Slack File Attachments Downloading as HTML Instead of Binary Data
Running into an issue with Slack file attachments in OpenClaw 2026.2.9.
Symptoms:
- File attachments appear correctly in Koda's context with paths like /home/clawdbot/.openclaw/media/inbound/<uuid>.png
- When reading the file, instead of PNG/JPG binary data, I get HTML — specifically Slack's login/redirect page
- Example file content starts with: <!DOCTYPE html><html lang="en-US"...
- The HTML contains redirect URLs like: "redirectURL":"/files-pri/T0ADER0PR1A-F0AEC0WQ483/download/..."
Root Cause (hypothesis):
When OpenClaw fetches from Slack's url_private_download, it's not passing the bot token in the Authorization header. Slack returns a 302 redirect to the login page, and OpenClaw saves that HTML
response as the "image."
Config:
- Slack Socket Mode enabled
- Bot token configured with files:read and files:write scopes (verified in Slack app settings)
- Telegram file attachments work fine — this is Slack-specific
Question:
Is this a known issue? I searched GitHub but didn't find an existing report. According to https://api.slack.com/tokens, private file URLs require Authorization: Bearer xoxb-... headers to
download.
Symptoms:
- File attachments appear correctly in Koda's context with paths like /home/clawdbot/.openclaw/media/inbound/<uuid>.png
- When reading the file, instead of PNG/JPG binary data, I get HTML — specifically Slack's login/redirect page
- Example file content starts with: <!DOCTYPE html><html lang="en-US"...
- The HTML contains redirect URLs like: "redirectURL":"/files-pri/T0ADER0PR1A-F0AEC0WQ483/download/..."
Root Cause (hypothesis):
When OpenClaw fetches from Slack's url_private_download, it's not passing the bot token in the Authorization header. Slack returns a 302 redirect to the login page, and OpenClaw saves that HTML
response as the "image."
Config:
- Slack Socket Mode enabled
- Bot token configured with files:read and files:write scopes (verified in Slack app settings)
- Telegram file attachments work fine — this is Slack-specific
Question:
Is this a known issue? I searched GitHub but didn't find an existing report. According to https://api.slack.com/tokens, private file URLs require Authorization: Bearer xoxb-... headers to
download.
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