Slack · api · fg-0358

files.upload stops working and returns method_deprecated after the November 2025 sunset

method_deprecated from files.upload

Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100

Cause

Slack retired files.upload in favor of a two step external upload flow. Apps created after 2024-05-16 lost it first, and the method stopped working for everyone on 2025-11-12.

Fix

Switch to files.getUploadURLExternal plus files.completeUploadExternal, or the SDK v2 helpers (filesUploadV2 in Node, files_upload_v2 in Python).

Apply

client.files_upload_v2(channel="C0123456789", file="report.pdf", title="Report")

Affects: Slack Web API, all apps from 2025-11-12; apps created on or after 2024-05-16 earlier

Sources

https://docs.slack.dev/changelog/2024-04-a-better-way-to-upload-files-is-here-to-stay/

Have your agent know this before it fails

claude mcp add --transport http footgun https://getfootgun.com/api/mcp