Bug type

Regression (worked before, now fails)

Beta release blocker

No

Summary

After upgrading from 2026.4.23 to 2026.4.24, identical user messages are occasionally delivered twice to the session with the same timestamp but different seq numbers, causing the assistant to reply to both and producing duplicate visible messages in all channels (webchat and WeChat).

Steps to reproduce

1. Run OpenClaw 2026.4.24 with webchat or WeChat channel configured
2. Send a user message from the webchat UI or WeChat
3. Observe session history via sessions_history API
4. Same user message appears twice in transcript with identical timestamp but sequential seq numbers (e.g., seq 2703 and seq 2705)
5. Assistant reply is also duplicated (seq 2704 and seq 2706) with same responseId

Expected behavior

In 2026.4.23, each user message was delivered exactly once. The same message should not appear twice in the session transcript.

Actual behavior

Same user message is delivered twice with identical timestamp but different __openclaw.id and sequential seq numbers. The assistant replies to both, producing duplicate visible messages. This happens intermittently, not on every message. Confirmed via sessions_history API showing duplicate entries for both user messages and assistant replies.

OpenClaw version

2026.4.24 (cbcfdf6)

Operating system

Linux 6.6.87.2-microsoft-standard-WSL2 (x64) / Windows 11 host

Install method

npm global

Model

bailian/qwen3.6-plus (also observed with nvidia-nim/z-ai/glm4.7)

Provider / routing chain

openclaw-weixin -> gateway -> bailian (dashscope) / webchat -> gateway -> bailian

Additional provider/model setup details

No response

Logs, screenshots, and evidence

Impact and severity

Affected: All channels (webchat, WeChat)
Severity: Medium (annoying UX, duplicate visible messages, no data loss)
Frequency: Intermittent — not every message, but recurring across multiple sessions
Consequence: User sees duplicate messages in chat history, making conversations hard to follow

Additional information

Last known good version: 2026.4.23
First known bad version: 2026.4.24

Session history evidence from sessions_history API:

• User message seq 2703 at timestamp 1777207291784
• User message seq 2705 at same timestamp 1777207291784 (duplicate)
• Assistant reply seq 2704 at timestamp 1777207292059
• Assistant reply seq 2706 at same timestamp 1777207292059 (duplicate)

This pattern repeats multiple times (seq 2707-2710).

Possible related changes in 2026.4.24:

• Block streaming dedupe fix (Fixes Block-streaming channels deliver assembled final payload in addition to per-chunk streaming, causing full-reply duplication #70921)
• Gateway/sessions webchat mutation guard changes (Fixes fix(gateway): block webchat session compaction mutations #70716)
• Gateway/WebChat image attachment preservation (Fixes [Bug] User image attachments dropped when primary model lacks vision — imageModel fallback not honored #68513)

No workaround available — occurs at the session delivery layer.