diff --git a/src/app/api/insights/chat/__tests__/route-tool-mode.test.ts b/src/app/api/insights/chat/__tests__/route-tool-mode.test.ts
index d8b95d743..3f4a1e17d 100644
--- a/src/app/api/insights/chat/__tests__/route-tool-mode.test.ts
+++ b/src/app/api/insights/chat/__tests__/route-tool-mode.test.ts
@@ -154,6 +154,7 @@ const { buildCoachDataInventory, renderDataInventory, runCoachToolLoop } =
       totalTokens: 80,
       rounds: 2,
       toolTrace: [{ name: "get_metric_series", present: true }],
+      toolResults: [],
     })),
   }));
 vi.mock("@/lib/ai/coach/tools", () => ({
@@ -183,6 +184,9 @@ vi.mock("@/lib/validations/coach-prefs", () => ({
 }));
 
 const { appendMessage } = await import("@/lib/ai/coach/persistence");
+const { parseKeyValuesSentinel } = await import("@/lib/ai/coach/keyvalues");
+const { parseSuggestReminder } =
+  await import("@/lib/ai/coach/suggest-reminder");
 
 vi.mock("@/lib/sse/create-stream", () => ({
   createSseStream: (
@@ -260,6 +264,50 @@ describe("coach chat — tool-mode routing (F1)", () => {
     ).toEqual([{ name: "get_metric_series", present: true }]);
   });
 
+  it("soft-strips a prose number the tools never returned (P6)", async () => {
+    resolveProviderChain.mockResolvedValue([
+      { providerType: "anthropic", instance: {} },
+    ]);
+    // Echo the real prose through the sentinel + suggest parsers so the
+    // verifier sees the model's actual numbers (the default mocks return a
+    // fixed string).
+    const drift = "Your systolic averaged about 138 lately.";
+    (parseKeyValuesSentinel as ReturnType<typeof vi.fn>).mockReturnValue({
+      prose: drift,
+      keyValues: [],
+      malformed: false,
+      malformedEntries: [],
+    });
+    (parseSuggestReminder as ReturnType<typeof vi.fn>).mockReturnValue({
+      prose: drift,
+    });
+    // The tool returned systolic 128; the prose drifts to 138.
+    (runCoachToolLoop as ReturnType<typeof vi.fn>).mockImplementation(
+      async () => ({
+        result: {
+          content: "Your systolic averaged about 138 lately.",
+          tokensUsed: 80,
+          model: "m",
+        },
+        workingProviderType: "anthropic",
+        totalTokens: 80,
+        rounds: 2,
+        toolTrace: [{ name: "get_metric_series", present: true }],
+        toolResults: [
+          { present: true, data: { aggregate: { avgSys30: 128 } } },
+        ],
+      }),
+    );
+    await post(chatReq({ message: "How is my BP?" }));
+    const calls = (appendMessage as ReturnType<typeof vi.fn>).mock.calls;
+    const assistantCall = calls.find(
+      (c) => (c[0] as { role: string }).role === "assistant",
+    );
+    const content = (assistantCall?.[0] as { content: string }).content;
+    expect(content).toContain("[unverified]");
+    expect(content).not.toContain("138");
+  });
+
   it("falls back to the snapshot-stuffing path when a provider lacks tools", async () => {
     resolveProviderChain.mockResolvedValue([
       { providerType: "anthropic", instance: {} },
diff --git a/src/app/api/insights/chat/route.ts b/src/app/api/insights/chat/route.ts
index 341476274..9fca7a8d8 100644
--- a/src/app/api/insights/chat/route.ts
+++ b/src/app/api/insights/chat/route.ts
@@ -84,6 +84,10 @@ import {
 } from "@/lib/ai/coach/tools";
 import type { AiMessage } from "@/lib/ai/types";
 import { parseKeyValuesSentinel } from "@/lib/ai/coach/keyvalues";
+import {
+  findUnverifiedCoachNumbers,
+  stripUnverifiedNumbers,
+} from "@/lib/ai/coach/coach-prose-grounding";
 import { parseSuggestReminder } from "@/lib/ai/coach/suggest-reminder";
 import { gateSuggestion } from "@/lib/ai/coach/suggest-gate";
 import {
@@ -518,6 +522,9 @@ Reply now as the assistant, in ${locale === "de" ? "German" : "English"}.`;
   let result: CompletionResult;
   let workingProviderType: string;
   let toolTrace: CoachToolTrace[] = [];
+  // v1.21.0 (P6) — the present tool-result payloads this turn, for the post-hoc
+  // prose number-verifier. Empty on the no-tools path.
+  let toolResultPayloads: unknown[] = [];
   let totalTokensSpent: number;
   try {
     if (toolMode) {
@@ -556,6 +563,7 @@ Reply now as the assistant, in ${locale === "de" ? "German" : "English"}. Fetch
       result = loop.result;
       workingProviderType = loop.workingProviderType;
       toolTrace = loop.toolTrace;
+      toolResultPayloads = (loop.toolResults ?? []).map((r) => r.data);
       totalTokensSpent = loop.totalTokens;
     } else {
       const fallback = await runRawCompletionWithFallback({
@@ -701,6 +709,38 @@ Reply now as the assistant, in ${locale === "de" ? "German" : "English"}. Fetch
     });
   }
 
+  // v1.21.0 (P6 / C2-5) — post-hoc numeric verifier on the Coach prose. On the
+  // tool path, cross-check every number the model cited against the figures the
+  // tools actually returned this turn; an unmatched number (transcription /
+  // paraphrase drift) is soft-stripped to "[unverified]" and annotated. Cheap,
+  // non-blocking, and a no-op when no tool returned figures (a qualitative turn
+  // or the no-tools path) — the prompt-level grounding rule remains the
+  // backstop there, exactly like the briefing's "no signals → skip". A blocked
+  // turn already carries canned fallback prose, so skip it.
+  if (!outbound.block && toolResultPayloads.length > 0) {
+    const unverified = findUnverifiedCoachNumbers(
+      replyText,
+      toolResultPayloads,
+    );
+    if (unverified.length > 0) {
+      const { prose: corrected, stripped } = stripUnverifiedNumbers(
+        replyText,
+        unverified,
+      );
+      replyText = corrected;
+      annotate({
+        action: { name: "coach.prose.number_unverified" },
+        meta: {
+          flagged: unverified.length,
+          stripped,
+          // No raw values — just the count + truncated tokens for ops triage.
+          tokens: unverified.slice(0, 6).map((u) => u.source),
+          promptVersion: PROMPT_VERSION,
+        },
+      });
+    }
+  }
+
   let surfacedSuggestion: CoachSuggestion | null = null;
   if (!outbound.block && suggestParse.cadence) {
     const decision = await gateSuggestion({
diff --git a/src/lib/ai/coach/__tests__/coach-prose-grounding.test.ts b/src/lib/ai/coach/__tests__/coach-prose-grounding.test.ts
new file mode 100644
index 000000000..c6a61a988
--- /dev/null
+++ b/src/lib/ai/coach/__tests__/coach-prose-grounding.test.ts
@@ -0,0 +1,89 @@
+/**
+ * v1.21.0 (P6 / C2-5) — post-hoc numeric verifier on Coach prose. It must flag
+ * a number the model cited that no tool returned this turn (transcription
+ * drift), exempt structural window/ordinal integers, and no-op when no tool
+ * returned figures. Soft-strip replaces only the flagged tokens.
+ */
+import { describe, expect, it } from "vitest";
+
+import {
+  collectNumericLeaves,
+  findUnverifiedCoachNumbers,
+  stripUnverifiedNumbers,
+} from "@/lib/ai/coach/coach-prose-grounding";
+
+describe("collectNumericLeaves", () => {
+  it("walks numbers, numeric strings, arrays and nested objects", () => {
+    const out = new Set<number>();
+    collectNumericLeaves(
+      {
+        section: { avgSys30: 128, label: "LDL", value: "120" },
+        recent: [{ v: 72 }, { v: "1.2" }],
+      },
+      out,
+    );
+    expect(out.has(128)).toBe(true);
+    expect(out.has(120)).toBe(true);
+    expect(out.has(72)).toBe(true);
+    expect(out.has(1.2)).toBe(true);
+  });
+});
+
+describe("findUnverifiedCoachNumbers", () => {
+  const payloads = [{ aggregate: { avgSys30: 128, avgDia30: 82 } }];
+
+  it("returns nothing when every cited number is grounded", () => {
+    const prose =
+      "Your systolic averaged 128 and diastolic 82 over the last 30 days.";
+    expect(findUnverifiedCoachNumbers(prose, payloads)).toEqual([]);
+  });
+
+  it("flags a drifted number the tools never returned", () => {
+    const prose = "Your systolic averaged about 138 recently.";
+    const findings = findUnverifiedCoachNumbers(prose, payloads);
+    expect(findings).toHaveLength(1);
+    expect(findings[0].value).toBe(138);
+  });
+
+  it("allows a rounding within tolerance", () => {
+    const prose = "Diastolic sat around 82.0 this period.";
+    expect(findUnverifiedCoachNumbers(prose, payloads)).toEqual([]);
+  });
+
+  it("exempts structural window + small-ordinal integers", () => {
+    const prose = "Over the last 30 days, 2 readings stood out of 7 total.";
+    // 30 + 7 are window integers; 2 is a small ordinal — none graded.
+    const findings = findUnverifiedCoachNumbers(prose, [{ x: 999 }]);
+    expect(findings).toEqual([]);
+  });
+
+  it("no-ops when no tool returned any figure", () => {
+    const prose = "Your systolic averaged 138 recently.";
+    expect(findUnverifiedCoachNumbers(prose, [])).toEqual([]);
+    expect(
+      findUnverifiedCoachNumbers(prose, [{ note: "no numbers here" }]),
+    ).toEqual([]);
+  });
+
+  it("returns empty on empty prose", () => {
+    expect(findUnverifiedCoachNumbers("", payloads)).toEqual([]);
+  });
+});
+
+describe("stripUnverifiedNumbers", () => {
+  it("replaces only the flagged tokens, leaving grounded numbers intact", () => {
+    const prose = "Systolic 128, but it spiked to 138 yesterday.";
+    const findings = [{ value: 138, source: "138" }];
+    const { prose: out, stripped } = stripUnverifiedNumbers(prose, findings);
+    expect(stripped).toBe(1);
+    expect(out).toContain("128");
+    expect(out).toContain("[unverified]");
+    expect(out).not.toContain("138");
+  });
+
+  it("is a no-op when nothing was flagged", () => {
+    const { prose, stripped } = stripUnverifiedNumbers("all good", []);
+    expect(prose).toBe("all good");
+    expect(stripped).toBe(0);
+  });
+});
diff --git a/src/lib/ai/coach/__tests__/correlations-read.test.ts b/src/lib/ai/coach/__tests__/correlations-read.test.ts
new file mode 100644
index 000000000..b6e813f83
--- /dev/null
+++ b/src/lib/ai/coach/__tests__/correlations-read.test.ts
@@ -0,0 +1,146 @@
+/**
+ * v1.21.0 (C3) — the Coach correlations reader surfaces the deterministic FDR
+ * discovery + coincident-deviation flag, returns descriptive driver rows, and
+ * degrades to a clean { present: false } when nothing survives or a read fails.
+ */
+import { describe, expect, it, vi, beforeEach } from "vitest";
+
+const measurementFindMany = vi.fn();
+const moodFindMany = vi.fn();
+const userFindUnique = vi.fn();
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    measurement: { findMany: (a: unknown) => measurementFindMany(a) },
+    moodEntry: { findMany: (a: unknown) => moodFindMany(a) },
+    user: { findUnique: (a: unknown) => userFindUnique(a) },
+  },
+}));
+
+const loadBaselineProfile = vi.fn();
+const computeCoincidentDeviation = vi.fn();
+vi.mock("@/lib/insights/derived", async (importOriginal) => {
+  const actual =
+    await importOriginal<typeof import("@/lib/insights/derived")>();
+  return {
+    ...actual,
+    loadBaselineProfile: () => loadBaselineProfile(),
+    computeCoincidentDeviation: () => computeCoincidentDeviation(),
+  };
+});
+
+const discoverCorrelations = vi.fn();
+vi.mock("@/lib/insights/correlation-discovery", async (importOriginal) => {
+  const actual =
+    await importOriginal<
+      typeof import("@/lib/insights/correlation-discovery")
+    >();
+  return { ...actual, discoverCorrelations: () => discoverCorrelations() };
+});
+
+import { readCoachCorrelations } from "@/lib/ai/coach/tools/correlations-read";
+
+describe("readCoachCorrelations", () => {
+  beforeEach(() => {
+    measurementFindMany.mockReset().mockResolvedValue([]);
+    moodFindMany.mockReset().mockResolvedValue([]);
+    userFindUnique.mockReset().mockResolvedValue({ timezone: "Europe/Berlin" });
+    loadBaselineProfile
+      .mockReset()
+      .mockResolvedValue({ ageYears: 40, sex: "MALE", heightCm: 180 });
+    computeCoincidentDeviation.mockReset().mockResolvedValue(null);
+    discoverCorrelations.mockReset();
+  });
+
+  it("returns descriptive drivers when pairs survive", async () => {
+    discoverCorrelations.mockReturnValue({
+      discovered: [
+        {
+          behaviour: "TIME_IN_DAYLIGHT",
+          outcome: "SLEEP_DURATION",
+          n: 42,
+          r: 0.34,
+          pValue: 0.001,
+          qValue: 0.02,
+          interpretation:
+            "Higher time in daylight tends to go with higher next-day sleep duration in your data — a pattern worth watching, not a cause.",
+          lagDays: 1,
+        },
+      ],
+      pairsTested: 18,
+      fdrQ: 0.1,
+      minPairs: 20,
+    });
+    const result = await readCoachCorrelations("u1");
+    expect(result.present).toBe(true);
+    expect(result.drivers).toHaveLength(1);
+    expect(result.drivers?.[0]).toMatchObject({
+      behaviour: "time in daylight",
+      outcome: "sleep duration",
+      direction: "higher",
+      lagDays: 1,
+      n: 42,
+    });
+    expect(result.pairsTested).toBe(18);
+  });
+
+  it("returns present:false when nothing survives and no coincident flag", async () => {
+    discoverCorrelations.mockReturnValue({
+      discovered: [],
+      pairsTested: 4,
+      fdrQ: 0.1,
+      minPairs: 20,
+    });
+    const result = await readCoachCorrelations("u1");
+    expect(result.present).toBe(false);
+    expect(result.reason).toBe("no_significant_pattern");
+  });
+
+  it("surfaces a fired coincident flag even without drivers", async () => {
+    discoverCorrelations.mockReturnValue({
+      discovered: [],
+      pairsTested: 4,
+      fdrQ: 0.1,
+      minPairs: 20,
+    });
+    computeCoincidentDeviation.mockResolvedValue({
+      status: "ok",
+      value: {
+        fired: true,
+        vitals: [],
+        contributing: [
+          { type: "RESTING_HEART_RATE", direction: "above" },
+          { type: "HEART_RATE_VARIABILITY", direction: "below" },
+        ],
+        day: "2026-06-02",
+        illnessExplained: false,
+      },
+      coverage: {
+        requiredInputs: 2,
+        presentInputs: 2,
+        historyDays: 30,
+        missing: [],
+      },
+      confidence: { score: 80, band: "high" },
+      provenance: {
+        inputs: [],
+        source: "DAY",
+        windowDays: 30,
+        computedAt: "x",
+      },
+    });
+    const result = await readCoachCorrelations("u1");
+    expect(result.present).toBe(true);
+    expect(result.coincident?.fired).toBe(true);
+    expect(result.coincident?.contributing).toEqual([
+      { metric: "resting heart rate", direction: "above" },
+      { metric: "heart rate variability", direction: "below" },
+    ]);
+  });
+
+  it("degrades to present:false on a read failure", async () => {
+    loadBaselineProfile.mockRejectedValue(new Error("db down"));
+    const result = await readCoachCorrelations("u1");
+    expect(result.present).toBe(false);
+    expect(result.reason).toBe("retrieval_failed");
+  });
+});
diff --git a/src/lib/ai/coach/__tests__/tools-executor.test.ts b/src/lib/ai/coach/__tests__/tools-executor.test.ts
index 9b7e96c87..e4edce158 100644
--- a/src/lib/ai/coach/__tests__/tools-executor.test.ts
+++ b/src/lib/ai/coach/__tests__/tools-executor.test.ts
@@ -16,6 +16,11 @@ vi.mock("@/lib/ai/coach/snapshot", () => ({
     buildCoachSnapshot(userId, scope),
 }));
 
+const readCoachCorrelations = vi.fn();
+vi.mock("@/lib/ai/coach/tools/correlations-read", () => ({
+  readCoachCorrelations: (userId: string) => readCoachCorrelations(userId),
+}));
+
 import { executeCoachTool } from "@/lib/ai/coach/tools/executor";
 
 function snapshot(
@@ -33,6 +38,7 @@ function snapshot(
 describe("executeCoachTool", () => {
   beforeEach(() => {
     buildCoachSnapshot.mockReset();
+    readCoachCorrelations.mockReset();
   });
 
   it("returns the matching section for get_metric_series when present", async () => {
@@ -182,6 +188,104 @@ describe("executeCoachTool", () => {
     expect(miss.reason).toBe("analyte_not_found");
   });
 
+  it("returns the workouts section for get_workouts when present", async () => {
+    buildCoachSnapshot.mockResolvedValue(
+      snapshot({ workouts: { recent: [{ sport: "RUN" }], totalInWindow: 3 } }),
+    );
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_workouts",
+      rawArguments: JSON.stringify({ window: "last30days" }),
+    });
+    expect(result.present).toBe(true);
+    expect(result.data).toMatchObject({ totalInWindow: 3 });
+  });
+
+  it("returns { present: false } for get_workouts when no block", async () => {
+    buildCoachSnapshot.mockResolvedValue(snapshot({}));
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_workouts",
+      rawArguments: "{}",
+    });
+    expect(result.present).toBe(false);
+    expect(result.reason).toBe("no_data");
+  });
+
+  it("returns the cycle section for get_cycle when present", async () => {
+    buildCoachSnapshot.mockResolvedValue(
+      snapshot({ cycle: { phase: "luteal", dayOfCycle: 21 } }),
+    );
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_cycle",
+      rawArguments: "{}",
+    });
+    expect(result.present).toBe(true);
+    expect(result.data).toMatchObject({ phase: "luteal" });
+  });
+
+  it("returns { present: false } for get_cycle when cycle tracking is off", async () => {
+    // A non-cycle account produces no cycle block (gated in the builder).
+    buildCoachSnapshot.mockResolvedValue(snapshot({}));
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_cycle",
+      rawArguments: "{}",
+    });
+    expect(result.present).toBe(false);
+    expect(result.reason).toBe("no_data");
+  });
+
+  it("surfaces discovered drivers + coincident flag for get_correlations", async () => {
+    readCoachCorrelations.mockResolvedValue({
+      present: true,
+      drivers: [
+        {
+          behaviour: "time in daylight",
+          outcome: "sleep duration",
+          direction: "higher",
+          lagDays: 1,
+          n: 42,
+          r: 0.31,
+          note: "Higher time in daylight tends to go with higher next-day sleep duration in your data — a pattern worth watching, not a cause.",
+        },
+      ],
+      coincident: {
+        fired: false,
+        contributing: [],
+        day: "2026-06-02",
+        illnessExplained: false,
+      },
+      pairsTested: 18,
+      windowDays: 180,
+    });
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_correlations",
+      rawArguments: "{}",
+    });
+    expect(result.present).toBe(true);
+    expect(result.data).toMatchObject({
+      drivers: [{ behaviour: "time in daylight", n: 42 }],
+      pairsTested: 18,
+    });
+  });
+
+  it("returns a clean { present: false } for get_correlations on no pattern", async () => {
+    readCoachCorrelations.mockResolvedValue({
+      present: false,
+      reason: "no_significant_pattern",
+    });
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_correlations",
+      rawArguments: "{}",
+    });
+    expect(result.present).toBe(false);
+    expect(result.reason).toBe("no_significant_pattern");
+  });
+
   it("never passes userId as a tool argument (read from session only)", async () => {
     buildCoachSnapshot.mockResolvedValue(snapshot({}));
     // A crafted argument trying to smuggle a userId must be rejected by the
diff --git a/src/lib/ai/coach/__tests__/tools-inventory.test.ts b/src/lib/ai/coach/__tests__/tools-inventory.test.ts
index 8387dfd08..d2cfa9675 100644
--- a/src/lib/ai/coach/__tests__/tools-inventory.test.ts
+++ b/src/lib/ai/coach/__tests__/tools-inventory.test.ts
@@ -67,6 +67,50 @@ describe("buildCoachDataInventory", () => {
     expect(sleep?.present).toBe(false);
   });
 
+  it("advertises workouts + correlations tools and the cycle tool when enabled", async () => {
+    buildCoachSnapshot.mockResolvedValue(
+      snapshot(
+        {
+          workouts: { recent: [], totalInWindow: 4 },
+          mood: {},
+          cycle: { phase: "luteal" },
+          scope: { window: "last30days" },
+        },
+        { workouts: 4 },
+      ),
+    );
+    isCycleAvailableForUser.mockResolvedValue(true);
+    const inv = await buildCoachDataInventory("u1", undefined);
+    const workouts = inv.entries.find((e) => e.tool === "get_workouts");
+    expect(workouts).toMatchObject({ present: true, count: 4 });
+    const correlations = inv.entries.find((e) => e.tool === "get_correlations");
+    expect(correlations?.present).toBe(true); // mood present → correlatable
+    const cycle = inv.entries.find((e) => e.tool === "get_cycle");
+    expect(cycle).toMatchObject({ present: true });
+  });
+
+  it("omits the cycle line when cycle tracking is unavailable", async () => {
+    buildCoachSnapshot.mockResolvedValue(snapshot({ bloodPressure: {} }));
+    isCycleAvailableForUser.mockResolvedValue(false);
+    const inv = await buildCoachDataInventory("u1", undefined);
+    expect(inv.entries.find((e) => e.tool === "get_cycle")).toBeUndefined();
+  });
+
+  it("probes a wide source set so synced domains are advertised", async () => {
+    // body composition + spo2 present even though they are not default clusters.
+    buildCoachSnapshot.mockResolvedValue(
+      snapshot(
+        { bodyFat: {}, oxygenSaturation: {}, scope: { window: "last30days" } },
+        { body_fat: 12, spo2: 30 },
+      ),
+    );
+    const inv = await buildCoachDataInventory("u1", undefined);
+    const bodyFat = inv.entries.find((e) => e.metric === "body_fat");
+    const spo2 = inv.entries.find((e) => e.metric === "spo2");
+    expect(bodyFat).toMatchObject({ present: true, count: 12 });
+    expect(spo2).toMatchObject({ present: true, count: 30 });
+  });
+
   it("reports restMode + cycleEnabled", async () => {
     buildCoachSnapshot.mockResolvedValue(
       snapshot({ illness: { restMode: true } }),
diff --git a/src/lib/ai/coach/__tests__/tools-loop.test.ts b/src/lib/ai/coach/__tests__/tools-loop.test.ts
index 7e70c3499..3c4586224 100644
--- a/src/lib/ai/coach/__tests__/tools-loop.test.ts
+++ b/src/lib/ai/coach/__tests__/tools-loop.test.ts
@@ -86,6 +86,9 @@ describe("runCoachToolLoop", () => {
     expect(out.toolTrace).toEqual([
       { name: "get_metric_series", present: true },
     ]);
+    // v1.21.0 (P6) — the present result's payload is retained for the prose
+    // number-verifier.
+    expect(out.toolResults).toEqual([{ present: true, data: { x: 1 } }]);
     // The second call must forbid tools? No — round 2 still offers them
     // (round <= MAX_ROUNDS). It simply chose to answer.
     expect(runRawCompletionWithFallback).toHaveBeenCalledTimes(2);
diff --git a/src/lib/ai/coach/coach-prose-grounding.ts b/src/lib/ai/coach/coach-prose-grounding.ts
new file mode 100644
index 000000000..0772e83b8
--- /dev/null
+++ b/src/lib/ai/coach/coach-prose-grounding.ts
@@ -0,0 +1,153 @@
+/**
+ * v1.21.0 (P6 / C2-5) — post-hoc numeric verifier for Coach prose.
+ *
+ * The Daily Briefing strips any number absent from the server-computed
+ * `signalsOfDay` block (`@/lib/ai/briefing-grounding`). The Coach's TOOL path
+ * had no equivalent: the addendum forbids citing un-fetched figures, but
+ * nothing deterministically checks the FINAL prose against the figures the
+ * tools actually returned this turn — so a transcription/paraphrase drift
+ * (tool says systolic 128, prose says "~138") could ship.
+ *
+ * This module closes that gap the same way, scoped to the tool path:
+ *   1. Collect every numeric leaf from this turn's PRESENT `CoachToolResult`
+ *      data payloads — the authoritative figure set.
+ *   2. Extract every number the model's prose asserts (reusing the briefing
+ *      verifier's `extractNumbers`).
+ *   3. Flag any prose number that matches no authoritative figure within a
+ *      rounding tolerance, exempting the structural integers (window lengths,
+ *      small ordinals) the briefing verifier already exempts.
+ *
+ * Posture: NON-BLOCKING and cheap. The caller annotates
+ * `coach.prose.number_unverified` and may SOFT-STRIP the unverified figure
+ * from the prose (replacing the bare token with a neutral placeholder) — it
+ * never hard-fails the user's turn. When NO tool returned figures (a
+ * qualitative answer, or the no-tools path) there is no authoritative set to
+ * grade against, so the check no-ops and the prompt-level grounding rule
+ * remains the backstop, exactly like the briefing's "no signals → skip".
+ */
+import { extractNumbers } from "@/lib/ai/briefing-grounding";
+
+/** Absolute + relative tolerance — identical basis to the briefing verifier. */
+const ABS_TOLERANCE = 0.15;
+const REL_TOLERANCE = 0.02;
+
+/**
+ * Window lengths + small ordinals the prose uses structurally ("last 7 days",
+ * "2 of your vitals", "3 readings") — never graded, to avoid false positives on
+ * honest framing. Mirrors the briefing verifier's exemption set.
+ */
+const STRUCTURAL_INTEGERS = new Set([7, 14, 30, 31, 90, 180, 365]);
+
+function isStructural(value: number, raw: string): boolean {
+  if (raw.includes(".") || raw.includes(",")) return false;
+  if (!Number.isInteger(value)) return false;
+  const abs = Math.abs(value);
+  if (abs <= 3) return true;
+  return STRUCTURAL_INTEGERS.has(abs);
+}
+
+/** One prose number that matched no figure any tool returned this turn. */
+export interface UnverifiedCoachNumber {
+  /** The numeric value the model wrote, as parsed. */
+  value: number;
+  /** The raw token the value was read from (truncated). */
+  source: string;
+}
+
+/**
+ * Recursively collect every finite numeric leaf from a tool-result payload —
+ * numbers, and numeric strings ("128", "1.2"). Both forms appear in the
+ * snapshot sections (a mean may be a number; a lab value a string). The set is
+ * deliberately broad so a legitimately-cited figure never trips the verifier;
+ * the verifier's job is only to catch a number the model invented or mis-copied.
+ */
+export function collectNumericLeaves(value: unknown, out: Set<number>): void {
+  if (value === null || value === undefined) return;
+  if (typeof value === "number") {
+    if (Number.isFinite(value)) out.add(value);
+    return;
+  }
+  if (typeof value === "string") {
+    // A scalar numeric string ("128", "-1.2", "92%") — pull its magnitudes.
+    for (const { value: n } of extractNumbers(value)) out.add(n);
+    return;
+  }
+  if (Array.isArray(value)) {
+    for (const item of value) collectNumericLeaves(item, out);
+    return;
+  }
+  if (typeof value === "object") {
+    for (const v of Object.values(value as Record<string, unknown>)) {
+      collectNumericLeaves(v, out);
+    }
+  }
+}
+
+/** True when `value` matches any authoritative figure within tolerance. */
+function isGrounded(
+  value: number,
+  authoritative: ReadonlySet<number>,
+): boolean {
+  for (const a of authoritative) {
+    const tol = Math.max(ABS_TOLERANCE, Math.abs(a) * REL_TOLERANCE);
+    if (Math.abs(value - a) <= tol) return true;
+  }
+  return false;
+}
+
+/**
+ * Find every number the Coach prose asserts that does not trace to a figure
+ * returned by a tool this turn. Returns an empty array when there is no prose,
+ * no authoritative figure set (no present tool result with numbers), or every
+ * cited number is grounded.
+ *
+ * `toolPayloads` is the `data` payload of each PRESENT tool result this turn.
+ */
+export function findUnverifiedCoachNumbers(
+  prose: string,
+  toolPayloads: ReadonlyArray<unknown>,
+): UnverifiedCoachNumber[] {
+  if (!prose) return [];
+  const authoritative = new Set<number>();
+  for (const payload of toolPayloads)
+    collectNumericLeaves(payload, authoritative);
+  // No authoritative figures (a qualitative turn / no-tools path) — nothing to
+  // grade against. The prompt-level grounding rule remains the backstop.
+  if (authoritative.size === 0) return [];
+
+  const findings: UnverifiedCoachNumber[] = [];
+  for (const { value, raw } of extractNumbers(prose)) {
+    if (isStructural(value, raw)) continue;
+    if (isGrounded(value, authoritative)) continue;
+    findings.push({ value, source: raw.slice(0, 32) });
+  }
+  return findings;
+}
+
+/**
+ * Soft-correct the prose: replace each unverified numeric token with a neutral
+ * placeholder so a drifted figure never reaches the user as if authoritative,
+ * while the surrounding qualitative framing is preserved. Conservative — it
+ * only rewrites the exact ungrounded tokens the verifier flagged, and only the
+ * first occurrence of each, leaving every grounded number untouched.
+ *
+ * Returns the (possibly unchanged) prose plus the count of tokens stripped.
+ */
+export function stripUnverifiedNumbers(
+  prose: string,
+  findings: ReadonlyArray<UnverifiedCoachNumber>,
+): { prose: string; stripped: number } {
+  if (findings.length === 0) return { prose, stripped: 0 };
+  let out = prose;
+  let stripped = 0;
+  for (const f of findings) {
+    // Replace the first standalone occurrence of the flagged token. The token
+    // is bounded by non-digit / non-sign edges so we don't clip a larger number.
+    const token = f.source;
+    const idx = out.indexOf(token);
+    if (idx === -1) continue;
+    out = `${out.slice(0, idx)}[unverified]${out.slice(idx + token.length)}`;
+    stripped += 1;
+  }
+  return { prose: out, stripped };
+}
diff --git a/src/lib/ai/coach/derived-snapshot.ts b/src/lib/ai/coach/derived-snapshot.ts
index 51a96bacc..34422b03b 100644
--- a/src/lib/ai/coach/derived-snapshot.ts
+++ b/src/lib/ai/coach/derived-snapshot.ts
@@ -16,6 +16,7 @@
  */
 import {
   computeDerivedMetric,
+  computeCoincidentDeviation,
   isDerivedOk,
   type DerivedMetricId,
   type BaselineProfile,
@@ -55,6 +56,35 @@ interface DerivedSnapshotEntry {
   historyDays: number;
 }
 
+/**
+ * v1.21.0 (C3 / D3) — the coincident-deviation flag, compactly. "Two or more
+ * of your vitals are outside their usual band today." Descriptive multi-signal
+ * co-movement, never a cause; carries the illness-explained reframe. Folded
+ * into the derived block so BOTH Coach paths (the tool path via
+ * get_illness_recovery/get_correlations AND the no-tools snapshot floor) can
+ * narrate it. Omitted entirely when it did not fire (no noise).
+ */
+interface CoincidentSnapshotEntry {
+  fired: true;
+  /** The out-of-band vitals (possible factors), e.g. "resting heart rate above". */
+  contributing: string[];
+  /** The day the flag was evaluated (YYYY-MM-DD). */
+  day: string;
+  /** True when an active illness episode explains the deviations. */
+  illnessExplained: boolean;
+}
+
+/**
+ * The derived block: per-metric compact score entries (keyed by metric id),
+ * plus the optional fired-only coincident-deviation flag under its own reserved
+ * `COINCIDENT_DEVIATION` key. The score entries keep their `DerivedSnapshotEntry`
+ * shape (so callers + tests read `block.READINESS.value` directly); the
+ * coincident flag rides alongside without widening the score index signature.
+ */
+type DerivedSnapshotBlock = Record<string, DerivedSnapshotEntry> & {
+  COINCIDENT_DEVIATION?: CoincidentSnapshotEntry;
+};
+
 /** Pull the headline number + band off each metric's value shape. */
 function summariseValue(
   metric: DerivedMetricId,
@@ -115,9 +145,18 @@ export async function buildDerivedSnapshotBlock(
   userId: string,
   profile: BaselineProfile,
   now: Date,
-): Promise<Record<string, DerivedSnapshotEntry> | null> {
+): Promise<DerivedSnapshotBlock | null> {
   const block: Record<string, DerivedSnapshotEntry> = {};
 
+  // v1.21.0 (C3 / D3) — the coincident-deviation flag, fired-only. Computed
+  // off the one shared profile alongside the scores; fail-soft to null so a
+  // baseline hiccup never sinks the derived block. Only attached when it
+  // FIRED (≥2 vitals out of band today) — a quiet day adds no entry, keeping
+  // the snapshot noise-free.
+  const coincidentPromise = computeCoincidentDeviation(userId, profile, {
+    now,
+  }).catch(() => null);
+
   // The metrics are independent passthrough reads off the one shared profile —
   // no ordering dependency — so compute them concurrently. Per-metric fault
   // isolation: a transient failure on one must never sink the whole Coach turn,
@@ -176,5 +215,22 @@ export async function buildDerivedSnapshotBlock(
     }
   }
 
-  return Object.keys(block).length > 0 ? block : null;
+  // Attach the coincident-deviation flag (fired-only) — the await happens here
+  // so the score computes above run concurrently with it. It rides under its
+  // own reserved key alongside the score entries.
+  const out: DerivedSnapshotBlock = block;
+  const coincident = await coincidentPromise;
+  if (coincident && isDerivedOk(coincident) && coincident.value.fired) {
+    out.COINCIDENT_DEVIATION = {
+      fired: true,
+      contributing: coincident.value.contributing.map(
+        (c) =>
+          `${String(c.type).replace(/_/g, " ").toLowerCase()} ${c.direction}`,
+      ),
+      day: coincident.value.day,
+      illnessExplained: coincident.value.illnessExplained,
+    };
+  }
+
+  return Object.keys(out).length > 0 ? out : null;
 }
diff --git a/src/lib/ai/coach/tools/correlations-read.ts b/src/lib/ai/coach/tools/correlations-read.ts
new file mode 100644
index 000000000..1d1424ab3
--- /dev/null
+++ b/src/lib/ai/coach/tools/correlations-read.ts
@@ -0,0 +1,233 @@
+/**
+ * v1.21.0 (C3) — Coach correlations reader.
+ *
+ * Surfaces the deterministic insight engine's cross-metric intelligence to the
+ * Coach via the `get_correlations` tool. Two read-only sources, both already
+ * computed elsewhere and reused verbatim here (no new statistics):
+ *
+ *  - The FDR-controlled, day-D→D+1 lagged all-pairs discovery
+ *    (`@/lib/insights/correlation-discovery`). We run the SAME full-matrix scan
+ *    the `/api/insights/correlations` route + the per-metric card run, so the
+ *    Coach never surfaces a pair the insight pages would not — same Pearson,
+ *    same exact p-value, same Benjamini-Hochberg control. We return every
+ *    surviving pair (not filtered to one metric) as a descriptive driver row.
+ *  - The coincident-deviation flag (`computeCoincidentDeviation`): "two or more
+ *    of your vitals are outside their usual band today", with the illness-
+ *    explained reframe carried through.
+ *
+ * Grounding posture mirrors the other tools: a structured `{ present: false }`
+ * when too little paired data exists for any pattern to survive (or the read
+ * fails), never a throw and never an ambiguous empty list. The driver rows are
+ * descriptive — direction + lag + n + the engine's own never-causal
+ * interpretation string — so the Coach states the observed linkage without
+ * inventing a relationship.
+ */
+import type { MeasurementType } from "@/generated/prisma/client";
+import { prisma } from "@/lib/db";
+import { wallClockInTz } from "@/lib/tz/wall-clock";
+import {
+  discoverCorrelations,
+  DISCOVERY_BEHAVIOURS,
+  DISCOVERY_OUTCOMES,
+  type DailySeriesPoint,
+  type NamedSeries,
+} from "@/lib/insights/correlation-discovery";
+import {
+  computeCoincidentDeviation,
+  loadBaselineProfile,
+  isDerivedOk,
+} from "@/lib/insights/derived";
+
+const MS_PER_DAY = 24 * 60 * 60 * 1000;
+/** Trailing window for the discovery scan — mirrors the insight route. */
+const WINDOW_DAYS = 180;
+
+/** One discovered driver pair, descriptive — never causal. */
+export interface CoachCorrelationDriver {
+  behaviour: string;
+  outcome: string;
+  /** "higher" / "lower" — sign of the next-day association. */
+  direction: "higher" | "lower";
+  /** Lag in days (always 1 today). */
+  lagDays: number;
+  /** Paired-day sample count after the lag join. */
+  n: number;
+  /** Pearson r, rounded for display. */
+  r: number;
+  /** The engine's conservative, descriptive interpretation. */
+  note: string;
+}
+
+/** The coincident-deviation summary the Coach can narrate. */
+export interface CoachCoincidentFlag {
+  /** True when ≥2 vitals are outside their usual band on the latest day. */
+  fired: boolean;
+  /** The vitals outside their band (possible factors, never a cause). */
+  contributing: Array<{ metric: string; direction: "above" | "below" }>;
+  /** The day the flag was evaluated (YYYY-MM-DD). */
+  day: string;
+  /** True when an active illness episode explains the deviations. */
+  illnessExplained: boolean;
+}
+
+export interface CoachCorrelationsResult {
+  present: boolean;
+  drivers?: CoachCorrelationDriver[];
+  coincident?: CoachCoincidentFlag;
+  /** How many behaviour×outcome pairs were tested (honest footer). */
+  pairsTested?: number;
+  /** Trailing-day window the discovery scanned. */
+  windowDays?: number;
+  reason?: string;
+}
+
+/** Day key (YYYY-MM-DD) for an instant in the user's display timezone. */
+function tzDayKey(at: Date, tz: string): string {
+  const { year, month, day } = wallClockInTz(at, tz);
+  return `${year}-${String(month).padStart(2, "0")}-${String(day).padStart(2, "0")}`;
+}
+
+/** Collapse rows to per-day means keyed in the user's tz. */
+function toDailyMeans(
+  rows: Array<{ value: number; at: Date }>,
+  tz: string,
+): DailySeriesPoint[] {
+  const byDay = new Map<string, { sum: number; count: number }>();
+  for (const r of rows) {
+    if (!Number.isFinite(r.value)) continue;
+    const day = tzDayKey(r.at, tz);
+    const acc = byDay.get(day) ?? { sum: 0, count: 0 };
+    acc.sum += r.value;
+    acc.count += 1;
+    byDay.set(day, acc);
+  }
+  return [...byDay.entries()]
+    .map(([day, acc]) => ({ day, value: acc.sum / acc.count }))
+    .sort((a, b) => (a.day < b.day ? -1 : 1));
+}
+
+/** Lower-case, space-separated label from a discovery channel key. */
+function humanise(key: string): string {
+  return key.replace(/_/g, " ").toLowerCase();
+}
+
+/**
+ * Build the Coach correlations payload for a user. Returns `{ present: false }`
+ * when no driver survives AND the coincident flag is not informative, when the
+ * user has no correlatable data, or on any read/compute failure (best-effort —
+ * a correlation hiccup must never break the chat turn).
+ */
+export async function readCoachCorrelations(
+  userId: string,
+): Promise<CoachCorrelationsResult> {
+  try {
+    const profile = await loadBaselineProfile(prisma, userId);
+    const userRow = await prisma.user.findUnique({
+      where: { id: userId },
+      select: { timezone: true },
+    });
+    const tz = userRow?.timezone ?? "Europe/Berlin";
+    const since = new Date(Date.now() - WINDOW_DAYS * MS_PER_DAY);
+
+    // MOOD is mood-entry backed, not a measurement type — strip it from the
+    // measurement query and source it separately, exactly like the route.
+    const behaviourTypes = DISCOVERY_BEHAVIOURS.filter(
+      (k) => k !== "MOOD",
+    ) as MeasurementType[];
+    const outcomeTypes = DISCOVERY_OUTCOMES.filter(
+      (k) => k !== "MOOD",
+    ) as MeasurementType[];
+
+    const [measurements, moodEntries, coincidentDerived] = await Promise.all([
+      prisma.measurement.findMany({
+        where: {
+          userId,
+          deletedAt: null,
+          measuredAt: { gte: since },
+          type: { in: [...behaviourTypes, ...outcomeTypes] },
+        },
+        orderBy: { measuredAt: "asc" },
+        take: 20000,
+        select: { type: true, value: true, measuredAt: true },
+      }),
+      prisma.moodEntry.findMany({
+        where: { userId, deletedAt: null, moodLoggedAt: { gte: since } },
+        orderBy: { moodLoggedAt: "asc" },
+        take: 5000,
+        select: { score: true, moodLoggedAt: true },
+      }),
+      // Coincident-deviation is its own derived metric — fail-soft to null so a
+      // baseline hiccup never sinks the whole correlations read.
+      computeCoincidentDeviation(userId, profile).catch(() => null),
+    ]);
+
+    const byType = new Map<string, Array<{ value: number; at: Date }>>();
+    for (const m of measurements) {
+      const list = byType.get(m.type) ?? [];
+      list.push({ value: m.value, at: m.measuredAt });
+      byType.set(m.type, list);
+    }
+    const moodDaily = toDailyMeans(
+      moodEntries.map((e) => ({ value: e.score, at: e.moodLoggedAt })),
+      tz,
+    );
+
+    const series: NamedSeries[] = [];
+    for (const key of DISCOVERY_BEHAVIOURS) {
+      const points =
+        key === "MOOD" ? moodDaily : toDailyMeans(byType.get(key) ?? [], tz);
+      series.push({ key, role: "behaviour", points });
+    }
+    for (const key of DISCOVERY_OUTCOMES) {
+      const points =
+        key === "MOOD" ? moodDaily : toDailyMeans(byType.get(key) ?? [], tz);
+      series.push({ key, role: "outcome", points });
+    }
+
+    const discovery = discoverCorrelations(series);
+    const drivers: CoachCorrelationDriver[] = discovery.discovered.map((d) => ({
+      behaviour: humanise(d.behaviour),
+      outcome: humanise(d.outcome),
+      direction: d.r >= 0 ? "higher" : "lower",
+      lagDays: d.lagDays,
+      n: d.n,
+      r: Math.round(d.r * 100) / 100,
+      note: d.interpretation,
+    }));
+
+    const coincident = buildCoincidentFlag(coincidentDerived);
+
+    // Nothing to say: no surviving driver AND the coincident flag is either
+    // insufficient or quiet (not fired). Report a clean miss.
+    if (drivers.length === 0 && (!coincident || !coincident.fired)) {
+      return { present: false, reason: "no_significant_pattern" };
+    }
+
+    return {
+      present: true,
+      ...(drivers.length > 0 ? { drivers } : {}),
+      ...(coincident ? { coincident } : {}),
+      pairsTested: discovery.pairsTested,
+      windowDays: WINDOW_DAYS,
+    };
+  } catch {
+    return { present: false, reason: "retrieval_failed" };
+  }
+}
+
+/** Shape the derived coincident-deviation value into the Coach summary. */
+function buildCoincidentFlag(
+  derived: Awaited<ReturnType<typeof computeCoincidentDeviation>> | null,
+): CoachCoincidentFlag | undefined {
+  if (!derived || !isDerivedOk(derived)) return undefined;
+  const v = derived.value;
+  return {
+    fired: v.fired,
+    contributing: v.contributing.map((c) => ({
+      metric: humanise(String(c.type)),
+      direction: c.direction === "above" ? "above" : "below",
+    })),
+    day: v.day,
+    illnessExplained: v.illnessExplained,
+  };
+}
diff --git a/src/lib/ai/coach/tools/definitions.ts b/src/lib/ai/coach/tools/definitions.ts
index 4fa65c033..d41caf2f6 100644
--- a/src/lib/ai/coach/tools/definitions.ts
+++ b/src/lib/ai/coach/tools/definitions.ts
@@ -9,15 +9,17 @@
  * narrowed from the session in the executor), and every tool is read-only, so
  * there is no new mutation or egress surface.
  *
- * Six tools ship in v1.20.0 (the research's recommended slice):
+ * Tools ship as a closed catalogue:
  *   1. get_metric_series         — BP / weight / pulse + the ~38 additive series
  *   2. get_glucose_panel         — per-context daily means + the 30-day clinical panel
  *   3. get_sleep                 — per-night sleep + sleep-rhythm (debt + chronotype)
  *   4. get_medication_compliance — dose-weighted compliance + GLP-1
  *   5. get_labs                  — latest reading per biomarker (12 months)
  *   6. get_illness_recovery      — restMode + active/resolved illnesses + recovery composites
- *
- * cycle / correlation / workouts are deferred to a later release.
+ *   7. get_workouts              — recent sessions + per-sport rollup (v1.21.0, C2-4)
+ *   8. get_cycle                 — menstrual phase / prediction / correlation (v1.21.0, C2-1)
+ *   9. get_correlations          — discovered FDR cross-metric drivers + the
+ *                                  coincident-deviation flag (v1.21.0, C3)
  */
 import { z } from "zod/v4";
 
@@ -35,6 +37,9 @@ export const COACH_TOOL_NAMES = [
   "get_medication_compliance",
   "get_labs",
   "get_illness_recovery",
+  "get_workouts",
+  "get_cycle",
+  "get_correlations",
 ] as const;
 
 export type CoachToolName = (typeof COACH_TOOL_NAMES)[number];
@@ -83,6 +88,16 @@ export const getLabsArgsSchema = z
 
 export const getIllnessRecoveryArgsSchema = z.object({}).strict();
 
+export const getWorkoutsArgsSchema = z
+  .object({
+    window: coachScopeWindowSchema.optional(),
+  })
+  .strict();
+
+export const getCycleArgsSchema = z.object({}).strict();
+
+export const getCorrelationsArgsSchema = z.object({}).strict();
+
 /**
  * JSON-Schema parameter shapes handed to the provider. Kept hand-written
  * (rather than generated from Zod) so the wire description the model reads is
@@ -205,4 +220,43 @@ export const COACH_TOOL_DEFS: AiToolDef[] = [
       properties: {},
     },
   },
+  {
+    name: "get_workouts",
+    description:
+      "Fetch the user's workouts: the most recent sessions (sport, duration, energy, distance, avg/max HR) plus a per-sport rollup over the window. Use for training-load and 'how were my runs / am I overtraining?' questions. Returns { present: false } when no workouts are tracked.",
+    parameters: {
+      type: "object",
+      additionalProperties: false,
+      required: [],
+      properties: {
+        window: {
+          type: "string",
+          enum: WINDOW_ENUM,
+          description: "Analysis window. Defaults to the user's scope window.",
+        },
+      },
+    },
+  },
+  {
+    name: "get_cycle",
+    description:
+      "Fetch the user's menstrual-cycle context: current phase + day-of-cycle, the next predicted event, and the headline phase-correlation finding. Descriptive only — never a contraception-grade or 'safe day' claim. Returns { present: false } when cycle tracking is off or there is no data.",
+    parameters: {
+      type: "object",
+      additionalProperties: false,
+      required: [],
+      properties: {},
+    },
+  },
+  {
+    name: "get_correlations",
+    description:
+      "Fetch the user's DISCOVERED cross-metric patterns: statistically-vetted (FDR-controlled) day-to-next-day driver pairs between behaviours (daylight, mood, glucose, blood pressure, steps) and outcomes (sleep, HRV, resting HR, weight, mood), each with direction, lag, sample size and a descriptive — never causal — note. Also reports the coincident-deviation flag (whether two or more vitals are outside their usual band today). Use when a metric is off and you want to state the observed linkage. Returns { present: false } when too little paired data exists for any pattern to survive.",
+    parameters: {
+      type: "object",
+      additionalProperties: false,
+      required: [],
+      properties: {},
+    },
+  },
 ];
diff --git a/src/lib/ai/coach/tools/executor.ts b/src/lib/ai/coach/tools/executor.ts
index f9502c7d9..60baa2ba1 100644
--- a/src/lib/ai/coach/tools/executor.ts
+++ b/src/lib/ai/coach/tools/executor.ts
@@ -37,6 +37,9 @@ import {
   getMedicationComplianceArgsSchema,
   getLabsArgsSchema,
   getIllnessRecoveryArgsSchema,
+  getWorkoutsArgsSchema,
+  getCycleArgsSchema,
+  getCorrelationsArgsSchema,
   isCoachToolName,
   type CoachToolName,
 } from "./definitions";
@@ -44,6 +47,7 @@ import {
   COACH_SOURCE_SNAPSHOT_KEY,
   METRIC_SERIES_EXCLUDED_SOURCES,
 } from "./source-keys";
+import { readCoachCorrelations } from "./correlations-read";
 
 /** A read-only structured tool result. Serialised to a `role:"tool"` turn. */
 export interface CoachToolResult {
@@ -162,9 +166,15 @@ async function dispatch(
     case "get_medication_compliance":
       return getMedicationCompliance(userId, rawArgs, fallbackWindow);
     case "get_labs":
-      return getLabs(userId, rawArgs);
+      return getLabs(userId, rawArgs, fallbackWindow);
     case "get_illness_recovery":
-      return getIllnessRecovery(userId);
+      return getIllnessRecovery(userId, fallbackWindow);
+    case "get_workouts":
+      return getWorkouts(userId, rawArgs, fallbackWindow);
+    case "get_cycle":
+      return getCycle(userId, rawArgs);
+    case "get_correlations":
+      return getCorrelations(userId, rawArgs);
   }
 }
 
@@ -300,13 +310,23 @@ async function getMedicationCompliance(
 async function getLabs(
   userId: string,
   rawArgs: unknown,
+  fallbackWindow: CoachScopeWindow | undefined,
 ): Promise<CoachToolResult> {
   const parsed = getLabsArgsSchema.safeParse(rawArgs);
   if (!parsed.success) return badArgs("get_labs", parsed.error);
   // Labs ride the snapshot regardless of `sources` (attached unconditionally),
   // so a minimal scope still surfaces them. Pass an empty source set to keep
   // the read tight.
-  const snapshot = await buildCoachSnapshot(userId, { sources: [] });
+  //
+  // v1.21.0 (A5-F4) — the labs block itself is a "latest reading per biomarker
+  // over the last 12 months" snapshot and is intentionally window-AGNOSTIC
+  // (the read cutoff is fixed). We still thread the conversation's window onto
+  // the scope so the snapshot's `scope` block reports the right horizon for the
+  // turn; it does not move the labs read.
+  const snapshot = await buildCoachSnapshot(userId, {
+    sources: [],
+    window: fallbackWindow,
+  });
   const labs = pickSection(snapshot.sections, "labs") as
     | { recent?: Array<{ name?: string; analyte?: string }> }
     | undefined;
@@ -327,15 +347,23 @@ async function getLabs(
   return { present: true, data: labs };
 }
 
-async function getIllnessRecovery(userId: string): Promise<CoachToolResult> {
+async function getIllnessRecovery(
+  userId: string,
+  fallbackWindow: CoachScopeWindow | undefined,
+): Promise<CoachToolResult> {
   // Validate the (empty) args shape for consistency; an empty object always
   // passes.
   getIllnessRecoveryArgsSchema.parse({});
   // Recovery composites gate on the `recovery` module + the HRV/RHR/VO2max
   // sources; request them so the derived / dayStrain / trajectory blocks can
   // build when the module is on. Illness rides the snapshot unconditionally.
+  //
+  // v1.21.0 (A5-F4) — honour the conversation's window so the recovery/strain/
+  // trajectory composites are computed over the horizon the caller asked for
+  // rather than the builder default.
   const snapshot = await buildCoachSnapshot(userId, {
     sources: ["hrv", "resting_hr", "vo2_max"],
+    window: fallbackWindow,
   });
   const illness = pickSection(snapshot.sections, "illness");
   const derived = pickSection(snapshot.sections, "derived");
@@ -359,3 +387,60 @@ async function getIllnessRecovery(userId: string): Promise<CoachToolResult> {
     },
   };
 }
+
+async function getWorkouts(
+  userId: string,
+  rawArgs: unknown,
+  fallbackWindow: CoachScopeWindow | undefined,
+): Promise<CoachToolResult> {
+  const parsed = getWorkoutsArgsSchema.safeParse(rawArgs);
+  if (!parsed.success) return badArgs("get_workouts", parsed.error);
+  // The workouts block builds when the `workouts` cluster is active AND the
+  // user has workout rows in the window. Scope the read to that single source.
+  const snapshot = await buildCoachSnapshot(
+    userId,
+    scopeFor(["workouts"], parsed.data.window, fallbackWindow),
+  );
+  const workouts = pickSection(snapshot.sections, "workouts");
+  if (workouts === undefined) return { present: false, reason: "no_data" };
+  return { present: true, data: workouts };
+}
+
+async function getCycle(
+  userId: string,
+  rawArgs: unknown,
+): Promise<CoachToolResult> {
+  const parsed = getCycleArgsSchema.safeParse(rawArgs);
+  if (!parsed.success) return badArgs("get_cycle", parsed.error);
+  // The cycle block is gated INSIDE the builder by `isCycleAvailableForUser`
+  // (the per-user toggle AND the operator switch), independent of `sources` —
+  // so a minimal scope still surfaces it when the account tracks cycles, and a
+  // non-cycle account structurally produces no block (→ present:false).
+  const snapshot = await buildCoachSnapshot(userId, { sources: [] });
+  const cycle = pickSection(snapshot.sections, "cycle");
+  if (cycle === undefined) return { present: false, reason: "no_data" };
+  return { present: true, data: cycle };
+}
+
+async function getCorrelations(
+  userId: string,
+  rawArgs: unknown,
+): Promise<CoachToolResult> {
+  const parsed = getCorrelationsArgsSchema.safeParse(rawArgs);
+  if (!parsed.success) return badArgs("get_correlations", parsed.error);
+  // Reads the deterministic FDR discovery + coincident-deviation flag; returns
+  // a clean `{ present: false }` when too little paired data exists.
+  const result = await readCoachCorrelations(userId);
+  if (!result.present) {
+    return { present: false, reason: result.reason ?? "no_data" };
+  }
+  return {
+    present: true,
+    data: {
+      ...(result.drivers ? { drivers: result.drivers } : {}),
+      ...(result.coincident ? { coincident: result.coincident } : {}),
+      pairsTested: result.pairsTested,
+      windowDays: result.windowDays,
+    },
+  };
+}
diff --git a/src/lib/ai/coach/tools/inventory.ts b/src/lib/ai/coach/tools/inventory.ts
index 7e4e93bb8..10a5431e4 100644
--- a/src/lib/ai/coach/tools/inventory.ts
+++ b/src/lib/ai/coach/tools/inventory.ts
@@ -17,7 +17,17 @@
  */
 import { isCycleAvailableForUser } from "@/lib/cycle/gate";
 import { buildCoachSnapshot } from "@/lib/ai/coach/snapshot";
-import type { CoachProvenanceMetric, CoachScope } from "@/lib/ai/coach/types";
+import type {
+  CoachProvenanceMetric,
+  CoachScope,
+  CoachScopeSource,
+} from "@/lib/ai/coach/types";
+import {
+  COACH_SOURCE_SNAPSHOT_KEY,
+  COACH_SOURCE_DOMAIN_LABEL,
+  METRIC_SERIES_INVENTORY_SOURCES,
+  FULL_INVENTORY_SOURCE_SET,
+} from "./source-keys";
 
 /** One row of the inventory: a domain + whether the user has data for it. */
 export interface InventoryEntry {
@@ -36,73 +46,48 @@ export interface CoachDataInventory {
   entries: InventoryEntry[];
   /** Illness rest-mode flag, so the safety framing is right before any call. */
   restMode: boolean;
-  /** Whether cycle tracking is available (the get_cycle tool is deferred). */
+  /** Whether cycle tracking is available (fetched via get_cycle). */
   cycleEnabled: boolean;
   /** The window the inventory was built against. */
   window: string;
 }
 
 /**
- * Map a snapshot section key → an inventory row. The per-metric series tool
- * carries the `metric` argument; the dedicated-tool domains name their tool.
+ * v1.21.0 (C2-2 / C2-3) — generate the get_metric_series inventory rows from
+ * the FULL source→key map rather than the eight legacy clusters. Every series
+ * the user actually has rows for is advertised, so the model is no longer told
+ * (rule 2) to skip body-composition / vascular / SpO2 / gait / environment.
+ * The `provenance` count key equals the source name for these series sources.
  */
 const METRIC_SERIES_DOMAINS: Array<{
   sectionKey: string;
-  metric: string;
+  metric: CoachScopeSource;
   domain: string;
   provenance: CoachProvenanceMetric;
-}> = [
-  {
-    sectionKey: "bloodPressure",
-    metric: "bp",
-    domain: "blood pressure",
-    provenance: "bp",
-  },
-  {
-    sectionKey: "weight",
-    metric: "weight",
-    domain: "weight",
-    provenance: "weight",
-  },
-  {
-    sectionKey: "pulse",
-    metric: "pulse",
-    domain: "pulse",
-    provenance: "pulse",
-  },
-  { sectionKey: "mood", metric: "mood", domain: "mood", provenance: "mood" },
-  {
-    sectionKey: "heartRateVariability",
-    metric: "hrv",
-    domain: "heart-rate variability",
-    provenance: "hrv",
-  },
-  {
-    sectionKey: "restingHeartRate",
-    metric: "resting_hr",
-    domain: "resting heart rate",
-    provenance: "resting_hr",
-  },
-  {
-    sectionKey: "steps",
-    metric: "steps",
-    domain: "steps",
-    provenance: "steps",
-  },
-  {
-    sectionKey: "vo2Max",
-    metric: "vo2_max",
-    domain: "VO2 max",
-    provenance: "vo2_max",
-  },
-];
+}> = METRIC_SERIES_INVENTORY_SOURCES.map((metric) => ({
+  sectionKey: COACH_SOURCE_SNAPSHOT_KEY[metric] as string,
+  metric,
+  domain: COACH_SOURCE_DOMAIN_LABEL[metric] ?? (metric as string),
+  provenance: metric as unknown as CoachProvenanceMetric,
+}));
 
 export async function buildCoachDataInventory(
   userId: string,
   scope: CoachScope | undefined,
 ): Promise<CoachDataInventory> {
+  // v1.21.0 (C2-2) — probe presence against the FULL source set, not the
+  // user's narration-cluster default. `effectiveScope` only carried the
+  // window; expanding `sources` here makes the snapshot build every domain the
+  // user has rows for, so sleep / glucose / activity / body-composition / etc.
+  // no longer report `absent` for a default-prefs user. Each per-tool read
+  // still re-scopes to its own domain, so this presence probe never widens a
+  // figure read — it only widens what the inventory advertises.
+  const probeScope: CoachScope = {
+    sources: [...FULL_INVENTORY_SOURCE_SET],
+    window: scope?.window,
+  };
   const [snapshot, cycleEnabled] = await Promise.all([
-    buildCoachSnapshot(userId, scope),
+    buildCoachSnapshot(userId, probeScope),
     isCycleAvailableForUser(userId),
   ]);
   const sections = snapshot.sections;
@@ -147,6 +132,14 @@ export async function buildCoachDataInventory(
       ? { count: counts.compliance }
       : {}),
   });
+  // v1.21.0 (C2-4) — workouts has its own tool now (get_metric_series refuses
+  // it). The block builds when the user has workout rows + the cluster is on.
+  entries.push({
+    tool: "get_workouts",
+    domain: "workouts & training",
+    present: has("workouts"),
+    ...(typeof counts.workouts === "number" ? { count: counts.workouts } : {}),
+  });
   entries.push({
     tool: "get_labs",
     domain: "lab results",
@@ -158,6 +151,31 @@ export async function buildCoachDataInventory(
     present:
       has("illness") || has("derived") || has("dayStrain") || has("trajectory"),
   });
+  // v1.21.0 (C3) — discovered cross-metric correlations (FDR-controlled lagged
+  // drivers) + the coincident-deviation flag. Advertised when the user has any
+  // two discovery channels with data; the tool itself returns present:false
+  // cleanly when nothing survives, so the inventory marks it present whenever a
+  // correlatable signal exists (mood / cardio / activity).
+  entries.push({
+    tool: "get_correlations",
+    domain: "cross-metric patterns (discovered drivers)",
+    present:
+      has("derived") ||
+      has("mood") ||
+      has("heartRateVariability") ||
+      has("restingHeartRate") ||
+      has("steps") ||
+      has("sleep"),
+  });
+  // v1.21.0 (C2-1) — cycle is fetchable via get_cycle when cycle tracking is
+  // available for this account (per-user toggle AND operator switch).
+  if (cycleEnabled) {
+    entries.push({
+      tool: "get_cycle",
+      domain: "menstrual cycle & phase",
+      present: has("cycle"),
+    });
+  }
 
   // restMode rides the illness section.
   const illness = sections.illness as { restMode?: boolean } | undefined;
diff --git a/src/lib/ai/coach/tools/loop.ts b/src/lib/ai/coach/tools/loop.ts
index 1f0dfb1d6..5e8208e4a 100644
--- a/src/lib/ai/coach/tools/loop.ts
+++ b/src/lib/ai/coach/tools/loop.ts
@@ -28,7 +28,11 @@ import type { ProviderChainResolved } from "@/lib/ai/provider-runner";
 import type { AiMessage, AiToolDef, CompletionResult } from "@/lib/ai/types";
 import type { ProviderHealthLedger } from "@/lib/ai/provider-health-ledger";
 import type { CoachScopeWindow } from "@/lib/ai/coach/types";
-import { executeCoachTool, type CoachToolTrace } from "./executor";
+import {
+  executeCoachTool,
+  type CoachToolResult,
+  type CoachToolTrace,
+} from "./executor";
 
 export const MAX_ROUNDS = 2;
 /** Absolute ceiling; the final allowed round forces prose (toolChoice none). */
@@ -45,6 +49,13 @@ export interface CoachToolLoopResult {
   rounds: number;
   /** Which tools ran + whether each found data (persisted onto provenance). */
   toolTrace: CoachToolTrace[];
+  /**
+   * v1.21.0 (P6) — the structured payloads of every PRESENT tool result this
+   * turn, in call order. The post-hoc prose number-verifier extracts the
+   * numeric leaves from these to cross-check the figures the model cited. Empty
+   * on a no-tools answer.
+   */
+  toolResults: CoachToolResult[];
 }
 
 export async function runCoachToolLoop(args: {
@@ -78,6 +89,7 @@ export async function runCoachToolLoop(args: {
   let rounds = 0;
   let workingProviderType = "";
   const toolTrace: CoachToolTrace[] = [];
+  const toolResults: CoachToolResult[] = [];
 
   // Round budget: rounds 1..HARD_CAP. On the last allowed round we forbid tool
   // calls so the model must answer.
@@ -120,7 +132,14 @@ export async function runCoachToolLoop(args: {
           forcedFinal: isForcedFinal,
         },
       });
-      return { result, workingProviderType, totalTokens, rounds, toolTrace };
+      return {
+        result,
+        workingProviderType,
+        totalTokens,
+        rounds,
+        toolTrace,
+        toolResults,
+      };
     }
 
     // Append the assistant turn that requested the tools, then execute them in
@@ -140,6 +159,10 @@ export async function runCoachToolLoop(args: {
           fallbackWindow,
         });
         toolTrace.push({ name: call.name, present: toolResult.present });
+        // v1.21.0 (P6) — retain the present results' payloads for the post-hoc
+        // prose number-verifier (the union of numeric leaves grounds the
+        // figures the model may cite).
+        if (toolResult.present) toolResults.push(toolResult);
         return { call, toolResult };
       }),
     );
diff --git a/src/lib/ai/coach/tools/source-keys.ts b/src/lib/ai/coach/tools/source-keys.ts
index d0d821347..a5fc0d878 100644
--- a/src/lib/ai/coach/tools/source-keys.ts
+++ b/src/lib/ai/coach/tools/source-keys.ts
@@ -17,7 +17,10 @@
  * either resolves here or is explicitly one of the dedicated-tool sources, so a
  * future source addition cannot silently fall through to a fabricated answer.
  */
-import type { CoachScopeSource } from "@/lib/ai/coach/types";
+import {
+  coachScopeSourceSchema,
+  type CoachScopeSource,
+} from "@/lib/ai/coach/types";
 
 /** Sources that `get_metric_series` does NOT serve (they have own tools). */
 export const METRIC_SERIES_EXCLUDED_SOURCES: ReadonlySet<CoachScopeSource> =
@@ -73,3 +76,78 @@ export const COACH_SOURCE_SNAPSHOT_KEY: Readonly<
   sleep: "sleep",
   body_temp: "bodyTemperature",
 };
+
+/**
+ * v1.21.0 (C2-3) — human-readable domain label per metric source, for the DATA
+ * INVENTORY lines. Brand-free, lower-case, stable across turns so the cached
+ * prefix holds. Every key in `COACH_SOURCE_SNAPSHOT_KEY` plus the dedicated-tool
+ * sources has an entry; the inventory renders one line per series source the
+ * user actually has rows for.
+ */
+export const COACH_SOURCE_DOMAIN_LABEL: Readonly<
+  Partial<Record<CoachScopeSource, string>>
+> = {
+  bp: "blood pressure",
+  weight: "weight",
+  pulse: "pulse",
+  mood: "mood",
+  hrv: "heart-rate variability",
+  resting_hr: "resting heart rate",
+  walking_hr: "walking heart rate",
+  respiratory_rate: "respiratory rate",
+  spo2: "blood oxygen (SpO2)",
+  pulse_wave_velocity: "pulse-wave velocity",
+  vascular_age: "vascular age",
+  body_fat: "body fat",
+  fat_mass: "fat mass",
+  fat_free_mass: "fat-free mass",
+  muscle_mass: "muscle mass",
+  lean_body_mass: "lean body mass",
+  bone_mass: "bone mass",
+  total_body_water: "total body water",
+  bmi: "BMI",
+  visceral_fat: "visceral fat",
+  steps: "steps",
+  active_energy: "active energy",
+  flights: "flights climbed",
+  distance: "walking/running distance",
+  vo2_max: "VO2 max",
+  walking_steadiness: "walking steadiness",
+  walking_asymmetry: "walking asymmetry",
+  walking_double_support: "walking double support",
+  walking_step_length: "walking step length",
+  walking_speed: "walking speed",
+  audio_env: "environmental audio exposure",
+  audio_headphone: "headphone audio exposure",
+  audio_event: "audio exposure events",
+  daylight: "time in daylight",
+  skin_temp: "skin temperature",
+  sleep: "sleep",
+  body_temp: "body temperature",
+};
+
+/**
+ * v1.21.0 (C2-2 / C2-3) — the FULL set of metric-series sources the inventory
+ * probes for presence: every source `get_metric_series` can serve (the
+ * `COACH_SOURCE_SNAPSHOT_KEY` keys), minus the few that ride a dedicated tool
+ * (sleep has `get_sleep`; glucose/compliance/workouts are excluded). The
+ * inventory is built against this full set so a domain with data is advertised
+ * regardless of the user's narration-cluster preference — closing the
+ * default-cluster reach gap. `sleep` is omitted here because `get_sleep` owns
+ * its inventory line.
+ */
+export const METRIC_SERIES_INVENTORY_SOURCES: ReadonlyArray<CoachScopeSource> =
+  (Object.keys(COACH_SOURCE_SNAPSHOT_KEY) as CoachScopeSource[]).filter(
+    (source) => source !== "sleep",
+  );
+
+/**
+ * v1.21.0 (C2-2) — the full source set the inventory snapshot is built against,
+ * so every domain with stored rows reports `present` (not the default-cluster
+ * subset). The per-tool reads still re-scope to the exact domain, so widening
+ * the inventory probe never widens a figure read. This is the canonical enum
+ * (every `CoachScopeSource`) — the snapshot builder only emits a block when the
+ * matching source has rows, so probing the full set is presence-only.
+ */
+export const FULL_INVENTORY_SOURCE_SET: ReadonlyArray<CoachScopeSource> =
+  coachScopeSourceSchema.options;