diff --git a/README.md b/README.md
index 45a2dfa..5e455bf 100644
--- a/README.md
+++ b/README.md
@@ -58,7 +58,7 @@ confirm_destructive = true
 max_context_tokens = 200000
 ```
 
-Supported provider presets today: `openai`, `openai-compatible`, `deepseek` (OpenAI convention; default models `deepseek-v4-flash` and `deepseek-v4-pro` if `models` is omitted). Anthropic presets are modeled in config but not wired in the runtime client yet.
+Supported provider presets today: `openai` (default if `preset` is omitted; default models `gpt-5.4` / `gpt-5.4-mini` / `gpt-5.4-nano` when `models` is omitted), `openai-compatible`, `deepseek` (OpenAI convention; default models `deepseek-v4-flash` and `deepseek-v4-pro` if `models` is omitted). Anthropic presets are modeled in config but not wired in the runtime client yet.
 
 If `[database]` is omitted (or SQLite `url` is empty/`":memory:"`), chat uses a durable file under the user data dir (e.g. `~/.local/share/plyngent/chat.db` on Linux).
 
diff --git a/doc/plyngent.example.toml b/doc/plyngent.example.toml
index d6b3180..fa5926f 100644
--- a/doc/plyngent.example.toml
+++ b/doc/plyngent.example.toml
@@ -32,6 +32,8 @@ access_key_or_token = "sk-replace-me"
 "gpt-4o-mini" = { text = true, cost_factor = 1.0 }
 
 # --- OpenAI platform (Responses API; tag is "openai") ---
+# If ``preset`` is omitted, it defaults to "openai".
+# If ``models`` is omitted, defaults: gpt-5.4, gpt-5.4-mini, gpt-5.4-nano.
 # [providers.openai]
 # preset = "openai"
 # access_key_or_token = "sk-replace-me"
diff --git a/src/plyngent/config/models.py b/src/plyngent/config/models.py
index d844da4..48e84f3 100644
--- a/src/plyngent/config/models.py
+++ b/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)
 
 
diff --git a/src/plyngent/config/store.py b/src/plyngent/config/store.py
index 3c071b8..ec2fcf4 100644
--- a/src/plyngent/config/store.py
+++ b/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
diff --git a/tests/test_config/test_config.py b/tests/test_config/test_config.py
index 9944e69..92ae82d 100644
--- a/tests/test_config/test_config.py
+++ b/tests/test_config/test_config.py
@@ -58,6 +58,27 @@ def test_deepseek_default_models_on_construct() -> None:
     assert set(provider.models) == {"deepseek-v4-flash", "deepseek-v4-pro"}
 
 
+def test_openai_default_models_on_construct() -> None:
+    provider = OpenAIProvider(access_key_or_token="sk-test")
+    assert set(provider.models) == {"gpt-5.4", "gpt-5.4-mini", "gpt-5.4-nano"}
+
+
+def test_openai_omitted_preset_and_models_from_toml(tmp_path: Path) -> None:
+    path = tmp_path / "openai-defaults.toml"
+    _ = path.write_text(
+        """
+[providers.oai]
+access_key_or_token = "sk-test"
+""",
+        encoding="utf-8",
+    )
+    config = plyngent.config.load(path)
+    assert "oai" in config.providers
+    provider = config.providers["oai"]
+    assert isinstance(provider, OpenAIProvider)
+    assert set(provider.models) == {"gpt-5.4", "gpt-5.4-mini", "gpt-5.4-nano"}
+
+
 def test_deepseek_explicit_models_override_defaults() -> None:
     from plyngent.config import ModelConfig