PreCompact hook blocks indefinitely — no escape condition

[mjvmsteixeira]

hook_precompact() always returns {"decision": "block"} with no exit path,
causing /compact to be permanently blocked.

Fix: add session-level flag file (same pattern as Stop hook's stop_hook_active guard).
See: hooks_cli.py :: hook_stop() for reference implementation.

[mjvmsteixeira]

Version: mempalace 3.0.14, Claude Code

Steps to reproduce:

1. Run a long session until context fills
2. Run /compact
3. Claude saves to MemPalace via MCP tools
4. Run /compact again
5. Blocked again — repeats forever

Expected: After Claude saves, second /compact proceeds.
Actual: Every /compact call returns {"decision": "block"} regardless.

Root cause:
hook_precompact() in hooks_cli.py unconditionally returns block with no escape:

# Always block -- compaction = save everything
_output({"decision": "block", "reason": PRECOMPACT_BLOCK_REASON})

The Stop hook avoids this with:
if str(stop_hook_active).lower() in ("true", "1", "yes"):
    _output({})
    return
PreCompact has no equivalent guard.

Proposed fix:
Add a session-level flag file ~/.mempalace/hook_state/{session_id}_precompact_blocked.
First call: create flag + block. Second call: delete flag + allow.
This preserves the "always save before compact" intent while breaking the loop.

Workaround (local patch applied):
Patched hooks_cli.py locally with the flag file approach — verified working.

[mvalentsev]

Duplicate of #938 and #941. Fixed in #863 (merged 2026-04-15) -- precompact hook returns {} now instead of blocking.

Available on develop, not yet in a PyPI release. You're on 3.0.14 which predates the fix.

[LuigiEspinosa]

Hit this on 3.0.14 today, lost a session because auto-compact kept getting blocked. PR #863's return {} fix would have prevented that, would appreciate a PyPI release when the timing makes sense.

Side note on design: instead of waiting, I implemented the sentinel approach proposed in this issue's body (and in @mjvmsteixeira's comment) as a local patch. Per-session flag at ~/.mempalace/hook_state/{session_id}_precompact_acked. First /compact writes the sentinel and blocks with the save reminder, second /compact consumes the sentinel and returns {}. Verified block, {}, block across three back-to-back calls within the same session.

Compared to #863's "always allow" behavior, the sentinel keeps the save reminder firing once per session, which is the part of the original hook intent I personally found useful. Posting in case the tradeoff (always allow vs reminder-once) is worth a second look before the next release. No strong opinion, the return {} approach also unblocks the deadlock cleanly.