litellm - 💡(How to fix) Fix websearch_interception does not fire for Claude Code + Bedrock pass-through; PR #25242 would fix the root cause but introduces a new Bedrock skip that re-breaks it [1 comments, 2 participants]

Describe the bug

Routing Claude Code through LiteLLM to AWS Bedrock via ANTHROPIC_BASE_URL with websearch_interception configured, the interception short-circuit never fires. The web_search_20250305 tool is forwarded to Bedrock, which rejects it because Bedrock does not support that tool on any API path.

There are two related problems here, which I want to separate clearly:

Problem 1 (current, v1.83.7-stable): On main today, interception does not fire for Claude Code's web_search_20250305 request shape when routed through the Bedrock pass-through. This appears to be a tool-name / request-format compatibility gap — Claude Code sends the tool as {"type": "web_search_20250305", "name": "web_search"}, but the interception detection logic in current main doesn't recognize this as a search-only request that should be short-circuited. Related context in #21733 (adapter path) and #20179 (tool name detection on v1.81.3).

Problem 2 (pending, PR #25242): PR #25242 is attempting to fix the Claude Code compatibility gap — renaming the injected tool name to WebSearch, returning native Anthropic format (server_tool_use + web_search_tool_result), and adding streaming support for those block types. This would resolve Problem 1. However, commit 05ddb2e within that same PR ("Restore native provider skip for upstream compatibility") adds an unconditional skip for anthropic, bedrock, and vertex_ai, on the premise that these providers "handle web_search_20250305 natively." This premise is false for Bedrock.

If #25242 merges as currently structured, it will fix the Claude Code compatibility path but simultaneously make enabled_providers: [bedrock] a no-op — the very scenario the docs (Claude Code - WebSearch Across All Providers) explicitly advertise as supported.

Ground truth on Bedrock's support for web_search_20250305

Bedrock Converse rejects it with a validation error that enumerates accepted type tags:

tools.0: Input tag 'web_search_20250305' found using 'type' does not match
any of the expected tags: 'bash_20250124', 'custom', 'text_editor_20250124'

Sources:

• AWS re:Post — Web Search for Anthropic Models in Bedrock
• Anthropic tool search tool docs — confirms server-side tool support on Bedrock is limited to the invoke API, and web_search_20250305 is not listed for either invoke or Converse.
• AWS Bedrock Claude tool use documentation — the accepted Anthropic-defined tool types for Bedrock are bash_*, text_editor_*, and custom. web_search_20250305 is not listed.

To Reproduce

1. Set ANTHROPIC_BASE_URL pointing to a LiteLLM proxy backed by AWS Bedrock.
2. Configure websearch_interception with enabled_providers: [bedrock] and a search provider (SearXNG, Tavily, etc.).
3. Trigger a web search from Claude Code.
4. Observe: the web_search tool definition is forwarded to Bedrock unintercepted; Bedrock returns a 400.

Minimal config:

model_list:
  - model_name: claude-sonnet-4-5-20250929
    litellm_params:
      model: bedrock/us.anthropic.claude-sonnet-4-5-20250929-v1:0
      aws_region_name: us-east-1

litellm_settings:
  callbacks:
    - websearch_interception:
        enabled_providers: [bedrock]

search_tools:
  - search_tool_name: searxng-search
    litellm_params:
      search_provider: searxng
      api_base: http://searxng.internal:8080

Error surfaced through the proxy:

{"message":"The provided request is not valid"}. Received Model Group=claude-haiku-4-5-20251001
Available Model Group Fallbacks=None

Expected behavior

When enabled_providers includes bedrock, the interception short-circuit should execute for Bedrock-routed requests. Bedrock cannot handle web_search_20250305 natively on any API path, so the interception layer needs to run the search via the configured provider and return results in Anthropic-compatible format before the request reaches Bedrock.

Proposed fix

Two things need to both happen:

1. Land the Claude Code compatibility changes in #25242 (tool-name alignment, native-format response, streaming support for server_tool_use / web_search_tool_result blocks). These are correct and necessary.
2. In the same PR, narrow the native-provider skip introduced in commit 05ddb2e to anthropic only. Bedrock and Vertex AI should go through the interception path the same as other providers, since neither handles web_search_20250305 server-side. (I'm less certain about Vertex's current state — happy to be corrected there — but the Bedrock case is unambiguous from AWS's own error message.)

Environment

• LiteLLM version: v1.83.7-stable
• Client: Claude Code (via ANTHROPIC_BASE_URL → LiteLLM)
• Backend: AWS Bedrock (bedrock/us.anthropic.claude-sonnet-4-5-20250929-v1:0, claude-haiku-4-5-20251001-v1:0)

Related

• PR #25242 — the fix-in-progress and the source of the pending regression
• #21733 — adapter vs. base handler path distinction for agentic loop hooks
• #20179 — tool-name detection / spend tracking on v1.81.3
• #20187 — zero output tokens when interception does fire on Bedrock (pre-#25242)