Support public text/markdown and text/csv resources in the web open tool

What variant of Codex are you using?

Codex Desktop on Windows, using the built-in web tool's open operation.

What feature would you like to see?

Please support public text/markdown and text/csv resources in the web reader, exposing their textual content with appropriate size limits and the existing URL access checks.

Currently these formats require switching to an HTML version or using a separate HTTP download. This is a small usability limitation.

Reproducible examples

Reproduced on September 13, 2026 with this web tool input:

{
  "open": [
    {"ref_id": "https://learn.chatgpt.com/docs/agent-configuration/agents-md.md"},
    {"ref_id": "https://www.wpallimport.com/wp-content/uploads/2014/12/BurtonSacks.csv"}
  ]
}

The reader reports, respectively:

• (400) Unsupported content-type: text/markdown
• (400) Unsupported content-type: text/csv

The first URL is official OpenAI documentation; the second is a public WP All Import sample. Earlier observations on September 11–12 produced the same errors. HTML documentation pages worked, and an ordinary HTTP download of the CSV succeeded.

Scope

This is a request for expanded format support, not a claim that previously documented support regressed. The tool's displayed (400) does not establish that the origin websites returned HTTP 400.

This concerns the built-in web reader, a different tool and error from Browser Use's ERR_BLOCKED_BY_CLIENT reports such as #38369.

Start by locating the built-in web tool's open operation and its content-type handling. Inspect how existing URL access checks and size limits are applied, then verify that public text/markdown and text/csv resources expose textual content without changing those checks. Done means both supplied resource types are readable and their limits and access behavior remain covered by tests.