[BUG] Claude Slack app ignores thread context and searches claude.ai chat history instead

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Note: this bug affects the Claude for Slack official app (chat mode), not Claude Code CLI. The form fields above do not apply.

When @Claude is mentioned inside a Slack thread, the bot is expected to read the thread context automatically. Instead, it searches the user's claude.ai conversation history and asks for clarification about which topic the user is referring to — even when the topic is fully contained in the thread where the bot was mentioned.

What Should Happen?

Claude should read the messages in the Slack thread where it was mentioned and use that as context, without requiring the user to paste a direct link to the thread.

Error Messages/Logs

<img width="740" height="1339" alt="Image" src="https://github.com/user-attachments/assets/7a964e0f-af40-4eb7-8e85-9644344ec137" />

Steps to Reproduce

1. Start a thread in a Slack channel where Claude is invited
2. Have several messages in the thread discussing a specific topic (e.g. an alerting configuration issue)
3. Mention @Claude what do you recommend? in the thread
4. Claude responds asking for more context, presenting a list of topics from the user's claude.ai history
5. Explicitly tell Claude: @Claude read the thread you were mentioned in and recommend a plan of action
6. Claude responds again searching chat history and listing topics from claude.ai — not from the current Slack thread

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

N/A - Slack app bug

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

The official documentation states: "From threads: When you @mention Claude in a thread, it gathers context from all messages in that thread." This behavior is not occurring.