feat(anthropic): support advisor_20260301 tool type by ishaan-berri · Pull Request #25525 · BerriAI/litellm

ishaan-berri · 2026-04-10T19:41:06Z

Relevant issues

Fixes #25516

Pre-Submission checklist

I have Added testing in the tests/test_litellm/ directory, Adding at least 1 test is a hard requirement - see details
My PR passes all unit tests on make test-unit
My PR's scope is as isolated as possible, it only solves 1 specific problem

CI (LiteLLM team)

Branch creation CI run
Link:
CI run for the last commit
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Merge / cherry-pick CI run
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Type

🆕 New Feature / 🐛 Bug Fix

Changes

Adds support for Anthropic's advisor_20260301 tool. Previously LiteLLM raised a ValueError on unknown tool types and stripped the beta header. This also adds auto-strip of stale advisor_tool_result blocks to prevent 400s on follow-up turns.

Files changed:

litellm/types/llms/anthropic.py — AnthropicAdvisorTool TypedDict + ADVISOR_TOOL_2026_03_01 enum value
litellm/llms/anthropic/chat/transformation.py — handle advisor_20260301 in _map_tool_helper(); auto-inject beta header; auto-strip advisor blocks when tool is absent
litellm/llms/anthropic/experimental_pass_through/messages/transformation.py — same auto-inject + auto-strip for /v1/messages path
litellm/llms/anthropic/common_utils.py — strip_advisor_blocks_from_messages() helper
litellm/anthropic_beta_headers_config.json — register advisor-tool-2026-03-01 so the beta headers manager forwards it (was silently dropped)
docs/my-website/docs/providers/anthropic_advisor_tool.md — new doc page

Auto-strip behavior: When the advisor tool is not in tools, LiteLLM strips server_tool_use(name=advisor) and advisor_tool_result blocks from message history before forwarding. This prevents the Anthropic 400 that happens when a caller removes the advisor tool for cost control but forgets to clean history.

Live test results (both paths, both modes):

/v1/messages non-streaming:

[server_tool_use] name=advisor, id=srvtoolu_016tba5RDoFRrti7ycatWiLV
[advisor_tool_result] tool_use_id=srvtoolu_016tba5RDoFRrti7ycatWiLV
[text] Here is an efficient Python primality check...
usage: 2223 in / 635 out

/v1/messages streaming:

[server_tool_use] name=advisor, id=srvtoolu_01HS2LKg3iGsCL3kRtZLoYbV
[advisor_tool_result] tool_use_id=srvtoolu_01HS2LKg3iGsCL3kRtZLoYbV
[text] Here is an efficient Python function to check if a number is prime...

10 unit tests in tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py.

…03_01 beta header enum

…r beta header

…ader in /messages path

Add advisor-tool-2026-03-01 to anthropic_beta_headers_config.json so the beta headers manager forwards it to Anthropic (was being silently dropped). Mark as null for all non-native providers.

vercel · 2026-04-10T19:41:16Z

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CLAassistant · 2026-04-10T19:41:18Z

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

codspeed-hq · 2026-04-10T19:43:09Z

Merging this PR will not alter performance

✅ 16 untouched benchmarks

_{Comparing feat/anthropic-advisor-tool (9897c6d) with main (d67b5f8)}

codecov · 2026-04-10T19:44:52Z

Codecov Report

❌ Patch coverage is 95.38462% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
litellm/llms/anthropic/chat/transformation.py	92.59%	2 Missing ⚠️
litellm/llms/anthropic/common_utils.py	94.73%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

greptile-apps · 2026-04-10T19:50:02Z

Greptile Summary

This PR adds support for Anthropic's advisor_20260301 tool type across both the Chat Completions and /v1/messages paths, including automatic injection of the advisor-tool-2026-03-01 beta header and a new strip_advisor_blocks_from_messages() helper that scrubs stale advisor blocks from message history when the advisor tool is absent (preventing Anthropic 400s on follow-up turns). The implementation is thorough — TypedDict, enum value, JSON config, and two transformation paths are all updated together — and 10 unit tests cover the main scenarios.

Confidence Score: 5/5

Safe to merge — the single remaining finding is a P2 edge case that requires a caller to explicitly pass unsupported fields on an advisor tool.

All changes are isolated to the Anthropic provider directory, 10 new unit tests cover the main code paths without network calls, both transformation paths are handled consistently, and no security or data-integrity issues were found. The only open concern (advisor tool not excluded from cache_control/defer_loading/allowed_callers processing) only triggers if a caller deliberately passes unsupported fields on an advisor tool and does not affect the primary use case.

litellm/llms/anthropic/chat/transformation.py — the three post-build processing blocks (cache_control, defer_loading, allowed_callers) should exclude ANTHROPIC_ADVISOR_TOOL_TYPE.

Important Files Changed

Filename	Overview
litellm/llms/anthropic/chat/transformation.py	Core transformation path: adds advisor tool handling in `_map_tool_helper`, auto-beta-header injection, and auto-strip of advisor blocks; advisor tool type is not excluded from `cache_control`/`defer_loading`/`allowed_callers` processing blocks, which can silently forward unsupported fields.
litellm/llms/anthropic/common_utils.py	Adds `strip_advisor_blocks_from_messages()` helper — logic is correct, strips `server_tool_use(name=advisor)` and associated `advisor_tool_result` blocks from assistant message content.
litellm/llms/anthropic/experimental_pass_through/messages/transformation.py	Messages pass-through path: mirrors the chat path with advisor beta-header injection and auto-strip; implementation is consistent with the chat path.
litellm/types/llms/anthropic.py	Adds `AnthropicAdvisorTool` TypedDict, `ANTHROPIC_ADVISOR_TOOL_TYPE` constant, `ADVISOR_TOOL_2026_03_01` enum value, and includes `AnthropicAdvisorTool` in `AllAnthropicToolsValues` union — all correct.
tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py	10 new unit tests covering tool mapping, beta-header injection, response parsing, and message stripping — all are pure mock/unit tests with no network calls.
litellm/anthropic_beta_headers_config.json	Registers `advisor-tool-2026-03-01` in the beta headers config so it is forwarded by the headers manager — correct addition.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Incoming request with tools] --> B{advisor_20260301\nin tools?}
    B -- Yes --> C[Auto-inject\nadvisor-tool-2026-03-01\nbeta header]
    B -- No --> D[strip_advisor_blocks_from_messages\nscan assistant history]
    D --> E{Advisor blocks\nfound in history?}
    E -- Yes --> F[Remove server_tool_use name=advisor\n+ matching advisor_tool_result blocks]
    E -- No --> G[No-op]
    C --> H[_map_tool_helper:\nAnthropicAdvisorTool TypedDict\nwith type/name/model/max_uses/caching]
    H --> I[Forward to Anthropic API]
    F --> I
    G --> I

_{Reviews (4): Last reviewed commit: "refactor(advisor): replace hardcoded "ad..." | Re-trigger Greptile}

greptile-apps · 2026-04-10T19:50:05Z

+                    break
+
        # Check for tool search tools
        tools = optional_params.get("tools")


Redundant tools fetch

tools is fetched from optional_params again here (line 338) even though it was already assigned at line 328 and its value hasn't changed. The existing reference can be reused directly.

Suggested change

tools = optional_params.get("tools")

# Check for tool search tools

if tools:

greptile-apps · 2026-04-10T19:50:06Z

                name=tool_name,
            )
+        elif tool["type"] == "advisor_20260301":
+            from litellm.types.llms.anthropic import AnthropicAdvisorTool


Inline import inside method

AnthropicAdvisorTool is imported inside the method body rather than at the module top-level. CLAUDE.md asks to avoid inline imports unless they are strictly needed to break a circular dependency. AnthropicAdvisorTool lives in the same litellm.types.llms.anthropic module that is already imported at the top of this file (line 21), so it can be added there instead — the same way AnthropicMessagesTool, AnthropicComputerTool, etc. are imported. The same pattern exists at lines 489 and 501 for the tool-search types; all three could be moved up together.

Context Used: CLAUDE.md (source)

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

greptile-apps · 2026-04-10T19:50:07Z

+            advisor_model = _tool_dict.get("model")
+            if not isinstance(advisor_model, str):
+                raise ValueError("Advisor tool must have a valid model")


Empty-string model passes validation

isinstance("", str) is True, so passing "model": "" will bypass the guard and produce an AnthropicAdvisorTool with an empty model field. Anthropic will reject the request, but the error message will be cryptic. A simple additional check makes the failure fast and clear:

Suggested change

advisor_model = _tool_dict.get("model")

if not isinstance(advisor_model, str):

raise ValueError("Advisor tool must have a valid model")

advisor_model = _tool_dict.get("model")

if not isinstance(advisor_model, str) or not advisor_model.strip():

raise ValueError("Advisor tool must have a valid model")

…l absent Prevents Anthropic 400 invalid_request_error on follow-up turns where the caller has removed the advisor tool but message history still contains server_tool_use(advisor) + advisor_tool_result blocks.

…m_request


-from ..common_utils import AnthropicError, AnthropicModelInfo, process_anthropic_headers
+from ..common_utils import (
+    AnthropicError,


-from ..common_utils import AnthropicError, AnthropicModelInfo, process_anthropic_headers
+from ..common_utils import (
+    AnthropicError,
+    AnthropicModelInfo,


+from ..common_utils import (
+    AnthropicError,
+    AnthropicModelInfo,
+    process_anthropic_headers,


+    AnthropicError,
+    AnthropicModelInfo,
+    process_anthropic_headers,
+    strip_advisor_blocks_from_messages,


…C_ADVISOR_TOOL_TYPE constant

 from litellm.llms.base_llm.base_utils import type_to_response_format_param
 from litellm.llms.base_llm.chat.transformation import BaseConfig, BaseLLMException
 from litellm.types.llms.anthropic import (
+    ANTHROPIC_ADVISOR_TOOL_TYPE,


ishaan-berri added 6 commits April 10, 2026 12:39

feat(anthropic): add AnthropicAdvisorTool type and ADVISOR_TOOL_2026_…

506de45

…03_01 beta header enum

feat(anthropic): support advisor_20260301 tool and auto-inject adviso…

a30a538

…r beta header

test(anthropic): add advisor tool transformation tests

0f9eba4

feat(anthropic/messages): auto-inject advisor-tool-2026-03-01 beta he…

ed4aa84

…ader in /messages path

test(anthropic): add advisor tool tests for /messages beta header path

55f0e66

feat(anthropic): register advisor-tool-2026-03-01 in beta headers config

91f6d49

Add advisor-tool-2026-03-01 to anthropic_beta_headers_config.json so the beta headers manager forwards it to Anthropic (was being silently dropped). Mark as null for all non-native providers.

vercel bot deployed to Preview April 10, 2026 19:42 View deployment

greptile-apps bot reviewed Apr 10, 2026

View reviewed changes

ishaan-berri added 5 commits April 10, 2026 13:15

feat(advisor): auto-strip advisor_tool_result blocks when advisor too…

3a89465

…l absent Prevents Anthropic 400 invalid_request_error on follow-up turns where the caller has removed the advisor tool but message history still contains server_tool_use(advisor) + advisor_tool_result blocks.

feat(advisor): call strip_advisor_blocks in chat/completions transfor…

ab8d92c

…m_request

feat(advisor): call strip_advisor_blocks in /messages transform path

9742bcd

test(advisor): add tests for auto-strip advisor_tool_result blocks

318196f

docs: add Advisor Tool documentation page

ed973c0

vercel bot deployed to Preview April 10, 2026 20:17 View deployment

github-advanced-security AI found potential problems Apr 10, 2026

View reviewed changes

docs: move advisor tool doc to completion/ guides section in sidebar

d6e2a74

vercel bot deployed to Preview April 10, 2026 22:10 View deployment

refactor(advisor): replace hardcoded "advisor_20260301" with ANTHROPI…

9897c6d

…C_ADVISOR_TOOL_TYPE constant

vercel bot deployed to Preview April 10, 2026 23:01 View deployment

github-advanced-security AI found potential problems Apr 10, 2026

View reviewed changes

Comment thread litellm/llms/anthropic/chat/transformation.py

from litellm.llms.base_llm.base_utils import type_to_response_format_param

from litellm.llms.base_llm.chat.transformation import BaseConfig, BaseLLMException

from litellm.types.llms.anthropic import (

ANTHROPIC_ADVISOR_TOOL_TYPE,

ishaan-berri changed the base branch from main to litellm_ishaan_april10 April 10, 2026 23:39

ishaan-berri merged commit 831083b into litellm_ishaan_april10 Apr 10, 2026
49 of 51 checks passed

ishaan-berri deleted the feat/anthropic-advisor-tool branch April 10, 2026 23:39

ishaan-berri mentioned this pull request Apr 10, 2026

feat(advisor): Anthropic Claude Code /advisor rollout #25516

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feat(anthropic): support advisor_20260301 tool type#25525

feat(anthropic): support advisor_20260301 tool type#25525
ishaan-berri merged 13 commits intolitellm_ishaan_april10from
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	tools = optional_params.get("tools")
	# Check for tool search tools
	if tools:

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Confidence Score: 5/5

Important Files Changed

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