Description

After upgrading to OpenClaw 2026.5.12, the Xiaomi MiMo v2.5 provider (configured as openai-compatible API at token-plan-cn.xiaomimimo.com/v1) started returning HTTP 400 "Param Incorrect" when the agent sends a request with full tool schemas. Before the upgrade, it worked fine.

The error is:

FailoverError: LLM request failed: provider rejected the request schema or tool payload.

Underlying: 400 Param Incorrect | providerRuntimeFailureKind: "schema" | failoverReason: "format"

Root Cause Analysis

The root cause traces to the 2026.5.12 changelog entry:

"Agents: add permissive item schemas to array tool parameters before provider submission, preventing OpenAI-compatible schema validation from rejecting plugin tools that omit items."

This change adds items schemas to array tool parameters. The Xiaomi MiMo API does not accept this extended schema format and returns 400.

Impact

All cron jobs and agent sessions using xiaomi-mimo-tp/mimo-v2.5 as the primary model are affected. The failure is intermittent - some runs succeed while others fail with the same error, suggesting the provider may have varying tolerance for schema payload size/format.

Affected scenarios:

• Isolated cron agent sessions with tools.profile: "full" (sends all tool definitions)
• Both mimo-v2.5 and potentially mimo-v2.5-pro models
• Sessions using the full tool payload including exec, read, write, web tools, feishu plugin tools, etc.

Timeline

Log Evidence

{
  "event": "embedded_run_agent_end",
  "error": "LLM request failed: provider rejected the request schema or tool payload.",
  "failoverReason": "format",
  "model": "mimo-v2.5",
  "provider": "xiaomi-mimo-tp",
  "rawErrorPreview": "400 Param Incorrect",
  "providerRuntimeFailureKind": "schema"
}

Workaround

Adding a fallback model (e.g. deepseek/deepseek-v4-flash) to cron job payloads bypasses the issue since the fallback model is used when MiMo rejects the request.

Request

Two possible fixes:

1. Make the items schema addition optional or configurable, allowing it to be skipped for providers that don't support it
2. Detect schema rejection from the provider response and automatically strip items from array parameters before retrying

Environment

• OpenClaw version: 2026.5.12
• Provider: Xiaomi MiMo Token Plan (token-plan-cn.xiaomimimo.com/v1)
• Model: mimo-v2.5 (openai-completions API)
• Agent tools profile: full
• Session type: isolated cron agentTurn