[ranxianglei]

Fixes #1249

What

Pins acp-kernel 0.0.85 → 0.0.86, bundling acp-kernel#379/#380:

• tiers.tier2Trigger 5→1000, tier3Trigger 10→2000 — the count path ("满5个块就蒸馏") is default-off. Block count is not a need signal: count-triggered distillations reclaimed ~nothing while rewriting the wire from the fold anchor onward → prefix-cache invalidation far beyond the reclaimed tokens — the sawtooth root cause of [Bug] oh-my-pi 长会话缓存命中率波动：相邻请求 99%→4%，125 folds 估算净收益为负 #1249.
• The release v0.1.53 #238 usage gate on count paths is deleted — percentages never gate compression; growth (≥ growthFloor) and token-mass (≥1.5× growthFloor) are the need signal and stay ungated. tierActionHint now agrees with decideNudge (pure count, default-off).

bili-side surface

• No behavior/config change of bili's own: CompressSettings.tiers remains a boolean (enabled toggle only); triggers are kernel-owned. Users who explicitly want count-driven distillation can no longer get it via bili config (never could) — kernel config is the escape hatch.
• New tests/kernel-tier-defaults.test.ts pins the contract into bili's suite: kernel defaults 1000/2000, and applyCompressSettings never overrides triggers — so a future kernel bump that silently reverts fix: merge all system/developer messages into one leading message (SGLang #377) #379 fails CI here instead of re-opening [Bug] oh-my-pi 长会话缓存命中率波动：相邻请求 99%→4%，125 folds 估算净收益为负 #1249.

Verification

• npm run typecheck clean
• Full suite 2452 tests / 2450 pass / 0 fail (2 E2E-gated skips), incl. the new guard test
• npm run build ✓ — dist/index.js bundles the 1000/2000 defaults (tsup inlines the kernel)

Sequence

acp-kernel 0.0.86 is already live on npm (latest, tag v0.0.86) — this PR only needs to merge and ride the next bili release.

[github-actions]

📦 Built Package Artifact

Branch: 2026-09-25_kernel-0.0.86 (d4f1c3f)

Option A — Install from npm PR tag (recommended)

npm install -g billion-context@pr-1260

Each push to this PR publishes a new version under the pr-1260 npm tag.

Option B — Download artifact

1. Download the artifact from the Actions run
2. Extract the tarball and install:

tar xzf billion-context-pr1260.tgz
npm install -g package

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Install instructions are refreshed on each push.

[ranxianglei]

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[bot] 🏷 Review in progress: pulling branch 2026-09-25_kernel-0.0.86 (d4f1c3f), verifying the diff against current master, running typecheck/test/build locally, and checking CI status. Will report full findings shortly.