diff --git a/src/app/api/admin/provider-health/__tests__/route.test.ts b/src/app/api/admin/provider-health/__tests__/route.test.ts
index 75fb1b373..bcc30b8ef 100644
--- a/src/app/api/admin/provider-health/__tests__/route.test.ts
+++ b/src/app/api/admin/provider-health/__tests__/route.test.ts
@@ -60,6 +60,14 @@ import { GET } from "../route";
 import { prisma } from "@/lib/db";
 import { requireAdmin } from "@/lib/api-handler";
 
+// Reset, not clear, before every case: cases replace the paused rows, the
+// settings row and the account groups, and a cleared mock would hand the
+// next case whatever the last one left there. A reset mock goes back to the
+// empty answer it was created with.
+beforeEach(() => {
+  vi.resetAllMocks();
+});
+
 const groupBy = vi.mocked(prisma.providerHealth.groupBy);
 const usageRows = vi.mocked(prisma.coachUsage.findMany);
 
@@ -101,7 +109,6 @@ function group(
 
 describe("GET /api/admin/provider-health", () => {
   beforeEach(() => {
-    vi.clearAllMocks();
     vi.mocked(requireAdmin).mockResolvedValue({
       user: { id: "admin1" },
     } as never);
@@ -302,7 +309,6 @@ describe("GET /api/admin/provider-health — pause and model check (v1.42)", ()
   const settings = vi.mocked(prisma.appSettings.findUnique);
 
   beforeEach(() => {
-    vi.clearAllMocks();
     vi.mocked(requireAdmin).mockResolvedValue({
       user: { id: "admin" },
     } as never);
diff --git a/src/app/api/coach/about-me/__tests__/route-concurrency.test.ts b/src/app/api/coach/about-me/__tests__/route-concurrency.test.ts
index c84a45162..249de579b 100644
--- a/src/app/api/coach/about-me/__tests__/route-concurrency.test.ts
+++ b/src/app/api/coach/about-me/__tests__/route-concurrency.test.ts
@@ -131,7 +131,10 @@ function putReq(
 }
 
 beforeEach(() => {
-  vi.clearAllMocks();
+  // Reset, not clear: cases replace the profile reads and the question store
+  // with their own implementations, and a cleared mock keeps them. A reset
+  // mock returns to the implementation it was created with.
+  vi.resetAllMocks();
   requireModuleEnabled.mockResolvedValue({ enabled: true });
 });
 
diff --git a/src/app/api/export/__tests__/soft-delete-filter.test.ts b/src/app/api/export/__tests__/soft-delete-filter.test.ts
index ef58cd010..50363cc58 100644
--- a/src/app/api/export/__tests__/soft-delete-filter.test.ts
+++ b/src/app/api/export/__tests__/soft-delete-filter.test.ts
@@ -174,6 +174,16 @@ beforeEach(() => {
   vi.mocked(isModuleEnabled).mockResolvedValue(true);
   vi.mocked(requireModuleEnabled).mockResolvedValue({ enabled: true } as never);
   vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+  // A session that signed in just now. Reset, not only cleared: a case below
+  // swaps in a stale session, and `clearAllMocks` keeps the implementation
+  // it left behind for whichever case runs next.
+  vi.mocked(prisma.session.findUnique)
+    .mockReset()
+    .mockImplementation((async () => ({
+      createdAt: new Date(),
+      mfaVerifiedAt: null,
+      reproofAt: null,
+    })) as never);
   vi.mocked(checkRateLimit).mockResolvedValue({
     allowed: true,
     limit: 60,
diff --git a/src/app/api/insights/chat/[id]/attachments/__tests__/route.test.ts b/src/app/api/insights/chat/[id]/attachments/__tests__/route.test.ts
index a715ba6c3..be0ab6d2e 100644
--- a/src/app/api/insights/chat/[id]/attachments/__tests__/route.test.ts
+++ b/src/app/api/insights/chat/[id]/attachments/__tests__/route.test.ts
@@ -87,6 +87,15 @@ beforeEach(() => {
   vi.clearAllMocks();
   vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
   vi.mocked(validateAttachmentCandidate).mockResolvedValue({ ok: true });
+  // Open again for every case: the detach case closes every capability, and
+  // `clearAllMocks` would carry that refusal into whichever case runs next.
+  vi.mocked(requireAiCapability)
+    .mockReset()
+    .mockResolvedValue({
+      available: true,
+      reason: null,
+      onDeviceAllowed: true,
+    } as never);
 });
 
 describe("POST attach", () => {
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 947964daa..8a7019860 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
@@ -276,7 +276,10 @@ function chatReq(body: Record<string, unknown>): Request {
 
 describe("coach chat — tool-mode routing (F1)", () => {
   beforeEach(() => {
-    vi.clearAllMocks();
+    // Reset, not clear: cases swap in their own tool loop and parsers, and a
+    // cleared mock would hand those to the next case. Every mock here goes
+    // back to the implementation it was created with.
+    vi.resetAllMocks();
     reserveBudget.mockResolvedValue({
       allowed: true,
       reserved: 3000,
diff --git a/src/components/dashboard/__tests__/dashboard-header.test.tsx b/src/components/dashboard/__tests__/dashboard-header.test.tsx
index 680ec64e8..6948538e8 100644
--- a/src/components/dashboard/__tests__/dashboard-header.test.tsx
+++ b/src/components/dashboard/__tests__/dashboard-header.test.tsx
@@ -52,6 +52,12 @@ import { primeLocales } from "@/__tests__/helpers/prime-locales";
 
 primeLocales("de");
 
+// Every case starts on an account that never set a module, whichever case
+// ran before it and left its own modules behind.
+beforeEach(() => {
+  modulesRef.value = undefined;
+});
+
 function renderSSR(node: React.ReactElement, locale: "en" | "de" = "de") {
   return renderToStaticMarkup(
     <I18nProvider initialLocale={locale}>{node}</I18nProvider>,
@@ -162,10 +168,6 @@ describe("<DashboardHeader> — quick-add menu", () => {
 });
 
 describe("<DashboardHeader> — Log workout", () => {
-  beforeEach(() => {
-    modulesRef.value = undefined;
-  });
-
   it("offers it beside the other capture entries", () => {
     modulesRef.value = { workouts: true };
     const html = renderSSR(
@@ -187,10 +189,6 @@ describe("<DashboardHeader> — Log workout", () => {
 });
 
 describe("<DashboardHeader> — every entry follows its module, as the capture picker does", () => {
-  beforeEach(() => {
-    modulesRef.value = undefined;
-  });
-
   it("withholds Log mood when the mood module is off", () => {
     modulesRef.value = { mood: false };
     const html = renderSSR(
diff --git a/src/components/illness/__tests__/use-illness-episodes-paging.test.ts b/src/components/illness/__tests__/use-illness-episodes-paging.test.ts
index e447bc115..79814a155 100644
--- a/src/components/illness/__tests__/use-illness-episodes-paging.test.ts
+++ b/src/components/illness/__tests__/use-illness-episodes-paging.test.ts
@@ -5,7 +5,7 @@
  * off the illness page, its settings and every picker once a record held more
  * than that, and they could then be found only through search.
  */
-import { describe, expect, it, vi } from "vitest";
+import { beforeEach, describe, expect, it, vi } from "vitest";
 
 const calls = vi.hoisted(() => [] as string[]);
 
@@ -41,6 +41,12 @@ vi.mock("@/lib/api/api-fetch", () => ({
 import { useIllnessEpisodes } from "../use-illness";
 
 describe("useIllnessEpisodes", () => {
+  // Each case states its own journal and counts only its own requests.
+  beforeEach(() => {
+    calls.length = 0;
+    journal.total = 230;
+  });
+
   it("reads page after page until the whole journal is in", async () => {
     const options = useIllnessEpisodes(true) as unknown as {
       queryFn: () => Promise<{ id: string }[]>;
@@ -55,7 +61,6 @@ describe("useIllnessEpisodes", () => {
   });
 
   it("stops on a full last page the route says is the end", async () => {
-    calls.length = 0;
     journal.total = 200;
     const options = useIllnessEpisodes(true) as unknown as {
       queryFn: () => Promise<{ id: string }[]>;
@@ -63,6 +68,5 @@ describe("useIllnessEpisodes", () => {
     expect(await options.queryFn()).toHaveLength(200);
     // Two full pages of 100, no third request for an empty one.
     expect(calls).toHaveLength(2);
-    journal.total = 230;
   });
 });
diff --git a/src/lib/insights/__tests__/usage-level-simulation.test.ts b/src/lib/insights/__tests__/usage-level-simulation.test.ts
index 1f51ab309..b09e8e657 100644
--- a/src/lib/insights/__tests__/usage-level-simulation.test.ts
+++ b/src/lib/insights/__tests__/usage-level-simulation.test.ts
@@ -129,9 +129,27 @@ function day(): Event[] {
   return events.sort((a, b) => a.at.localeCompare(b.at));
 }
 
-const ALL_SCOPES_AT_WARM = new Set<string>();
+/**
+ * Every scope the day dirties: run it once on `full` with no warm, which
+ * enqueues each scope at least once. Each case derives it itself rather than
+ * reading what an earlier case left behind.
+ */
+async function discoverWarmScopes(): Promise<Set<string>> {
+  sim.notes.clear();
+  sim.level = "FULL";
+  for (const event of day()) {
+    vi.setSystemTime(new Date(`2026-10-15T${event.at}:00Z`));
+    await invalidateStatusInsightsForTypes("u1", event.types, {
+      source: event.source,
+    });
+  }
+  return new Set(sim.notes.keys());
+}
 
-async function simulate(level: string | null): Promise<{
+async function simulate(
+  level: string | null,
+  warmScopes: ReadonlySet<string>,
+): Promise<{
   warm: number;
   ingest: number;
   bySource: Record<"sync" | "manual", number>;
@@ -141,8 +159,8 @@ async function simulate(level: string | null): Promise<{
   sim.level = level;
   // The 04:30 warm regenerates every scope the day will touch.
   const warmAt = Date.parse("2026-10-15T04:30:00Z");
-  for (const scope of ALL_SCOPES_AT_WARM) sim.notes.set(scope, warmAt);
-  const warm = ALL_SCOPES_AT_WARM.size;
+  for (const scope of warmScopes) sim.notes.set(scope, warmAt);
+  const warm = warmScopes.size;
   const bySource = { sync: 0, manual: 0 };
   for (const event of day()) {
     vi.setSystemTime(new Date(`2026-10-15T${event.at}:00Z`));
@@ -161,25 +179,14 @@ beforeEach(() => {
 
 describe("generations per day on a watch-synced account", () => {
   it("counts the scopes once to seed the warm", async () => {
-    // Discover every scope the day dirties: run it once on `full` with no
-    // warm, which enqueues each scope at least once.
-    ALL_SCOPES_AT_WARM.clear();
-    sim.notes.clear();
-    sim.level = "FULL";
-    for (const event of day()) {
-      vi.setSystemTime(new Date(`2026-10-15T${event.at}:00Z`));
-      await invalidateStatusInsightsForTypes("u1", event.types, {
-        source: event.source,
-      });
-    }
-    for (const scope of sim.notes.keys()) ALL_SCOPES_AT_WARM.add(scope);
-    expect(ALL_SCOPES_AT_WARM.size).toBe(19);
+    expect((await discoverWarmScopes()).size).toBe(19);
   });
 
   it("before v1.43 (every ingest at one hour) versus each level", async () => {
-    const full = await simulate("FULL"); // the behaviour before v1.43
-    const standard = await simulate("STANDARD");
-    const frugal = await simulate("FRUGAL");
+    const warmScopes = await discoverWarmScopes();
+    const full = await simulate("FULL", warmScopes); // the behaviour before v1.43
+    const standard = await simulate("STANDARD", warmScopes);
+    const frugal = await simulate("FRUGAL", warmScopes);
     const result = { full, standard, frugal };
     process.stdout.write(`SIMULATION ${JSON.stringify(result)}\n`);
 
diff --git a/src/lib/insights/derived/__tests__/derived-assessment-ai.test.ts b/src/lib/insights/derived/__tests__/derived-assessment-ai.test.ts
index 553b3c8bc..b1a6e3b3a 100644
--- a/src/lib/insights/derived/__tests__/derived-assessment-ai.test.ts
+++ b/src/lib/insights/derived/__tests__/derived-assessment-ai.test.ts
@@ -34,6 +34,7 @@ import {
   resolveReadOnlyStatusMiss,
 } from "@/lib/insights/status-cache";
 import { runStatusCompletion } from "@/lib/insights/status-provider";
+import { invalidateUserTimezone } from "@/lib/tz/resolver";
 import {
   resolveDerivedAssessment,
   generateDerivedScoreAssessment,
@@ -71,6 +72,9 @@ function okDerived(): Derived<unknown> {
 
 beforeEach(() => {
   vi.resetAllMocks();
+  // The zone resolver keeps a per-user cache for a minute; without this the
+  // first case to run fills it and every later one skips the read.
+  invalidateUserTimezone("u-ny");
   findUnique.mockResolvedValue({ timezone: "America/New_York" });
 });
 
diff --git a/src/lib/jobs/reminder/__tests__/backup-handlers.test.ts b/src/lib/jobs/reminder/__tests__/backup-handlers.test.ts
index 5f386a2d7..637a97952 100644
--- a/src/lib/jobs/reminder/__tests__/backup-handlers.test.ts
+++ b/src/lib/jobs/reminder/__tests__/backup-handlers.test.ts
@@ -248,6 +248,13 @@ describe("handleDataBackup on a large instance", () => {
   beforeEach(() => {
     vi.clearAllMocks();
     mocks.store.mockResolvedValue(undefined);
+    // Stated here rather than inherited: without a payload the pass stores
+    // nothing, and these cases used to pass only when another block's setup
+    // had run first and left its payload behind.
+    mocks.buildFullBackupPayload.mockResolvedValue({
+      payload: { schemaVersion: "1", userId: "user-dr" },
+      counts: {},
+    });
   });
 
   it("backs up the accounts with the oldest copies first and stops on the budget", async () => {
diff --git a/src/lib/withings/__tests__/sync-plausibility.test.ts b/src/lib/withings/__tests__/sync-plausibility.test.ts
index 60901ebb6..cc8bb6105 100644
--- a/src/lib/withings/__tests__/sync-plausibility.test.ts
+++ b/src/lib/withings/__tests__/sync-plausibility.test.ts
@@ -211,8 +211,10 @@ describe("syncUserMeasurements — plausibility gate", () => {
   it("does not overwrite a stored reading with an out-of-band one", async () => {
     // The slot already holds a real pulse; the provider re-sends the same
     // instant carrying a decode slip. Ungated, the update branch rewrote the
-    // good value with the bad one.
-    vi.mocked(prisma.measurement.findMany).mockResolvedValueOnce([
+    // good value with the bad one. Not `mockResolvedValueOnce`: the gate
+    // drops the reading before the stored rows are read, so a once-value
+    // would sit unconsumed and answer the next test's read instead.
+    vi.mocked(prisma.measurement.findMany).mockResolvedValue([
       {
         id: "existing-row",
         type: "PULSE",