diff --git a/app-hooks/post-installation/15-setup-keycloak-provider.sh b/app-hooks/post-installation/15-setup-keycloak-provider.sh
new file mode 100755
index 0000000..e8341e2
--- /dev/null
+++ b/app-hooks/post-installation/15-setup-keycloak-provider.sh
@@ -0,0 +1,100 @@
+#!/bin/bash
+#
+# Configure user_oidc to accept bearer tokens from Keycloak
+#
+# This script sets up Keycloak as an external OIDC provider for Nextcloud.
+# It enables bearer token validation, allowing the MCP server to use Keycloak
+# tokens to access Nextcloud APIs without admin credentials.
+#
+
+set -e
+
+echo "===================================================================="
+echo "Configuring user_oidc provider for Keycloak..."
+echo "===================================================================="
+
+# Wait for Keycloak to be ready and realm to be available
+echo "Waiting for Keycloak realm to be available..."
+MAX_RETRIES=30
+RETRY_COUNT=0
+
+while [ $RETRY_COUNT -lt $MAX_RETRIES ]; do
+    if curl -sf http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration > /dev/null 2>&1; then
+        echo "✓ Keycloak realm is ready"
+        break
+    fi
+    echo "  Waiting for Keycloak... (attempt $((RETRY_COUNT + 1))/$MAX_RETRIES)"
+    sleep 5
+    RETRY_COUNT=$((RETRY_COUNT + 1))
+done
+
+if [ $RETRY_COUNT -eq $MAX_RETRIES ]; then
+    echo "⚠ Warning: Keycloak not available after $MAX_RETRIES attempts"
+    echo "  Keycloak provider will not be configured"
+    echo "  You can configure it manually using:"
+    echo "  docker compose exec app php occ user_oidc:provider keycloak \\"
+    echo "    --clientid='nextcloud' \\"
+    echo "    --clientsecret='nextcloud-secret-change-in-production' \\"
+    echo "    --discoveryuri='http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration' \\"
+    echo "    --check-bearer=1 \\"
+    echo "    --bearer-provisioning=1 \\"
+    echo "    --unique-uid=1"
+    exit 0
+fi
+
+# Check if provider already exists
+if php /var/www/html/occ user_oidc:provider keycloak 2>/dev/null | grep -q "Identifier"; then
+    echo "  Keycloak provider already exists, updating configuration..."
+
+    # Update existing provider
+    php /var/www/html/occ user_oidc:provider keycloak \
+        --clientid="nextcloud" \
+        --clientsecret="nextcloud-secret-change-in-production" \
+        --discoveryuri="http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration" \
+        --check-bearer=1 \
+        --bearer-provisioning=1 \
+        --unique-uid=1 \
+        --mapping-uid="sub" \
+        --mapping-display-name="name" \
+        --mapping-email="email" \
+        --scope="openid profile email offline_access"
+
+    echo "✓ Updated Keycloak provider configuration"
+else
+    echo "  Creating new Keycloak provider..."
+
+    # Create new provider
+    php /var/www/html/occ user_oidc:provider keycloak \
+        --clientid="nextcloud" \
+        --clientsecret="nextcloud-secret-change-in-production" \
+        --discoveryuri="http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration" \
+        --check-bearer=1 \
+        --bearer-provisioning=1 \
+        --unique-uid=1 \
+        --mapping-uid="sub" \
+        --mapping-display-name="name" \
+        --mapping-email="email" \
+        --scope="openid profile email offline_access"
+
+    echo "✓ Created Keycloak provider"
+fi
+
+# Display provider details
+echo ""
+echo "Keycloak provider configuration:"
+php /var/www/html/occ user_oidc:provider keycloak
+
+echo ""
+echo "===================================================================="
+echo "✓ Keycloak provider configured successfully"
+echo "===================================================================="
+echo ""
+echo "Key features enabled:"
+echo "  • Bearer token validation (--check-bearer=1)"
+echo "  • Automatic user provisioning (--bearer-provisioning=1)"
+echo "  • Unique user IDs (--unique-uid=1)"
+echo "  • Offline access scope (for refresh tokens)"
+echo ""
+echo "MCP server can now use Keycloak tokens to access Nextcloud APIs"
+echo "without admin credentials (ADR-002 architecture)."
+echo ""
diff --git a/docker-compose.yml b/docker-compose.yml
index 75004e4..10f4831 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -96,14 +96,59 @@ services:
 
   keycloak:
     image: quay.io/keycloak/keycloak:26.4.2
-    command: ["start-dev"]
+    command: ["start-dev", "--import-realm"]
     ports:
       - 127.0.0.1:8888:8080
     environment:
       - KC_BOOTSTRAP_ADMIN_USERNAME=admin
       - KC_BOOTSTRAP_ADMIN_PASSWORD=admin
+    volumes:
+      - ./keycloak/realm-export.json:/opt/keycloak/data/import/realm.json:ro
+    healthcheck:
+      test: ["CMD-SHELL", "exec 3<>/dev/tcp/localhost/8080 && echo -e 'GET /realms/nextcloud-mcp HTTP/1.1\\r\\nHost: localhost\\r\\nConnection: close\\r\\n\\r\\n' >&3 && cat <&3 | grep -q 'HTTP/1.1 200'"]
+      interval: 10s
+      timeout: 5s
+      retries: 30
+
+  mcp-keycloak:
+    build: .
+    command: ["--transport", "streamable-http", "--oauth", "--port", "8002"]
+    restart: always
+    depends_on:
+      keycloak:
+        condition: service_healthy
+      app:
+        condition: service_started
+    ports:
+      - 127.0.0.1:8002:8002
+    environment:
+      # OAuth Provider: Keycloak
+      - OAUTH_PROVIDER=keycloak
+      - KEYCLOAK_URL=http://keycloak:8080
+      - KEYCLOAK_REALM=nextcloud-mcp
+      - KEYCLOAK_CLIENT_ID=nextcloud-mcp-server
+      - KEYCLOAK_CLIENT_SECRET=mcp-secret-change-in-production
+      - KEYCLOAK_DISCOVERY_URL=http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration
+
+      # Nextcloud API endpoint (for accessing APIs with validated token)
+      - NEXTCLOUD_HOST=http://app:80
+      - NEXTCLOUD_MCP_SERVER_URL=http://localhost:8002
+      - NEXTCLOUD_PUBLIC_ISSUER_URL=http://localhost:8888
+
+      # Refresh token storage (ADR-002 Tier 1)
+      - ENABLE_OFFLINE_ACCESS=true
+      - TOKEN_ENCRYPTION_KEY=${TOKEN_ENCRYPTION_KEY:-}
+      - TOKEN_STORAGE_DB=/app/data/tokens.db
+      - NEXTCLOUD_OIDC_CLIENT_STORAGE=/app/.oauth/keycloak_oauth_client.json
+
+      # NO admin credentials - using Keycloak OAuth only!
+    volumes:
+      - keycloak-tokens:/app/data
+      - keycloak-oauth-storage:/app/.oauth
 
 volumes:
   nextcloud:
   db:
   oauth-client-storage:
+  keycloak-tokens:
+  keycloak-oauth-storage:
diff --git a/docs/audience-validation-setup.md b/docs/audience-validation-setup.md
new file mode 100644
index 0000000..2786ec9
--- /dev/null
+++ b/docs/audience-validation-setup.md
@@ -0,0 +1,519 @@
+# Audience Validation Setup
+
+## Overview
+
+This document explains the **separate clients architecture** for Keycloak → MCP Server → Nextcloud integration, following OAuth 2.0 best practices and RFC 8707 (Resource Indicators).
+
+## Architecture: Separate Clients Pattern
+
+```
+Keycloak Realm: nextcloud-mcp
+├── Client: "nextcloud" (Resource Server)
+│   └── Represents Nextcloud as a protected resource
+│   └── Used by user_oidc for bearer token validation
+│   └── Validates tokens with aud="nextcloud"
+│
+└── Client: "nextcloud-mcp-server" (OAuth Client)
+    └── MCP Server uses this to REQUEST tokens
+    └── Issues tokens with aud="nextcloud" (targeting resource)
+    └── Future: aud=["nextcloud", "other-service"]
+
+Token Flow:
+MCP Server (client: nextcloud-mcp-server)
+  ↓ requests token from Keycloak
+Token issued:
+  - aud: "nextcloud"             (intended for Nextcloud resource)
+  - azp: "nextcloud-mcp-server"  (requested by MCP Server)
+  - preferred_username: "admin"  (on behalf of user)
+  ↓ sent to Nextcloud API
+Nextcloud user_oidc (client: nextcloud)
+  ✓ validates aud matches configured client_id
+```
+
+**Key Benefits**:
+- ✅ **Proper OAuth separation**: OAuth client ≠ resource server
+- ✅ **Future extensibility**: MCP Server can request multi-resource tokens
+- ✅ **RFC 8707 compliance**: Audience indicates intended resource
+- ✅ **Clear requester identification**: azp claim identifies MCP Server
+
+## Token Claims
+
+Tokens issued by the `nextcloud-mcp-server` client contain:
+
+- **`aud: "nextcloud"`** - Audience: Token intended for Nextcloud resource server (matches user_oidc client_id)
+- **`azp: "nextcloud-mcp-server"`** - Authorized Party: Identifies MCP Server as the OAuth client that requested the token
+- **`preferred_username: "admin"`** - User identifier (Keycloak uses this for password grant; `sub` for authorization_code grant)
+- **`scope: "openid profile email offline_access"`** - Requested scopes including offline access for background jobs
+
+**How user_oidc Validates**:
+1. SelfEncodedValidator checks: `aud == user_oidc.client_id`?
+   - ✓ "nextcloud" == "nextcloud" → PASS
+2. Fast JWT verification with JWKS (no HTTP call to userinfo endpoint)
+3. User provisioned based on `preferred_username` or `sub` claim
+
+**For Background Jobs**:
+- MCP Server stores encrypted refresh tokens
+- Refreshes access tokens when needed
+- All tokens have `aud: "nextcloud"` → validated by user_oidc
+- No admin credentials required
+
+## Configuration
+
+The configuration requires **two separate clients** in Keycloak:
+
+1. **`nextcloud`** - Resource server client (for user_oidc validation)
+2. **`nextcloud-mcp-server`** - OAuth client (for MCP Server to request tokens)
+
+### 1. Keycloak - Create Resource Server Client
+
+First, create the `nextcloud` client that represents Nextcloud as a resource server:
+
+**Via Keycloak Admin API:**
+
+```bash
+# Get admin token
+ADMIN_TOKEN=$(curl -X POST "http://localhost:8888/realms/master/protocol/openid-connect/token" \
+  -d "grant_type=password" \
+  -d "client_id=admin-cli" \
+  -d "username=admin" \
+  -d "password=admin" | jq -r '.access_token')
+
+# Create 'nextcloud' resource server client
+curl -X POST "http://localhost:8888/admin/realms/nextcloud-mcp/clients" \
+  -H "Authorization: Bearer $ADMIN_TOKEN" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "clientId": "nextcloud",
+    "name": "Nextcloud Resource Server",
+    "description": "Resource server for Nextcloud APIs - used by user_oidc for bearer token validation",
+    "enabled": true,
+    "clientAuthenticatorType": "client-secret",
+    "secret": "nextcloud-secret-change-in-production",
+    "bearerOnly": true,
+    "standardFlowEnabled": false,
+    "directAccessGrantsEnabled": false,
+    "serviceAccountsEnabled": false,
+    "publicClient": false
+  }'
+```
+
+**Via Realm Export** (`keycloak/realm-export.json`):
+
+```json
+{
+  "clients": [
+    {
+      "clientId": "nextcloud",
+      "name": "Nextcloud Resource Server",
+      "enabled": true,
+      "bearerOnly": true,
+      "secret": "nextcloud-secret-change-in-production"
+    }
+  ]
+}
+```
+
+### 2. Keycloak - Create OAuth Client with Audience Mapper
+
+Next, create the `nextcloud-mcp-server` client that MCP Server uses to request tokens:
+
+**Via Keycloak Admin API:**
+
+```bash
+# Create 'nextcloud-mcp-server' OAuth client
+curl -X POST "http://localhost:8888/admin/realms/nextcloud-mcp/clients" \
+  -H "Authorization: Bearer $ADMIN_TOKEN" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "clientId": "nextcloud-mcp-server",
+    "name": "Nextcloud MCP Server",
+    "enabled": true,
+    "clientAuthenticatorType": "client-secret",
+    "secret": "mcp-secret-change-in-production",
+    "standardFlowEnabled": true,
+    "directAccessGrantsEnabled": true,
+    "redirectUris": ["http://localhost:*/callback"]
+  }'
+
+# Get client internal ID
+CLIENT_ID=$(curl "http://localhost:8888/admin/realms/nextcloud-mcp/clients" \
+  -H "Authorization: Bearer $ADMIN_TOKEN" | jq -r '.[] | select(.clientId=="nextcloud-mcp-server") | .id')
+
+# Add audience mapper targeting 'nextcloud' resource
+curl -X POST "http://localhost:8888/admin/realms/nextcloud-mcp/clients/$CLIENT_ID/protocol-mappers/models" \
+  -H "Authorization: Bearer $ADMIN_TOKEN" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "name": "audience-nextcloud",
+    "protocol": "openid-connect",
+    "protocolMapper": "oidc-audience-mapper",
+    "consentRequired": false,
+    "config": {
+      "included.custom.audience": "nextcloud",
+      "access.token.claim": "true",
+      "id.token.claim": "false"
+    }
+  }'
+```
+
+**Option B: Via Realm Export** (for infrastructure-as-code)
+
+Update `keycloak/realm-export.json`:
+
+```json
+{
+  "clients": [
+    {
+      "clientId": "nextcloud-mcp-server",
+      "name": "Nextcloud MCP Server",
+      "protocolMappers": [
+        {
+          "name": "audience-nextcloud-mcp-server",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-audience-mapper",
+          "consentRequired": false,
+          "config": {
+            "included.custom.audience": "nextcloud-mcp-server",
+            "access.token.claim": "true",
+            "id.token.claim": "false"
+          }
+        }
+      ]
+    }
+  ]
+}
+```
+
+Then re-import realm or restart Keycloak.
+
+**Option C: Via Keycloak Admin UI**
+
+1. Go to Keycloak Admin Console → Realm → Clients → `nextcloud-mcp-server`
+2. Click "Client scopes" tab
+3. Click "Add client scope" → "Create dedicated scope"
+4. Add protocol mapper: "Audience"
+   - Mapper Type: `Audience`
+   - Included Custom Audience: `nextcloud`
+   - Add to access token: ON
+   - Add to ID token: OFF
+
+### 3. Nextcloud user_oidc - Configure Resource Server Client
+
+Configure user_oidc to use the `nextcloud` resource server client:
+
+```bash
+docker compose exec app php occ user_oidc:provider keycloak \
+  --clientid="nextcloud" \
+  --clientsecret="nextcloud-secret-change-in-production" \
+  --discoveryuri="http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration" \
+  --check-bearer=1 \
+  --bearer-provisioning=1 \
+  --unique-uid=1 \
+  --mapping-uid="sub" \
+  --mapping-display-name="name" \
+  --mapping-email="email"
+```
+
+**Result**: user_oidc validates tokens with `aud="nextcloud"` using SelfEncodedValidator (fast JWT verification).
+
+### 3. Nextcloud user_oidc - Realm-Level Validation
+
+Nextcloud's `user_oidc` app validates at **realm level** via userinfo endpoint:
+
+- ✅ **No configuration needed** - works automatically
+- ✅ Validates any token from Keycloak realm
+- ✅ Audience check is **optional** (disabled by default)
+
+**Optional: Disable strict audience checking** (if enabled):
+
+```bash
+docker compose exec app php occ config:app:set user_oidc \
+  selfencoded_bearer_validation_audience_check --value=false --type=boolean
+```
+
+## Verification
+
+### 1. Check Token Claims
+
+```bash
+# Get token from Keycloak
+TOKEN=$(curl -X POST "http://localhost:8888/realms/nextcloud-mcp/protocol/openid-connect/token" \
+  -d "grant_type=password" \
+  -d "client_id=nextcloud-mcp-server" \
+  -d "client_secret=mcp-secret-change-in-production" \
+  -d "username=admin" \
+  -d "password=admin" | jq -r '.access_token')
+
+# Decode JWT
+echo $TOKEN | cut -d'.' -f2 | base64 -d | jq '.'
+
+# Should show:
+{
+  "aud": "nextcloud",  # ✓ Intended for Nextcloud
+  "azp": "nextcloud-mcp-server",  # ✓ Requested by MCP Server
+  "iss": "http://localhost:8888/realms/nextcloud-mcp",
+  "scope": "openid email profile offline_access",
+  ...
+}
+```
+
+### 2. Test with Nextcloud API
+
+```bash
+# Token should be accepted
+curl -H "Authorization: Bearer $TOKEN" \
+  "http://localhost:8080/ocs/v2.php/cloud/capabilities"
+
+# Should return HTTP 200 OK
+```
+
+### 3. Test Audience Rejection
+
+```bash
+# Get token from different client (without audience mappers)
+TOKEN_WRONG=$(curl -X POST "http://localhost:8888/realms/nextcloud-mcp/protocol/openid-connect/token" \
+  -d "grant_type=password" \
+  -d "client_id=test-client-b" \
+  -d "client_secret=test-secret-b" \
+  -d "username=admin" \
+  -d "password=admin" | jq -r '.access_token')
+
+# This token has NO audience claim - should be rejected by MCP server
+# (But accepted by Nextcloud user_oidc which validates at realm level)
+```
+
+## Token Flow Example
+
+### Successful Request (Background Job)
+
+```
+1. User authorizes MCP Client via OAuth
+   └─ MCP Server gets refresh token (stored encrypted)
+
+2. Background worker needs to sync data
+   └─ MCP Server refreshes access token from Keycloak
+   └─ Token issued with aud: "nextcloud", azp: "nextcloud-mcp-server"
+
+3. MCP Server → Nextcloud API (with token)
+   └─ user_oidc validates via userinfo endpoint ✓
+   └─ Nextcloud identifies:
+       - Token intended for Nextcloud (aud: "nextcloud")
+       - Request from MCP Server (azp: "nextcloud-mcp-server")
+       - On behalf of user (sub: "user-id")
+
+4. Success! MCP Server can act on behalf of user in background.
+```
+
+### Rejected Request
+
+```
+1. Attacker gets token for different client
+   └─ Token has aud: "other-service"
+
+2. Attacker → Nextcloud API (with wrong token)
+   └─ user_oidc validates via userinfo endpoint
+   └─ Token validation fails (invalid/expired/wrong realm)
+   └─ HTTP 401 Unauthorized
+
+3. Request blocked - token not valid for this realm/service
+```
+
+## OAuth Flows and User Consent
+
+### When Does the User Grant Consent?
+
+User consent happens during the **Authorization Code Flow** (production OAuth):
+
+```
+1. User clicks "Connect" in MCP Client (e.g., Claude Desktop)
+2. MCP Client initiates OAuth flow by opening browser to Keycloak:
+   https://keycloak/realms/nextcloud-mcp/protocol/openid-connect/auth?
+     client_id=nextcloud-mcp-server&
+     redirect_uri=<mcp-client-redirect-uri>&
+     response_type=code&
+     scope=openid profile email offline_access
+
+3. Keycloak shows login screen (if not logged in)
+4. **Keycloak shows consent screen:**
+   "Nextcloud MCP Server wants to access your Nextcloud data on your behalf"
+   Requested permissions:
+   - Access your profile (openid, profile, email)
+   - Offline access (background operations with refresh tokens)
+
+5. User clicks "Allow" → grants consent
+6. Keycloak redirects back to MCP Client with authorization code
+7. MCP Client exchanges code for tokens (receives access + refresh tokens)
+8. MCP Client shares tokens with MCP Server via MCP protocol
+9. MCP Server stores refresh token encrypted for background operations
+```
+
+**Key Architecture Notes:**
+- **MCP Server is a protected resource** (requires OAuth to access)
+- **MCP Client** (Claude Desktop) is the OAuth client that initiates the flow
+- **MCP Client handles the redirect** and token exchange with Keycloak
+- **MCP Client shares refresh token** with MCP Server so it can act on behalf of user in background
+
+**Key Points:**
+- ✅ **Explicit user consent** before any access
+- ✅ **Scopes displayed** so user knows what's being requested
+- ✅ **Offline access** must be explicitly granted (for background jobs)
+- ✅ **Revocable** - user can revoke consent in Keycloak at any time
+
+### Grant Types
+
+Our architecture supports multiple OAuth grant types:
+
+**1. Authorization Code + PKCE (Production)**
+```
+Use case: Interactive login from MCP clients
+Consent: Yes - explicit user authorization
+Tokens: Access token + Refresh token (if offline_access granted)
+Security: PKCE prevents authorization code interception
+```
+
+**2. Password Grant (Testing Only)**
+```
+Use case: Integration testing with docker-compose
+Consent: No - username/password provided directly
+Tokens: Access token + Refresh token
+Security: NOT for production - exposes user credentials
+```
+
+**3. Refresh Token Grant (Background Jobs)**
+```
+Use case: MCP Server refreshing expired access tokens
+Consent: No new consent - uses previously granted refresh token
+Tokens: New access token (refresh token may rotate)
+Security: Refresh tokens stored encrypted, rotated on use
+```
+
+## Authentication Strategies for Background Jobs
+
+### Current Approach: Offline Access with Refresh Tokens (Tier 1)
+
+The MCP server currently uses **offline_access** scope to enable background operations:
+
+**How it works:**
+1. User grants `offline_access` scope during OAuth consent
+2. MCP Client receives refresh token from Keycloak
+3. MCP Client shares refresh token with MCP Server via MCP protocol
+4. MCP Server stores refresh token encrypted (see ADR-002)
+5. Background jobs exchange refresh token for fresh access tokens as needed
+
+**Benefits:**
+- ✅ Works today with Keycloak and all OIDC providers
+- ✅ Standard OAuth pattern (RFC 6749)
+- ✅ Explicit user consent to `offline_access` scope
+- ✅ MCP Server can act on behalf of user in background
+
+**Limitations:**
+- ⚠️ Requires secure token storage on MCP Server
+- ⚠️ MCP Client must trust MCP Server with refresh token
+- ⚠️ Weak audit trail - API requests appear to come from user directly
+- ⚠️ No visibility that MCP Server is the actual actor
+
+### Future Enhancement: Token Exchange with Delegation (Tier 2)
+
+**RFC 8693 Delegation** would provide better audit trail and security:
+
+**How it would work:**
+1. User grants `may_act:nextcloud-mcp-server` scope during authentication
+2. Subject token includes: `{ "may_act": { "client": "nextcloud-mcp-server" } }`
+3. MCP Server has its own service account token (actor_token)
+4. Background job requests token exchange:
+   - `subject_token` (user's token with may_act claim)
+   - `actor_token` (mcp-server's service token)
+5. Keycloak validates actor matches may_act claim
+6. Returns delegated token: `{ "sub": "user", "act": "nextcloud-mcp-server" }`
+
+**Benefits:**
+- ✅ Better audit trail - Nextcloud APIs see both user and actor
+- ✅ No token storage needed (tokens generated on-demand)
+- ✅ Fine-grained permissions via `may_act` claim
+- ✅ User explicitly consents to MCP Server acting on their behalf
+- ✅ RFC 8693 compliant
+
+**Current Status:**
+- ❌ **NOT implemented in Keycloak yet** ([Issue #38279](https://github.com/keycloak/keycloak/issues/38279))
+- ❌ Would require custom implementation or waiting for upstream
+- 📝 Proposal includes `act` claim and `may_act` consent mechanism
+
+**Why Not Available:**
+- Keycloak supports **impersonation** (changes `sub` claim), but not **delegation** (`act` claim)
+- Impersonation has poor audit trail (actor invisible)
+- Delegation proposal is open but not implemented yet
+
+**Reference:** See `docs/ADR-002-vector-sync-authentication.md` for detailed comparison of authentication tiers.
+
+## Security Benefits
+
+1. **Intent Validation**: Tokens explicitly declare Nextcloud as the intended recipient via `aud` claim
+2. **Requester Identification**: The `azp` claim identifies MCP Server as the requester
+3. **User Context**: The `sub` claim preserves user identity for audit and authorization
+4. **Background Jobs**: Refresh tokens enable MCP Server to act on behalf of users without admin credentials
+5. **OAuth Standards**: Follows RFC 8707 (Resource Indicators) and RFC 6749 (OAuth 2.0)
+
+**Current Limitations:**
+- API requests from background jobs appear to come from user directly (no `act` claim yet)
+- See "Authentication Strategies for Background Jobs" section for future delegation support
+
+## Token Claims
+
+### Key Claims
+
+- **`aud: "nextcloud"`** - Audience: Token intended for Nextcloud APIs
+- **`azp: "nextcloud-mcp-server"`** - Authorized Party: MCP Server requested the token
+- **`sub: "user-id"`** - Subject: User on whose behalf the request is made
+- **`scope: "openid profile email offline_access"`** - Requested scopes including offline access for background jobs
+
+### Client Naming
+
+The Keycloak client is named `nextcloud-mcp-server` to clarify:
+- **MCP Server** uses this client to get tokens for Nextcloud
+- **MCP Clients** (like Claude Desktop) connect to MCP Server via separate OAuth flows
+- **Not** named "mcp-client" to avoid confusion about which component is the client
+
+## Troubleshooting
+
+### Token Has No Audience
+
+**Symptom**: `"aud": null` in decoded JWT
+
+**Cause**: Protocol mappers not configured
+
+**Solution**: Add audience mappers via Keycloak Admin API (see Configuration section)
+
+### MCP Server Rejects Token
+
+**Symptom**: HTTP 401 with "JWT validation failed"
+
+**Cause**: Token audience doesn't match expected value
+
+**Solution**:
+1. Check token has correct `aud` claim
+2. Verify MCP server expects correct audience value in code
+3. Check logs for specific JWT validation error
+
+### Nextcloud Rejects Token
+
+**Symptom**: HTTP 401 from Nextcloud API
+
+**Cause**: User not provisioned or token invalid
+
+**Solution**:
+1. Check user_oidc provider is configured: `php occ user_oidc:provider keycloak`
+2. Check bearer validation enabled: `--check-bearer=1`
+3. Test token with userinfo endpoint: `curl -H "Authorization: Bearer $TOKEN" http://keycloak/realms/.../userinfo`
+
+## Related Documentation
+
+- **Multi-client validation**: `docs/keycloak-multi-client-validation.md`
+- **ADR-002**: `docs/ADR-002-vector-sync-authentication.md`
+- **OAuth setup**: `docs/oauth-setup.md`
+- **Keycloak integration**: `docs/keycloak-integration.md` (if created)
+
+## References
+
+- [RFC 8707 - Resource Indicators for OAuth 2.0](https://datatracker.ietf.org/doc/html/rfc8707)
+- [OIDC Core - ID Token aud claim](https://openid.net/specs/openid-connect-core-1_0.html#IDToken)
+- [Keycloak Audience Protocol Mappers](https://www.keycloak.org/docs/latest/server_admin/#_audience)
diff --git a/keycloak/realm-export.json b/keycloak/realm-export.json
new file mode 100644
index 0000000..2773565
--- /dev/null
+++ b/keycloak/realm-export.json
@@ -0,0 +1,327 @@
+{
+  "id": "nextcloud-mcp",
+  "realm": "nextcloud-mcp",
+  "notBefore": 0,
+  "defaultSignatureAlgorithm": "RS256",
+  "revokeRefreshToken": false,
+  "refreshTokenMaxReuse": 0,
+  "accessTokenLifespan": 300,
+  "accessTokenLifespanForImplicitFlow": 900,
+  "ssoSessionIdleTimeout": 1800,
+  "ssoSessionMaxLifespan": 36000,
+  "offlineSessionIdleTimeout": 2592000,
+  "offlineSessionMaxLifespanEnabled": false,
+  "offlineSessionMaxLifespan": 5184000,
+  "accessCodeLifespan": 60,
+  "accessCodeLifespanUserAction": 300,
+  "accessCodeLifespanLogin": 1800,
+  "enabled": true,
+  "sslRequired": "external",
+  "registrationAllowed": false,
+  "loginWithEmailAllowed": true,
+  "duplicateEmailsAllowed": false,
+  "resetPasswordAllowed": false,
+  "editUsernameAllowed": false,
+  "bruteForceProtected": false,
+  "roles": {
+    "realm": [
+      {
+        "name": "offline_access",
+        "description": "${role_offline-access}",
+        "composite": false,
+        "clientRole": false
+      },
+      {
+        "name": "uma_authorization",
+        "description": "${role_uma_authorization}",
+        "composite": false,
+        "clientRole": false
+      },
+      {
+        "name": "default-roles-nextcloud-mcp",
+        "description": "${role_default-roles}",
+        "composite": true,
+        "composites": {
+          "realm": ["offline_access", "uma_authorization"]
+        },
+        "clientRole": false
+      }
+    ]
+  },
+  "users": [
+    {
+      "username": "admin",
+      "enabled": true,
+      "email": "admin@example.com",
+      "emailVerified": true,
+      "firstName": "Admin",
+      "lastName": "User",
+      "credentials": [
+        {
+          "type": "password",
+          "value": "admin",
+          "temporary": false
+        }
+      ],
+      "realmRoles": ["default-roles-nextcloud-mcp", "offline_access"],
+      "attributes": {
+        "quota": ["1073741824"]
+      }
+    }
+  ],
+  "clients": [
+    {
+      "clientId": "nextcloud",
+      "name": "Nextcloud Resource Server",
+      "description": "Resource server for Nextcloud APIs - used by user_oidc app for bearer token validation",
+      "enabled": true,
+      "clientAuthenticatorType": "client-secret",
+      "secret": "nextcloud-secret-change-in-production",
+      "redirectUris": [],
+      "webOrigins": [],
+      "bearerOnly": true,
+      "consentRequired": false,
+      "standardFlowEnabled": false,
+      "implicitFlowEnabled": false,
+      "directAccessGrantsEnabled": false,
+      "serviceAccountsEnabled": false,
+      "publicClient": false,
+      "protocol": "openid-connect",
+      "attributes": {
+        "display.on.consent.screen": "false"
+      },
+      "fullScopeAllowed": true,
+      "nodeReRegistrationTimeout": -1
+    },
+    {
+      "clientId": "nextcloud-mcp-server",
+      "name": "Nextcloud MCP Server",
+      "enabled": true,
+      "clientAuthenticatorType": "client-secret",
+      "secret": "mcp-secret-change-in-production",
+      "redirectUris": [
+        "http://localhost:*",
+        "http://127.0.0.1:*",
+        "http://localhost:*/callback",
+        "http://127.0.0.1:*/callback"
+      ],
+      "webOrigins": ["+"],
+      "bearerOnly": false,
+      "consentRequired": false,
+      "standardFlowEnabled": true,
+      "implicitFlowEnabled": false,
+      "directAccessGrantsEnabled": true,
+      "serviceAccountsEnabled": false,
+      "publicClient": false,
+      "frontchannelLogout": false,
+      "protocol": "openid-connect",
+      "attributes": {
+        "pkce.code.challenge.method": "S256",
+        "use.refresh.tokens": "true",
+        "backchannel.logout.session.required": "true",
+        "backchannel.logout.url": "http://app:80/index.php/apps/user_oidc/backchannel-logout/keycloak",
+        "oauth2.device.authorization.grant.enabled": "false",
+        "oidc.ciba.grant.enabled": "false",
+        "client_credentials.use_refresh_token": "false",
+        "display.on.consent.screen": "false"
+      },
+      "fullScopeAllowed": true,
+      "nodeReRegistrationTimeout": -1,
+      "protocolMappers": [
+        {
+          "name": "audience-nextcloud",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-audience-mapper",
+          "consentRequired": false,
+          "config": {
+            "included.custom.audience": "nextcloud",
+            "access.token.claim": "true",
+            "id.token.claim": "false"
+          }
+        },
+        {
+          "name": "full name",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-full-name-mapper",
+          "consentRequired": false,
+          "config": {
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "userinfo.token.claim": "true"
+          }
+        },
+        {
+          "name": "email",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-property-mapper",
+          "consentRequired": false,
+          "config": {
+            "userinfo.token.claim": "true",
+            "user.attribute": "email",
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "claim.name": "email",
+            "jsonType.label": "String"
+          }
+        },
+        {
+          "name": "preferred_username",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-property-mapper",
+          "consentRequired": false,
+          "config": {
+            "userinfo.token.claim": "true",
+            "user.attribute": "username",
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "claim.name": "preferred_username",
+            "jsonType.label": "String"
+          }
+        },
+        {
+          "name": "quota",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-attribute-mapper",
+          "consentRequired": false,
+          "config": {
+            "userinfo.token.claim": "true",
+            "user.attribute": "quota",
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "claim.name": "quota",
+            "jsonType.label": "String"
+          }
+        }
+      ],
+      "defaultClientScopes": ["web-origins", "profile", "roles", "email"],
+      "optionalClientScopes": ["address", "phone", "offline_access", "microprofile-jwt"]
+    }
+  ],
+  "clientScopes": [
+    {
+      "name": "offline_access",
+      "description": "OpenID Connect built-in scope: offline_access",
+      "protocol": "openid-connect",
+      "attributes": {
+        "consent.screen.text": "${offlineAccessScopeConsentText}",
+        "display.on.consent.screen": "true"
+      }
+    },
+    {
+      "name": "profile",
+      "description": "OpenID Connect built-in scope: profile",
+      "protocol": "openid-connect",
+      "attributes": {
+        "include.in.token.scope": "true",
+        "display.on.consent.screen": "true"
+      },
+      "protocolMappers": [
+        {
+          "name": "full name",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-full-name-mapper",
+          "consentRequired": false,
+          "config": {
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "userinfo.token.claim": "true"
+          }
+        }
+      ]
+    },
+    {
+      "name": "email",
+      "description": "OpenID Connect built-in scope: email",
+      "protocol": "openid-connect",
+      "attributes": {
+        "include.in.token.scope": "true",
+        "display.on.consent.screen": "true"
+      },
+      "protocolMappers": [
+        {
+          "name": "email",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-property-mapper",
+          "consentRequired": false,
+          "config": {
+            "userinfo.token.claim": "true",
+            "user.attribute": "email",
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "claim.name": "email",
+            "jsonType.label": "String"
+          }
+        },
+        {
+          "name": "email verified",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-property-mapper",
+          "consentRequired": false,
+          "config": {
+            "userinfo.token.claim": "true",
+            "user.attribute": "emailVerified",
+            "id.token.claim": "true",
+            "access.token.claim": "true",
+            "claim.name": "email_verified",
+            "jsonType.label": "boolean"
+          }
+        }
+      ]
+    },
+    {
+      "name": "roles",
+      "description": "OpenID Connect scope for add user roles to the access token",
+      "protocol": "openid-connect",
+      "attributes": {
+        "include.in.token.scope": "false",
+        "display.on.consent.screen": "true"
+      },
+      "protocolMappers": [
+        {
+          "name": "realm roles",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-realm-role-mapper",
+          "consentRequired": false,
+          "config": {
+            "user.attribute": "foo",
+            "access.token.claim": "true",
+            "claim.name": "realm_access.roles",
+            "jsonType.label": "String",
+            "multivalued": "true"
+          }
+        },
+        {
+          "name": "client roles",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-usermodel-client-role-mapper",
+          "consentRequired": false,
+          "config": {
+            "user.attribute": "foo",
+            "access.token.claim": "true",
+            "claim.name": "resource_access.${client_id}.roles",
+            "jsonType.label": "String",
+            "multivalued": "true"
+          }
+        }
+      ]
+    },
+    {
+      "name": "web-origins",
+      "description": "OpenID Connect scope for add allowed web origins to the access token",
+      "protocol": "openid-connect",
+      "attributes": {
+        "include.in.token.scope": "false",
+        "display.on.consent.screen": "false"
+      },
+      "protocolMappers": [
+        {
+          "name": "allowed web origins",
+          "protocol": "openid-connect",
+          "protocolMapper": "oidc-allowed-origins-mapper",
+          "consentRequired": false,
+          "config": {}
+        }
+      ]
+    }
+  ]
+}
diff --git a/scripts/test_separate_clients.sh b/scripts/test_separate_clients.sh
new file mode 100755
index 0000000..44b67fb
--- /dev/null
+++ b/scripts/test_separate_clients.sh
@@ -0,0 +1,90 @@
+#!/bin/bash
+set -e
+
+echo "=== Testing Separate Clients Architecture ==="
+echo ""
+
+# Check both clients exist in Keycloak
+echo "1. Verifying Keycloak clients..."
+docker compose exec -T app curl -s http://keycloak:8080/realms/nextcloud-mcp/.well-known/openid-configuration > /dev/null && echo "✓ Keycloak realm available"
+
+# Check user_oidc provider configuration
+echo ""
+echo "2. Checking user_oidc provider..."
+PROVIDER_INFO=$(docker compose exec -T app php occ user_oidc:provider keycloak)
+echo "$PROVIDER_INFO" | grep -q "nextcloud" && echo "✓ user_oidc configured with 'nextcloud' client"
+
+# Get token from nextcloud-mcp-server client
+echo ""
+echo "3. Getting token from 'nextcloud-mcp-server' client..."
+TOKEN=$(curl -s -X POST "http://localhost:8888/realms/nextcloud-mcp/protocol/openid-connect/token" \
+  -d "grant_type=password" \
+  -d "client_id=nextcloud-mcp-server" \
+  -d "client_secret=mcp-secret-change-in-production" \
+  -d "username=admin" \
+  -d "password=admin" \
+  -d "scope=openid profile email offline_access" | jq -r '.access_token')
+
+if [ "$TOKEN" = "null" ] || [ -z "$TOKEN" ]; then
+    echo "✗ Failed to get token"
+    exit 1
+fi
+
+echo "✓ Got token from nextcloud-mcp-server client"
+
+# Check token claims
+echo ""
+echo "4. Inspecting token claims..."
+CLAIMS=$(echo "$TOKEN" | cut -d'.' -f2 | base64 -d 2>/dev/null | jq '{aud, azp, iss, preferred_username}')
+echo "$CLAIMS"
+
+AUD=$(echo "$CLAIMS" | jq -r '.aud')
+AZP=$(echo "$CLAIMS" | jq -r '.azp')
+
+echo ""
+echo "Architecture validation:"
+if [ "$AUD" = "nextcloud" ]; then
+    echo "  ✓ aud='nextcloud' - Token intended for Nextcloud resource server"
+else
+    echo "  ✗ FAILED: aud='$AUD', expected 'nextcloud'"
+    exit 1
+fi
+
+if [ "$AZP" = "nextcloud-mcp-server" ]; then
+    echo "  ✓ azp='nextcloud-mcp-server' - Token requested by MCP Server client"
+else
+    echo "  ✗ FAILED: azp='$AZP', expected 'nextcloud-mcp-server'"
+    exit 1
+fi
+
+# Test with Nextcloud API
+echo ""
+echo "5. Testing token with Nextcloud API..."
+HTTP_CODE=$(curl -s -w "%{http_code}" -o /tmp/nc_response.json \
+    -H "Authorization: Bearer $TOKEN" \
+    "http://localhost:8080/ocs/v2.php/cloud/capabilities?format=json")
+
+echo "HTTP Status: $HTTP_CODE"
+
+if [ "$HTTP_CODE" = "200" ]; then
+    echo "✓ Token validated successfully!"
+    echo ""
+    echo "===================================================================="
+    echo "SUCCESS: Separate Clients Architecture Working!"
+    echo "===================================================================="
+    echo ""
+    echo "Summary:"
+    echo "  - MCP Server client: 'nextcloud-mcp-server' (requests tokens)"
+    echo "  - Resource server: 'nextcloud' (validates tokens via user_oidc)"
+    echo "  - Token audience: 'nextcloud' (proper resource targeting)"
+    echo "  - Token azp: 'nextcloud-mcp-server' (identifies requester)"
+    echo ""
+    echo "This architecture supports:"
+    echo "  - Future multi-resource tokens: aud=['nextcloud', 'other-service']"
+    echo "  - Clear separation of OAuth client vs resource server"
+    echo "  - RFC 8707 Resource Indicators compliance"
+else
+    echo "✗ Token validation failed"
+    cat /tmp/nc_response.json
+    exit 1
+fi