@@ -6,7 +6,7 @@
 import logging
 from collections.abc import Iterable, Sequence
 from itertools import chain
-from typing import Any, TypedDict
+from typing import Any, Literal, TypedDict
 
 import httpx2
 from anthropic import NOT_GIVEN, AsyncAnthropic
@@ -78,6 +78,9 @@ def _message_usage(message: Message) -> Usage:
     return normalize_usage(message.usage.model_dump() if message.usage else {})
 
 
+Speed = Literal["standard", "fast"]
+
+
 class CreateOptions(TypedDict, total=False):
     # `temperature`, `top_p` and `top_k` are absent on purpose: `anthropic` 1.x
     # removed them from the Messages API signature, so passing one here is a
@@ -89,6 +92,7 @@ class CreateOptions(TypedDict, total=False):
     stream: bool
     metadata: dict[str, str] | None
     service_tier: str | None
+    speed: Speed | None
 
 
 class AnthropicClient(LLMClient):
 
@@ -11,7 +11,7 @@
 
 from ag2.config.config import ModelConfig, ModelProvider
 
-from .anthropic_client import AnthropicClient, CreateOptions
+from .anthropic_client import AnthropicClient, CreateOptions, Speed
 from .files import AnthropicFilesClient
 from .mappers import SAMPLING_FIELDS, merge_sampling_into_extra_body
 
@@ -35,6 +35,7 @@ class AnthropicConfigOverrides(TypedDict, total=False):
     prompt_caching: bool
     cache_diagnostics: bool
     extra_body: dict[str, Any] | None
+    speed: Speed | None
 
 
 @dataclass(slots=True)
@@ -57,6 +58,8 @@ class AnthropicConfig(ModelConfig):
     prompt_caching: bool = True
     cache_diagnostics: bool = False
     extra_body: dict[str, Any] | None = None
+    speed: Speed | None = None
+    """Inference speed; some models require a fast-mode beta header for either value."""
 
     @property
     def provider(self) -> ModelProvider:
@@ -78,6 +81,8 @@ def create(self) -> AnthropicClient:
             options["metadata"] = self.metadata
         if self.service_tier is not None:
             options["service_tier"] = self.service_tier
+        if self.speed is not None:
+            options["speed"] = self.speed
 
         return AnthropicClient(
             api_key=self.api_key,
 
@@ -88,7 +88,7 @@ ag-ui = ["ag-ui-protocol>=1.0,<2"]
 
 # === LLM providers (ag2.config) ===
 openai = ["openai>=3.27.0,<4"]
-anthropic = ["anthropic>=1.9.0,<2"]
+anthropic = ["anthropic>=1.15.0,<2"]
 gemini = [
     # Version bounds: local types in gemini_types.py are tested for subset compatibility
     # with the SDK (local can have extra fields for forward compatibility).
 
@@ -2,6 +2,10 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+from typing import Literal
+
+import pytest
+
 from ag2.config import AnthropicConfig
 from ag2.config.anthropic import AnthropicClient
 
@@ -48,6 +52,22 @@ def test_max_tokens_can_be_overridden() -> None:
     assert config.max_tokens == 8192
 
 
+def test_speed_defaults_to_none() -> None:
+    config = AnthropicConfig(model="claude-opus-5-5")
+    assert config.speed is None
+
+
+@pytest.mark.parametrize("speed", ["standard", "fast", None])
+def test_copy_with_speed(speed: Literal["standard", "fast"] | None) -> None:
+    config = AnthropicConfig(model="claude-opus-5-5", speed="fast")
+
+    copied = config.copy(speed=speed)
+
+    assert copied == AnthropicConfig(model="claude-opus-5-5", speed=speed)
+    assert config.speed == "fast"
+    assert copied is not config
+
+
 def test_extra_body_defaults_to_none() -> None:
     config = AnthropicConfig(model="claude-sonnet-5")
     assert config.extra_body is None
 
@@ -11,6 +11,7 @@
 """
 
 import json
+from typing import Literal
 
 import httpx2
 import pytest
@@ -123,6 +124,57 @@ async def test_sampling_fields_reach_the_api_when_streaming() -> None:
     assert captured["body"] == IsPartialDict({"temperature": 0.2, "stream": True})
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("streaming", [False, True])
+@pytest.mark.parametrize("speed", ["standard", "fast", None])
+async def test_speed_reaches_the_api_when_set(speed: Literal["standard", "fast"] | None, streaming: bool) -> None:
+    captured: dict[str, object] = {}
+    config = AnthropicConfig(
+        model="claude-opus-5-5",
+        api_key="test",
+        speed=speed,
+        streaming=streaming,
+        http_client=_capturing_client(captured, stream=streaming),
+    )
+
+    await _ask(config)
+
+    body = captured["body"]
+    assert isinstance(body, dict)
+    if speed is None:
+        assert "speed" not in body
+    else:
+        assert body == IsPartialDict({"speed": speed})
+    headers = captured["headers"]
+    assert isinstance(headers, httpx2.Headers)
+    assert "anthropic-beta" not in headers
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("streaming", [False, True])
+@pytest.mark.parametrize("speed", ["standard", "fast"])
+async def test_speed_preserves_the_users_beta_header_with_mcp(
+    context: Context, speed: Literal["standard", "fast"], streaming: bool
+) -> None:
+    captured: dict[str, object] = {}
+    config = AnthropicConfig(
+        model="claude-opus-5",
+        api_key="test",
+        speed=speed,
+        streaming=streaming,
+        default_headers={"Anthropic-Beta": "fast-mode-2026-02-01"},
+        http_client=_capturing_client(captured, stream=streaming),
+    )
+    schemas = await MCPServerTool(server_url="https://mcp.example.com/x", server_label="x").schemas(context)
+
+    await _ask(config, tools=schemas)
+
+    assert captured["body"] == IsPartialDict({"speed": speed})
+    headers = captured["headers"]
+    assert isinstance(headers, httpx2.Headers)
+    assert headers.get_list("anthropic-beta") == ["fast-mode-2026-02-01,mcp-client-2025-11-20"]
+
+
 @pytest.mark.asyncio
 async def test_user_extra_body_wins_over_a_sampling_field() -> None:
     captured: dict[str, object] = {}
 
@@ -77,7 +77,7 @@ config = AnthropicConfig(
 )
 ```
 
-`ag2[anthropic]` requires `anthropic>=1.6.0,<2`. See [Anthropic Configuration](#anthropic-configuration) for the `httpx2` HTTP client and the sampling parameters (`temperature`, `top_p`, `top_k`).
+`ag2[anthropic]` requires `anthropic>=1.15.0,<2`. See [Anthropic Configuration](#anthropic-configuration) for the `httpx2` HTTP client and the sampling parameters (`temperature`, `top_p`, `top_k`).
   </Tab>
 
   <Tab title="Gemini">
@@ -253,7 +253,7 @@ The model only returns its thinking when you set `summary`; without it the model
 
 ### Anthropic Configuration
 
-`AnthropicConfig` connects to the [Claude API](https://platform.claude.com/docs/en/build-with-claude/overview){.external-link target="_blank"} through the official `anthropic` SDK. Install the optional dependency with `pip install "ag2[anthropic]"`, which requires `anthropic>=1.6.0,<2`.
+`AnthropicConfig` connects to the [Claude API](https://platform.claude.com/docs/en/build-with-claude/overview){.external-link target="_blank"} through the official `anthropic` SDK. Install the optional dependency with `pip install "ag2[anthropic]"`, which requires `anthropic>=1.15.0,<2`.
 
 If `api_key` is not passed explicitly, it is resolved from the `ANTHROPIC_API_KEY` environment variable.
 
@@ -264,6 +264,24 @@ from ag2.config import AnthropicConfig
 config = AnthropicConfig(model="claude-haiku-4-5-20251001", streaming=True)
 ```
 
+#### Inference Speed
+
+Set `speed="fast"` or `speed="standard"` to select the inference speed on supported models. The default, `None`, omits the parameter and leaves the API's default behavior unchanged. The option works with both streaming and non-streaming requests, including `config.copy(speed="standard")` overrides.
+
+Some models require the `fast-mode-2026-02-01` beta header for **either** explicit value, including `"standard"`. AG2 does not add this model-specific header automatically; set it through `default_headers` when required:
+
+```python linenums="1"
+from ag2.config import AnthropicConfig
+
+config = AnthropicConfig(
+    model="claude-opus-5",
+    speed="fast",
+    default_headers={"anthropic-beta": "fast-mode-2026-02-01"},
+)
+```
+
+Caller-supplied beta headers are preserved when AG2 adds its own tool-related betas. See [Anthropic's fast-mode guide](https://platform.claude.com/docs/en/build-with-claude/fast-mode){.external-link target="_blank"} for current model availability, header requirements and pricing. Fast mode has premium pricing; enabling it does not make an unsupported model compatible.
+
 #### Custom HTTP Client
 
 `anthropic>=1` is built on [`httpx2`](https://pypi.org/project/httpx2/){.external-link target="_blank"}, so `http_client` takes an `#!python httpx2.AsyncClient`: