fix: restore runnerRoundTrips agent-cost field dropped in #968

[thymikee]

Regression

PR #968 (apple-platform-consolidation, merge 26ac865c6) accidentally removed the runnerRoundTrips field from the agent-cost block — a shipped Phase-4 feature. The removal was an over-broad conflict resolution: the merge intended to keep main's round-trip wiring, but it got dropped. The commit message is just "refactor: consolidate Apple platform internals" with no mention of dropping the feature, and the cost graft's call site still carries the comment "Runs inside the diagnostics scope so cost can read this request's runner-round-trip tally" — i.e. the intent was preserved while the implementation was lost.

On the regressed main, runnerRoundTrips appeared nowhere in src/: ResponseCost had only wallClockMs + optional nodeCount, and the request-router cost graft only set wallClockMs.

What was restored

• src/kernel/contracts.ts — re-add ResponseCost.runnerRoundTrips: number (always present when cost is included; 0 when no runner was hit).
• src/utils/diagnostics.ts — restore the countDiagnosticEventsByPhase() accessor over the flush-surviving phaseCounts tally. The tally mechanism itself (phaseCounts map on the diagnostics scope, populated in emitDiagnostic) survived refactor: consolidate Apple platform internals #968; only the public accessor was removed, so this re-adds just the accessor.
• src/daemon/request-router.ts — repopulate runnerRoundTrips in buildResponseCost by counting the two real round-trip diagnostic phases (ios_runner_command_send + ios_runner_readiness_preflight). The graft already runs inside the request's diagnostics scope, so it reads the per-request tally. The RUNNER_ROUND_TRIP_PHASES constant is now defined locally in this file: its former home, the dev-only runner-request-count.ts CI gate, was removed in refactor: consolidate Apple platform internals #968 and is intentionally out of scope to restore (a separate maintainer decision).
• src/daemon/__tests__/request-router-cost.test.ts — restore the runnerRoundTrips: 0 assertion in the additive-only test and re-add the round-trip counting test (1 preflight + 2 command_send = 3, excluding _skipped/unrelated phases).

Out of scope (intentionally not restored)

The dev-only ndjson gate deleted by #968 (scripts/runner-request-count/, src/daemon/runner-request-count.ts) — a separate maintainer decision. Only the runnerRoundTrips agent-cost field is restored here.

Invariant preserved

Byte-identical-default: with --cost OFF (or on an error response) the serialized response is unchanged. The cost block is still purely additive on the success path.

Verification

• tsc -p tsconfig.json --noEmit — 0 errors
• vitest run request-router-cost.test.ts — 6/6 pass
• oxfmt --check + oxlint --deny-warnings on all 4 changed files — clean
• fallow audit --base origin/main — no issues
• rslib build — success

[github-actions]

Size Report

Metric	Base	Current	Diff
JS raw	1.4 MB	1.4 MB	+268 B
JS gzip	450.4 kB	450.5 kB	+123 B
npm tarball	549.7 kB	549.9 kB	+164 B
npm unpacked	1.9 MB	1.9 MB	+361 B

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	27.9 ms	27.8 ms	-0.1 ms
CLI --help	47.6 ms	47.9 ms	+0.3 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/9722.js	+127 B	+75 B

[thymikee]

Review finding for head 5ef1e70:

plans/phase3-platform-plugin-progress.md still says the cost.runnerRoundTrips runtime surface was removed in #968, but this PR intentionally restores that public agent-cost field. If this lands as-is, the plan becomes stale/misleading for the next Apple/agent-cost worker. Please update the Step (c) request-count bullet to distinguish the dev-only request-count CI gate, which remains removed, from the restored runtime cost.runnerRoundTrips surface.

[github-actions]

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2026-07-01 05:24 UTC