What happened?

While investigating #4815, we verified that microcompactHistory() only runs inside the UserQuery / Cron branch in packages/core/src/core/client.ts.

/goal uses Stop-hook continuations that recursively call sendMessageStream() with SendMessageType.Hook. Those Hook turns bypass the microcompaction branch, so a long-running /goal loop can keep accumulating old tool result contents until a later UserQuery or Cron turn happens.

Relevant flow:

• microcompactHistory() runs only when messageType === SendMessageType.UserQuery || messageType === SendMessageType.Cron.
• Stop-hook continuation calls sendMessageStream(..., { type: SendMessageType.Hook, ... }).
• Current memory-pressure cleanup only evicts/clears file cache and optional GC; it does not compact chat history.

Expected behavior

Hook continuations that can drive long-running autonomous work, especially /goal, should still give old tool results a cleanup point without waiting for a future user/cron turn.

Suggested fix direction

Keep the fix narrow: reuse the existing microcompaction logic for SendMessageType.Hook turns, while continuing to avoid ToolResult turns so functionCall/functionResponse pairing is not disturbed.

Add a focused regression test that builds old read_file tool results, sets lastApiCompletionTimestamp beyond the idle threshold, runs a Hook turn, and verifies history is compacted.

Related

Follow-up from #4815.