claude-opus-4-6[1m] fails on startup: tool schema validation rejects oneOf/allOf/anyOf in bootstrap bundle

Bug

claude-opus-4-6[1m] fails before prompt execution with a 400 error on the startup tool bundle. All other models work.

Error

API Error: 400
{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "tools.25.custom.input_schema: input_schema does not support oneOf, allOf, or anyOf at the top level"
  }
}

Request IDs:

• req_011CZkztbxiR1mKp1R1mAf1X
• req_011CZkzL3cPtHycae76GHMVp

Repro

1. Open Claude Desktop or Claude Code
2. Set model to claude-opus-4-6[1m]
3. Send any prompt (e.g. "say ok")
4. Immediate 400 error before prompt execution

Proof it's the tool bundle, not the model

claude --model 'claude-opus-4-6[1m]' --strict-mcp-config --mcp-config=/path/to/empty-mcp.json -p 'say ok'
# Returns: ok

The 1M model works when the startup tool bundle is stripped. The failure is in the default tool/bootstrap bundle.

Local causes ruled out

• Repo-local Claude config: cleared
• User plugins: removed and blocklisted
• Local Claude Extensions: disabled
• Bridge state: reset
• Local agent mode session cache: reset
• Claude Code session cache: reset
• Desktop local-agent trusted folders: disabled
• Raw local MCP state: only shows account-side claude.ai connectors

Root cause

claude-opus-4-6[1m] applies stricter JSON schema validation to tool definitions than the standard model. One startup tool (index 25) has a top-level oneOf, allOf, or anyOf in its input_schema, which standard models tolerate but the 1M context beta rejects.

Expected behavior

The startup tool bundle should pass schema validation on all supported model variants, including the 1M context beta.

Environment

• macOS (Sequoia)
• Claude Code CLI + Claude Desktop
• Model: claude-opus-4-6[1m]