| name | slack-image-upload |
| description | Upload images/files to Slack ALWAYS into the current thread (never straight to the channel), using the
3-step external upload API (files.getUploadURLExternal → PUT → files.completeUploadExternal) with
thread_ts extracted from HERMES_SESSION_KEY. Load whenever posting an image, chart, or file to Slack.
|
| version | 1.0.0 |
| author | gohan (via Claude Code tuning) |
| license | MIT |
| platforms | ["linux"] |
| metadata | {"hermes":{"tags":["slack","image","upload","thread","files"]}} |
Slack Image Upload (thread-safe, 3-step API)
Rule: ALWAYS post to the current thread. NEVER post directly to the channel.
Context extraction
- Session/thread info lives in
HERMES_SESSION_KEY, format: agent:main:slack:group:{channel_id}:{thread_ts}
- Bot token: env var
SLACK_BOT_TOKEN
The 3 steps
files.getUploadURLExternal — get upload_url + file_id (params: filename, length in bytes)PUT the raw file bytes to upload_urlfiles.completeUploadExternal — MUST include BOTH channel_id AND thread_ts
Working script template
FILE=~/.hermes/workspace/chart.png
KEY="$HERMES_SESSION_KEY"
CHANNEL=$(echo "$KEY" | awk -F: '{print $(NF-1)}')
THREAD_TS=$(echo "$KEY" | awk -F: '{print $NF}')
LEN=$(stat -c%s "$FILE")
RESP=$(curl -s -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
"https://slack.com/api/files.getUploadURLExternal?filename=$(basename $FILE)&length=$LEN")
UPLOAD_URL=$(echo "$RESP" | jq -r .upload_url)
FILE_ID=$(echo "$RESP" | jq -r .file_id)
curl -s -X PUT -H "Content-Type: application/octet-stream" --data-binary @"$FILE" "$UPLOAD_URL"
curl -s -X POST https://slack.com/api/files.completeUploadExternal \
-H "Authorization: Bearer $SLACK_BOT_TOKEN" \
-H "Content-Type: application/json" \
-d "{\"files\":[{\"id\":\"$FILE_ID\",\"title\":\"$(basename $FILE)\"}],\"channel_id\":\"$CHANNEL\",\"thread_ts\":\"$THREAD_TS\"}"
Failure modes
- Missing
thread_ts in step 3 → image lands in the channel (forbidden here) — always pass both fields
invalid_auth → check SLACK_BOT_TOKEN is the Bot token (xoxb-), not an app-level token- If the session key has no thread part (DM), pass only
channel_id
