openclaw - 💡(How to fix) Fix [Bug]: WhatsApp channel silently drops long/complex agent responses (v2026.5.18) [3 comments, 3 participants]

Describe the Bug

After upgrading OpenClaw from 2026.5.12 to 2026.5.18, the WhatsApp channel silently drops long or complex agent responses (e.g., markdown tables, multi-line structured content over ~500 chars). Short responses (version checks, 1-line confirmations) deliver fine. Rolling back to 2026.5.12 restores full delivery.

To Reproduce

1. Install OpenClaw v2026.5.18
2. Configure WhatsApp channel (direct chat)
3. Ask the agent a question that generates a response with markdown tables, code blocks, or ~1KB+ structured text
4. Observe: the response never arrives on WhatsApp. No error is logged in gateway logs.
5. Repeat with a short query ("what version?") — response arrives immediately.

Expected Behavior

All agent responses, regardless of length or formatting complexity, should be delivered to the WhatsApp channel as they did in v2026.5.12.

Environment

• OpenClaw version: 2026.5.18 (regression), working on 2026.5.12
• Platform: macOS (Mac Studio M4 Max, macOS 15.x)
• WhatsApp plugin version: 2026.5.12 (pre-upgrade) and 2026.5.18 (updated — same broken behavior)
• Node.js: v25.9.0
• Channel: WhatsApp (direct chat, allowlist DM policy)
• Config: textChunkLimit 100000, chunkMode "newline"

Root Cause Analysis

The 2026.5.18 release introduced a channel presentation capability negotiation system (changelog: "Plugins/messages: add presentation capability limits for channel renderers, adapt rich message controls before native rendering").

Telegram and Mattermost channels declare presentationCapabilityLimits in their channel-actions files (see related issues #56039, #55649, #56496). The WhatsApp channel plugin appears to be missing this capability declaration. When the core attempts to adapt a complex message for a renderer that returns no capabilities, it triggers a silent failure path instead of falling back to raw text delivery.

Suggested Fix

Add a presentationCapabilityLimits declaration to the WhatsApp channel plugin (analogous to the Telegram implementation in extensions/telegram/src/channel-actions.ts), declaring basic text markdown capability without rich controls (buttons, interactive elements). The adaptation layer should fall back to plain text on capability mismatch rather than silently dropping messages.

Workaround

Rollback to OpenClaw v2026.5.12:

npm install -g [email protected]