fix: strip model-echoed render tags from tool-call arguments on every wire path

[ranxianglei]

Problem (#933)

Verified chain: kernel renderMessage injects <acp …>mNNNNN</acp> refs into message text (text-only) → model echoes them in output → response-side stripping covered only text fields (content/reasoning/thinking) → tags echoed into tool-call arguments passed through verbatim on every wire format, entered client session storage, and rendered raw in the host TUI. The issue's "move tags to a header channel" main fix is infeasible — the model must read refs from prompt text to cite them in compress calls — so the actionable fix is making the response-side strip structurally complete.

Changes

1. Structural invariant instead of field enumeration (src/loop/tag-echo-filter.ts): new exports stripAcpTagsDeep / findAcpLikeTagSnippetsDeep walk every string leaf of any payload object. Non-streaming strips now also cover tool args: OpenAI function.arguments, Anthropic tool_use.input (+ streaming partial_json), Responses item arguments and reasoning summary[].text.
2. Streaming plugin pipes (src/plugin.ts, opencode/pi/omp mode): per-tool-call argument streams for OpenAI delta.tool_calls[].function.arguments and Anthropic input_json_delta.partial_json; per-item streams for Responses function_call_arguments.delta / reasoning_summary_text.delta, plus one-shot strip on .done payloads. Held mid-tag tails flush before done-family/EOF/error events. Also fixed a real bug found while writing the tests: Responses fc delta fragments live in delta, not arguments — the old-style field read would have passed them through raw.
3. Proxy-mode adapters (src/loop/adapter-*.ts): strip buffered-complete arguments at emission time. adapter-openai additionally reconstructs fragmented raw replays when accumulated args are tag-tainted (a tag spanning fragment boundaries cannot be cut by per-fragment stripping).
4. Kill switch made global (src/server.ts): ACP_RENDER_NONE=1 was previously honored only on the Responses path + compact rebuilds — exactly the wires opencode 插件模式下 render tag 注入消息正文，模型回显漏网后原样渲染进 TUI（元数据与正文同层问题） #933 hit (chat paths) ignored it. Now honored on all paths (OpenAI chat, Anthropic, count_tokens, [bug] ACP 压缩轮以 stop 终止任务：模型输出压缩摘要后零 toolCalls，需用户手动「继续」（#361 同族） #422 fold-refresh re-request). Documented in CONFIGURATION.md.
5. Tests (tests/fix-933-tag-echo-toolargs.test.ts, 6 cases): deep-scan invariant over every carrier field × 3 protocols; mid-tag-split streaming through each pipe (tag broken across fragments); non-streaming JSON × 3 protocols; faithful-client replay loop (assistant turn rebuilt from the clean client stream ⇒ next-turn request carries no tags).

Verification

• npm run typecheck ✓
• npm test: 1674 pass / 0 fail / 2 skipped (gated e2e) ✓
• npm run build ✓

Both compression modes reasoned: plugin mode (carrier = agent's compress tool call) gets the pipe-level strips; proxy mode (carrier = acp_summary) gets the adapter-level strips.

Fixes #933

[ranxianglei]

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[bot] 🏷 Reviewing PR #934 now. Initial state:

• Single commit 8695aee on 2026-09-18_fix-933-tag-echo-toolargs, 8 files, +623/−50 — diff scope matches the described fix, no unrelated churn visible in the stat.
• Stale base: the branch forked from 55da3f0 (v0.1.117), but master has since advanced to 852b068 (~40 merges incl. feat: standard npm install path for the opencode native plugin (#925) #931, fix: TTL-cache the opencode-native per-request health probe (#928) #930, feat: opencode v1 — keep opencode-acp legacy sessions working under bili (#920) #923, opencode v1: keep opencode-acp legacy sessions working after switching to bili #920, feat: OpenCode 1.x native support — V1 .server() hooks on the standard install path #919, release v0.1.118 #916/v0.1.118, fix: recover from mid-stream upstream truncations (#413 relaxation + continuation retry) #891, fix(loop): swallow a render tag wrapped around the model's turn #872, fix(preflight): fold deep enough for a payload far over the window (#868) #869…). Four files overlap both sides: src/loop/tag-echo-filter.ts, src/plugin.ts, src/server.ts, CONFIGURATION.md → GitHub reports the PR as unmergeable.

Per repo convention (§7.2: rebase to CURRENT master before claiming mergeable), I'm rebasing the branch onto origin/master, resolving by union of intent where the two sides touch the same regions, then re-running typecheck + full test suite + build. Will follow up here with the result and CI status.

[github-actions]

📦 Built Package Artifact

Branch: 2026-09-18_fix-933-tag-echo-toolargs (a757033)

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Option B — Download artifact

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tar xzf billion-context-pr934.tgz
npm install -g package

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[ranxianglei]

This branch now conflicts with master and can't merge as-is. A clean rebase preserving the full change (plus conflict resolution: master's done-family split in plugin.ts, #728 localInputEstimate merged with the ACP_RENDER_NONE gate in server.ts) is up as #935 — please close this one in favor of #935.