[ranxianglei]

What

Fixes #732 — "AUTO model sometime stop".

A reasoning model can end a turn with only a thinking block (zero visible text, zero tool calls, status completed) — most often right after a post-compress re-request, where it sees the freshly-shrunk context and "wraps up" into a silent thought. The client then receives an empty completed turn and stalls until manually nudged.

Root cause (verified)

The user's log line at 14:43:32.513Z is the stop:

[degenerate-turn] responses: turn ended completed with zero visible text and zero tool calls (thinking present; no visible text emitted) … (#673)

• Round 1 the model issued compress; bili executed it server-side and re-requested (round 2).
• Round 2 deepseek-flash returned a reasoning-only completed turn → empty turn forwarded → agent stalled until the next request (14:46:30).
• The second timestamp in the issue, 14:44:08.791Z, is an unrelated routine npm auto-update check.

#673 (#674) shipped only the [degenerate-turn] detector, described as "the groundwork for auto-retry" — the retry itself was never implemented. (The existing #371 fake-completion backstop detects a different shape, is opt-in/off by default, and only guards the first fetch, not loop rounds 2+.)

Fix

In src/loop/core.ts (runCompressLoop), after a round completes with nothing forwarded to the client yet (forwardedAny === false — true for these rounds on wires whose round>1 framing is suppressed, e.g. Responses) and the turn is a genuine silent thought, re-fetch once with an ephemeral continuation nudge. The nudge is appended only to the retry body — never committed to coreMessages/session state, so it is neither persisted nor replayed.

Guard rails:

• One-shot per request (degenerateRetried).
• Requires sawThinking — surfaced on the done stream event by all three adapters — so a legitimately empty/no-reasoning terminal turn is left untouched. Only the "silent thought" shape retries.
• Excludes truncated/suppressed/error terminals (those are handled by 启动横幅硬编码 raw-HTTP-capture(on) 而真开关是 ACP_DUMP_BODY(默认关):日志永远撒谎,取证被带偏过 #413 truncation-retry or pass through).
• On retry failure, logs and passes the empty turn through (no worse than today).

Scoped to proxy mode automatically (the compress loop doesn't run in plugin mode).

Pre-flight

• npm run typecheck ✅
• npm test ✅ 1431 pass / 0 fail / 2 skipped (incl. new tests/loop-degenerate-retry.test.ts: D1 one invisible retry w/ nudge, D2 one-shot bound)
• npm run build ✅ (dist self-contained)

[github-actions]

📦 Built Package Artifact

Branch: 2026-09-12_auto-mode-degenerate-turn (22c609c)

Option A — Install from npm PR tag (recommended)

npm install -g billion-context@pr-734

Each push to this PR publishes a new version under the pr-734 npm tag.

Option B — Download artifact

1. Download the artifact from the Actions run
2. Extract the tarball and install:

tar xzf billion-context-pr734.tgz
npm install -g package

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This comment is automatically updated on each push.