fix(ai): keep lab values out of every model prompt while Labs is off

The Coach snapshot attached its labs block regardless of the module, a
decision from before Labs could be switched off, while the snapshot's own
prelude says a disabled domain never reaches the model. With Labs off, the
Coach prompt, its get_labs tool, the daily briefing's flagged-marker block,
the biomarker status note, the reaction line to a new panel and the MCP
lab_trend_brief prompt all still read lab values for a model.

Each of those reads now asks the labs module first and reads nothing when it
is off: the Coach tool answers module_disabled, the briefing omits the
block, the status note neither writes nor serves text, the reaction line
gets no value, and the MCP prompt refuses like get_labs and the doctor-visit
prompt already did. The data routes stay as they are. A structural guard
holds every lab-table reader under the model-input paths to the gate or to
a listed reason its rows never reach a model.

src/lib/ai/coach/__tests__/coach-history-reach-guard.test.ts

@@ -183,6 +183,7 @@ vi.mock("@/lib/tz/resolver", () => ({
 }));
 vi.mock("@/lib/modules/gate", () => ({
   resolveModuleMap: async () => ({}),
+  isModuleEnabled: async () => true,
 }));
 vi.mock("@/lib/ai/coach/persistence", () => ({
   readMessageResults: async () => null,

src/lib/ai/coach/__tests__/data-field-injection.test.ts

@@ -20,6 +20,19 @@ import { resolve } from "node:path";
 
 import { describe, expect, it, vi, beforeEach } from "vitest";
 
+// The labs module is on unless a test switches it off.
+const { labsModule } = vi.hoisted(() => ({ labsModule: { on: true } }));
+vi.mock("@/lib/modules/gate", async (importActual) => {
+  const actual = await importActual<typeof import("@/lib/modules/gate")>();
+  return {
+    ...actual,
+    isModuleEnabled: async (
+      userId: string,
+      key: Parameters<typeof actual.isModuleEnabled>[1],
+    ) => (key === "labs" ? labsModule.on : actual.isModuleEnabled(userId, key)),
+  };
+});
+
 vi.mock("@/lib/db", () => ({
   prisma: {
     labResult: { findMany: vi.fn() },

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

@@ -1,4 +1,17 @@
-import { describe, expect, it, vi, beforeEach } from "vitest";
+import { describe, expect, it, vi, beforeEach, onTestFinished } from "vitest";
+
+// The labs module is on unless a test switches it off.
+const { labsModule } = vi.hoisted(() => ({ labsModule: { on: true } }));
+vi.mock("@/lib/modules/gate", async (importActual) => {
+  const actual = await importActual<typeof import("@/lib/modules/gate")>();
+  return {
+    ...actual,
+    isModuleEnabled: async (
+      userId: string,
+      key: Parameters<typeof actual.isModuleEnabled>[1],
+    ) => (key === "labs" ? labsModule.on : actual.isModuleEnabled(userId, key)),
+  };
+});
 
 vi.mock("@/lib/db", () => ({
   prisma: {
@@ -45,6 +58,21 @@ beforeEach(() => {
 });
 
 describe("buildLabsSnapshotBlock", () => {
+  it("reads no lab row and answers null with the labs module off", async () => {
+    labsModule.on = false;
+    onTestFinished(() => {
+      labsModule.on = true;
+    });
+    prismaMock.labResult.findMany.mockResolvedValue([numericRow()]);
+    expect(await buildLabsSnapshotBlock("user_1", NOW)).toBeNull();
+    expect(
+      await buildLabsSnapshotBlock("user_1", NOW, undefined, {
+        analyte: "ldl",
+      }),
+    ).toBeNull();
+    expect(prismaMock.labResult.findMany).not.toHaveBeenCalled();
+  });
+
   it("returns null when the account has no readings", async () => {
     prismaMock.labResult.findMany.mockResolvedValue([]);
     const block = await buildLabsSnapshotBlock("user_1", NOW);

src/lib/ai/coach/__tests__/tools-executor.test.ts

@@ -5,7 +5,20 @@
  * audit asserts the model can always tell "no data" from "data".
  */
 import { DEFAULT_UNIT_PREFERENCES } from "@/lib/measurements/display-transform";
-import { describe, expect, it, vi, beforeEach } from "vitest";
+import { describe, expect, it, vi, beforeEach, onTestFinished } from "vitest";
+
+// The labs module is on unless a test switches it off.
+const { labsModule } = vi.hoisted(() => ({ labsModule: { on: true } }));
+vi.mock("@/lib/modules/gate", async (importActual) => {
+  const actual = await importActual<typeof import("@/lib/modules/gate")>();
+  return {
+    ...actual,
+    isModuleEnabled: async (
+      userId: string,
+      key: Parameters<typeof actual.isModuleEnabled>[1],
+    ) => (key === "labs" ? labsModule.on : actual.isModuleEnabled(userId, key)),
+  };
+});
 
 import type { CoachSnapshotResult } from "@/lib/ai/coach/snapshot";
 
@@ -267,6 +280,21 @@ describe("executeCoachTool", () => {
   // can cite the reading, not just name the biomarker. The snapshot labs block
   // already carries { analyte, value, unit, rangeStatus, … }; the tool passes
   // it through verbatim. This guards that the value + unit survive the tool.
+  it("get_labs answers module_disabled with the labs module off", async () => {
+    labsModule.on = false;
+    onTestFinished(() => {
+      labsModule.on = true;
+    });
+    buildCoachSnapshot.mockClear();
+    const result = await executeCoachTool({
+      userId: "u1",
+      name: "get_labs",
+      rawArguments: "{}",
+    });
+    expect(result).toMatchObject({ present: false, reason: "module_disabled" });
+    expect(buildCoachSnapshot).not.toHaveBeenCalled();
+  });
+
   it("get_labs carries each reading's value and unit (citation guarantee)", async () => {
     buildCoachSnapshot.mockResolvedValue(
       snapshot({

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

@@ -46,10 +46,12 @@
  * `labs_read` tool result, so sanitisation lives here at the shared source.
  *
  * `userId` is narrowed from the authenticated session by the caller and feeds
- * the Prisma `where` field-by-field; it is never an input. Unlike the illness
- * block, Labs is intentionally NOT module-gated (mirrors `/api/labs` — the data
- * is always owner-scoped and safe to read), so the block is `null` only when the
- * account has no recent readings.
+ * the Prisma `where` field-by-field; it is never an input. Like the illness
+ * block it is module-gated: with the `labs` module off the block is `null`
+ * and no lab row is read, so neither the Coach prompt nor its `get_labs` tool
+ * sees a value. It used to ride regardless, a decision from before Labs could
+ * be switched off; the data routes (`/api/labs`) stay ungated, because a
+ * module decides what a model is given, not what the owner can read.
  */
 import { sameLabUnit } from "@/lib/labs/unit-normalise";
 import {
@@ -61,6 +63,7 @@ import { classifyAgainstEffectiveRange } from "@/lib/labs/reference-range";
 import { resolveLabFields } from "@/lib/labs/serialise";
 import { sanitizeForPrompt } from "@/lib/insights/sanitize";
 import { prisma } from "@/lib/db";
+import { isModuleEnabled } from "@/lib/modules/gate";
 
 /** Cap on distinct biomarkers in the block (newest reading first). */
 const MAX_BIOMARKERS = 24;
@@ -235,6 +238,7 @@ export async function buildLabsSnapshotBlock(
     analyte?: string;
   } = {},
 ): Promise<CoachLabsBlock | null> {
+  if (!(await isModuleEnabled(userId, "labs"))) return null;
   const wanted = options.analyte?.trim().toLowerCase() || null;
   const floor = reachFloor(reach, now);
 

src/lib/ai/coach/snapshot.ts

@@ -666,9 +666,8 @@ async function buildCoachSnapshotImpl(
 
   // v1.18.11 (#65) — lab-result context. Like illness it is CONTEXT, not a
   // scope-gated metric: attached without a `registerBlock` so the budget
-  // degrader never sheds it, and Labs is intentionally not module-gated (the
-  // helper reads owner-scoped rows directly, mirroring `/api/labs`). The block
-  // carries the most-recent resolved reading per biomarker (last 12 months,
+  // degrader never sheds it. The helper is module-gated internally: with the
+  // labs module off it reads nothing and answers null. The block carries the most-recent resolved reading per biomarker (last 12 months,
   // capped) so the Coach can answer "what was my LDL" without re-deriving.
   const labsBlockPromise = buildLabsSnapshotBlock(userId, now, reach);
 

src/lib/ai/coach/tools/__tests__/__snapshots__/coach-turn-tool-defs.snap

@@ -137,7 +137,7 @@
   },
   {
     "name": "get_labs",
-    "description": "Fetch the user's lab results over the whole record (or the user's lookback limit, when there is one): without arguments the latest reading per biomarker. Pass an analyte for how it changed over time: each matching marker then carries a history, the newest earlier values in full and older ones as one mean / min / max / count per year. Returns { present: false } with a reason — no_data means no labs are on file, outside_reach means they are older than the user's lookback limit.",
+    "description": "Fetch the user's lab results over the whole record (or the user's lookback limit, when there is one): without arguments the latest reading per biomarker. Pass an analyte for how it changed over time: each matching marker then carries a history, the newest earlier values in full and older ones as one mean / min / max / count per year. Returns { present: false } with a reason — no_data means no labs are on file, outside_reach means they are older than the user's lookback limit, module_disabled means the user switched the labs module off.",
     "parameters": {
       "type": "object",
       "additionalProperties": false,

src/lib/ai/coach/tools/definitions.ts

@@ -321,7 +321,7 @@ export const COACH_TOOL_DEFS: AiToolDef[] = [
   {
     name: "get_labs",
     description:
-      "Fetch the user's lab results over the whole record (or the user's lookback limit, when there is one): without arguments the latest reading per biomarker. Pass an analyte for how it changed over time: each matching marker then carries a history, the newest earlier values in full and older ones as one mean / min / max / count per year. Returns { present: false } with a reason — no_data means no labs are on file, outside_reach means they are older than the user's lookback limit.",
+      "Fetch the user's lab results over the whole record (or the user's lookback limit, when there is one): without arguments the latest reading per biomarker. Pass an analyte for how it changed over time: each matching marker then carries a history, the newest earlier values in full and older ones as one mean / min / max / count per year. Returns { present: false } with a reason — no_data means no labs are on file, outside_reach means they are older than the user's lookback limit, module_disabled means the user switched the labs module off.",
     parameters: {
       type: "object",
       additionalProperties: false,

src/lib/ai/coach/tools/run/get-labs.ts

@@ -2,6 +2,7 @@ import { buildCoachSnapshot } from "@/lib/ai/coach/snapshot";
 import { buildLabsSnapshotBlock } from "@/lib/ai/coach/labs-snapshot";
 import type { CoachScope, CoachScopeWindow } from "@/lib/ai/coach/types";
 import type { CoachHistoryReach } from "@/lib/ai/coach/history-reach";
+import { isModuleEnabled } from "@/lib/modules/gate";
 import { getLabsArgsSchema } from "../definitions";
 import { subjectForTool } from "../availability";
 import { badArgs, emptyRead, pickSection, scopeFor } from "./shared";
@@ -16,6 +17,11 @@ export async function getLabs(
 ): Promise<CoachToolResult> {
   const parsed = getLabsArgsSchema.safeParse(rawArgs);
   if (!parsed.success) return badArgs("get_labs", parsed.error);
+  // The labs module off: said as such, not probed for rows (the block below
+  // would be empty and the availability probe would count lab rows).
+  if (!(await isModuleEnabled(userId, "labs"))) {
+    return { present: false, reason: "module_disabled" };
+  }
   // Labs ride the snapshot regardless of `sources` (attached unconditionally),
   // so a minimal scope still surfaces them.
   //

src/lib/insights/__tests__/biomarker-status.test.ts

@@ -1,4 +1,17 @@
-import { describe, expect, it, vi, beforeEach } from "vitest";
+import { describe, expect, it, vi, beforeEach, onTestFinished } from "vitest";
+
+// The labs module is on unless a test switches it off.
+const { labsModule } = vi.hoisted(() => ({ labsModule: { on: true } }));
+vi.mock("@/lib/modules/gate", async (importActual) => {
+  const actual = await importActual<typeof import("@/lib/modules/gate")>();
+  return {
+    ...actual,
+    isModuleEnabled: async (
+      userId: string,
+      key: Parameters<typeof actual.isModuleEnabled>[1],
+    ) => (key === "labs" ? labsModule.on : actual.isModuleEnabled(userId, key)),
+  };
+});
 
 vi.mock("@/lib/db", () => ({
   prisma: {
@@ -108,6 +121,25 @@ beforeEach(() => {
   vi.mocked(prisma.user.findUnique).mockResolvedValue(null as never);
 });
 
+describe("generateBiomarkerStatus — labs module", () => {
+  it("writes and serves nothing about a marker with the labs module off", async () => {
+    labsModule.on = false;
+    onTestFinished(() => {
+      labsModule.on = true;
+    });
+    const result = await generateBiomarkerStatus({
+      biomarkerId: MARKER.id,
+      userId: "u1",
+      locale: "en",
+      force: true,
+    });
+    expect(result.text).toBeNull();
+    expect(runStatusCompletion).not.toHaveBeenCalled();
+    expect(prisma.labResult.findMany).not.toHaveBeenCalled();
+    expect(prisma.insightStatusCache.findUnique).not.toHaveBeenCalled();
+  });
+});
+
 describe("generateBiomarkerStatus — empty-data guard", () => {
   it("returns insufficient WITHOUT calling the provider for a marker with no numeric readings", async () => {
     vi.mocked(prisma.labResult.findMany).mockResolvedValue([] as never);

src/lib/insights/__tests__/features.test.ts

@@ -1,4 +1,17 @@
-import { describe, expect, it, vi, beforeEach } from "vitest";
+import { describe, expect, it, vi, beforeEach, onTestFinished } from "vitest";
+
+// The labs module is on unless a test switches it off.
+const { labsModule } = vi.hoisted(() => ({ labsModule: { on: true } }));
+vi.mock("@/lib/modules/gate", async (importActual) => {
+  const actual = await importActual<typeof import("@/lib/modules/gate")>();
+  return {
+    ...actual,
+    isModuleEnabled: async (
+      userId: string,
+      key: Parameters<typeof actual.isModuleEnabled>[1],
+    ) => (key === "labs" ? labsModule.on : actual.isModuleEnabled(userId, key)),
+  };
+});
 
 vi.mock("@/lib/db", () => ({
   prisma: {
@@ -410,6 +423,25 @@ describe("extractFeatures — weight target direction (#1006)", () => {
 });
 
 describe("extractFeatures — v1.22 labs briefing block", () => {
+  it("leaves the labs out of the briefing with the labs module off", async () => {
+    labsModule.on = false;
+    onTestFinished(() => {
+      labsModule.on = true;
+    });
+    prismaMock.labResult.findMany.mockResolvedValue([
+      labRow({
+        analyte: "LDL",
+        value: 200,
+        referenceLow: 0,
+        referenceHigh: 130,
+        daysAgo: 5,
+      }),
+    ]);
+    const f = await extractFeatures("user-1", false);
+    expect(f.labs).toBeUndefined();
+    expect(prismaMock.labResult.findMany).not.toHaveBeenCalled();
+  });
+
   it("surfaces an abnormal (out-of-range) biomarker", async () => {
     prismaMock.labResult.findMany.mockResolvedValue([
       labRow({

src/lib/insights/biomarker-status.ts

@@ -21,6 +21,7 @@
  * `insufficient` marker WITHOUT touching the provider chain.
  */
 import { prisma } from "@/lib/db";
+import { isModuleEnabled } from "@/lib/modules/gate";
 import { PROMPT_VERSION } from "@/lib/ai/prompts/base-system";
 import { AI_BUDGETS } from "@/lib/ai/ai-budgets";
 import {
@@ -130,6 +131,11 @@ export async function generateBiomarkerStatus(args: {
     // Unknown / cross-user marker — degrade gracefully rather than throwing.
     return insufficient();
   }
+  // With the labs module off no model writes about a marker, and text it
+  // wrote while the module was on is not served either.
+  if (!(await isModuleEnabled(args.userId, "labs"))) {
+    return { hasProvider: true, text: null, cached: false, updatedAt: null };
+  }
 
   const prepared = await prepareBiomarkerStatus(marker, args);
   return (await runPreparedStatusCard(prepared)) as BiomarkerStatusResult;

src/lib/insights/feature-blocks.ts

@@ -20,6 +20,7 @@ import {
 import { classifyAgainstEffectiveRange } from "@/lib/labs/reference-range";
 import { calendarDaysUntil } from "@/lib/measurement-reminders/due-day";
 import { resolveLabFields } from "@/lib/labs/serialise";
+import { isModuleEnabled } from "@/lib/modules/gate";
 import {
   readRollupBuckets,
   ROLLUP_FOLD_WINDOW_MS,
@@ -346,12 +347,15 @@ function sanitizeLabel(text: string, max = 80): string {
  * Most-recent reading per biomarker over the lookback window; hidden markers
  * excluded; qualitative rows neutral. Only abnormal (below/above) OR trending
  * markers surface, bounded. Returns `undefined` when nothing is flagged so the
- * block is omitted rather than emitting an empty shape.
+ * block is omitted rather than emitting an empty shape, and when the `labs`
+ * module is off, before any row is read: the briefing prompt never carries a
+ * switched-off domain.
  */
 export async function readLabsBriefingBlock(
   userId: string,
   now: number,
 ): Promise<AggregatedFeatures["labs"] | undefined> {
+  if (!(await isModuleEnabled(userId, "labs"))) return undefined;
   const nowDate = new Date(now);
   const cutoff = new Date(nowDate);
   cutoff.setMonth(cutoff.getMonth() - LABS_LOOKBACK_MONTHS);

src/lib/jobs/__tests__/reaction-line-degradation.test.ts

@@ -14,7 +14,20 @@
  * still surface the chip. The last assertion of each case is the one that
  * matters: `justIn` survives.
  */
-import { describe, it, expect, vi, beforeEach } from "vitest";
+import { describe, it, expect, vi, beforeEach, onTestFinished } from "vitest";
+
+// The labs module is on unless a test switches it off.
+const { labsModule } = vi.hoisted(() => ({ labsModule: { on: true } }));
+vi.mock("@/lib/modules/gate", async (importActual) => {
+  const actual = await importActual<typeof import("@/lib/modules/gate")>();
+  return {
+    ...actual,
+    isModuleEnabled: async (
+      userId: string,
+      key: Parameters<typeof actual.isModuleEnabled>[1],
+    ) => (key === "labs" ? labsModule.on : actual.isModuleEnabled(userId, key)),
+  };
+});
 
 import { getServerTranslator } from "@/lib/i18n/server-translator";
 import { buildDailyDigest, type DailyDigestInput } from "@/lib/daily/digest";
@@ -336,6 +349,31 @@ describe("reaction line — degradation", () => {
     expectSurfaceStillWorks();
   });
 
+  it("gives the model no lab value once the labs module is off", async () => {
+    labsModule.on = false;
+    onTestFinished(() => {
+      labsModule.on = true;
+    });
+    labResultFindMany.mockResolvedValue([
+      { analyte: "LDL", value: 190, valueText: null, unit: "mg/dL" },
+    ]);
+    const generateCompletion = vi.fn().mockResolvedValue({
+      content: "A new lab panel arrived.",
+      tokensUsed: 300,
+      cachedInputTokens: 0,
+    });
+    resolveProviderChain.mockResolvedValue([
+      { providerType: "openai", instance: { generateCompletion } },
+    ]);
+
+    await runReactionLine({ ...JOB, kind: "labs_panel" });
+
+    expect(labResultFindMany).not.toHaveBeenCalled();
+    for (const [request] of generateCompletion.mock.calls) {
+      expect(JSON.stringify(request)).not.toContain("190");
+    }
+  });
+
   it("fences free-text lab fields as data, never prompt instructions", async () => {
     labResultFindMany.mockResolvedValue([
       {

src/lib/jobs/reaction-line-labs.ts

@@ -0,0 +1,40 @@
+/**
+ * The new lab panel a reaction line is written about, as evidence lines for
+ * the model (`loadArrivalEvidence` in `./reaction-line`).
+ *
+ * Module-gated: an arrival is only emitted with Labs on, but its job can run
+ * after the owner switched the module off, and then the model gets no value.
+ */
+import { fenceUserText } from "@/lib/ai/coach/data-fence";
+import { prisma } from "@/lib/db";
+import { isModuleEnabled } from "@/lib/modules/gate";
+
+/** Up to eight results of the panel, fenced; null when there is nothing to say. */
+export async function labsPanelEvidence(
+  userId: string,
+  arrival: { occurredAt: Date; refId: string | null },
+): Promise<string | null> {
+  if (!(await isModuleEnabled(userId, "labs"))) return null;
+  const labs = await prisma.labResult.findMany({
+    where: {
+      userId,
+      takenAt: arrival.occurredAt,
+      deletedAt: null,
+      ...(arrival.refId ? { panel: arrival.refId } : {}),
+    },
+    select: { analyte: true, value: true, valueText: true, unit: true },
+    orderBy: { analyte: "asc" },
+    take: 8,
+  });
+  if (labs.length === 0) return null;
+  return labs
+    .map((lab) => {
+      const value =
+        lab.value === null
+          ? fenceUserText(lab.valueText ?? "not reported")
+          : String(lab.value);
+      const unit = lab.unit ? ` ${fenceUserText(lab.unit)}` : "";
+      return `- Newly arrived lab result: ${fenceUserText(lab.analyte)} ${value}${unit}.`;
+    })
+    .join("\n");
+}

src/lib/jobs/reaction-line.ts

@@ -57,7 +57,7 @@ import {
 } from "@/lib/ai/coach/coach-prose-grounding";
 import { extractAssessmentSummary } from "@/lib/insights/status-shared";
 import { encryptToBytes } from "@/lib/ai/coach/bytes-codec";
-import { fenceUserText } from "@/lib/ai/coach/data-fence";
+import { labsPanelEvidence } from "@/lib/jobs/reaction-line-labs";
 import { SESSION_USER_SELECT } from "@/lib/auth/session-user";
 import { singleUserTurn, type CompletionResult } from "@/lib/ai/types";
 import type { Locale } from "@/lib/i18n/config";
@@ -267,29 +267,8 @@ export async function loadArrivalEvidence(
   }
 
   if (job.kind === "labs_panel") {
-    const labs = await prisma.labResult.findMany({
-      where: {
-        userId: job.userId,
-        takenAt: row.occurredAt,
-        deletedAt: null,
-        ...(row.refId ? { panel: row.refId } : {}),
-      },
-      select: { analyte: true, value: true, valueText: true, unit: true },
-      orderBy: { analyte: "asc" },
-      take: 8,
-    });
-    if (labs.length > 0) {
-      return labs
-        .map((lab) => {
-          const value =
-            lab.value === null
-              ? fenceUserText(lab.valueText ?? "not reported")
-              : String(lab.value);
-          const unit = lab.unit ? ` ${fenceUserText(lab.unit)}` : "";
-          return `- Newly arrived lab result: ${fenceUserText(lab.analyte)} ${value}${unit}.`;
-        })
-        .join("\n");
-    }
+    const lines = await labsPanelEvidence(job.userId, row);
+    if (lines) return lines;
   }
 
   return "- The arrival marker was written, but its exact value is unavailable.";

src/lib/mcp/__tests__/prompts.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, vi, beforeEach } from "vitest";
+import { describe, it, expect, vi, beforeEach, onTestFinished } from "vitest";
 
 vi.mock("@/lib/modules/gate", () => ({
   isModuleEnabled: vi.fn(async () => true),
@@ -457,6 +457,21 @@ describe("sleep_review", () => {
 });
 
 describe("lab_trend_brief", () => {
+  it("refuses with the labs module off and reads no lab row", async () => {
+    const { isModuleEnabled } = await import("@/lib/modules/gate");
+    vi.mocked(isModuleEnabled).mockImplementation(
+      async (_userId, key) => key !== "labs",
+    );
+    onTestFinished(() => {
+      vi.mocked(isModuleEnabled).mockImplementation(async () => true);
+    });
+    vi.mocked(prisma.labResult.findMany).mockClear();
+    await expect(prompt("lab_trend_brief").run(CTX, {})).rejects.toThrow(
+      /"labs" module is turned off/,
+    );
+    expect(prisma.labResult.findMany).not.toHaveBeenCalled();
+  });
+
   it("builds a per-analyte trajectory with stored ranges + status, latest first", async () => {
     vi.mocked(prisma.labResult.findMany).mockResolvedValue([
       {

src/lib/mcp/prompts.ts

@@ -567,6 +567,18 @@ export const MCP_PROMPTS: McpPromptDefinition[] = [
       "Assemble a grounded per-analyte lab trajectory — latest reading vs prior readings, against the stored reference range, for one named analyte or across the panel. Reads the user's own lab store directly (the latest-only labs tool can't show a trend). Reference ranges are the lab's own stored bounds, never recomputed. Facts only: no diagnosis, no verdict.",
     argsShape: { analyte: z.string().min(1).max(80).optional() },
     async run(ctx, args) {
+      // The same door `get_labs` has: refuse with the module off rather than
+      // hand the assistant an empty panel to narrate as "no labs on file".
+      if (!(await isModuleEnabled(ctx.userId, "labs"))) {
+        annotate({
+          action: { name: "mcp.prompt.invoked" },
+          meta: { prompt: "lab_trend_brief", refused: "module_disabled" },
+        });
+        throw new Error(
+          'The "labs" module is turned off for this account, so the lab trend ' +
+            "brief is not available.",
+        );
+      }
       const analyte =
         typeof args.analyte === "string" && args.analyte.trim() !== ""
           ? args.analyte.trim()