Feishu WebSocket duplicate messages issue

Description

Feishu channel receives duplicate messages repeatedly from the same conversation, causing duplicate responses.

Evidence

Logs show repeated message deliveries with same conversation ID:

All messages have same conversation ID: oc_8c03ea94803e8faaf921c4b5d3f7c984

Root Cause Analysis

1. Feishu WebSocket doesn't receive proper ACK from OpenClaw
2. Feishu server keeps retrying message delivery
3. OpenClaw Feishu plugin has no message deduplication based on message_id

Impact

• Duplicate messages cause duplicate responses in chat
• Affects user experience (messages appear multiple times)
• Messages are still processed correctly, but repeated

Expected Behavior

• Messages should be deduplicated based on message_id
• OR ACKs should be properly sent to prevent retry

Environment

• OpenClaw version: 2026.2.6-3
• Channel: Feishu (websocket mode)
• Feishu app: cli_a9f6140194b89bd9
• Gateway running with systemd

Additional Notes

This appears to be a persistent issue where Feishu keeps retrying delivery without ACK confirmation. The messages are not due to WebSocket disconnect/reconnect - logs show connection stays stable but messages still repeat every 18-21 seconds or 4+ minutes.

A deduplication mechanism based on message_id in the Feishu plugin would resolve this issue.