feat: add Xiaomi MiMo Anthropic-compatible endpoint support for thinking mode

[comeonzhj]

Summary

Add support for Xiaomi MiMo's Anthropic-compatible endpoint (/anthropic) for thinking mode. This fix resolves HTTP 400 errors when using Xiaomi MiMo models with thinking/reasoning enabled.

Problem

When using Xiaomi MiMo model (mimo-v2.5-pro) via Anthropic-compatible endpoint (https://token-plan-cn.xiaomimimo.com/anthropic), enabling thinking mode causes HTTP 400 error:

HTTP 400: Param Incorrect
The reasoning_content in the thinking mode must be passed back to the API.

Root Cause

Xiaomi's /anthropic endpoint, like Kimi and DeepSeek, uses the Anthropic Messages protocol but requires unsigned thinking blocks to be preserved when thinking mode is enabled. The current code strips all thinking blocks for third-party endpoints, causing Xiaomi's API to not receive the required reasoning_content.

Solution

Following the approach used for Kimi and DeepSeek endpoints:

1. Added _is_xiaomi_anthropic_endpoint() detection function
2. Added Xiaomi endpoint to _preserve_unsigned_thinking condition in convert_messages_to_anthropic()

This preserves unsigned thinking blocks synthesized from reasoning_content while stripping Anthropic's signed blocks, matching the behavior for Kimi and DeepSeek endpoints.

Test plan

• Test Xiaomi MiMo model with thinking mode enabled (reasoning_effort: medium/high)
• Verify no HTTP 400 errors when using thinking mode
• Verify thinking blocks are properly preserved in multi-turn conversations
• Verify existing Kimi and DeepSeek endpoints still work correctly

Related issues

Closes #24884

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Note: This PR was created by ClaudeCode powered by MiMo-2.5-Pro.

[alt-glitch]

Duplicate of #24465 (earliest open PR for Xiaomi MiMo reasoning_content echo-back). Also competes with #24603, #24784, #24810. Closes #24884 which is itself a duplicate of #24443.

[teknium1]

Thanks for identifying the Xiaomi replay contract. The underlying issue is still present on current main: agent/anthropic_adapter.py:2275-2278 preserves unsigned replay thinking only for Kimi and DeepSeek, while the third-party branch at agent/anthropic_adapter.py:2302-2309 strips Xiaomi's blocks.

Problems

• agent/anthropic_adapter.py:489 uses a raw "xiaomimimo.com" in normalized match. Please use the existing hostname-aware helper at utils.py:528-546; it rejects path and hostname-suffix collisions.
• Commit 01e053e84454 changes only agent/anthropic_adapter.py; add a Xiaomi regression test covering unsigned preservation, signed-block stripping, and a non-Xiaomi negative URL.
• Current main moved this logic into _manage_thinking_signatures() at agent/anthropic_adapter.py:2250-2309, so the patch needs to be ported there rather than applied to the old conversion block.

Suggested changes

• Add a fail-closed Xiaomi /anthropic detector using base_url_host_matches() and include it in the current preservation predicate.
• Add the focused regression coverage above.

Automated hermes-sweeper review.

[teknium1]

Use base_url_host_matches(base_url or "", "xiaomimimo.com") before the /anthropic path check. The current raw substring match also accepts URL paths and host suffixes containing this string; utils.py:528-546 provides the repository-standard fail-closed matcher.