feat: expand /fast to all OpenAI Priority Processing models

Previously /fast only supported gpt-5.4 and forced a provider switch to
openai-codex. Now supports all 13 models from OpenAI's Priority Processing
pricing table (gpt-5.4, gpt-5.4-mini, gpt-5.2, gpt-5.1, gpt-5, gpt-5-mini,
gpt-4.1, gpt-4.1-mini, gpt-4.1-nano, gpt-4o, gpt-4o-mini, o3, o4-mini).

Key changes:
- Replaced _FAST_MODE_BACKEND_CONFIG with _PRIORITY_PROCESSING_MODELS frozenset
- Removed provider-forcing logic — service_tier is now injected into whatever
  API path the user is already on (Codex Responses, Chat Completions, or
  OpenRouter passthrough)
- Added request_overrides support to chat_completions path in run_agent.py
- Updated messaging from 'Codex inference tier' to 'Priority Processing'
- Expanded test coverage for all supported models

cli.py

@@ -2572,7 +2572,7 @@ class HermesCLI:
     def _resolve_turn_agent_config(self, user_message: str) -> dict:
         """Resolve model/runtime overrides for a single user turn."""
         from agent.smart_model_routing import resolve_turn_route
-        from hermes_cli.models import resolve_fast_mode_runtime
+        from hermes_cli.models import resolve_fast_mode_overrides
 
         route = resolve_turn_route(
             user_message,
@@ -2595,27 +2595,10 @@ class HermesCLI:
             return route
 
         try:
-            fast_runtime = resolve_fast_mode_runtime(route.get("model"))
+            overrides = resolve_fast_mode_overrides(route.get("model"))
         except Exception:
-            route["request_overrides"] = None
-            return route
-        if not fast_runtime:
-            route["request_overrides"] = None
-            return route
-
-        runtime = fast_runtime["runtime"]
-        route["runtime"] = runtime
-        route["request_overrides"] = fast_runtime["request_overrides"]
-        route["label"] = f"fast route → {route.get('model')} ({runtime.get('provider')})"
-        route["signature"] = (
-            route.get("model"),
-            runtime.get("provider"),
-            runtime.get("base_url"),
-            runtime.get("api_mode"),
-            runtime.get("command"),
-            tuple(runtime.get("args") or ()),
-            json.dumps(route["request_overrides"], sort_keys=True),
-        )
+            overrides = None
+        route["request_overrides"] = overrides
         return route
 
     def _init_agent(self, *, model_override: str = None, runtime_override: dict = None, route_label: str = None, request_overrides: dict | None = None) -> bool:
@@ -5662,15 +5645,15 @@ class HermesCLI:
             _cprint(f"  {_GOLD}✓ Reasoning effort set to '{arg}' (session only){_RST}")
 
     def _handle_fast_command(self, cmd: str):
-        """Handle /fast — choose the Codex Responses service tier."""
+        """Handle /fast — toggle OpenAI Priority Processing (service_tier)."""
         if not self._fast_command_available():
-            _cprint("  (._.) /fast is only available for models that explicitly expose a fast backend.")
+            _cprint("  (._.) /fast is only available for OpenAI models that support Priority Processing.")
             return
 
         parts = cmd.strip().split(maxsplit=1)
         if len(parts) < 2 or parts[1].strip().lower() == "status":
             status = "fast" if self.service_tier == "priority" else "normal"
-            _cprint(f"  {_GOLD}Codex inference tier: {status}{_RST}")
+            _cprint(f"  {_GOLD}Priority Processing: {status}{_RST}")
             _cprint(f"  {_DIM}Usage: /fast [normal|fast|status]{_RST}")
             return
 
@@ -5691,9 +5674,9 @@ class HermesCLI:
 
         self.agent = None  # Force agent re-init with new service-tier config
         if save_config_value("agent.service_tier", saved_value):
-            _cprint(f"  {_GOLD}✓ Codex inference tier set to {label} (saved to config){_RST}")
+            _cprint(f"  {_GOLD}✓ Priority Processing set to {label} (saved to config){_RST}")
         else:
-            _cprint(f"  {_GOLD}✓ Codex inference tier set to {label} (session only){_RST}")
+            _cprint(f"  {_GOLD}✓ Priority Processing set to {label} (session only){_RST}")
 
     def _on_reasoning(self, reasoning_text: str):
         """Callback for intermediate reasoning display during tool-call loops."""

hermes_cli/commands.py

@@ -100,7 +100,7 @@ COMMAND_REGISTRY: list[CommandDef] = [
     CommandDef("reasoning", "Manage reasoning effort and display", "Configuration",
                args_hint="[level|show|hide]",
                subcommands=("none", "minimal", "low", "medium", "high", "xhigh", "show", "hide", "on", "off")),
-    CommandDef("fast", "Choose Codex inference tier (Normal/Fast)", "Configuration",
+    CommandDef("fast", "Toggle OpenAI Priority Processing (Normal/Fast)", "Configuration",
                cli_only=True, args_hint="[normal|fast|status]",
                subcommands=("normal", "fast", "status", "on", "off")),
     CommandDef("skin", "Show or change the display skin/theme", "Configuration",

hermes_cli/models.py

@@ -1017,58 +1017,45 @@ def provider_label(provider: Optional[str]) -> str:
     return _PROVIDER_LABELS.get(normalized, original or "OpenRouter")
 
 
-_FAST_MODE_BACKEND_CONFIG: dict[str, dict[str, Any]] = {
-    "gpt-5.4": {
-        "provider": "openai-codex",
-        "request_overrides": {"service_tier": "priority"},
-    },
-}
-
-
-def fast_mode_backend_config(model_id: Optional[str]) -> dict[str, Any] | None:
-    """Return backend config for models that expose Fast mode.
-
-    To expose Fast mode for a new model, add its normalized model slug to
-    ``_FAST_MODE_BACKEND_CONFIG`` along with the backend runtime selection and
-    backend-specific request overrides Hermes should apply.
-    """
-    raw = str(model_id or "").strip().lower()
-    if "/" in raw:
-        raw = raw.split("/", 1)[1]
-    config = _FAST_MODE_BACKEND_CONFIG.get(raw)
-    return dict(config) if config else None
+# Models that support OpenAI Priority Processing (service_tier="priority").
+# See https://openai.com/api-priority-processing/ for the canonical list.
+# Only the bare model slug is stored (no vendor prefix).
+_PRIORITY_PROCESSING_MODELS: frozenset[str] = frozenset({
+    "gpt-5.4",
+    "gpt-5.4-mini",
+    "gpt-5.2",
+    "gpt-5.1",
+    "gpt-5",
+    "gpt-5-mini",
+    "gpt-4.1",
+    "gpt-4.1-mini",
+    "gpt-4.1-nano",
+    "gpt-4o",
+    "gpt-4o-mini",
+    "o3",
+    "o4-mini",
+})
 
 
 def model_supports_fast_mode(model_id: Optional[str]) -> bool:
-    """Return whether Hermes should expose Fast mode for the active model."""
-    return fast_mode_backend_config(model_id) is not None
+    """Return whether Hermes should expose the /fast (Priority Processing) toggle."""
+    raw = str(model_id or "").strip().lower()
+    if "/" in raw:
+        raw = raw.split("/", 1)[1]
+    return raw in _PRIORITY_PROCESSING_MODELS
 
 
-def resolve_fast_mode_runtime(model_id: Optional[str]) -> dict[str, Any] | None:
-    """Resolve runtime selection and request overrides for a fast-mode model."""
-    cfg = fast_mode_backend_config(model_id)
-    if not cfg:
+def resolve_fast_mode_overrides(model_id: Optional[str]) -> dict[str, Any] | None:
+    """Return request_overrides for Priority Processing, or None if unsupported.
+
+    Unlike the previous ``resolve_fast_mode_runtime``, this does NOT force a
+    provider/backend switch.  The ``service_tier`` parameter is injected into
+    whatever API path the user is already on (Codex Responses, Chat Completions,
+    or OpenRouter passthrough).
+    """
+    if not model_supports_fast_mode(model_id):
         return None
-
-    from hermes_cli.runtime_provider import resolve_runtime_provider
-
-    runtime = resolve_runtime_provider(
-        requested=cfg.get("provider"),
-        explicit_base_url=cfg.get("base_url"),
-        explicit_api_key=cfg.get("api_key"),
-    )
-    return {
-        "runtime": {
-            "api_key": runtime.get("api_key"),
-            "base_url": runtime.get("base_url"),
-            "provider": runtime.get("provider"),
-            "api_mode": runtime.get("api_mode"),
-            "command": runtime.get("command"),
-            "args": list(runtime.get("args") or []),
-            "credential_pool": runtime.get("credential_pool"),
-        },
-        "request_overrides": dict(cfg.get("request_overrides") or {}),
-    }
+    return {"service_tier": "priority"}
 
 
 def _resolve_copilot_catalog_api_key() -> str:

run_agent.py

@@ -5686,6 +5686,11 @@ class AIAgent:
         if "x.ai" in self._base_url_lower and hasattr(self, "session_id") and self.session_id:
             api_kwargs["extra_headers"] = {"x-grok-conv-id": self.session_id}
 
+        # Priority Processing / generic request overrides (e.g. service_tier).
+        # Applied last so overrides win over any defaults set above.
+        if self.request_overrides:
+            api_kwargs.update(self.request_overrides)
+
         return api_kwargs
 
     def _supports_reasoning_extra_body(self) -> bool:

tests/cli/test_fast_command.py

@@ -108,15 +108,52 @@ class TestHandleFastCommand(unittest.TestCase):
         self.assertTrue(mock_cprint.called)
 
 
-class TestFastModeRegistry(unittest.TestCase):
-    def test_only_gpt_5_4_is_enabled_for_codex(self):
-        from hermes_cli.models import fast_mode_backend_config
+class TestPriorityProcessingModels(unittest.TestCase):
+    """Verify the expanded Priority Processing model registry."""
 
-        assert fast_mode_backend_config("gpt-5.4") == {
-            "provider": "openai-codex",
-            "request_overrides": {"service_tier": "priority"},
-        }
-        assert fast_mode_backend_config("gpt-5.3-codex") is None
+    def test_all_documented_models_supported(self):
+        from hermes_cli.models import model_supports_fast_mode
+
+        # All models from OpenAI's Priority Processing pricing table
+        supported = [
+            "gpt-5.4", "gpt-5.4-mini", "gpt-5.2",
+            "gpt-5.1", "gpt-5", "gpt-5-mini",
+            "gpt-4.1", "gpt-4.1-mini", "gpt-4.1-nano",
+            "gpt-4o", "gpt-4o-mini",
+            "o3", "o4-mini",
+        ]
+        for model in supported:
+            assert model_supports_fast_mode(model), f"{model} should support fast mode"
+
+    def test_vendor_prefix_stripped(self):
+        from hermes_cli.models import model_supports_fast_mode
+
+        assert model_supports_fast_mode("openai/gpt-5.4") is True
+        assert model_supports_fast_mode("openai/gpt-4.1") is True
+        assert model_supports_fast_mode("openai/o3") is True
+
+    def test_non_priority_models_rejected(self):
+        from hermes_cli.models import model_supports_fast_mode
+
+        assert model_supports_fast_mode("gpt-5.3-codex") is False
+        assert model_supports_fast_mode("claude-sonnet-4") is False
+        assert model_supports_fast_mode("") is False
+        assert model_supports_fast_mode(None) is False
+
+    def test_resolve_overrides_returns_service_tier(self):
+        from hermes_cli.models import resolve_fast_mode_overrides
+
+        result = resolve_fast_mode_overrides("gpt-5.4")
+        assert result == {"service_tier": "priority"}
+
+        result = resolve_fast_mode_overrides("gpt-4.1")
+        assert result == {"service_tier": "priority"}
+
+    def test_resolve_overrides_none_for_unsupported(self):
+        from hermes_cli.models import resolve_fast_mode_overrides
+
+        assert resolve_fast_mode_overrides("gpt-5.3-codex") is None
+        assert resolve_fast_mode_overrides("claude-sonnet-4") is None
 
 
 class TestFastModeRouting(unittest.TestCase):
@@ -126,7 +163,16 @@ class TestFastModeRouting(unittest.TestCase):
 
         assert cli_mod.HermesCLI._fast_command_available(stub) is True
 
-    def test_turn_route_switches_to_model_backend_when_fast_enabled(self):
+    def test_fast_command_exposed_for_non_codex_models(self):
+        cli_mod = _import_cli()
+        stub = SimpleNamespace(provider="openai", requested_provider="openai", model="gpt-4.1", agent=None)
+        assert cli_mod.HermesCLI._fast_command_available(stub) is True
+
+        stub = SimpleNamespace(provider="openrouter", requested_provider="openrouter", model="o3", agent=None)
+        assert cli_mod.HermesCLI._fast_command_available(stub) is True
+
+    def test_turn_route_injects_overrides_without_provider_switch(self):
+        """Fast mode should add request_overrides but NOT change the provider/runtime."""
         cli_mod = _import_cli()
         stub = SimpleNamespace(
             model="gpt-5.4",
@@ -141,35 +187,28 @@ class TestFastModeRouting(unittest.TestCase):
             service_tier="priority",
         )
 
-        with (
-            patch("agent.smart_model_routing.resolve_turn_route", return_value={
-                "model": "gpt-5.4",
-                "runtime": {
-                    "api_key": "primary-key",
-                    "base_url": "https://openrouter.ai/api/v1",
-                    "provider": "openrouter",
-                    "api_mode": "chat_completions",
-                    "command": None,
-                    "args": [],
-                    "credential_pool": None,
-                },
-                "label": None,
-                "signature": ("gpt-5.4", "openrouter", "https://openrouter.ai/api/v1", "chat_completions", None, ()),
-            }),
-            patch("hermes_cli.runtime_provider.resolve_runtime_provider", return_value={
-                "provider": "openai-codex",
-                "api_mode": "codex_responses",
-                "base_url": "https://chatgpt.com/backend-api/codex",
-                "api_key": "codex-key",
-                "command": None,
-                "args": [],
-                "credential_pool": None,
-            }),
-        ):
+        original_runtime = {
+            "api_key": "***",
+            "base_url": "https://openrouter.ai/api/v1",
+            "provider": "openrouter",
+            "api_mode": "chat_completions",
+            "command": None,
+            "args": [],
+            "credential_pool": None,
+        }
+
+        with patch("agent.smart_model_routing.resolve_turn_route", return_value={
+            "model": "gpt-5.4",
+            "runtime": dict(original_runtime),
+            "label": None,
+            "signature": ("gpt-5.4", "openrouter", "https://openrouter.ai/api/v1", "chat_completions", None, ()),
+        }):
             route = cli_mod.HermesCLI._resolve_turn_agent_config(stub, "hi")
 
-        assert route["runtime"]["provider"] == "openai-codex"
-        assert route["runtime"]["api_mode"] == "codex_responses"
+        # Provider should NOT have changed
+        assert route["runtime"]["provider"] == "openrouter"
+        assert route["runtime"]["api_mode"] == "chat_completions"
+        # But request_overrides should be set
         assert route["request_overrides"] == {"service_tier": "priority"}
 
     def test_turn_route_keeps_primary_runtime_when_model_has_no_fast_backend(self):
@@ -190,7 +229,7 @@ class TestFastModeRouting(unittest.TestCase):
         primary_route = {
             "model": "gpt-5.3-codex",
             "runtime": {
-                "api_key": "primary-key",
+                "api_key": "***",
                 "base_url": "https://openrouter.ai/api/v1",
                 "provider": "openrouter",
                 "api_mode": "chat_completions",

tests/run_agent/test_provider_parity.py

@@ -225,6 +225,26 @@ class TestDeveloperRoleSwap:
         assert kwargs["messages"][0]["role"] == "developer"
 
 
+class TestBuildApiKwargsChatCompletionsServiceTier:
+    """service_tier via request_overrides works on the chat_completions path."""
+
+    def test_includes_service_tier_via_request_overrides(self, monkeypatch):
+        agent = _make_agent(monkeypatch, "openrouter")
+        agent.model = "gpt-4.1"
+        agent.request_overrides = {"service_tier": "priority"}
+        messages = [{"role": "user", "content": "hi"}]
+        kwargs = agent._build_api_kwargs(messages)
+        assert kwargs["service_tier"] == "priority"
+
+    def test_no_service_tier_when_overrides_empty(self, monkeypatch):
+        agent = _make_agent(monkeypatch, "openrouter")
+        agent.model = "gpt-4.1"
+        agent.request_overrides = {}
+        messages = [{"role": "user", "content": "hi"}]
+        kwargs = agent._build_api_kwargs(messages)
+        assert "service_tier" not in kwargs
+
+
 class TestBuildApiKwargsAIGateway:
     def test_uses_chat_completions_format(self, monkeypatch):
         agent = _make_agent(monkeypatch, "ai-gateway", base_url="https://ai-gateway.vercel.sh/v1")