Pi-backed Guided Review masks insufficient-credits errors as guide parse failures

[alexanderkreidich]

Summary

When a Pi-backed Guided Review uses an API model whose account has no remaining credits, the provider error is not surfaced. Instead, Plannotator reports a misleading guide parsing failure:

[guide] Failed to parse output for job c5fa951f-1e32-4585-986a-67cd462960df

The same behavior was observed previously with job 49318521-4030-425d-8c60-c8d15499eb4e.

Reproduction

1. Configure an API-backed Pi model on an account with no remaining API credits.
2. Open a pull request using /plannotator-review.
3. Open Guided Review.
4. Select the Pi engine and the no-credits API model.
5. Generate the guide.

Tested with:

• @plannotator/pi-extension 0.22.0
• Pi 0.80.6
• Guide engine: Pi
• Model: codex-proxy/openai/gpt-5.5
• Thinking: medium

Actual behavior

The provider rejects the request because the account has no credits, but the visible/logged failure is:

[guide] Failed to parse output for job <uuid>

The underlying insufficient-credits error is lost, and the failure appears to be malformed guide JSON.

Expected behavior

The job should fail with the original provider error, for example:

Insufficient API credits

Plannotator should not attempt to parse guide JSON after the underlying agent run has already failed.

Technical diagnosis

The relevant flow appears to be:

1. Pi is launched in JSON mode by the marker-engine integration.
2. pi --mode json can exit with code 0 even when the agent run itself errors or is aborted. This behavior is already documented in piBuildArgv() in packages/server/marker-review.ts.
3. Because the process exit code is 0, the agent-job handler invokes Guided Review result ingestion.
4. The failed agent produced no complete nonce-delimited guide JSON block.
5. parseGuideMarkerOutput() returns null, and createGuideSession().onJobComplete() logs the generic parsing failure.

A normal replay using the same Pi/model configuration successfully produced a valid marker block, so this is error propagation for the no-credits path rather than a general Pi/Guide parser incompatibility.

Suggested regression coverage

Add a Pi NDJSON fixture where:

• the process exit code is 0;
• the assistant/provider event contains an error or error stop reason;
• no marker-delimited output exists.

Assert that the job surfaces the provider error and does not report Failed to parse output. The same handling may be relevant to Pi-backed code review jobs in addition to Guided Review.