fix(tui): guard personality overlay when personalities is null

TUI auto-resolves `display.personality` at session init, unlike the base CLI.
If config contains `agent.personalities: null`, `_resolve_personality_prompt`
called `.get()` on None and failed before model/provider selection.
Normalize null personalities to `{}` and surface a targeted config warning.

tests/tui_gateway/test_make_agent_provider.py

@@ -67,11 +67,25 @@ def test_probe_config_health_flags_null_sections():
     assert "model" not in msg
 
 
+def test_probe_config_health_flags_null_personalities_with_active_personality():
+    from tui_gateway.server import _probe_config_health
+
+    msg = _probe_config_health(
+        {
+            "agent": {"personalities": None},
+            "display": {"personality": "kawaii"},
+            "model": {},
+        }
+    )
+    assert "display.personality" in msg
+    assert "agent.personalities" in msg
+
+
 def test_make_agent_tolerates_null_config_sections():
     """Bare `agent:` / `display:` keys in ~/.hermes/config.yaml parse as
     None. cfg.get("agent", {}) returns None (default only fires on missing
     key), so downstream .get() chains must be guarded. Reported via Twitter
-    against the new TUI; CLI path is unaffected."""
+    against the new TUI."""
 
     fake_runtime = {
         "provider": "openrouter",
@@ -99,3 +113,37 @@ def test_make_agent_tolerates_null_config_sections():
         _make_agent("sid-null", "key-null")
 
         assert mock_agent.called
+
+
+def test_make_agent_tolerates_null_personalities_with_active_personality():
+    fake_runtime = {
+        "provider": "openrouter",
+        "base_url": "https://api.synthetic.new/v1",
+        "api_key": "sk-test",
+        "api_mode": "chat_completions",
+        "command": None,
+        "args": None,
+        "credential_pool": None,
+    }
+    cfg = {
+        "agent": {"personalities": None},
+        "display": {"personality": "kawaii"},
+        "model": {"default": "glm-5"},
+    }
+
+    with (
+        patch("tui_gateway.server._load_cfg", return_value=cfg),
+        patch("tui_gateway.server._get_db", return_value=MagicMock()),
+        patch("cli.load_cli_config", return_value={"agent": {"personalities": None}}),
+        patch(
+            "hermes_cli.runtime_provider.resolve_runtime_provider",
+            return_value=fake_runtime,
+        ),
+        patch("run_agent.AIAgent") as mock_agent,
+    ):
+        from tui_gateway.server import _make_agent
+
+        _make_agent("sid-null-personality", "key-null-personality")
+
+        assert mock_agent.called
+        assert mock_agent.call_args.kwargs["ephemeral_system_prompt"] is None

tui_gateway/server.py

@@ -829,15 +829,32 @@ def _probe_config_health(cfg: dict) -> str:
     drop nested settings. Returns warning or ''."""
     if not isinstance(cfg, dict):
         return ""
+    warnings: list[str] = []
     null_keys = sorted(k for k, v in cfg.items() if v is None)
     if not null_keys:
-        return ""
-    keys = ", ".join(f"`{k}`" for k in null_keys)
-    return (
-        f"config.yaml has empty section(s): {keys}. "
-        f"Remove the line(s) or set them to `{{}}` — "
-        f"empty sections silently drop nested settings."
-    )
+        pass
+    else:
+        keys = ", ".join(f"`{k}`" for k in null_keys)
+        warnings.append(
+            f"config.yaml has empty section(s): {keys}. "
+            f"Remove the line(s) or set them to `{{}}` — "
+            f"empty sections silently drop nested settings."
+        )
+    display_cfg = cfg.get("display")
+    agent_cfg = cfg.get("agent")
+    if isinstance(display_cfg, dict):
+        personality = str(display_cfg.get("personality", "") or "").strip().lower()
+        if (
+            personality
+            and personality not in {"default", "none", "neutral"}
+            and isinstance(agent_cfg, dict)
+            and agent_cfg.get("personalities") is None
+        ):
+            warnings.append(
+                "`display.personality` is set but `agent.personalities` is empty/null; "
+                "personality overlay will be skipped."
+            )
+    return " ".join(warnings).strip()
 
 
 def _session_info(agent) -> dict:
@@ -1134,16 +1151,16 @@ def _resolve_personality_prompt(cfg: dict) -> str:
     try:
         from cli import load_cli_config
 
-        personalities = (load_cli_config().get("agent") or {}).get("personalities", {})
+        personalities = (load_cli_config().get("agent") or {}).get("personalities", {}) or {}
     except Exception:
         try:
             from hermes_cli.config import load_config as _load_full_cfg
 
-            personalities = (_load_full_cfg().get("agent") or {}).get(
-                "personalities", {}
+            personalities = (
+                (_load_full_cfg().get("agent") or {}).get("personalities", {}) or {}
             )
         except Exception:
-            personalities = (cfg.get("agent") or {}).get("personalities", {})
+            personalities = (cfg.get("agent") or {}).get("personalities", {}) or {}
     pval = personalities.get(name)
     if pval is None:
         return ""