diff --git a/api/oauth.py b/api/oauth.py
index b9f6495b..13d9a693 100644
--- a/api/oauth.py
+++ b/api/oauth.py
@@ -218,6 +218,23 @@ def _now_iso() -> str:
     return datetime.now(timezone.utc).isoformat().replace("+00:00", "Z")
 
 
+def _invalidate_provider_state_caches(provider: str) -> None:
+    """Invalidate caches derived from provider credential state."""
+    try:
+        from api.config import invalidate_credential_pool_cache
+
+        invalidate_credential_pool_cache(provider)
+    except Exception:
+        logger.debug("Failed to invalidate %s credential cache", provider, exc_info=True)
+
+    try:
+        from api.providers import invalidate_providers_cache
+
+        invalidate_providers_cache()
+    except Exception:
+        logger.debug("Failed to invalidate providers cache after %s credential change", provider, exc_info=True)
+
+
 def _persist_codex_credentials(hermes_home: Path, token_data: dict[str, Any]) -> Path:
     """Persist Codex OAuth credentials to active-profile auth.json."""
     access_token = str(token_data.get("access_token") or "").strip()
@@ -277,12 +294,7 @@ def _persist_codex_credentials(hermes_home: Path, token_data: dict[str, Any]) ->
     auth["updated_at"] = now
     path = _write_auth_json(auth, auth_path)
 
-    try:
-        from api.config import invalidate_credential_pool_cache
-
-        invalidate_credential_pool_cache("openai-codex")
-    except Exception:
-        logger.debug("Failed to invalidate openai-codex credential cache", exc_info=True)
+    _invalidate_provider_state_caches("openai-codex")
 
     return path
 
@@ -389,12 +401,7 @@ def _link_anthropic_credentials(hermes_home: Path) -> None:
     })
     auth["updated_at"] = now
     _write_auth_json(auth, auth_path)
-
-    try:
-        from api.config import invalidate_credential_pool_cache
-        invalidate_credential_pool_cache("anthropic")
-    except Exception:
-        logger.debug("Failed to invalidate anthropic credential cache", exc_info=True)
+    _invalidate_provider_state_caches("anthropic")
 
 
 def _anthropic_public_start_payload(flow_id: str, flow: dict[str, Any]) -> dict[str, Any]:
@@ -515,11 +522,7 @@ def _remove_anthropic_link_marker(hermes_home: Path) -> None:
         pool.pop("anthropic", None)
     auth["updated_at"] = _now_iso()
     _write_auth_json(auth, auth_path)
-    try:
-        from api.config import invalidate_credential_pool_cache
-        invalidate_credential_pool_cache("anthropic")
-    except Exception:
-        logger.debug("Failed to invalidate anthropic credential cache", exc_info=True)
+    _invalidate_provider_state_caches("anthropic")
 
 
 # ── Codex protocol ──────────────────────────────────────────────────────────
diff --git a/api/providers.py b/api/providers.py
index fb42b82b..98bb2960 100644
--- a/api/providers.py
+++ b/api/providers.py
@@ -1025,6 +1025,9 @@ def _get_cached_providers(cache_key: tuple[Any, ...]) -> dict[str, Any] | None:
 
 def _store_cached_providers(cache_key: tuple[Any, ...], payload: dict[str, Any]) -> dict[str, Any]:
     with _providers_cache_lock:
+        # Single-entry by design: /api/providers is cacheable only for the
+        # active profile/config snapshot, so clear older snapshots to avoid
+        # retaining unbounded provider metadata across profile switches.
         _providers_cache.clear()
         _providers_cache[cache_key] = (time.monotonic(), copy.deepcopy(payload))
     return payload
diff --git a/tests/test_provider_management.py b/tests/test_provider_management.py
index f51bacd6..013a8aad 100644
--- a/tests/test_provider_management.py
+++ b/tests/test_provider_management.py
@@ -170,6 +170,24 @@ class TestGetProviders:
             if hasattr(prov, "invalidate_providers_cache"):
                 prov.invalidate_providers_cache()
 
+    def test_oauth_credential_updates_invalidate_providers_cache(self, monkeypatch, tmp_path):
+        """OAuth credential updates should invalidate cached Providers responses (#6010)."""
+        from api import oauth
+        from api import providers as prov
+
+        invalidated_credentials = []
+        providers_invalidated = []
+        monkeypatch.setattr(config, "invalidate_credential_pool_cache", invalidated_credentials.append)
+        monkeypatch.setattr(prov, "invalidate_providers_cache", lambda: providers_invalidated.append(True))
+
+        oauth._persist_codex_credentials(
+            tmp_path,
+            {"access_token": "access-token", "refresh_token": "refresh-token"},
+        )
+
+        assert invalidated_credentials == ["openai-codex"]
+        assert providers_invalidated == [True]
+
     def test_returns_list_of_known_providers(self, monkeypatch, tmp_path):
         """GET /api/providers should return a list of all known providers."""
         _install_fake_hermes_cli(monkeypatch)