# PRD 0043: Sidecar Pipe Lifecycle Cleanup

- **Status:** Active
- **Author:** didericis-codex
- **Created:** 2026-06-02
- **Issue:** #140

## Summary

Close the unclosed child stdout pipe file descriptors that `sidecar_init.py`
leaks during restart and shutdown paths, eliminating `ResourceWarning` noise
and tightening the process lifecycle.

## Problem

Unit tests for `sidecar_init.py` pass, but restart and shutdown cases emit
`ResourceWarning: unclosed file <_io.BufferedReader …>` for child stdout pipes,
originating around lines 141 and 273. The warnings indicate the restart path
leaks pipe file descriptors: a pipe opened for a stopped or replaced child is
not explicitly closed before the next child is spawned or before the supervisor
exits.

## Goals / Success Criteria

- `python3 -m unittest tests.unit.test_sidecar_init` produces no
  `ResourceWarning` output.
- Pipe file descriptors for stopped or replaced child processes are explicitly
  closed in the restart path.
- Pipe file descriptors for all children are explicitly closed in the shutdown
  path.
- No change to the external signal or exit-code contract from PRD 0034.

## Non-goals

- No changes to restart or shutdown policy (coalescing, ordering, timeout).
- No changes to egress, pipelock, git-gate, or supervise daemon argv.
- No new runtime dependencies.

## Scope

In scope:

- `bot_bottle/sidecar_init.py` pipe open/close lifecycle in `_Supervisor`.
- Unit tests in `tests/unit/test_sidecar_init.py` asserting no leaked pipes.

Out of scope:

- Changing how pumping threads read from pipes.
- Integration tests that start a live sidecar container.

## Design

Audit every code path in `_Supervisor` where a child process is stopped,
replaced, or reaches end-of-life, and ensure the corresponding stdout pipe is
explicitly closed before spawning a replacement or exiting the supervisor loop.

Where a pumping thread holds a reference to the pipe, coordinate closure so the
thread sees EOF and exits cleanly rather than blocking indefinitely.

## Testing Strategy

- Enable `ResourceWarning` as an error in test setUp:
  `warnings.simplefilter("error", ResourceWarning)`.
- Run existing restart and shutdown test cases under this stricter setting.
- Add tests for restart-then-shutdown if not already covered.

Run:

- `python3 -m unittest tests.unit.test_sidecar_init`
- `python3 -m unittest discover -s tests/unit`

## Open Questions

None.