diff --git a/Security-audit.md b/Security-audit.md
index 7a99bc8..b033238 100644
--- a/Security-audit.md
+++ b/Security-audit.md
@@ -54,13 +54,17 @@ The application should remain behind the production reverse proxy, with real DNS
 
 ### SA-002: Raw infrastructure errors are returned to clients
 
-**Severity:** High  
-**Evidence:** SMTP and Mastodon routes interpolate exception text into `503`/`502` responses. Setup and email-address routes also expose mail-delivery exception text.  
+**Severity:** High, remediated in current worktree
+**Evidence before remediation:** SMTP and Mastodon routes interpolated exception text into `503`/`502` responses. Setup and email-address routes also exposed mail-delivery exception text.
 **Impact:** Error responses can disclose SMTP hostnames, ports, TLS/library details, upstream response bodies, internal network information, or sensitive URL fragments.
 
-**Recommendation:** Log technical details server-side with a request/correlation ID and return a stable public message with a short reference ID. Redact credentials, authorization headers, reset tokens, OTP data, and secret-bearing URLs. Add tests asserting that representative exception text is absent from HTTP responses.
+**Current state:** The application assigns a request ID at middleware entry, returns it in `X-Request-ID`, logs technical exception summaries server-side after redacting authorization values, tokens, passwords, secrets, OTP/code values, and secret-bearing URL query values, and returns stable public messages with a reference ID. SMTP setup/admin/email errors and Mastodon registration/callback errors no longer expose raw exception text. Regression tests verify representative exception and secret text is absent from HTTP responses.
 
-**Priority:** High.
+**Residual impact:** Logging currently uses the application logger rather than a centralized protected sink. Request-ID trust, log retention, access control, and structured redaction should be reviewed in deployment.
+
+**Recommendation:** Keep public errors stable and reference-based, export redacted logs to a protected centralized system, define retention and access controls, and never log authorization headers or secret-bearing request data.
+
+**Priority:** Completed in code; centralized logging and operational controls remain.
 
 ### SA-003: First-run setup is unauthenticated and lacks application-level body limits
 
diff --git a/VIBE/CHAT_LOG.md b/VIBE/CHAT_LOG.md
index 17de7ae..f06e950 100644
--- a/VIBE/CHAT_LOG.md
+++ b/VIBE/CHAT_LOG.md
@@ -1,5 +1,11 @@
 # Chat Log
 
+### User
+For SA-002, log technical details server-side with a request/correlation ID, return a stable public message with a short reference ID, redact secrets, and test that exception text is absent from responses.
+
+### Assistant outcome
+Added request-ID middleware and stable public error references. SMTP, setup, email-verification, and Mastodon exception paths now log redacted technical summaries server-side without exposing raw exception text, credentials, authorization values, reset tokens, OTP data, or secret-bearing URL values. Added regression coverage and updated SA-002 documentation.
+
 ### User
 Remedy SA-001: Logout uses non-standard token transport.
 
diff --git a/VIBE/PROMPTS.md b/VIBE/PROMPTS.md
index 1f4c18b..dcb1339 100644
--- a/VIBE/PROMPTS.md
+++ b/VIBE/PROMPTS.md
@@ -201,6 +201,7 @@
 195. Perform a new security audit overwriting Security-audit.md with new and remaining issues.
 195. Update SA-012 and README for the implemented refresh-token lifecycle, revocation behavior, and refresh endpoint.
 196. Remedy SA-001: migrate logout from JSON token transport to the Authorization bearer header.
+197. Implement SA-002: replace raw infrastructure errors with redacted server-side logging, request IDs, and stable public reference messages.
 
 ## Future entries
 
diff --git a/backend/app/api/admin.py b/backend/app/api/admin.py
index a644309..a859f85 100644
--- a/backend/app/api/admin.py
+++ b/backend/app/api/admin.py
@@ -5,7 +5,7 @@ import json
 from datetime import datetime, timedelta, timezone
 from uuid import uuid4
 
-from fastapi import APIRouter, Depends, HTTPException
+from fastapi import APIRouter, Depends, HTTPException, Request
 from pydantic import BaseModel
 
 from backend.app.api.dependencies import require_admin
@@ -23,8 +23,11 @@ from backend.app.services.theme_service import THEMES, get_enabled_themes, save_
 from backend.app.services.secret_store import encrypt_secret
 from backend.app.core.config import settings
 from backend.app.services.audit_service import record_audit_event
+from backend.app.core.errors import public_error, redacted_error, request_id
+import logging
 
 router = APIRouter()
+logger = logging.getLogger(__name__)
 
 
 class AdminPluginUpdate(BaseModel):
@@ -112,7 +115,7 @@ def reset_user_otp(user_id: str, current_user: dict = Depends(require_admin)):
 
 
 @router.post('/users', status_code=201)
-def create_user(payload: AdminUserCreate, current_user: dict = Depends(require_admin)):
+def create_user(payload: AdminUserCreate, request: Request, current_user: dict = Depends(require_admin)):
     username = payload.username.strip()
     email = payload.email.strip()
     if not username or not email or len(payload.password) < 8:
@@ -142,7 +145,8 @@ def create_user(payload: AdminUserCreate, current_user: dict = Depends(require_a
         try:
             send_verification_email(row['email'], row['username'], verification_url)
         except Exception as error:
-            raise HTTPException(status_code=503, detail=f'User created but verification email could not be sent: {error}') from error
+            logger.error('User verification email failed request_id=%s error=%s', request_id(request), redacted_error(error))
+            raise HTTPException(status_code=503, detail=public_error(request, 'User created but verification email could not be sent.')) from error
             record_audit_event(current_user['id'], 'user_created', 'user', row['id'], details={'is_admin': bool(payload.is_admin)})
     return public_user(row)
 
@@ -188,7 +192,7 @@ def update_admin_smtp_settings(payload: AdminSmtpUpdate, current_user: dict = De
 
 
 @router.post('/smtp/test')
-def validate_admin_smtp(payload: AdminSmtpUpdate, current_user: dict = Depends(require_admin)):
+def validate_admin_smtp(payload: AdminSmtpUpdate, request: Request, current_user: dict = Depends(require_admin)):
     values = validate_smtp_values(payload, get_smtp_settings())
     now = datetime.now(timezone.utc)
     with get_connection() as conn:
@@ -209,7 +213,8 @@ def validate_admin_smtp(payload: AdminSmtpUpdate, current_user: dict = Depends(r
     try:
         send_test_email(current_user['email'], values)
     except Exception as error:
-        raise HTTPException(status_code=503, detail=f'SMTP validation failed: {error}') from error
+        logger.error('SMTP validation failed request_id=%s error=%s', request_id(request), redacted_error(error))
+        raise HTTPException(status_code=503, detail=public_error(request, 'SMTP validation failed.')) from error
     sends = int(rate.get('sends', 0)) + 1
     updated_rate = {'sends': sends, 'last_sent': now.isoformat()}
     if sends >= 5:
diff --git a/backend/app/api/mastodon.py b/backend/app/api/mastodon.py
index 9a1d772..28f0ec4 100644
--- a/backend/app/api/mastodon.py
+++ b/backend/app/api/mastodon.py
@@ -10,12 +10,15 @@ from starlette.requests import Request
 
 from backend.app.api.dependencies import get_current_user
 from backend.app.services.mastodon_oauth import finish_authorization, start_authorization
+from backend.app.core.errors import public_error, redacted_error, request_id
+import logging
 
 router = APIRouter()
+logger = logging.getLogger(__name__)
 
 
 @router.get('/oauth/start')
-def oauth_start(instance: str = 'mastodon.social', user: dict = Depends(get_current_user)):
+def oauth_start(request: Request, instance: str = 'mastodon.social', user: dict = Depends(get_current_user)):
     try:
         authorization_url = start_authorization(user['id'], instance)
     except HTTPError as error:
@@ -27,7 +30,8 @@ def oauth_start(instance: str = 'mastodon.social', user: dict = Depends(get_curr
             headers=headers,
         ) from error
     except Exception as error:
-        raise HTTPException(status_code=502, detail=f'Could not register with Mastodon: {error}') from error
+        logger.error('Mastodon registration failed request_id=%s error=%s', request_id(request), redacted_error(error))
+        raise HTTPException(status_code=502, detail=public_error(request, 'Could not register with Mastodon.')) from error
     return {'authorization_url': authorization_url}
 
 
@@ -38,5 +42,6 @@ def oauth_callback(request: Request, code: str | None = None, state: str | None
     try:
         finish_authorization(code, state)
     except Exception as callback_error:
-        return RedirectResponse(f'/profile?mastodon_error={quote(str(callback_error))}')
+        logger.error('Mastodon callback failed request_id=%s error=%s', request_id(request), redacted_error(callback_error))
+        return RedirectResponse(f'/profile?mastodon_error={quote(public_error(request, "Could not complete Mastodon authorization."))}')
     return RedirectResponse('/profile?mastodon=connected')
\ No newline at end of file
diff --git a/backend/app/api/setup.py b/backend/app/api/setup.py
index be00deb..664e5f3 100644
--- a/backend/app/api/setup.py
+++ b/backend/app/api/setup.py
@@ -5,14 +5,17 @@ from datetime import datetime, timedelta, timezone
 import json
 from uuid import uuid4
 
-from fastapi import APIRouter, HTTPException
+from fastapi import APIRouter, HTTPException, Request
 from pydantic import BaseModel
 
 from backend.app.core.config import settings
 from backend.app.database import get_connection, hash_password
 from backend.app.services.email_service import get_smtp_settings, save_smtp_settings, send_test_email
+from backend.app.core.errors import public_error, redacted_error, request_id
+import logging
 
 router = APIRouter()
+logger = logging.getLogger(__name__)
 
 
 class SetupRequest(BaseModel):
@@ -92,7 +95,7 @@ def save_configuration(payload: SetupRequest):
 
 
 @router.post('/test-mail')
-def test_mail(payload: TestMailRequest | None = None):
+def test_mail(request: Request, payload: TestMailRequest | None = None):
     if has_administrator():
         raise HTTPException(status_code=409, detail='LinkLog is already configured')
     pending = get_pending_setup()
@@ -119,7 +122,8 @@ def test_mail(payload: TestMailRequest | None = None):
     try:
         send_test_email(payload.email if payload and payload.email else pending['email'])
     except Exception as error:
-        raise HTTPException(status_code=503, detail=f'SMTP test mail could not be sent: {error}') from error
+        logger.error('SMTP test mail failed request_id=%s error=%s', request_id(request), redacted_error(error))
+        raise HTTPException(status_code=503, detail=public_error(request, 'SMTP test mail could not be sent.')) from error
 
     sends = int(rate.get('sends', 0)) + 1
     updated_rate = {'sends': sends, 'last_sent': now.isoformat()}
diff --git a/backend/app/api/user_config.py b/backend/app/api/user_config.py
index fd2f781..cbf7fa3 100644
--- a/backend/app/api/user_config.py
+++ b/backend/app/api/user_config.py
@@ -7,7 +7,7 @@ from io import BytesIO
 from datetime import datetime, timedelta, timezone
 from uuid import uuid4
 
-from fastapi import APIRouter, Depends, File, HTTPException, UploadFile
+from fastapi import APIRouter, Depends, File, HTTPException, Request, UploadFile
 from PIL import Image, UnidentifiedImageError
 from pydantic import BaseModel
 
@@ -20,8 +20,11 @@ from backend.app.services.email_service import send_verification_email, smtp_con
 from backend.app.core.config import settings
 from backend.app.services.secret_store import decrypt_secret, encrypt_secret
 from backend.app.services.audit_service import record_audit_event
+from backend.app.core.errors import public_error, redacted_error, request_id
+import logging
 
 router = APIRouter()
+logger = logging.getLogger(__name__)
 
 MAX_AVATAR_BYTES = 2 * 1024 * 1024
 MAX_AVATAR_PIXELS = 25_000_000
@@ -186,7 +189,7 @@ def get_additional_emails(user: dict = Depends(get_current_user)):
 
 
 @router.post('/emails', status_code=201)
-def add_additional_email(payload: AdditionalEmail, user: dict = Depends(get_current_user)):
+def add_additional_email(payload: AdditionalEmail, request: Request, user: dict = Depends(get_current_user)):
     email = payload.email.strip().lower()
     if email == user['email'].lower():
         raise HTTPException(status_code=409, detail='This is already the primary email address')
@@ -209,7 +212,8 @@ def add_additional_email(payload: AdditionalEmail, user: dict = Depends(get_curr
         try:
             send_verification_email(email_address, user['username'], verification_url)
         except Exception as error:
-            raise HTTPException(status_code=503, detail=f'Email address added but verification email could not be sent: {error}') from error
+            logger.error('Additional email verification failed request_id=%s error=%s', request_id(request), redacted_error(error))
+            raise HTTPException(status_code=503, detail=public_error(request, 'Email address added but verification email could not be sent.')) from error
         with get_connection() as conn:
             conn.execute(
                 '''INSERT INTO app_settings (name, value, updated_at) VALUES (?, ?, CURRENT_TIMESTAMP)
@@ -221,7 +225,7 @@ def add_additional_email(payload: AdditionalEmail, user: dict = Depends(get_curr
 
 
 @router.post('/emails/{address_id}/resend')
-def resend_additional_email(address_id: str, user: dict = Depends(get_current_user)):
+def resend_additional_email(address_id: str, request: Request, user: dict = Depends(get_current_user)):
     now = datetime.now(timezone.utc)
     setting_name = f'email_verify_rate:{address_id}'
     with get_connection() as conn:
@@ -245,7 +249,8 @@ def resend_additional_email(address_id: str, user: dict = Depends(get_current_us
     try:
         send_verification_email(email, user['username'], verification_url)
     except Exception as error:
-        raise HTTPException(status_code=503, detail=f'Verification email could not be sent: {error}') from error
+        logger.error('Verification email resend failed request_id=%s error=%s', request_id(request), redacted_error(error))
+        raise HTTPException(status_code=503, detail=public_error(request, 'Verification email could not be sent.')) from error
     sends = int(rate.get('sends', 0)) + 1
     updated = {'sends': sends, 'last_sent': now.isoformat()}
     if sends >= 5:
diff --git a/backend/app/core/errors.py b/backend/app/core/errors.py
new file mode 100644
index 0000000..e7dbc67
--- /dev/null
+++ b/backend/app/core/errors.py
@@ -0,0 +1,23 @@
+import re
+from uuid import uuid4
+
+from fastapi import Request
+
+
+SENSITIVE_PATTERN = re.compile(
+    r'(?i)(authorization\s*[:=]\s*bearer\s+[^\s,;]+|'
+    r'(?:token|password|secret|otp|code)(?:[_-](?:token|password|secret|code))?\s*[:=]\s*[^\s,;&]+|'
+    r'([?&](?:token|code|password|secret|otp)=[^&#\s]+))'
+)
+
+
+def request_id(request: Request) -> str:
+    return getattr(request.state, 'request_id', None) or str(uuid4())
+
+
+def redacted_error(error: Exception) -> str:
+    return SENSITIVE_PATTERN.sub('[REDACTED]', str(error))
+
+
+def public_error(request: Request, message: str) -> str:
+    return f'{message} Reference: {request_id(request)}'
\ No newline at end of file
diff --git a/backend/app/main.py b/backend/app/main.py
index 51e59ae..8bc5649 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -1,8 +1,9 @@
 ## Copyright © 2026 Olaf Kolkman
 ## SPDX-License-Identifier: GPL-3.0-or-later
 
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
 import logging
+from uuid import uuid4
 from fastapi.responses import HTMLResponse
 from fastapi.responses import RedirectResponse
 from fastapi.staticfiles import StaticFiles
@@ -24,6 +25,15 @@ from backend.app.services.link_service import get_public_profile, list_public_li
 logging.basicConfig(level=getattr(logging, settings.log_level, logging.INFO))
 
 app = FastAPI(title='LinkLog API', version=settings.version)
+
+
+@app.middleware('http')
+async def add_request_id(request: Request, call_next):
+    request.state.request_id = request.headers.get('X-Request-ID') or str(uuid4())
+    response = await call_next(request)
+    response.headers['X-Request-ID'] = request.state.request_id
+    return response
+
 app.mount('/static', StaticFiles(directory='frontend/static'), name='static')
 app.mount('/media', StaticFiles(directory=AVATARS_DIR), name='media')
 app.include_router(auth_router, prefix='/api/auth')
diff --git a/backend/tests/test_api.py b/backend/tests/test_api.py
index c9dab5d..66f7b62 100644
--- a/backend/tests/test_api.py
+++ b/backend/tests/test_api.py
@@ -227,7 +227,31 @@ def test_admin_reports_smtp_validation_errors():
             'smtp_use_tls': False,
         })
     assert failed_validation.status_code == 503
-    assert 'connection refused' in failed_validation.json()['detail']
+    assert failed_validation.json()['detail'].startswith('SMTP validation failed. Reference: ')
+    assert 'connection refused' not in failed_validation.json()['detail']
+    assert failed_validation.headers['X-Request-ID']
+
+
+def test_request_id_is_preserved_and_sensitive_error_text_is_not_returned():
+    headers = login_headers()
+    with get_connection() as conn:
+        conn.execute('DELETE FROM app_settings WHERE name = ?', ('admin_smtp_mail_rate',))
+        conn.commit()
+    with patch('backend.app.api.admin.send_test_email', side_effect=RuntimeError('password=super-secret token=abc123')):
+        response = client.post(
+            '/api/admin/smtp/test',
+            headers={**headers, 'X-Request-ID': 'audit-test-123'},
+            json={
+                'smtp_host': 'smtp.example.com',
+                'smtp_port': 2525,
+                'smtp_from': 'admin@example.com',
+            },
+        )
+    assert response.status_code == 503
+    assert response.headers['X-Request-ID'] == 'audit-test-123'
+    assert response.json()['detail'] == 'SMTP validation failed. Reference: audit-test-123'
+    assert 'super-secret' not in response.text
+    assert 'abc123' not in response.text
 
 
 def test_admin_can_add_list_and_remove_users():