[leehack]

Summary

• tool/litert_lm_library_smoke.dart (the LiteRT-LM Smoke library step) now fails when the pinned Linux or Windows LiteRT-LM runtime does not export litert_lm_native_in_process_litert_abi_version or does not return 1, so a repin that drops the marker fails CI instead of only hardware runs.
• Covers Linux x64 and Windows x64 (the existing smoke matrix). Linux arm64 is not covered: an ubuntu-24.04-arm entry failed in flutter-action ("Unable to determine Flutter version ... 3.47.1 architecture: arm64"), so it was dropped.
• The smoke body is now runLiteRtLmLibrarySmoke, which enforces the marker and puts the value in the RESULT JSON as inProcessLiteRtAbi; main() only prints it.
• Maintainer note in native-and-web-sync.md, including that rolling the pin back to a pre-marker tag (v0.18.1-4, v0.19.0, v0.19.1, v0.19.1-1) fails the smoke on Linux/Windows by design.

Refs #1837 #1845

Production-readiness scope

• User-facing scope: None directly; CI guard for the embedding gate from #1830.
• Supported platforms/paths: CI (Linux x64, Windows x64), tooling.
• Unsupported or intentionally unavailable paths: Apple/Android runtimes are not required to export the marker (helper returns early).
• Out of scope / follow-ups: Linux arm64 marker check (needs an arm64 runner with Dart, or a static ELF export probe of the pinned archive); to be filed under #1845.

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. (N/A: tooling/docs only)
• Public API docs, README/website docs, examples, support matrices, and changelog entries are updated where relevant. (changelog N/A: not user-visible)
• Regression coverage covers the original issue plus key negative/version-skew paths where relevant.
• Public capability changes update the validation coverage registry. (N/A: no capability change)
• Security/privacy review completed: no secrets, tokens, signed URLs or secret-bearing paths added.
• Follow-up work is tracked in GitHub Issues, or marked "None" above.

PR type guidance

• Bugfix PR (CI gap): no runtime code; negative path covered by tests below.

Test Plan

• dart run tool/prepare_workspace.dart
• dart format --output=none --set-exit-if-changed .
• dart analyze
• dart test -p vm -j 1 --exclude-tags local-only test/unit/tooling/
• dart test -p chrome -- N/A: no web code
• coverage-lib -- N/A: no lib/ change
• Docs: ./tool/docs/build_site.sh --port 4817 passes

Failing-first / mutation evidence

• Tests compile c_api_version.c three ways (symbol absent, returns 0, returns 1). Absent and 0 throw StateError for linuxX64/linuxArm64/windowsX64; 1 passes; macOS/Android skip the check.
• runLiteRtLmLibrarySmoke tests (injected library) assert inProcessLiteRtAbi == 1 on Linux/Windows and StateError for absent/0.
• Mutants killed: (1) replacing the requireInProcessLiteRtMarker call with a constant null; (2) wrapping it in try/on StateError; (3) tolerating a missing export.

Matrix Evidence

Matrix row	Scope covered	Platform / model / backend	Result	Evidence / notes
static-format-analyze	format, analyze	macOS, Flutter 3.47.1	Pass	clean
tooling suite	test/unit/tooling/	macOS VM	Pass	litert_lm_library_smoke_test.dart 65/65; only windows_registry_qualification_test.dart fails locally (no pwsh)
LiteRT-LM Smoke	pinned v0.19.1-2 desktop bundles	CI linux x64, windows x64	Pass (run 42636717551)	prior head dc058a2a: run 42610329205 passed on both

Review Notes

• Independent review status: pending (standard-risk)
• CI status / head SHA: green / b068961a2

Risk classification

• Classification: standard (classify_high_risk_changes.dart on the current diff)
• Implementation task: lane 2 of #1845
• Known PR-caused P1 regressions: 0
• Unresolved review threads: 0

[leehack]

Landed through the 0.19.2 batch integration PR #1870 (rebase merge, one commit per constituent; this PR's pinned head was audited/CI-gated there).

[github-actions]

Chat app preview removed for leehack/llamadart-chat-pr-1849.