Loop doesn't exit after finish=stop — model re-invoked with no input until the session is quit

Description

When the agent finishes a turn with finish=stop and no tool calls, the session should go idle. Instead the loop keeps running and re-calls the model every ~10-20s with no new user message. The UI shows "busy" the whole time while the model just returns one-line filler ("Standing by", "Ready", "Idle").

From the logs:

• Normal cycles end with an exiting loop event. The stuck cycle never emits one — it runs loop step=0..28+ over ~25 minutes.
• The repeating pattern is loop step=N -> process (new message) -> stream (new model call), with nothing in between.
• Every filler message is finish=stop and its step-finish reason=stop, so the model is correctly signaling "done" and the loop is ignoring it.
• Esc fires cancel + error=Aborted (finish=None, 0 parts), then the loop restarts at step=0 and sticks again. Esc doesn't break it; only quitting the session does.

Also notable: the model's hidden reasoning in those filler turns literally says "I'm being repeatedly prompted with no user message — this is an artifact", so it's aware it's being re-called with nothing to do.

Version 1.17.18, model deepseek-v4-pro (opencode-go), Linux/WSL. Reproduced in one session, then again right after resuming it. Looks related to #42363 and #22329.

Plugins

No plugins

OpenCode version

1.17.18

Steps to reproduce

1. Run opencode (v1.17.18) with deepseek-v4-pro (opencode-go).
2. Do a normal multi-turn agent task — several tool calls, some reasoning, then a finish=stop (e.g. "implement X, run the tests, commit, summarize").
3. Let it reach a turn that ends with no tool calls. Instead of going idle, it keeps re-calling the model every ~10-20s with no new input — the UI stays "busy" and it appends one-line "Standing by" / "Ready" / "Idle" replies.
4. Press Esc: the current generation aborts, but the loop restarts at step=0 and sticks again.
5. Only quitting the session (Ctrl+C) stops it.
   Note: not fully deterministic — I only hit it after long sessions with a lot of reasoning/tool history, so it may depend on context length.

Screenshot and/or share link

Recreated using sql db trace by ds4 pro

Operating System

WSL on Windows 11

Terminal

westerm