Codex 0.159.1 Swaps in GPT 6.1 Sol

Ethan Park

Here's a small mystery. You update Codex to version 0.159.1. You change nothing in your config. And your sessions start on a different model. No banner, no prompt. Which model?

Maya

Okay, I'll bite. Is it, um, one of the Sol ones?

Ethan Park

GPT 6.1 Sol. If config.toml has no model key, it used to boot GPT 6 Astra, and as of 0.159.1 it boots GPT 6.1 Sol. Oh, and quick thanks to Jellypod for helping make a daily show actually possible. Okay. Back to it.

Maya

Wait, where did that change happen?

Ethan Park

The release notes list two pull requests, 49323 and 49342. The second one covers the Amazon Bedrock catalogs, so GPT 6.1 Sol also replaces GPT 6 Sol as the default in the Bedrock Mantle and Runtime catalogs. And according to a community guide to the CLI, the model picker now lists it first, as the latest workhorse model for coding and everyday work.

Maya

Fine, but a new default is just, you know, a new default. Why does anyone care?

Ethan Park

Money. OpenAI's changelog says GPT 6.1 Sol offers near Astra performance for complex work at a lower cost than Astra. The guide puts numbers on it. 50 credits per million input tokens, 2.5 cached, 250 output. Astra is 250, 25, and 1,250.

Maya

Hold on. So that's a, a fifth of the price.

Ethan Park

Eighty percent off. Yeah.

Maya

Okay, that's not nothing.

Ethan Park

But the sneakier part is the service tier. The same guide says GPT 6 Sol and Luna ship with Fast as the default tier. On ChatGPT sign in, Fast bills at 2.5 times Standard credits. So a session where you never set a service tier could quietly start in Fast.

Maya

So people were paying a tax they didn't know existed.

Ethan Park

Possibly, yeah. GPT 6.1 Sol has no default service tier. Sessions start at Standard speed. You can check with the slash fast status command.

Maya

Huh. That's, that's honestly a bigger deal than the price table. The price you can see. The tier you can't.

Ethan Park

Right. And there's a third change. Default reasoning effort is low, where GPT 6 Sol was medium.

Maya

Oh, I felt that one. I ran it on a multi file refactor, and turns came back in seconds. The reasoning was, um, really sparse. Almost suspiciously quick.

Ethan Park

Was the result any good?

Maya

For mechanical stuff, renames, moving things around, yes. But if the job is deciding how the pieces should fit together, I'd raise the effort. Medium, high, and the SDK notes even mention an ultra value.

Ethan Park

So cheaper, slower to burn credits, and thinks less out of the box. That's the trade.

Maya

A fair trade, as long as you know you're making it.

Ethan Park

Now the catch. Does upgrading the CLI move you to 6.1 Sol?

Maya

I'd have guessed yes. New version, new model.

Ethan Park

Nope. The default only applies when config.toml names no model. If you pinned model to GPT 6 Sol, or GPT 6 Astra, you keep that. Saved choices aren't migrated.

Maya

And the older stuff? Like GPT 5.6?

Ethan Park

Per the guide, the migration prompts for the older picks, GPT 5.6 Sol, GPT 5.6 Terra, GPT 5.5, still point to GPT 6 Sol. Not 6.1. So somebody can click through a migration and land one generation behind without noticing.

Maya

Ugh. So to actually get it, you set the model key yourself, or pass the m flag on the command line.

Ethan Park

Yep. Next gotcha. Rollout covers Plus, Pro, Business, Enterprise, and Edu. But Enterprise and Edu keep it off until an administrator enables it. Free and Go aren't included at launch.

Maya

So the whole team upgrades, the admin hasn't flipped the switch, and half of them are wondering why nothing changed.

Ethan Park

Or why the model they expected isn't there. So verify. Slash status, which as of 0.159.0 renders without borders and wraps long values, or open the slash model picker and see whether 6.1 Sol is even listed.

Maya

And if it's not, pin one you do have.

Ethan Park

Right. Now, the patch train. 0.159.2 landed the same day as 0.159.1, about three and a half hours later. It's one backport, pull request 49385, and it stops Windows from flashing a console window every time Codex starts a background process.

Maya

Oh, the flashing. Shell commands, hooks, Git calls, all of it?

Ethan Park

The guide says that covers shell tool commands, hooks, Git and npm calls, doctor checks, sandbox setup refreshes. Commands that need your terminal still use it. No defaults change.

Maya

Small fix, but if you've watched windows pop up forty times during a task, you remember it.

Ethan Park

Then 0.159.3, on September 30th. Pull request 49744. The notes say eligible local sessions signed in with ChatGPT can now show optional reminders to complete account security setup.

Maya

Optional. So a nudge, not a wall.

Ethan Park

A nudge. And the clock to watch is October 14th, 2026. That's when GPT 5.5 retires from Codex for ChatGPT sign in.

Maya

So if your config still says 5.5, you've got until then to choose on purpose.

Ethan Park

Yeah. Check the config. That's it from me.