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Status: downloadable plugin (bot token + WebSocket events). Channels, private channels, group DMs, and DMs are supported. Mattermost is a self-hostable team messaging platform (mattermost.com).

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Install

Details: Plugins

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Quick setup

1

Ensure plugin is available

Install @openclaw/mattermost with the command above, then restart the Gateway if it is already running.
2

Create a Mattermost bot

Create a Mattermost bot account, copy the bot token, and add the bot to the teams and channels it should read.
3

Copy the base URL

Copy the Mattermost base URL (e.g., https://chat.example.com). A trailing /api/v4 is stripped automatically.
4

Configure OpenClaw and start the gateway

Minimal config:
Non-interactive alternative:
Self-hosted Mattermost on a private/LAN/tailnet address: outbound Mattermost API requests pass through an SSRF guard that blocks private and internal IPs by default. Opt in with channels.mattermost.network.dangerouslyAllowPrivateNetwork: true (per account: channels.mattermost.accounts.<id>.network.dangerouslyAllowPrivateNetwork).

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Native slash commands

Native slash commands are opt-in. When enabled, OpenClaw registers oc_* slash commands on every team the bot is a member of and receives callback POSTs on the gateway HTTP server.
Registered commands: /oc_status, /oc_model, /oc_models, /oc_new, /oc_help, /oc_think, /oc_reasoning, /oc_verbose, /oc_queue. With nativeSkills: true, skill commands are also registered as /oc_<skill>.
  • native and nativeSkills default to "auto", which resolves to disabled for Mattermost. Set them to true explicitly.
  • callbackPath defaults to /api/channels/mattermost/command.
  • If callbackUrl is omitted, OpenClaw derives http://<gateway.customBindHost or localhost>:<gateway.port, default 18789><callbackPath>. Wildcard bind hosts (0.0.0.0, ::) fall back to localhost.
  • For multi-account setups, commands can be set at the top level or under channels.mattermost.accounts.<id>.commands (account values override top-level fields).
  • Existing slash commands with the same trigger created by other integrations are left untouched (registration skips them); commands the bot created are updated or recreated when the callback URL drifts.
  • Command callbacks are validated with the per-command tokens returned by Mattermost when OpenClaw registers oc_* commands.
  • OpenClaw refreshes current Mattermost command registration before accepting each callback, so stale tokens from deleted or regenerated slash commands stop being accepted without a gateway restart.
  • Callback validation fails closed if the Mattermost API cannot confirm the command is still current; failed validations are cached briefly, concurrent lookups are coalesced, and fresh lookup starts are rate-limited per command to bound replay pressure.
  • Slash callbacks fail closed when registration failed, startup was partial, or the callback token does not match the resolved command’s registered token (a token valid for one command cannot reach upstream validation for a different command).
  • Accepted callbacks are acknowledged with an ephemeral “Processing…” reply; the real answer arrives as a normal message.
The callback endpoint must be reachable from the Mattermost server.
  • Do not set callbackUrl to localhost unless Mattermost runs on the same host/network namespace as OpenClaw.
  • Do not set callbackUrl to your Mattermost base URL unless that URL reverse-proxies /api/channels/mattermost/command to OpenClaw.
  • A quick check is curl https://<gateway-host>/api/channels/mattermost/command; a GET should return 405 Method Not Allowed from OpenClaw, not 404.
If your callback targets private/tailnet/internal addresses, set Mattermost ServiceSettings.AllowedUntrustedInternalConnections to include the callback host/domain.Use host/domain entries, not full URLs.
  • Good: gateway.tailnet-name.ts.net
  • Bad: https://gateway.tailnet-name.ts.net

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Environment variables (default account)

Set these on the gateway host if you prefer env vars:
  • MATTERMOST_BOT_TOKEN=...
  • MATTERMOST_URL=https://chat.example.com
Env vars apply only to the default account (default). Other accounts must use config values.MATTERMOST_URL cannot be set from a workspace .env; see Workspace .env files.

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Chat modes

Mattermost responds to DMs automatically. Channel behavior is controlled by chatmode:
Respond only when @mentioned in channels.
Config example:
Notes:
  • onchar still responds to explicit @mentions.
  • channels.mattermost.requireMention is still honored, but chatmode is preferred. Per-channel groups.<channelId>.requireMention settings win over both.
  • After the bot sends a visible reply in a channel thread, later messages in that same thread are answered without a new @mention or onchar prefix, so multi-turn thread conversations keep flowing. Participation is remembered for 7 days after the bot last replied in that thread and persists across gateway restarts. Threads the bot has only observed are unaffected; start a new top-level message to require an explicit mention again.

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Threading and sessions

Use channels.mattermost.replyToMode to control whether channel and group replies stay in the main channel or start a thread under the triggering post.
  • off (default): only reply in a thread when the inbound post is already in one.
  • first: for top-level channel/group posts, start a thread under that post and route the conversation to a thread-scoped session.
  • all and batched: same behavior as first for Mattermost today, because once Mattermost has a thread root, follow-up chunks and media continue in that same thread.
  • Direct messages default to off even when replyToMode is set.
Use channels.mattermost.replyToModeByChatType to override the mode for direct, group, or channel chats. Set direct to opt direct messages into threading:
  • off (default): direct messages stay non-threaded in one rolling session.
  • first, all, or batched: each top-level direct message starts a Mattermost thread backed by a fresh, independent session.
Notes:
  • Thread-scoped sessions use the triggering post id as the thread root.
  • first and all are currently equivalent because once Mattermost has a thread root, follow-up chunks and media continue in that same thread.
  • Per-chat-type overrides take precedence over replyToMode. Without a direct override, existing deployments keep flat, non-threaded DMs.

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Access control (DMs)

  • Default: channels.mattermost.dmPolicy = "pairing" (unknown senders get a pairing code). Other values: allowlist, open, disabled.
  • Approve via:
    • openclaw pairing list mattermost
    • openclaw pairing approve mattermost <CODE>
  • Public DMs: channels.mattermost.dmPolicy="open" plus channels.mattermost.allowFrom=["*"] (the config schema enforces the wildcard).
  • channels.mattermost.allowFrom accepts user ids (recommended) and accessGroup:<name> entries. See Access groups.

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Channels (groups)

  • Default: channels.mattermost.groupPolicy = "allowlist" (mention-gated).
  • Allowlist senders with channels.mattermost.groupAllowFrom (user IDs recommended).
  • channels.mattermost.groupAllowFrom accepts accessGroup:<name> entries. See Access groups.
  • Per-channel mention overrides live under channels.mattermost.groups.<channelId>.requireMention or channels.mattermost.groups["*"].requireMention for a default.
  • @username matching is mutable and only enabled when channels.mattermost.dangerouslyAllowNameMatching: true.
  • Open channels: channels.mattermost.groupPolicy="open" (mention-gated).
  • Resolution order: channels.mattermost.groupPolicy, then channels.defaults.groupPolicy, then "allowlist".
  • Runtime note: if the channels.mattermost section is completely missing, runtime fails closed to groupPolicy="allowlist" for group checks (even if channels.defaults.groupPolicy is set) and logs a one-time warning.
Example:

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Targets for outbound delivery

Use these target formats with openclaw message send or cron/webhooks: Outbound sends support at most one attachment per message; split multiple files into separate sends.
Bare opaque IDs (like 64ifufp...) are ambiguous in Mattermost (user ID vs channel ID).OpenClaw resolves them user-first:
  • If the ID exists as a user (GET /api/v4/users/<id> succeeds), OpenClaw sends a DM by resolving the direct channel via /api/v4/channels/direct.
  • Otherwise the ID is treated as a channel ID.
If you need deterministic behavior, always use the explicit prefixes (user:<id> / channel:<id>).

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DM channel retry

When OpenClaw sends to a Mattermost DM target and needs to resolve the direct channel first, it retries transient direct-channel creation failures by default. Use channels.mattermost.dmChannelRetry to tune that behavior globally for the Mattermost plugin, or channels.mattermost.accounts.<id>.dmChannelRetry for one account. Defaults:
Notes:
  • This applies only to DM channel creation (/api/v4/channels/direct), not every Mattermost API call.
  • Retries use exponential backoff with jitter and apply to transient failures such as rate limits, 5xx responses, and network or timeout errors.
  • 4xx client errors other than 429 are treated as permanent and are not retried.

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Preview streaming

Mattermost streams thinking, tool activity, and partial reply text into a draft preview post that finalizes in place when the final answer is safe to send. In partial mode the preview updates on the same post id instead of spamming the channel with per-chunk messages. In block mode the preview rotates between completed text and tool-activity blocks, so earlier blocks stay visible as their own posts instead of being overwritten by the next one. Media/error finals cancel pending preview edits and use normal delivery instead of flushing a throwaway preview post. Preview streaming is on by default in partial mode. Configure via channels.mattermost.streaming.mode (legacy scalar/boolean streaming values are migrated by openclaw doctor --fix):
  • partial (default): one preview post that is edited as the reply grows, then finalized with the complete answer.
  • block rotates the preview between completed text and tool-activity blocks, so each block stays visible as its own post instead of being overwritten in place. Parallel and consecutive tool updates share the current tool-activity post.
  • progress shows a status preview while generating and only posts the final answer at completion.
  • off disables preview streaming. With streaming.block.enabled: true, completed assistant blocks are still delivered as normal block replies (separate posts) rather than a single coalesced final post.
  • If the stream cannot be finalized in place (for example the post was deleted mid-stream), OpenClaw falls back to sending a fresh final post so the reply is never lost.
  • Thinking-only payloads are suppressed from channel posts, including text that arrives as a > Thinking blockquote. Set /reasoning on to see thinking in other surfaces; the Mattermost final post keeps the answer only.
  • See Streaming for the channel-mapping matrix.

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Reactions (message tool)

  • Use message action=react with channel=mattermost.
  • messageId is the Mattermost post id.
  • emoji accepts names like thumbsup or :+1: (colons are optional).
  • Set remove=true (boolean) to remove a reaction.
  • Reaction add/remove events are forwarded as system events to the routed agent session, subject to the same DM/group policy checks as messages.
Examples:
Config:
  • channels.mattermost.actions.reactions: enable/disable reaction actions (default true).
  • Per-account override: channels.mattermost.accounts.<id>.actions.reactions.

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Interactive buttons (message tool)

Send messages with clickable buttons. When a user clicks a button, the agent receives the selection and can respond. Buttons come from the semantic presentation payload (in normal agent replies and in message action=send). OpenClaw renders value buttons as Mattermost interactive buttons, keeps URL buttons visible in the message text, and downgrades select menus to readable text.
Presentation button fields:
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label
string
required
Display label (alias: text).
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value
string
Value sent back on click, used as the action ID (aliases: callback_data, callbackData). Required for a clickable button unless url is set.
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url
string
Link button; rendered as label: url text in the message body instead of an interactive button.
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style
"primary" | "secondary" | "success" | "danger"
Button style. Mattermost applies default styling to values it does not support.
To advertise button support in the agent system prompt, add inlineButtons to the channel capabilities:
When a user clicks a button:
1

Access check

The clicker must pass the same DM/group policy checks as a message sender; unauthorized clicks get an ephemeral notice and are ignored.
2

Buttons replaced with confirmation

All buttons are replaced with a confirmation line (e.g., ”✓ Yes selected by @user”).
3

Agent receives the selection

The agent receives the selection as an inbound message (plus a system event) and responds.
  • Button callbacks use HMAC-SHA256 verification (automatic, no config needed).
  • The whole attachment block is replaced on click, so all buttons are removed together - partial removal is not possible.
  • Action IDs containing hyphens or underscores are sanitized automatically (Mattermost routing limitation).
  • Clicks whose action_id does not match an action on the original post are rejected with 403 (“Unknown action”).
  • channels.mattermost.capabilities: array of capability strings. Add "inlineButtons" to enable the buttons tool description in the agent system prompt.
  • channels.mattermost.interactions.callbackBaseUrl: optional external base URL for button callbacks (for example https://gateway.example.com). Use this when Mattermost cannot reach the gateway at its bind host directly.
  • In multi-account setups, you can also set the same field under channels.mattermost.accounts.<id>.interactions.callbackBaseUrl.
  • If interactions.callbackBaseUrl is omitted, OpenClaw derives the callback URL from gateway.customBindHost + gateway.port (default 18789), then falls back to http://localhost:<port>. The callback path is /mattermost/interactions/<accountId>.
  • Reachability rule: the button callback URL must be reachable from the Mattermost server. localhost only works when Mattermost and OpenClaw run on the same host/network namespace.
  • channels.mattermost.interactions.allowedSourceIps: source-IP allowlist for button callbacks. Without it, only loopback sources (127.0.0.1, ::1) are accepted, so a remote Mattermost server must be allowlisted here or its clicks are rejected with 403. Behind a reverse proxy, also set gateway.trustedProxies so the real client IP is derived from forwarded headers.
  • If your callback target is private/tailnet/internal, add its host/domain to Mattermost ServiceSettings.AllowedUntrustedInternalConnections.

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Direct API integration (external scripts)

External scripts and webhooks can post buttons directly via the Mattermost REST API instead of going through the agent’s message tool. Prefer OpenClaw’s message tool. For direct integrations, import buildButtonAttachments from @openclaw/mattermost/api.js; if posting raw JSON, follow these rules: Payload structure:
Critical rules
  1. Attachments go in props.attachments, not top-level attachments (silently ignored).
  2. Every action needs type: "button" - without it, clicks are swallowed silently.
  3. Every action needs an id field - Mattermost ignores actions without IDs.
  4. Action id must be alphanumeric only ([a-zA-Z0-9]). Hyphens and underscores break Mattermost’s server-side action routing (returns 404). Strip them before use.
  5. context.action_id must match the button’s id; the gateway rejects clicks whose action_id does not exist on the post.
  6. context.action_id is required - the interaction handler returns 400 without it.
  7. The callback source IP must be allowed (see interactions.allowedSourceIps above).
HMAC token generation The gateway verifies button clicks with HMAC-SHA256. External scripts must generate tokens that match the gateway’s verification logic:
1

Derive the secret from the bot token

HMAC-SHA256(key="openclaw-mattermost-interactions", data=botToken), hex-encoded.
2

Build the context object

Build the context object with all fields except _token.
3

Serialize with sorted keys

Serialize with recursively sorted keys and no spaces (the gateway canonicalizes nested objects too and produces compact JSON).
4

Sign the payload

HMAC-SHA256(key=secret, data=serializedContext)
5

Add the token

Add the resulting hex digest as _token in the context.
Python example:
  • Python’s json.dumps adds spaces by default ({"key": "val"}). Use separators=(",", ":") to match JavaScript’s compact output ({"key":"val"}).
  • Always sign all context fields (minus _token). The gateway strips _token then signs everything remaining. Signing a subset causes silent verification failure.
  • Use sort_keys=True - the gateway sorts keys before signing, and Mattermost may reorder context fields when storing the payload.
  • Derive the secret from the bot token (deterministic), not random bytes. The secret must be the same across the process that creates buttons and the gateway that verifies.

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Directory adapter

The Mattermost plugin includes a directory adapter that resolves channel and user names via the Mattermost API. This enables #channel-name and @username targets in openclaw message send and cron/webhook deliveries. No configuration is needed - the adapter uses the bot token from the account config.

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Multi-account

Mattermost supports multiple accounts under channels.mattermost.accounts:
Account values override top-level fields; channels.mattermost.defaultAccount picks which account is used when none is specified.

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Troubleshooting

Ensure the bot is in the channel and mention it (oncall), use a trigger prefix (onchar), or set chatmode: "onmessage".
  • Check the bot token, base URL, and whether the account is enabled.
  • Multi-account issues: env vars only apply to the default account.
  • Private/LAN Mattermost hosts need network.dangerouslyAllowPrivateNetwork: true (the SSRF guard blocks private IPs by default).
  • Unauthorized: invalid command token.: OpenClaw did not accept the callback token. Typical causes:
    • slash command registration failed or only partially completed at startup
    • the callback is hitting the wrong gateway/account
    • Mattermost still has old commands pointing at a previous callback target
    • the gateway restarted without reactivating slash commands
  • If native slash commands stop working, check logs for mattermost: failed to register slash commands or mattermost: native slash commands enabled but no commands could be registered.
  • If callbackUrl is omitted and logs warn that the callback resolved to a loopback URL like http://localhost:18789/..., that URL is probably only reachable when Mattermost runs on the same host/network namespace as OpenClaw. Set an explicit externally reachable commands.callbackUrl instead.
  • Buttons appear as white boxes or not at all: the button data is malformed. Each presentation button needs a label and a value (buttons missing either are dropped).
  • Buttons render but clicks do nothing: verify the gateway is reachable from the Mattermost server, the Mattermost server IP is included in channels.mattermost.interactions.allowedSourceIps (only loopback is accepted without it), and ServiceSettings.AllowedUntrustedInternalConnections includes the callback host for private targets.
  • Buttons return 404 on click: the button id likely contains hyphens or underscores. Mattermost’s action router breaks on non-alphanumeric IDs. Use [a-zA-Z0-9] only.
  • Gateway logs rejected callback source: the click came from an IP outside interactions.allowedSourceIps. Allowlist the Mattermost server or your ingress, and set gateway.trustedProxies behind a reverse proxy.
  • Gateway logs invalid _token: HMAC mismatch. Check that you sign all context fields (not a subset), use sorted keys, and use compact JSON (no spaces). See the HMAC section above.
  • Gateway logs missing _token in context: the _token field is not in the button’s context. Ensure it is included when building the integration payload.
  • Gateway rejects the click with Unknown action: context.action_id does not match any action id on the post. Set both to the same sanitized value.
  • Agent does not offer buttons: add capabilities: ["inlineButtons"] to the Mattermost channel config.