[ranxianglei]

Adds Key Design Principle #6 to AGENTS.md, paired with the revert in #191:

Message ids are NEVER reused or duplicated — within a session, a raw content-hash id and a ref number (mNNNNN) denote exactly one message forever. No ref-slot reclamation/recycling of any kind; capacity pressure is resolved by widening REF_WIDTH, never by recycling numbers.

Rationale recorded inline: hosts persist refs across turns and summaries cite tags in rendered text — the model can cite any number it has ever seen, so a re-issued number silently misattributes on decompress (wrong content, not an error). Also formalizes the existing "GC-free" principle (#4) as it applies to the ref map.

Same invariant is being added to the host repos' AGENTS.md (billion-context, billion-context-pi) so hosts treat it as a kernel contract.

[github-actions]

📦 Built Package Artifact

Branch: 2026-09-03_agents-id-invariant (6b6f269)

Option A — Install from npm PR tag (recommended)

In your adapter project:

npm install acp-kernel@pr-192

Each push to this PR publishes a new version under the pr-192 npm tag.

Option B — Download artifact

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

tar xzf acp-kernel-pr192.tgz
npm install ./package

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This comment is automatically updated on each push.

[ranxianglei]

🤖 ework agent · qwen3.8-27b

Reviewed PR #192 (docs-only: AGENTS.md +10 lines, adds Key Design Principle #6). Verdict: LGTM — approve.

Verified against the code:

• Terms are accurate — raw ids are content hashes (deriveMessageId in the wire codec); mNNNNN is the ref number (indexToRef); REF_WIDTH = 5 lives at src/refs.ts:3 and is the right knob for widening the ref space.
• New item fix: split compressible ranges at user-turn boundaries #6 slots correctly after fix: hard-enforce protection of recent messages + last user message #5 under "Key Design Principles"; list continuation renders cleanly.
• Inline rationale matches the paired revert Revert "fix: reclaim dead message refs, reuse exhausted capacity (#176)" — ref slot reuse is unsafe #191 (silent decompress misattribution, broken tag-trust contract, capacity solved by widening not recycling).
• Confirmed fix: reclaim dead message refs, reuse exhausted capacity, classify boundary failures (billion-context#386) #176 is the ref-reclamation PR (merged, shipped in 0.0.48/0.0.49) and Revert "fix: reclaim dead message refs, reuse exhausted capacity (#176)" — ref slot reuse is unsafe #191 is its open revert.

Duplicate screening: no other open/closed issue or PR codifies this invariant or edits the principles list. #191 is the complementary code change, not a duplicate.

Non-blocking notes:

1. Merge ordering — fix: reclaim dead message refs, reuse exhausted capacity, classify boundary failures (billion-context#386) #176's reclamation code (pruneDeadRefs + wrap-around reuse in refs.ts/compress.ts/rebuild.ts/sync.ts) is still on master because Revert "fix: reclaim dead message refs, reuse exhausted capacity (#176)" — ref slot reuse is unsafe #191 hasn't landed. Merging docs: codify id-immutability invariant in AGENTS.md #192 alone would leave AGENTS.md asserting an invariant master currently violates, and the closing line "was reverted (Revert "fix: reclaim dead message refs, reuse exhausted capacity (#176)" — ref slot reuse is unsafe #191)" would read as done before the revert ships. Recommend landing Revert "fix: reclaim dead message refs, reuse exhausted capacity (#176)" — ref slot reuse is unsafe #191 first or concurrently.
2. (Optional) The closing line hardcodes PR numbers fix: reclaim dead message refs, reuse exhausted capacity, classify boundary failures (billion-context#386) #176/Revert "fix: reclaim dead message refs, reuse exhausted capacity (#176)" — ref slot reuse is unsafe #191 into a standing section — fine for traceability; soften only if you want the doc to stand alone without GitHub context.

Still needs a second-agent sign-off and a human merge per repo policy (Agents don't merge). Happy to take the second review or tweak wording if you want the notes addressed.