fix: suppress quota banner after successful stream

[Nomadcxx]

Small fix for the false quota banner we saw with Composer 2.5 Fast.

What changed:

• track whether streaming has already produced useful assistant output or a successful result
• if cursor-agent exits non-zero with quota text after that, log it as diagnostic instead of appending a second assistant error chunk
• keep the existing hard-error path when no successful streamed output was seen
• add an integration regression where the mock streams an answer, writes quota text to stderr, and exits 1

Test plan:

• npm test -- tests/integration/opencode-loop.integration.test.ts
• npm test -- tests/unit/errors.test.ts tests/unit/streaming/openai-sse.test.ts
• npm run verify:issue-92
• npm test

[coderabbitai]

Caution

Review failed

The pull request is closed.

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Reviewing files that changed from the base of the PR and between d2cee4e and 6a1cc76.

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• tests/integration/opencode-loop.integration.test.ts

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📝 Walkthrough

Walkthrough

The plugin introduces a sawSuccessfulStreamOutput boolean in both Bun and Node streaming paths, set when successful result events or assistant/thinking SSE chunks are observed. On non-zero cursor-agent exit, a new shouldTreatCursorAgentFailureAsDiagnostic predicate (quota type + saw output) gates whether eviction and error-chunk emission are skipped. A matching integration test and mock scenario validate this silent-passthrough behavior.

Changes

Quota-exit diagnostic passthrough

Layer / File(s)	Summary
Helper predicates for quota diagnostic detection src/plugin.ts	Adds isSuccessfulResultEvent and shouldTreatCursorAgentFailureAsDiagnostic local helpers; the latter checks parseAgentError(errSource).type === "quota" and requires sawSuccessfulStreamOutput to be true.
Bun streaming: sawSuccessfulStreamOutput tracking src/plugin.ts	Declares the flag at Bun streaming scope and sets it on successful result events in the main loop, on assistant/thinking SSE chunks during live streaming, and again during flush/remainder processing.
Bun non-zero exit: conditional diagnostic skip src/plugin.ts	Replaces the unconditional eviction + error-chunk path with a conditional branch: quota failures after successful output log a warning and return early; all other failures follow the existing maybeEvictResumeChatId + error-chunk path.
Node streaming: sawSuccessfulStreamOutput tracking src/plugin.ts	Mirrors the Bun tracking pattern for the Node path: declares the flag and sets it in the Node streaming loop and SSE conversion path.
Node non-zero exit: conditional diagnostic skip src/plugin.ts	Applies the same quota diagnostic skip to the Node non-zero exit handler.
Mock scenario and integration test tests/integration/opencode-loop.integration.test.ts	Adds the assistant-text-quota-exit mock branch (stderr "Cursor usage limit", exit 1) and an integration test asserting no quota/error text in assembled output and a [DONE]-terminated SSE stream.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• Nomadcxx/opencode-cursor#99: Introduces the session-resume and pool plumbing in src/plugin.ts that this PR's non-zero exit handling and resume-chat-id eviction logic directly builds on.
• Nomadcxx/opencode-cursor#100: Hardens which cursor-agent failures should evict the cached resume chat id, the same code path this PR further modifies by gating eviction on the quota diagnostic predicate.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: suppressing quota banners after successful streaming, which matches the core fix implemented in the changeset.
Description check	✅ Passed	The description is directly related to the changeset, explaining the quota banner fix, the tracking mechanism, conditional error handling, and the regression test added.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@tests/integration/opencode-loop.integration.test.ts`:
- Around line 220-223: In the mock for the "assistant-text-quota-exit" scenario,
replace the immediate process.exit(1) call with setting process.exitCode to 1
and then returning. This allows any buffered stderr output from the
process.stderr.write call to be properly flushed before the process terminates,
preventing nondeterministic test failures caused by incomplete stream writes.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

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📥 Commits

Reviewing files that changed from the base of the PR and between c7b08c1 and d2cee4e.

📒 Files selected for processing (2)

• src/plugin.ts
• tests/integration/opencode-loop.integration.test.ts