Summary

Follow-up to #70392 (closed as fixed). The sanitizeToolCallIds fix from #70030 correctly handles short conversations, but reasoning_content is missing 400 errors still occur in long sessions after context compaction.

Environment

• OpenClaw: 2026.4.23 (a979721)
• Model: moonshot/kimi-k2.6
• Thinking: enabled

Reproduction

1. Start a session with kimi-k2.6 as primary model
2. Run 15-20+ turns with heavy tool usage
3. Wait for LCM compaction (softThreshold trigger)
4. Continue tool calls after compaction → 400

Observed Errors (same session, same day)

• reasoning_content is missing in assistant tool call message at index 122
• reasoning_content is missing in assistant tool call message at index 144

Hypothesis

The fix preserves reasoning_content in normal multi-turn flow. However, after LCM compaction or context compression, assistant tool-call messages that were part of the compressed context may lose their reasoning_content during reconstruction. Moonshot's API then rejects the transcript on replay because it requires reasoning_content for all assistant tool-call messages when thinking is enabled.

Expected Behavior

reasoning_content should be preserved or synthetically restored for compressed assistant tool-call messages, even after LCM compaction.

Workaround

Model fallback to MiniMax/Grok succeeds. Kimi K2.6 usage deferred for long sessions until resolved.