fix(opencode): exit nonzero when run produces no assistant message

[iscekic]

Request

Surface: the CLI (packages/opencode).

kilo run exits 0 when the model returns no assistant message, so a caller cannot tell an empty run from a successful one. Reproduce first on a live CLI build: force a run that produces no assistant message and read its exit code. If it already exits non-zero, stop with the evidence and no code change. If it does not, exit non-zero with a clear stderr line, leave the exit code of a normal run unchanged, add a test beside the existing run tests, and show both exit codes in the PR body.

Changelog for users

• kilo run now exits non-zero when the model returns no assistant message, printing run ended without an assistant message; the model returned no output to stderr. Previously an empty run exited 0, indistinguishable from a successful run.
• A normal kilo run that produces assistant output still exits 0.

Changelog for maintainers

• The run command now records whether any assistant output arrived (a tool part, or a non-empty text/reasoning part that finished) and sets the exit code to 1 when a completed run produced none; under --format json it emits a final error record with the same message instead of stderr.
• A prompt-level request failure (result.error) keeps its own error as the only reported cause; the empty-output diagnostic is suppressed so a failed request does not also claim a silent model.
• Exit codes: empty run reproduced live exiting 0 → now exits 1; a normal run stays at 0.
• New subprocess tests beside the existing run subprocess tests cover the nonzero exit + stderr diagnostic, the JSON error record, and two request-failure cases that must not emit the empty-output diagnostic.
• Review: the empty-output check sits at the end of the run command's drain; the request-failure cases exercise an oversized attachment that triggers a BadRequest, and the empty-output diagnostic must stay absent there.

E2E proof

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• packages/opencode/src/cli/cmd/run.ts
• packages/opencode/test/cli/run/run-empty.process.test.ts

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_{Review guidance: REVIEW.md from base branch main}