Bug type

Regression (worked before, now fails)

Beta release blocker

No

Summary

Bug Description

Mattermost slash commands are not working in OpenClaw v2026.4.15. All commands return HTTP 503 with message "Slash commands are not yet initialized. Please try again in a moment."

Environment

• OpenClaw version: 2026.4.15 (041266a)
• OS: Linux 6.8.0-106-generic
• Mattermost version: 6.1.1
• Installation method: npm global

Configuration

{
"channels": {
"mattermost": {
"commands": {
"native": true,
"nativeSkills": true,
"callbackUrl": "https://gateway.example.com:18789/api/channels/mattermost/command"
}
}
}
}

Steps to reproduce

1. Install OpenClaw v2026.4.15 with Mattermost channel configured
2. Configure native slash commands in openclaw.json (see Configuration section)
3. Start gateway and wait for commands to register (logs show "slash commands activated")
4. Execute any slash command in Mattermost (e.g., /oc_status)
5. Observe HTTP 503 error with message "Slash commands are not yet initialized"

Expected behavior

Slash command should execute successfully and return the requested information (e.g., gateway status for /oc_status).

According to OpenClaw documentation, GET request to /api/channels/mattermost/command should return 405 Method Not Allowed when the handler is properly initialized.

Actual behavior

• Commands are successfully registered in Mattermost (33 commands)
• Gateway logs show: [mattermost] slash commands activated for account default (33 commands)
• But all slash commands return: {"response_type":"ephemeral","text":"Slash commands are not yet initialized. Please try again in a moment."}
• GET request to callback endpoint returns HTTP 503 instead of expected 405 Method Not Allowed
• Problem persists even 90+ seconds after gateway startup
• Direct requests to gateway (127.0.0.1:18788) and through nginx proxy both fail with same error

OpenClaw version

2026.4.15 (041266a)

Operating system

Linux 6.8.0-106-generic (Ubuntu)

Install method

npm global

Model

anthropic/claude-opus-4-6

Provider / routing chain

Direct connection to Mattermost (http://127.0.0.1:8065) Nginx reverse proxy for callback URL (https://gateway.example.com:18789)

Additional provider/model setup details

Mattermost configuration:

• baseUrl: http://127.0.0.1:8065
• Callback URL: https://gateway.example.com:18789/api/channels/mattermost/command
• Native commands enabled: true
• Commands successfully registered in Mattermost via API
• Other channels (Telegram, Control UI) work normally

Logs, screenshots, and evidence

## Gateway startup logs:
2026-04-17T07:08:18 [plugins] mattermost: registered slash command callback at /api/channels/mattermost/command
2026-04-17T07:08:20 [gateway] ready (8 plugins: acpx, browser, device-pair, mattermost, memory-core, phone-control, talk-voice, telegram; 10.5s)
2026-04-17T07:08:44 [mattermost] slash commands activated for account default (33 commands)
2026-04-17T07:08:44 [mattermost] slash commands registered (33 commands across 1 teams, callback=https://gateway.example.com:18789/api/channels/mattermost/com

## Test results:
Tested callback endpoint 6 times over 90 seconds - all attempts returned same error:

{"response_type":"ephemeral","text":"Slash commands are not yet initialized. Please try again in a moment."}
# GET request to callback endpoint (should return 405, but returns 503)
curl -k https://gateway.example.com:18789/api/channels/mattermost/command
# Returns: HTTP/1.1 503 Service Unavailable
OpenClaw status output:

Channels:
- Telegram: OK (6 accounts)
- Mattermost: OK (@openclaw)

Gateway: reachable
Version: 2026.4.15 (041266a)


---

Impact and severity

Affected: All Mattermost users using native slash commands in v2026.4.15

Severity: High - completely blocks slash command functionality in Mattermost

Frequency: 100% reproducible on every gateway restart

Consequence:

• Users cannot execute any slash commands in Mattermost
• Must use alternative channels (Telegram, Control UI) as workaround
• Affects productivity for teams relying on Mattermost integration

Additional information

Regression: This appears to be a regression in v2026.4.15. The same configuration worked in previous versions.

Workaround: Using Telegram bots or Control UI instead of Mattermost slash commands.

Related issues: None found for this specific problem (checked #65624, #50625 - different issues)

Possible cause: The callback handler is registered in the plugin but the internal routing/initialization is not completing properly, leaving the handler in "not yet initialized" state permanently.