fix: key MCP identity on the canonical issuer, not the token issuer

Verifying against OIDC_ISSUER_MCP fixed the 401, but would have introduced a
quieter bug. Identity is keyed on (oidc_iss, oidc_sub) and
userContextFromClaims UPSERTS rather than failing, so a token carrying the MCP
application's issuer would have created a SECOND user row for the same person:
MCP calls would succeed against an account holding none of their memories, and
nothing would appear broken.

Authentik's `sub` is `user.uid`, a user-level value that is identical across
providers (verified against the live instance), so the issuer is the only
differing component. Pin it to OIDC_ISSUER after verification.

No stray rows exist to clean up — verification failed before this path could
ever create one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.env.example

@@ -31,6 +31,11 @@ ACME_EMAIL=you@example.com
 # resource server). See README.md for exact provider settings.
 # -----------------------------------------------------------------------------
 OIDC_ISSUER=https://auth.example.com/application/o/shared-memory/
+# Issuer of MCP access tokens, when the MCP endpoint is a separate application
+# in your IdP (it usually is). Authentik stamps each token with its own app
+# slug, so verifying MCP tokens against OIDC_ISSUER fails with
+# "claim invalid: iss". Defaults to OIDC_ISSUER.
+OIDC_ISSUER_MCP=https://auth.example.com/application/o/shared-memory-mcp/
 OIDC_CLIENT_ID_WEB=replace-me
 OIDC_CLIENT_SECRET_WEB=replace-me
 OIDC_CLIENT_ID_MCP=replace-me

README.md

@@ -144,6 +144,7 @@ Copy `.env.example` and fill in the values below.
 | `OIDC_CLIENT_SECRET_WEB` | both | Client secret of the Web-UI client. |
 | `OIDC_CLIENT_ID_MCP` | both | Client ID of the MCP resource-server client in your IdP. |
 | `OIDC_AUDIENCE` | both | Audience string the MCP access token must carry in its `aud` claim. Recommended: `shared-memory`. |
+| `OIDC_ISSUER_MCP` | optional | Issuer of MCP access tokens when the MCP endpoint is a separate IdP application (Authentik stamps each app's tokens with its own slug). Defaults to `OIDC_ISSUER`. |
 | `OIDC_AUDIENCE_SCOPE` | optional | Name of the IdP scope whose mapping emits that `aud` claim. Advertised in `scopes_supported` so clients request it. Defaults to `aud-<OIDC_AUDIENCE>`. |
 | `POSTGRES_USER` / `POSTGRES_PASSWORD` / `POSTGRES_DB` | both | Local Postgres credentials. |
 | `NEXTAUTH_SECRET` | both | Session-cookie signing key. Generate with `openssl rand -base64 32`. |
@@ -322,6 +323,25 @@ reliable pattern:
 >   | jq .scopes_supported     # must include aud-<your audience>
 > ```
 >
+> **Second trap, same failure surface:** the MCP endpoint is a *separate
+> application* from the Web UI, and Authentik's default `per_provider` issuer
+> mode stamps each token with its own application slug. So MCP tokens carry
+> `iss: .../application/o/shared-memory-mcp/` while `OIDC_ISSUER` points at
+> `.../application/o/shared-memory/`, and verification fails with
+> `claim invalid: iss` even once `aud` is correct. Set `OIDC_ISSUER_MCP` to the
+> MCP application's issuer. Confirm which one your tokens actually carry:
+>
+> ```bash
+> curl -s https://auth.example.com/application/o/shared-memory-mcp/.well-known/openid-configuration | jq .issuer
+> ```
+>
+> **Identity note:** the app verifies MCP tokens against `OIDC_ISSUER_MCP` but
+> keys the user record on `OIDC_ISSUER`. Authentik's `sub` is `user.uid`, which
+> is stable across providers, so the same person resolves to the same row
+> whether they arrive via the Web UI or the MCP endpoint. Without that
+> normalization the MCP path silently creates a second, empty account instead
+> of failing visibly.
+>
 > Note also that Claude Code sends an RFC 8707 `resource` parameter on the
 > authorize request; Authentik 2026.5 ignores it, so it cannot be relied on
 > for audience binding. The scope mapping is what sets `aud`.

apps/web/app/.well-known/oauth-protected-resource/route.ts

@@ -1,5 +1,6 @@
 import { NextResponse } from "next/server";
 import { env } from "@/lib/env";
+import { mcpIssuer } from "@/lib/auth/jwt";
 
 export const runtime = "nodejs";
 export const dynamic = "force-dynamic";
@@ -22,7 +23,10 @@ export function GET() {
 
   return NextResponse.json({
     resource,
-    authorization_servers: [env().OIDC_ISSUER],
+    // The MCP application's issuer, which is not necessarily the Web UI's —
+    // see mcpIssuer(). Advertising the wrong one sends clients to a discovery
+    // document whose tokens this endpoint will then reject on `iss`.
+    authorization_servers: [mcpIssuer()],
     scopes_supported: ["openid", "profile", "email", audienceScope],
     bearer_methods_supported: ["header"],
     resource_documentation: `${resource}/`,

apps/web/lib/auth/jwt.ts

@@ -23,13 +23,21 @@ type GlobalWithJwks = typeof globalThis & {
 };
 const g = globalThis as GlobalWithJwks;
 
+/**
+ * Issuer of MCP access tokens. The MCP endpoint is a separate application in
+ * the IdP from the Web UI, and Authentik stamps each token with its own
+ * application slug, so this is NOT interchangeable with OIDC_ISSUER.
+ */
+export function mcpIssuer(): string {
+  return (env().OIDC_ISSUER_MCP ?? env().OIDC_ISSUER).replace(/\/$/, "");
+}
+
 function jwks() {
   if (g.__sharedMemoryJwks) return g.__sharedMemoryJwks;
   // Authentik discovery is at `${issuer}/.well-known/openid-configuration`;
   // the JWKS URI is normally `${issuer}/jwks/` or `${issuer}/.well-known/jwks.json`.
   // Authentik canonically serves `${issuer}/jwks/`.
-  const issuer = env().OIDC_ISSUER.replace(/\/$/, "");
+  const url = new URL(`${mcpIssuer()}/jwks/`);
-  const url = new URL(`${issuer}/jwks/`);
   g.__sharedMemoryJwks = createRemoteJWKSet(url, {
     cacheMaxAge: 10 * 60 * 1000, // 10 min
     cooldownDuration: 30 * 1000,
@@ -118,7 +126,7 @@ export async function authenticateBearer(authHeader: string | null): Promise<Aut
     }
 
     const { payload } = await jwtVerify(token, jwks(), {
-      issuer: env().OIDC_ISSUER,
+      issuer: mcpIssuer(),
       audience: env().OIDC_AUDIENCE,
     });
     if (!payload.sub) {
@@ -127,7 +135,24 @@ export async function authenticateBearer(authHeader: string | null): Promise<Aut
         buildWwwAuthenticate("invalid_token", "missing sub"),
       );
     }
-    return { ...payload, groups: extractGroupsClaim(payload) } as AuthenticatedClaims;
+    // Normalize the issuer for identity purposes.
+    //
+    // The token was just verified against mcpIssuer() — that check is done.
+    // But identity is keyed on (oidc_iss, oidc_sub), and the Web UI signs
+    // people in through a DIFFERENT application whose tokens carry
+    // OIDC_ISSUER. Authentik's `sub` is stable across providers (it is
+    // `user.uid`, a user-level value), so the only thing that differs is the
+    // issuer.
+    //
+    // Leave it un-normalized and userContextFromClaims — which UPSERTS rather
+    // than failing — quietly creates a SECOND user row for the same human:
+    // MCP writes would land in an account with none of their memories, and
+    // nothing would look broken. Pin identity to the canonical issuer.
+    return {
+      ...payload,
+      iss: env().OIDC_ISSUER,
+      groups: extractGroupsClaim(payload),
+    } as AuthenticatedClaims;
   } catch (err) {
     if (err instanceof UnauthorizedError) throw err;
     const desc =

apps/web/lib/env.ts

@@ -4,6 +4,16 @@ const Bool = z
   .union([z.boolean(), z.enum(["true", "false", "1", "0"])])
   .transform((v) => v === true || v === "true" || v === "1");
 
+/**
+ * Treat an empty string as "not set".
+ *
+ * docker-compose renders `${VAR:-}` as an empty string rather than omitting
+ * the key, so an unset optional var arrives as "" and would otherwise fail
+ * `.url()` / `.min(1)` validation and take the whole app down at boot.
+ */
+const optional = <T extends z.ZodTypeAny>(schema: T) =>
+  z.preprocess((v) => (v === "" ? undefined : v), schema.optional());
+
 const envSchema = z.object({
   NODE_ENV: z.enum(["development", "test", "production"]).default("development"),
   LOG_LEVEL: z.enum(["debug", "info", "warn", "error"]).default("info"),
@@ -13,6 +23,19 @@ const envSchema = z.object({
 
   // Authentik OIDC
   OIDC_ISSUER: z.string().url(),
+
+  // Issuer of MCP *access tokens*, when it differs from OIDC_ISSUER.
+  //
+  // The Web UI and the MCP endpoint are two separate applications in the IdP,
+  // and Authentik's default `per_provider` issuer mode stamps each token with
+  // its own application slug. So the web app issues
+  // `.../application/o/<slug>/` while the MCP provider issues
+  // `.../application/o/<slug>-mcp/`, and verifying MCP tokens against
+  // OIDC_ISSUER fails with "claim invalid: iss".
+  //
+  // Set this to the MCP application's issuer. Defaults to OIDC_ISSUER for
+  // single-application setups.
+  OIDC_ISSUER_MCP: optional(z.string().url()),
   OIDC_CLIENT_ID_WEB: z.string().min(1),
   OIDC_CLIENT_SECRET_WEB: z.string().min(1),
   OIDC_CLIENT_ID_MCP: z.string().min(1),
@@ -27,7 +50,7 @@ const envSchema = z.object({
   // every token arrives without an `aud` claim (-> 401 "claim invalid: aud").
   //
   // Defaults to the `aud-<audience>` convention used in the README setup.
-  OIDC_AUDIENCE_SCOPE: z.string().min(1).optional(),
+  OIDC_AUDIENCE_SCOPE: optional(z.string().min(1)),
 
   // Database
   DATABASE_URL: z.string().url(),

docker-compose.yml

@@ -113,6 +113,10 @@ services:
       OIDC_CLIENT_SECRET_WEB: ${OIDC_CLIENT_SECRET_WEB:?required}
       OIDC_CLIENT_ID_MCP: ${OIDC_CLIENT_ID_MCP:?required}
       OIDC_AUDIENCE: ${OIDC_AUDIENCE:?required}
+      # Optional. This block is an explicit allow-list, not env_file — a var
+      # added to .env but not listed here never reaches the container.
+      OIDC_ISSUER_MCP: ${OIDC_ISSUER_MCP:-}
+      OIDC_AUDIENCE_SCOPE: ${OIDC_AUDIENCE_SCOPE:-}
 
       DATABASE_URL: postgres://${POSTGRES_USER}:${POSTGRES_PASSWORD}@db:5432/${POSTGRES_DB}