diff --git a/src/lib/api-handler.ts b/src/lib/api-handler.ts
index 4733b9ac2..ba78ad92f 100644
--- a/src/lib/api-handler.ts
+++ b/src/lib/api-handler.ts
@@ -6,9 +6,8 @@ import { eventStorage, getEvent } from "./logging/context";
 import { emitIfSampled } from "./logging/transports";
 import { redactOptional, redactSecrets } from "./logging/redact";
 import { getSession } from "./auth/session";
-import { hashToken } from "./auth/hmac";
-import { prisma } from "./db";
 import { auditLog } from "./auth/audit";
+import { resolveBearerToken, BearerAuthError } from "./auth/bearer";
 import { AssistantDisabledError } from "./feature-flags";
 import { ConsentRequiredError } from "./ai/consent-guard";
 
@@ -291,110 +290,52 @@ export async function requireAuth(
 
 /**
  * Authenticate a raw Bearer token against `ApiToken`.
- * Annotates the Wide Event with `auth_method: "api_key"` and writes audit-log
- * entries for both success and failure.
+ *
+ * The validation itself lives in the transport-agnostic `resolveBearerToken`
+ * (`./auth/bearer`) — the single source of truth shared with the MCP wire. This
+ * wrapper adds the HTTP-edge concerns: the `auth.bearer.*` audit trail for both
+ * outcomes and the Wide-Event `auth_method: "bearer"` annotation, then maps the
+ * result onto the `AuthContext` contract (`session.id` carries the token id).
+ *
+ * Authorisation contract (unchanged): a route that declares no
+ * `requiredPermission` accepts any valid token; one that declares a scope
+ * accepts wildcard (`["*"]`) tokens and narrow-scope tokens that list it.
  */
 async function authenticateBearer(
   rawToken: string,
   requiredPermission: string | undefined,
 ): Promise<AuthContext> {
-  const tokenHashValue = hashToken(rawToken);
-
-  const apiToken = await prisma.apiToken.findUnique({
-    where: { tokenHash: tokenHashValue },
-    select: {
-      id: true,
-      userId: true,
-      permissions: true,
-      revoked: true,
-      expiresAt: true,
-    },
-  });
-
-  if (!apiToken) {
-    auditLog("auth.bearer.failure", {
-      details: { reason: "unknown_token" },
-    }).catch(() => {});
-    throw new HttpError(401, "Invalid token");
+  let resolution;
+  try {
+    resolution = await resolveBearerToken(rawToken, requiredPermission);
+  } catch (err) {
+    if (err instanceof BearerAuthError) {
+      auditLog("auth.bearer.failure", {
+        userId: err.userId ?? null,
+        details: {
+          reason: err.reason,
+          ...(err.tokenId ? { tokenId: err.tokenId } : {}),
+          ...(err.reason === "insufficient_permissions"
+            ? { required: requiredPermission }
+            : {}),
+        },
+      }).catch(() => {});
+      const message =
+        err.statusCode === 403
+          ? "Insufficient permissions"
+          : err.reason === "expired"
+            ? "Token expired"
+            : "Invalid token";
+      throw new HttpError(err.statusCode, message);
+    }
+    throw err;
   }
 
-  if (apiToken.revoked) {
-    auditLog("auth.bearer.failure", {
-      userId: apiToken.userId,
-      details: { reason: "revoked", tokenId: apiToken.id },
-    }).catch(() => {});
-    throw new HttpError(401, "Invalid token");
-  }
-
-  if (apiToken.expiresAt && apiToken.expiresAt <= new Date()) {
-    auditLog("auth.bearer.failure", {
-      userId: apiToken.userId,
-      details: { reason: "expired", tokenId: apiToken.id },
-    }).catch(() => {});
-    throw new HttpError(401, "Token expired");
-  }
-
-  // `["*"]` is the wildcard scope: granted to the iOS app on login so it
-  // can call any authenticated route. Narrow scopes (e.g.
-  // `["medication:ingest"]`) gate specific routes.
-  //
-  // Authorisation contract:
-  //   - Route declares no `requiredPermission`: any valid token passes
-  //     (both wildcard and narrow-scope). The route does not gate on
-  //     scope, so authentication alone is sufficient.
-  //   - Route declares a `requiredPermission`: wildcard tokens pass;
-  //     narrow-scope tokens must list the required permission.
-  //
-  // v1.4.25 W10 reconcile (code-review H2): the previous "no
-  // requiredPermission ⇒ wildcard only" rule misread the contract.
-  // Routes without a declared scope (`/api/measurements/by-external-ids`,
-  // `/api/personal-records`, `/api/medications/[id]/glp1`,
-  // `/api/dashboard/glp1`) 403'd every narrow-scope token even though
-  // those routes did not intend to restrict by scope at all. Allowing
-  // any authenticated token through when the route does not declare a
-  // scope unblocks the v1.5 iOS endpoints while keeping the scoped-
-  // route gating below intact.
-  const hasWildcardPermission = apiToken.permissions.includes("*");
-
-  if (
-    requiredPermission &&
-    !hasWildcardPermission &&
-    !apiToken.permissions.includes(requiredPermission)
-  ) {
-    auditLog("auth.bearer.failure", {
-      userId: apiToken.userId,
-      details: {
-        reason: "insufficient_permissions",
-        tokenId: apiToken.id,
-        required: requiredPermission,
-      },
-    }).catch(() => {});
-    throw new HttpError(403, "Insufficient permissions");
-  }
-
-  const user = await prisma.user.findUnique({
-    where: { id: apiToken.userId },
-  });
-
-  if (!user) {
-    auditLog("auth.bearer.failure", {
-      userId: apiToken.userId,
-      details: { reason: "user_missing", tokenId: apiToken.id },
-    }).catch(() => {});
-    throw new HttpError(401, "Invalid token");
-  }
-
-  // Fire-and-forget: refresh lastUsedAt without blocking the request.
-  prisma.apiToken
-    .update({
-      where: { id: apiToken.id },
-      data: { lastUsedAt: new Date() },
-    })
-    .catch(() => {});
+  const { user, tokenId, expiresAt } = resolution;
 
   auditLog("auth.bearer.success", {
     userId: user.id,
-    details: { tokenId: apiToken.id },
+    details: { tokenId },
   }).catch(() => {});
 
   const evt = getEvent();
@@ -406,13 +347,8 @@ async function authenticateBearer(
     });
   }
 
-  // Use the token expiry as the session expiry; fall back to a 30-day window if
-  // the token has no fixed expiry so the contract `{ expiresAt: Date }` holds.
-  const expiresAt =
-    apiToken.expiresAt ?? new Date(Date.now() + 30 * 24 * 60 * 60 * 1000);
-
   return {
-    session: { id: apiToken.id, expiresAt },
+    session: { id: tokenId, expiresAt },
     user,
   };
 }
diff --git a/src/lib/auth/__tests__/bearer.test.ts b/src/lib/auth/__tests__/bearer.test.ts
new file mode 100644
index 000000000..f3dc89159
--- /dev/null
+++ b/src/lib/auth/__tests__/bearer.test.ts
@@ -0,0 +1,130 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+vi.mock("@/lib/db", () => ({
+  prisma: {
+    apiToken: { findUnique: vi.fn(), update: vi.fn() },
+    user: { findUnique: vi.fn() },
+  },
+}));
+vi.mock("@/lib/auth/hmac", () => ({ hashToken: vi.fn() }));
+
+import { resolveBearerToken, BearerAuthError } from "../bearer";
+import { prisma } from "@/lib/db";
+import { hashToken } from "@/lib/auth/hmac";
+
+const FAKE_HASH = "deadbeefcafef00d";
+const RAW_TOKEN = "hlk_" + "a".repeat(64);
+const FAKE_USER = { id: "user-1", role: "USER" };
+
+beforeEach(() => {
+  vi.resetAllMocks();
+  vi.mocked(hashToken).mockReturnValue(FAKE_HASH);
+  vi.mocked(prisma.apiToken.update).mockResolvedValue({} as never);
+});
+
+describe("resolveBearerToken", () => {
+  it("looks the token up by HMAC hash, never the plaintext", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue({
+      id: "token-1",
+      userId: "user-1",
+      permissions: ["*"],
+      revoked: false,
+      expiresAt: new Date(Date.now() + 86_400_000),
+    } as never);
+    vi.mocked(prisma.user.findUnique).mockResolvedValue(FAKE_USER as never);
+
+    const res = await resolveBearerToken(RAW_TOKEN);
+
+    expect(hashToken).toHaveBeenCalledWith(RAW_TOKEN);
+    expect(prisma.apiToken.findUnique).toHaveBeenCalledWith(
+      expect.objectContaining({ where: { tokenHash: FAKE_HASH } }),
+    );
+    expect(res.user.id).toBe("user-1");
+    expect(res.tokenId).toBe("token-1");
+    expect(res.permissions).toEqual(["*"]);
+    expect(prisma.apiToken.update).toHaveBeenCalledWith({
+      where: { id: "token-1" },
+      data: { lastUsedAt: expect.any(Date) },
+    });
+  });
+
+  it("rejects an unknown token (401)", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue(null as never);
+    await expect(resolveBearerToken(RAW_TOKEN)).rejects.toMatchObject({
+      statusCode: 401,
+      reason: "unknown_token",
+    } satisfies Partial<BearerAuthError>);
+    expect(prisma.user.findUnique).not.toHaveBeenCalled();
+  });
+
+  it("rejects a revoked token (401)", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue({
+      id: "token-2",
+      userId: "user-1",
+      permissions: [],
+      revoked: true,
+      expiresAt: null,
+    } as never);
+    await expect(resolveBearerToken(RAW_TOKEN)).rejects.toMatchObject({
+      statusCode: 401,
+      reason: "revoked",
+    });
+  });
+
+  it("rejects an expired token (401)", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue({
+      id: "token-3",
+      userId: "user-1",
+      permissions: [],
+      revoked: false,
+      expiresAt: new Date(Date.now() - 60_000),
+    } as never);
+    await expect(resolveBearerToken(RAW_TOKEN)).rejects.toMatchObject({
+      statusCode: 401,
+      reason: "expired",
+    });
+  });
+
+  it("rejects a narrow-scope token missing the required permission (403)", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue({
+      id: "token-4",
+      userId: "user-1",
+      permissions: ["something:else"],
+      revoked: false,
+      expiresAt: null,
+    } as never);
+    await expect(
+      resolveBearerToken(RAW_TOKEN, "health:write"),
+    ).rejects.toMatchObject({
+      statusCode: 403,
+      reason: "insufficient_permissions",
+    });
+    expect(prisma.user.findUnique).not.toHaveBeenCalled();
+  });
+
+  it("admits any valid token when no permission is required (REQ-SEC-5)", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue({
+      id: "token-5",
+      userId: "user-1",
+      permissions: ["medication:ingest"],
+      revoked: false,
+      expiresAt: null,
+    } as never);
+    vi.mocked(prisma.user.findUnique).mockResolvedValue(FAKE_USER as never);
+    const res = await resolveBearerToken(RAW_TOKEN);
+    expect(res.user.id).toBe("user-1");
+  });
+
+  it("admits a wildcard token for any required permission", async () => {
+    vi.mocked(prisma.apiToken.findUnique).mockResolvedValue({
+      id: "token-6",
+      userId: "user-1",
+      permissions: ["*"],
+      revoked: false,
+      expiresAt: null,
+    } as never);
+    vi.mocked(prisma.user.findUnique).mockResolvedValue(FAKE_USER as never);
+    const res = await resolveBearerToken(RAW_TOKEN, "health:write");
+    expect(res.user.id).toBe("user-1");
+  });
+});
diff --git a/src/lib/auth/bearer.ts b/src/lib/auth/bearer.ts
new file mode 100644
index 000000000..694f27f14
--- /dev/null
+++ b/src/lib/auth/bearer.ts
@@ -0,0 +1,144 @@
+/**
+ * Canonical Bearer-token validation — the single source of truth for resolving
+ * a raw `hlk_<hex>` token to a user.
+ *
+ * Extracted from `api-handler.ts` so it can be reused outside a Next.js request
+ * scope (the local MCP stdio transport runs in a plain Node process and must not
+ * drag `next/server` / `next/headers` / the Wide-Event machinery into its import
+ * graph). The HTTP edge (`requireAuth` → `authenticateBearer`) and the MCP edge
+ * both call this one function, so the revoked / expired / scope / `lastUsedAt`
+ * semantics can never drift between the two wires.
+ *
+ * This module is deliberately lean: it depends only on the HMAC hasher and
+ * Prisma. Audit-log emission + Wide-Event annotation stay with each caller (the
+ * HTTP path keeps its existing `auth.bearer.*` audit trail), so this layer adds
+ * no I/O beyond the two reads the validation needs.
+ */
+import type { User } from "@/generated/prisma/client";
+import { prisma } from "@/lib/db";
+import { hashToken } from "@/lib/auth/hmac";
+
+/** Why a Bearer token was rejected. Stable handles for audit details. */
+export type BearerAuthReason =
+  | "unknown_token"
+  | "revoked"
+  | "expired"
+  | "insufficient_permissions"
+  | "user_missing";
+
+/**
+ * Thrown when a token fails validation. Carries the HTTP status the HTTP edge
+ * should surface plus the machine `reason` (and, when known, the owning
+ * `userId` / `tokenId`) so a caller can write a faithful audit entry without
+ * re-deriving them.
+ */
+export class BearerAuthError extends Error {
+  constructor(
+    public readonly statusCode: 401 | 403,
+    public readonly reason: BearerAuthReason,
+    public readonly userId?: string,
+    public readonly tokenId?: string,
+  ) {
+    super(reason);
+    this.name = "BearerAuthError";
+  }
+}
+
+/** The validated identity behind a Bearer token. */
+export interface BearerResolution {
+  user: User;
+  /** The `ApiToken` row id (the token-id half of the `<user>:<token>` binding). */
+  tokenId: string;
+  /** The token's granted scopes (`["*"]` = wildcard). */
+  permissions: string[];
+  /** Token expiry, or a 30-day fallback window when the token has no fixed expiry. */
+  expiresAt: Date;
+}
+
+/**
+ * Resolve a raw `hlk_<hex>` token to its user, or throw `BearerAuthError`.
+ *
+ * Lookups are by HMAC hash only — the plaintext token is never compared against
+ * a stored value. When `requiredPermission` is set, a non-wildcard token must
+ * list it; an unset `requiredPermission` admits any valid token (matching the
+ * "route declares no scope ⇒ authentication alone is sufficient" contract).
+ *
+ * `lastUsedAt` is refreshed fire-and-forget on success.
+ */
+export async function resolveBearerToken(
+  rawToken: string,
+  requiredPermission?: string,
+): Promise<BearerResolution> {
+  const tokenHashValue = hashToken(rawToken);
+
+  const apiToken = await prisma.apiToken.findUnique({
+    where: { tokenHash: tokenHashValue },
+    select: {
+      id: true,
+      userId: true,
+      permissions: true,
+      revoked: true,
+      expiresAt: true,
+    },
+  });
+
+  if (!apiToken) {
+    throw new BearerAuthError(401, "unknown_token");
+  }
+
+  if (apiToken.revoked) {
+    throw new BearerAuthError(401, "revoked", apiToken.userId, apiToken.id);
+  }
+
+  if (apiToken.expiresAt && apiToken.expiresAt <= new Date()) {
+    throw new BearerAuthError(401, "expired", apiToken.userId, apiToken.id);
+  }
+
+  // `["*"]` is the wildcard scope. A route that declares no `requiredPermission`
+  // accepts any valid token; one that declares a scope accepts wildcard tokens
+  // and narrow-scope tokens that list that scope.
+  const hasWildcardPermission = apiToken.permissions.includes("*");
+  if (
+    requiredPermission &&
+    !hasWildcardPermission &&
+    !apiToken.permissions.includes(requiredPermission)
+  ) {
+    throw new BearerAuthError(
+      403,
+      "insufficient_permissions",
+      apiToken.userId,
+      apiToken.id,
+    );
+  }
+
+  const user = await prisma.user.findUnique({
+    where: { id: apiToken.userId },
+  });
+
+  if (!user) {
+    throw new BearerAuthError(
+      401,
+      "user_missing",
+      apiToken.userId,
+      apiToken.id,
+    );
+  }
+
+  // Fire-and-forget: refresh lastUsedAt without blocking the caller.
+  prisma.apiToken
+    .update({
+      where: { id: apiToken.id },
+      data: { lastUsedAt: new Date() },
+    })
+    .catch(() => {});
+
+  const expiresAt =
+    apiToken.expiresAt ?? new Date(Date.now() + 30 * 24 * 60 * 60 * 1000);
+
+  return {
+    user,
+    tokenId: apiToken.id,
+    permissions: apiToken.permissions,
+    expiresAt,
+  };
+}