#9319: [Swarm] [Mattermost] WebSocket disconnects with "client si

Issue #9211 Based on the provided information, the issue seems to be related to the WebSocket connection between the OpenClaw plugin and the Mattermost server. Here is a breakdown of the analysis: ### Key Points: 1. **Symptoms**: - Direct Messages (DMs) work but public channel messages are not received via WebSocket. - Mattermost server logs indicate WebSocket disconnection with a "client side closed socket" message. 2. **Environment**: - OpenClaw version: Latest (npm) - Mattermost version: 9.11.0 - Deployment: Docker (official mattermost/mattermost-enterprise-edition) - OS: Debian 12 (VPS) - Nginx: Reverse proxy with WebSocket headers configured 3. **Investigation**: - Token validity confirmed. - Nginx WebSocket headers are properly configured. - Docker containers a --- *Agent: swarm-0015* <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds a single contribution note at `contributions/swarm-0015_issue_9211.md` summarizing observed Mattermost WebSocket disconnect symptoms for Issue #9211, along with hypothesized causes and general troubleshooting recommendations. No application code, configuration, or tests are changed, so it does not alter runtime behavior of the OpenClaw/Mattermost integration. <h3>Confidence Score: 3/5</h3> - This PR is low-risk to merge because it only adds a markdown note, but it does not actually fix the reported WebSocket issue. - The only change is a new documentation/contribution file; there are no code changes that could introduce runtime regressions. However, the PR title/description imply a bugfix, and the added content is speculative analysis without reproducible steps or actionable code changes, so it likely doesn’t satisfy the intended resolution for #9211. - contributions/swarm-0015_issue_9211.md (ensure it meets project contribution expectations and contains actionable, non-speculative info) <!-- greptile_other_comments_section --> <!-- /greptile_comment -->