slack-attach

name	slack-attach
description	Attach ANY file to the current Slack thread — text or binary. A log, a diff, a CSV, a long answer as a snippet, and equally a PDF, a PNG, a zip, a sqlite db, a tarball: the bytes go up unchanged. TRIGGER when the user asks you to attach, upload, or send a file, or when an answer is too long or too structured to read as a message (a full log, a wide table, hundreds of lines of output) and a file reads better than a wall of text. Also TRIGGER when the user asks for something "as a file", "as a snippet", "as an attachment", or "upload that". Write the content to a file first with Bash, then attach it. This is NOT for charts (use slack-chart) or generated images (use slack-image) — those render and upload on their own. This is NOT for ordinary replies: a short answer belongs in the message, not in an attachment.
allowed-tools	Bash
argument-hint	--path <FILE> [--title "<shown as the file title>"] [--comment "<message posted with it>"]

slack-attach

Uploads a file from disk into the thread this turn is running in, using Slack's files.getUploadURLExternal → upload → files.completeUploadExternal flow.

Any file type. The bytes are sent as-is — Slack is told the byte length up front and the file is POSTed raw, so a PDF, an image, an archive or a database arrives intact. Nothing is re-encoded as text.

bun features/slack/skills/slack-attach/scripts/index.ts \
  --path /tmp/deploy.log \
  --title "deploy.log" \
  --comment "The failing run, in full."

The thread comes from $SLACK_CHANNEL_ID / $SLACK_THREAD_TS. There is no --channel: a file goes to the conversation that asked for it.

Attaching an answer as a snippet

Write it, then attach it:

cat > /tmp/answer.md <<'TXT'
| stage | status |
| ----- | ------ |
| dedup | ok     |
TXT
bun features/slack/skills/slack-attach/scripts/index.ts \
  --path /tmp/answer.md --title "Pipeline stages"

Slack renders .md, .txt, .json, .csv and source files as previewable snippets, so a long or wide answer stays readable instead of being flattened into message text.

Binary example

bun features/slack/skills/slack-attach/scripts/index.ts \
  --path /tmp/q3-report.pdf --comment "Q3, signed off."

Flags

• --path (required) — the file to upload. Read by the daemon, which runs on this host.
• --title — the file's title in Slack. Defaults to the filename.
• --comment — a message posted alongside the file.

Prints {"ok":true,"permalink":"https://..."} and exits 0. Exits 1 with a reason on failure.

When it refuses

• cannot read <path> (HTTP 422) — the path does not exist or is not readable. Check the file was written before attaching it.
• Slack refused the upload (HTTP 502) — Slack rejected the file. The cause is logged by the daemon.
• No thread in scope — SLACK_CHANNEL_ID / SLACK_THREAD_TS unset.

The upload leg is given two minutes before it is abandoned, so a very large file over a slow link can time out; the workspace's own file size limit applies on top of that.