ChatGPT app rejects custom `base_url` / `auth` in `[model_providers.amazon-bedrock]` (only `aws.profile` and `aws.region` accepted)

Summary

The ChatGPT macOS app (version 26.715.x) validates ~/.codex/config.toml more strictly than the npm CLI. When [model_providers.amazon-bedrock] contains fields other than aws.profile and aws.region (e.g. base_url, usesCodexManagedCredentials, or an [auth] subsection), the app refuses to open the thread and displays:

ChatGPT can't load config.toml, so this thread can't resume. Fix config.toml: model_providers.amazon-bedrock only supports changing aws.profile and aws.region; other non-default provider fields are not supported. After saving the file, reopen the thread.

Context

PR #33695 (rust-v0.145.0) introduced support for base_url, auth, and usesCodexManagedCredentials overrides on the amazon-bedrock provider, resolving issue #28902. This works correctly with the npm CLI (codex exec) but is blocked by the ChatGPT app.

The intended use case is routing the amazon-bedrock provider through a custom endpoint (e.g. a local proxy that handles authentication):

model_provider = "amazon-bedrock"
model = "gpt-5.6-luna"

[model_providers.amazon-bedrock]
base_url = "http://localhost:9876"
usesCodexManagedCredentials = false

[model_providers.amazon-bedrock.auth]
command = "/bin/cat"
args = ["/path/to/token"]
timeout_ms = 5000
refresh_interval_ms = 300000

This config works end-to-end with the npm CLI (Mantle response received correctly via the custom base_url) but is rejected by the ChatGPT app.

Request

Could the ChatGPT app be updated to allow the same [model_providers.amazon-bedrock] fields that the CLI accepts (specifically base_url, usesCodexManagedCredentials, and the [auth] subsection introduced in #33695)?

If the restriction is intentional for security reasons in the app context, it would be helpful to document which fields are supported per runtime (app vs CLI) so developers can plan accordingly.

Environment

• ChatGPT app: 26.715.72028
• Codex CLI: 0.145.0 (npm)
• macOS: Darwin 25.5.0 (aarch64)