Add Cerebras provider support

docs/models/cerebras.md

@@ -0,0 +1,83 @@
+# Cerebras
+
+## Install
+
+To use `CerebrasModel`, you need to either install `pydantic-ai`, or install `pydantic-ai-slim` with the `cerebras` optional group (which installs `openai`):
+
+```bash
+pip install "pydantic-ai-slim[cerebras]"
+```
+
+or
+
+```bash
+uv add "pydantic-ai-slim[cerebras]"
+```
+
+## Configuration
+
+To use [Cerebras](https://cerebras.ai/) through their API, go to [cloud.cerebras.ai](https://cloud.cerebras.ai/?utm_source=3pi_pydantic-ai&utm_campaign=partner_doc) and follow your nose until you find the place to generate an API key.
+
+`CerebrasModelName` contains a list of available Cerebras models.
+
+## Environment variable
+
+Once you have the API key, you can set it as an environment variable:
+
+```bash
+export CEREBRAS_API_KEY='your-api-key'
+```
+
+You can then use `CerebrasModel` by name:
+
+```python
+from pydantic_ai import Agent
+
+agent = Agent('cerebras:llama-3.3-70b')
+...
+```
+
+Or initialise the model directly with just the model name:
+
+```python
+from pydantic_ai import Agent
+from pydantic_ai.models.cerebras import CerebrasModel
+
+model = CerebrasModel('llama-3.3-70b')
+agent = Agent(model)
+...
+```
+
+## `provider` argument
+
+You can provide a custom `Provider` via the `provider` argument:
+
+```python
+from pydantic_ai import Agent
+from pydantic_ai.models.cerebras import CerebrasModel
+from pydantic_ai.providers.cerebras import CerebrasProvider
+
+model = CerebrasModel(
+    'llama-3.3-70b', provider=CerebrasProvider(api_key='your-api-key')
+)
+agent = Agent(model)
+...
+```
+
+You can also customize the `CerebrasProvider` with a custom `httpx.AsyncHTTPClient`:
+
+```python
+from httpx import AsyncClient
+
+from pydantic_ai import Agent
+from pydantic_ai.models.cerebras import CerebrasModel
+from pydantic_ai.providers.cerebras import CerebrasProvider
+
+custom_http_client = AsyncClient(timeout=30)
+model = CerebrasModel(
+    'llama-3.3-70b',
+    provider=CerebrasProvider(api_key='your-api-key', http_client=custom_http_client),
+)
+agent = Agent(model)
+...
+```

mkdocs.yml

@@ -30,6 +30,7 @@ nav:
           - models/anthropic.md
           - models/google.md
           - models/bedrock.md
+          - models/cerebras.md
           - models/cohere.md
           - models/groq.md
           - models/mistral.md

pydantic_ai_slim/pydantic_ai/models/__init__.py

@@ -134,7 +134,6 @@
         'cerebras:llama-3.3-70b',
         'cerebras:llama3.1-8b',
         'cerebras:qwen-3-235b-a22b-instruct-2507',
-        'cerebras:qwen-3-235b-a22b-thinking-2507',
         'cerebras:qwen-3-32b',
         'cerebras:zai-glm-4.6',
         'cohere:c4ai-aya-expanse-32b',
@@ -800,7 +799,6 @@ def infer_model(  # noqa: C901
         'openai',
         'azure',
         'deepseek',
-        'cerebras',
         'fireworks',
         'github',
         'grok',
@@ -818,7 +816,11 @@ def infer_model(  # noqa: C901
     elif model_kind in ('google-gla', 'google-vertex'):
         model_kind = 'google'
 
-    if model_kind == 'openai-chat':
+    if model_kind == 'cerebras':
+        from .cerebras import CerebrasModel
+
+        return CerebrasModel(model_name, provider=provider)  # type: ignore[arg-type]
+    elif model_kind == 'openai-chat':
         from .openai import OpenAIChatModel
 
         return OpenAIChatModel(model_name, provider=provider)

pydantic_ai_slim/pydantic_ai/models/cerebras.py

@@ -0,0 +1,58 @@
+"""Cerebras model implementation using OpenAI-compatible API."""
+
+from __future__ import annotations as _annotations
+
+from dataclasses import dataclass
+from typing import Literal
+
+from ..profiles import ModelProfileSpec
+from ..providers import Provider
+from ..settings import ModelSettings
+from .openai import OpenAIChatModel
+
+try:
+    from openai import AsyncOpenAI
+except ImportError as _import_error:  # pragma: no cover
+    raise ImportError(
+        'Please install the `openai` package to use the Cerebras model, '
+        'you can use the `cerebras` optional group — `pip install "pydantic-ai-slim[cerebras]"'
+    ) from _import_error
+
+__all__ = ('CerebrasModel', 'CerebrasModelName')
+
+CerebrasModelName = Literal[
+    'gpt-oss-120b',
+    'llama-3.3-70b',
+    'llama3.1-8b',
+    'qwen-3-235b-a22b-instruct-2507',
+    'qwen-3-32b',
+    'zai-glm-4.6',
+]
+
+
+@dataclass(init=False)
+class CerebrasModel(OpenAIChatModel):
+    """A model that uses Cerebras's OpenAI-compatible API.
+
+    Cerebras provides ultra-fast inference powered by the Wafer-Scale Engine (WSE).
+
+    Apart from `__init__`, all methods are private or match those of the base class.
+    """
+
+    def __init__(
+        self,
+        model_name: CerebrasModelName,
+        *,
+        provider: Literal['cerebras'] | Provider[AsyncOpenAI] = 'cerebras',
+        profile: ModelProfileSpec | None = None,
+        settings: ModelSettings | None = None,
+    ):
+        """Initialize a Cerebras model.
+
+        Args:
+            model_name: The name of the Cerebras model to use.
+            provider: The provider to use. Defaults to 'cerebras'.
+            profile: The model profile to use. Defaults to a profile based on the model name.
+            settings: Model-specific settings that will be used as defaults for this model.
+        """
+        super().__init__(model_name, provider=provider, profile=profile, settings=settings)

pydantic_ai_slim/pydantic_ai/providers/cerebras.py

@@ -10,7 +10,7 @@
 from pydantic_ai.models import cached_async_http_client
 from pydantic_ai.profiles.harmony import harmony_model_profile
 from pydantic_ai.profiles.meta import meta_model_profile
-from pydantic_ai.profiles.openai import OpenAIJsonSchemaTransformer, OpenAIModelProfile
+from pydantic_ai.profiles.openai import OpenAIModelProfile
 from pydantic_ai.profiles.qwen import qwen_model_profile
 from pydantic_ai.providers import Provider
 
@@ -19,7 +19,7 @@
 except ImportError as _import_error:  # pragma: no cover
     raise ImportError(
         'Please install the `openai` package to use the Cerebras provider, '
-        'you can use the `openai` optional group — `pip install "pydantic-ai-slim[openai]"`'
+        'you can use the `cerebras` optional group — `pip install "pydantic-ai-slim[cerebras]"`'
     ) from _import_error
 
 
@@ -39,27 +39,22 @@ def client(self) -> AsyncOpenAI:
         return self._client
 
     def model_profile(self, model_name: str) -> ModelProfile | None:
-        prefix_to_profile = {'llama': meta_model_profile, 'qwen': qwen_model_profile, 'gpt-oss': harmony_model_profile}
+        prefix_to_profile = {
+            'llama': meta_model_profile,
+            'qwen': qwen_model_profile,
+            'gpt-oss': harmony_model_profile,
+        }
 
         profile = None
+        model_name_lower = model_name.lower()
         for prefix, profile_func in prefix_to_profile.items():
-            model_name = model_name.lower()
-            if model_name.startswith(prefix):
+            if model_name_lower.startswith(prefix):
                 profile = profile_func(model_name)
+                break
 
-        # According to https://inference-docs.cerebras.ai/resources/openai#currently-unsupported-openai-features,
-        # Cerebras doesn't support some model settings.
-        unsupported_model_settings = (
-            'frequency_penalty',
-            'logit_bias',
-            'presence_penalty',
-            'parallel_tool_calls',
-            'service_tier',
-        )
-        return OpenAIModelProfile(
-            json_schema_transformer=OpenAIJsonSchemaTransformer,
-            openai_unsupported_model_settings=unsupported_model_settings,
-        ).update(profile)
+        # Wrap in OpenAIModelProfile with web search disabled
+        # Cerebras doesn't support web search
+        return OpenAIModelProfile(openai_chat_supports_web_search=False).update(profile)
 
     @overload
     def __init__(self) -> None: ...
@@ -70,6 +65,9 @@ def __init__(self, *, api_key: str) -> None: ...
     @overload
     def __init__(self, *, api_key: str, http_client: httpx.AsyncClient) -> None: ...
 
+    @overload
+    def __init__(self, *, http_client: httpx.AsyncClient) -> None: ...
+
     @overload
     def __init__(self, *, openai_client: AsyncOpenAI | None = None) -> None: ...
 
@@ -80,6 +78,14 @@ def __init__(
         openai_client: AsyncOpenAI | None = None,
         http_client: httpx.AsyncClient | None = None,
     ) -> None:
+        """Create a new Cerebras provider.
+
+        Args:
+            api_key: The API key to use for authentication, if not provided, the `CEREBRAS_API_KEY` environment variable
+                will be used if available.
+            openai_client: An existing `AsyncOpenAI` client to use. If provided, `api_key` and `http_client` must be `None`.
+            http_client: An existing `httpx.AsyncClient` to use for making HTTP requests.
+        """
         api_key = api_key or os.getenv('CEREBRAS_API_KEY')
         if not api_key and openai_client is None:
             raise UserError(

pydantic_ai_slim/pyproject.toml

@@ -72,6 +72,7 @@ cohere = ["cohere>=5.18.0; platform_system != 'Emscripten'"]
 vertexai = ["google-auth>=2.36.0", "requests>=2.32.2"]
 google = ["google-genai>=1.51.0"]
 anthropic = ["anthropic>=0.70.0"]
+cerebras = ["openai>=1.107.2"]
 groq = ["groq>=0.25.0"]
 mistral = ["mistralai>=1.9.10"]
 bedrock = ["boto3>=1.40.14"]

tests/models/cassettes/test_model_names/test_known_model_names.yaml

@@ -124,7 +124,7 @@ interactions:
       alt-svc:
       - h3=":443"; ma=86400
       content-length:
-      - '570'
+      - '479'
       content-type:
       - application/json
       referrer-policy:
@@ -133,32 +133,28 @@ interactions:
       - max-age=3600; includeSubDomains
     parsed_body:
       data:
-      - created: 0
-        id: qwen-3-235b-a22b-thinking-2507
-        object: model
-        owned_by: Cerebras
       - created: 0
         id: llama-3.3-70b
         object: model
         owned_by: Cerebras
       - created: 0
-        id: qwen-3-235b-a22b-instruct-2507
+        id: llama3.1-8b
         object: model
         owned_by: Cerebras
       - created: 0
-        id: qwen-3-32b
+        id: zai-glm-4.6
         object: model
         owned_by: Cerebras
       - created: 0
-        id: zai-glm-4.6
+        id: qwen-3-32b
         object: model
         owned_by: Cerebras
       - created: 0
         id: gpt-oss-120b
         object: model
         owned_by: Cerebras
       - created: 0
-        id: llama3.1-8b
+        id: qwen-3-235b-a22b-instruct-2507
         object: model
         owned_by: Cerebras
       object: list

tests/models/test_cerebras.py

@@ -0,0 +1,73 @@
+import re
+
+import pytest
+
+from pydantic_ai._json_schema import InlineDefsJsonSchemaTransformer
+from pydantic_ai.exceptions import UserError
+from pydantic_ai.profiles.openai import OpenAIJsonSchemaTransformer, OpenAIModelProfile
+
+from ..conftest import TestEnv, try_import
+
+with try_import() as imports_successful:
+    from openai import AsyncOpenAI
+
+    from pydantic_ai.models.cerebras import CerebrasModel
+    from pydantic_ai.providers.cerebras import CerebrasProvider
+
+pytestmark = pytest.mark.skipif(not imports_successful(), reason='openai not installed')
+
+
+def test_cerebras_model_init():
+    model = CerebrasModel('llama-3.3-70b', provider=CerebrasProvider(api_key='test_key'))
+    assert model.model_name == 'llama-3.3-70b'
+    assert isinstance(model._provider, CerebrasProvider)  # type: ignore[reportPrivateUsage]
+    assert model._provider.client.api_key == 'test_key'  # type: ignore[reportPrivateUsage]
+
+
+def test_cerebras_model_profile():
+    provider = CerebrasProvider(api_key='test_key')
+
+    # Test Llama model
+    model = CerebrasModel('llama-3.3-70b', provider=provider)
+    profile = model.profile
+    assert isinstance(profile, OpenAIModelProfile)
+    assert profile.json_schema_transformer == InlineDefsJsonSchemaTransformer
+    assert OpenAIModelProfile.from_profile(profile).openai_chat_supports_web_search is False
+
+    # Test Qwen model
+    model = CerebrasModel('qwen-3-235b-a22b-instruct-2507', provider=provider)
+    profile = model.profile
+    assert isinstance(profile, OpenAIModelProfile)
+    assert profile.json_schema_transformer == InlineDefsJsonSchemaTransformer
+    assert OpenAIModelProfile.from_profile(profile).openai_chat_supports_web_search is False
+
+    # Test GPT-OSS model
+    model = CerebrasModel('gpt-oss-120b', provider=provider)
+    profile = model.profile
+    assert isinstance(profile, OpenAIModelProfile)
+    assert profile.json_schema_transformer == OpenAIJsonSchemaTransformer
+    assert OpenAIModelProfile.from_profile(profile).openai_chat_supports_web_search is False
+
+    # Test unknown model - use zai-glm which is valid but won't match any prefix
+    model = CerebrasModel('zai-glm-4.6', provider=provider)
+    profile = model.profile
+    assert isinstance(profile, OpenAIModelProfile)
+    assert OpenAIModelProfile.from_profile(profile).openai_chat_supports_web_search is False
+
+
+def test_cerebras_provider_need_api_key(env: TestEnv) -> None:
+    env.remove('CEREBRAS_API_KEY')
+    with pytest.raises(
+        UserError,
+        match=re.escape(
+            'Set the `CEREBRAS_API_KEY` environment variable or pass it via `CerebrasProvider(api_key=...)` '
+            'to use the Cerebras provider.'
+        ),
+    ):
+        CerebrasProvider()
+
+
+def test_cerebras_provider_pass_openai_client() -> None:
+    openai_client = AsyncOpenAI(api_key='test_key', base_url='https://api.cerebras.ai/v1')
+    provider = CerebrasProvider(openai_client=openai_client)
+    assert provider.client == openai_client