Slack

The Slack replica implements 22 Web API methods for a bot token, with Events API delivery for messages and reactions. Its key is slack. It was tested with @slack/web-api and @slack/bolt.

Connect

Variable	Value
`SLACK_API_URL`	Base URL of the Web API. It ends in `/api/`, so append the method name: `SLACK_API_URL + "chat.postMessage"`.
`SLACK_BOT_TOKEN`	Fake bot token. Send it as `Authorization: Bearer <token>`.
`SLACK_SIGNING_SECRET`	Signs HTTP event deliveries. Verify signatures against the raw request body.
`SLACK_APP_TOKEN`	Fake app-level token for Socket Mode.

import { WebClient } from '@slack/web-api';
const slack = new WebClient(process.env.SLACK_BOT_TOKEN, { slackApiUrl: process.env.SLACK_API_URL });
await slack.conversations.list();

import os
from slack_sdk import WebClient
slack = WebClient(token=os.environ['SLACK_BOT_TOKEN'], base_url=os.environ['SLACK_API_URL'].rstrip('/') + '/')
slack.conversations_list()

These are the snippets ancha connect slack --lang ts and --lang py print. The SDKs call every method with POST, which matters for trace checks. For Bolt in Socket Mode, set the local URL on both the app’s clientOptions and the receiver’s installerOptions.clientOptions. Otherwise the receiver opens its socket against real Slack.

Endpoints

Every method is called with POST at /api/<method>, so trace checks look like POST /api/chat.postMessage.

Method	Support	Notes
`auth.test`	supported	Also allowed while an SDK starts up, before the attempt’s clock starts.
`conversations.list`	partial	`types=im` lists the bot’s direct messages. `mpim` is accepted and matches nothing: multi-person direct messages are not modeled.
`conversations.info`	supported
`conversations.history`	supported	Newest first, with cursors.
`conversations.replies`	supported	Parent first, then replies oldest first.
`conversations.join`	supported
`conversations.create`	supported
`conversations.members`	supported
`conversations.open`	partial	One user opens a direct message, created on first use, or returns an existing one; `return_im` and `prevent_creation`. Multi-person direct messages are a gap.
`chat.postMessage`	partial	Text and a subset of blocks. A user ID as `channel` posts in the direct message with that user. Emits `message` events in channels where the bot is a member and in its direct messages.
`chat.update`	partial	Text and blocks; `metadata` and `attachments` are coverage gaps. Emits `message_changed`.
`chat.delete`	partial	The bot’s own messages. Emits `message_deleted`. Deleting a thread parent leaves its replies in place.
`chat.getPermalink`	supported	Returns a fictional workspace address.
`reactions.add`	supported	Emits `reaction_added`.
`reactions.remove`	partial	Emits `reaction_removed`.
`reactions.get`	supported
`search.messages`	partial	Needs a user token. The bot token, the only token Ancha provides, is rejected.
`users.list`	supported
`users.info`	supported
`users.lookupByEmail`	supported
`users.conversations`	partial	`types=im` lists the bot’s direct messages; `mpim` matches nothing.
`apps.connections.open`	partial	Socket Mode only, with `SLACK_APP_TOKEN`. One live socket per attempt.

Any other method returns HTTP 200 with {"ok": false, "error": "unknown_method"}, an ancha_gap message and the header x-ancha-gap: 1.

Events

Posting, editing and deleting messages and adding or removing reactions emit Events API envelopes for channels where the bot is a member. A person in the world who mentions the bot also emits app_mention. Starter history does not emit events. ancha run delivers events in one of three ways, set by agent.slack_transport in ancha.yaml:

Transport	How the agent receives events
`feed`	Polls `ANCHA_EVENTS_URL` with `ANCHA_EVENTS_TOKEN`. The default for command agents.
`http`	Ancha POSTs signed requests to the agent’s URL, after the Slack `url_verification` handshake. The default for endpoint agents.
`socket`	Socket Mode through `apps.connections.open`. Command agents only.

See ancha.yaml and Environment variables.

MCP server

ancha mcp serve --sandbox <id> runs a Slack MCP server over stdio, profile ancha-slack-v1, against a running sandbox. ancha mcp config --sandbox <id> prints the mcpServers entry to add to your MCP host. It exposes 19 tools that call the same Web API and appear in the same trace: slack_auth_test, slack_conversations_list, slack_conversations_info, slack_conversations_history, slack_conversations_replies, slack_conversations_members, slack_conversations_join, slack_conversations_create, slack_chat_postMessage, slack_chat_update, slack_chat_delete, slack_chat_getPermalink, slack_reactions_add, slack_reactions_remove, slack_reactions_get, slack_users_list, slack_users_info, slack_users_lookupByEmail, slack_users_conversations. The MCP server writes plain-text messages only and has no reset or admin tools. See ancha mcp.

Starter data

The slack-starter dataset is the workspace Acme: a bot, nine people and ten channels, with 52 messages of history. Worlds, sandboxes and the hosted console use it. Scene files carry their own seed.

Ref	User
`$slack_bot`	`@ancha` (“Ancha assistant”), a bot. Your agent acts as this user.
`$slack_ben`	Ben Carter, `ben@acme.example`
`$slack_rachel`	Rachel Moore, `rachel@acme.example`
`$slack_mike`	Mike Turner, `mike@acme.example`
`$slack_greg`	Greg Wilson, `greg@acme.example`
`$slack_laura`	Laura Kim, `laura@acme.example`
`$slack_tom`	Tom Hughes, `tom@acme.example`
`$slack_ellen`	Ellen Price, `ellen@acme.example`
`$slack_victor`	Victor Lane, `victor@acme.example`
`$slack_anna`	Anna Fischer, `anna@acme.example`

Ref	Channel	Members
`$slack_general`	`#general`, “Company updates”	Everyone, including the bot
`$slack_support`	`#support`, “Customer questions and follow-ups”	Bot, Ben, Mike, Greg, Laura, Anna
`$slack_growth`	`#growth`, “Ridgeway Robotics pilot”	Bot, Ben, Mike, Tom, Ellen
`$slack_orders`	`#orders-incident`, “Orders API operations”	Bot, Ben, Rachel, Greg
`$slack_leadership`	`#leadership`, private, “Private planning”	Ben and Mike. The bot is not a member.
`$slack_product`	`#product`, “Roadmap and customer feedback”	Bot, Ben, Ellen, Greg, Laura
`$slack_sales`	`#sales`, “Deals and pipeline”	Bot, Tom, Mike, Anna, Ben
`$slack_success`	`#customer-success`, “Renewals and onboarding”	Bot, Laura, Mike, Tom
`$slack_data`	`#data-platform`, “Warehouse sync and pipelines”	Bot, Victor, Greg, Rachel
`$slack_random`	`#random`, “Anything else”	Everyone except the bot

The messages tell one story: a support channel with customer questions and answers, an Orders API incident that was rolled back two hours ago, a sales pipeline, a product roadmap and a data platform team. The ones with refs, which checks can name:

Ref	Message
`$slack_question`	Mike in #support, 35 minutes before start: “Ridgeway Robotics cannot find last month’s CSV export. Where should I point them?”
`$slack_answer`, `$slack_followup`	Ben’s answer in that thread (“Reports → Exports. Choose the month, then Download CSV. The export can take two minutes to appear.”) and Mike’s thanks.
`$slack_access`	Ben in #support, 20 minutes before start: a second customer needs help inviting a teammate; an admin can use Settings → Members → Invite.
`$slack_sso`, `$slack_double`, `$slack_seats`	Three more support threads: Bluefield Logistics asking about SSO with Okta and SCIM, Kestrel Credit Union’s dashboard showing yesterday’s numbers twice (fixed in 4.12), and Pinecrest Health adding 20 seats mid-contract (prorated).
`$slack_brief`, `$slack_brief_reply`	Ben in #growth: the Ridgeway Robotics pilot is this week’s focus; Mike’s reply about the discovery call.
`$slack_case_study`	Ellen in #growth: the warehouse-to-pipeline case study draft is ready for review, with a thread.
`$slack_ops`, `$slack_docs`	Rachel in #orders-incident: the Orders API is healthy and the slow-request incident is resolved. Ben: a draft runbook update is in GitHub.
`$slack_latency`	Rachel in #orders-incident, 3 hours before start: p95 latency above 700 ms, with a thread about the 4.12.1 deploy and the rollback.
`$slack_welcome`, `$slack_roadmap`, `$slack_signed`, `$slack_hello_victor`	#general: a welcome, Thursday’s roadmap review, Pinecrest Health signing for 120 seats, and Victor joining the data platform team.
`$slack_feedback`, `$slack_spec`	#product: this month’s top feedback and the scheduled reports spec.
`$slack_renewal`	Mike in #sales: the Kestrel Credit Union renewal moves to contract next week.
`$slack_connector`	Victor in #data-platform: the Snowflake connector upgrade is tomorrow at 9am.
`$slack_private`	Ben in #leadership: a draft planning note.
`$slack_sourdough`	Greg in #random, about a sourdough starter.

ancha sandbox configuration --tools slack --json prints every message with its text and time.

Checks

Use slack.message to check what ended up in a channel:

- id: answered_in_thread
  state:
    slack.message:
      channel: $slack_support
      from: $slack_bot
      in_thread_of: $slack_question
      text_contains: "Exports"

It counts messages in channel that match every condition you set and passes when there are at least count_gte (default 1). text_contains ignores case. in_thread_of counts replies, not the parent. Set from, or a message from the starter history can satisfy the check. See Checks reference.

Limits

Bot token only: no user OAuth and no user-token search. The bot can open and post in a direct message with one user; multi-person direct messages are not modeled.
No file uploads, no Slack UI and no rate-limit model.
Unsupported message arguments, such as attachments, metadata and broadcast replies, return an error and change nothing.

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​Connect

​Endpoints

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​MCP server

​Starter data

​Checks

​Limits

Connect

Endpoints

Events

MCP server

Starter data

Checks

Limits