diff --git a/src/__tests__/apple-health-unit-audit-guard.test.ts b/src/__tests__/apple-health-unit-audit-guard.test.ts
index b8799aeaf..070472f32 100644
--- a/src/__tests__/apple-health-unit-audit-guard.test.ts
+++ b/src/__tests__/apple-health-unit-audit-guard.test.ts
@@ -48,6 +48,7 @@ import {
   convertHkValue,
   isConvertibleHkUnit,
 } from "@/lib/measurements/hk-units";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 const ENTRIES = Object.values(APPLE_HEALTH_TYPE_MAP);
 
@@ -193,10 +194,10 @@ describe("Apple Health mapping — the record's own unit (issue #944)", () => {
       "utf8",
     );
     expect(archive).toContain(optIn);
-    const batch = readFileSync(
-      join(process.cwd(), "src/app/api/measurements/batch/route.ts"),
-      "utf8",
-    );
+    const batch = readSource("src/app/api/measurements/batch/route.ts", [
+      "export const POST",
+      "hkIdentifier",
+    ]);
     expect(
       batch,
       "the batch route opted into record-unit conversion",
diff --git a/src/__tests__/helpers/prisma-schema-names.ts b/src/__tests__/helpers/prisma-schema-names.ts
index b9e187e12..f45171d02 100644
--- a/src/__tests__/helpers/prisma-schema-names.ts
+++ b/src/__tests__/helpers/prisma-schema-names.ts
@@ -171,5 +171,16 @@ export function readDeclaredSchema(
     };
   });
 
+  // Every consumer compares this against an allowlist or a "none of these"
+  // rule, which an empty parse satisfies. For the real schema, this little is
+  // a broken read (a moved file, a block regex that stopped matching), not a
+  // schema. A synthetic schema a test writes itself is exempt.
+  if (schemaPath === SCHEMA_PATH && (models.length < 50 || enums.length < 10)) {
+    throw new Error(
+      `readDeclaredSchema(${schemaPath}): parsed ${models.length} model(s) and ` +
+        `${enums.length} enum(s), below the floor of 50 and 10. Fix the parser ` +
+        `before trusting a guard built on it.`,
+    );
+  }
   return { enums, models };
 }
diff --git a/src/__tests__/helpers/source-files.ts b/src/__tests__/helpers/source-files.ts
index 15a5da508..70e92385a 100644
--- a/src/__tests__/helpers/source-files.ts
+++ b/src/__tests__/helpers/source-files.ts
@@ -50,7 +50,7 @@
  * worktrees, each a full second copy of the tree that would double every
  * match. Every caller roots at `src/`, `e2e/` or a subtree of one.
  */
-import { readdirSync, readFileSync } from "node:fs";
+import { existsSync, readdirSync, readFileSync } from "node:fs";
 import { join, sep } from "node:path";
 
 export function walkSourceFiles(
@@ -229,3 +229,82 @@ export function scanSourceMatches(
     options.matchFloor,
   ) as SourceMatch[];
 }
+
+/** Something a file must still contain for a read of it to mean anything. */
+export type SourceAnchor = string | RegExp;
+
+function anchorCount(text: string, anchor: SourceAnchor): number {
+  if (typeof anchor === "string") return text.split(anchor).length - 1;
+  const flags = anchor.flags.includes("g") ? anchor.flags : `${anchor.flags}g`;
+  return [...text.matchAll(new RegExp(anchor.source, flags))].length;
+}
+
+/**
+ * Read one source file by path, and prove it is still the file the guard is
+ * about.
+ *
+ * A guard that reads a fixed path and asserts that something is ABSENT
+ * (`expect(source).not.toMatch(…)`) is green on a file that has been split:
+ * the code it watched moved next door, the old path holds whatever is left,
+ * and the absence is true for the wrong reason. A missing file at least
+ * throws; a file that kept its name but lost its contents does not.
+ *
+ * So the caller names at least one anchor: a string or pattern the watched
+ * code itself carries (the function the guard is about, the call it pins).
+ * Every anchor must match at least once, or this throws and names the file,
+ * which is the moment to point the guard at the new home (or at a folder
+ * with `readSourceFolder`). `rel` is relative to the repository root.
+ */
+export function readSource(
+  rel: string,
+  anchors: SourceAnchor | readonly SourceAnchor[],
+): string {
+  const list = (Array.isArray(anchors) ? anchors : [anchors]) as SourceAnchor[];
+  if (list.length === 0) {
+    throw new Error(
+      `readSource(${rel}): name at least one anchor the watched code carries.`,
+    );
+  }
+  const path = join(process.cwd(), rel);
+  if (!existsSync(path)) {
+    throw new Error(
+      `readSource(${rel}): the file does not exist. If it was split or moved, ` +
+        `point the guard at the new location or scan the folder with ` +
+        `readSourceFolder and a floor.`,
+    );
+  }
+  const text = readFileSync(path, "utf8");
+  const lost = list.filter((anchor) => anchorCount(text, anchor) === 0);
+  if (lost.length > 0) {
+    throw new Error(
+      `readSource(${rel}): the file no longer contains ${lost
+        .map(String)
+        .join(", ")}. The code this guard watches has moved; a negative ` +
+        `assertion on this file would now pass for the wrong reason.`,
+    );
+  }
+  return text;
+}
+
+/**
+ * Read every source file under a folder (relative to the repository root),
+ * with a floor on how many it found: the folder-scan form of `readSource`
+ * for a guard whose subject was split into several files. Returns
+ * `[path relative to the folder, text]` pairs, sorted.
+ */
+export function readSourceFolder(
+  relDir: string,
+  options: {
+    floor: number;
+    include?: (rel: string) => boolean;
+    extensions?: readonly string[];
+  },
+): Array<[string, string]> {
+  const root = join(process.cwd(), relDir);
+  const files = walkSourceFiles(root, {
+    floor: options.floor,
+    extensions: options.extensions,
+  }).filter(options.include ?? (() => true));
+  requireFloor(`readSourceFolder(${relDir})`, files, options.floor);
+  return files.map((rel) => [rel, readFileSync(join(root, rel), "utf8")]);
+}
diff --git a/src/__tests__/helpers/wipe-schema-shape.ts b/src/__tests__/helpers/wipe-schema-shape.ts
index 1e6f915f2..51a80a736 100644
--- a/src/__tests__/helpers/wipe-schema-shape.ts
+++ b/src/__tests__/helpers/wipe-schema-shape.ts
@@ -38,6 +38,12 @@ export function parseWipeSchema(
   const blocks = [...schema.matchAll(/^model\s+(\w+)\s*\{([\s\S]*?)^\}/gm)].map(
     (m) => ({ name: m[1], body: m[2] }),
   );
+  if (schemaPath === WIPE_SCHEMA_PATH && blocks.length < 50) {
+    throw new Error(
+      `parseWipeSchema(${schemaPath}): parsed ${blocks.length} model(s), below ` +
+        `the floor of 50. A wipe guard over an empty parse passes on nothing.`,
+    );
+  }
   const modelNames = new Set(blocks.map((b) => b.name));
 
   const out = new Map<string, ModelShape>();
diff --git a/src/__tests__/moodlog-removal-guard.test.ts b/src/__tests__/moodlog-removal-guard.test.ts
index 6bd82e6a3..6eccca904 100644
--- a/src/__tests__/moodlog-removal-guard.test.ts
+++ b/src/__tests__/moodlog-removal-guard.test.ts
@@ -22,6 +22,7 @@ import { describe, expect, it } from "vitest";
 
 import { INTEGRATION_CADENCE } from "@/lib/integrations/sync-verdict";
 import { INTEGRATION_DISPLAY_NAMES } from "@/components/settings/integrations/integration-fallback-row";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 const ROOT = path.resolve(__dirname, "../..");
 
@@ -65,9 +66,9 @@ describe("moodLog integration stays removed", () => {
   });
 
   it("registers no moodlog queue, cron or handler binding", () => {
-    const registrar = readFileSync(
-      path.join(ROOT, "src/lib/jobs/reminder/register-integration-sync.ts"),
-      "utf8",
+    const registrar = readSource(
+      "src/lib/jobs/reminder/register-integration-sync.ts",
+      "export async function registerIntegrationSyncQueues",
     );
     expect(registrar).not.toContain("moodlog");
     expect(registrar).not.toContain("MoodLog");
diff --git a/src/__tests__/source-read-helpers.test.ts b/src/__tests__/source-read-helpers.test.ts
new file mode 100644
index 000000000..05fb28e7a
--- /dev/null
+++ b/src/__tests__/source-read-helpers.test.ts
@@ -0,0 +1,55 @@
+/**
+ * `readSource` and `readSourceFolder`: the reads a path-pinned guard goes
+ * through, so a split file fails the guard instead of leaving it green.
+ */
+import { describe, expect, it } from "vitest";
+
+import { readSource, readSourceFolder } from "./helpers/source-files";
+
+const HERE = "src/__tests__/helpers/source-files.ts";
+
+describe("readSource", () => {
+  it("returns the text when every anchor is present", () => {
+    const text = readSource(HERE, [
+      "export function readSource(",
+      /export function walkSourceFiles\(/,
+    ]);
+    expect(text.length).toBeGreaterThan(1000);
+  });
+
+  it("throws on a file that does not exist", () => {
+    expect(() => readSource("src/lib/does-not-exist.ts", "anything")).toThrow(
+      /does not exist/,
+    );
+  });
+
+  it("throws when an anchor no longer matches", () => {
+    expect(() =>
+      readSource(HERE, ["export function readSource(", "noSuchAnchorHere"]),
+    ).toThrow(/no longer contains noSuchAnchorHere/);
+    expect(() => readSource(HERE, /export function neverDeclared\(/)).toThrow(
+      /no longer contains/,
+    );
+  });
+
+  it("refuses a read without an anchor", () => {
+    expect(() => readSource(HERE, [])).toThrow(/at least one anchor/);
+  });
+});
+
+describe("readSourceFolder", () => {
+  it("returns the files with their text, above the floor", () => {
+    const files = readSourceFolder("src/__tests__/helpers", { floor: 5 });
+    expect(files.length).toBeGreaterThanOrEqual(5);
+    expect(files.map(([rel]) => rel)).toContain("source-files.ts");
+  });
+
+  it("throws when the folder holds fewer files than the floor", () => {
+    expect(() =>
+      readSourceFolder("src/__tests__/helpers", {
+        floor: 1,
+        include: (rel) => rel === "nothing-matches.ts",
+      }),
+    ).toThrow(/below the stated floor/);
+  });
+});
diff --git a/src/app/__tests__/dashboard-hrv-rmssd-fallback.test.tsx b/src/app/__tests__/dashboard-hrv-rmssd-fallback.test.tsx
index c063d13c1..6ed76d946 100644
--- a/src/app/__tests__/dashboard-hrv-rmssd-fallback.test.tsx
+++ b/src/app/__tests__/dashboard-hrv-rmssd-fallback.test.tsx
@@ -19,6 +19,7 @@ import {
 import { moduleForMeasurementType } from "@/lib/modules/measurement-scope";
 import { locales } from "@/lib/i18n/config";
 import type { DataSummary } from "@/lib/analytics/trends";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 /**
  * The dashboard HRV tile must accept either HRV type.
@@ -250,10 +251,10 @@ describe("the tile the user actually sees", () => {
     // current formatting of the replacement, so reformatting cannot break
     // it. Freshness is per-type and captioning a live RMSSD tile from the
     // SDNN lookup is the failure it guards.
-    const page = readFileSync(
-      join(process.cwd(), "src/app/page-client.tsx"),
-      "utf8",
-    );
+    const page = readSource("src/app/page-client.tsx", [
+      "const tileStaleDays",
+      "HEART_RATE_VARIABILITY",
+    ]);
     expect(page).not.toContain('tileStaleDays("HEART_RATE_VARIABILITY")');
     expect(page).not.toContain(
       "const hrvSummary = data?.summaries?.HEART_RATE_VARIABILITY",
diff --git a/src/app/api/tokens/__tests__/route.test.ts b/src/app/api/tokens/__tests__/route.test.ts
index 2c757c67d..e273d971d 100644
--- a/src/app/api/tokens/__tests__/route.test.ts
+++ b/src/app/api/tokens/__tests__/route.test.ts
@@ -40,6 +40,7 @@ import { DELETE } from "../[id]/route";
 import { requireAuth } from "@/lib/api-handler";
 import { prisma } from "@/lib/db";
 import { isApiGloballyEnabled } from "@/lib/app-settings";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 const USER = { id: "user-1", username: "u" };
 
@@ -168,11 +169,9 @@ describe("the switch and the authentication path", () => {
     // a token would NOT be live during the outage and hiding the list would
     // stop being wrong. This reads the source because the behaviour is an
     // absence, and an absence has no call to spy on.
-    const { readFileSync } = await import("node:fs");
-    const { join } = await import("node:path");
-    const source = readFileSync(
-      join(process.cwd(), "src/lib/api-handler.ts"),
-      "utf8",
+    const source = readSource(
+      "src/lib/api-handler.ts",
+      "export async function requireAuth(",
     );
     expect(source).not.toContain("isApiGloballyEnabled");
     expect(source).not.toContain("apiGlobal");
diff --git a/src/app/insights/__tests__/header-add-pattern.test.ts b/src/app/insights/__tests__/header-add-pattern.test.ts
index 72f9616a8..5dc8179ee 100644
--- a/src/app/insights/__tests__/header-add-pattern.test.ts
+++ b/src/app/insights/__tests__/header-add-pattern.test.ts
@@ -14,6 +14,7 @@
 import { readdirSync, readFileSync, statSync } from "node:fs";
 import { join, relative } from "node:path";
 import { describe, expect, it } from "vitest";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 const ROOT = process.cwd();
 const INSIGHTS = join(ROOT, "src/app/insights");
@@ -52,7 +53,10 @@ describe("Insights add actions", () => {
   });
 
   it("the mood page has no text links into logging or the check-in", () => {
-    const source = readFileSync(join(INSIGHTS, "mood/page-client.tsx"), "utf8");
+    const source = readSource(
+      "src/app/insights/mood/page-client.tsx",
+      "<SubPageAddButton",
+    );
     expect(source).not.toMatch(/<Link\s+href="\/mood"\s+data-slot/);
     expect(source).not.toContain('href="/mental-wellbeing"');
     expect(source).not.toContain("insights.mood.mentalWellbeingLink");
diff --git a/src/app/insights/sleep/__tests__/empty-state-href.test.ts b/src/app/insights/sleep/__tests__/empty-state-href.test.ts
index 0e3d1f414..d6c7a0df2 100644
--- a/src/app/insights/sleep/__tests__/empty-state-href.test.ts
+++ b/src/app/insights/sleep/__tests__/empty-state-href.test.ts
@@ -11,6 +11,7 @@ import { join } from "node:path";
 import { describe, expect, it } from "vitest";
 
 import { isSettingsSectionSlug } from "@/lib/settings/section-slugs";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 describe("sleep empty-state CTA href", () => {
   it("links to /settings/integrations (a real settings slug)", () => {
@@ -29,9 +30,9 @@ describe("sleep empty-state CTA href", () => {
   });
 
   it("never links to the removed /settings/data-sources slug", () => {
-    const source = readFileSync(
-      join(process.cwd(), "src/app/insights/sleep/page.tsx"),
-      "utf8",
+    const source = readSource(
+      "src/app/insights/sleep/page.tsx",
+      "<MetricEmptyState",
     );
     expect(source).not.toContain("/settings/data-sources");
   });
diff --git a/src/components/insights/__tests__/sleep-overview-empty-href.test.ts b/src/components/insights/__tests__/sleep-overview-empty-href.test.ts
index 441a7b5f2..e5c569ed6 100644
--- a/src/components/insights/__tests__/sleep-overview-empty-href.test.ts
+++ b/src/components/insights/__tests__/sleep-overview-empty-href.test.ts
@@ -12,6 +12,7 @@ import { join } from "node:path";
 import { describe, expect, it } from "vitest";
 
 import { isSettingsSectionSlug } from "@/lib/settings/section-slugs";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 describe("sleep-overview empty-state CTA href", () => {
   it("links to /settings/integrations (a real settings slug)", () => {
@@ -30,9 +31,9 @@ describe("sleep-overview empty-state CTA href", () => {
   });
 
   it("never links to the non-existent /settings/devices slug", () => {
-    const source = readFileSync(
-      join(process.cwd(), "src/components/insights/sleep-overview.tsx"),
-      "utf8",
+    const source = readSource(
+      "src/components/insights/sleep-overview.tsx",
+      "<EmptyState",
     );
     expect(source).not.toContain("/settings/devices");
   });
diff --git a/src/components/layout/__tests__/sidebar-nav.test.tsx b/src/components/layout/__tests__/sidebar-nav.test.tsx
index d2a47f420..8195a4f9a 100644
--- a/src/components/layout/__tests__/sidebar-nav.test.tsx
+++ b/src/components/layout/__tests__/sidebar-nav.test.tsx
@@ -66,6 +66,7 @@ import {
 import { ADMIN_SECTIONS } from "@/components/admin/admin-shell";
 import { visibleUtilityDestinations } from "../nav-model";
 import { delegatedDomains } from "@/lib/sharing/domain-write-support";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 function render({
   pathname = "/",
@@ -565,9 +566,9 @@ describe("<SidebarNav> carries no rules for a viewport it never shows on", () =>
     // A touch screen at most 520 px tall gets the phone shell (the
     // `shell-mobile` variant), so the rail is hidden there and a class keyed
     // on that query can never apply.
-    const source = readFileSync(
-      join(__dirname, "..", "sidebar-nav.tsx"),
-      "utf8",
+    const source = readSource(
+      "src/components/layout/sidebar-nav.tsx",
+      "export function SidebarNav",
     );
     expect(source).not.toMatch(/pointer:coarse\)_and_\(height<=520px\)/);
   });
diff --git a/src/components/onboarding/__tests__/confirm-failure-recovery.test.ts b/src/components/onboarding/__tests__/confirm-failure-recovery.test.ts
index 2df83c41e..dc1e036b7 100644
--- a/src/components/onboarding/__tests__/confirm-failure-recovery.test.ts
+++ b/src/components/onboarding/__tests__/confirm-failure-recovery.test.ts
@@ -16,8 +16,6 @@
  * component tests render server-side and cannot click.
  */
 import { describe, expect, it, vi } from "vitest";
-import { readFileSync } from "node:fs";
-import { join } from "node:path";
 
 import {
   defaultOnboardingSteps,
@@ -27,6 +25,7 @@ import {
 
 import { runBaselineAttempt } from "../baseline-form";
 import { runConfirmFinish } from "../confirm-screen";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 type PassableStep = Parameters<
   Parameters<typeof runConfirmFinish>[0]["passStep"]
@@ -92,10 +91,10 @@ describe("runBaselineAttempt", () => {
   it("is the form's only way to move the pending flag", () => {
     // A second, inline `setSaving(false)` is how the flag stopped being
     // reset on one of the three exits in the first place.
-    const source = readFileSync(
-      join(process.cwd(), "src/components/onboarding/baseline-form.tsx"),
-      "utf8",
-    );
+    const source = readSource("src/components/onboarding/baseline-form.tsx", [
+      "export function BaselineForm",
+      "setSaving",
+    ]);
     expect(source).not.toContain("setSaving(false)");
     expect(source).not.toContain("setSaving(true)");
   });
diff --git a/src/components/settings/__tests__/anamnesis-about-me-relocation.test.tsx b/src/components/settings/__tests__/anamnesis-about-me-relocation.test.tsx
index 0383d285b..4eedaf5cb 100644
--- a/src/components/settings/__tests__/anamnesis-about-me-relocation.test.tsx
+++ b/src/components/settings/__tests__/anamnesis-about-me-relocation.test.tsx
@@ -1,11 +1,10 @@
 import type React from "react";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
-import { readFileSync } from "node:fs";
-import { join } from "node:path";
 
 import { I18nProvider } from "@/lib/i18n/context";
 import { AnamnesisSection } from "../anamnesis-section";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 /**
  * #159 — the "About me" note and the free-text allergies line moved from the
@@ -144,9 +143,9 @@ describe("Anamnese — the About-me note card (#159)", () => {
 
 describe("Account settings — the About-me card is gone (#159)", () => {
   it("the account section carries no about-me mount any more", () => {
-    const source = readFileSync(
-      join(process.cwd(), "src/components/settings/account-section/index.tsx"),
-      "utf8",
+    const source = readSource(
+      "src/components/settings/account-section/index.tsx",
+      "export function AccountSection",
     );
     expect(source).not.toContain("AboutMeSection");
     expect(source).not.toContain("about-me-section");
diff --git a/src/components/settings/__tests__/password-card-placement.test.tsx b/src/components/settings/__tests__/password-card-placement.test.tsx
index 57618e9ff..d902a055a 100644
--- a/src/components/settings/__tests__/password-card-placement.test.tsx
+++ b/src/components/settings/__tests__/password-card-placement.test.tsx
@@ -41,6 +41,7 @@ vi.mock("@/hooks/use-auth", () => ({
 
 import { PasswordCard } from "../password-card";
 import { SecuritySection } from "../security-section";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 const SLOT = 'data-slot="settings-password-card"';
 
@@ -108,9 +109,9 @@ describe("change-password card placement", () => {
   });
 
   it("left no password form behind in the Account section", () => {
-    const account = readFileSync(
-      join(ROOT, "src/components/settings/account-section/index.tsx"),
-      "utf8",
+    const account = readSource(
+      "src/components/settings/account-section/index.tsx",
+      "export function AccountSection",
     );
     for (const marker of [
       "settings.passwordTitle",
diff --git a/src/lib/jobs/reminder/__tests__/integration-cohort-outcomes.test.ts b/src/lib/jobs/reminder/__tests__/integration-cohort-outcomes.test.ts
index 644c43133..1916b6511 100644
--- a/src/lib/jobs/reminder/__tests__/integration-cohort-outcomes.test.ts
+++ b/src/lib/jobs/reminder/__tests__/integration-cohort-outcomes.test.ts
@@ -1,6 +1,7 @@
 import { readFileSync } from "node:fs";
 import { join } from "node:path";
 import { describe, expect, it, vi } from "vitest";
+import { readSource } from "@/__tests__/helpers/source-files";
 
 type Provider = "google_health" | "withings";
 type UserStatus = "complete" | "partial" | "failed" | "parked" | "skipped";
@@ -45,9 +46,9 @@ const googleHandlerSource = readFileSync(
   join(process.cwd(), "src/lib/jobs/reminder/google-health-sync.ts"),
   "utf8",
 );
-const googleSyncSource = readFileSync(
-  join(process.cwd(), "src/lib/google-health/sync.ts"),
-  "utf8",
+const googleSyncSource = readSource(
+  "src/lib/google-health/sync.ts",
+  "export async function syncUserGoogleHealth(",
 );
 const withingsHandlerSource = readFileSync(
   join(process.cwd(), "src/lib/jobs/reminder/withings-sync.ts"),