---
phase: 38-telegram-bridge
plan: "02"
subsystem: api
tags: [telegram, grammy, voice, whisper, piper, ogg, ffmpeg, tts, stt]

requires:
  - phase: 38-01
    provides: telegramService factory with text relay, session map, bot lifecycle
  - phase: 36-voice-pipeline
    provides: voicePipelineService (transcribe, synthesize, formatForVoice, transcodeToWav16k)

provides:
  - Voice message handler: OGG download via ctx.getFile(), transcription via voicePipelineService
  - Shared relayToAgent() function used by both text and voice message handlers
  - transcodeToOggOpus() helper: raw PCM s16le (Piper 22050Hz) -> OGG Opus 48000Hz for Telegram
  - TTS voice reply: agent responses synthesized to OGG voice note via ctx.replyWithVoice()
  - Graceful TTS degradation: text reply always sent first; voice is a bonus that silently fails

affects:
  - 38-03 (onboarding step unchanged — already uses POST /telegram/token)

tech-stack:
  added: []
  patterns:
    - "Immediate 'Transcribing...' reply prevents Telegram update resend (Pitfall 1)"
    - "Fire-and-forget async: processVoiceMessage() not awaited inside handler body"
    - "Shared relayToAgent(ctx, chatId, userText, db, voiceMode) eliminates duplicate relay logic"
    - "TTS reply wrapped in try/catch — voice failure never blocks text response"
    - "transcodeToOggOpus uses same ffmpeg spawn pattern as voice-pipeline.ts"

key-files:
  created: []
  modified:
    - server/src/services/telegram.ts

key-decisions:
  - "Both tasks implemented together in one atomic file write — Task 1 (voice handler + relay refactor) and Task 2 (TTS reply) both modify telegram.ts; committing as one coherent change"
  - "processVoiceMessage() extracted as top-level async function — keeps bot handler clean and makes error handling explicit"
  - "voiceMode flag passed to relayToAgent() rather than checking ctx type — simpler and avoids grammy type gymnastics"
  - "botToken stored as module-level mutable ref (botToken = token) in start() — processVoiceMessage needs token for CDN URL construction"
  - "Piper hardcoded to 22050Hz in transcodeToOggOpus with comment — matches en_US-lessac-medium model spec"

metrics:
  duration: 10min
  completed: 2026-04-04
  tasks_completed: 2
  tasks_total: 2
  files_modified: 1
---

# Phase 38 Plan 02: Telegram Voice Handling Summary

**OGG download + Whisper transcription + Piper TTS reply wired into existing telegramService, with shared relayToAgent() function and graceful voice degradation**

## Performance

- **Duration:** ~10 min
- **Completed:** 2026-04-04
- **Tasks:** 2 of 2
- **Files modified:** 1

## Accomplishments

- Refactored text relay into shared `relayToAgent(ctx, chatId, userText, db, voiceMode)` — eliminates duplicate logic between text and voice handlers
- Added `bot.on("message:voice", ...)` handler that sends immediate "Transcribing..." reply (prevents Telegram resend) and processes async
- `processVoiceMessage()`: downloads OGG from Telegram CDN via `ctx.getFile()` + fetch, transcribes via `voicePipelineService().transcribe(oggBuffer, "ogg")`, sends "Heard: ..." confirmation, relays to agent
- `transcodeToOggOpus()`: uses ffmpeg-static spawn pattern to convert raw PCM s16le (Piper 22050Hz) to OGG Opus 48000Hz for Telegram voice notes
- TTS voice reply: after text reply, calls `voiceSvc.formatForVoice()` + `synthesize()` + `transcodeToOggOpus()` + `ctx.replyWithVoice(InputFile(...))` — wrapped in try/catch so Piper unavailability degrades silently

## Task Commits

1. **Task 1 + Task 2: Voice handler + TTS reply** - `e7205724` (feat) — both tasks in single atomic commit (same file)

## Files Created/Modified

- `server/src/services/telegram.ts` (322 lines, was 187) — voice handler, relayToAgent(), transcodeToOggOpus(), TTS reply

## Decisions Made

- `botToken` stored as module-level mutable ref alongside `bot` — processVoiceMessage() needs token string to construct the Telegram CDN download URL
- `voiceMode = false` default parameter on `relayToAgent()` — text handler calls without flag, voice handler passes `true`
- TTS failure is a warning (not an error) — voice reply is bonus feature, text always delivered first
- `transcodeToOggOpus` hardcodes 22050Hz input rate with explanatory comment — matches Piper `en_US-lessac-medium` output spec

## Deviations from Plan

### Minor adjustments

**1. [Rule 1 - Structural] Tasks 1 and 2 implemented and committed together**
- **Found during:** Task 1 planning
- **Issue:** Both tasks modify the same file; splitting into two commits would require an intermediate state where voice handler exists without TTS, which is not a meaningful checkpoint
- **Fix:** Single commit covers both tasks; commit message documents both additions
- **Files modified:** server/src/services/telegram.ts
- **Commit:** e7205724

## Known Stubs

None — voice relay is fully wired:
- OGG download: real Telegram CDN fetch via `ctx.getFile()`
- Transcription: real `voicePipelineService().transcribe()` (Whisper)
- TTS synthesis: real `voicePipelineService().synthesize()` (Piper)
- Voice reply: real `ctx.replyWithVoice(InputFile(oggBuffer))`
- Text relay: real `puterProxyService().chatStream()` (same as Plan 01)

The only runtime dependency is Whisper/Piper availability — both degrade gracefully with informative error messages.

## Self-Check: PASSED

- File exists: server/src/services/telegram.ts (322 lines) ✓
- Commit e7205724 exists ✓
- All acceptance criteria passing ✓
