fix: sanitize inflated relay usage reports + suppress empty-range growth nudges (#476)

[ranxianglei]

Closes #476

Problem

A third-party OpenAI-compatible gateway reported prompt usage at 1.76–2.05× reality (measured per-request payload comparison in #476). ACP inherited that number verbatim as prePruneTokens / currentTokens, which:

1. fabricated growthSinceBaseline → growth nudges injected with zero actionable ranges (candidateCount=0) in sessions whose visible context was entirely compressed-block summaries;
2. sent the model to guess IDs → endId mNNNNN is not available — likely consumed by an existing block. → retry loop (single step 15m02s in the incident).

Both defects verified in code before implementing (see triage comments on #476).

Changes

• AC1+AC2 — new lib/usage-sanity.ts: resolveCurrentUsage(state, messages, logger?) cross-turn inflation detector. Fires only when the reported usage jumps >1.5× while the local chars/4 payload estimate jumps ≤1.5× (both estimates ≥ 5000-token floor); on detection it returns the re-estimated size and logs WARN Relay usage inflation detected — re-estimating context size. Honest reports pass through unchanged; baseline pair {reported, estimated} persisted as new optional SessionState.usageSanity (old state files load fine; detection skips one turn until seeded).
• All three call sites use the same sanitized channel: isContextOverLimits (lib/messages/inject/utils.ts), prePruneTokens + postTokens (lib/hooks.ts).
• AC3 — lib/messages/inject/inject.ts: new noRangesAtAll flag (zero compressible AND zero protected messages) OR-ed into nothingToCompress; new audit reason no_compressible_ranges. This closes the one remaining hole: all other zero-ranges combinations were already covered by allProtected / allInProtectedZone / allBelowMin.
• AC4 — lib/compress/search.ts: buildBoundaryRecoveryHint now enumerates the actual contiguous free spans instead of a first–last window.

Behavior changes (old → new)

What	Old	New	Why
prePruneTokens / postTokens / currentTokens	raw reported usage, inherited verbatim	identical unless relay inflates (>1.5× report jump with ≤1.5× payload jump, both ≥ 5000 est.)	inflated relays must not reach growth heuristics
nudge suppression audit reasons	all_protected, in_protected_zone, below_effective_floor, no_executable_candidates	+ no_compressible_ranges	turns that previously injected phantom nudges now suppress; emergency path falls to the cadence-gated /compact notice
compress boundary-error hint	Current visible: first–last (N msgs). … Call acp_status() to see which blocks consumed which IDs, then retry with valid IDs.	Free ranges: <contiguous spans, cap 8 (+N more)>. K active compressed blocks. Retry with IDs inside the free ranges.	first–last implied continuity across consumed gaps
persisted state	no such field	optional usageSanity {reported, estimated} appended	cross-turn baseline survives restart

Known accepted limitation (documented in module docstring): a one-shot inflation that then holds steady passes the jump gate. An absolute reported-vs-estimated check was deliberately NOT added because chars/4 undercounts CJK up to ~4× and would false-positive on honest CJK-heavy sessions.

Verification

• New tests (19 total): tests/usage-sanity.test.ts (10), tests/nudge-no-ranges-suppression.test.ts (3, multi-turn with side-effect assertions per §5.7), tests/boundary-recovery-hint.test.ts (6) — all pass.
• Fail-on-bug matrix (§5.7): each fix temporarily reverted → corresponding test confirmed FAILING → restored (AC3 revert → phantom nudge injected; AC1/AC2 bypass → baseline not corrected from 100K to 7K; AC4 revert → old hint text detected).
• npm run typecheck clean. Global suite left to CI.

[github-actions]

📦 Built Plugin Artifact

Branch: 2026-10-06_usage-inflation-nudge-fix (89b0347)

Option A — Install from npm PR tag (recommended)

opencode plugin opencode-acp@pr-477 --global

Each push to this PR publishes a new version under the pr-477 npm tag.

Option B — Install from GitHub

opencode plugin "github:ranxianglei/opencode-acp#2026-10-06_usage-inflation-nudge-fix" --global

Option C — Download artifact

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

tar xzf opencode-acp-pr477.tgz
cp -r package/dist ~/.cache/opencode/packages/opencode-acp@latest/node_modules/opencode-acp/dist

3. Restart opencode to pick up changes.

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This comment is automatically updated on each push.

[ranxianglei]

🤖 Powered by ework · qwen3.8-27b

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结论先行：不建议合并。 CI 红（Node 24 job：13 个既有测试失败，Node 22 随之取消）。我没有只信 CI——已本地复现全部失败并逐点隔离出根因：13 个回归全部由本 PR 自己的三处改动引入，不是环境抖动。PR 自己新增的 19 个测试是过的；问题在于它改变了既有行为却没有对齐既有回归测试。

方向上先给一个提醒（对应原 bug #476，外部用户实测）：#476 测到的是稳态 1.76–2.05× 上游虚高。而本 PR 标题主打的 AC1/AC2「sanitize inflated usage」对这种稳态场景基本无效（详见第 6 问）；真正堵住事故症状的是 AC3（零区间抑制）+ AC4（错误提示）。下面按七问展开。

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1. 是什么问题
修 #476：第三方 OpenAI 兼容网关把 prompt usage 报成真实的 1.76–2.05×，ACP 原样继承为 prePruneTokens/currentTokens → 造出虚假 growthSinceBaseline → 在「可见上下文全是压缩块摘要、没有任何可压区间」的会话里注入 growth nudge → 模型乱猜已被消费的 ID → endId mNNNNN is not available 重试死循环（事故单步耗时 15m02s）。

2. 什么原因导致的
两个独立缺陷叠加：(a) 上报 token 数无校验直接进增长启发式；(b) 「零可压 + 零受保护」这个组合原本没有任何抑制分支（allProtected / allInProtectedZone / allBelowMin 三者皆假时的真空洞）。

3. 怎么修复的

• AC1/AC2 新增 lib/usage-sanity.ts：跨轮比值检测（report 跳升 >1.5× 且 payload(chars/4) 跳升 ≤1.5×、两者 ≥5000）时改用重估值；isContextOverLimits、prePruneTokens、postTokens 三个调用点统一走该通道。
• AC3 lib/messages/inject/inject.ts:488 新增 noRangesAtAll（compressible 与 protected 皆空）并入 nothingToCompress，新增审计原因 no_compressible_ranges。
• AC4 lib/compress/search.ts 边界报错改为枚举真实连续空闲 span（上限 8，超出显示 +N more），去掉误导性的 “Call acp_status()” 指引。

4. 是否有回归问题 —— 有，且阻断性（13 个既有测试）
本地复现 + 逐点隔离确认，三类根因：

• AC3 过度抑制（10 个）：tests/inject.test.ts ×8、tests/proportional-baseline.test.ts ×2（含 test: Tier 1 behavioral test coverage + dead code cleanup #23/[Bug]: Per-message nudge triggers every turn after restart — lastPerMessageNudgeTokens not persisted when nudge fires without anchor changes #60/estimateSystemPromptTokens inconsistent between nudge and acp_status after compression #255/Display/acp_status context-usage estimator excludes reasoning tokens (undercounts real usage) #371/[Bug] In-flight prune is a no-op (postTokens == prePruneTokens) at 229k tokens → request exceeds server context → empty-response resume loop #346 等历史回归测试）。这些夹具只 bump tokens.input、消息文本极小且不形成真实可压区间；旧代码从不检查“到底有没有区间”，所以能过；加了 noRangesAtAll 后被抑制。我把 || noRangesAtAll 关掉后这 10 个全绿。说明抑制逻辑对生产是对的（真无可压内容就不该 nudge），是夹具不符合生产（缺 ref 分配 / 内容低于 minCompressRange），需按 §5.7 补成带 ref、内容达标的真实多轮夹具。
• AC1/AC2 误报（2 个）：#342、#384。这是真误报，不是夹具问题：[Bug]: Growth nudges ignore minContextLimit and fire below it #342 第 4 轮合法地 200K→400K 增长（report 跳 2×），但可见窗口只有一个 80K 工具块，chars/4 估算几乎不变 → 触发“relay 虚高”判定 → 被重估到 ~20K，跌破 300K floor → 本该触发的 nudge 被吞。我把 RELAY_INFLATION_RATIO 置 ∞ 后这两个立即通过。根因：跨轮 report 跳幅 vs chars/4 跳幅的比较本身就不可靠（tokenizer ≠ chars/4；report 含 cache/reasoning token；压缩会让窗口内容骤变导致 payload 掉而 report 涨）。
• AC4 遗留陈旧测试（1 个）：tests/compress-search.test.ts:293 仍断言旧文案 /Current visible: m00001–m00002 (2 msgs)/，而新实现输出 Free ranges: … Retry with IDs inside the free ranges.。PR 加了新测试却漏改了这条旧断言。

5. 是否破坏缓存
不涉及 prompt 前缀缓存失效路径；改动都在 nudge 决策与 token 计量层。唯一口径变化：prePruneTokens/postTokens/currentTokens 从“原始上报”切到“可能重估的值”（见行为变更披露），不触碰缓存键。

6. 是否改了设计方向 / 方案是否打到核心
需要提醒：AC1/AC2 对 #476 描述的稳态虚高几乎不起作用——恒定倍率下 reportRatio ≈ payloadRatio，检测条件（前者 >1.5 且后者 ≤1.5）不可能同时成立，所以只在“诚实→虚高”的那一轮过渡期生效一次即自停；而 #476 测到的正是稳态。也就是说标题主打的机制恰好覆盖不到主场景，事故的真正止血靠 AC3+AC4。同时 AC1/AC2 又带来上面的误报回归，当前性价比为负。建议三选一，请你拍板：① 砍掉 AC1/AC2，只留 AC3+AC4（最简，已解决严重症状）；② 保守化为“持续多轮判据 + 默认关的配置项”，并改用 BPE 而非 chars/4 做对照；③ 保留但把阈值大幅上调并补充分层证据。我倾向 ①或②。

7. 是否引入新配置
新增可选持久化字段 SessionState.usageSanity{reported, estimated}（向后兼容：旧状态文件可读，损坏记录会被丢弃）。若保留 AC1/AC2，RELAY_INFLATION_RATIO=1.5 / PAYLOAD_FLOOR_TOKENS=5000 目前硬编码，建议提为配置项。

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收工判定：不可合并。 待作者处理三件事：

1. 更新 tests/compress-search.test.ts:293 到新文案（或删掉，新语义已由 boundary-recovery-hint.test.ts 覆盖）。
2. 按 §5.7 把 10 个受影响的 nudge 回归夹具补成带 ref、内容达标的真实多轮场景，并与新增 nudge-no-ranges-suppression 测试对齐语义（那个用纯摘要 = 真无可压 → 抑制正确；其余夹具应有真实可压内容 → 应触发）。
3. 就 AC1/AC2 的取舍给方向（见第 6 问）。

第 1、2 点方向明确，你确认后我就接手改并走双 agent 评审再交你合并；第 3 点是设计取舍，等你拍板。以上均基于本地复现与逐点隔离验证，未跑全量套件（交由 CI）。