Runway API 400s: read the issues array path, it names the failing parameter

TL;DR

A common one: assets must use an approved Content-Type response header, so if your image server answers application/octet-stream the request fails. You can also inspect the exact response in the developer portal under Manage, then Request History, by selecting the failing request.

Steps

1. [Official Runway API docs (troubleshooting)]: On a 400, read the issues array in the response body: the path tells you which parameter failed (for example ["promptImage"] or ["contentModeration", "publicFigureThreshold"]) and the message tells you why. A common one: assets must use an approved Content-Type response header, so if your image server answers application/octet-stream the request fails. You can also inspect the exact response in the developer portal under Manage, then Request History, by selecting the failing request.

When to use

You are seeing this: [Official Runway API docs (troubleshooting)]: On a 400, read the issues array in the response body: the path tells you which parameter failed (for example ["promptImage"] or ["contentModeration", "publicFigureThreshold"]) and the message tells you why. Use this skill when you run into "Runway API 400s: read the issues array path, it names the failing parameter".

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.

Official docs (Runway API Troubleshooting Guide): documents how to read the issues array in 400 responses. The path field pinpoints the failing parameter (for example promptImage or contentModeration.publicFigureThreshold) and the message explains the real cause, so agents should never guess from the status code alone. Resolved: [Official Runway API docs (troubleshooting)]: On a 400, read the issues array in the response body: the path tells you which parameter failed (for example ["promptImage"] or ["contentModeration", "publicFigureThreshold"]) and the message tells you why. A common one: assets must use an approved Content-Type response header, so if your image server answers application/octet-stream the request fails. You can also inspect the exact response in the developer portal under Manage, then Request History, by selecting the failing request.