2026 OpenClaw MeshMac: Mattermost Incoming Webhook for Multi-Node Build Status

If you already run OpenClaw on MeshMac, treat this integration like our Microsoft Teams webhook guide or Matrix webhook build status: same gateway-first shape, different JSON host. For deployment topology, start from the multi-node deployment guide and browse the OpenClaw hub.

Gateway and Webhook configuration

Pick one sender. Designate a single OpenClaw gateway process (stable VM, bastion, or a dedicated Mac) that owns outbound chat integrations. Builder nodes should enqueue “build finished” events to a shared queue or RPC channel—mirroring multi-node deploy and task queue sync—instead of calling Mattermost directly. That keeps firewall rules, secrets, and audit trails in one place.

Create the Mattermost Incoming Webhook. In Mattermost: Integrations → Incoming Webhooks → Add Incoming Webhook, choose the target team and channel, optionally lock the channel, and copy the generated URL. It looks like https://<your-host>/hooks/<token>. The path token is a bearer credential: anyone who can POST to it can post as the integration.

Wire the gateway. Configure your notifier to POST with Content-Type: application/json. A minimal body is {"text": "Build succeeded on main"}. For richer layouts, use attachments with fallback text so mobile clients still render something. Keep payloads under your server’s configured size limits; huge log dumps often return 400.

Egress and TLS. From the gateway shell, verify connectivity: curl -sS -o /dev/null -w "%{http_code}\n" -X POST -H "Content-Type: application/json" -d '{"text":"openclaw probe"}' "$MATTERMOST_WEBHOOK_URL" (use a throwaway test channel first). If you use an HTTP forward proxy, export the same HTTPS_PROXY variables your OpenClaw service uses. Align timeouts with gateway rate limits and session concurrency so a slow Mattermost day does not wedge your whole queue worker.

• Never log the full webhook URL. Log host plus the last four characters of the token path when debugging.
• Separate staging and production hooks so a test workflow cannot spam executives.
• If Mattermost sits behind mTLS or IP allowlists, terminate client TLS on the gateway side that security already trusts—do not scatter exceptions across every Mac in the pool.

Multi-node status aggregation minimal steps

Step 1 — Normalize events on ingest. Each MeshMac worker should emit a compact JSON record when a job finishes: workflow, state (succeeded, failed, cancelled), branch, short commit, run_url, mesh_node_id (hostname or pool tag), and provider_run_id from GitHub, GitLab, or your CI. The gateway merges these into one Mattermost message template.

Step 2 — One logical post per state transition. Emit when the workflow moves from running to terminal state—not on every log line. If several nodes report the same provider_run_id, the gateway should deduplicate before calling Mattermost (see task queue retry steps for backoff patterns shared with other chat targets).

Step 3 — Optional failover clarity. When you run redundant gateways or hot standby nodes, document which process owns the webhook and how you switch it during drills—overlap with cluster permission and failover so operators do not post from two gateways during cutover.

Tokens and minimum permissions

The Incoming Webhook is already a high-privilege secret: it can post to a channel without a user session. Store it in a file such as /etc/openclaw/secrets.d/mattermost/build-status.url with mode 0440, owner root, and group a dedicated openclaw-notify role, consistent with secrets and least privilege on MeshMac nodes. CI users and interactive developers should not read that group.

Do not reuse a personal access token for “simplicity” unless you truly need API calls beyond incoming webhooks; broader tokens increase blast radius if a laptop image leaks. If you must call Mattermost REST APIs (for example threaded replies), scope a bot account with only the channels you need and store those credentials separately from the webhook file.

Rotation playbook: create a new Incoming Webhook, swap the secret file on the gateway, reload the service, post a test message, then delete the old webhook in Mattermost. Document the steps beside your IM alerts and token rotation runbook so on-call does not improvise under pressure.

Shared patterns for verifying inbound CI webhooks to OpenClaw itself (signatures, replay windows) live in shared build notify webhooks; apply the same discipline to any callback that triggers builds, even though Mattermost outbound posts are URL-bearer style.

Troubleshooting FAQ when no message arrives

CI is green but the channel is empty

Confirm the gateway logged an outbound POST and HTTP status (not only “job succeeded”). Test from the gateway with minimal JSON. Verify the integration was not deleted or disabled, and that the channel still exists.

HTTP 400 from Mattermost

Malformed JSON, missing text when required, or payload too large. Shrink attachments and validate with Mattermost’s documented schema for your server version.

HTTP 403 or 404

Token rotated, webhook removed, or team/channel moved. Regenerate the hook URL and update the secret file; 404 often means the integration ID no longer exists.

Only some Macs “lose” notifications

Those workers may still be calling Mattermost directly with an old URL or bypassing the proxy. Enforce gateway-only egress and remove per-node exceptions.

Duplicate posts after a flaky network

Retries without idempotency. Dedupe on provider_run_id + state before emitting to Mattermost.