[patrykkopycinski]

Problem

A cursor-agent turn that decodes zero usable signal (no text, thinking, argumented tool call, or token delta — e.g. only a turn_ended frame) previously finalized into a clean 200 completion. The combo quality gate passes that fabricated empty-success shape, so clients received a successful-looking response with no content they could act on, instead of failing over to another hop.

Truncated tool calls make this worse: under load cursor can emit finish_reason: "tool_calls" with a bare tool name and arguments: ""; treating the bare name as signal let that empty turn finalize cleanly too.

Fix

• open-sse/executors/cursor.ts: add ctxProducedSignal(ctx) — a shared predicate for whether a StreamCtx saw usable content. A tool call only counts when it carried non-empty arguments. After driveH2 completes, the executor errors the stream (cursor-agent completed turn with no usable content) when no signal was produced, instead of calling finalizeSseStream.
• open-sse/services/combo/validateQuality.ts: the streaming peek loop now tracks whether any content/terminator was seen; a read error with no prior content is marked invalid so combo fails over, instead of passing through.

Tests

tests/unit/cursor-empty-turn-failover-v9.test.ts:

• RED: a ctx with only turn_ended reports no produced signal
• controls: text delta / token-delta-only turns do report signal
• chain: an executor-erroring empty stream now fails combo validation
• chain: a healthy stream with real content still passes validation

[diegosouzapw]

Thanks @patrykkopycinski — a Cursor turn that only ends with turn_ended, or a tool call whose arguments are blank, now fails over instead of a clean 200. The resume path sends tool results that the translator embedded as user-message XML, and the combo gate only treats Cursor's empty-turn and stream-timeout read errors as hop failures. That commit is on your branch, co-authored. This is in the upcoming release.