fix: strip cache_breakpoint in LiteLLM path and expand Anthropic prefixes

[superShen0916]

Summary

Two small fixes to improve LLM provider routing robustness:

1. Strip cache_breakpoint in LiteLLM fallback path (Fixes #5886)

_format_messages_for_provider was not stripping cache_breakpoint flags before sending messages to providers through the LiteLLM path. This caused errors like:

GroqException - 'messages.0': property 'cache_breakpoint' is unsupported

BaseLLM._format_messages already handles this for native providers (OpenAI, Anthropic, etc.), but the LiteLLM fallback path uses its own method which missed this step. The fix strips the flag from message copies before they reach LiteLLM.

2. Expand Anthropic model prefix matching (Fixes #5893)

Added anthropic-- to the Anthropic model prefix list in _matches_provider_pattern. This allows custom deployments with names like anthropic--claude-sonnet-4 to be recognized as Anthropic models and routed to the native provider.

Changes

• lib/crewai/src/crewai/llm.py: Strip cache_breakpoint from message copies in _format_messages_for_provider (the LiteLLM fallback path) before provider-specific formatting
• lib/crewai/src/crewai/llm.py: Add anthropic-- to Anthropic model prefix detection

Test plan

• Existing tests pass: TestCacheMarkerHelpers, TestBaseFormatDoesNotMutate, TestNonAnthropicStripsMarker
• The message copy approach preserves caller message lists (no mutation) — consistent with the pattern used in BaseLLM._format_messages

Risk

Low. Changes are limited to stripping an internal-only flag from API-bound messages (already done in the native path) and expanding a prefix allowlist by one entry.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved Anthropic model compatibility with additional naming patterns.
  • Fixed cache marker handling in message preparation for improved provider request processing.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 55f2f543-aac8-4652-abfc-7e9d1641451a

📥 Commits

Reviewing files that changed from the base of the PR and between c3e2001 and 303d166.

📒 Files selected for processing (1)

• lib/crewai/src/crewai/llm.py

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📝 Walkthrough

Walkthrough

This PR expands Anthropic model prefix validation to support anthropic-- naming convention alongside existing claude- and anthropic. prefixes, and adds cache-breakpoint flag sanitization in LiteLLM message preparation to strip unsupported cache markers before sending requests to non-Anthropic providers.

Changes

LiteLLM Provider Compatibility

Layer / File(s)	Summary
Expanded Anthropic model prefix validation lib/crewai/src/crewai/llm.py	Anthropic/Claude provider matching logic now accepts an additional anthropic-- prefix alongside existing claude- and anthropic. prefixes.
Cache breakpoint sanitization for LiteLLM lib/crewai/src/crewai/llm.py	_format_messages_for_provider imports strip_cache_breakpoint, shallow-copies each message dict, and applies strip_cache_breakpoint to remove cache-breakpoint flags prior to provider-specific message handling.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A prefix grows from claude to bright,
Anthropic flags now stripped from sight,
Cache breakpoints fade without a trace,
LiteLLM finds its proper place!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the two main changes: stripping cache_breakpoint in the LiteLLM path and expanding Anthropic model name prefixes.
Linked Issues check	✅ Passed	The PR addresses both linked issues: it strips cache_breakpoint before sending to LiteLLM providers (#5886) and adds 'anthropic--' prefix to Anthropic model detection (#5893).
Out of Scope Changes check	✅ Passed	All changes in the PR are directly scoped to the two linked issues; no unrelated modifications were introduced.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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