core/config: default OpenAI preset and model catalog

Missing preset becomes openai; omitted models seed gpt-5.4 / mini / nano.

src/plyngent/config/models.py

@@ -53,14 +53,27 @@ class ProviderConfig(Struct, tag_field="preset", omit_defaults=True):
     models: dict[str, ModelConfig] = field(default_factory=dict)
 
 
+def _default_openai_models() -> dict[str, ModelConfig]:
+    """Current OpenAI text catalog when TOML omits ``models``."""
+    return {
+        "gpt-5.4": ModelConfig(text=True),
+        "gpt-5.4-mini": ModelConfig(text=True),
+        "gpt-5.4-nano": ModelConfig(text=True),
+    }
+
+
 class OpenAIProvider(ProviderConfig, tag="openai"):
     """OpenAI platform provider (agent uses Responses API).
 
     ``provider_tools`` are hosted/provider-side tools (e.g. web_search) passed
     through to ``POST /responses`` as opaque dicts. They are **not** local
     ``ToolRegistry`` handlers and are ignored by non-OpenAI clients.
+
+    When ``models`` is omitted in TOML, seeds a small default catalog (same idea
+    as DeepSeek). Explicit ``models = {}`` stays empty (recoverable / free-form).
     """
 
+    models: dict[str, ModelConfig] = field(default_factory=_default_openai_models)
     provider_tools: list[dict[str, Any]] = field(default_factory=list)
 
 

src/plyngent/config/store.py

@@ -60,9 +60,14 @@ def _parse_providers(
             bad_providers[name] = raw_entry
             continue
 
+        entry = cast("dict[str, object]", raw_entry)
+        # Missing preset → OpenAI platform (Responses-capable defaults).
+        if "preset" not in entry:
+            entry = {**entry, "preset": "openai"}
+
         # Try tagged-union dispatch via msgspec
         try:
-            provider: Provider = msgspec.convert(raw_entry, Provider)
+            provider: Provider = msgspec.convert(entry, Provider)
         except msgspec.ValidationError:
             bad_providers[name] = raw_entry
             continue
@@ -72,12 +77,13 @@ def _parse_providers(
         cls = type(provider)
         known = set(cls.__struct_fields__)
         known.add("preset")  # tag_field, excluded from __struct_fields__
-        if set(cast("dict[str, object]", raw_entry).keys()) - known:
+        # Validate against the entry we actually converted (may have injected preset).
+        if set(entry.keys()) - known:
             bad_providers[name] = raw_entry
             continue
 
-        # Empty models: keep as recoverable (DeepSeek seeds defaults when
-        # models is omitted, so only explicit models={} lands here).
+        # Empty models: recoverable. OpenAI/DeepSeek seed defaults when
+        # ``models`` is omitted; only explicit models={} lands here.
         if not provider.models:
             recoverable[name] = provider
             continue