fix: auto-rotation never fired when memory was enabled

src/daemon/context-math.ts

@@ -96,12 +96,26 @@ export function decideRotation(input: RotationDecisionInput): RotationDecision {
     return { shouldRotate: false, reason: "no_signal", occupancy: 0 };
   }
   const occupancy = ctx / W;
-  if (input.numTurns < input.minTurnsBeforeRotate) {
-    return { shouldRotate: false, reason: "below_min_turns", occupancy };
-  }
+  // The hard ceiling is checked FIRST, ahead of the min-turns guard.
+  //
+  // It is the last line of defence before the backend rejects the prompt
+  // outright, and it is documented to fire regardless of the `enabled`
+  // toggle — so letting a *different* guard preempt it made it conditional
+  // in practice. The min-turns window exists to stop churn right after a
+  // rotation (the seed prompt needs a few turns to earn its keep); it was
+  // never meant to license running past the context ceiling. A session that
+  // legitimately reaches 97% inside its first few turns — one big paste, a
+  // wide repo scan — needs the net MORE than a long-running one, not less.
+  //
+  // Ordering it this way also means a stuck/never-advancing turn counter can
+  // no longer disable the net silently, which is exactly how this failed
+  // before (see the counter hoist in Session#recordUsageFromTurn).
   if (occupancy >= input.hardRotatePct) {
     return { shouldRotate: true, reason: "hard_threshold", occupancy };
   }
+  if (input.numTurns < input.minTurnsBeforeRotate) {
+    return { shouldRotate: false, reason: "below_min_turns", occupancy };
+  }
   if (!input.enabled) {
     return { shouldRotate: false, reason: "disabled_below_hard", occupancy };
   }

src/daemon/session.ts

@@ -2691,6 +2691,19 @@ export class Session {
       primaryCacheReadThisTurn = cacheRead; // best we can do on fallback
     }
 
+    // Turns-since-rotation is the min-turns guard's only input, and it is
+    // process-local (never read back from the store), so it MUST advance on
+    // both paths. It used to live inside the `!store` branch below, which
+    // meant that with memory enabled — the common configuration — it stayed
+    // pinned at 0 for the life of the session. `decideRotation` then returned
+    // `below_min_turns` on every check, and because that guard is evaluated
+    // BEFORE the hard-rotate ceiling, it silently disabled auto-rotation
+    // entirely: soft threshold and the "fires even when disabled" safety net
+    // alike. Observed on a 1M session that sat at 999,627 tokens across 52
+    // primary calls, rotated zero times, and then failed the turn outright
+    // with `prompt is too long`.
+    this.#turnsSinceLastRotation += 1;
+
     // If the memory engine isn't enabled we have no durable store — fall
     // back to pure in-memory accumulation so StatusBar still gets usage.
     const store = this.#memory?.store;
@@ -2702,7 +2715,6 @@ export class Session {
       this.#usage.totalCostUsd += result.totalCostUsd;
       this.#usage.durationMs += result.durationMs;
       this.#usage.numTurns += 1;
-      this.#turnsSinceLastRotation += 1;
       // PEAK tracks primary-only — ignore subagent contributions so a
       // subagent-heavy turn doesn't poison the bloat canary.
       this.#usage.peakInputTokens = Math.max(

src/tests/context-math.test.ts

@@ -119,10 +119,13 @@ describe("decideRotation", () => {
     expect(out.reason).toBe("no_signal");
   });
 
-  it("below min-turns guard → no rotation even at high occupancy", () => {
+  it("below min-turns guard → no rotation at elevated (but sub-ceiling) occupancy", () => {
+    // 91%: past the soft threshold, still under the 97% hard ceiling. This is
+    // the guard's actual job — suppress churn in the first few turns after a
+    // rotation, while the seed prompt is still earning its keep.
     const out = decideRotation({
       ...baseInput(),
-      primaryLastTurnContext: 980_000,
+      primaryLastTurnContext: 910_000,
       numTurns: 2,
     });
     expect(out.shouldRotate).toBe(false);
@@ -168,14 +171,36 @@ describe("decideRotation", () => {
     expect(out.reason).toBe("hard_threshold");
   });
 
-  it("hard threshold still respects min-turns (don't rotate fresh sessions)", () => {
+  it("hard threshold PREEMPTS min-turns — the net is unconditional", () => {
+    // Deliberate inversion of the previous behaviour. The ceiling is the last
+    // defence before the backend rejects the prompt outright, so no other
+    // guard may gate it. A session that reaches 97% inside its first turns —
+    // one large paste, a wide repo scan — needs the net more than a
+    // long-running one, not less.
+    //
+    // This ordering also means a stuck turn counter can no longer disable the
+    // net silently, which is precisely how it failed: with memory enabled the
+    // counter never advanced past 0, so `below_min_turns` was returned on
+    // every check and a 999,627-token session rotated zero times.
     const out = decideRotation({
       ...baseInput(),
       numTurns: 1,
       primaryLastTurnContext: 999_999,
     });
-    expect(out.shouldRotate).toBe(false);
-    expect(out.reason).toBe("below_min_turns");
+    expect(out.shouldRotate).toBe(true);
+    expect(out.reason).toBe("hard_threshold");
+  });
+
+  it("a never-advancing turn counter cannot suppress the ceiling", () => {
+    // The exact shape of the bug: numTurns pinned at 0 forever.
+    const out = decideRotation({
+      ...baseInput(),
+      enabled: false,
+      numTurns: 0,
+      primaryLastTurnContext: 999_627, // the observed live value
+    });
+    expect(out.shouldRotate).toBe(true);
+    expect(out.reason).toBe("hard_threshold");
   });
 
   it("the user's 24-turn 214k avg case: NO rotation (healthy)", () => {

src/tests/rotation-counter-guard.test.ts

@@ -0,0 +1,51 @@
+import { describe, test, expect } from "bun:test";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+/**
+ * Guard: the rotation turn-counter must advance on BOTH usage paths.
+ *
+ * `#turnsSinceLastRotation` is the only input to `decideRotation`'s min-turns
+ * guard, and it is process-local — never read back from the store. It used to
+ * be incremented inside the `if (!store)` branch of
+ * `Session#recordUsageFromTurn`, i.e. only when the memory engine was OFF.
+ * With memory enabled (the common configuration) it stayed pinned at 0, so
+ * every rotation check returned `below_min_turns` and auto-rotation was
+ * silently dead — soft threshold and hard ceiling alike.
+ *
+ * That shipped because nothing asserted it. A behavioural test would need a
+ * full daemon + memory store + provider harness for a single integer, so this
+ * checks the structure instead: the increment must appear BEFORE the
+ * `if (!store)` branch it used to hide in. Crude, but it fails loudly on the
+ * one edit that would reintroduce the bug.
+ *
+ * The behavioural half of this fix — that the hard ceiling can no longer be
+ * suppressed by a stuck counter — is covered in `context-math.test.ts`.
+ */
+describe("rotation turn counter", () => {
+  const src = readFileSync(
+    join(import.meta.dir, "..", "daemon", "session.ts"),
+    "utf8",
+  );
+
+  test("is incremented exactly once, outside any store branch", () => {
+    const increments = [...src.matchAll(/#turnsSinceLastRotation\s*\+=\s*1/g)];
+    expect(increments).toHaveLength(1);
+  });
+
+  test("the increment precedes the `if (!store)` fallback branch", () => {
+    const inc = src.indexOf("#turnsSinceLastRotation += 1");
+    const storeBranch = src.indexOf("if (!store) {");
+    expect(inc).toBeGreaterThan(-1);
+    expect(storeBranch).toBeGreaterThan(-1);
+    // Strictly before — inside or after the branch means memory-enabled
+    // sessions stop counting turns and lose auto-rotation entirely.
+    expect(inc).toBeLessThan(storeBranch);
+  });
+
+  test("is reset only by an actual rotation", () => {
+    const resets = [...src.matchAll(/#turnsSinceLastRotation\s*=\s*0/g)];
+    // One field initialiser + one reset inside #rotate().
+    expect(resets).toHaveLength(2);
+  });
+});