Compaction failed: received empty response from model (3x retry, manual /compact on Opus 4.6)

[ronkeele]

Describe the bug

Running /compact manually in a short session (< 30 turns) on Claude Opus 4.6 produces three consecutive failures:

X Compaction Failed: Error: Compaction failed: received empty response from model
X Compaction Failed: Error: Compaction failed: received empty response from model
X Compaction Failed: Error: Compaction failed: received empty response from model

The session remained usable — after one additional turn (wasting a premium request), a subsequent /compact succeeded normally.

Affected version

1.0.34

Steps to reproduce the behavior

1. Start a session using Claude Opus 4.6.
2. Work through a task (commit pushed, environment reloaded mid-session — MCP servers, extensions, hooks, agents, skills all reloaded at the same time).
3. Run /compact manually.
4. Observe three consecutive Compaction failed: received empty response from model errors.

Expected behavior

/compact should succeed, or at minimum degrade gracefully (e.g., retry with a different summarization strategy rather than repeating the same failing call three times).

Additional context

• Model: Claude Opus 4.6
• Session length: Short (< 30 turns)
• Trigger: Manual /compact command
• Environment: Windows, VS Code Insiders connected, 2 custom instructions, 1 extension, 1 hook, 6 agents, 14 skills
• MCP servers: 0 connected at the time of failure (had just reloaded)
• Recovery: Session continued normally after one additional turn, then /compact worked — but this wasted a premium request on the recovery turn.

The environment reload (MCP Servers reloaded: 0 servers connected, mermaid-render extension loaded, Environment loaded: ...) occurred immediately before the compaction failures, which may be relevant — the compaction model may have received an unusual message history containing reload notifications.

Related issues

• Compaction killed the session #2500 — Compaction killed the session (different symptom but same area)
• CAPIError: 400 Unrecognized request argument 'reasoning_effort' when compacting after switching models #2553 — Compaction fails after model switching (different root cause)
• Toggle off for auto compaction!!!! #2333 — Request to toggle off auto-compaction (workaround request)