Chrome Use blocks top-level application/json navigation with ERR_BLOCKED_BY_CLIENT

Summary

When Chrome Use is attached, direct top-level navigation to a URL that returns application/json is blocked with ERR_BLOCKED_BY_CLIENT.

This reproduces with the public endpoint:

https://httpbin.org/json

The same endpoint returns 200 application/json through curl and browser fetch, while ordinary text/html navigation works.

Environment

• Codex Chrome plugin/runtime: 26.715.72359
• Chrome: 150.0.7871.129
• macOS: 27.0 (arm64)

Steps to reproduce

1. Connect Chrome Use to Chrome.
2. Navigate the active tab directly to https://httpbin.org/json.
3. Observe the navigation failure.

Expected behavior

Chrome displays the JSON document. If direct JSON documents are intentionally unsupported, Chrome Use should return a specific unsupported-content diagnostic instead of a generic client-blocking error.

Actual behavior

Chrome shows:

ERR_BLOCKED_BY_CLIENT

The sanitized CDP failure signal reports:

blockedReason: inspector

Additional findings

Inspection of the bundled runtime indicates that top-level Document responses are intercepted. Its inline-view MIME allowlist includes text/html, application/pdf, image/*, and video/*, but not JSON. The response therefore appears to be classified as download content, after which the runtime invokes Fetch.failRequest with BlockedByClient.

A possible fix would be to allow application/json and, if appropriate, application/*+json when the response does not specify Content-Disposition: attachment. Alternatively, the runtime could surface an explicit unsupported-document error.

Related issue

Possibly related to #30687, which covers an HTML response without a Content-Type header. This report is distinct because the affected response has a valid application/json content type.