fix(cli): return a typed 422 for commit-message with no changes

[marius-kilocode]

When generating a commit message with nothing to commit (nothing staged, or only lock files which are filtered out), the user saw a generic Unexpected server error. Check server logs for details. (HTTP 500) instead of a clear, actionable message.

Why

generate.ts throws a plain Error("No changes found to generate a commit message for"). The HTTP handler wraps it via EffectBridge.fromPromise, but Effect maps unhandled promise rejections to Dies, so the plain error becomes an untyped defect. The error middleware treats untyped defects as 500 and masks the message, leaving the user with no idea why generation failed.

The correct pattern for this API surface is to declare an explicit Schema.ErrorClass on the endpoint and fail with that typed error so it surfaces as a real HTTP status with the actual message.

What changed

• Declare CommitMessageNoChangesError (Schema.ErrorClass, httpApiStatus: 422, { message }) on the commit-message endpoint error contract alongside the existing HttpApiError.BadRequest.
• Replace the plain Error in generate.ts with a recognizable NoChangesError domain class, so the handler can distinguish it from unexpected defects.
• In the handler, keep EffectBridge.fromPromise (preserves Kilo instance/workspace contexts across the callback) and add Effect.catchDefect to translate the NoChangesError defect into the typed CommitMessageNoChangesError failure (422). Unexpected defects are re-died so they still surface as masked 500s, which is correct for truly unexpected errors.
• The VS Code extension shows the real message directly instead of prepending a redundant Failed to generate commit message: prefix that doubled up the wording.
• Regenerated the SDK so CommitMessageNoChangesError and the 422 status are part of the typed client contract.

All changes are in Kilo-owned paths (packages/opencode/src/kilocode/, packages/kilo-vscode/); no shared upstream files were touched.

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	1
SUGGESTION	0

Issue Details (click to expand)

WARNING

File	Line	Issue
packages/opencode/src/kilocode/server/httpapi/handlers/commit-message.ts	26	Expected "no changes" failure is modeled as a defect and caught with Effect.catchDefect, which specs/effect/errors.md explicitly says not to do for expected failures

Files Reviewed (9 files)

• .changeset/commit-message-no-changes-error.md
• packages/kilo-vscode/src/services/commit-message/index.ts
• packages/opencode/src/kilocode/commit-message/generate.ts
• packages/opencode/src/kilocode/commit-message/index.ts
• packages/opencode/src/kilocode/server/httpapi/groups/commit-message.ts - 0 issues
• packages/opencode/src/kilocode/server/httpapi/handlers/commit-message.ts - 1 issue
• packages/opencode/test/kilocode/commit-message/generate.test.ts
• packages/opencode/test/kilocode/server/commit-message-no-changes.test.ts
• packages/opencode/test/kilocode/server/httpapi-exercise-scenarios.ts

Note: packages/sdk/js/src/v2/gen/types.gen.ts is a generated SDK file; its unrelated sandbox_writable_paths addition is SDK regen drift, not reviewed per repo policy.

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_{Reviewed by claude-sonnet-5-20260630 · Input: 44 · Output: 14.1K · Cached: 1.7M}

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