[leehack]

Summary

Prepares llamadart and all three Apple runtime companions at 0.19.2. Release notes: the compacted 0.19.2 section, covering #1855, #1853, #1836, #1867, #1531 and #1858 (batch #1870). Cut from main at 99b8406e3; main 2c3a959b0 (with #1873) is merged in as 6d3e63328, no rebase.

Draft: the #1872 fix (#1873) is merged and folded into the #1836 bullet, so nothing is pending. High-risk (artifactConsumer); an independent exact-head audit follows before this is marked ready. Merging into main publishes** core 0.19.2, then the three companions, to pub.dev through release_on_prep_merge.yml, so it needs explicit maintainer approval.

Production-readiness scope

• User-facing scope: release metadata and docs only. No native or Web pin changes: llama.cpp v0.9.0, LiteRT-LM v0.19.1-2, stable-diffusion v0.3.0-3, Web bridge v0.1.83 (unchanged from 0.19.1) and Web LiteRT-LM @litert-lm/[email protected].
• Companions: git diff v0.19.1..main -- packages/ is empty, but the verifier requires the companion install snippets to name core ^0.19.2. That changes each companion's publishable contents, and companion_pub_preflight.dart rejects republishing 0.19.1 (all three failed before the bump). All three move to 0.19.2 with a README refresh entry, as in the 0.17.5 precedent (#1699). Their Package.swift pins and llamadart constraints do not change: the LiteRT-LM companion keeps >=0.19.1 <0.20.0, and the llama.cpp and stable-diffusion companions keep >=0.19.0 <0.20.0.
• Supported platforms/paths: the documented support matrix, unchanged.
• Unsupported or intentionally unavailable paths: unchanged.
• Out of scope / follow-ups: genkit_llamadart and llamadart_model_store are versioned independently and not touched. MIGRATION.md is unchanged: no breaking change for default users. None.

Completeness checklist

• The declared scope is implemented.
• Unsupported combinations: N/A. No runtime behavior change in this PR.
• README, install docs, companion READMEs and changelogs (core, docs, three companions) are updated. The docs changelog is not trimmed (patch release; it keeps 0.19.x and 0.18.x).
• Regression coverage: release-docs gates pass; the tooling suites ran.
• Validation coverage registry: N/A. No public capability change in this PR.
• Security review: no secrets, tokens or signed URLs added.
• Follow-ups: None.

PR type guidance

• Release preparation: bumps versions, install snippets and lockfiles, and promotes and compacts the changelogs. It changes no pin, Package.swift, hook code or .gitattributes. The normal high-risk route applies.
• Feature PR / Bugfix PR / Docs-only PR: N/A. Release preparation.

Changelog compaction (## Unreleased -> ## 0.19.2, both core changelogs)

• Added the bridge-tag baseline line and the runtime baseline paragraph (no pin changed).
• Folded the Count the LiteRT-LM runtime-template prompt as native prefill reads it #1873 fix into the LiteRT-LM .litertlm: separate the reported/rendered bundle chat template from the Dart-side format and capability template #1836 bullet (tokenCount matches the runtime's prefill for Gemma 4 and Qwen3.5), because the regression never shipped.
• Kept the six bullets, one issue link each, with tightened wording; no user-visible item was dropped.

Test Plan

Run with the pinned Flutter 3.47.1 SDK (Dart 3.13.1) and an isolated TMPDIR.

• dart run tool/prepare_workspace.dart: only the expected lock changes.
• dart format --output=none --set-exit-if-changed .: 0 changed.
• dart analyze: no issues.
• dart test -p vm -j 1 --exclude-tags local-only: ran the tool/ci/markdown_test_suites.txt suites plus test/unit/tooling/ locally (re-run after the merge, same 6 pwsh-only failures, 6 failed). All 6 are in windows_registry_qualification_test.dart and need pwsh, which this macOS host lacks (same as Prepare 0.19.1 release #1844). CI runs the full lane.
• dart test -p chrome --exclude-tags local-only: N/A locally. No lib/ or Web change; CI runs it.
• coverage-lib: N/A. No lib/ change.
• Other checks:
  • check_platform_boundaries.dart: OK.
  • verify_release_docs_versions.dart, normal and --release-prep: both exit 0 in a full-history clone (the local clone is shallow).
  • check_webgpu_bridge_tag.dart: OK.
  • companion_pub_preflight.dart: OK for all three companions.
  • check_core_archive.py: pass, 1,891 files staged.
  • ./tool/docs/build_site.sh: OK, no broken links.
  • Lock regeneration through pub only: example/chat_app, packages/llamadart_validation and website/examples/observability change only local core and companion versions.
  • Classifier: high-risk (artifactConsumer).

Matrix Evidence

Matrix row	Scope covered	Platform / model / backend	Result	Evidence / notes
high-risk-exact-head-independent-qa	exact-head release audit	macOS host	Pending	Independent audit to run on the exact head.
release-metadata-verification	versions, constraints, changelog promotion	macOS host	PASS	verify_release_docs_versions --release-prep exits 0 (full-history clone).
release-companion-pub-gate	companion pub.dev availability and constraints	pub.dev API	PASS (pre-merge)	companion_pub_preflight OK; companion 0.19.2 not yet published.
release-representative-smokes	representative examples	macOS host	PASS (partial)	check_core_archive.py resolves and analyzes the packaged basic example. No model-backed smoke for this metadata-only PR.
genkit-release, android-release-device-pool, structured-output-adversarial, litert-lm-v1-public-*, litert-lm-json-schema	N/A	N/A	N/A	No Genkit, Android runtime, parser, grammar, template or LiteRT-LM code change in this PR.

Review Notes

• Independent review status: pending (draft until the audit passes).
• CI status / head SHA: pending for 6d3e63328f29e24cfbc8460def525d6ecff6abe0.

High-risk regression review

• Classification: high-risk (artifactConsumer).
• Implementation task: 0.19.2 release prep, branch release/prep-0.19.2.
• Independent blocking QA task: pending.
• Exact head / current base: 6d3e63328f29e24cfbc8460def525d6ecff6abe0 / 2c3a959b0 (main).
• Production-branch deletion, bypass, or miswire proof: N/A. No production code change.
• Affected-family real-model/artifact evidence: N/A. No pin change.
• Explicit unavailable-family or other N/A evidence: N/A. No runtime change.
• Known PR-caused P1 regressions: 0.
• Unresolved review threads: 0.

Independent audit

Exact head 6d3e63328f29e24cfbc8460def525d6ecff6abe0 against main 2c3a959b0: PASS, 0 blocking, 0 PR-caused P1, 0 review threads. Released sections byte-identical to v0.19.1; companion bumps confirmed required by verify_release_docs_versions and companion_pub_preflight; no native/SwiftPM pin change since v0.19.1; check_core_archive.py and both verifier runs pass; tokenCount claim verified on Gemma 4 and Qwen3.5 real bundles. Readiness evidence v2: local run exits 2. CI on the exact head: 36 pass, 9 skipped.

[github-actions]

Chat app preview removed for leehack/llamadart-chat-pr-1871.