fix(#325): floor meter at provider anchor minus tokens reclaimed since it

src/floor-stale.ts

@@ -1,7 +1,7 @@
 // pi's getContextUsage() anchors on the last assistant message with valid
-// provider usage. A successful compress lands AFTER that anchor, so the
-// floor must be skipped for the next LLM call (mirrors pi's own
-// "usage source must be post-compaction" compaction check).
+// provider usage; a successful compress after that anchor leaves it reflecting
+// the pre-compression request until the next turn reports fresh usage.
+import type { CompressionBlock } from "acp-kernel";
 import { isCompressSuccessText } from "./compress-tool.js";
 import { extractText } from "./messages.js";
 
@@ -32,13 +32,16 @@ function validAnchorUsage(u: UsageLike): boolean {
   return total > 0;
 }
 
-/** True when the last valid assistant usage anchor comes strictly BEFORE the
- *  last successful compress toolResult — the host's provider-usage number
- *  still reflects the pre-compression request. Failed/no-op compresses don't
- *  count (nothing was reclaimed). */
-export function usageAnchorPredatesCompression(entries: AnchorEntry[]): boolean {
+interface AnchorScan {
+  lastUsageIdx: number;
+  lastCompressIdx: number;
+  compressIdxByCallId: Map<string, number>;
+}
+
+function scanEntries(entries: AnchorEntry[]): AnchorScan {
   let lastUsageIdx = -1;
   let lastCompressIdx = -1;
+  const compressIdxByCallId = new Map<string, number>();
   for (let i = 0; i < entries.length; i++) {
     const m = entries[i]!.message;
     if (!m) continue;
@@ -52,7 +55,46 @@ export function usageAnchorPredatesCompression(entries: AnchorEntry[]): boolean
       isCompressSuccessText(extractText(m.content))
     ) {
       lastCompressIdx = i;
+      compressIdxByCallId.set(m.toolCallId, i);
     }
   }
-  return lastCompressIdx > lastUsageIdx;
+  return { lastUsageIdx, lastCompressIdx, compressIdxByCallId };
+}
+
+/** True when the last valid assistant usage anchor comes strictly BEFORE the
+ *  last successful compress toolResult — the host's provider-usage number
+ *  still reflects the pre-compression request. Failed/no-op compresses don't
+ *  count (nothing was reclaimed). */
+export function usageAnchorPredatesCompression(entries: AnchorEntry[]): boolean {
+  const scan = scanEntries(entries);
+  return scan.lastCompressIdx > scan.lastUsageIdx;
+}
+
+export interface AnchorStaleness {
+  // anchor still reflects the pre-compression request
+  predates: boolean;
+  // Σ max(0, compressedTokens − summary) over active blocks whose compress
+  // landed after the anchor; unattributable/pre-anchor blocks are excluded
+  netReclaimed: number;
+}
+
+// issue #325: flooring at a stale anchor's raw value re-fires a false EMERGENCY,
+// while skipping it under-counts by the fixed overhead the host already counts.
+// Return how much was reclaimed since the anchor so callers floor at
+// `anchor − netReclaimed` instead of either extreme.
+export function compressionAnchorStaleness(
+  entries: AnchorEntry[],
+  blocks: readonly CompressionBlock[],
+  countTokens: (text: string) => number,
+): AnchorStaleness {
+  const scan = scanEntries(entries);
+  let netReclaimed = 0;
+  for (const block of blocks) {
+    if (!block.active || block.compressCallId == null) continue;
+    const idx = scan.compressIdxByCallId.get(block.compressCallId);
+    if (idx == null || idx <= scan.lastUsageIdx) continue;
+    const saved = (block.compressedTokens ?? 0) - countTokens(block.summary ?? "");
+    netReclaimed += saved > 0 ? saved : 0;
+  }
+  return { predates: scan.lastCompressIdx > scan.lastUsageIdx, netReclaimed };
 }

src/index.ts

@@ -24,7 +24,7 @@ import { delegateStatusWidget } from "./fleet-widget.js";
 import { wireToolGuardrails } from "./tool-guardrails.js";
 import { debug, logError, logInfo, logWarn, logThrow, closeLogStream } from "./log.js";
 import { collectCoveredMessageIds, estimateTokens, lastUserMessageId, collectImageTokens, modelSupportsImages } from "./tokens.js";
-import { usageAnchorPredatesCompression } from "./floor-stale.js";
+import { compressionAnchorStaleness } from "./floor-stale.js";
 import { checkForUpdate } from "./update.js";
 import {
   THROTTLE_RETRY_ERROR_MESSAGE,
@@ -244,13 +244,18 @@ function wireContextTransform(pi: ExtensionAPI, runtime: AcpRuntime): void {
       // a heuristic (images, mixed content, per-model tokenizer drift), so
       // the 0.75/0.95 bands run on the real scale via the floor. realUsage is
       // anchored on the last assistant's provider-reported usage + trailing
-      // estimate. Only ever raises (never lowers); skipped while the anchor
-      // predates a successful compress (floor-stale.ts). tokenCount only
-      // feeds processTurn.
+      // estimate. Only ever raises (never lowers). While the anchor predates a
+      // successful compress its raw value still reflects the pre-compression
+      // request, so we subtract the tokens reclaimed since it (issue #325)
+      // rather than skip the floor. tokenCount only feeds processTurn.
       let tokenCount = sentTokens;
       const realPromptTokens = realUsage?.tokens ?? 0;
-      if (!usageAnchorPredatesCompression(entries) && realPromptTokens > tokenCount) {
-        tokenCount = realPromptTokens;
+      if (realPromptTokens > 0) {
+        const { predates, netReclaimed } = compressionAnchorStaleness(entries, state.blocks, defaultCountTokens);
+        const effectiveFloor = predates ? Math.max(0, realPromptTokens - netReclaimed) : realPromptTokens;
+        if (effectiveFloor > tokenCount) {
+          tokenCount = effectiveFloor;
+        }
       }
       // Self-heal (armed): after an overflow, force this turn's usage to >=95%
       // so the kernel's emergency nudge + tool-result truncate fire immediately,

tests/floor-stale.test.ts

@@ -1,6 +1,7 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { usageAnchorPredatesCompression } from "../src/floor-stale.js";
+import type { CompressionBlock } from "acp-kernel";
+import { usageAnchorPredatesCompression, compressionAnchorStaleness } from "../src/floor-stale.js";
 
 // The issue #257 floor must be skipped while the host's provider-usage anchor
 // (the usage on the last valid assistant message) predates the last
@@ -96,3 +97,86 @@ test("non-compress toolResults are ignored", () => {
   ];
   assert.equal(usageAnchorPredatesCompression(entries), false);
 });
+
+// issue #325: compressionAnchorStaleness attributes reclamation to blocks whose
+// creating compress toolResult lands after the last valid usage anchor, so the
+// caller can floor at (anchor − netReclaimed) instead of skipping the floor.
+const ct = (t: string): number => t.length;
+const blk = (over: Partial<CompressionBlock> = {}): CompressionBlock => ({
+  blockId: "b0", runId: "r", tier: 1, summary: "abcde", directMessageIds: [], effectiveMessageIds: [],
+  directBlockIds: [], compressedTokens: 1000, createdAt: Date.now(), survivedCount: 0, generation: "young", active: true, ...over,
+});
+
+test("staleness: fresh anchor → not predates, nothing reclaimed", () => {
+  const entries = [
+    msg("e0", { role: "user", content: "go" }),
+    assistantUsage("e1"),
+    compressResult("e2", PANEL_OK),
+    assistantUsage("e3"),
+  ];
+  const r = compressionAnchorStaleness(entries, [blk()], ct);
+  assert.equal(r.predates, false);
+  assert.equal(r.netReclaimed, 0);
+});
+
+test("staleness: stale anchor reclaims a post-anchor block", () => {
+  const entries = [
+    msg("e0", { role: "user", content: "go" }),
+    assistantUsage("e1"),
+    compressResult("e2", PANEL_OK), // toolCallId c1
+  ];
+  const r = compressionAnchorStaleness(entries, [blk({ compressCallId: "c1" })], ct);
+  assert.equal(r.predates, true);
+  assert.equal(r.netReclaimed, 995); // 1000 − len("abcde")
+});
+
+test("staleness: pre-anchor block is not counted as reclaimed", () => {
+  const entries = [
+    msg("e0", { role: "user", content: "go" }),
+    compressResult("e1", PANEL_OK), // c1 before any usage anchor
+    assistantUsage("e2"),
+  ];
+  const r = compressionAnchorStaleness(entries, [blk({ compressCallId: "c1" })], ct);
+  assert.equal(r.predates, false);
+  assert.equal(r.netReclaimed, 0);
+});
+
+test("staleness: inactive and unattributable blocks are skipped", () => {
+  const entries = [
+    msg("e0", { role: "user", content: "go" }),
+    assistantUsage("e1"),
+    compressResult("e2", PANEL_OK), // c1
+  ];
+  const r = compressionAnchorStaleness(entries, [
+    blk({ compressCallId: "c1", active: false }),
+    blk({ blockId: "b1", compressCallId: undefined }),
+  ], ct);
+  assert.equal(r.predates, true);
+  assert.equal(r.netReclaimed, 0);
+});
+
+test("staleness: negative savings clamp to zero", () => {
+  const entries = [
+    msg("e0", { role: "user", content: "go" }),
+    assistantUsage("e1"),
+    compressResult("e2", PANEL_OK), // c1
+  ];
+  const r = compressionAnchorStaleness(entries, [blk({ compressCallId: "c1", compressedTokens: 3 })], ct);
+  assert.equal(r.predates, true);
+  assert.equal(r.netReclaimed, 0); // 3 − 5 < 0 → clamped
+});
+
+test("staleness: sums multiple post-anchor blocks", () => {
+  const entries = [
+    msg("e0", { role: "user", content: "go" }),
+    assistantUsage("e1"),
+    compressResult("e2", PANEL_OK), // c1
+    msg("e3", { role: "toolResult", toolName: "compress", toolCallId: "c2", content: [{ type: "text", text: PANEL_OK }] }),
+  ];
+  const r = compressionAnchorStaleness(entries, [
+    blk({ compressCallId: "c1", compressedTokens: 1000 }), // 995
+    blk({ blockId: "b1", compressCallId: "c2", compressedTokens: 2000 }), // 1995
+  ], ct);
+  assert.equal(r.predates, true);
+  assert.equal(r.netReclaimed, 2990);
+});

tests/sent-view-arbitration.test.ts

@@ -1,6 +1,6 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { rm } from "node:fs/promises";
+import { rm, writeFile } from "node:fs/promises";
 import { createAcpExtension } from "../src/index.js";
 
 // Nudge arbitration runs on the SENT-VIEW estimate floored at the host's real
@@ -112,23 +112,58 @@ test("context transform stays idle when there is no provider usage to floor from
   await rm(`${STATE_FILE}.500.acp.json`, { force: true });
 });
 
-// Stale-anchor guard (PR #258 review): the usage anchor (e19's 175K usage)
-// predates the successful compress toolResult that follows it. The next LLM
-// call must NOT floor the meter at the pre-compress anchor — the context was
-// just shrunk, so no emergency fires even though the host still reports 97%
-// of the window (same stream and fakeCtx(175_000) as the floor test above).
-test("context transform skips the provider-usage floor while the anchor predates a successful compress", async () => {
-  await rm(`${STATE_FILE}.175001.acp.json`, { force: true });
-  const { api, handlers } = captureApi();
-  createAcpExtension({ modelContextLimit: 180_000 })(api as any);
+// issue #325: the usage anchor (e19's 175K) predates the successful compress
+// toolResult that follows it, so the host's 175K still reflects the PRE-compress
+// request. Seeding a real reclaiming block makes the meter floor at
+// (anchor − reclaimed) instead of skipping the floor or flooring at the raw
+// anchor — the next turn must not snap back to 97% and re-fire a false EMERGENCY.
+async function seedState(file: string, block: Record<string, unknown>) {
+  const state = { blocks: [block], nextBlockId: 2, messageRefs: { byRaw: {}, byRef: {}, nextRef: 0 }, nudge: {}, stats: {} };
+  await writeFile(file, JSON.stringify(state), "utf8");
+}
 
-  const ctx = fakeCtx(175_000);
+const seedBlock = (over: Record<string, unknown> = {}) => ({
+  blockId: "b0", runId: 0, tier: 1, generation: "young", active: true,
+  summary: "compressed early history", directMessageIds: ["e1", "e2", "e3"],
+  effectiveMessageIds: ["e1", "e2", "e3"], directBlockIds: [], compressedTokens: 60_000,
+  survivedCount: 3, createdAt: Date.now(), compressCallId: "c1", ...over,
+});
+
+const staleStream = (): any[] => {
   const entries = [msg("e0", "user", "start " + MID)];
   for (let i = 1; i <= 18; i++) entries.push(msg(`e${i}`, i % 2 ? "assistant" : "user", `f${i} ` + MID));
   entries.push({ type: "message", id: "e19", parentId: null, timestamp: "", message: { role: "assistant", content: "f19 " + MID, timestamp: Date.now(), usage: { input: 175_000, cacheRead: 0, cacheWrite: 0 } } });
   entries.push({ type: "message", id: "e20", parentId: null, timestamp: "", message: { role: "toolResult", toolName: "compress", toolCallId: "c1", content: [{ type: "text", text: "▣ ACP | 42.3K → 18.9K tokens (~23.4K reclaimed, 3 blocks)" }], timestamp: Date.now() } });
-  branchEntries = entries;
-  const r = await fire(handlers, entries, ctx);
-  assert.equal(nudgeCount(r), 0, "no nudge: usage anchor predates a successful compress, floor skipped");
-  await rm(`${STATE_FILE}.175001.acp.json`, { force: true });
+  return entries;
+};
+
+test("context transform floors at anchor-minus-reclaimed while the anchor predates a successful compress", async () => {
+  const acpFile = `${STATE_FILE}.175000.acp.json`;
+  await rm(acpFile, { force: true });
+  await seedState(acpFile, seedBlock({ compressedTokens: 60_000 }));
+  const { api, handlers } = captureApi();
+  createAcpExtension({ modelContextLimit: 180_000 })(api as any);
+
+  const ctx = fakeCtx(175_000);
+  branchEntries = staleStream();
+  const r = await fire(handlers, branchEntries, ctx);
+  assert.equal(nudgeCount(r), 0, "no false emergency: floor adjusted down by ~60K reclaimed since the anchor");
+  await rm(acpFile, { force: true });
+});
+
+// issue #325 guard: if the compress barely reclaimed anything while the context
+// is already near the limit, the adjusted floor must stay high enough to STILL
+// trip the nudge — never over-suppress a genuinely full context.
+test("context transform still trips the nudge when a stale-anchor compress reclaimed little", async () => {
+  const acpFile = `${STATE_FILE}.174000.acp.json`;
+  await rm(acpFile, { force: true });
+  await seedState(acpFile, seedBlock({ compressedTokens: 1_000 }));
+  const { api, handlers } = captureApi();
+  createAcpExtension({ modelContextLimit: 180_000 })(api as any);
+
+  const ctx = fakeCtx(174_000);
+  branchEntries = staleStream();
+  const r = await fire(handlers, branchEntries, ctx);
+  assert.ok(nudgeCount(r) >= 1, "nudge still fires: only ~1K reclaimed, context is genuinely near the limit");
+  await rm(acpFile, { force: true });
 });