lfx-slack

Slack Web API actions for Langflow, backed by connections.

Seven components, split by executing identity:

The action set, its scopes, and the executing identity per action are frozen by the INT-1 discovery gate in design/dedicated-integrations/matrices/slack.json; capabilities.v1.json is lifted from it and scripts/ci/check_capability_manifests.py proves the two still agree.

Two identities, two connections

Slack user tokens and bot tokens are different credentials with overlapping scope names, so the bundle ships two authorization profiles:

• slack-user-oauth — an OAuth authorization-code grant whose user_scope the connected Slack user approves. Available in every deployment context, including Desktop (PKCE, loopback redirect).
• slack-bot-install — a workspace installation whose bot token belongs to the workspace, not to the installing user. Not available on Desktop: Slack desktop redirects may not request bot scopes.

A component that runs as the bot fails closed with connection-not-authorized before its first request when it is handed a user token, and the reverse. It checks two signals, and each one that is present must match the action: ResolvedCredential.identity, recorded on the connection by the host, and the token's own type prefix (xoxb- bot, xoxp- user, optionally behind the xoxe. rotation marker).

Connections resolved from LF_CONNECTION__SLACK__<NAME> carry no recorded identity, so the prefix is the only proof for them, and a headless token without a recognizable prefix is refused. Slack's own not_allowed_token_type is not a backstop: chat.postMessage accepts both token types, so a mismatched token would post under the wrong author without an error.

Hiding the bot components on Desktop is delivered by capability discovery filtering on deployment_contexts (INT-7/INT-8), not by this bundle; the bundle only declares the contexts.

Errors

Slack answers HTTP 200 with {"ok": false, "error": "..."}, so the bundle registers a provider error normalizer with lfx. Without it, an expired token or a missing scope would be reported as provider-unavailable and the frontend's reconnect and grant-scopes affordances would never appear.

Only rate-limited and provider-unavailable are retryable. The full code sets live in _client.py. Slack's HTTP 200 is never copied onto the typed error, so a run that fails this way is not reported with a success status.

An auth-expired rejection triggers exactly one reactive re-resolve through CredentialLease.get_token_after_auth_error, which is how a rotated Slack token is picked up: Slack tokens have no expiry unless the app opted into rotation, so a rejection is the only signal.

Rate limits

conversations.replies (Read Thread) is Tier 3 for Slack Marketplace apps but 1 request per minute with a 15-message page for commercially distributed apps that are not listed in the Marketplace. chat.postMessage is roughly one message per second per channel. Components make one Web API call per run (plus one users.info per member when Resolve display names is on), and components with two outputs memoize the response so a second output never spends a second call.

SSRF posture

The API root is the module constant SLACK_API_BASE_URL (https://slack.com/api/) and no component exposes a URL, host, or proxy input, so there is no user-controllable request target. The bundle therefore does not use lfx.utils.ssrf_transport: those helpers build httpx clients with DNS pinning, and slack_sdk.web.async_client.AsyncWebClient speaks aiohttp, for which lfx ships no equivalent. Removing the surface is a stronger guarantee than pinning DNS for a URL a flow author can set.

Install

lfx-slack is part of the default uv pip install langflow install. Installing lfx on its own:

uv pip install lfx-slack

Tests

uv venv
uv pip install ./src/lfx ./src/bundles/slack pytest pytest-asyncio
.venv/bin/python -m pytest src/bundles/slack/tests -q -m "not api_key_required"

The opt-in live-workspace suite (tests/test_slack_live.py) is marked api_key_required and skips unless LANGFLOW_SLACK_LIVE_USER_TOKEN, LANGFLOW_SLACK_LIVE_BOT_TOKEN, and LANGFLOW_SLACK_LIVE_CHANNEL are set. It is never run in CI.