Auto-compaction infinite loop when assistant ended its turn (finish !== tool-calls)

[Lee-SiHyeon]

Bug Description

When auto-compaction triggers after the assistant has naturally ended its turn (e.g., asked a question via the question tool, or simply finished responding with finish === "stop"), SessionCompaction.process() unconditionally injects a synthetic "Continue..." user message, creating an infinite loop.

Steps to Reproduce

1. Start a long conversation that approaches the context window limit
2. Have the assistant end its turn naturally (ask a question, or finish responding)
3. Auto-compaction triggers due to context overflow
4. Synthetic "Continue if you have next steps..." message is injected
5. Agent responds to the synthetic continue → context overflows again → compaction → synthetic continue → ...

Expected Behavior

When the assistant had naturally ended its turn (finish === "stop"), the compaction should complete without injecting a synthetic continue message. The session loop should exit and wait for real user input.

The synthetic continue should only be injected when the assistant was in the middle of tool execution (finish === "tool-calls" or "unknown").

Actual Behavior

The synthetic continue is always injected during auto-compaction, regardless of the assistant's state. This causes an unbounded loop:

assistant responds → context overflow → auto-compaction → synthetic "Continue..." →
agent responds → overflow → compaction → synthetic "Continue..." → …

Root Cause

In packages/opencode/src/session/compaction.ts, the process() function (line ~202) checks result === "continue" && input.auto but does not check the assistant's finish reason before injecting the synthetic continue.

Environment

• OpenCode v1.2.15
• Observed with oh-my-opencode plugin (Sisyphus/Ultraworker agent)
• Model: Claude Sonnet 4

Related

• feat(session): add custom compaction thresholds along with prevention of continuous compaction #10123 — addresses continuous compaction with min_messages threshold (different approach)
• fix: auto-resume agent loop after context compaction #12970 — addresses the opposite problem (continue NOT being injected when it should be)
• fix: compaction bugs #13946 and #13980 #14245 — fixes other compaction bugs in headless mode

[github-actions]

This issue might be a duplicate of or closely related to existing issues. Please check:

• Session Loop Termination Condition Fails Causing Infinite Loop #13577: Session Loop Termination Condition Fails Causing Infinite Loop — same symptom (infinite loop when finish=stop), different root cause (string ID comparison in loop termination logic)
• Session loop doesn't stop when model returns finish_reason=stop #11153: Session loop doesn't stop when model returns finish_reason=stop — same symptom, root cause traced to processor.ts returning "continue" when it should return "stop"

These issues share the same observable behavior but differ in where the fix should be applied. It may be worth coordinating with the assignees of those issues to ensure the fixes are complementary.

[Lee-SiHyeon]

I did local build and It is fixed when I use my local binary.

[aeciolevy]

I was seeing the same.

It’s an infinite loop. For me, this mostly happened with Claude Opus through GitHub Copilot.

After digging further, it looked like an MCP handshake with hundreds of definitions was triggering it.

Just reduced the access to the MCPs tool I was using, and it stopped.