Filestack policies must be signed server-side with a scoped, expiring policy

TL;DR

Set the call scope to exactly the operations the URL performs, a read-scoped policy will not authorize a convert. Keep expiries short and mint fresh policies per session rather than reusing long-lived ones.

Steps

1. Generate and sign Filestack policies server-side only, never in client code. Set the call scope to exactly the operations the URL performs, a read-scoped policy will not authorize a convert. Keep expiries short and mint fresh policies per session rather than reusing long-lived ones.

When to use

You are seeing this: Generate and sign Filestack policies server-side only, never in client code. Use this skill when you run into "Filestack policies must be signed server-side with a scoped, expiring policy".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Source: Web (Filestack's Claude Code plugin reference): security policies are base64-encoded JSON with a required expiry Unix timestamp and a call scope like read, write, convert, or remove, signed with HMAC-SHA256 using the app secret. The signing happens locally and the secret never leaves the machine. Agents that generate policies client-side either leak the app secret into the bundle or ship policies whose call scope does not cover the operation, and both fail in confusing ways at request time.

Verified resolution: Generate and sign Filestack policies server-side only, never in client code. Set the call scope to exactly the operations the URL performs, a read-scoped policy will not authorize a convert. Keep expiries short and mint fresh policies per session rather than reusing long-lived ones.

Source URL: https://github.com/aya11218/filestack-claude-plugin