+    } finally {
+      _ackEventCount += 1;
+      _signalAckWaiters();
+    }
+  }
+
+  void _emitProgress({
+    DfuUpdateState? state,
+    int? totalBytes,
+    int? sentBytes,
+    int? lastAckedSequence,
+    int? sessionId,
+    DfuUpdateFlags? flags,
+    String? errorMessage,
+  }) {
+    final next = DfuUpdateProgress(
+      state: state ?? _currentProgress.state,
+      totalBytes: totalBytes ?? _currentProgress.totalBytes,
+      sentBytes: sentBytes ?? _currentProgress.sentBytes,
+      lastAckedSequence:
+          lastAckedSequence ?? _currentProgress.lastAckedSequence,
+      sessionId: sessionId ?? _currentProgress.sessionId,
+      flags: flags ?? _currentProgress.flags,
+      errorMessage: errorMessage,
+    );
+    _currentProgress = next;
+    _progressController.add(next);
+  }
+
+  Future<int> _waitForInitialAck({
+    required int afterEventCount,
+    required Duration timeout,
+  }) async {
+    final deadline = DateTime.now().add(timeout);
+    var observedEvents = afterEventCount;
+
+    while (true) {
+      _throwIfCancelled();
+      _throwIfAckStreamErrored();
+      final remaining = deadline.difference(DateTime.now());
+      if (remaining <= Duration.zero) {
+        throw _DfuFailure(
+          'Timed out waiting for initial DFU ACK after START. Ensure indications are enabled and retry.',
+        );
+      }
+
+      final gotEvent = await _waitForNextAckEvent(
+        afterEventCount: observedEvents,
+        timeout: remaining,
+      );
+      if (!gotEvent) {
+        continue;
+      }
+      observedEvents = _ackEventCount;
+      return _latestAckSequence;
+    }
+  }
+
+  Future<bool> _waitForAckProgress({
+    required int ackedFramesBeforeWait,
+    required Duration timeout,
+  }) async {
+    final deadline = DateTime.now().add(timeout);
+    var observedEvents = _ackEventCount;
+
+    while (true) {
+      _throwIfCancelled();
+      _throwIfAckStreamErrored();
+
+      if (_ackedFrames > ackedFramesBeforeWait) {
+        return true;
+      }
+
+      final remaining = deadline.difference(DateTime.now());
+      if (remaining <= Duration.zero) {
+        return false;
+      }
+
+      final gotEvent = await _waitForNextAckEvent(
+        afterEventCount: observedEvents,
+        timeout: remaining,
+      );
+
+      if (!gotEvent) {
+        continue;
+      }
+
+      observedEvents = _ackEventCount;
+    }
+  }
+
+  Future<bool> _waitForNextAckEvent({
+    required int afterEventCount,
+    required Duration timeout,
+  }) async {
+    if (_ackEventCount > afterEventCount) {
+      return true;
+    }
+
+    _ackSignal ??= Completer<void>();
+    final signal = _ackSignal!;
+
+    try {
+      await Future.any<void>([
+        signal.future,
+        _cancelSignal?.future ?? Future<void>.value(),
+      ]).timeout(timeout);
+    } on TimeoutException {
+      return false;
+    }
+
+    if (identical(_ackSignal, signal)) {
+      _ackSignal = null;
+    }
+
+    _throwIfCancelled();
+    _throwIfAckStreamErrored();
+    return _ackEventCount > afterEventCount;
+  }
+
+  void _throwIfCancelled() {
+    if (_cancelRequested) {
+      throw const _DfuCancelled();
+    }
+  }
+
+  void _throwIfAckStreamErrored() {
+    final error = _ackStreamError;
+    if (error != null) {
+      throw _DfuFailure(error);
+    }
+  }
+
+  Future<void> _sendAbortForCleanup() async {
+    final result =
+        await _transport.writeControl(DfuProtocol.encodeAbortPayload());
+    if (result.isErr()) {
+      final cleanupMessage =
+          'Could not send DFU ABORT during cleanup: ${result.unwrapErr()}';
+      if (_currentProgress.state == DfuUpdateState.failed &&
+          _currentProgress.errorMessage != null) {
+        _emitProgress(
+          errorMessage: '${_currentProgress.errorMessage} $cleanupMessage',
+        );
+      }
+    }
+  }
+
+  void _signalAckWaiters() {
+    final signal = _ackSignal;
+    if (signal != null && !signal.isCompleted) {
+      signal.complete();
+    }
+  }
+
+  int _ackedBytesFromFrames(int ackedFrames, int totalFrames, int totalBytes) {
+    if (totalFrames == 0 || ackedFrames <= 0) {
+      return 0;
+    }
+    if (ackedFrames >= totalFrames) {
+      return totalBytes;
+    }
+    return ackedFrames * universalShifterDfuFramePayloadSizeBytes;
+  }
+}
+
+abstract interface class FirmwareUpdateTransport {
+  Future<Result<DfuPreflightResult>> runPreflight({required int requestedMtu});
+
+  Stream<List<int>> subscribeToAck();
+
+  Future<Result<void>> writeControl(List<int> payload);
+
+  Future<Result<void>> writeDataFrame(List<int> frame);
+
+  Future<Result<void>> waitForExpectedResetDisconnect({
+    required Duration timeout,
+  });
+
+  Future<Result<void>> reconnectForVerification({
+    required Duration timeout,
+  });
+
+  /// Verifies that the device is reachable after reconnect.
+  ///
+  /// Current limitation: strict firmware version comparison is not possible
+  /// yet because no firmware version characteristic is exposed by the device.
+  Future<Result<void>> verifyDeviceReachable({
+    required Duration timeout,
+  });
+}
+
+class ShifterFirmwareUpdateTransport implements FirmwareUpdateTransport {
+  ShifterFirmwareUpdateTransport({
+    required this.shifterService,
+    required this.bluetoothController,
+    required this.buttonDeviceId,
+  });
+
+  final ShifterService shifterService;
+  final BluetoothController bluetoothController;
+  final String buttonDeviceId;
+
+  @override
+  Future<Result<DfuPreflightResult>> runPreflight({
+    required int requestedMtu,
+  }) {
+    return shifterService.runDfuPreflight(requestedMtu: requestedMtu);
+  }
+
+  @override
+  Stream<List<int>> subscribeToAck() {
+    return bluetoothController.subscribeToCharacteristic(
+      buttonDeviceId,
+      universalShifterControlServiceUuid,
+      universalShifterDfuAckCharacteristicUuid,
+    );
+  }
+
+  @override
+  Future<Result<void>> writeControl(List<int> payload) {
+    return bluetoothController.writeCharacteristic(
+      buttonDeviceId,
+      universalShifterControlServiceUuid,
+      universalShifterDfuControlCharacteristicUuid,
+      payload,
+    );
+  }
+
+  @override
+  Future<Result<void>> writeDataFrame(List<int> frame) {
+    return bluetoothController.writeCharacteristic(
+      buttonDeviceId,
+      universalShifterControlServiceUuid,
+      universalShifterDfuDataCharacteristicUuid,
+      frame,
+      withResponse: false,
+    );
+  }
+
+  @override
+  Future<Result<void>> waitForExpectedResetDisconnect({
+    required Duration timeout,
+  }) async {
+    final currentState = bluetoothController.currentConnectionState;
+    if (currentState.$1 == ConnectionStatus.disconnected) {
+      return Ok(null);
+    }
+
+    try {
+      await bluetoothController.connectionStateStream
+          .firstWhere((state) => state.$1 == ConnectionStatus.disconnected)
+          .timeout(timeout);
+      return Ok(null);
+    } on TimeoutException {
+      return bail(
+        'Timed out after ${timeout.inMilliseconds}ms waiting for the expected reset disconnect.',
+      );
+    } catch (error) {
+      return bail('Failed while waiting for expected reset disconnect: $error');
+    }
+  }
+
+  @override
+  Future<Result<void>> reconnectForVerification({
+    required Duration timeout,
+  }) async {
+    final connectResult =
+        await bluetoothController.connectById(buttonDeviceId, timeout: timeout);
+    if (connectResult.isErr()) {
+      return bail(connectResult.unwrapErr());
+    }
+
+    final currentState = bluetoothController.currentConnectionState;
+    if (currentState.$1 == ConnectionStatus.connected &&
+        currentState.$2 == buttonDeviceId) {
+      return Ok(null);
+    }
+
+    try {
+      await bluetoothController.connectionStateStream
+          .firstWhere(
+            (state) =>
+                state.$1 == ConnectionStatus.connected &&
+                state.$2 == buttonDeviceId,
+          )
+          .timeout(timeout);
+      return Ok(null);
+    } on TimeoutException {
+      return bail(
+        'Timed out after ${timeout.inMilliseconds}ms waiting for reconnect.',
+      );
+    } catch (error) {
+      return bail('Reconnect wait failed: $error');
+    }
+  }
+
+  @override
+  Future<Result<void>> verifyDeviceReachable({
+    required Duration timeout,
+  }) async {
+    try {
+      final statusResult = await shifterService.readStatus().timeout(timeout);
+      if (statusResult.isErr()) {
+        return bail(statusResult.unwrapErr());
+      }
+      return Ok(null);
+    } on TimeoutException {
+      return bail(
+        'Timed out after ${timeout.inMilliseconds}ms while reading status for post-update verification.',
+      );
+    } catch (error) {
+      return bail('Post-update verification failed: $error');
+    }
+  }
+}
+
+class _DfuFailure implements Exception {
+  const _DfuFailure(this.message);
+
+  final String message;
+
+  @override
+  String toString() => message;
+}
+
+class _DfuCancelled implements Exception {
+  const _DfuCancelled();
+}
--- a/lib/service/shifter_service.dart
+++ b/lib/service/shifter_service.dart
@ -6,12 +6,30 @@ import 'package:anyhow/anyhow.dart';

 class ShifterService {
  ShifterService({
-    required BluetoothController bluetooth,
+    BluetoothController? bluetooth,
    required this.buttonDeviceId,
-  }) : _bluetooth = bluetooth;
+    DfuPreflightBluetoothAdapter? dfuPreflightBluetooth,
+  })  : _bluetooth = bluetooth,
+        _dfuPreflightBluetooth =
+            dfuPreflightBluetooth ?? _BluetoothDfuPreflightAdapter(bluetooth!) {
+    if (bluetooth == null && dfuPreflightBluetooth == null) {
+      throw ArgumentError(
+        'Either bluetooth or dfuPreflightBluetooth must be provided.',
+      );
+    }
+  }

-  final BluetoothController _bluetooth;
+  final BluetoothController? _bluetooth;
  final String buttonDeviceId;
+  final DfuPreflightBluetoothAdapter _dfuPreflightBluetooth;
+
+  BluetoothController get _requireBluetooth {
+    final bluetooth = _bluetooth;
+    if (bluetooth == null) {
+      throw StateError('Bluetooth controller is not available.');
+    }
+    return bluetooth;
+  }

  final StreamController<CentralStatus> _statusController =
      StreamController<CentralStatus>.broadcast();
@ -20,13 +38,15 @@ class ShifterService {
  Stream<CentralStatus> get statusStream => _statusController.stream;

  static const int _gearRatioSlots = 32;
+  static const int _defaultGearIndexOffset = _gearRatioSlots;
+  static const int _gearRatioPayloadBytes = _gearRatioSlots + 1;
  static const double _maxGearRatio = 255 / 64;
  static const int _gearRatioWriteMtu = 64;

  Future<Result<void>> writeConnectToAddress(String bikeDeviceId) async {
    try {
      final payload = parseMacToLittleEndianBytes(bikeDeviceId);
-      return _bluetooth.writeCharacteristic(
+      return _requireBluetooth.writeCharacteristic(
        buttonDeviceId,
        universalShifterControlServiceUuid,
        universalShifterConnectToAddrCharacteristicUuid,
@ -40,7 +60,7 @@ class ShifterService {
  }

  Future<Result<void>> writeCommand(UniversalShifterCommand command) {
-    return _bluetooth.writeCharacteristic(
+    return _requireBluetooth.writeCharacteristic(
      buttonDeviceId,
      universalShifterControlServiceUuid,
      universalShifterCommandCharacteristicUuid,
@ -56,8 +76,8 @@ class ShifterService {
    return writeCommand(UniversalShifterCommand.connectToDevice);
  }

-  Future<Result<List<double>>> readGearRatios() async {
-    final readRes = await _bluetooth.readCharacteristic(
+  Future<Result<GearRatiosData>> readGearRatios() async {
+    final readRes = await _requireBluetooth.readCharacteristic(
      buttonDeviceId,
      universalShifterControlServiceUuid,
      universalShifterGearRatiosCharacteristicUuid,
@ -67,40 +87,64 @@ class ShifterService {
    }

    final raw = readRes.unwrap();
-    if (raw.length > _gearRatioSlots) {
+    if (raw.length > _gearRatioPayloadBytes) {
      return bail(
-        'Invalid gear ratio payload length: expected at most $_gearRatioSlots, got ${raw.length}',
+        'Invalid gear ratio payload length: expected at most $_gearRatioPayloadBytes, got ${raw.length}',
      );
    }

-    final normalizedRaw = List<int>.filled(_gearRatioSlots, 0, growable: false);
+    final normalizedRaw = List<int>.filled(
+      _gearRatioPayloadBytes,
+      0,
+      growable: false,
+    );
    for (var i = 0; i < raw.length; i++) {
      normalizedRaw[i] = raw[i];
    }

-    final ratios = normalizedRaw
-        .where((v) => v > 0)
-        .map((v) => _decodeGearRatio(v))
-        .toList(growable: false);
-    return Ok(ratios);
+    final ratios = <double>[];
+    for (var i = 0; i < _gearRatioSlots; i++) {
+      final value = normalizedRaw[i];
+      if (value == 0) {
+        break;
+      }
+      ratios.add(_decodeGearRatio(value));
+    }
+
+    final defaultIndexRaw = normalizedRaw[_defaultGearIndexOffset];
+    final defaultGearIndex = ratios.isEmpty
+        ? 0
+        : defaultIndexRaw.clamp(0, ratios.length - 1).toInt();
+    return Ok(
+      GearRatiosData(
+        ratios: ratios,
+        defaultGearIndex: defaultGearIndex,
+      ),
+    );
  }

-  Future<Result<void>> writeGearRatios(List<double> ratios) async {
-    final mtuResult =
-        await _bluetooth.requestMtu(buttonDeviceId, mtu: _gearRatioWriteMtu);
+  Future<Result<void>> writeGearRatios(GearRatiosData data) async {
+    final mtuResult = await _requireBluetooth.requestMtu(
+      buttonDeviceId,
+      mtu: _gearRatioWriteMtu,
+    );
    if (mtuResult.isErr()) {
      return bail(
          'Could not request MTU before writing gear ratios: ${mtuResult.unwrapErr()}');
    }

-    final payload = List<int>.filled(_gearRatioSlots, 0, growable: false);
+    final payload =
+        List<int>.filled(_gearRatioPayloadBytes, 0, growable: false);
+    final ratios = data.ratios;
    final limit =
        ratios.length < _gearRatioSlots ? ratios.length : _gearRatioSlots;
    for (var i = 0; i < limit; i++) {
      payload[i] = _encodeGearRatio(ratios[i]);
    }
+    payload[_defaultGearIndexOffset] =
+        limit == 0 ? 0 : data.defaultGearIndex.clamp(0, limit - 1).toInt();

-    return _bluetooth.writeCharacteristic(
+    return _requireBluetooth.writeCharacteristic(
      buttonDeviceId,
      universalShifterControlServiceUuid,
      universalShifterGearRatiosCharacteristicUuid,
@ -109,7 +153,7 @@ class ShifterService {
  }

  Future<Result<CentralStatus>> readStatus() async {
-    final readRes = await _bluetooth.readCharacteristic(
+    final readRes = await _requireBluetooth.readCharacteristic(
      buttonDeviceId,
      universalShifterControlServiceUuid,
      universalShifterStatusCharacteristicUuid,
@ -125,12 +169,78 @@ class ShifterService {
    }
  }

+  Future<Result<DfuPreflightResult>> runDfuPreflight({
+    int requestedMtu = universalShifterDfuPreferredMtu,
+  }) async {
+    final currentConnection = _dfuPreflightBluetooth.currentConnectionState;
+    final connectionStatus = currentConnection.$1;
+    final connectedDeviceId = currentConnection.$2;
+
+    if (connectionStatus != ConnectionStatus.connected ||
+        connectedDeviceId == null) {
+      return Ok(
+        DfuPreflightResult.failed(
+          requestedMtu: requestedMtu,
+          failureReason: DfuPreflightFailureReason.deviceNotConnected,
+          message:
+              'No button connection is active. Connect the target button, then retry the firmware update.',
+        ),
+      );
+    }
+
+    if (connectedDeviceId != buttonDeviceId) {
+      return Ok(
+        DfuPreflightResult.failed(
+          requestedMtu: requestedMtu,
+          failureReason: DfuPreflightFailureReason.wrongConnectedDevice,
+          message:
+              'Connected to a different button ($connectedDeviceId). Reconnect to $buttonDeviceId before starting the firmware update.',
+        ),
+      );
+    }
+
+    final mtuResult = await _dfuPreflightBluetooth.requestMtuAndGetValue(
+      buttonDeviceId,
+      mtu: requestedMtu,
+    );
+    if (mtuResult.isErr()) {
+      return Ok(
+        DfuPreflightResult.failed(
+          requestedMtu: requestedMtu,
+          failureReason: DfuPreflightFailureReason.mtuRequestFailed,
+          message:
+              'Could not negotiate BLE MTU for DFU. Move closer to the button and retry. Details: ${mtuResult.unwrapErr()}',
+        ),
+      );
+    }
+
+    final negotiatedMtu = mtuResult.unwrap();
+    if (negotiatedMtu < universalShifterDfuMinimumMtu) {
+      return Ok(
+        DfuPreflightResult.failed(
+          requestedMtu: requestedMtu,
+          negotiatedMtu: negotiatedMtu,
+          failureReason: DfuPreflightFailureReason.mtuTooLow,
+          message:
+              'Negotiated MTU $negotiatedMtu is too small for 64-byte DFU frames. Need at least $universalShifterDfuMinimumMtu bytes MTU (64-byte frame + $universalShifterAttWriteOverheadBytes-byte ATT overhead). Reconnect and retry.',
+        ),
+      );
+    }
+
+    return Ok(
+      DfuPreflightResult.ready(
+        requestedMtu: requestedMtu,
+        negotiatedMtu: negotiatedMtu,
+      ),
+    );
+  }
+
  void startStatusNotifications() {
    if (_statusSubscription != null) {
      return;
    }

-    _statusSubscription = _bluetooth
+    _statusSubscription = _requireBluetooth
        .subscribeToCharacteristic(
      buttonDeviceId,
      universalShifterControlServiceUuid,
@ -177,3 +287,39 @@ class ShifterService {
    return raw / 64.0;
  }
 }
+
+abstract interface class DfuPreflightBluetoothAdapter {
+  (ConnectionStatus, String?) get currentConnectionState;
+  Future<Result<int>> requestMtuAndGetValue(
+    String deviceId, {
+    required int mtu,
+  });
+}
+
+class _BluetoothDfuPreflightAdapter implements DfuPreflightBluetoothAdapter {
+  const _BluetoothDfuPreflightAdapter(this._bluetooth);
+
+  final BluetoothController _bluetooth;
+
+  @override
+  (ConnectionStatus, String?) get currentConnectionState =>
+      _bluetooth.currentConnectionState;
+
+  @override
+  Future<Result<int>> requestMtuAndGetValue(
+    String deviceId, {
+    required int mtu,
+  }) {
+    return _bluetooth.requestMtuAndGetValue(deviceId, mtu: mtu);
+  }
+}
+
+class GearRatiosData {
+  const GearRatiosData({
+    required this.ratios,
+    required this.defaultGearIndex,
+  });
+
+  final List<double> ratios;
+  final int defaultGearIndex;
+}
--- a/lib/widgets/gear_ratio_editor_card.dart
+++ b/lib/widgets/gear_ratio_editor_card.dart
@ -17,6 +17,7 @@ class GearRatioPreset {
 class GearRatioEditorCard extends StatefulWidget {
  const GearRatioEditorCard({
    required this.ratios,
+    required this.defaultGearIndex,
    required this.isLoading,
    required this.onSave,
    required this.presets,
@ -26,8 +27,10 @@ class GearRatioEditorCard extends StatefulWidget {
  });

  final List<double> ratios;
+  final int defaultGearIndex;
  final bool isLoading;
-  final Future<String?> Function(List<double> ratios) onSave;
+  final Future<String?> Function(List<double> ratios, int defaultGearIndex)
+      onSave;
  final List<GearRatioPreset> presets;
  final String? errorText;
  final VoidCallback? onRetry;
@ -43,6 +46,11 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
  static const double _sliderPivotV = 1.00;
  static const Duration _animDuration = Duration(milliseconds: 280);
  static const Curve _animCurve = Cubic(0.2, 0.8, 0.2, 1.0);
+  static const int _maxGears = 32;
+  static const double _inlineAddRadius = 24;
+  static const double _editorTileOverlap = 20;
+
+  double get _inlineAddEdgeOffset => _inlineAddRadius + 2;

  bool _isExpanded = false;
  bool _isEditing = false;
@ -54,20 +62,34 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {

  List<double> _committed = const [];
  List<double> _draft = const [];
+  int _committedDefaultGearIndex = 0;
+  int _draftDefaultGearIndex = 0;

  @override
  void initState() {
    super.initState();
    _committed = List<double>.from(widget.ratios);
    _draft = List<double>.from(widget.ratios);
+    _committedDefaultGearIndex = _normalizeDefaultIndex(
+      widget.defaultGearIndex,
+      _committed.length,
+    );
+    _draftDefaultGearIndex = _committedDefaultGearIndex;
  }

  @override
  void didUpdateWidget(covariant GearRatioEditorCard oldWidget) {
    super.didUpdateWidget(oldWidget);
-    if (!_isEditing && !_listEquals(oldWidget.ratios, widget.ratios)) {
+    if (!_isEditing &&
+        (!_listEquals(oldWidget.ratios, widget.ratios) ||
+            oldWidget.defaultGearIndex != widget.defaultGearIndex)) {
      _committed = List<double>.from(widget.ratios);
      _draft = List<double>.from(widget.ratios);
+      _committedDefaultGearIndex = _normalizeDefaultIndex(
+        widget.defaultGearIndex,
+        _committed.length,
+      );
+      _draftDefaultGearIndex = _committedDefaultGearIndex;
    }
  }

@ -172,7 +194,7 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
                    child: AnimatedContainer(
                      duration: _animDuration,
                      curve: _animCurve,
-                      height: _isExpanded ? 210 : 130,
+                      height: _isExpanded ? 240 : 130,
                      child: _GearRatioGraph(
                        ratios: _isEditing ? _draft : _committed,
                        compact: !_isExpanded,
@ -183,7 +205,11 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
              if (!_isExpanded && !_isEditing && _committed.isNotEmpty)
                Padding(
                  padding: const EdgeInsets.fromLTRB(14, 0, 14, 10),
-                  child: _compactRatioStrip(context, _committed),
+                  child: _compactRatioStrip(
+                    context,
+                    _committed,
+                    defaultGearIndex: _committedDefaultGearIndex,
+                  ),
                ),
              AnimatedSize(
                duration: _animDuration,
@ -197,7 +223,12 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
                          runSpacing: 8,
                          children: [
                            for (var i = 0; i < _committed.length; i++)
-                              _ratioChip(context, i + 1, _committed[i]),
+                              _ratioChip(
+                                context,
+                                i + 1,
+                                _committed[i],
+                                isDefault: i == _committedDefaultGearIndex,
+                              ),
                          ],
                        ),
                      )
@ -232,8 +263,8 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
                if (_draft.isEmpty)
                  const Padding(
                    padding: EdgeInsets.fromLTRB(14, 0, 14, 10),
-                    child:
-                        Text('No ratios yet. Load a preset to start editing.'),
+                    child: Text(
+                        'No ratios yet. Add a gear or load a preset to start editing.'),
                  ),
                Padding(
                  padding: const EdgeInsets.fromLTRB(14, 0, 14, 8),
@ -274,23 +305,16 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
                  ),
                ),
                Padding(
-                  padding: const EdgeInsets.fromLTRB(10, 0, 10, 12),
+                  padding: const EdgeInsets.fromLTRB(10, 0, 10, 0),
                  child: AnimatedSwitcher(
                    duration: _animDuration,
                    switchInCurve: _animCurve,
                    switchOutCurve: Curves.easeInCubic,
                    transitionBuilder: _snappyTransition,
-                    child: Wrap(
+                    child: Column(
                      key: ValueKey('editors-$_gearLayoutVersion'),
-                      spacing: 8,
-                      runSpacing: 8,
-                      children: [
-                        for (var i = 0; i < _draft.length; i++)
-                          KeyedSubtree(
-                            key: ValueKey('editor-${i + 1}'),
-                            child: _buildGearEditor(context, i),
-                          ),
-                      ],
+                      crossAxisAlignment: CrossAxisAlignment.stretch,
+                      children: _buildEditableGearTiles(context),
                    ),
                  ),
                ),
@ -314,73 +338,307 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
    );
  }

-  Widget _buildGearEditor(BuildContext context, int index) {
-    final ratio = _draft[index];
-    final sliderValue = _valueToSlider(ratio);
-    return ConstrainedBox(
-      constraints: const BoxConstraints(minWidth: 230, maxWidth: 280),
-      child: Container(
-        padding: const EdgeInsets.fromLTRB(10, 8, 10, 4),
-        decoration: BoxDecoration(
-          borderRadius: BorderRadius.circular(12),
-          color: Theme.of(context).colorScheme.surface.withValues(alpha: 0.7),
-          border: Border.all(
-            color: Theme.of(context)
-                .colorScheme
-                .outlineVariant
-                .withValues(alpha: 0.6),
+  List<Widget> _buildEditableGearTiles(BuildContext context) {
+    if (_draft.isEmpty) {
+      return [_buildStandaloneAddGearButton(context)];
+    }
+
+    final widgets = <Widget>[];
+    for (var i = 0; i < _draft.length; i++) {
+      final editor = KeyedSubtree(
+        key: ValueKey('editor-${i + 1}'),
+        child: _buildGearEditor(context, i),
+      );
+      if (i == 0) {
+        widgets.add(editor);
+      } else {
+        widgets.add(
+          Transform.translate(
+            offset: Offset(0, -i * _editorTileOverlap),
+            child: editor,
          ),
-        ),
-        child: Column(
-          crossAxisAlignment: CrossAxisAlignment.start,
-          children: [
-            Row(
-              children: [
-                Text(
-                  'Gear ${index + 1}',
-                  style: const TextStyle(fontWeight: FontWeight.w600),
-                ),
-                const Spacer(),
-                InkWell(
-                  borderRadius: BorderRadius.circular(6),
-                  onTap: () => _editRatioText(index),
-                  child: Padding(
-                    padding:
-                        const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
-                    child: Text(
-                      ratio.toStringAsFixed(2),
-                      style: const TextStyle(
-                        fontSize: 15,
-                        fontWeight: FontWeight.w700,
-                      ),
-                    ),
-                  ),
-                ),
-              ],
-            ),
-            Slider(
-              min: 0,
-              max: 1,
-              value: sliderValue,
-              onChanged: (value) {
-                setState(() {
-                  _draft[index] = _quantizeRatio(_sliderToValue(value));
-                });
-              },
-              onChangeEnd: (_) {
-                setState(() {
-                  if (_sortAscending) {
-                    _sortDraft(animate: true);
-                  }
-                });
-              },
-            ),
-          ],
+        );
+      }
+    }
+    return widgets;
+  }
+
+  Widget _buildStandaloneAddGearButton(BuildContext context) {
+    final canAdd = _draft.length < _maxGears;
+    return SizedBox(
+      width: double.infinity,
+      height: 118,
+      child: Center(
+        child: _buildInlineAddButton(
+          context,
+          afterIndex: -1,
+          canAdd: canAdd,
        ),
      ),
    );
  }

+  Widget _buildInlineAddButton(
+    BuildContext context, {
+    required int afterIndex,
+    required bool canAdd,
+    String? tooltip,
+  }) {
+    final theme = Theme.of(context);
+    return Tooltip(
+      message: canAdd ? 'Add gear' : 'Maximum $_maxGears gears reached',
+      child: Material(
+        type: MaterialType.transparency,
+        child: Ink(
+          width: _inlineAddRadius * 2,
+          height: _inlineAddRadius * 2,
+          decoration: ShapeDecoration(
+            shape: CircleBorder(
+              side: BorderSide(
+                color: theme.colorScheme.outlineVariant.withValues(alpha: 0.8),
+              ),
+            ),
+            color: theme.colorScheme.surface,
+            shadows: [
+              BoxShadow(
+                blurRadius: 12,
+                spreadRadius: 1,
+                color: Colors.black.withValues(alpha: 0.12),
+              ),
+            ],
+          ),
+          child: IconButton(
+            onPressed: canAdd ? () => _insertGearAfter(afterIndex) : null,
+            icon: const Icon(Icons.add),
+            iconSize: 22,
+            splashRadius: _inlineAddRadius,
+            tooltip: canAdd ? tooltip ?? 'Add gear' : null,
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildGearEditor(BuildContext context, int index) {
+    final theme = Theme.of(context);
+    final canAdd = _draft.length < _maxGears;
+    final ratio = _draft[index];
+    final sliderValue = _valueToSlider(ratio);
+    final isDefault = index == _draftDefaultGearIndex;
+    final borderColor = isDefault
+        ? theme.colorScheme.primary
+        : theme.colorScheme.outlineVariant.withValues(alpha: 0.6);
+    return Stack(
+      children: [
+        Padding(
+          padding: EdgeInsets.only(
+            right: _inlineAddEdgeOffset,
+            top: index == 0 ? _inlineAddEdgeOffset : 0,
+            bottom: _inlineAddEdgeOffset,
+          ),
+          child: ClipPath(
+            clipper: _GearEditorNotchClipper(
+              topNotchRadius: _inlineAddRadius + 2,
+              bottomNotchRadius: _inlineAddRadius + 2,
+            ),
+            child: Material(
+              color: theme.colorScheme.surface.withValues(alpha: 0.7),
+              borderRadius: BorderRadius.circular(12),
+              child: InkWell(
+                borderRadius: BorderRadius.circular(12),
+                onTap: () => _setDefaultGear(index),
+                child: Container(
+                  padding: const EdgeInsets.fromLTRB(10, 8, 10, 4),
+                  decoration: BoxDecoration(
+                    borderRadius: BorderRadius.circular(12),
+                    border: Border.all(
+                      color: borderColor,
+                      width: isDefault ? 1.6 : 1,
+                    ),
+                  ),
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: [
+                      Row(
+                        children: [
+                          Text(
+                            'Gear ${index + 1}',
+                            style: const TextStyle(fontWeight: FontWeight.w600),
+                          ),
+                          const SizedBox(width: 8),
+                          if (isDefault)
+                            Container(
+                              padding: const EdgeInsets.symmetric(
+                                horizontal: 8,
+                                vertical: 2,
+                              ),
+                              decoration: BoxDecoration(
+                                borderRadius: BorderRadius.circular(999),
+                                color: theme.colorScheme.primaryContainer,
+                                border: Border.all(
+                                  color: theme.colorScheme.primary.withValues(
+                                    alpha: 0.65,
+                                  ),
+                                ),
+                              ),
+                              child: Text(
+                                'default',
+                                style: theme.textTheme.labelSmall?.copyWith(
+                                  color: theme.colorScheme.onPrimaryContainer,
+                                  fontWeight: FontWeight.w700,
+                                ),
+                              ),
+                            ),
+                          const Spacer(),
+                          IconButton(
+                            visualDensity: VisualDensity.compact,
+                            tooltip: 'Delete gear',
+                            onPressed: () => _deleteGear(index),
+                            icon: const Icon(Icons.delete_outline),
+                          ),
+                          InkWell(
+                            borderRadius: BorderRadius.circular(6),
+                            onTap: () => _editRatioText(index),
+                            child: Padding(
+                              padding: const EdgeInsets.symmetric(
+                                horizontal: 8,
+                                vertical: 4,
+                              ),
+                              child: Text(
+                                ratio.toStringAsFixed(2),
+                                style: const TextStyle(
+                                  fontSize: 15,
+                                  fontWeight: FontWeight.w700,
+                                ),
+                              ),
+                            ),
+                          ),
+                        ],
+                      ),
+                      Slider(
+                        min: 0,
+                        max: 1,
+                        value: sliderValue,
+                        onChanged: (value) {
+                          setState(() {
+                            _draft[index] =
+                                _quantizeRatio(_sliderToValue(value));
+                          });
+                        },
+                        onChangeEnd: (_) {
+                          setState(() {
+                            if (_sortAscending) {
+                              _sortDraft(animate: true);
+                            }
+                          });
+                        },
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+            ),
+          ),
+        ),
+        if (index == 0)
+          Positioned(
+            top: 0,
+            right: 0,
+            child: _buildInlineAddButton(
+              context,
+              afterIndex: index - 1,
+              canAdd: canAdd,
+              tooltip: 'Insert gear before',
+            ),
+          ),
+        Positioned(
+          bottom: 0,
+          right: 0,
+          child: _buildInlineAddButton(
+            context,
+            afterIndex: index,
+            canAdd: canAdd,
+            tooltip: 'Insert gear after',
+          ),
+        ),
+      ],
+    );
+  }
+
+  void _insertGearAfter(int index) {
+    if (_draft.length >= _maxGears) {
+      return;
+    }
+    final insertIndex = (index + 1).clamp(0, _draft.length);
+    final newRatio = _nextInsertedRatio(insertIndex);
+
+    setState(() {
+      final next = List<double>.from(_draft)..insert(insertIndex, newRatio);
+      _draft = next;
+      if (insertIndex <= _draftDefaultGearIndex) {
+        _draftDefaultGearIndex += 1;
+      }
+      _draftDefaultGearIndex = _normalizeDefaultIndex(
+        _draftDefaultGearIndex,
+        _draft.length,
+      );
+      if (_sortAscending) {
+        _sortDraft(animate: true);
+      } else {
+        _gearLayoutVersion++;
+      }
+      _stretchBase = null;
+    });
+  }
+
+  void _deleteGear(int index) {
+    if (_draft.isEmpty || index < 0 || index >= _draft.length) {
+      return;
+    }
+
+    setState(() {
+      final next = List<double>.from(_draft)..removeAt(index);
+      _draft = next;
+
+      if (_draft.isEmpty) {
+        _draftDefaultGearIndex = 0;
+      } else if (index < _draftDefaultGearIndex) {
+        _draftDefaultGearIndex -= 1;
+      } else if (index == _draftDefaultGearIndex) {
+        _draftDefaultGearIndex = index.clamp(0, _draft.length - 1);
+      }
+
+      _draftDefaultGearIndex = _normalizeDefaultIndex(
+        _draftDefaultGearIndex,
+        _draft.length,
+      );
+      _gearLayoutVersion++;
+      _stretchBase = null;
+    });
+  }
+
+  void _setDefaultGear(int index) {
+    if (index < 0 || index >= _draft.length) {
+      return;
+    }
+    setState(() {
+      _draftDefaultGearIndex = index;
+    });
+  }
+
+  double _nextInsertedRatio(int insertIndex) {
+    if (_draft.isEmpty) {
+      return _quantizeRatio(1.0);
+    }
+    if (insertIndex <= 0) {
+      return _quantizeRatio(_draft.first * 0.9);
+    }
+    if (insertIndex >= _draft.length) {
+      return _quantizeRatio(_draft.last * 1.1);
+    }
+    return _quantizeRatio((_draft[insertIndex - 1] + _draft[insertIndex]) / 2);
+  }
+
  Future<void> _editRatioText(int index) async {
    final controller = TextEditingController(
      text: _draft[index].toStringAsFixed(2),
@ -493,6 +751,7 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {

    setState(() {
      _draft = selected.ratios.map(_quantizeRatio).toList(growable: false);
+      _draftDefaultGearIndex = _normalizeDefaultIndex(0, _draft.length);
      if (_sortAscending) {
        _sortDraft(animate: true);
      }
@ -500,11 +759,14 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
  }

  void _sortDraft({bool animate = false}) {
-    final sorted = _sorted(_draft);
-    if (animate && !_listEquals(_draft, sorted)) {
+    final sorted = _sortedWithDefault(_draft, _draftDefaultGearIndex);
+    final sortedValues = sorted.$1;
+    final sortedDefaultIndex = sorted.$2;
+    if (animate && !_listEquals(_draft, sortedValues)) {
      _gearLayoutVersion++;
    }
-    _draft = sorted;
+    _draft = sortedValues;
+    _draftDefaultGearIndex = sortedDefaultIndex;
  }

  void _enterEditMode() {
@ -514,6 +776,10 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
      _stretchFactor = 1.0;
      _stretchBase = null;
      _draft = List<double>.from(_committed);
+      _draftDefaultGearIndex = _normalizeDefaultIndex(
+        _committedDefaultGearIndex,
+        _draft.length,
+      );
    });
  }

@ -521,6 +787,10 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
    setState(() {
      _isEditing = false;
      _draft = List<double>.from(_committed);
+      _draftDefaultGearIndex = _normalizeDefaultIndex(
+        _committedDefaultGearIndex,
+        _draft.length,
+      );
      _stretchFactor = 1.0;
      _stretchBase = null;
    });
@ -531,7 +801,10 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
      _isSaving = true;
    });

-    final message = await widget.onSave(List<double>.from(_draft));
+    final message = await widget.onSave(
+      List<double>.from(_draft),
+      _normalizeDefaultIndex(_draftDefaultGearIndex, _draft.length),
+    );
    if (!mounted) {
      return;
    }
@ -540,6 +813,10 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
      _isSaving = false;
      if (message == null) {
        _committed = List<double>.from(_draft);
+        _committedDefaultGearIndex = _normalizeDefaultIndex(
+          _draftDefaultGearIndex,
+          _committed.length,
+        );
        _isEditing = false;
      }
    });
@ -551,7 +828,12 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
    }
  }

-  Widget _ratioChip(BuildContext context, int gear, double ratio) {
+  Widget _ratioChip(
+    BuildContext context,
+    int gear,
+    double ratio, {
+    bool isDefault = false,
+  }) {
    final theme = Theme.of(context);
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 6),
@ -559,10 +841,17 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
        borderRadius: BorderRadius.circular(999),
        color: theme.colorScheme.surface.withValues(alpha: 0.7),
        border: Border.all(
-          color: theme.colorScheme.outlineVariant.withValues(alpha: 0.6),
+          color: isDefault
+              ? theme.colorScheme.primary
+              : theme.colorScheme.outlineVariant.withValues(alpha: 0.6),
+          width: isDefault ? 1.4 : 1,
        ),
      ),
-      child: Text('G$gear  ${ratio.toStringAsFixed(2)}'),
+      child: Text(
+        isDefault
+            ? 'G$gear  ${ratio.toStringAsFixed(2)}  default'
+            : 'G$gear  ${ratio.toStringAsFixed(2)}',
+      ),
    );
  }

@ -570,6 +859,7 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
    BuildContext context,
    List<double> ratios, {
    bool showGearLabel = true,
+    int? defaultGearIndex,
  }) {
    final theme = Theme.of(context);
    return SizedBox(
@ -588,13 +878,18 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
                    borderRadius: BorderRadius.circular(999),
                    color: theme.colorScheme.surface.withValues(alpha: 0.7),
                    border: Border.all(
-                      color: theme.colorScheme.outlineVariant
-                          .withValues(alpha: 0.55),
+                      color: i == defaultGearIndex
+                          ? theme.colorScheme.primary
+                          : theme.colorScheme.outlineVariant
+                              .withValues(alpha: 0.55),
+                      width: i == defaultGearIndex ? 1.3 : 1,
                    ),
                  ),
                  child: Text(
                    showGearLabel
-                        ? 'G${i + 1} ${ratios[i].toStringAsFixed(2)}'
+                        ? (i == defaultGearIndex
+                            ? 'G${i + 1} ${ratios[i].toStringAsFixed(2)} default'
+                            : 'G${i + 1} ${ratios[i].toStringAsFixed(2)}')
                        : ratios[i].toStringAsFixed(2),
                    style: theme.textTheme.bodySmall?.copyWith(
                      fontWeight: FontWeight.w600,
@ -613,9 +908,34 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
    return ((clamped * 64).round() / 64.0).clamp(_sliderMin, _sliderMax);
  }

-  List<double> _sorted(List<double> values) {
-    final out = List<double>.from(values)..sort();
-    return out;
+  (List<double>, int) _sortedWithDefault(
+      List<double> values, int defaultIndex) {
+    final normalizedDefault =
+        _normalizeDefaultIndex(defaultIndex, values.length);
+    final decorated = List<_DraftGearEntry>.generate(
+      values.length,
+      (i) => _DraftGearEntry(
+        ratio: values[i],
+        isDefault: i == normalizedDefault,
+      ),
+      growable: false,
+    )..sort((a, b) => a.ratio.compareTo(b.ratio));
+
+    final sortedValues = decorated.map((entry) => entry.ratio).toList(
+          growable: false,
+        );
+    final sortedDefaultIndex = decorated.indexWhere((entry) => entry.isDefault);
+    return (
+      sortedValues,
+      _normalizeDefaultIndex(sortedDefaultIndex, sortedValues.length),
+    );
+  }
+
+  int _normalizeDefaultIndex(int index, int length) {
+    if (length <= 0) {
+      return 0;
+    }
+    return index.clamp(0, length - 1).toInt();
  }

  bool _listEquals(List<double> a, List<double> b) {
@ -661,6 +981,69 @@ class _GearRatioEditorCardState extends State<GearRatioEditorCard> {
  }
 }

+class _DraftGearEntry {
+  const _DraftGearEntry({required this.ratio, required this.isDefault});
+
+  final double ratio;
+  final bool isDefault;
+}
+
+class _GearEditorNotchClipper extends CustomClipper<Path> {
+  const _GearEditorNotchClipper({
+    required this.topNotchRadius,
+    required this.bottomNotchRadius,
+  });
+
+  final double topNotchRadius;
+  final double bottomNotchRadius;
+
+  @override
+  Path getClip(Size size) {
+    final base = Path()
+      ..addRRect(
+        RRect.fromRectAndRadius(
+          Offset.zero & size,
+          const Radius.circular(12),
+        ),
+      );
+
+    if (topNotchRadius <= 0 && bottomNotchRadius <= 0) {
+      return base;
+    }
+
+    var clipped = base;
+    if (topNotchRadius > 0) {
+      final topNotch = Path()
+        ..addOval(
+          Rect.fromCircle(
+            center: Offset(size.width, 0),
+            radius: topNotchRadius,
+          ),
+        );
+      clipped = Path.combine(PathOperation.difference, clipped, topNotch);
+    }
+
+    if (bottomNotchRadius > 0) {
+      final bottomNotch = Path()
+        ..addOval(
+          Rect.fromCircle(
+            center: Offset(size.width, size.height),
+            radius: bottomNotchRadius,
+          ),
+        );
+      clipped = Path.combine(PathOperation.difference, clipped, bottomNotch);
+    }
+
+    return clipped;
+  }
+
+  @override
+  bool shouldReclip(covariant _GearEditorNotchClipper oldClipper) {
+    return oldClipper.topNotchRadius != topNotchRadius ||
+        oldClipper.bottomNotchRadius != bottomNotchRadius;
+  }
+}
+
 class _GearRatioGraph extends StatelessWidget {
  const _GearRatioGraph({required this.ratios, required this.compact});

@ -681,9 +1064,12 @@ class _GearRatioGraph extends StatelessWidget {
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            if (!compact)
-              Text(
-                'Input RPM -> Output RPM',
-                style: textTheme.bodySmall,
+              Container(
+                padding: const EdgeInsets.only(bottom: 6),
+                child: Text(
+                  'Input RPM -> Output RPM',
+                  style: textTheme.bodySmall,
+                ),
              ),
            Expanded(
              child: CustomPaint(
--- a/macos/Flutter/GeneratedPluginRegistrant.swift
+++ b/macos/Flutter/GeneratedPluginRegistrant.swift
@ -6,6 +6,7 @@ import FlutterMacOS
 import Foundation

 import connectivity_plus
+import file_picker
 import flutter_blue_plus_darwin
 import nb_utils
 import path_provider_foundation
@ -15,6 +16,7 @@ import sqlite3_flutter_libs

 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
  ConnectivityPlusPlugin.register(with: registry.registrar(forPlugin: "ConnectivityPlusPlugin"))
+  FilePickerPlugin.register(with: registry.registrar(forPlugin: "FilePickerPlugin"))
  FlutterBluePlusPlugin.register(with: registry.registrar(forPlugin: "FlutterBluePlusPlugin"))
  NbUtilsPlugin.register(with: registry.registrar(forPlugin: "NbUtilsPlugin"))
  PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
--- a/pubspec.lock
+++ b/pubspec.lock
@ -233,6 +233,14 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "3.1.2"
+  cross_file:
+    dependency: transitive
+    description:
+      name: cross_file
+      sha256: "28bb3ae56f117b5aec029d702a90f57d285cd975c3c5c281eaca38dbc47c5937"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.3.5+2"
  crypto:
    dependency: transitive
    description:
@ -345,6 +353,14 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "7.0.1"
+  file_picker:
+    dependency: "direct main"
+    description:
+      name: file_picker
+      sha256: ab13ae8ef5580a411c458d6207b6774a6c237d77ac37011b13994879f68a8810
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.3.7"
  fixnum:
    dependency: transitive
    description:
@ -427,6 +443,14 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "5.0.0"
+  flutter_plugin_android_lifecycle:
+    dependency: transitive
+    description:
+      name: flutter_plugin_android_lifecycle
+      sha256: ee8068e0e1cd16c4a82714119918efdeed33b3ba7772c54b5d094ab53f9b7fd1
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.33"
  flutter_reactive_ble:
    dependency: "direct main"
    description:
@ -1187,6 +1211,14 @@ packages:
      url: "https://pub.dev"
    source: hosted
    version: "3.1.0"
+  win32:
+    dependency: transitive
+    description:
+      name: win32
+      sha256: "329edf97fdd893e0f1e3b9e88d6a0e627128cc17cc316a8d67fda8f1451178ba"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.13.0"
  xdg_directories:
    dependency: transitive
    description:
--- a/pubspec.yaml
+++ b/pubspec.yaml
@ -54,6 +54,7 @@ dependencies:
  flutter_reactive_ble: ^5.4.0
  nb_utils: ^7.2.0
  cbor: ^6.3.3
+  file_picker: ^8.1.7

 dev_dependencies:
  flutter_test:
--- a/test/service/dfu_preflight_test.dart
+++ b/test/service/dfu_preflight_test.dart
@ -0,0 +1,137 @@
+import 'package:abawo_bt_app/controller/bluetooth.dart';
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/shifter_service.dart';
+import 'package:anyhow/anyhow.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('ShifterService.runDfuPreflight', () {
+    test('fails when no active button connection exists', () async {
+      final adapter = _FakeDfuPreflightBluetoothAdapter(
+        currentConnectionState: (ConnectionStatus.disconnected, null),
+        mtuResult: Ok(128),
+      );
+      final service = ShifterService(
+        buttonDeviceId: 'target-device',
+        dfuPreflightBluetooth: adapter,
+      );
+
+      final result = await service.runDfuPreflight();
+
+      expect(result.isOk(), isTrue);
+      final preflight = result.unwrap();
+      expect(preflight.canStart, isFalse);
+      expect(preflight.failureReason,
+          DfuPreflightFailureReason.deviceNotConnected);
+      expect(adapter.requestMtuCallCount, 0);
+    });
+
+    test('fails when connected to a different button', () async {
+      final adapter = _FakeDfuPreflightBluetoothAdapter(
+        currentConnectionState: (ConnectionStatus.connected, 'wrong-device'),
+        mtuResult: Ok(128),
+      );
+      final service = ShifterService(
+        buttonDeviceId: 'target-device',
+        dfuPreflightBluetooth: adapter,
+      );
+
+      final result = await service.runDfuPreflight();
+
+      expect(result.isOk(), isTrue);
+      final preflight = result.unwrap();
+      expect(preflight.canStart, isFalse);
+      expect(preflight.failureReason,
+          DfuPreflightFailureReason.wrongConnectedDevice);
+      expect(adapter.requestMtuCallCount, 0);
+    });
+
+    test('fails when MTU negotiation fails', () async {
+      final adapter = _FakeDfuPreflightBluetoothAdapter(
+        currentConnectionState: (ConnectionStatus.connected, 'target-device'),
+        mtuResult: bail('adapter rejected mtu request'),
+      );
+      final service = ShifterService(
+        buttonDeviceId: 'target-device',
+        dfuPreflightBluetooth: adapter,
+      );
+
+      final result = await service.runDfuPreflight(requestedMtu: 247);
+
+      expect(result.isOk(), isTrue);
+      final preflight = result.unwrap();
+      expect(preflight.canStart, isFalse);
+      expect(
+          preflight.failureReason, DfuPreflightFailureReason.mtuRequestFailed);
+      expect(preflight.message, contains('adapter rejected mtu request'));
+      expect(adapter.requestedMtuValues, [247]);
+    });
+
+    test('fails when negotiated MTU is too low for 64-byte frame writes',
+        () async {
+      final adapter = _FakeDfuPreflightBluetoothAdapter(
+        currentConnectionState: (ConnectionStatus.connected, 'target-device'),
+        mtuResult: Ok(universalShifterDfuMinimumMtu - 1),
+      );
+      final service = ShifterService(
+        buttonDeviceId: 'target-device',
+        dfuPreflightBluetooth: adapter,
+      );
+
+      final result = await service.runDfuPreflight();
+
+      expect(result.isOk(), isTrue);
+      final preflight = result.unwrap();
+      expect(preflight.canStart, isFalse);
+      expect(preflight.failureReason, DfuPreflightFailureReason.mtuTooLow);
+      expect(preflight.negotiatedMtu, universalShifterDfuMinimumMtu - 1);
+      expect(preflight.requiredMtu, universalShifterDfuMinimumMtu);
+    });
+
+    test('passes when connected to target and MTU is sufficient', () async {
+      final adapter = _FakeDfuPreflightBluetoothAdapter(
+        currentConnectionState: (ConnectionStatus.connected, 'target-device'),
+        mtuResult: Ok(128),
+      );
+      final service = ShifterService(
+        buttonDeviceId: 'target-device',
+        dfuPreflightBluetooth: adapter,
+      );
+
+      final result = await service.runDfuPreflight();
+
+      expect(result.isOk(), isTrue);
+      final preflight = result.unwrap();
+      expect(preflight.canStart, isTrue);
+      expect(preflight.failureReason, isNull);
+      expect(preflight.negotiatedMtu, 128);
+      expect(preflight.requestedMtu, universalShifterDfuPreferredMtu);
+    });
+  });
+}
+
+class _FakeDfuPreflightBluetoothAdapter
+    implements DfuPreflightBluetoothAdapter {
+  _FakeDfuPreflightBluetoothAdapter({
+    required this.currentConnectionState,
+    required Result<int> mtuResult,
+  }) : _mtuResult = mtuResult;
+
+  @override
+  final (ConnectionStatus, String?) currentConnectionState;
+
+  final Result<int> _mtuResult;
+
+  int requestMtuCallCount = 0;
+  final List<int> requestedMtuValues = <int>[];
+
+  @override
+  Future<Result<int>> requestMtuAndGetValue(
+    String deviceId, {
+    required int mtu,
+  }) async {
+    requestMtuCallCount += 1;
+    requestedMtuValues.add(mtu);
+    return _mtuResult;
+  }
+}
--- a/test/service/dfu_protocol_test.dart
+++ b/test/service/dfu_protocol_test.dart
@ -0,0 +1,86 @@
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/dfu_protocol.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('DfuProtocol CRC32', () {
+    test('matches known vector', () {
+      final crc = DfuProtocol.crc32('123456789'.codeUnits);
+      expect(crc, 0xCBF43926);
+    });
+  });
+
+  group('DfuProtocol control payload encoding', () {
+    test('encodes START payload with exact 11-byte LE layout', () {
+      final payload = DfuProtocol.encodeStartPayload(
+        const DfuStartPayload(
+          totalLength: 0x1234,
+          imageCrc32: 0x89ABCDEF,
+          sessionId: 0x22,
+          flags: universalShifterDfuFlagEncrypted,
+        ),
+      );
+
+      expect(payload.length, 11);
+      expect(
+        payload,
+        [
+          universalShifterDfuOpcodeStart,
+          0x34,
+          0x12,
+          0x00,
+          0x00,
+          0xEF,
+          0xCD,
+          0xAB,
+          0x89,
+          0x22,
+          universalShifterDfuFlagEncrypted,
+        ],
+      );
+    });
+
+    test('encodes FINISH and ABORT payloads as one byte', () {
+      expect(
+          DfuProtocol.encodeFinishPayload(), [universalShifterDfuOpcodeFinish]);
+      expect(
+          DfuProtocol.encodeAbortPayload(), [universalShifterDfuOpcodeAbort]);
+    });
+  });
+
+  group('DfuProtocol data frame building', () {
+    test('builds 64-byte frames and handles final partial payload', () {
+      final image = List<int>.generate(80, (index) => index);
+      final frames = DfuProtocol.buildDataFrames(image);
+
+      expect(frames.length, 2);
+
+      expect(frames[0].sequence, 0);
+      expect(frames[0].offset, 0);
+      expect(frames[0].payloadLength, universalShifterDfuFramePayloadSizeBytes);
+      expect(frames[0].bytes.length, universalShifterDfuFrameSizeBytes);
+      expect(frames[0].bytes.sublist(1, 64), image.sublist(0, 63));
+
+      expect(frames[1].sequence, 1);
+      expect(frames[1].offset, 63);
+      expect(frames[1].payloadLength, 17);
+      expect(frames[1].bytes.length, universalShifterDfuFrameSizeBytes);
+      expect(frames[1].bytes.sublist(1, 18), image.sublist(63, 80));
+    });
+  });
+
+  group('DfuProtocol sequence and ACK helpers', () {
+    test('wraps sequence values and computes ack+1 rewind', () {
+      expect(DfuProtocol.nextSequence(0x00), 0x01);
+      expect(DfuProtocol.nextSequence(0xFF), 0x00);
+
+      expect(DfuProtocol.rewindSequenceFromAck(0x05), 0x06);
+      expect(DfuProtocol.rewindSequenceFromAck(0xFF), 0x00);
+    });
+
+    test('computes wrapping sequence distance', () {
+      expect(DfuProtocol.sequenceDistance(250, 2), 8);
+      expect(DfuProtocol.sequenceDistance(1, 1), 0);
+    });
+  });
+}
--- a/test/service/firmware_file_selection_service_test.dart
+++ b/test/service/firmware_file_selection_service_test.dart
@ -0,0 +1,132 @@
+import 'dart:typed_data';
+
+import 'package:abawo_bt_app/model/firmware_file_selection.dart';
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/firmware_file_selection_service.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('FirmwareFileSelectionService', () {
+    test('prepares v1 metadata for selected .bin firmware', () async {
+      final service = FirmwareFileSelectionService(
+        filePicker: _FakeFirmwareFilePicker(
+          selection: FirmwarePickerSelection(
+            fileName: 'firmware.BIN',
+            filePath: '/tmp/firmware.BIN',
+            fileBytes: Uint8List.fromList(<int>[1, 2, 3, 4]),
+          ),
+        ),
+        sessionIdGenerator: () => 0x1AB,
+      );
+
+      final result = await service.selectAndPrepareDfuV1();
+      expect(result.isSuccess, isTrue);
+
+      final firmware = result.firmware!;
+      expect(firmware.fileName, 'firmware.BIN');
+      expect(firmware.filePath, '/tmp/firmware.BIN');
+      expect(firmware.fileBytes, <int>[1, 2, 3, 4]);
+      expect(firmware.metadata.totalLength, 4);
+      expect(firmware.metadata.crc32, 0xB63CFBCD);
+      expect(firmware.metadata.sessionId, 0xAB);
+      expect(firmware.metadata.flags, universalShifterDfuFlagNone);
+    });
+
+    test('returns canceled result when user dismisses picker', () async {
+      final service = FirmwareFileSelectionService(
+        filePicker: _FakeFirmwareFilePicker(selection: null),
+      );
+
+      final result = await service.selectAndPrepareDfuV1();
+
+      expect(result.isSuccess, isFalse);
+      expect(result.isCanceled, isTrue);
+      expect(result.failure?.reason, FirmwareSelectionFailureReason.canceled);
+    });
+
+    test('rejects unsupported extension', () async {
+      final service = FirmwareFileSelectionService(
+        filePicker: _FakeFirmwareFilePicker(
+          selection: FirmwarePickerSelection(
+            fileName: 'firmware.hex',
+            fileBytes: Uint8List.fromList(<int>[1]),
+          ),
+        ),
+      );
+
+      final result = await service.selectAndPrepareDfuV1();
+
+      expect(result.isSuccess, isFalse);
+      expect(result.failure?.reason,
+          FirmwareSelectionFailureReason.unsupportedExtension);
+    });
+
+    test('rejects empty payload', () async {
+      final service = FirmwareFileSelectionService(
+        filePicker: _FakeFirmwareFilePicker(
+          selection: FirmwarePickerSelection(
+            fileName: 'firmware.bin',
+            fileBytes: Uint8List(0),
+          ),
+        ),
+      );
+
+      final result = await service.selectAndPrepareDfuV1();
+
+      expect(result.isSuccess, isFalse);
+      expect(result.failure?.reason, FirmwareSelectionFailureReason.emptyFile);
+    });
+
+    test('generates session id per run', () async {
+      var nextSession = 9;
+      final service = FirmwareFileSelectionService(
+        filePicker: _FakeFirmwareFilePicker(
+          selection: FirmwarePickerSelection(
+            fileName: 'firmware.bin',
+            fileBytes: Uint8List.fromList(<int>[10]),
+          ),
+        ),
+        sessionIdGenerator: () => nextSession++,
+      );
+
+      final first = await service.selectAndPrepareDfuV1();
+      final second = await service.selectAndPrepareDfuV1();
+
+      expect(first.firmware?.metadata.sessionId, 9);
+      expect(second.firmware?.metadata.sessionId, 10);
+    });
+
+    test('maps picker read failure to explicit validation error', () async {
+      final service = FirmwareFileSelectionService(
+        filePicker: _FakeFirmwareFilePicker(
+          selection: null,
+          error: const FormatException('broken pick payload'),
+        ),
+      );
+
+      final result = await service.selectAndPrepareDfuV1();
+
+      expect(result.isSuccess, isFalse);
+      expect(result.failure?.reason, FirmwareSelectionFailureReason.readFailed);
+      expect(result.failure?.message, contains('broken pick payload'));
+    });
+  });
+}
+
+class _FakeFirmwareFilePicker implements FirmwareFilePicker {
+  _FakeFirmwareFilePicker({
+    required this.selection,
+    this.error,
+  });
+
+  final FirmwarePickerSelection? selection;
+  final Object? error;
+
+  @override
+  Future<FirmwarePickerSelection?> pickFirmwareFile() async {
+    if (error != null) {
+      throw error!;
+    }
+    return selection;
+  }
+}
--- a/test/service/firmware_update_service_test.dart
+++ b/test/service/firmware_update_service_test.dart
@ -0,0 +1,350 @@
+import 'dart:async';
+
+import 'package:abawo_bt_app/model/shifter_types.dart';
+import 'package:abawo_bt_app/service/firmware_update_service.dart';
+import 'package:anyhow/anyhow.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('FirmwareUpdateService', () {
+    test('completes happy path with START, data frames, and FINISH', () async {
+      final transport = _FakeFirmwareUpdateTransport();
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultWindowSize: 4,
+        defaultAckTimeout: const Duration(milliseconds: 100),
+      );
+
+      final image = List<int>.generate(130, (index) => index & 0xFF);
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 7,
+      );
+
+      expect(result.isOk(), isTrue);
+      expect(transport.controlWrites.length, 2);
+      expect(
+          transport.controlWrites.first.first, universalShifterDfuOpcodeStart);
+      expect(transport.controlWrites.last, [universalShifterDfuOpcodeFinish]);
+      expect(transport.dataWrites.length, greaterThanOrEqualTo(3));
+      expect(
+        transport.postFinishSteps,
+        [
+          'waitForExpectedResetDisconnect',
+          'reconnectForVerification',
+          'verifyDeviceReachable',
+        ],
+      );
+      expect(service.currentProgress.state, DfuUpdateState.completed);
+      expect(service.currentProgress.sentBytes, image.length);
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('rewinds to ack+1 and retransmits after ACK stall', () async {
+      final transport = _FakeFirmwareUpdateTransport(dropFirstSequence: 1);
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultWindowSize: 3,
+        defaultAckTimeout: const Duration(milliseconds: 100),
+        maxNoProgressRetries: 4,
+      );
+
+      final image = List<int>.generate(190, (index) => index & 0xFF);
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 9,
+      );
+
+      expect(result.isOk(), isTrue);
+      expect(transport.dataWrites.length, greaterThan(4));
+      expect(transport.sequenceWriteCount(1), greaterThan(1));
+      expect(service.currentProgress.state, DfuUpdateState.completed);
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('cancel sends ABORT and reports aborted state', () async {
+      final firstFrameSent = Completer<void>();
+      final transport = _FakeFirmwareUpdateTransport(
+        onDataWrite: (frame) {
+          if (!firstFrameSent.isCompleted) {
+            firstFrameSent.complete();
+          }
+        },
+        suppressDataAcks: true,
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultWindowSize: 1,
+        defaultAckTimeout: const Duration(milliseconds: 500),
+      );
+
+      final future = service.startUpdate(
+        imageBytes: List<int>.generate(90, (index) => index & 0xFF),
+        sessionId: 11,
+      );
+
+      await firstFrameSent.future.timeout(const Duration(seconds: 1));
+      await service.cancelUpdate();
+      final result = await future;
+
+      expect(result.isErr(), isTrue);
+      expect(result.unwrapErr().toString(), contains('canceled'));
+      expect(transport.controlWrites.last, [universalShifterDfuOpcodeAbort]);
+      expect(service.currentProgress.state, DfuUpdateState.aborted);
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('fails when reconnect does not succeed after expected reset',
+        () async {
+      final transport = _FakeFirmwareUpdateTransport(
+        reconnectError: 'simulated reconnect timeout',
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultWindowSize: 4,
+        defaultAckTimeout: const Duration(milliseconds: 100),
+      );
+
+      final image = List<int>.generate(130, (index) => index & 0xFF);
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 13,
+      );
+
+      expect(result.isErr(), isTrue);
+      expect(result.unwrapErr().toString(), contains('did not reconnect'));
+      expect(service.currentProgress.state, DfuUpdateState.failed);
+      expect(
+        transport.postFinishSteps,
+        [
+          'waitForExpectedResetDisconnect',
+          'reconnectForVerification',
+        ],
+      );
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('fails when expected reset disconnect is not observed', () async {
+      final transport = _FakeFirmwareUpdateTransport(
+        resetDisconnectError: 'simulated missing disconnect',
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultWindowSize: 4,
+        defaultAckTimeout: const Duration(milliseconds: 100),
+      );
+
+      final image = List<int>.generate(130, (index) => index & 0xFF);
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 15,
+      );
+
+      expect(result.isErr(), isTrue);
+      expect(
+        result.unwrapErr().toString(),
+        contains('expected post-FINISH reset disconnect'),
+      );
+      expect(service.currentProgress.state, DfuUpdateState.failed);
+      expect(
+        transport.postFinishSteps,
+        ['waitForExpectedResetDisconnect'],
+      );
+
+      await service.dispose();
+      await transport.dispose();
+    });
+
+    test('fails when post-update status verification read fails', () async {
+      final transport = _FakeFirmwareUpdateTransport(
+        verificationError: 'simulated status read failure',
+      );
+      final service = FirmwareUpdateService(
+        transport: transport,
+        defaultWindowSize: 4,
+        defaultAckTimeout: const Duration(milliseconds: 100),
+      );
+
+      final image = List<int>.generate(130, (index) => index & 0xFF);
+      final result = await service.startUpdate(
+        imageBytes: image,
+        sessionId: 14,
+      );
+
+      expect(result.isErr(), isTrue);
+      expect(
+        result.unwrapErr().toString(),
+        contains('post-update verification failed'),
+      );
+      expect(
+        result.unwrapErr().toString(),
+        contains('does not expose a version characteristic'),
+      );
+      expect(service.currentProgress.state, DfuUpdateState.failed);
+      expect(
+        transport.postFinishSteps,
+        [
+          'waitForExpectedResetDisconnect',
+          'reconnectForVerification',
+          'verifyDeviceReachable',
+        ],
+      );
+
+      await service.dispose();
+      await transport.dispose();
+    });
+  });
+}
+
+class _FakeFirmwareUpdateTransport implements FirmwareUpdateTransport {
+  _FakeFirmwareUpdateTransport({
+    this.dropFirstSequence,
+    this.onDataWrite,
+    this.suppressDataAcks = false,
+    this.resetDisconnectError,
+    this.reconnectError,
+    this.verificationError,
+  });
+
+  final int? dropFirstSequence;
+  final void Function(List<int> frame)? onDataWrite;
+  final bool suppressDataAcks;
+  final String? resetDisconnectError;
+  final String? reconnectError;
+  final String? verificationError;
+
+  final StreamController<List<int>> _ackController =
+      StreamController<List<int>>.broadcast();
+
+  final List<List<int>> controlWrites = <List<int>>[];
+  final List<List<int>> dataWrites = <List<int>>[];
+  final List<String> postFinishSteps = <String>[];
+  final Set<int> _droppedOnce = <int>{};
+  int _lastAck = 0xFF;
+  int _expectedSequence = 0;
+
+  @override
+  Future<Result<DfuPreflightResult>> runPreflight({
+    required int requestedMtu,
+  }) async {
+    return Ok(
+      DfuPreflightResult.ready(
+        requestedMtu: requestedMtu,
+        negotiatedMtu: 128,
+      ),
+    );
+  }
+
+  @override
+  Stream<List<int>> subscribeToAck() => _ackController.stream;
+
+  @override
+  Future<Result<void>> writeControl(List<int> payload) async {
+    controlWrites.add(List<int>.from(payload, growable: false));
+
+    final opcode = payload.isEmpty ? -1 : payload.first;
+    if (opcode == universalShifterDfuOpcodeStart) {
+      _lastAck = 0xFF;
+      _expectedSequence = 0;
+      scheduleMicrotask(() {
+        _ackController.add([0xFF]);
+      });
+    }
+
+    if (opcode == universalShifterDfuOpcodeAbort) {
+      _lastAck = 0xFF;
+      _expectedSequence = 0;
+    }
+
+    return Ok(null);
+  }
+
+  @override
+  Future<Result<void>> writeDataFrame(List<int> frame) async {
+    dataWrites.add(List<int>.from(frame, growable: false));
+    onDataWrite?.call(frame);
+
+    if (suppressDataAcks) {
+      return Ok(null);
+    }
+
+    final sequence = frame.first;
+    final shouldDrop = dropFirstSequence != null &&
+        sequence == dropFirstSequence &&
+        !_droppedOnce.contains(sequence);
+
+    if (shouldDrop) {
+      _droppedOnce.add(sequence);
+      scheduleMicrotask(() {
+        _ackController.add([_lastAck]);
+      });
+      return Ok(null);
+    }
+
+    if (sequence == _expectedSequence) {
+      _lastAck = sequence;
+      _expectedSequence = (_expectedSequence + 1) & 0xFF;
+    }
+
+    scheduleMicrotask(() {
+      _ackController.add([_lastAck]);
+    });
+
+    return Ok(null);
+  }
+
+  @override
+  Future<Result<void>> waitForExpectedResetDisconnect({
+    required Duration timeout,
+  }) async {
+    postFinishSteps.add('waitForExpectedResetDisconnect');
+    if (resetDisconnectError != null) {
+      return bail(resetDisconnectError!);
+    }
+    return Ok(null);
+  }
+
+  @override
+  Future<Result<void>> reconnectForVerification({
+    required Duration timeout,
+  }) async {
+    postFinishSteps.add('reconnectForVerification');
+    if (reconnectError != null) {
+      return bail(reconnectError!);
+    }
+    return Ok(null);
+  }
+
+  @override
+  Future<Result<void>> verifyDeviceReachable({
+    required Duration timeout,
+  }) async {
+    postFinishSteps.add('verifyDeviceReachable');
+    if (verificationError != null) {
+      return bail(verificationError!);
+    }
+    return Ok(null);
+  }
+
+  int sequenceWriteCount(int sequence) {
+    var count = 0;
+    for (final frame in dataWrites) {
+      if (frame.first == sequence) {
+        count += 1;
+      }
+    }
+    return count;
+  }
+
+  Future<void> dispose() async {
+    await _ackController.close();
+  }
+}
Author	SHA1	Message	Date
Yandrik	2ac68e09ab	bd: backup 2026-03-04 17:07	2026-03-04 18:07:18 +01:00
Yandrik	1dbbf191e6	feat(dfu): add firmware update controls to device page	2026-03-04 18:07:12 +01:00
Yandrik	32f258a492	bd: backup 2026-03-03 16:11	2026-03-03 17:11:51 +01:00
Yandrik	c581b4d92c	feat(dfu): verify reconnect before reporting update success	2026-03-03 17:11:47 +01:00
Yandrik	aafa9928ac	feat(dfu): add firmware file selection and validation	2026-03-03 17:06:54 +01:00
Yandrik	8b24084f97	feat(dfu): add firmware transfer engine with ack retries	2026-03-03 17:00:37 +01:00
Yandrik	dd2afa34ef	bd: backup 2026-03-03 15:55	2026-03-03 16:55:11 +01:00
Yandrik	fb85565854	feat(dfu): add connection and MTU preflight checks	2026-03-03 16:54:56 +01:00
Yandrik	7a33e71410	feat(dfu): add packet codec and crc32 utilities	2026-03-03 16:48:49 +01:00
Yandrik	e704f27a96	feat(dfu): add protocol constants and progress models	2026-03-03 16:45:16 +01:00
Yandrik	08405c879b	fix(devices details page): style fixes	2026-03-03 16:41:43 +01:00
Yandrik	76c0fbe237	bd: backup 2026-03-03 15:37	2026-03-03 16:37:50 +01:00
Yandrik	d3a2fe6613	bd: backup 2026-03-03 15:20	2026-03-03 16:20:28 +01:00
Yandrik	a673aa14b7	bd init: initialize beads issue tracking	2026-03-03 16:15:18 +01:00
Yandrik	575ccaae42	feat: new shifter types and better gear ratio editor	2026-02-23 11:45:25 +01:00