gpt-5.4 on codex cli is very reluctant, and even resistant, to reading long files

What issue are you seeing?

When using gpt‑5.4, if I force it to read an entire markdown doc (around 1,000 lines), it will occasionally run wc -l to check the line count, but every time it only reads the first 220 lines. Even if I continue asking it in follow-up turns to read the full doc, it either checks the line count with wc -l and then answers without reading anything, or insists that the 220 lines it already read are the complete file.

Switching back to gpt-5.3-codex, even without repeatedly asking it to read the entire doc, it can tell the file is long and keeps reading in multiple passes until it has consumed the full file content before answering.

What steps can reproduce the bug?

Unless I’m just extremely unlucky and happened to hit a bad case in ~10 repeated conversations, this should be reproducible by giving gpt-5.4 a markdown file longer than 1,000 lines and discussing its contents with it, even when you explicitly require it to read the entire file.

What is the expected behavior?

_No response_

Additional information

_No response_