diff --git a/config/defaults/development.config.js b/config/defaults/development.config.js
index b05d7fccf..c5516cbb4 100644
--- a/config/defaults/development.config.js
+++ b/config/defaults/development.config.js
@@ -88,8 +88,8 @@ const config = {
     // `lib/helpers/redactUrl.js` (`redactPathSecrets` for PATH segments e.g.
     // `/api/auth/reset/:token`; `redactUrl` for query params e.g.
     // `?inviteToken=…`). Values are UNIONED with the built-in defaults there
-    // (['reset', 'verify', 'verify-email'] / ['inviteToken']), never
-    // replacing them.
+    // (['reset', 'verify', 'verify-email'] / ['inviteToken', 'code', 'state']),
+    // never replacing them.
     //
     // These two keys are intentionally OMITTED from this file: `deepMerge`
     // (config/index.js) replaces arrays wholesale rather than merging them,
diff --git a/lib/helpers/redactUrl.js b/lib/helpers/redactUrl.js
index d92dfd537..ff29d793e 100644
--- a/lib/helpers/redactUrl.js
+++ b/lib/helpers/redactUrl.js
@@ -13,7 +13,7 @@ import config from '../../config/index.js';
  * silently disabled (an absent key or an explicit empty array in config both
  * degrade to exactly these defaults, never to nothing).
  */
-const DEFAULT_SENSITIVE_QUERY_KEYS = ['inviteToken'];
+const DEFAULT_SENSITIVE_QUERY_KEYS = ['inviteToken', 'code', 'state'];
 const DEFAULT_SENSITIVE_PATH_MARKERS = ['reset', 'verify', 'verify-email'];
 
 /**
@@ -42,9 +42,12 @@ const sanitizeConfigList = (value, label) => {
  * Sensitive query-string parameters that must never reach the request log.
  *
  * `inviteToken` rides the query string of `POST /api/auth/signup?inviteToken=…`
- * (the Vue client puts it there, not in the body). The morgan log pattern logs
- * `:url`, so without redaction a live single-use invite token lands in prod logs
- * (and any log shipper / aggregator downstream). Redact it to `REDACTED`.
+ * (the Vue client puts it there, not in the body). `code` and `state` ride the
+ * query string of `GET /api/auth/:strategy/callback?code=…&state=…` (the OAuth
+ * provider redirects there with the one-time authorization code). The morgan
+ * log pattern logs `:url`, so without redaction a live single-use secret lands
+ * in prod logs (and any log shipper / aggregator downstream). Redact them to
+ * `REDACTED`.
  *
  * Union of `DEFAULT_SENSITIVE_QUERY_KEYS` and `config.log.sensitiveQueryKeys`:
  * a module/downstream project extends the set purely additively from its own
diff --git a/lib/helpers/tests/redactUrl.unit.tests.js b/lib/helpers/tests/redactUrl.unit.tests.js
index 434508866..85ecbc66c 100644
--- a/lib/helpers/tests/redactUrl.unit.tests.js
+++ b/lib/helpers/tests/redactUrl.unit.tests.js
@@ -71,6 +71,19 @@ describe('redactUrl', () => {
   test('exports inviteToken as a sensitive key', () => {
     expect(SENSITIVE_QUERY_KEYS).toContain('inviteToken');
   });
+
+  test('redacts an OAuth callback code and state, preserving the path', () => {
+    expect(redactUrl('/api/auth/google/callback?code=SECRET&state=xyz')).toBe('/api/auth/google/callback?code=REDACTED&state=REDACTED');
+  });
+
+  test('redacts an OAuth callback code among other query params, leaving the rest intact', () => {
+    expect(redactUrl('/api/auth/google/callback?state=xyz&scope=email&code=SECRET')).toBe('/api/auth/google/callback?state=REDACTED&scope=email&code=REDACTED');
+  });
+
+  test('exports code and state as sensitive keys', () => {
+    expect(SENSITIVE_QUERY_KEYS).toContain('code');
+    expect(SENSITIVE_QUERY_KEYS).toContain('state');
+  });
 });
 
 describe('redactPathSecrets', () => {
@@ -168,7 +181,7 @@ describe('redactUrl config sourcing (#3953)', () => {
       log: { sensitivePathMarkers: [], sensitiveQueryKeys: [] },
     });
     expect(mod.SENSITIVE_PATH_MARKERS).toEqual(['reset', 'verify', 'verify-email']);
-    expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken']);
+    expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken', 'code', 'state']);
     expect(mod.redactPathSecrets('/api/auth/reset/SECRETTOKEN')).toBe('/api/auth/reset/REDACTED');
     expect(mod.default('/x?inviteToken=secret')).toBe('/x?inviteToken=REDACTED');
   });
@@ -176,7 +189,7 @@ describe('redactUrl config sourcing (#3953)', () => {
   test('falls back to the built-in defaults when config.log is missing', async () => {
     const mod = await loadWithConfig({});
     expect(mod.SENSITIVE_PATH_MARKERS).toEqual(['reset', 'verify', 'verify-email']);
-    expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken']);
+    expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken', 'code', 'state']);
     expect(mod.redactPathSecrets('/api/auth/reset/SECRETTOKEN')).toBe('/api/auth/reset/REDACTED');
     expect(mod.default('/x?inviteToken=secret')).toBe('/x?inviteToken=REDACTED');
   });
@@ -184,7 +197,7 @@ describe('redactUrl config sourcing (#3953)', () => {
   test('falls back to the built-in defaults when config itself is undefined', async () => {
     const mod = await loadWithConfig(undefined);
     expect(mod.SENSITIVE_PATH_MARKERS).toEqual(['reset', 'verify', 'verify-email']);
-    expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken']);
+    expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken', 'code', 'state']);
   });
 
   /**
@@ -214,7 +227,7 @@ describe('redactUrl config sourcing (#3953)', () => {
       const mod = await loadWithConfig({
         log: { sensitiveQueryKeys: 'oops' },
       });
-      expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken']);
+      expect(mod.SENSITIVE_QUERY_KEYS).toEqual(['inviteToken', 'code', 'state']);
       expect(mod.default('/x?inviteToken=secret')).toBe('/x?inviteToken=REDACTED');
       expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining('log.sensitiveQueryKeys'));
     } finally {