diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index bb4954579..39c418f68 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -212,7 +212,11 @@ jobs:
               run: |
                   set -euo pipefail
 
-                  required_client_id="$EXPECTED_CLIENT_ID"
+                  configured_expected_client_id="${EXPECTED_CLIENT_ID:-}"
+                  if [ -z "$configured_expected_client_id" ]; then
+                    echo "::error::Missing required secret WEBAPP_EXPECTED_CLIENT_ID"
+                    exit 1
+                  fi
                   base_url=$(node -e 'const u = new URL(process.env.WEBHOOK_URL); console.log(`${u.protocol}//${u.host}`)')
                   auth_url="${base_url}/api/auth/discord"
                   auth_config_url="${base_url}/api/health/auth-config"
@@ -248,20 +252,21 @@ jobs:
                     '
                   )"
 
-                  expected_client_id="$(echo "$expected_values" | sed -n '1p')"
+                  auth_config_client_id="$(echo "$expected_values" | sed -n '1p')"
                   expected_redirect_uri="$(echo "$expected_values" | sed -n '2p')"
 
-                  if [ -z "$expected_client_id" ] || [ -z "$expected_redirect_uri" ]; then
+                  if [ -z "$auth_config_client_id" ] || [ -z "$expected_redirect_uri" ]; then
                     echo "::error::Unable to derive OAuth expectations from auth-config payload"
                     exit 1
                   fi
 
-                  if [ "$expected_client_id" != "$required_client_id" ]; then
-                    echo "::error::Auth-config client_id does not match WEBAPP_EXPECTED_CLIENT_ID"
-                    echo "::error::expected=$required_client_id actual=$expected_client_id"
+                  if [ "$auth_config_client_id" != "$configured_expected_client_id" ]; then
+                    echo "::error::Auth-config client_id (${auth_config_client_id}) does not match WEBAPP_EXPECTED_CLIENT_ID secret"
                     exit 1
                   fi
 
+                  expected_client_id="$configured_expected_client_id"
+
                   echo "==> Running OAuth redirect contract smoke check: $auth_url"
 
                   for attempt in $(seq 1 18); do
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f968828b0..d41c7fbd8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -58,6 +58,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - GitGuardian incident hardening: removed hardcoded compose PostgreSQL password
   fallbacks, enforced secret-managed expected client-id checks in deploy OAuth
   smoke validation, and replaced secret-like literals in test/example fixtures
+- Deploy workflow OAuth smoke now fails fast when
+  `WEBAPP_EXPECTED_CLIENT_ID` is missing and reports explicit auth-config
+  client-id mismatches.
 - Bundle-size CI workflow now exports `YOUTUBE_DL_SKIP_DOWNLOAD=true` (with
   workflow token) so `youtube-dl-exec` postinstall no longer fails on anonymous
   GitHub API rate limits during `npm ci`
diff --git a/README.md b/README.md
index 01e88ec54..49738365a 100644
--- a/README.md
+++ b/README.md
@@ -349,9 +349,9 @@ See `.env.example` for all available options. Key variables:
 | `REDIS_HOST` | No | Redis host (default: localhost) |
 | `WEBAPP_ENABLED` | No | Enable web dashboard (default: false) |
 | `WEBAPP_SESSION_SECRET` | No | Session encryption key |
-| `WEBAPP_REDIRECT_URI` | No | Explicit Discord OAuth callback URL (must match Discord app settings and deploy smoke contract); fallback callback source when `WEBAPP_BACKEND_URL` is unset |
-| `WEBAPP_EXPECTED_CLIENT_ID` | No | Expected Discord app client id for `/api/health/auth-config` mismatch detection when explicitly set |
-| `WEBAPP_BACKEND_URL` | No | Public backend/API origin used as canonical host for backend links and bot Last.fm connect links (must be an absolute HTTP(S) URL; recommended production canonical: `https://lucky-api.lucassantana.tech`) |
+| `WEBAPP_REDIRECT_URI` | No | Explicit Discord OAuth callback URL (must match Discord app settings and deploy smoke contract) |
+| `WEBAPP_EXPECTED_CLIENT_ID` | No | Expected Discord app client id for `/api/health/auth-config` mismatch detection when explicitly set (recommended via deployment secret) |
+| `WEBAPP_BACKEND_URL` | No | Public backend/API origin used for backend links and bot Last.fm connect links (must be an absolute HTTP(S) URL; recommended: `https://lucky-api.lucassantana.tech`) |
 | `CLIENT_SECRET` | No | Discord OAuth secret (for dashboard) |
 | `SENTRY_DSN` | No | Error tracking |