[leehack]

Summary

• Sweep of #1815 follow-ups: macOS arm64 LiteRT-LM library smoke support, model-store Flutter/test floors, and a closed-stdout guard in the Chrome test supervisor.
• tool/litert_lm_library_smoke.dart: macOS arm64 is a supported host and resolves libLiteRtLm.dylib.
• packages/llamadart_model_store/pubspec.yaml: flutter: ">=3.38.6" (first Flutter whose Dart 3.10.7 satisfies sdk: ^3.10.7) and test: ^1.26.3 (first test accepting Flutter 3.38.6's test_api 0.7.7); rationale in website/docs/maintainers/model-store-package.md.
• tool/ci/supervise_chrome_test.py: reserve_standard_descriptors() keeps a closed fd 0/1/2 from being reused by the next open(), which sent echoed output into the events file.

Production-readiness scope

• User-facing scope: CI/tooling and one unpublished package's version floors; no public API change.
• Supported platforms/paths: smoke tool on Linux, macOS arm64, Windows x64; supervisor on Linux CI.
• Unsupported or intentionally unavailable paths: unchanged; other hosts still fail the smoke tool loudly.
• Out of scope / follow-ups: None.

Completeness checklist

• Declared scope is fully implemented, or explicitly reduced above.
• Unsupported platform/option combinations fail loudly with actionable diagnostics or are clearly documented as unavailable.
• Public API docs, README/website docs, examples, support matrices, and changelog entries are updated where relevant. N/A for the changelog: no user-facing release change.
• Regression coverage covers the original issue plus key negative/version-skew paths where relevant.
• Public capability changes update the validation coverage registry with a pack or a reasoned, issue-linked exemption. N/A: no capability change.
• Security/privacy review completed: no secrets, tokens, URLs or paths added to logs or metadata.
• Follow-up work is tracked or marked "None" above.

PR type guidance

• Feature PR: N/A.
• Bugfix PR: closed-stdout supervisor echo; root cause and regression test above.
• Docs-only PR: N/A.

Test Plan

Pinned Flutter 3.47.1, macOS arm64, head 6430609a437f499b8c8807f4af4e39c22018d426.

• dart run tool/prepare_workspace.dart: clean.
• dart format --output=none --set-exit-if-changed .: 0 changed.
• dart analyze: clean. check_platform_boundaries.dart: OK.
• dart test -p vm -j 1 --exclude-tags local-only: CI green; test/unit/tooling +1608 ~5 -6 locally (the 6 failures are the missing-pwsh windows_registry tests only).
• dart test -p chrome --exclude-tags local-only: N/A, no lib/ or Web change.
• coverage-lib: N/A, no lib/ change.
• Other validation:
  • test/ci/test_supervise_chrome_test.py: 21 OK in python:3.12-slim; manual closed fd 0/1/2/1+2/all OK.
  • litert_lm_library_smoke_test: +61; real macOS arm64 smoke run RESULT exit 0.
  • Model store on the Flutter 3.38.6 image (Dart 3.10.7): pub get, analyze --fatal-infos, pub downgrade, flutter test +51 (non-root).

Matrix Evidence

Matrix row	Scope covered	Platform / model / backend	Result	Evidence / notes
high-risk-exact-head-independent-qa	exact-head audit, v2 evidence	macOS arm64 + Linux container	PASS (exit 2, unverifiedPrerequisites, expected locally)	audit record below

Review Notes

• Independent review status: fresh-agent auditor, PASS at 6430609a437f499b8c8807f4af4e39c22018d426, zero blocking findings.
• CI status / head SHA: 35 pass, 8 skipped, 0 fail at 6430609a437f499b8c8807f4af4e39c22018d426.
• Base note: main has since moved to 50d897054 (#1829, #1826); no file overlap and git merge-tree is clean. Evidence is bound to merge base 9f532720b.

High-risk regression review

Classification: high-risk
Surfaces: regressionPolicy
Required matrix: dart run tool/testing/test_matrix.dart --tier high-risk

• Classification: high-risk (regressionPolicy)
• Implementation task: this PR's author session
• Independent blocking QA task: fresh-agent auditor, PASS, mutation controls: dropping the reserve_standard_descriptors call fails test_closed_stdout_cannot_redirect_the_echo_into_events; dropping the macosArm64 line fails the macOS smoke cases
• Exact head / current base: 6430609a437f499b8c8807f4af4e39c22018d426 / 9f532720b9de18f263e492ef1c049cc1abfd0ae8 (merge base)
• Production-branch deletion, bypass, or miswire proof: N/A; additive guard and host entry
• Affected-family real-model/artifact evidence: N/A; no model-family path
• Explicit unavailable-family or other N/A evidence: N/A
• Known PR-caused P1 regressions: 0
• Unresolved review threads: 0
• Readiness evidence: v2 high_risk_readiness.dart run exits 2 (unverifiedPrerequisites), as expected for a local run.

[github-actions]

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