GPT-5.6 Sol context window remains limited to 272k despite 1M configuration #40106

What version of Codex CLI is running?

26.819.11345

What subscription do you have?

pro

Which model were you using?

gpt-5.6-sol xhigh

What platform is your computer?

macOS

What terminal emulator and version are you using (if applicable)?

Terminal.app

Codex doctor report

What issue are you seeing?

Description

GPT-5.6 Sol is still limited to a 272k context window on my ChatGPT Pro account, even when I explicitly configure Codex to use the 1M context window.

According to the documented configuration, I tried both config.toml and CLI overrides, but neither changes the effective context window.

Configuration

In ~/.codex/config.toml:

model = "gpt-5.6-sol"
model_context_window = 1000000
model_auto_compact_token_limit = 900000

I also tested a fresh CLI session with:

codex -m gpt-5.6-sol
-c model_context_window=1000000
-c model_auto_compact_token_limit=900000
Actual behavior

After starting a new session and sending messages, the backend/model metadata still reports GPT-5.6 Sol with a maximum/effective context window of approximately:

272000

The requested model_context_window=1000000 does not take effect.

The same issue occurs after:

restarting Codex
starting a completely new conversation/session
logging out and logging back in
refreshing/removing the local model cache
using the configuration file
using CLI -c overrides directly

The context window remains limited to 272k.

What steps can reproduce the bug?

Uploaded thread: 01a0296b-839a-7c40-b643-59914df5741c

What is the expected behavior?

Expected behavior

GPT-5.6 Sol supports a much larger context window, and Codex has documented a configuration for enabling the 1M-token context window:

model_context_window = 1000000
model_auto_compact_token_limit = 900000

I therefore expect Codex to honor the larger context configuration instead of limiting the model to 272k.

Additional information

Possible cause

This appears to be related to server-delivered model metadata or an account-level entitlement/configuration issue.

It looks like the server returning a max_context_window of 272000 for GPT-5.6 Sol, which causes the locally configured 1M context window to be clamped back to 272k.

“slug: gpt-5.6-sol
context_window: 272000
max_context_window: 272000
effective_context_window_percent: 95”

Could you please check whether the GPT-5.6 Sol long-context capability is being correctly enabled for my ChatGPT Pro account?