[ranxianglei]

Model: qwen3.8-27b (vllm)

Fixes #242.

Root cause

When the Responses-API compress loop runs round 2+, src/loop/adapter-responses.ts remapped upstream items with:

const mapped = { id: `msg-proxy-${round}-${origId || outputIndex}`, ... }

origId is the full upstream message id (e.g. 54 chars from Codex/OpenAI). With the msg-proxy-2- prefix that is 66 chars — over the upstream 64-char limit for input[].id. Codex Desktop persists that id into its rollout; on every subsequent request the rollout replays it and upstream rejects:

Invalid 'input[42].id': string too long. Expected a string with maximum length 64, but got a string with length 66 instead.

--passthrough does not help (the poisoned id is already persisted client-side). Affected: v0.1.53, Responses path (Codex).

Fix (two parts)

1. Stop minting over-long ids — the round-2+ mapping now uses a deterministic FNV-1a base36 digest instead of embedding the upstream id:

const mapped = { id: `msg-proxy-${round}-${shortItemHash(origId || String(outputIndex))}`, ... }

≤ ~21 chars. All lifecycle events (output_item.added / output_text.delta / output_item.done) share the same mapped id, so references stay intact.

2. Heal already-poisoned rollouts — prepareResponses now runs sanitizeResponsesInputIds(parsed.input) (new export) before the projection reads the input: any input[].id longer than 64 chars is rewritten in place to msg-fix-${shortItemHash(id)} — deterministic and idempotent, so repeated requests keep referencing the same replacement id. Conversations that were permanently 400-ing recover on their next request.

Not changed: /responses/compact (native compaction never carries these ids — a poisoned rollout 400s on its first regular request before compact could run), call_id values, and the ~27-char msg-proxy-${Date.now()}-… ids used by text/tool/marker emission (already within the cap).

Tests

• New round-2 lifecycle test using the exact 54-char upstream id from the issue: asserts the mapped id is ≤ 64 chars and that deltas + done events reference the same mapped id.
• New unit tests for sanitizeResponsesInputIds: short ids untouched, deterministic (same source → same replacement), call_id untouched, idempotent on re-run, non-array tolerated.
• Existing round-2 lifecycle test (msg-proxy-2- prefix assertion) still passes.

typecheck ✅  tests 595/595 ✅  build ✅

[github-actions]

📦 Built Package Artifact

Branch: 2026-08-25_responses-id-length (3abbab5)

Option A — Install from npm PR tag (recommended)

npm install -g billion-context@pr-244

Each push to this PR publishes a new version under the pr-244 npm tag.

Option B — Download artifact

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

tar xzf billion-context-pr244.tgz
npm install -g package

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This comment is automatically updated on each push.

[ranxianglei]

Superseded by #243 — same root-cause fix (that one cleaner: reuses the existing hashId()), plus the ingress-healing commit now pushed onto #243's branch. Keeping the contributor's PR.