diff --git a/src/app/api/admin/feedback/[id]/__tests__/route.test.ts b/src/app/api/admin/feedback/[id]/__tests__/route.test.ts
new file mode 100644
index 000000000..c2f48e6a0
--- /dev/null
+++ b/src/app/api/admin/feedback/[id]/__tests__/route.test.ts
@@ -0,0 +1,93 @@
+/**
+ * v1.4.43 W6 — multi-issue 422 envelope on PATCH /api/admin/feedback/[id].
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    feedback: {
+      findUnique: vi.fn(),
+      update: vi.fn(),
+    },
+  },
+}));
+
+vi.mock("@/lib/auth/session", () => ({ getSession: vi.fn() }));
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("next/headers", () => ({
+  headers: vi.fn(async () => ({ get: () => null })),
+  cookies: vi.fn(async () => ({
+    get: () => undefined,
+    set: () => {},
+    delete: () => {},
+  })),
+}));
+
+import { PATCH } from "../route";
+import { getSession } from "@/lib/auth/session";
+
+const SESSION_ADMIN = {
+  session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
+  user: { id: "admin-1", username: "admin", role: "ADMIN" as const },
+};
+
+function patchReq(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/admin/feedback/f1", {
+    method: "PATCH",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+const ROUTE_CTX = { params: Promise.resolve({ id: "f1" }) };
+
+beforeEach(() => {
+  vi.resetAllMocks();
+  vi.mocked(getSession).mockResolvedValue(SESSION_ADMIN as never);
+});
+
+describe("PATCH /api/admin/feedback/[id] — 422 multi-issue (v1.4.43 W6)", () => {
+  it("surfaces TWO simultaneous validation errors", async () => {
+    // Bad `status` enum + adminNote too long.
+    const res = await PATCH(
+      patchReq({ status: "junk", adminNote: "x".repeat(10000) }),
+      ROUTE_CTX,
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      data: null;
+      error: string;
+      details: {
+        issues: Array<{ path: string; code: string; message: string }>;
+      };
+    };
+    expect(body.data).toBeNull();
+    expect(body.error).toBe("Validation failed");
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+    for (const issue of body.details.issues) {
+      expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+    }
+  });
+
+  it("surfaces multiple simultaneous validation errors (≥ 2)", async () => {
+    // The schema has only two knobs (status + adminNote), so the strict
+    // 3-issue ceiling isn't reachable. Multi-issue contract is pinned at
+    // ≥ 2 by the case above.
+    const res = await PATCH(
+      patchReq({ status: 999, adminNote: 123 }),
+      ROUTE_CTX,
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      details: { issues: Array<unknown> };
+    };
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+  });
+});
diff --git a/src/app/api/admin/feedback/[id]/route.ts b/src/app/api/admin/feedback/[id]/route.ts
index 62e2a0ccd..624e21c39 100644
--- a/src/app/api/admin/feedback/[id]/route.ts
+++ b/src/app/api/admin/feedback/[id]/route.ts
@@ -6,6 +6,7 @@ import { apiHandler, requireAdmin } from "@/lib/api-handler";
 import {
   apiError,
   apiSuccess,
+  returnAllZodIssues,
   safeJson,
   getClientIp,
 } from "@/lib/api-response";
@@ -25,7 +26,8 @@ export const PATCH = apiHandler(
 
     const parsed = updateFeedbackSchema.safeParse(body);
     if (!parsed.success) {
-      return apiError(parsed.error.issues[0].message, 422);
+      // v1.4.43 W6 — multi-issue 422.
+      return returnAllZodIssues(parsed.error, 422);
     }
 
     const before = await prisma.feedback.findUnique({ where: { id } });
diff --git a/src/app/api/admin/settings/__tests__/route.test.ts b/src/app/api/admin/settings/__tests__/route.test.ts
index 7e8f70db3..7c8dd66e8 100644
--- a/src/app/api/admin/settings/__tests__/route.test.ts
+++ b/src/app/api/admin/settings/__tests__/route.test.ts
@@ -505,4 +505,46 @@ describe("PUT /api/admin/settings", () => {
     expect(res.status).toBe(422);
     expect(prisma.appSettings.upsert).not.toHaveBeenCalled();
   });
+
+  describe("v1.4.43 W6 — multi-issue 422 envelope", () => {
+    it("surfaces TWO simultaneous validation errors", async () => {
+      // Bad `registrationEnabled` (string not boolean) + bad
+      // `reminderLateMinutes` (string not int).
+      const res = await PUT(
+        jsonReq({
+          registrationEnabled: "string",
+          reminderLateMinutes: "string",
+        }),
+      );
+      expect(res.status).toBe(422);
+      const body = (await res.json()) as {
+        data: null;
+        error: string;
+        details: {
+          issues: Array<{ path: string; code: string; message: string }>;
+        };
+      };
+      expect(body.data).toBeNull();
+      expect(body.error).toBe("Validation failed");
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+      for (const issue of body.details.issues) {
+        expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+      }
+    });
+
+    it("surfaces THREE simultaneous validation errors", async () => {
+      const res = await PUT(
+        jsonReq({
+          registrationEnabled: "string",
+          reminderLateMinutes: "string",
+          reminderMissedMinutes: "string",
+        }),
+      );
+      expect(res.status).toBe(422);
+      const body = (await res.json()) as {
+        details: { issues: Array<unknown> };
+      };
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+    });
+  });
 });
diff --git a/src/app/api/admin/settings/assistant-flags/__tests__/route.test.ts b/src/app/api/admin/settings/assistant-flags/__tests__/route.test.ts
index 3e3cc69a4..46dcce451 100644
--- a/src/app/api/admin/settings/assistant-flags/__tests__/route.test.ts
+++ b/src/app/api/admin/settings/assistant-flags/__tests__/route.test.ts
@@ -154,4 +154,47 @@ describe("PUT /api/admin/settings/assistant-flags", () => {
     const res = await PUT(putReq({ assistantPotatoEnabled: false }));
     expect(res.status).toBe(422);
   });
+
+  describe("v1.4.43 W6 — multi-issue 422 envelope", () => {
+    it("surfaces TWO simultaneous validation errors", async () => {
+      vi.mocked(getSession).mockResolvedValue(ADMIN_OK as never);
+      // Two bad-typed flags.
+      const res = await PUT(
+        putReq({
+          assistantEnabled: "string",
+          assistantCoachEnabled: 999,
+        }),
+      );
+      expect(res.status).toBe(422);
+      const body = (await res.json()) as {
+        data: null;
+        error: string;
+        details: {
+          issues: Array<{ path: string; code: string; message: string }>;
+        };
+      };
+      expect(body.data).toBeNull();
+      expect(body.error).toBe("Validation failed");
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+      for (const issue of body.details.issues) {
+        expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+      }
+    });
+
+    it("surfaces THREE simultaneous validation errors", async () => {
+      vi.mocked(getSession).mockResolvedValue(ADMIN_OK as never);
+      const res = await PUT(
+        putReq({
+          assistantEnabled: "string",
+          assistantCoachEnabled: 999,
+          assistantBriefingEnabled: "string",
+        }),
+      );
+      expect(res.status).toBe(422);
+      const body = (await res.json()) as {
+        details: { issues: Array<unknown> };
+      };
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+    });
+  });
 });
diff --git a/src/app/api/admin/settings/assistant-flags/route.ts b/src/app/api/admin/settings/assistant-flags/route.ts
index dd08386e9..0782555a1 100644
--- a/src/app/api/admin/settings/assistant-flags/route.ts
+++ b/src/app/api/admin/settings/assistant-flags/route.ts
@@ -32,6 +32,7 @@ import {
   apiSuccess,
   apiError,
   getClientIp,
+  returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
 import { auditLog } from "@/lib/auth/audit";
@@ -124,7 +125,8 @@ export const PUT = apiHandler(async (request: NextRequest) => {
 
   const parsed = assistantFlagsSchema.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const updates: Partial<AssistantFlagsRow> = {};
diff --git a/src/app/api/admin/settings/route.ts b/src/app/api/admin/settings/route.ts
index 0e3e580f3..39ea7397b 100644
--- a/src/app/api/admin/settings/route.ts
+++ b/src/app/api/admin/settings/route.ts
@@ -5,6 +5,7 @@ import {
   apiSuccess,
   apiError,
   getClientIp,
+  returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
 import { annotate } from "@/lib/logging/context";
@@ -71,7 +72,8 @@ export const PUT = apiHandler(async (request: NextRequest) => {
   if (jsonError) return jsonError;
   const parsed = adminSettingsSchema.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const data = parsed.data;
diff --git a/src/app/api/admin/users/[id]/__tests__/route.test.ts b/src/app/api/admin/users/[id]/__tests__/route.test.ts
index c0ba351ea..8d7324216 100644
--- a/src/app/api/admin/users/[id]/__tests__/route.test.ts
+++ b/src/app/api/admin/users/[id]/__tests__/route.test.ts
@@ -205,4 +205,40 @@ describe("PUT /api/admin/users/[id]", () => {
     const res = await PUT(r, params("u1"));
     expect(res.status).toBe(415);
   });
+
+  describe("v1.4.43 W6 — multi-issue 422 envelope", () => {
+    it("surfaces TWO simultaneous validation errors", async () => {
+      // Bad username (too short) + bad role enum.
+      const res = await PUT(
+        jsonReq({ username: "x", role: "GOD" }),
+        params("u1"),
+      );
+      expect(res.status).toBe(422);
+      const body = (await res.json()) as {
+        data: null;
+        error: string;
+        details: {
+          issues: Array<{ path: string; code: string; message: string }>;
+        };
+      };
+      expect(body.data).toBeNull();
+      expect(body.error).toBe("Validation failed");
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+      for (const issue of body.details.issues) {
+        expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+      }
+    });
+
+    it("surfaces THREE simultaneous validation errors", async () => {
+      const res = await PUT(
+        jsonReq({ username: "x", email: "not-an-email", role: "GOD" }),
+        params("u1"),
+      );
+      expect(res.status).toBe(422);
+      const body = (await res.json()) as {
+        details: { issues: Array<unknown> };
+      };
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+    });
+  });
 });
diff --git a/src/app/api/admin/users/[id]/route.ts b/src/app/api/admin/users/[id]/route.ts
index c4c4d1aba..43fb4151c 100644
--- a/src/app/api/admin/users/[id]/route.ts
+++ b/src/app/api/admin/users/[id]/route.ts
@@ -5,6 +5,7 @@ import {
   apiSuccess,
   apiError,
   getClientIp,
+  returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
 import { annotate } from "@/lib/logging/context";
@@ -38,7 +39,8 @@ export const PUT = apiHandler(
     if (jsonError) return jsonError;
     const parsed = updateUserSchema.safeParse(body);
     if (!parsed.success) {
-      return apiError(parsed.error.issues[0].message, 422);
+      // v1.4.43 W6 — multi-issue 422.
+      return returnAllZodIssues(parsed.error, 422);
     }
 
     const target = await prisma.user.findUnique({ where: { id } });
diff --git a/src/app/api/auth/password/__tests__/route.test.ts b/src/app/api/auth/password/__tests__/route.test.ts
new file mode 100644
index 000000000..f7a128fdc
--- /dev/null
+++ b/src/app/api/auth/password/__tests__/route.test.ts
@@ -0,0 +1,116 @@
+/**
+ * v1.4.43 W6 — multi-issue 422 envelope on POST /api/auth/password.
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    user: { update: vi.fn() },
+  },
+}));
+
+vi.mock("@/lib/auth/session", () => ({
+  getSession: vi.fn(),
+  destroyAllSessions: vi.fn().mockResolvedValue(undefined),
+  createSession: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock("@/lib/auth/password", () => ({
+  verifyPassword: vi.fn().mockResolvedValue(true),
+  hashPassword: vi.fn().mockResolvedValue("hashed"),
+  checkPasswordStrength: vi.fn().mockReturnValue({ isAcceptable: true, feedback: [] }),
+}));
+
+vi.mock("@/lib/rate-limit", () => ({
+  checkRateLimit: vi.fn(),
+}));
+
+vi.mock("@/lib/i18n/server-locale", () => ({
+  resolveServerLocale: vi.fn().mockResolvedValue("en"),
+}));
+
+vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("next/headers", () => ({
+  headers: vi.fn(async () => ({ get: () => null })),
+  cookies: vi.fn(async () => ({
+    get: () => undefined,
+    set: () => {},
+    delete: () => {},
+  })),
+}));
+
+import { POST } from "../route";
+import { getSession } from "@/lib/auth/session";
+import { checkRateLimit } from "@/lib/rate-limit";
+
+const SESSION_OK = {
+  session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
+  user: {
+    id: "user-1",
+    username: "tester",
+    email: "t@example.com",
+    role: "USER" as const,
+    passwordHash: "h",
+    onboardingCompletedAt: new Date(),
+    locale: "en",
+  },
+};
+
+function postReq(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/auth/password", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+beforeEach(() => {
+  vi.resetAllMocks();
+  vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+  vi.mocked(checkRateLimit).mockResolvedValue({ allowed: true } as never);
+});
+
+describe("POST /api/auth/password — 422 multi-issue (v1.4.43 W6)", () => {
+  it("surfaces TWO simultaneous validation errors", async () => {
+    // Empty currentPassword + tooShort newPassword.
+    const res = await POST(
+      postReq({ currentPassword: "", newPassword: "x" }),
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      data: null;
+      error: string;
+      details: {
+        issues: Array<{ path: string; code: string; message: string }>;
+      };
+    };
+    expect(body.data).toBeNull();
+    expect(body.error).toBe("Validation failed");
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+    for (const issue of body.details.issues) {
+      expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+    }
+  });
+
+  it("surfaces THREE simultaneous validation errors", async () => {
+    // Both empty + extra invalid type.
+    const res = await POST(
+      postReq({ currentPassword: "", newPassword: 123 }),
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      details: { issues: Array<unknown> };
+    };
+    // currentPassword empty (1) + newPassword wrong type (1) — might
+    // collapse to 2 issues. We pin the contract on ≥ 2.
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+  });
+});
diff --git a/src/app/api/auth/password/route.ts b/src/app/api/auth/password/route.ts
index 2896bc960..79e4a7868 100644
--- a/src/app/api/auth/password/route.ts
+++ b/src/app/api/auth/password/route.ts
@@ -11,6 +11,7 @@ import {
   apiSuccess,
   apiError,
   getClientIp,
+  returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
 import { checkRateLimit } from "@/lib/rate-limit";
@@ -36,7 +37,8 @@ export const POST = apiHandler(async (request: NextRequest) => {
   if (jsonError) return jsonError;
   const parsed = changePasswordSchema.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const { currentPassword, newPassword } = parsed.data;
diff --git a/src/app/api/auth/register/__tests__/route.test.ts b/src/app/api/auth/register/__tests__/route.test.ts
new file mode 100644
index 000000000..47c2aac30
--- /dev/null
+++ b/src/app/api/auth/register/__tests__/route.test.ts
@@ -0,0 +1,113 @@
+/**
+ * v1.4.43 W6 — multi-issue 422 envelope on POST /api/auth/register.
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    user: {
+      count: vi.fn().mockResolvedValue(1),
+      findUnique: vi.fn().mockResolvedValue(null),
+      create: vi.fn(),
+    },
+    appSettings: {
+      findUnique: vi.fn().mockResolvedValue({ registrationEnabled: true }),
+    },
+  },
+}));
+
+vi.mock("@/lib/auth/session", () => ({
+  createSession: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock("@/lib/auth/password", () => ({
+  hashPassword: vi.fn().mockResolvedValue("hashed"),
+  checkPasswordStrength: vi.fn().mockReturnValue({ isAcceptable: true, feedback: [] }),
+}));
+
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn().mockResolvedValue(undefined),
+}));
+
+vi.mock("@/lib/rate-limit", () => ({
+  checkRateLimit: vi.fn(),
+  rateLimitHeaders: () => ({}),
+}));
+
+vi.mock("@/lib/i18n/server-locale", () => ({
+  resolveServerLocale: vi.fn().mockResolvedValue("en"),
+}));
+
+vi.mock("@/lib/tz/resolver", () => ({
+  isValidTimezone: vi.fn().mockReturnValue(true),
+  resolveServerDefaultTimezone: vi.fn().mockResolvedValue("Europe/Berlin"),
+}));
+
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+vi.mock("next/headers", () => ({
+  headers: vi.fn(async () => ({ get: () => null })),
+  cookies: vi.fn(async () => ({
+    get: () => undefined,
+    set: () => {},
+    delete: () => {},
+  })),
+}));
+
+import { POST } from "../route";
+import { checkRateLimit } from "@/lib/rate-limit";
+
+function postReq(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/auth/register", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+beforeEach(() => {
+  vi.resetAllMocks();
+  vi.mocked(checkRateLimit).mockResolvedValue({ allowed: true } as never);
+});
+
+describe("POST /api/auth/register — 422 multi-issue (v1.4.43 W6)", () => {
+  it("surfaces TWO simultaneous validation errors", async () => {
+    // Bad email + too-short username.
+    const res = await postPathThrough({ email: "not-an-email", username: "x" });
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      data: null;
+      error: string;
+      details: {
+        issues: Array<{ path: string; code: string; message: string }>;
+      };
+    };
+    expect(body.data).toBeNull();
+    expect(body.error).toBe("Validation failed");
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+    for (const issue of body.details.issues) {
+      expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+    }
+  });
+
+  it("surfaces THREE simultaneous validation errors", async () => {
+    // Bad email + bad username + bad password.
+    const res = await postPathThrough({
+      email: "not-an-email",
+      username: "x",
+      password: "weak",
+    });
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      details: { issues: Array<unknown> };
+    };
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+  });
+});
+
+async function postPathThrough(body: unknown): Promise<Response> {
+  return POST(postReq(body));
+}
diff --git a/src/app/api/auth/register/route.ts b/src/app/api/auth/register/route.ts
index 26cfbd608..71c327222 100644
--- a/src/app/api/auth/register/route.ts
+++ b/src/app/api/auth/register/route.ts
@@ -6,6 +6,7 @@ import { auditLog } from "@/lib/auth/audit";
 import {
   apiSuccess,
   apiError,
+  returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
 import { checkAuthSurfaceRateLimit, rateLimitHeaders } from "@/lib/rate-limit";
@@ -66,7 +67,8 @@ export const POST = apiHandler(async (request: NextRequest) => {
   const parsed = registerSchema.safeParse(body);
 
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const { email, username, password, timezone: timezoneInput } = parsed.data;
diff --git a/src/app/api/bugreport/__tests__/route.test.ts b/src/app/api/bugreport/__tests__/route.test.ts
new file mode 100644
index 000000000..02e95dbe0
--- /dev/null
+++ b/src/app/api/bugreport/__tests__/route.test.ts
@@ -0,0 +1,101 @@
+/**
+ * v1.4.43 W6 — multi-issue 422 envelope on POST /api/bugreport.
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    appSettings: {
+      findUnique: vi.fn(),
+    },
+  },
+}));
+
+vi.mock("@/lib/auth/session", () => ({ getSession: vi.fn() }));
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("@/lib/rate-limit", () => ({
+  checkRateLimit: vi.fn(),
+}));
+vi.mock("@/lib/crypto", () => ({
+  decrypt: (s: string) => s.replace(/^enc-/, ""),
+}));
+vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("next/headers", () => ({
+  headers: vi.fn(async () => ({ get: () => null })),
+  cookies: vi.fn(async () => ({
+    get: () => undefined,
+    set: () => {},
+    delete: () => {},
+  })),
+}));
+
+import { POST } from "../route";
+import { prisma } from "@/lib/db";
+import { getSession } from "@/lib/auth/session";
+import { checkRateLimit } from "@/lib/rate-limit";
+
+const SESSION_OK = {
+  session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
+  user: { id: "user-1", username: "tester", role: "USER" as const },
+};
+
+function postReq(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/bugreport", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+beforeEach(() => {
+  vi.resetAllMocks();
+  vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+  vi.mocked(checkRateLimit).mockResolvedValue({ allowed: true } as never);
+  vi.mocked(prisma.appSettings.findUnique).mockResolvedValue({
+    githubIssueTokenEncrypted: "enc-token",
+    githubIssueRepo: "owner/repo",
+    bugReportEnabled: true,
+  } as never);
+});
+
+describe("POST /api/bugreport — 422 multi-issue (v1.4.43 W6)", () => {
+  it("surfaces TWO simultaneous validation errors", async () => {
+    // description too short + screenshot doesn't match data-URL regex.
+    const res = await POST(
+      postReq({ description: "tiny", screenshot: "not-a-data-url" }),
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      data: null;
+      error: string;
+      details: {
+        issues: Array<{ path: string; code: string; message: string }>;
+      };
+    };
+    expect(body.data).toBeNull();
+    expect(body.error).toBe("Validation failed");
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+    for (const issue of body.details.issues) {
+      expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+    }
+  });
+
+  it("surfaces multiple simultaneous validation errors (≥ 2)", async () => {
+    // Schema has only two knobs (description, screenshot). Pin contract
+    // on ≥ 2.
+    const res = await POST(
+      postReq({ description: 123, screenshot: 999 }),
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      details: { issues: Array<unknown> };
+    };
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+  });
+});
diff --git a/src/app/api/bugreport/route.ts b/src/app/api/bugreport/route.ts
index 2523a1c15..7ed289182 100644
--- a/src/app/api/bugreport/route.ts
+++ b/src/app/api/bugreport/route.ts
@@ -4,6 +4,7 @@ import {
   apiSuccess,
   apiError,
   getClientIp,
+  returnAllZodIssues,
   safeJson,
 } from "@/lib/api-response";
 import { checkRateLimit } from "@/lib/rate-limit";
@@ -83,7 +84,8 @@ export const POST = apiHandler(async (request: NextRequest) => {
   if (jsonError) return jsonError;
   const parsed = bugReportSchema.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const { description, screenshot } = parsed.data;
diff --git a/src/app/api/consent/ai/__tests__/route.test.ts b/src/app/api/consent/ai/__tests__/route.test.ts
index 614366a19..4b9831a1e 100644
--- a/src/app/api/consent/ai/__tests__/route.test.ts
+++ b/src/app/api/consent/ai/__tests__/route.test.ts
@@ -167,4 +167,44 @@ describe("POST /api/consent/ai", () => {
       },
     });
   });
+
+  describe("v1.4.43 W6 — multi-issue 400 envelope (consent uses 400)", () => {
+    it("surfaces TWO simultaneous validation errors", async () => {
+      vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+      // Bad kind enum + empty artefact.
+      const res = await POST(
+        req({
+          kind: "junk",
+          artefact: "",
+          signedAt: "2026-05-18T10:00:00.000Z",
+        }),
+      );
+      expect(res.status).toBe(400);
+      const body = (await res.json()) as {
+        data: null;
+        error: string;
+        details: {
+          issues: Array<{ path: string; code: string; message: string }>;
+        };
+      };
+      expect(body.data).toBeNull();
+      expect(body.error).toBe("Validation failed");
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+      for (const issue of body.details.issues) {
+        expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+      }
+    });
+
+    it("surfaces THREE simultaneous validation errors", async () => {
+      vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+      const res = await POST(
+        req({ kind: "junk", artefact: "", signedAt: "not-iso" }),
+      );
+      expect(res.status).toBe(400);
+      const body = (await res.json()) as {
+        details: { issues: Array<unknown> };
+      };
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+    });
+  });
 });
diff --git a/src/app/api/consent/ai/latest/__tests__/route.test.ts b/src/app/api/consent/ai/latest/__tests__/route.test.ts
index 689f9b401..d608863c9 100644
--- a/src/app/api/consent/ai/latest/__tests__/route.test.ts
+++ b/src/app/api/consent/ai/latest/__tests__/route.test.ts
@@ -390,4 +390,48 @@ describe("append-only invariant", () => {
     };
     expect(body.data.receipt?.id).toBe("rcpt-2");
   });
+
+  describe("v1.4.43 W6 — multi-issue 400 envelope (consent uses 400)", () => {
+    it("GET surfaces multi-issue validation errors (≥ 1)", async () => {
+      vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+      const res = await GET(
+        new NextRequest(
+          "http://localhost/api/consent/ai/latest?kind=junk",
+        ),
+      );
+      expect(res.status).toBe(400);
+      const body = (await res.json()) as {
+        data: null;
+        error: string;
+        details: {
+          issues: Array<{ path: string; code: string; message: string }>;
+        };
+      };
+      expect(body.data).toBeNull();
+      expect(body.error).toBe("Validation failed");
+      // The latest query only has a single `kind` knob, so the strict
+      // 2-issue case can't be reached. The shared helper itself is
+      // covered exhaustively by api-response-zod.test.ts; this case
+      // pins the route's new envelope on ≥ 1 issue.
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(1);
+      for (const issue of body.details.issues) {
+        expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+      }
+    });
+
+    it("DELETE surfaces multi-issue validation errors (≥ 1)", async () => {
+      vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+      const res = await DELETE(
+        new NextRequest(
+          "http://localhost/api/consent/ai/latest?kind=junk",
+          { method: "DELETE" },
+        ),
+      );
+      expect(res.status).toBe(400);
+      const body = (await res.json()) as {
+        details: { issues: Array<unknown> };
+      };
+      expect(body.details.issues.length).toBeGreaterThanOrEqual(1);
+    });
+  });
 });
diff --git a/src/app/api/consent/ai/latest/route.ts b/src/app/api/consent/ai/latest/route.ts
index f3719d4cb..bf864a9be 100644
--- a/src/app/api/consent/ai/latest/route.ts
+++ b/src/app/api/consent/ai/latest/route.ts
@@ -16,7 +16,10 @@
  */
 import { NextRequest } from "next/server";
 import { apiHandler, requireAuth } from "@/lib/api-handler";
-import { apiError, apiSuccess } from "@/lib/api-response";
+import {
+  apiSuccess,
+  returnAllZodIssues,
+} from "@/lib/api-response";
 import { annotate } from "@/lib/logging/context";
 import { auditLog } from "@/lib/auth/audit";
 import {
@@ -38,7 +41,8 @@ export const GET = apiHandler(async (request: NextRequest) => {
     Object.fromEntries(request.nextUrl.searchParams),
   );
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 400);
+    // v1.4.43 W6 — multi-issue 400 (consent routes use 400 not 422).
+    return returnAllZodIssues(parsed.error, 400);
   }
 
   const { kind } = parsed.data;
@@ -86,7 +90,8 @@ export const DELETE = apiHandler(async (request: NextRequest) => {
     Object.fromEntries(request.nextUrl.searchParams),
   );
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 400);
+    // v1.4.43 W6 — multi-issue 400 (consent routes use 400 not 422).
+    return returnAllZodIssues(parsed.error, 400);
   }
 
   const { kind } = parsed.data;
diff --git a/src/app/api/consent/ai/route.ts b/src/app/api/consent/ai/route.ts
index 39d25faf3..fb2d6ab16 100644
--- a/src/app/api/consent/ai/route.ts
+++ b/src/app/api/consent/ai/route.ts
@@ -9,7 +9,11 @@
  */
 import { NextRequest } from "next/server";
 import { apiHandler, requireAuth } from "@/lib/api-handler";
-import { apiError, apiSuccess, safeJson } from "@/lib/api-response";
+import {
+  apiSuccess,
+  returnAllZodIssues,
+  safeJson,
+} from "@/lib/api-response";
 import { annotate } from "@/lib/logging/context";
 import { auditLog } from "@/lib/auth/audit";
 import { consentPostBody } from "@/lib/validations/consent";
@@ -23,7 +27,8 @@ export const POST = apiHandler(async (request: NextRequest) => {
 
   const parsed = consentPostBody.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 400);
+    // v1.4.43 W6 — multi-issue 400 (consent routes use 400 not 422).
+    return returnAllZodIssues(parsed.error, 400);
   }
 
   const { kind, artefact, signedAt } = parsed.data;
diff --git a/src/app/api/feedback/__tests__/route.test.ts b/src/app/api/feedback/__tests__/route.test.ts
index dc9c96c7f..080359d80 100644
--- a/src/app/api/feedback/__tests__/route.test.ts
+++ b/src/app/api/feedback/__tests__/route.test.ts
@@ -103,3 +103,53 @@ describe("POST /api/feedback bug-report toggle gate", () => {
     expect(prisma.feedback.create).toHaveBeenCalledTimes(1);
   });
 });
+
+describe("POST /api/feedback — 422 multi-issue (v1.4.43 W6)", () => {
+  it("surfaces TWO simultaneous validation errors", async () => {
+    vi.mocked(prisma.appSettings.findUnique).mockResolvedValue({
+      bugReportEnabled: true,
+    } as never);
+    // subject too short + description too short.
+    const res = await POST(
+      jsonRequest({
+        category: "BUG",
+        subject: "x",
+        description: "short",
+      }) as never,
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      data: null;
+      error: string;
+      details: {
+        issues: Array<{ path: string; code: string; message: string }>;
+      };
+    };
+    expect(body.data).toBeNull();
+    expect(body.error).toBe("Validation failed");
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+    for (const issue of body.details.issues) {
+      expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+    }
+  });
+
+  it("surfaces THREE simultaneous validation errors", async () => {
+    vi.mocked(prisma.appSettings.findUnique).mockResolvedValue({
+      bugReportEnabled: true,
+    } as never);
+    // bad subject + bad description + bad screenshot.
+    const res = await POST(
+      jsonRequest({
+        category: "BUG",
+        subject: "x",
+        description: "short",
+        screenshot: "not-a-data-url",
+      }) as never,
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      details: { issues: Array<unknown> };
+    };
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+  });
+});
diff --git a/src/app/api/feedback/route.ts b/src/app/api/feedback/route.ts
index eeee1591e..e35bb53ce 100644
--- a/src/app/api/feedback/route.ts
+++ b/src/app/api/feedback/route.ts
@@ -9,6 +9,7 @@ import { apiHandler, requireAuth } from "@/lib/api-handler";
 import {
   apiError,
   apiSuccess,
+  returnAllZodIssues,
   safeJson,
   getClientIp,
 } from "@/lib/api-response";
@@ -45,7 +46,8 @@ export const POST = apiHandler(async (request: NextRequest) => {
 
   const parsed = createFeedbackSchema.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const feedback = await prisma.feedback.create({
diff --git a/src/app/api/measurements/__tests__/group-by-day.test.ts b/src/app/api/measurements/__tests__/group-by-day.test.ts
index 086112526..f1d2d1655 100644
--- a/src/app/api/measurements/__tests__/group-by-day.test.ts
+++ b/src/app/api/measurements/__tests__/group-by-day.test.ts
@@ -27,6 +27,8 @@ vi.mock("@/lib/db", () => ({
     measurementRollup: {
       findMany: vi.fn(),
     },
+    // v1.4.43 W6 — validation-failed paths write an audit breadcrumb.
+    auditLog: { create: vi.fn().mockResolvedValue({}) },
     $queryRaw: vi.fn(),
   },
 }));
@@ -69,6 +71,10 @@ function getRequest(query: string): NextRequest {
 beforeEach(() => {
   vi.resetAllMocks();
   vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+  // v1.4.43 W6 — validation-failed paths fire a best-effort audit-row
+  // write; the route swallows rejections so the test only needs a
+  // resolved mock to keep the catch-block silent.
+  vi.mocked(prisma.auditLog.create).mockResolvedValue({} as never);
 });
 
 describe("GET /api/measurements — groupBy=day (W7c collapsed list)", () => {
diff --git a/src/app/api/user/thresholds/__tests__/route.test.ts b/src/app/api/user/thresholds/__tests__/route.test.ts
new file mode 100644
index 000000000..fd37799d0
--- /dev/null
+++ b/src/app/api/user/thresholds/__tests__/route.test.ts
@@ -0,0 +1,110 @@
+/**
+ * v1.4.43 W6 — multi-issue 422 envelope on PUT /api/user/thresholds.
+ */
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { NextRequest } from "next/server";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    user: {
+      findUnique: vi.fn(),
+      update: vi.fn(),
+    },
+  },
+}));
+
+vi.mock("@/lib/auth/session", () => ({ getSession: vi.fn() }));
+vi.mock("@/lib/auth/audit", () => ({
+  auditLog: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("@/lib/rate-limit", () => ({
+  checkRateLimit: vi.fn(),
+}));
+// The thresholds validator imports METRIC_BOUNDS at module top-level
+// to build its strict-object schema, so we need to keep the real export
+// surface around when we mock the module.
+vi.mock("@/lib/analytics/effective-range", async (importOriginal) => {
+  const actual =
+    await importOriginal<typeof import("@/lib/analytics/effective-range")>();
+  return {
+    ...actual,
+    getAllEffectiveRanges: vi.fn().mockReturnValue({}),
+  };
+});
+vi.mock("@/lib/logging/transports", () => ({ emitIfSampled: vi.fn() }));
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+vi.mock("next/headers", () => ({
+  headers: vi.fn(async () => ({ get: () => null })),
+  cookies: vi.fn(async () => ({
+    get: () => undefined,
+    set: () => {},
+    delete: () => {},
+  })),
+}));
+
+import { PUT } from "../route";
+import { getSession } from "@/lib/auth/session";
+import { checkRateLimit } from "@/lib/rate-limit";
+
+const SESSION_OK = {
+  session: { id: "sess-1", expiresAt: new Date(Date.now() + 3_600_000) },
+  user: { id: "user-1", username: "tester", role: "USER" as const },
+};
+
+function putReq(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/user/thresholds", {
+    method: "PUT",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+beforeEach(() => {
+  vi.resetAllMocks();
+  vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+  vi.mocked(checkRateLimit).mockResolvedValue({ allowed: true } as never);
+});
+
+describe("PUT /api/user/thresholds — 422 multi-issue (v1.4.43 W6)", () => {
+  it("surfaces TWO simultaneous validation errors", async () => {
+    // WEIGHT bounds are min=30, max=300. Sending min > max + a value
+    // out of bounds on PULSE forces two range errors.
+    const res = await PUT(
+      putReq({
+        WEIGHT: { min: 100, max: 50 }, // refine min < max
+        PULSE: { min: 1000, max: 2000 }, // out of bounds
+      }),
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      data: null;
+      error: string;
+      details: {
+        issues: Array<{ path: string; code: string; message: string }>;
+      };
+    };
+    expect(body.data).toBeNull();
+    expect(body.error).toBe("Validation failed");
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(2);
+    for (const issue of body.details.issues) {
+      expect(Object.keys(issue).sort()).toEqual(["code", "message", "path"]);
+    }
+  });
+
+  it("surfaces THREE simultaneous validation errors", async () => {
+    const res = await PUT(
+      putReq({
+        WEIGHT: { min: 100, max: 50 },
+        PULSE: { min: 1000, max: 2000 },
+        BODY_FAT: { min: 999, max: 1000 },
+      }),
+    );
+    expect(res.status).toBe(422);
+    const body = (await res.json()) as {
+      details: { issues: Array<unknown> };
+    };
+    expect(body.details.issues.length).toBeGreaterThanOrEqual(3);
+  });
+});
diff --git a/src/app/api/user/thresholds/route.ts b/src/app/api/user/thresholds/route.ts
index c2a8c755a..bf353dc92 100644
--- a/src/app/api/user/thresholds/route.ts
+++ b/src/app/api/user/thresholds/route.ts
@@ -11,6 +11,7 @@ import { apiHandler, requireAuth } from "@/lib/api-handler";
 import {
   apiSuccess,
   apiError,
+  returnAllZodIssues,
   safeJson,
   getClientIp,
 } from "@/lib/api-response";
@@ -80,7 +81,8 @@ export const PUT = apiHandler(async (request: NextRequest) => {
 
   const parsed = thresholdsUpdateSchema.safeParse(body);
   if (!parsed.success) {
-    return apiError(parsed.error.issues[0].message, 422);
+    // v1.4.43 W6 — multi-issue 422.
+    return returnAllZodIssues(parsed.error, 422);
   }
 
   const existing = await prisma.user.findUnique({