---
phase: 02-telegram-integration
plan: 01
subsystem: infra
tags: [asyncio, subprocess, python, claude-code-cli, stream-json, telegram, markdown, typing-indicator]

# Dependency graph
requires:
  - phase: 01-session-process-foundation
    provides: Session management and subprocess foundations
provides:
  - Persistent Claude Code subprocess with stream-json I/O (eliminates ~1s spawn overhead per turn)
  - Tool call progress notifications via on_tool_use callback
  - Smart message splitting respecting MarkdownV2 code block boundaries
  - MarkdownV2 escaping with code block awareness
  - Typing indicator loop for long operations
affects: [02-02, bot-integration, message-handling]

# Tech tracking
tech-stack:
  added:
    - telegram.constants.ChatAction (typing indicators)
  patterns:
    - "Persistent subprocess with NDJSON stdin streaming"
    - "Stream-json event routing including tool_use events"
    - "Smart message splitting at code block boundaries"
    - "Context-sensitive MarkdownV2 escaping (preserves code blocks)"
    - "Typing indicator loop with asyncio.Event cancellation"

key-files:
  created:
    - telegram/telegram_utils.py
  modified:
    - telegram/claude_subprocess.py

key-decisions:
  - "Use persistent subprocess instead of fresh process per turn (eliminates ~1s overhead)"
  - "Write NDJSON to stdin with drain() to prevent pipe buffer deadlock"
  - "Persistent readers run for process lifetime, result events mark not busy but don't exit loop"
  - "Parse content_block_start events for tool_use to enable progress notifications"
  - "Split messages at 4000 chars (not 4096) to leave room for escape character expansion"
  - "Never split inside code blocks (track in_code_block state while iterating lines)"
  - "Escape MarkdownV2 special chars only outside code blocks (regex pattern to identify code regions)"

patterns-established:
  - "Pattern 1: Persistent stdin streaming - start() spawns process, send_message() writes NDJSON, readers run until process dies"
  - "Pattern 2: Tool use notifications - Parse content_block_start with type=tool_use, extract name and input dict, pass to callback"
  - "Pattern 3: Smart message splitting - Track code block state, split only when NOT in code block and would exceed limit"
  - "Pattern 4: Code-aware escaping - Split by code regions (regex), escape only non-code text, rejoin"
  - "Pattern 5: Typing loop - Re-send every 4s via asyncio.wait_for timeout until Event is set"

# Metrics
duration: 5min
completed: 2026-02-04
---

# Phase 2 Plan 1: Persistent Subprocess + Telegram Utils Summary

**Persistent Claude Code subprocess with stream-json I/O and Telegram message formatting utilities for bot integration**

## Performance

- **Duration:** 5 minutes
- **Started:** 2026-02-04T19:12:28Z
- **Completed:** 2026-02-04T19:17:24Z
- **Tasks:** 2
- **Files created:** 1
- **Files modified:** 1

## Accomplishments

- Refactored ClaudeSubprocess from fresh-process-per-turn to persistent process model
- Eliminated ~1s spawn overhead per message turn
- Added stream-json stdin I/O for NDJSON message delivery to persistent process
- Implemented tool_use event parsing and on_tool_use callback for progress notifications
- Created telegram_utils.py with smart message splitting, MarkdownV2 escaping, and typing indicator loop
- Smart splitting respects code block boundaries (never splits inside triple-backtick blocks)
- MarkdownV2 escaping preserves code blocks while escaping 17 special characters outside code
- Typing indicator loop re-sends every 4 seconds with clean asyncio.Event cancellation

## Task Commits

Each task was committed atomically:

1. **Task 1: Refactor ClaudeSubprocess to persistent process** - `6a115a4` (refactor)
2. **Task 2: Create telegram_utils.py** - `6b624d7` (feat)

## Files Created/Modified

**Created:**
- `telegram/telegram_utils.py` - Message formatting utilities: split_message_smart (code-block-aware splitting), escape_markdown_v2 (context-sensitive escaping), typing_indicator_loop (4s re-send pattern)

**Modified:**
- `telegram/claude_subprocess.py` - Refactored to persistent subprocess with --input-format stream-json stdin, persistent stdout/stderr readers, tool_use event parsing, NDJSON message delivery via stdin.write + drain pattern

## Decisions Made

1. **Persistent process architecture**: Spawn Claude Code once with stream-json I/O, write NDJSON to stdin for each turn. Eliminates ~1s spawn overhead per message and maintains conversation context across turns.

2. **Tool use callback design**: Extract tool name and raw input dict from content_block_start events, pass directly to callback. Bot layer (Plan 02) will format human-readable progress messages. Keeps subprocess layer format-agnostic.

3. **Smart splitting strategy**: Track code block state (in/out of triple backticks), split only when NOT in code block and would exceed 4000 char limit. If code block itself exceeds limit, include it whole (Telegram handles overflow).

4. **Escape only outside code**: Use regex to identify code regions (```...``` and `...`), escape MarkdownV2 special chars only in non-code text. Prevents breaking code syntax while properly escaping user-facing text.

5. **4000 char split threshold**: Use 4000 instead of Telegram's 4096 limit to leave room for MarkdownV2 escape character expansion (each special char becomes 2 chars with backslash).

6. **Typing loop cancellation pattern**: Use asyncio.wait_for with 4s timeout on Event.wait(). Clean cancellation when Event is set, automatic re-send on timeout. Pattern from PTB community best practices.

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

**Issue 1: ChatAction import path**
- **Problem:** Initial import `from telegram import ChatAction` failed with ImportError
- **Root cause:** python-telegram-bot v22+ moved ChatAction to telegram.constants
- **Resolution:** Changed to `from telegram.constants import ChatAction`
- **Impact:** Minor, caught during testing, fixed immediately

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

**Ready for Plan 02 (Bot Integration):**
- ClaudeSubprocess provides persistent process with tool call notifications
- telegram_utils provides all message formatting needed for bot layer
- Smart splitting and escaping handle Claude's output for Telegram delivery
- Typing indicator loop ready for integration with message handlers
- stdin.write + drain pattern ensures no pipe deadlock

**Integration points for Plan 02:**
- Call `subprocess.start()` once per session
- Pass `on_tool_use` callback to format and send progress messages
- Use `split_message_smart()` on Claude output before sending to Telegram
- Use `escape_markdown_v2()` if sending with MarkdownV2 parse mode
- Wrap `subprocess.send_message()` with `typing_indicator_loop()` background task
- Handle file uploads by saving to session directory
- Implement message batching with debounce timer

**No blockers or concerns.**

---
*Phase: 02-telegram-integration*
*Completed: 2026-02-04*