feat(coach): carry discovered drivers in the no-tools snapshot

The FDR cross-metric driver pairs were reachable only through the
get_correlations tool, so a local/no-tools provider got the coincident
flag but zero discovered drivers and the cross-metric layer silently
degraded. The system prompt's fallback to a snapshot driver field
pointed at a field that did not exist on that path.

Attach a bounded top-3 slice of the same gated, ranked driver output the
tool serves to the no-tools snapshot floor, gated on the derived layer
and shed first under prompt-budget pressure. Local users now reach
parity on the flagship cross-metric capability.

src/lib/ai/coach/__tests__/correlations-snapshot.test.ts

@@ -0,0 +1,94 @@
+/**
+ * RECON1 (D5-5) — the no-tools snapshot driver block surfaces the SAME gated,
+ * ranked drivers the get_correlations tool serves, bounded to the top N, and
+ * attaches nothing when no driver survives the quality gates.
+ */
+import { describe, expect, it, vi, beforeEach } from "vitest";
+
+const readCoachCorrelations = vi.fn();
+vi.mock("@/lib/ai/coach/tools/correlations-read", () => ({
+  readCoachCorrelations: (userId: string) => readCoachCorrelations(userId),
+}));
+
+import {
+  buildCorrelationsSnapshotBlock,
+  SNAPSHOT_DRIVER_CAP,
+} from "@/lib/ai/coach/correlations-snapshot";
+import type { CoachCorrelationDriver } from "@/lib/ai/coach/tools/correlations-read";
+
+function driver(
+  behaviour: string,
+  outcome: string,
+  r: number,
+): CoachCorrelationDriver {
+  return {
+    behaviour,
+    outcome,
+    direction: r >= 0 ? "higher" : "lower",
+    lagDays: 1,
+    n: 42,
+    r,
+    note: `Higher ${behaviour} tends to go with ${outcome} — not a cause.`,
+  };
+}
+
+describe("buildCorrelationsSnapshotBlock (D5-5)", () => {
+  beforeEach(() => {
+    readCoachCorrelations.mockReset();
+  });
+
+  it("carries driver pairs when the engine surfaces them", async () => {
+    readCoachCorrelations.mockResolvedValue({
+      present: true,
+      drivers: [
+        driver("time in daylight", "sleep duration", 0.41),
+        driver("mood", "resting heart rate", -0.33),
+      ],
+      pairsTested: 16,
+      windowDays: 180,
+    });
+    const block = await buildCorrelationsSnapshotBlock("user-1");
+    expect(block).not.toBeNull();
+    expect(block!.drivers).toHaveLength(2);
+    expect(block!.drivers[0].behaviour).toBe("time in daylight");
+    expect(block!.pairsTested).toBe(16);
+    expect(block!.windowDays).toBe(180);
+  });
+
+  it("bounds the block to the top N ranked drivers", async () => {
+    const many = Array.from({ length: SNAPSHOT_DRIVER_CAP + 4 }, (_, i) =>
+      driver(`behaviour ${i}`, "sleep duration", 0.5 - i * 0.02),
+    );
+    readCoachCorrelations.mockResolvedValue({
+      present: true,
+      drivers: many,
+      pairsTested: 30,
+      windowDays: 180,
+    });
+    const block = await buildCorrelationsSnapshotBlock("user-1");
+    expect(block!.drivers).toHaveLength(SNAPSHOT_DRIVER_CAP);
+    // Order preserved from the already-ranked tool output (highest effect first).
+    expect(block!.drivers[0].behaviour).toBe("behaviour 0");
+  });
+
+  it("attaches nothing when no driver survives the quality gates", async () => {
+    readCoachCorrelations.mockResolvedValue({
+      present: false,
+      reason: "no_significant_pattern",
+    });
+    expect(await buildCorrelationsSnapshotBlock("user-1")).toBeNull();
+  });
+
+  it("attaches nothing when present but the driver list is empty (coincident-only)", async () => {
+    // The reader can be present purely for the coincident flag with zero
+    // discovered drivers — the snapshot floor adds the driver layer only.
+    readCoachCorrelations.mockResolvedValue({
+      present: true,
+      drivers: [],
+      coincident: { fired: true, contributing: [], day: "2026-06-26" },
+      pairsTested: 12,
+      windowDays: 180,
+    });
+    expect(await buildCorrelationsSnapshotBlock("user-1")).toBeNull();
+  });
+});

src/lib/ai/coach/correlations-snapshot.ts

@@ -0,0 +1,62 @@
+/**
+ * RECON1 (D5-5) — discovered-driver block for the no-tools Coach snapshot.
+ *
+ * The FDR-controlled cross-metric driver pairs were reachable ONLY via the
+ * `get_correlations` tool, so a local / no-tools provider (Ollama) got the
+ * coincident-deviation flag but ZERO discovered drivers — the differentiating
+ * cross-metric layer silently degraded, and system-prompt rule 14's fallback
+ * clause ("any correlation/driver field the SNAPSHOT carries") pointed at a
+ * field that did not exist on the no-tools path.
+ *
+ * This block closes that gap by attaching a BOUNDED slice of the SAME gated,
+ * ranked output the tool serves — `readCoachCorrelations` runs the identical
+ * discovery scan + quality gates (effect-size floor, family-tautology
+ * exclusion, sample-size shrinkage, confidence tiering), so a local user sees
+ * exactly the quality-filtered drivers a cloud user's tool would. We keep only
+ * the top few by ranked effect so the no-tools prompt stays compact.
+ *
+ * Server-only — `readCoachCorrelations` reads `@/lib/db`. Fail-soft: a null
+ * return (no surviving driver / read hiccup) attaches nothing.
+ */
+import {
+  readCoachCorrelations,
+  type CoachCorrelationDriver,
+} from "./tools/correlations-read";
+
+/** How many ranked drivers reach the no-tools snapshot floor. */
+export const SNAPSHOT_DRIVER_CAP = 3;
+
+/** One compact driver line for the snapshot — descriptive, never causal. */
+export interface CorrelationsSnapshotBlock {
+  /** Top discovered drivers by ranked effect, capped + descriptive. */
+  drivers: CoachCorrelationDriver[];
+  /** How many behaviour×outcome pairs were tested (honest footer). */
+  pairsTested: number;
+  /** Trailing-day window the discovery scanned. */
+  windowDays: number;
+}
+
+/**
+ * Build the bounded discovered-driver block for the no-tools snapshot floor, or
+ * `null` when no driver survives the quality gates (or the read fails). The
+ * coincident flag is intentionally NOT duplicated here — the derived block
+ * already carries it; this block adds only the discovered-driver layer the
+ * no-tools path was missing.
+ */
+export async function buildCorrelationsSnapshotBlock(
+  userId: string,
+): Promise<CorrelationsSnapshotBlock | null> {
+  const result = await readCoachCorrelations(userId);
+  if (!result.present || !result.drivers || result.drivers.length === 0) {
+    return null;
+  }
+  // `result.drivers` arrives already ranked by the discovery engine (shrunk
+  // effect magnitude, q as tie-break) and already gated (below-floor pairs
+  // dropped, tautologies excluded) — so the top-N slice is the highest-signal
+  // quality-filtered drivers, identical to what the tool path would surface.
+  return {
+    drivers: result.drivers.slice(0, SNAPSHOT_DRIVER_CAP),
+    pairsTested: result.pairsTested ?? 0,
+    windowDays: result.windowDays ?? 0,
+  };
+}

src/lib/ai/coach/snapshot.ts

@@ -46,6 +46,7 @@ import { annotate } from "@/lib/logging/context";
 import { memoizePerRequest } from "@/lib/request-cache";
 import { buildGlp1SnapshotBlock } from "./glp1-snapshot";
 import { buildDerivedSnapshotBlock } from "./derived-snapshot";
+import { buildCorrelationsSnapshotBlock } from "./correlations-snapshot";
 import { buildCoachMemoryBlock } from "./memory-snapshot";
 import { buildTrajectorySnapshotBlock } from "./trajectory-snapshot";
 import { buildCycleSnapshotBlock } from "./cycle-snapshot";
@@ -1259,6 +1260,16 @@ async function buildCoachSnapshotImpl(
   const trajectoryBlockPromise = derivedActive
     ? buildTrajectorySnapshotBlock(userId, derivedProfile, now)
     : null;
+  // RECON1 (D5-5) — discovered cross-metric driver pairs for the no-tools
+  // snapshot floor. Reuses the SAME gated/ranked output the get_correlations
+  // tool serves (effect-size floor + family-tautology exclusion + shrinkage +
+  // confidence tiering already applied inside the discovery engine), so a
+  // local/no-tools provider reaches parity on the flagship cross-metric layer
+  // instead of getting only the coincident flag. Gated on `derivedActive` (it
+  // is the recovery / cross-metric layer) and fail-soft to null.
+  const correlationsBlockPromise = derivedActive
+    ? buildCorrelationsSnapshotBlock(userId)
+    : null;
   const memoryBlockPromise = buildCoachMemoryBlock(
     userId,
     derivedProfile,
@@ -1305,6 +1316,7 @@ async function buildCoachSnapshotImpl(
     derivedBlock,
     dayStrainRows,
     trajectoryBlock,
+    correlationsBlock,
     memoryBlock,
     cycleBlock,
     illnessBlock,
@@ -1320,6 +1332,7 @@ async function buildCoachSnapshotImpl(
     derivedBlockPromise,
     dayStrainRowsPromise,
     trajectoryBlockPromise,
+    correlationsBlockPromise,
     memoryBlockPromise,
     cycleBlockPromise,
     illnessBlockPromise,
@@ -2269,6 +2282,20 @@ async function buildCoachSnapshotImpl(
       snapshot.trajectory = trajectoryBlock;
       registerBlock("trajectory", "skin_temp");
     }
+
+    // ── RECON1 (D5-5) — discovered cross-metric drivers ──────────────────
+    // The bounded top-N driver pairs (post quality-gate, post-rank) from the
+    // SAME engine the get_correlations tool reads, attached so the no-tools /
+    // local-provider path narrates the cross-metric layer it was missing —
+    // closing the parity gap with the tool path and making system-prompt rule
+    // 14's "any driver field the SNAPSHOT carries" fallback real. Descriptive,
+    // never causal. Registered against the lowest-priority `skin_temp`
+    // (environment) cluster so the budget degrader sheds it before any
+    // clinical block under prompt-budget pressure.
+    if (correlationsBlock) {
+      snapshot.correlations = correlationsBlock;
+      registerBlock("correlations", "skin_temp");
+    }
   }
 
   // ── v1.11.0 W5a — rolling-profile memory (Pillar P2 2a) ──────────────