docs: mark PRD 0043 Active

Closes #140. In restart_daemon, the old process's stdout pipe was never
explicitly closed after p.wait() returned, leaking the fd until the
supervisor object was GC'd. Similarly, when the watch loop converged
(all children dead), no pipe was closed. Both paths now call
p.stdout.close() immediately after the process is confirmed exited.
Tests enforce this with warnings.simplefilter("error", ResourceWarning)
in TestSupervisor.setUp.

bot_bottle/sidecar_init.py

@@ -245,7 +245,12 @@ class _Supervisor:
                             except ProcessLookupError:
                                 pass
 
-        return all(p.poll() is not None for _, p in self.procs)
+        done = all(p.poll() is not None for _, p in self.procs)
+        if done:
+            for _, p in self.procs:
+                if p.stdout is not None:
+                    p.stdout.close()
+        return done
 
     def exit_code(self) -> int:
         """Positive child failures win; otherwise report success.
@@ -335,6 +340,8 @@ class _Supervisor:
                     except ProcessLookupError:
                         pass
                     p.wait()
+            if p.stdout is not None:
+                p.stdout.close()
             self._logged_dead.discard(daemon_name)
             new_proc = _spawn(spec)
             self.procs[idx] = (spec, new_proc)

docs/prds/0043-sidecar-pipe-lifecycle.md

@@ -0,0 +1,74 @@
+# 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.

tests/unit/test_sidecar_init.py

@@ -14,6 +14,7 @@ import subprocess
 import sys
 import time
 import unittest
+import warnings
 from pathlib import Path
 from unittest.mock import patch
 
@@ -135,6 +136,10 @@ class TestSupervisor(unittest.TestCase):
     We don't go through `main()` because main installs signal
     handlers process-wide, which collides with the test runner."""
 
+    def setUp(self):
+        warnings.simplefilter("error", ResourceWarning)
+        self.addCleanup(warnings.resetwarnings)
+
     def _drive(self, sup: _Supervisor, max_wait_s: float = 6.0) -> int:
         deadline = time.monotonic() + max_wait_s
         while not sup.tick():