feat: Add slack trigger webhook (#1006)

* feat: Add slack trigger webhook

* cr

* better username tagging, react with eyes

* cr

* cr

* cr

apps/agent/agent/prompt.py

@@ -37,7 +37,9 @@ TASK_EXECUTION_SECTION = """---
 
 ### Task Execution
 
-If you make changes, call `linear_comment` to notify the user of the changes. For questions or status updates, call `linear_comment` with your answer.
+If you make changes, communicate updates in the source channel:
+- Use `linear_comment` for Linear-triggered tasks.
+- Use `slack_thread_reply` for Slack-triggered tasks.
 
 For tasks that require code changes, follow this order:
 
@@ -45,12 +47,12 @@ For tasks that require code changes, follow this order:
 2. **Implement** — Make focused, minimal changes. Do not modify code outside the scope of the task.
 3. **Verify** — Run tests and linters to confirm correctness before submitting.
 4. **Submit** — Call `commit_and_open_pr`.
-5. **Comment** — Call `linear_comment` with a summary and the PR link.
+5. **Comment** — Call `linear_comment` or `slack_thread_reply` with a summary and the PR link.
 
 For questions or status checks (no code changes needed):
 
 1. **Answer** — Gather the information needed to respond.
-2. **Comment** — Call `linear_comment` with your answer. Never leave a question unanswered."""
+2. **Comment** — Call `linear_comment` or `slack_thread_reply` with your answer. Never leave a question unanswered."""
 
 
 TOOL_USAGE_SECTION = """---
@@ -70,7 +72,11 @@ Make HTTP requests (GET, POST, PUT, DELETE, etc.) to APIs. Use this for API call
 Commits all changes, pushes to a branch, and opens a **draft** GitHub PR. If a PR already exists for the branch, it is updated instead of recreated.
 
 #### `linear_comment`
-Posts a comment to a Linear ticket given a `ticket_id`. Call this **after** `commit_and_open_pr` to notify stakeholders that the work is done and include the PR link. You can tag Linear users with `@username` (their Linear display name). Example: "I've completed the implementation and opened a PR: <pr_url>. Hey @username, let me know if you have any feedback!"."""
+Posts a comment to a Linear ticket given a `ticket_id`. Call this **after** `commit_and_open_pr` to notify stakeholders that the work is done and include the PR link. You can tag Linear users with `@username` (their Linear display name). Example: "I've completed the implementation and opened a PR: <pr_url>. Hey @username, let me know if you have any feedback!".
+
+#### `slack_thread_reply`
+Posts a message to the active Slack thread. Use this for clarifying questions, status updates, and final summaries when the task was triggered from Slack.
+Remember that Slack does not use standard markdown formatting. Ensure you always conform to the Slack specific markdown format when sending messages"""
 
 
 TOOL_BEST_PRACTICES_SECTION = """---

apps/agent/agent/server.py

@@ -32,7 +32,13 @@ from .middleware import (
     open_pr_if_needed,
 )
 from .prompt import construct_system_prompt
-from .tools import commit_and_open_pr, fetch_url, http_request, linear_comment
+from .tools import (
+    commit_and_open_pr,
+    fetch_url,
+    http_request,
+    linear_comment,
+    slack_thread_reply,
+)
 from .utils.auth import save_encrypted_token_from_email
 from .utils.model import make_model
 
@@ -377,7 +383,7 @@ async def get_agent(config: RunnableConfig) -> Pregel:  # noqa: PLR0915
             linear_issue_number=linear_issue_number,
             agents_md=agents_md,
         ),
-        tools=[http_request, fetch_url, commit_and_open_pr, linear_comment],
+        tools=[http_request, fetch_url, commit_and_open_pr, linear_comment, slack_thread_reply],
         backend=sandbox_backend,
         middleware=[
             ToolErrorMiddleware(),

apps/agent/agent/tools/__init__.py

@@ -2,5 +2,12 @@ from .commit_and_open_pr import commit_and_open_pr
 from .fetch_url import fetch_url
 from .http_request import http_request
 from .linear_comment import linear_comment
+from .slack_thread_reply import slack_thread_reply
 
-__all__ = ["commit_and_open_pr", "fetch_url", "http_request", "linear_comment"]
+__all__ = [
+    "commit_and_open_pr",
+    "fetch_url",
+    "http_request",
+    "linear_comment",
+    "slack_thread_reply",
+]

apps/agent/agent/tools/slack_thread_reply.py

@@ -0,0 +1,27 @@
+import asyncio
+from typing import Any
+
+from langgraph.config import get_config
+
+from ..utils.slack import post_slack_thread_reply
+
+
+def slack_thread_reply(message: str) -> dict[str, Any]:
+    """Post a message to the current Slack thread."""
+    config = get_config()
+    configurable = config.get("configurable", {})
+    slack_thread = configurable.get("slack_thread", {})
+
+    channel_id = slack_thread.get("channel_id")
+    thread_ts = slack_thread.get("thread_ts")
+    if not channel_id or not thread_ts:
+        return {
+            "success": False,
+            "error": "Missing slack_thread.channel_id or slack_thread.thread_ts in config",
+        }
+
+    if not message.strip():
+        return {"success": False, "error": "Message cannot be empty"}
+
+    success = asyncio.run(post_slack_thread_reply(channel_id, thread_ts, message))
+    return {"success": success}

apps/agent/agent/utils/auth.py

@@ -14,6 +14,7 @@ from langgraph_sdk import get_client
 
 from ..encryption import encrypt_token
 from .linear import comment_on_linear_issue
+from .slack import post_slack_thread_reply
 
 logger = logging.getLogger(__name__)
 
@@ -36,6 +37,30 @@ logger.debug(
 )
 
 
+def _retry_instruction(source: str) -> str:
+    if source == "slack":
+        return "Once authenticated, mention me again in this Slack thread to retry."
+    return "Once authenticated, reply to this issue mentioning @openswe to retry."
+
+
+def _source_account_label(source: str) -> str:
+    if source == "slack":
+        return "Slack"
+    return "Linear"
+
+
+def _auth_link_text(source: str, auth_url: str) -> str:
+    if source == "slack":
+        return auth_url
+    return f"[Authenticate with GitHub]({auth_url})"
+
+
+def _work_item_label(source: str) -> str:
+    if source == "slack":
+        return "thread"
+    return "issue"
+
+
 def get_service_jwt_token_for_user(
     user_id: str, tenant_id: str, expiration_seconds: int = 300
 ) -> str:
@@ -45,10 +70,10 @@ def get_service_jwt_token_for_user(
         raise ValueError(msg)
 
     payload = {
-        "sub": user_id,
+        "sub": "unspecified",
-        "tenant_id": tenant_id,
-        "iat": datetime.now(UTC),
         "exp": datetime.now(UTC) + timedelta(seconds=expiration_seconds),
+        "user_id": user_id,
+        "tenant_id": tenant_id,
     }
     return jwt.encode(payload, X_SERVICE_AUTH_JWT_SECRET, algorithm="HS256")
 
@@ -94,6 +119,7 @@ async def get_github_token_for_user(ls_user_id: str, tenant_id: str) -> dict[str
         headers = {
             "X-Service-Key": service_token,
             "X-Tenant-Id": tenant_id,
+            "X-User-Id": ls_user_id,
         }
 
         payload = {
@@ -162,9 +188,10 @@ async def leave_failure_comment(
     message: str,
 ) -> None:
     """Leave an auth failure comment for the appropriate source."""
+    config = get_config()
+    configurable = config.get("configurable", {})
+
     if source == "linear":
-        config = get_config()
-        configurable = config.get("configurable", {})
         linear_issue = configurable.get("linear_issue", {})
         issue_id = linear_issue.get("id") if isinstance(linear_issue, dict) else None
         if issue_id:
@@ -175,6 +202,18 @@ async def leave_failure_comment(
             )
             await comment_on_linear_issue(issue_id, message)
         return
+    if source == "slack":
+        slack_thread = configurable.get("slack_thread", {})
+        channel_id = slack_thread.get("channel_id") if isinstance(slack_thread, dict) else None
+        thread_ts = slack_thread.get("thread_ts") if isinstance(slack_thread, dict) else None
+        if channel_id and thread_ts:
+            logger.info(
+                "Posting auth failure reply to Slack channel %s thread %s",
+                channel_id,
+                thread_ts,
+            )
+            await post_slack_thread_reply(channel_id, thread_ts, message)
+        return
     raise ValueError(f"Unknown source: {source}")
 
 
@@ -211,14 +250,15 @@ async def save_encrypted_token_from_email(
     ls_user_id = user_info.get("ls_user_id")
     tenant_id = user_info.get("tenant_id")
     if not ls_user_id or not tenant_id:
+        account_label = _source_account_label(source)
         message = (
             "🔐 **GitHub Authentication Required**\n\n"
             f"Could not find a LangSmith account for **{email}**.\n\n"
             "Please ensure this email is invited to the main LangSmith organization. "
-            "If your Linear account uses a different email than your LangSmith account, "
+            f"If your {account_label} account uses a different email than your LangSmith account, "
             "you may need to update one of them to match.\n\n"
             "Once your email is added to LangSmith, "
-            "reply to this issue mentioning @openswe to retry."
+            f"{_retry_instruction(source)}"
         )
         await leave_failure_comment(source, message)
         raise ValueError(f"No ls_user_id found from email {email}")
@@ -226,12 +266,14 @@ async def save_encrypted_token_from_email(
     auth_result = await get_github_token_for_user(ls_user_id, tenant_id)
     auth_url = auth_result.get("auth_url")
     if auth_url:
+        work_item_label = _work_item_label(source)
+        auth_link_text = _auth_link_text(source, auth_url)
         message = (
             "🔐 **GitHub Authentication Required**\n\n"
-            "To allow the Open SWE agent to work on this issue, "
+            f"To allow the Open SWE agent to work on this {work_item_label}, "
             "please authenticate with GitHub by clicking the link below:\n\n"
-            f"[Authenticate with GitHub]({auth_url})\n\n"
+            f"{auth_link_text}\n\n"
-            "Once authenticated, reply to this issue mentioning @openswe to retry."
+            f"{_retry_instruction(source)}"
         )
         await leave_failure_comment(source, message)
         raise ValueError("User not authenticated.")

apps/agent/agent/utils/slack.py

@@ -0,0 +1,323 @@
+"""Slack API utilities."""
+
+from __future__ import annotations
+
+import asyncio
+import hashlib
+import hmac
+import logging
+import os
+import time
+from typing import Any
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+SLACK_API_BASE_URL = "https://slack.com/api"
+SLACK_BOT_TOKEN = os.environ.get("SLACK_BOT_TOKEN", "")
+
+
+def _slack_headers() -> dict[str, str]:
+    if not SLACK_BOT_TOKEN:
+        return {}
+    return {
+        "Authorization": f"Bearer {SLACK_BOT_TOKEN}",
+        "Content-Type": "application/json; charset=utf-8",
+    }
+
+
+def _parse_ts(ts: str | None) -> float:
+    try:
+        return float(ts or "0")
+    except (TypeError, ValueError):
+        return 0.0
+
+
+def _extract_slack_user_name(user: dict[str, Any]) -> str:
+    profile = user.get("profile", {})
+    if isinstance(profile, dict):
+        display_name = profile.get("display_name")
+        if isinstance(display_name, str) and display_name.strip():
+            return display_name.strip()
+        real_name = profile.get("real_name")
+        if isinstance(real_name, str) and real_name.strip():
+            return real_name.strip()
+
+    real_name = user.get("real_name")
+    if isinstance(real_name, str) and real_name.strip():
+        return real_name.strip()
+
+    name = user.get("name")
+    if isinstance(name, str) and name.strip():
+        return name.strip()
+
+    return "unknown"
+
+
+def replace_bot_mention_with_username(text: str, bot_user_id: str, bot_username: str) -> str:
+    """Replace Slack bot ID mention token with @username."""
+    if not text:
+        return ""
+    if bot_user_id and bot_username:
+        return text.replace(f"<@{bot_user_id}>", f"@{bot_username}")
+    return text
+
+
+def verify_slack_signature(
+    body: bytes,
+    timestamp: str,
+    signature: str,
+    secret: str,
+    max_age_seconds: int = 300,
+) -> bool:
+    """Verify Slack request signature."""
+    if not secret:
+        return True
+    if not timestamp or not signature:
+        return False
+    try:
+        request_timestamp = int(timestamp)
+    except ValueError:
+        return False
+    if abs(int(time.time()) - request_timestamp) > max_age_seconds:
+        return False
+
+    base_string = f"v0:{timestamp}:{body.decode('utf-8', errors='replace')}"
+    expected = (
+        "v0="
+        + hmac.new(secret.encode("utf-8"), base_string.encode("utf-8"), hashlib.sha256).hexdigest()
+    )
+    return hmac.compare_digest(expected, signature)
+
+
+def strip_bot_mention(text: str, bot_user_id: str, bot_username: str = "") -> str:
+    """Remove bot mention token from Slack text."""
+    if not text:
+        return ""
+    stripped = text
+    if bot_user_id:
+        stripped = stripped.replace(f"<@{bot_user_id}>", "")
+    if bot_username:
+        stripped = stripped.replace(f"@{bot_username}", "")
+    return stripped.strip()
+
+
+def select_slack_context_messages(
+    messages: list[dict[str, Any]],
+    current_message_ts: str,
+    bot_user_id: str,
+    bot_username: str = "",
+) -> tuple[list[dict[str, Any]], str]:
+    """Select context from thread start or previous bot mention."""
+    if not messages:
+        return [], "thread_start"
+
+    current_ts = _parse_ts(current_message_ts)
+    ordered = sorted(messages, key=lambda item: _parse_ts(item.get("ts")))
+    up_to_current = [item for item in ordered if _parse_ts(item.get("ts")) <= current_ts]
+    if not up_to_current:
+        up_to_current = ordered
+
+    mention_tokens = []
+    if bot_user_id:
+        mention_tokens.append(f"<@{bot_user_id}>")
+    if bot_username:
+        mention_tokens.append(f"@{bot_username}")
+    if not mention_tokens:
+        return up_to_current, "thread_start"
+
+    last_mention_index = -1
+    for index, message in enumerate(up_to_current[:-1]):
+        text = message.get("text", "")
+        if isinstance(text, str) and any(token in text for token in mention_tokens):
+            last_mention_index = index
+
+    if last_mention_index >= 0:
+        return up_to_current[last_mention_index:], "last_mention"
+    return up_to_current, "thread_start"
+
+
+def format_slack_messages_for_prompt(
+    messages: list[dict[str, Any]],
+    user_names_by_id: dict[str, str] | None = None,
+    bot_user_id: str = "",
+    bot_username: str = "",
+) -> str:
+    """Format Slack messages into readable prompt text."""
+    if not messages:
+        return "(no thread messages available)"
+
+    lines: list[str] = []
+    for message in messages:
+        text = (
+            replace_bot_mention_with_username(
+                str(message.get("text", "")),
+                bot_user_id=bot_user_id,
+                bot_username=bot_username,
+            ).strip()
+            or "[non-text message]"
+        )
+        user_id = message.get("user")
+        if isinstance(user_id, str) and user_id:
+            author_name = (user_names_by_id or {}).get(user_id) or user_id
+            author = f"@{author_name}({user_id})"
+        else:
+            bot_profile = message.get("bot_profile", {})
+            if isinstance(bot_profile, dict):
+                bot_name = bot_profile.get("name") or message.get("username") or "Bot"
+            else:
+                bot_name = message.get("username") or "Bot"
+            author = f"@{bot_name}(bot)"
+        lines.append(f"{author}: {text}")
+    return "\n".join(lines)
+
+
+async def post_slack_thread_reply(channel_id: str, thread_ts: str, text: str) -> bool:
+    """Post a reply in a Slack thread."""
+    if not SLACK_BOT_TOKEN:
+        return False
+
+    payload = {
+        "channel": channel_id,
+        "thread_ts": thread_ts,
+        "text": text,
+    }
+
+    async with httpx.AsyncClient() as http_client:
+        try:
+            response = await http_client.post(
+                f"{SLACK_API_BASE_URL}/chat.postMessage",
+                headers=_slack_headers(),
+                json=payload,
+            )
+            response.raise_for_status()
+            data = response.json()
+            if not data.get("ok"):
+                logger.warning("Slack chat.postMessage failed: %s", data.get("error"))
+                return False
+            return True
+        except httpx.HTTPError:
+            logger.exception("Slack chat.postMessage request failed")
+            return False
+
+
+async def add_slack_reaction(channel_id: str, message_ts: str, emoji: str = "eyes") -> bool:
+    """Add a reaction to a Slack message."""
+    if not SLACK_BOT_TOKEN:
+        return False
+
+    payload = {
+        "channel": channel_id,
+        "timestamp": message_ts,
+        "name": emoji,
+    }
+
+    async with httpx.AsyncClient() as http_client:
+        try:
+            response = await http_client.post(
+                f"{SLACK_API_BASE_URL}/reactions.add",
+                headers=_slack_headers(),
+                json=payload,
+            )
+            response.raise_for_status()
+            data = response.json()
+            if data.get("ok"):
+                return True
+            if data.get("error") == "already_reacted":
+                return True
+            logger.warning("Slack reactions.add failed: %s", data.get("error"))
+            return False
+        except httpx.HTTPError:
+            logger.exception("Slack reactions.add request failed")
+            return False
+
+
+async def get_slack_user_info(user_id: str) -> dict[str, Any] | None:
+    """Get Slack user details by user ID."""
+    if not SLACK_BOT_TOKEN:
+        return None
+
+    async with httpx.AsyncClient() as http_client:
+        try:
+            response = await http_client.get(
+                f"{SLACK_API_BASE_URL}/users.info",
+                headers=_slack_headers(),
+                params={"user": user_id},
+            )
+            response.raise_for_status()
+            data = response.json()
+            if not data.get("ok"):
+                logger.warning("Slack users.info failed: %s", data.get("error"))
+                return None
+            user = data.get("user")
+            if isinstance(user, dict):
+                return user
+        except httpx.HTTPError:
+            logger.exception("Slack users.info request failed")
+    return None
+
+
+async def get_slack_user_names(user_ids: list[str]) -> dict[str, str]:
+    """Get display names for a set of Slack user IDs."""
+    unique_ids = sorted({user_id for user_id in user_ids if isinstance(user_id, str) and user_id})
+    if not unique_ids:
+        return {}
+
+    user_infos = await asyncio.gather(
+        *(get_slack_user_info(user_id) for user_id in unique_ids),
+        return_exceptions=True,
+    )
+
+    user_names: dict[str, str] = {}
+    for user_id, user_info in zip(unique_ids, user_infos, strict=True):
+        if isinstance(user_info, dict):
+            user_names[user_id] = _extract_slack_user_name(user_info)
+        else:
+            user_names[user_id] = user_id
+    return user_names
+
+
+async def fetch_slack_thread_messages(channel_id: str, thread_ts: str) -> list[dict[str, Any]]:
+    """Fetch all messages for a Slack thread."""
+    if not SLACK_BOT_TOKEN:
+        return []
+
+    messages: list[dict[str, Any]] = []
+    cursor: str | None = None
+
+    async with httpx.AsyncClient() as http_client:
+        while True:
+            params: dict[str, str | int] = {"channel": channel_id, "ts": thread_ts, "limit": 200}
+            if cursor:
+                params["cursor"] = cursor
+
+            try:
+                response = await http_client.get(
+                    f"{SLACK_API_BASE_URL}/conversations.replies",
+                    headers=_slack_headers(),
+                    params=params,
+                )
+                response.raise_for_status()
+                payload = response.json()
+            except httpx.HTTPError:
+                logger.exception("Slack conversations.replies request failed")
+                break
+
+            if not payload.get("ok"):
+                logger.warning("Slack conversations.replies failed: %s", payload.get("error"))
+                break
+
+            batch = payload.get("messages", [])
+            if isinstance(batch, list):
+                messages.extend(item for item in batch if isinstance(item, dict))
+
+            response_metadata = payload.get("response_metadata", {})
+            cursor = (
+                response_metadata.get("next_cursor") if isinstance(response_metadata, dict) else ""
+            )
+            if not cursor:
+                break
+
+    messages.sort(key=lambda item: _parse_ts(item.get("ts")))
+    return messages

apps/agent/agent/webapp.py

@@ -5,6 +5,7 @@ import hmac
 import json
 import logging
 import os
+import uuid
 from typing import Any
 
 import httpx
@@ -14,12 +15,28 @@ from langgraph_sdk import get_client
 
 from .utils.comments import get_recent_comments
 from .utils.multimodal import dedupe_urls, extract_image_urls, fetch_image_block
+from .utils.slack import (
+    add_slack_reaction,
+    fetch_slack_thread_messages,
+    format_slack_messages_for_prompt,
+    get_slack_user_info,
+    get_slack_user_names,
+    post_slack_thread_reply,
+    select_slack_context_messages,
+    strip_bot_mention,
+    verify_slack_signature,
+)
 
 logger = logging.getLogger(__name__)
 
 app = FastAPI()
 
 LINEAR_WEBHOOK_SECRET = os.environ.get("LINEAR_WEBHOOK_SECRET", "")
+SLACK_SIGNING_SECRET = os.environ.get("SLACK_SIGNING_SECRET", "")
+SLACK_BOT_USER_ID = os.environ.get("SLACK_BOT_USER_ID", "")
+SLACK_BOT_USERNAME = os.environ.get("SLACK_BOT_USERNAME", "")
+SLACK_REPO_OWNER = os.environ.get("SLACK_REPO_OWNER", "langchain-ai")
+SLACK_REPO_NAME = os.environ.get("SLACK_REPO_NAME", "open-swe")
 
 LANGGRAPH_URL = os.environ.get("LANGGRAPH_URL") or os.environ.get(
     "LANGGRAPH_URL_PROD", "http://localhost:2024"
@@ -218,6 +235,33 @@ def generate_thread_id_from_issue(issue_id: str) -> str:
     )
 
 
+def generate_thread_id_from_slack_thread(channel_id: str, thread_id: str) -> str:
+    """Generate a deterministic thread ID from a Slack thread identifier."""
+    composite = f"{channel_id}:{thread_id}"
+    md5_hex = hashlib.md5(composite.encode("utf-8")).hexdigest()
+    return str(uuid.UUID(hex=md5_hex))
+
+
+async def get_slack_repo_config(message: str, channel_id: str, thread_ts: str) -> dict[str, str]:
+    """Resolve repository configuration for Slack-triggered runs."""
+    if "repo:" in message:
+        # extract out the repo from the message assuming its in the format of repo:owner/repo
+        import re
+
+        match = re.search(r"repo:([^ ]+)", message)
+        if match:
+            repo = match.group(1)
+            owner, name = repo.split("/")
+            await post_slack_thread_reply(
+                channel_id, thread_ts, f"Using repository: `{owner}/{name}`"
+            )
+            return {"owner": owner, "name": name}
+
+    owner = SLACK_REPO_OWNER.strip() or "langchain-ai"
+    name = SLACK_REPO_NAME.strip() or "langchainplus"
+    return {"owner": owner, "name": name}
+
+
 async def is_thread_active(thread_id: str) -> bool:
     """Check if a thread is currently active (has a running run).
 
@@ -513,6 +557,120 @@ async def process_linear_issue(  # noqa: PLR0912, PLR0915
         logger.info("LangGraph run created successfully for thread %s", thread_id)
 
 
+async def process_slack_mention(event_data: dict[str, Any], repo_config: dict[str, str]) -> None:
+    """Process a Slack app mention by creating or interrupting a thread run."""
+    channel_id = event_data.get("channel_id", "")
+    thread_ts = event_data.get("thread_ts", "")
+    event_ts = event_data.get("event_ts", "")
+    user_id = event_data.get("user_id", "")
+    text = event_data.get("text", "")
+    bot_user_id = event_data.get("bot_user_id", "")
+
+    if not channel_id or not thread_ts or not event_ts:
+        logger.warning(
+            "Missing Slack event fields (channel_id=%s, thread_ts=%s, event_ts=%s)",
+            channel_id,
+            thread_ts,
+            event_ts,
+        )
+        return
+
+    reacted = await add_slack_reaction(channel_id, event_ts, "eyes")
+    if not reacted:
+        logger.debug(
+            "Unable to add eyes reaction for Slack message ts=%s in channel=%s",
+            event_ts,
+            channel_id,
+        )
+
+    thread_id = generate_thread_id_from_slack_thread(channel_id, thread_ts)
+
+    user_email = None
+    user_name = ""
+    if user_id:
+        slack_user = await get_slack_user_info(user_id)
+        if slack_user:
+            profile = slack_user.get("profile", {})
+            if isinstance(profile, dict):
+                user_email = profile.get("email")
+                user_name = (
+                    profile.get("display_name")
+                    or profile.get("real_name")
+                    or slack_user.get("real_name")
+                    or slack_user.get("name")
+                    or ""
+                )
+
+    thread_messages = await fetch_slack_thread_messages(channel_id, thread_ts)
+    if not any(str(message.get("ts")) == str(event_ts) for message in thread_messages):
+        thread_messages.append({"ts": event_ts, "text": text, "user": user_id})
+
+    context_messages, context_mode = select_slack_context_messages(
+        thread_messages, event_ts, bot_user_id, SLACK_BOT_USERNAME
+    )
+    context_user_ids = [
+        value
+        for value in (message.get("user") for message in context_messages)
+        if isinstance(value, str) and value
+    ]
+    user_names_by_id = await get_slack_user_names(context_user_ids)
+    if user_id and user_name and user_id not in user_names_by_id:
+        user_names_by_id[user_id] = user_name
+    context_text = format_slack_messages_for_prompt(
+        context_messages,
+        user_names_by_id,
+        bot_user_id=bot_user_id,
+        bot_username=SLACK_BOT_USERNAME,
+    )
+    context_source = (
+        "the previous message where I was tagged"
+        if context_mode == "last_mention"
+        else "the beginning of the thread"
+    )
+    clean_text = (
+        strip_bot_mention(text, bot_user_id, bot_username=SLACK_BOT_USERNAME)
+        or "(no text in mention)"
+    )
+    trigger_user = user_name or (f"<@{user_id}>" if user_id else "Unknown user")
+
+    prompt = (
+        "You were mentioned in Slack.\n\n"
+        f"## Repository\n{repo_config.get('owner')}/{repo_config.get('name')}\n\n"
+        f"## Triggered by\n{trigger_user}\n\n"
+        f"## Slack Thread\n- Channel: {channel_id}\n- Thread TS: {thread_ts}\n"
+        f"- Context starts at: {context_source}\n\n"
+        f"## Conversation Context\n{context_text}\n\n"
+        f"## Latest Mention Request\n{clean_text}\n\n"
+        "Use `slack_thread_reply` to communicate in this Slack thread for clarifications, "
+        "status updates, and final summaries."
+    )
+    content_blocks: list[dict[str, Any]] = [create_text_block(prompt)]
+
+    configurable: dict[str, Any] = {
+        "repo": repo_config,
+        "slack_thread": {
+            "channel_id": channel_id,
+            "thread_ts": thread_ts,
+            "triggering_user_id": user_id,
+            "triggering_user_name": user_name,
+            "triggering_user_email": user_email,
+            "triggering_event_ts": event_ts,
+        },
+        "user_email": user_email,
+        "source": "slack",
+    }
+
+    langgraph_client = get_client(url=LANGGRAPH_URL)
+    await langgraph_client.runs.create(
+        thread_id,
+        "agent",
+        input={"messages": [{"role": "user", "content": content_blocks}]},
+        config={"configurable": configurable},
+        if_not_exists="create",
+        multitask_strategy="interrupt",
+    )
+
+
 def verify_linear_signature(body: bytes, signature: str, secret: str) -> bool:
     """Verify the Linear webhook signature.
 
@@ -651,6 +809,100 @@ async def linear_webhook_verify() -> dict[str, str]:
     return {"status": "ok", "message": "Linear webhook endpoint is active"}
 
 
+@app.post("/webhooks/slack")
+async def slack_webhook(request: Request, background_tasks: BackgroundTasks) -> dict[str, str]:
+    """Handle Slack Event API webhooks for app mentions."""
+    body = await request.body()
+
+    signature = request.headers.get("X-Slack-Signature", "")
+    timestamp = request.headers.get("X-Slack-Request-Timestamp", "")
+    if SLACK_SIGNING_SECRET and not verify_slack_signature(
+        body=body,
+        timestamp=timestamp,
+        signature=signature,
+        secret=SLACK_SIGNING_SECRET,
+    ):
+        logger.warning("Invalid Slack signature")
+        raise HTTPException(status_code=401, detail="Invalid signature")
+
+    try:
+        payload = json.loads(body)
+    except json.JSONDecodeError:
+        logger.exception("Failed to parse Slack webhook JSON")
+        return {"status": "error", "message": "Invalid JSON"}
+
+    if payload.get("type") == "url_verification":
+        challenge = payload.get("challenge", "")
+        return {"challenge": challenge}
+
+    if payload.get("type") != "event_callback":
+        return {"status": "ignored", "reason": "Not an event callback"}
+
+    event = payload.get("event", {})
+    if event.get("type") != "app_mention":
+        message_text = event.get("text", "")
+        has_username_mention = bool(
+            event.get("type") == "message"
+            and SLACK_BOT_USERNAME
+            and f"@{SLACK_BOT_USERNAME}" in message_text
+        )
+        has_id_mention = bool(
+            event.get("type") == "message"
+            and SLACK_BOT_USER_ID
+            and f"<@{SLACK_BOT_USER_ID}>" in message_text
+        )
+        if not (has_username_mention or has_id_mention):
+            return {"status": "ignored", "reason": "Not an app_mention event"}
+
+    if event.get("subtype") == "bot_message" or event.get("bot_id"):
+        return {"status": "ignored", "reason": "Event from a bot"}
+
+    channel_id = event.get("channel", "")
+    event_ts = event.get("ts", "")
+    thread_ts = event.get("thread_ts") or event_ts
+    user_id = event.get("user", "")
+    text = event.get("text", "")
+    if not channel_id or not event_ts or not thread_ts:
+        return {"status": "ignored", "reason": "Missing channel/thread timestamp"}
+
+    bot_user_id = SLACK_BOT_USER_ID
+    if not bot_user_id:
+        authorizations = payload.get("authorizations", [])
+        if isinstance(authorizations, list) and authorizations:
+            auth_user_id = authorizations[0].get("user_id")
+            if isinstance(auth_user_id, str):
+                bot_user_id = auth_user_id
+    if not bot_user_id:
+        authed_users = payload.get("authed_users", [])
+        if isinstance(authed_users, list) and authed_users:
+            first_user = authed_users[0]
+            if isinstance(first_user, str):
+                bot_user_id = first_user
+
+    if bot_user_id and user_id == bot_user_id:
+        return {"status": "ignored", "reason": "Event from this bot user"}
+
+    event_data = {
+        "channel_id": channel_id,
+        "thread_ts": thread_ts,
+        "event_ts": event_ts,
+        "user_id": user_id,
+        "text": text,
+        "bot_user_id": bot_user_id,
+    }
+    repo_config = await get_slack_repo_config(text, channel_id, thread_ts)
+
+    background_tasks.add_task(process_slack_mention, event_data, repo_config)
+
+    return {"status": "accepted", "message": "Slack mention queued"}
+
+
+@app.get("/webhooks/slack")
+async def slack_webhook_verify() -> dict[str, str]:
+    """Verify endpoint for Slack webhook setup."""
+    return {"status": "ok", "message": "Slack webhook endpoint is active"}
+
+
 @app.get("/health")
 async def health_check() -> dict[str, str]:
     """Health check endpoint."""

apps/agent/tests/test_auth_sources.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+import asyncio
+
+import pytest
+
+from agent.utils import auth
+
+
+def test_leave_failure_comment_posts_to_slack_thread(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    called: dict[str, str] = {}
+
+    async def fake_post_slack_thread_reply(channel_id: str, thread_ts: str, message: str) -> bool:
+        called["channel_id"] = channel_id
+        called["thread_ts"] = thread_ts
+        called["message"] = message
+        return True
+
+    monkeypatch.setattr(auth, "post_slack_thread_reply", fake_post_slack_thread_reply)
+    monkeypatch.setattr(
+        auth,
+        "get_config",
+        lambda: {"configurable": {"slack_thread": {"channel_id": "C123", "thread_ts": "1.2"}}},
+    )
+
+    asyncio.run(auth.leave_failure_comment("slack", "auth failed"))
+
+    assert called == {"channel_id": "C123", "thread_ts": "1.2", "message": "auth failed"}

apps/agent/tests/test_slack_context.py

@@ -0,0 +1,114 @@
+from agent.utils.slack import (
+    format_slack_messages_for_prompt,
+    replace_bot_mention_with_username,
+    select_slack_context_messages,
+    strip_bot_mention,
+)
+from agent.webapp import generate_thread_id_from_slack_thread
+
+
+def test_generate_thread_id_from_slack_thread_is_deterministic() -> None:
+    channel_id = "C12345"
+    thread_ts = "1730900000.123456"
+    first = generate_thread_id_from_slack_thread(channel_id, thread_ts)
+    second = generate_thread_id_from_slack_thread(channel_id, thread_ts)
+    assert first == second
+    assert len(first) == 36
+
+
+def test_select_slack_context_messages_uses_thread_start_when_no_prior_mention() -> None:
+    bot_user_id = "UBOT"
+    messages = [
+        {"ts": "1.0", "text": "hello", "user": "U1"},
+        {"ts": "2.0", "text": "context", "user": "U2"},
+        {"ts": "3.0", "text": "<@UBOT> please help", "user": "U1"},
+    ]
+
+    selected, mode = select_slack_context_messages(messages, "3.0", bot_user_id)
+
+    assert mode == "thread_start"
+    assert [item["ts"] for item in selected] == ["1.0", "2.0", "3.0"]
+
+
+def test_select_slack_context_messages_uses_previous_mention_boundary() -> None:
+    bot_user_id = "UBOT"
+    messages = [
+        {"ts": "1.0", "text": "hello", "user": "U1"},
+        {"ts": "2.0", "text": "<@UBOT> first request", "user": "U1"},
+        {"ts": "3.0", "text": "extra context", "user": "U2"},
+        {"ts": "4.0", "text": "<@UBOT> second request", "user": "U3"},
+    ]
+
+    selected, mode = select_slack_context_messages(messages, "4.0", bot_user_id)
+
+    assert mode == "last_mention"
+    assert [item["ts"] for item in selected] == ["2.0", "3.0", "4.0"]
+
+
+def test_select_slack_context_messages_ignores_messages_after_current_event() -> None:
+    bot_user_id = "UBOT"
+    messages = [
+        {"ts": "1.0", "text": "<@UBOT> first request", "user": "U1"},
+        {"ts": "2.0", "text": "follow-up", "user": "U2"},
+        {"ts": "3.0", "text": "<@UBOT> second request", "user": "U3"},
+        {"ts": "4.0", "text": "after event", "user": "U4"},
+    ]
+
+    selected, mode = select_slack_context_messages(messages, "3.0", bot_user_id)
+
+    assert mode == "last_mention"
+    assert [item["ts"] for item in selected] == ["1.0", "2.0", "3.0"]
+
+
+def test_strip_bot_mention_removes_bot_tag() -> None:
+    assert strip_bot_mention("<@UBOT> please check", "UBOT") == "please check"
+
+
+def test_strip_bot_mention_removes_bot_username_tag() -> None:
+    assert (
+        strip_bot_mention("@open-swe please check", "UBOT", bot_username="open-swe")
+        == "please check"
+    )
+
+
+def test_replace_bot_mention_with_username() -> None:
+    assert (
+        replace_bot_mention_with_username("<@UBOT> can you help?", "UBOT", "open-swe")
+        == "@open-swe can you help?"
+    )
+
+
+def test_format_slack_messages_for_prompt_uses_name_and_id() -> None:
+    formatted = format_slack_messages_for_prompt(
+        [{"ts": "1.0", "text": "hello", "user": "U123"}],
+        {"U123": "alice"},
+    )
+
+    assert formatted == "@alice(U123): hello"
+
+
+def test_format_slack_messages_for_prompt_replaces_bot_id_mention_in_text() -> None:
+    formatted = format_slack_messages_for_prompt(
+        [{"ts": "1.0", "text": "<@UBOT> status update?", "user": "U123"}],
+        {"U123": "alice"},
+        bot_user_id="UBOT",
+        bot_username="open-swe",
+    )
+
+    assert formatted == "@alice(U123): @open-swe status update?"
+
+
+def test_select_slack_context_messages_detects_username_mention() -> None:
+    selected, mode = select_slack_context_messages(
+        [
+            {"ts": "1.0", "text": "@open-swe first request", "user": "U1"},
+            {"ts": "2.0", "text": "follow up", "user": "U2"},
+            {"ts": "3.0", "text": "@open-swe second request", "user": "U3"},
+        ],
+        "3.0",
+        bot_user_id="UBOT",
+        bot_username="open-swe",
+    )
+
+    assert mode == "last_mention"
+    assert [item["ts"] for item in selected] == ["1.0", "2.0", "3.0"]