39e1831e84 Emit native web_search_tool_result blocks for Anthropic clients (Claude Desktop / Cowork citations) (#27886)
* feat(custom_logger): add async_post_agentic_loop_response_hook

Lets a CustomLogger shape the response returned by the agentic-loop
follow-up call without bypassing the loop's safety / observability
machinery (depth tracking, fingerprinting, etc.). Default returns the
response unchanged.

Used by websearch_interception to inject Anthropic-native
web_search_tool_result blocks when the originating client requested a
native web_search_* tool.

* feat(llm_http_handler): call post-agentic-loop hook on the originating callback

In _execute_anthropic_agentic_plan, after anthropic_messages.acreate
returns, call the originating callback's
async_post_agentic_loop_response_hook so it can mutate the final
response (e.g. inject native tool_result blocks). Pass the callback
through from _call_agentic_completion_hooks.

Exceptions in the post-hook are caught and logged so a buggy callback
can't kill the request.

* feat(websearch_interception): add is_anthropic_native_web_search_tool

Identifies tools the Anthropic-native clients (Claude Desktop, the
Anthropic SDK, the Anthropic Console) use to request native search:
type starts with "web_search_" (e.g. web_search_20250305). Rejects the
LiteLLM standard tool, the OpenAI-function variant, the bare
"WebSearch" legacy name, and the bare "web_search" Claude Code shape.

This lets us decide per-request whether the client expects
web_search_tool_result content blocks in the response, without
renaming any existing constants or touching native-provider skip
logic.

* feat(websearch_interception): add build_web_search_tool_result_block

Produces the Anthropic-native web_search_tool_result content block
from a structured SearchResponse. Anthropic-native clients use this
block to populate citations / source links — the existing text-blob
flatten path only feeds readable evidence to the model and discards
the structure, so this builder gives us the missing piece.

Shape matches https://docs.anthropic.com/en/api/web-search-tool —
web_search_result items carry url, title, page_age, encrypted_content
(empty string when the search provider doesn't supply one).

* feat(websearch_interception): emit native web_search_tool_result blocks

When the originating client request carried a native Anthropic
web_search_* tool, the final response now also carries
web_search_tool_result content blocks alongside the model's text
answer — so Claude Desktop / Anthropic SDK clients can populate the
citations panel and replay conversation history with structured search
evidence.

Wiring:
- Pre-request hooks (both deployment + Anthropic path) set a flag on
  kwargs when they see a native web_search_* tool, so the signal
  survives the conversion-to-litellm_web_search step regardless of
  which hook fires first.
- _execute_search now returns (text, SearchResponse) so the structured
  results aren't lost when the text is flattened for the follow-up
  model call.
- _build_anthropic_request_patch returns the parallel list of
  SearchResponse objects.
- async_build_agentic_loop_plan pre-builds the web_search_tool_result
  blocks (one per tool_use_id) and stashes them on plan.metadata when
  the flag is set.
- async_post_agentic_loop_response_hook reads the metadata and
  prepends the blocks to response.content.
- _execute_agentic_loop mirrors the injection for the legacy path so
  both paths behave identically.

Clients that send the LiteLLM standard tool keep the existing
text-only behavior — no regression.

* test(websearch_interception): cover native web_search_tool_result emission

18 tests across:
- detector branches (native vs litellm-standard, OpenAI-function shape,
  Claude Desktop builtin WebSearch, bare web_search, missing type)
- block-builder shape (results, none, empty)
- pre-request hook flag-setting (native sets, standard does not)
- async_build_agentic_loop_plan attaches blocks to plan.metadata when
  the flag is present, leaves metadata untouched when absent
- post-hook injection into dict and object responses
- legacy _execute_agentic_loop mirrors the injection so both paths
  return the same shape

* test(websearch_short_circuit): keep _execute_search mocks in sync with new tuple return

* test(websearch_thinking_constraint): keep _execute_search mocks in sync with new tuple return

* feat(websearch_interception): emit native blocks from try_short_circuit_search

The agentic-loop post-hook only fires when the model returns a tool_use
block. Cowork / Claude Desktop on Bedrock actually make TWO requests
per user turn: the main /v1/messages with their builtin tool, and a
separate standalone /v1/messages whose only tool is
web_search_20250305. That second request hits try_short_circuit_search
— no agentic loop, no post-hook — and was returning text-only, leaving
the citations panel empty.

When the short-circuit input carries a native web_search_* tool, build
a synthetic server_tool_use + web_search_tool_result pair (using the
structured SearchResponse already returned by _execute_search) so the
client gets the native shape it expects. The legacy text block is
preserved so non-native short-circuit callers (Claude Code,
github_copilot, etc.) see the same payload as before.

Failure path still emits the native block pair (with empty results)
plus the text-error block, so the client gets a well-formed response
rather than a malformed half-shape.

* test(websearch_native_blocks): cover short-circuit native-block emission

Three new cases on top of the existing 18:
- native web_search_20250305 short-circuit → [server_tool_use,
  web_search_tool_result, text], ids paired, urls/titles carried.
- litellm_web_search short-circuit → text-only (no regression).
- native short-circuit on search failure → still emits the native
  block pair (empty results) plus the text-error block, so the client
  never sees a malformed half-shape.

* test(websearch_short_circuit): index assertions by block type, not by position

Native short-circuit responses now have [server_tool_use,
web_search_tool_result, text] when the input carries
web_search_20250305 — find the text block by type rather than relying
on content[0].

* fix(websearch_interception): gate legacy WebSearch name on schema absence

Clients like Cowork / Claude Desktop ship a client-side tool named
"WebSearch" with a full input_schema — they handle it themselves and
expect to make a separate native web_search_20250305 sub-request for
the actual search.

Today is_web_search_tool matches the bare name regardless of other
fields, which hijacks the client's tool server-side. The agentic loop
fires on the main request, the model never gets to emit the
client-side tool_use, and the separate native sub-request (where
citation data flows) is never made. Net: citations panel empty.

Real Anthropic client tools always carry input_schema (the API rejects
them otherwise), so a bare {name: "WebSearch"} with no schema is the
only thing that could be a legacy interception marker. Gate the match
on schema absence: legacy callers (if any) keep working, real
client-side WebSearch tools pass through untouched.

* fix(websearch_interception): drop "WebSearch" from response-detection lists

Post-conversion the model always sees ``litellm_web_search``, so the
"WebSearch" entry in the response-side tool_use detection lists was
dead at best. If a model ever did return ``tool_use(name="WebSearch")``
it would now (incorrectly) hijack the client's own ``WebSearch`` tool
again — same Cowork problem we just fixed on the input side. Drop it.

* test(websearch_native_blocks): cover the WebSearch legacy-name schema gate

Three new cases:
- {name: "WebSearch"} (bare interception marker) → still matched
- {name: "WebSearch", input_schema: {...}} (Cowork client tool) →
  passes through untouched
- {name: "WebSearch", description: "..."} (no schema) → still matched
  on the assumption it's a legacy marker rather than a malformed real
  client tool.

---------

Co-authored-by: Ishaan Jaffer <ishaanjaffer0324@gmail.com>
2026-05-14 12:30:47 -07:00
2025-11-01 12:58:39 -07:00
2023-08-31 16:58:54 -07:00
2024-02-15 12:54:13 -08:00
2026-03-31 13:13:18 -07:00
2026-05-13 21:51:29 -07:00

🚅 LiteLLM

LiteLLM AI Gateway

Open Source AI Gateway for 100+ LLMs. Self-hosted. Enterprise-ready. Call any LLM in OpenAI format.

Deploy to Render Deploy on Railway

LiteLLM Proxy Server (AI Gateway) | Hosted Proxy | Enterprise Tier | Website

PyPI Version GitHub Stars Y Combinator W23 Whatsapp Discord Slack CodSpeed

Group 7154 (1)

What is LiteLLM

LiteLLM is an open source AI Gateway that gives you a single, unified interface to call 100+ LLM providers — OpenAI, Anthropic, Gemini, Bedrock, Azure, and more — using the OpenAI format.

Use it as a Python SDK for direct library integration, or deploy the AI Gateway (Proxy Server) as a centralized service for your team or organization.

Jump to LiteLLM Proxy (LLM Gateway) Docs
Jump to Supported LLM Providers


Why LiteLLM

Managing LLM calls across providers gets complicated fast — different SDKs, auth patterns, request formats, and error types for every model. LiteLLM removes that friction:

  • Unified API — one interface for 100+ LLMs, no provider-specific SDK juggling
  • Drop-in OpenAI compatibility — swap providers without rewriting your code
  • Production-ready gateway — virtual keys, spend tracking, guardrails, load balancing, and an admin dashboard out of the box
  • 8ms P95 latency at 1k RPS (benchmarks)

OSS Adopters

Stripe image Google ADK Greptile OpenHands

Netflix

OpenAI Agents SDK

Features

LLMs - Call 100+ LLMs (Python SDK + AI Gateway)

All Supported Endpoints - /chat/completions, /responses, /embeddings, /images, /audio, /batches, /rerank, /a2a, /messages and more.

Python SDK

uv add litellm
from litellm import completion
import os

os.environ["OPENAI_API_KEY"] = "your-openai-key"
os.environ["ANTHROPIC_API_KEY"] = "your-anthropic-key"

# OpenAI
response = completion(model="openai/gpt-4o", messages=[{"role": "user", "content": "Hello!"}])

# Anthropic  
response = completion(model="anthropic/claude-sonnet-4-20250514", messages=[{"role": "user", "content": "Hello!"}])

AI Gateway (Proxy Server)

Getting Started - E2E Tutorial - Setup virtual keys, make your first request

uv tool install 'litellm[proxy]'
litellm --model gpt-4o
import openai

client = openai.OpenAI(api_key="anything", base_url="http://0.0.0.0:4000")
response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Hello!"}]
)

Docs: LLM Providers

Agents - Invoke A2A Agents (Python SDK + AI Gateway)

Supported Providers - LangGraph, Vertex AI Agent Engine, Azure AI Foundry, Bedrock AgentCore, Pydantic AI

Python SDK - A2A Protocol

from litellm.a2a_protocol import A2AClient
from a2a.types import SendMessageRequest, MessageSendParams
from uuid import uuid4

client = A2AClient(base_url="http://localhost:10001")

request = SendMessageRequest(
    id=str(uuid4()),
    params=MessageSendParams(
        message={
            "role": "user",
            "parts": [{"kind": "text", "text": "Hello!"}],
            "messageId": uuid4().hex,
        }
    )
)
response = await client.send_message(request)

AI Gateway (Proxy Server)

Step 1. Add your Agent to the AI Gateway

Step 2. Call Agent via A2A SDK

from a2a.client import A2ACardResolver, A2AClient
from a2a.types import MessageSendParams, SendMessageRequest
from uuid import uuid4
import httpx

base_url = "http://localhost:4000/a2a/my-agent"  # LiteLLM proxy + agent name
headers = {"Authorization": "Bearer sk-1234"}    # LiteLLM Virtual Key

async with httpx.AsyncClient(headers=headers) as httpx_client:
    resolver = A2ACardResolver(httpx_client=httpx_client, base_url=base_url)
    agent_card = await resolver.get_agent_card()
    client = A2AClient(httpx_client=httpx_client, agent_card=agent_card)

    request = SendMessageRequest(
        id=str(uuid4()),
        params=MessageSendParams(
            message={
                "role": "user",
                "parts": [{"kind": "text", "text": "Hello!"}],
                "messageId": uuid4().hex,
            }
        )
    )
    response = await client.send_message(request)

Docs: A2A Agent Gateway

MCP Tools - Connect MCP servers to any LLM (Python SDK + AI Gateway)

Python SDK - MCP Bridge

from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client
from litellm import experimental_mcp_client
import litellm

server_params = StdioServerParameters(command="python", args=["mcp_server.py"])

async with stdio_client(server_params) as (read, write):
    async with ClientSession(read, write) as session:
        await session.initialize()

        # Load MCP tools in OpenAI format
        tools = await experimental_mcp_client.load_mcp_tools(session=session, format="openai")

        # Use with any LiteLLM model
        response = await litellm.acompletion(
            model="gpt-4o",
            messages=[{"role": "user", "content": "What's 3 + 5?"}],
            tools=tools
        )

AI Gateway - MCP Gateway

Step 1. Add your MCP Server to the AI Gateway

Step 2. Call MCP tools via /chat/completions

curl -X POST 'http://0.0.0.0:4000/v1/chat/completions' \
  -H 'Authorization: Bearer sk-1234' \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "gpt-4o",
    "messages": [{"role": "user", "content": "Summarize the latest open PR"}],
    "tools": [{
      "type": "mcp",
      "server_url": "litellm_proxy/mcp/github",
      "server_label": "github_mcp",
      "require_approval": "never"
    }]
  }'

Use with Cursor IDE

{
  "mcpServers": {
    "LiteLLM": {
      "url": "http://localhost:4000/mcp/",
      "headers": {
        "x-litellm-api-key": "Bearer sk-1234"
      }
    }
  }
}

Docs: MCP Gateway

Supported Providers (Website Supported Models | Docs)

Provider /chat/completions /messages /responses /embeddings /image/generations /audio/transcriptions /audio/speech /moderations /batches /rerank
Abliteration (abliteration)
AI/ML API (aiml)
AI21 (ai21)
AI21 Chat (ai21_chat)
Aleph Alpha
Amazon Nova
Anthropic (anthropic)
Anthropic Text (anthropic_text)
Anyscale
AssemblyAI (assemblyai)
Auto Router (auto_router)
AWS - Bedrock (bedrock)
AWS - Sagemaker (sagemaker)
Azure (azure)
Azure AI (azure_ai)
Azure Text (azure_text)
Baseten (baseten)
Bytez (bytez)
Cerebras (cerebras)
Clarifai (clarifai)
Cloudflare AI Workers (cloudflare)
Codestral (codestral)
Cohere (cohere)
Cohere Chat (cohere_chat)
CometAPI (cometapi)
CompactifAI (compactifai)
Custom (custom)
Custom OpenAI (custom_openai)
Dashscope (dashscope)
Databricks (databricks)
DataRobot (datarobot)
Deepgram (deepgram)
DeepInfra (deepinfra)
Deepseek (deepseek)
ElevenLabs (elevenlabs)
Empower (empower)
Fal AI (fal_ai)
Featherless AI (featherless_ai)
Fireworks AI (fireworks_ai)
FriendliAI (friendliai)
Galadriel (galadriel)
GitHub Copilot (github_copilot)
GitHub Models (github)
Google - PaLM
Google - Vertex AI (vertex_ai)
Google AI Studio - Gemini (gemini)
GradientAI (gradient_ai)
Groq AI (groq)
Heroku (heroku)
Hosted VLLM (hosted_vllm)
Huggingface (huggingface)
Hyperbolic (hyperbolic)
IBM - Watsonx.ai (watsonx)
Infinity (infinity)
Jina AI (jina_ai)
Lambda AI (lambda_ai)
Lemonade (lemonade)
LiteLLM Proxy (litellm_proxy)
Llamafile (llamafile)
LM Studio (lm_studio)
Maritalk (maritalk)
Meta - Llama API (meta_llama)
Mistral AI API (mistral)
Moonshot (moonshot)
Morph (morph)
Nebius AI Studio (nebius)
NLP Cloud (nlp_cloud)
Novita AI (novita)
Nscale (nscale)
Nvidia NIM (nvidia_nim)
OCI (oci)
Ollama (ollama)
Ollama Chat (ollama_chat)
Oobabooga (oobabooga)
OpenAI (openai)
OpenAI-like (openai_like)
OpenRouter (openrouter)
OVHCloud AI Endpoints (ovhcloud)
Perplexity AI (perplexity)
Petals (petals)
Predibase (predibase)
Recraft (recraft)
Replicate (replicate)
Sagemaker Chat (sagemaker_chat)
Sambanova (sambanova)
Snowflake (snowflake)
Text Completion Codestral (text-completion-codestral)
Text Completion OpenAI (text-completion-openai)
Together AI (together_ai)
Topaz (topaz)
Triton (triton)
V0 (v0)
Vercel AI Gateway (vercel_ai_gateway)
VLLM (vllm)
Volcengine (volcengine)
Voyage AI (voyage)
WandB Inference (wandb)
Watsonx Text (watsonx_text)
xAI (xai)
Xinference (xinference)

Read the Docs


Get Started

You can use LiteLLM through either the Proxy Server or Python SDK. Both give you a unified interface to access multiple LLMs (100+ LLMs). Choose the option that best fits your needs:

LiteLLM AI Gateway LiteLLM Python SDK
Use Case Central service (LLM Gateway) to access multiple LLMs Use LiteLLM directly in your Python code
Who Uses It? Gen AI Enablement / ML Platform Teams Developers building LLM projects
Key Features Centralized API gateway with authentication and authorization, multi-tenant cost tracking and spend management per project/user, per-project customization (logging, guardrails, caching), virtual keys for secure access control, admin dashboard UI for monitoring and management Direct Python library integration in your codebase, Router with retry/fallback logic across multiple deployments (e.g. Azure/OpenAI) - Router, application-level load balancing and cost tracking, exception handling with OpenAI-compatible errors, observability callbacks (Lunary, MLflow, Langfuse, etc.)

Stable Release: Use docker images with the -stable tag. These have undergone 12 hour load tests, before being published. More information about the release cycle here

Support for more providers. Missing a provider or LLM Platform, raise a feature request.

Run in Developer Mode

Services

  1. Setup .env file in root
  2. Run dependant services docker-compose up db prometheus

Backend

  1. (In root) create virtual environment python -m venv .venv
  2. Activate virtual environment source .venv/bin/activate
  3. Install dependencies uv sync --all-extras --group proxy-dev
  4. uv run prisma generate
  5. prisma generate
  6. Start proxy backend python litellm/proxy/proxy_cli.py

Frontend

  1. Navigate to ui/litellm-dashboard
  2. Install dependencies npm install
  3. Run npm run dev to start the dashboard

Verify Docker Image Signatures

All LiteLLM Docker images published to GHCR are signed with cosign. Every release is signed with the same key introduced in commit 0112e53.

Verify using the pinned commit hash (recommended):

A commit hash is cryptographically immutable, so this is the strongest way to ensure you are using the original signing key:

cosign verify \
  --key https://raw.githubusercontent.com/BerriAI/litellm/0112e53046018d726492c814b3644b7d376029d0/cosign.pub \
  ghcr.io/berriai/litellm:<release-tag>

Verify using a release tag (convenience):

Tags are protected in this repository and resolve to the same key. This option is easier to read but relies on tag protection rules:

cosign verify \
  --key https://raw.githubusercontent.com/BerriAI/litellm/<release-tag>/cosign.pub \
  ghcr.io/berriai/litellm:<release-tag>

Replace <release-tag> with the version you are deploying (e.g. v1.83.0-stable).


Enterprise

For companies that need better security, user management and professional support

Get an Enterprise License Talk to founders

This covers:

  • Features under the LiteLLM Commercial License:
  • Feature Prioritization
  • Custom Integrations
  • Professional Support - Dedicated discord + slack
  • Custom SLAs
  • Secure access with Single Sign-On

Contributing

We welcome contributions to LiteLLM! Whether you're fixing bugs, adding features, or improving documentation, we appreciate your help.

Quick Start for Contributors

This requires uv to be installed.

git clone https://github.com/BerriAI/litellm.git
cd litellm
make install-dev    # Install development dependencies
make format         # Format your code
make lint           # Run all linting checks
make test-unit      # Run unit tests
make format-check   # Check formatting only

For detailed contributing guidelines, see CONTRIBUTING.md.

📖 Contributing to documentation? The LiteLLM docs have moved to a separate repository: BerriAI/litellm-docs. Please open doc PRs there. Docs are served at docs.litellm.ai.

Code Quality / Linting

LiteLLM follows the Google Python Style Guide.

Our automated checks include:

  • Black for code formatting
  • Ruff for linting and code quality
  • MyPy for type checking
  • Circular import detection
  • Import safety checks

All these checks must pass before your PR can be merged.

Support / talk with founders

Contributors

S
Description
Python SDK, Proxy Server (AI Gateway) to call 100+ LLM APIs in OpenAI (or native) format, with cost tracking, guardrails, loadbalancing and logging. [Bedrock, Azure, OpenAI, VertexAI, Cohere, Anthropic, Sagemaker, HuggingFace, VLLM, NVIDIA NIM]
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1.1 GiB
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Python 81%
TypeScript 12.2%
JavaScript 5.9%
HTML 0.5%
HCL 0.2%