[ranxianglei]

Closes #605 — tracking issue for this PR.

What

Adapts the proxy to acp-kernel 0.0.45's new absorb pipeline (kernel PR #139, merged) — closes #14 on the companion billion-context-pi tracker direction: 小上下文场景下, 工具调用后模型立即复述关键结果, 原始工具输出下一轮隐藏.

• src/absorb.ts (new): absorbEnabled / applyAbsorbConfig (settings → kernel Config.absorb, percent parsing for contextThresholdPct) and executeAbsorb. The wire result carries the model's summary verbatim inside <absorbed-summary> — the absorb tool_use is rewritten to text on the wire, so that text is the only durable record of the original output.
• Injection: absorb tool + system-prompt section for anthropic / openai / responses (streaming loops included), gated on absorb being enabled in compress settings. Plugin manifest and MCP tool list now advertise absorb (5 tools); plugin tool API executes it under the session lock.

Kernel 0.0.31 → 0.0.45 upgrade fallout (fixed here)

1. openaiToCore now hoists the leading system/developer prefix out of the fold space. prepareOpenai re-injects systemText (restoring a developer head role) — without this the host system prompt is silently dropped from every rebuilt request.
2. Kernel KEEP_LAST_ORPHANED=2 (issue release v0.1.2 #9 fix) keeps the newest two orphaned compress calls visible. In plugin mode the wire echo of an executed compress carries a host id that never matches the block's plugin_* call id → permanent orphan → stays visible. hidePluginEchoCompressCalls drops the consumed tail pair before the turn.
3. Pinned acp-kernel to exact 0.0.45-pr.160.14 (the npm preview of kernel release PR refactor: adopt acp-kernel/wire — codecs move to the kernel #160). Follow-up commit flips this to 0.0.45 once the kernel release lands on npm — merge this PR after that.

Tests

518/518 pass (node --import tsx --test), tsc --noEmit --project tsconfig.build.json clean, tsup build clean:

• roundtrip tests adapted to the hoist contract (systemText + injectOpenaiSystem)
• manifest / MCP tool lists now expect 5 tools
• plugin fold test passes again (echo pair hidden, range folded, summary retrievable via search_context)
• 6 new unit tests for absorbEnabled / applyAbsorbConfig / executeAbsorb (disabled fast-fail, missing-summary guidance, success records + hides + verbatim summary, idempotency, unknown ref)

Merge is human-only per AGENTS.md.

[ranxianglei]

Review vs master 3cd85b6 (kernel 0.0.56): ❌ superseded in approach — do not merge; use as design reference (#605).

Two blockers:

1. Kernel pin is a PR-preview tag: "acp-kernel": "0.0.45-pr.160.14" — a pr-160 dist-tag artifact, not a stable release. Not installable in CI reproducibly.
2. Kernel now ships the absorb API natively — verified exports in 0.0.56: ABSORB_TOOL, ABSORB_TOOL_OPENAI, ABSORB_TOOL_NAME, ABSORB_TOOL_DESCRIPTION, ABSORB_PROMPT_MARKER, DEFAULT_ABSORB_CONFIG, appendAbsorbPrompts, applyAbsorb, buildAbsorbPrompt, buildAbsorbSystemPrompt, parseAbsorbInput, hideAbsorbedMessages, isAbsorbCandidate, resolveAbsorbConfig. This PR's host-side reimplementation (17 files, +344) predates that and would fork the logic.

Rework direction (#605): wire the kernel API the same way search_context was wired (kernel-owned semantics, host = thin injection + execution + hide). Concretely: inject ABSORB_TOOL(_OPENAI) alongside the compress tools, execute applyAbsorb server-side, call hideAbsorbedMessages in the wire rebuild, honor resolveAbsorbConfig/DEFAULT_ABSORB_CONFIG. The PR's tests (roundtrip coverage) remain a useful spec for behavior.

(tracking: #605)

[ranxianglei]

Superseded by PR #615 (full kernel-absorb wiring, tracked in #605/#616).

PR #615 完整实现了本 PR 的意图, 且基于 kernel 0.0.56 的官方 absorb API (ABSORB_TOOL/applyAbsorb/parseAbsorbInput/hideAbsorbedMessages/appendAbsorbPrompts/DEFAULT_ABSORB_CONFIG), 而不是 host 侧重造:

• 三协议门控 + plugin tool API 接线 (src/absorb.ts)
• responses adapter buffer absorb function_call (修 absorb: responses adapter raw-replayed absorb function_call — feature broken on /v1/responses wire (fixed pre-merge in #615) #616, 本 PR 未覆盖)
• persist absorbed 字段 (重启不复活, 本 PR 未覆盖)
• netting (compressCreditTokens) 与 fix: net post-compress usage credit + hand launcher context windows to the proxy (#252) #252 对齐
• 253 行测试 + 文档 EN/zh

关闭本 PR, 保留其原始设计价值作为 #605 spec 的参考。感谢提交!