diff --git a/agent/copilot_acp_client.py b/agent/copilot_acp_client.py
index 421438964a..3df2f1477b 100644
--- a/agent/copilot_acp_client.py
+++ b/agent/copilot_acp_client.py
@@ -371,13 +371,16 @@ class CopilotACPClient:
         threading.Thread(target=_pump, args=(proc.stdout, lambda line: inbox.put(_decode(line))), daemon=True).start()
         threading.Thread(target=_pump, args=(proc.stderr, lambda line: stderr_tail.append(line.rstrip("\n"))), daemon=True).start()
         request_ids = iter(range(1, 1 << 62))
+        # One budget for the WHOLE session (initialize + session/new + any prompt), not per
+        # request: a hung CLI must not get 2x the caller's timeout on the foreground /model path.
+        session_deadline = time.monotonic() + timeout_seconds
 
         def _request(method: str, params: dict[str, Any], *, text_parts: list[str] | None = None,
                      reasoning_parts: list[str] | None = None) -> Any:
             request_id = next(request_ids)
             proc.stdin.write(json.dumps({"jsonrpc": "2.0", "id": request_id, "method": method, "params": params}) + "\n")
             proc.stdin.flush()
-            deadline = time.monotonic() + timeout_seconds
+            deadline = session_deadline
             while time.monotonic() < deadline and proc.poll() is None:
                 try:
                     msg = inbox.get(timeout=0.1)
diff --git a/hermes_cli/models.py b/hermes_cli/models.py
index 1179d9e783..a21c3be470 100644
--- a/hermes_cli/models.py
+++ b/hermes_cli/models.py
@@ -1235,20 +1235,23 @@ def _codex_catalog(normalized: str, force_refresh: bool) -> list[str]:
     return get_codex_model_ids(access_token=access_token)
 
 
-_COPILOT_ACP_SESSION_MEMO_TTL = 300.0  # 5 min, same as the GitHub catalog memo; SWR disk cache handles the rest
-_copilot_acp_session_memo: Optional[tuple[float, Optional[list[str]]]] = None
+_COPILOT_ACP_SESSION_MEMO_TTL = 300.0  # 5 min; SWR disk cache handles the rest
+_COPILOT_ACP_SESSION_FAIL_TTL = 30.0  # failed probes re-probe quickly so a fresh CLI login is picked up
+_copilot_acp_session_memo: Optional[tuple[float, float, Optional[list[str]]]] = None  # (at, ttl, models)
 
 
 def _copilot_acp_session_models(force_refresh: bool) -> Optional[list[str]]:
     """Enabled models from a signed-in ``copilot --acp`` session, memoized for a few minutes —
     successes AND failures. Model-switch validation (``models_validate._static_catalog``) reads
     this uncached on every ``/model`` switch, and each miss is a CLI spawn + handshake (up to the
-    probe timeout), so without the memo every switch paid a subprocess."""
+    probe timeout), so without the memo every switch paid a subprocess. A failed probe is
+    memoized much more briefly so a user who signs in to the CLI right after a miss is picked up
+    on the next switch (or immediately via ``/model --refresh``, which clears this memo)."""
     global _copilot_acp_session_memo
     now = time.monotonic()
     memo = _copilot_acp_session_memo
-    if not force_refresh and memo is not None and now - memo[0] < _COPILOT_ACP_SESSION_MEMO_TTL:
-        return memo[1]
+    if not force_refresh and memo is not None and now - memo[0] < memo[1]:
+        return memo[2]
     from providers import get_provider_profile
 
     try:
@@ -1256,7 +1259,7 @@ def _copilot_acp_session_models(force_refresh: bool) -> Optional[list[str]]:
     except Exception:
         logger.debug("copilot-acp session model discovery failed", exc_info=True)
         live = None
-    _copilot_acp_session_memo = (now, live)
+    _copilot_acp_session_memo = (now, _COPILOT_ACP_SESSION_MEMO_TTL if live else _COPILOT_ACP_SESSION_FAIL_TTL, live)
     return live
 
 
@@ -1738,6 +1741,11 @@ def clear_provider_models_cache(provider: Optional[str] = None) -> None:
         _OLLAMA_LOCAL_MODELS_CACHE.clear()
         _OLLAMA_LOCAL_PROBE_FAILURE_CACHE.clear()
         _OLLAMA_LOCAL_PROBE_REACHABLE.clear()
+        # A fresh copilot-acp CLI login must be visible to the next /model switch (this helper is
+        # what ``--refresh`` runs): don't let the 5-min session memo (or its failure memo) serve
+        # a stale signed-out probe past an explicit refresh.
+        global _copilot_acp_session_memo
+        _copilot_acp_session_memo = None
         if provider is None:
             path = _provider_models_cache_path()
             if path.exists():
diff --git a/plugins/model-providers/copilot-acp/__init__.py b/plugins/model-providers/copilot-acp/__init__.py
index c351ca364f..6027873a84 100644
--- a/plugins/model-providers/copilot-acp/__init__.py
+++ b/plugins/model-providers/copilot-acp/__init__.py
@@ -33,13 +33,18 @@ class CopilotACPProfile(ProviderProfile):
         """
         from hermes_cli.auth import resolve_external_process_provider_credentials
 
-        creds = resolve_external_process_provider_credentials(self.name)
-        if not str(creds.get("base_url") or "").startswith("acp://"):
+        try:
+            creds = resolve_external_process_provider_credentials(self.name)
+            if not str(creds.get("base_url") or "").startswith("acp://"):
+                return None
+            client = self.create_client(
+                api_key=creds.get("api_key"), base_url=creds.get("base_url"),
+                command=creds.get("command"), args=creds.get("args"))
+            return client.list_models(timeout_seconds=timeout) or None
+        except Exception:
+            # Missing CLI (AuthError), refused --acp / failed spawn (RuntimeError), probe
+            # timeout — the base fetch_models contract is "None if the fetch failed".
             return None
-        client = self.create_client(
-            api_key=creds.get("api_key"), base_url=creds.get("base_url"),
-            command=creds.get("command"), args=creds.get("args"))
-        return client.list_models(timeout_seconds=timeout) or None
 
 
 copilot_acp = CopilotACPProfile(
diff --git a/tests/hermes_cli/test_copilot_in_model_list.py b/tests/hermes_cli/test_copilot_in_model_list.py
index 8337840a9a..6ba0d7b12e 100644
--- a/tests/hermes_cli/test_copilot_in_model_list.py
+++ b/tests/hermes_cli/test_copilot_in_model_list.py
@@ -93,6 +93,9 @@ _ACP_CREDS = {"api_key": "copilot-acp", "base_url": "acp://copilot", "command":
 @pytest.fixture()
 def _fresh_acp_memo(monkeypatch):
     monkeypatch.setattr(models, "_copilot_acp_session_memo", None)
+    yield
+    # Don't leak a memoized (possibly failed) probe into other tests in this process.
+    monkeypatch.setattr(models, "_copilot_acp_session_memo", None)
 
 
 @pytest.mark.parametrize(
@@ -131,7 +134,7 @@ def test_copilot_acp_session_probe_is_memoized_across_model_switch_validation(_f
             assert verdict["accepted"] and verdict["recognized"]
     assert list_models.call_count == 1
 
-    models._copilot_acp_session_memo = None
+    models._copilot_acp_session_memo = None  # (teardown in _fresh_acp_memo restores it)
     with patch("hermes_cli.auth.resolve_external_process_provider_credentials", return_value=_ACP_CREDS), \
          patch("agent.copilot_acp_client.CopilotACPClient.list_models", side_effect=RuntimeError("not signed in")) as list_models, \
          patch("hermes_cli.models._resolve_copilot_catalog_api_key", return_value=""), \