diff --git a/acp_adapter/session.py b/acp_adapter/session.py
index 6f1e17a07f57..954971481160 100644
--- a/acp_adapter/session.py
+++ b/acp_adapter/session.py
@@ -634,6 +634,10 @@ def _make_agent(
 
         try:
             runtime = resolve_runtime_provider(requested=requested_provider or config_provider)
+            # Match gateway/CLI: pass credential_pool so long-lived ACP sessions
+            # can refresh OAuth (xAI returns 403 bad-credentials for stale tokens).
+            # Without the pool, idle Buzz ACP processes abort while Telegram/Desktop
+            # keep working on the same HERMES_HOME.
             kwargs.update(
                 {
                     "provider": runtime.get("provider"),
@@ -642,6 +646,7 @@ def _make_agent(
                     "api_key": runtime.get("api_key"),
                     "command": runtime.get("command"),
                     "args": list(runtime.get("args") or []),
+                    "credential_pool": runtime.get("credential_pool"),
                 }
             )
         except Exception:
diff --git a/agent/conversation_loop.py b/agent/conversation_loop.py
index a764501febab..97ae345a78ce 100644
--- a/agent/conversation_loop.py
+++ b/agent/conversation_loop.py
@@ -3271,13 +3271,19 @@ def _perform_api_call(next_api_kwargs):
                 if (
                     agent.api_mode == "codex_responses"
                     and agent.provider in {"openai-codex", "xai-oauth"}
-                    and status_code == 401
+                    # xAI often returns 403 bad-credentials for a stale access
+                    # token (not only 401). Refresh on both when the classifier
+                    # says auth (spending-limit 403 is billing and is excluded).
+                    and status_code in {401, 403}
+                    and classified.reason == FailoverReason.auth
                     and not _retry.codex_auth_retry_attempted
                 ):
                     _retry.codex_auth_retry_attempted = True
                     if agent._try_refresh_codex_client_credentials(force=True):
                         _label = "xAI OAuth" if agent.provider == "xai-oauth" else "Codex"
-                        agent._buffer_vprint(f"🔐 {_label} auth refreshed after 401. Retrying request...")
+                        agent._buffer_vprint(
+                            f"🔐 {_label} auth refreshed after {status_code}. Retrying request..."
+                        )
                         continue
                 if (
                     agent.api_mode == "chat_completions"
diff --git a/agent/error_classifier.py b/agent/error_classifier.py
index 33c2f5458560..dba9cae5d91e 100644
--- a/agent/error_classifier.py
+++ b/agent/error_classifier.py
@@ -968,9 +968,21 @@ def _classify_by_status(
                 should_rotate_credential=True,
                 should_fallback=True,
             )
+        # Default: auth without rotate — preserve historical behaviour for
+        # generic providers (see test_non_xai_403_generic_billing_code_remains_auth).
+        # OAuth providers that return 403 for stale access tokens (xAI
+        # ``bad-credentials``, etc.) need rotate/refresh like 401 so long-lived
+        # ACP sessions recover. Billing shapes above already returned.
+        _stale_oauth_403 = (
+            provider in {"xai-oauth", "openai-codex", "nous"}
+            or "bad-credentials" in error_msg
+            or "oauth2 access token could not be validated" in error_msg
+            or "wke=unauthenticated" in error_msg
+        )
         return result_fn(
             FailoverReason.auth,
             retryable=False,
+            should_rotate_credential=_stale_oauth_403,
             should_fallback=True,
         )
 
diff --git a/tests/acp/test_session.py b/tests/acp/test_session.py
index 199454b39dba..c58e7a215a85 100644
--- a/tests/acp/test_session.py
+++ b/tests/acp/test_session.py
@@ -130,6 +130,48 @@ def __init__(self, **kwargs):
 
 
 class TestWslCwdTranslation:
+    def test_make_agent_forwards_credential_pool_from_runtime(self, monkeypatch):
+        """ACP must wire the runtime credential pool like gateway/CLI.
+
+        Without the pool, long-lived ACP sessions cannot refresh stale
+        xAI OAuth tokens (403 bad-credentials) while Telegram keeps working.
+        """
+        captured = {}
+        fake_pool = object()
+
+        def fake_agent(**kwargs):
+            captured.update(kwargs)
+            return SimpleNamespace(
+                model=kwargs.get("model"),
+                session_cwd=None,
+                _print_fn=None,
+            )
+
+        monkeypatch.setattr(
+            "hermes_cli.config.load_config",
+            lambda: {"model": {"provider": "xai-oauth", "default": "grok-4.5"}},
+        )
+        monkeypatch.setattr(
+            "hermes_cli.runtime_provider.resolve_runtime_provider",
+            lambda requested=None, **kwargs: {
+                "provider": "xai-oauth",
+                "api_mode": "codex_responses",
+                "base_url": "https://api.x.ai/v1",
+                "api_key": "stale-token",
+                "command": None,
+                "args": [],
+                "credential_pool": fake_pool,
+            },
+        )
+        with patch("run_agent.AIAgent", side_effect=fake_agent):
+            agent = SessionManager(db=None)._make_agent(
+                session_id="sess-pool",
+                cwd="/tmp/work",
+            )
+
+        assert captured.get("credential_pool") is fake_pool
+        assert captured.get("provider") == "xai-oauth"
+
     def test_translate_acp_cwd_converts_windows_drive_path_when_wsl(self, monkeypatch):
         monkeypatch.setattr("hermes_constants._wsl_detected", True)