Thoughts Brewing Blog

AI Quick Tips 250: What’s New in GPT 5.1 (And What Actually Matters)

Written by Damien Griffin | Nov 18, 2025 2:30:00 PM

ChatGPT pushed out yet another set of updates, shuffled the model menu, and renamed a few things for reasons known only to OpenAI’s internal naming committee.

Lucky for you, I read the documentation so you don’t have to.

Here’s what changed — and what’s worth your attention.

If you prefer the video, watch here:

 
1. The New Default Model: GPT 5.1

If you log in today, you’ll notice the default model is now GPT 5.1 instead of GPT 5.

You still get the same three major modes:

  • Auto — The router decides which model to use (Instant or Thinking). If it switches between them, the usage doesn’t count against your limits, which is… interesting.
  • Instant — Fast responses, lighter processing.
  • Thinking — Slower, deeper reasoning, more persistence on complex tasks.

Think of it like “casual drive,” “sport mode,” and “off-road with a roof rack full of logic.”

2. GPT 5.1 Instant: Softer, Warmer, Less Robot

When GPT-5 first came out, many people said it felt colder and more robotic than GPT-4. The emotional tone dropped off a cliff.

GPT 5.1 Instant is OpenAI’s attempt to climb back up that cliff.

According to the docs, it’s now:

  • “Warmer”
  • “More intelligent”
  • “Better at following instructions”

Translation: conversations should feel more human” again, and less like you’re arguing with a politely annoyed spreadsheet.

3. GPT 5.1 Thinking: Deeper Reasoning (Allegedly)

OpenAI calls it their “advanced reasoning model.”

Their claims:

  • Easier to understand
  • Faster on simple tasks
  • More persistent on complex ones

My experience so far? It’s… fine. Not mind-blowing, not disappointing. Just fine. You’ll need to try it on your own use cases to get a feel for it.

4. Usage Limits: Where Things Get Confusing

OpenAI managed to take something simple and give it the IKEA treatment.

Here are the numbers in plain English:

For GPT 5.1 Instant

  • Free: 10 messages per 5 hours
  • Plus: 160 messages per 3 hours
  • Business / Pro: “Unlimited” (which actually means “until we think you’re being weird about it”)
  • Enterprise: Likely unlimited, but not actually stated

For GPT 5.1 Thinking

  • Free: No access
  • Plus: 3000 messages per week
  • Business / Pro: “Unlimited”
  • Enterprise: Again, presumably unlimited

And if Auto switches models for you, that usage doesn’t count toward your limits at all. Make of that what you will.

5. Context Windows: How Much It Can Remember

If you’re wondering how many tokens you get before ChatGPT starts forgetting everything you said like it’s rebooting an Etch A Sketch:

GPT 5.1 Instant

  • Free: 16K
  • Plus/Business: 32K
  • Pro/Enterprise: 128K

GPT 5.1 Thinking

  • All paid tiers: 196K

Compared to competitors:

  • Gemini: up to 1–2 million
  • Claude: 400K to ~1 million depending on the model

So 196K isn’t wild, but it’s better than before, and most users won’t hit that ceiling unless they’re feeding it a mid-sized codebase.

6. Personalization: Mostly Renaming, Not New Features

If you click your menu (bottom left as of today, but OpenAI likes to move things around), you’ll see updated names for tone settings.

Notable changes:

  • Friendly (used to be Reader/Listener)
  • Efficient (used to be “Robot,” which may have offended the robots)

These seem like label changes, not behavior changes.

The docs mention you can now adjust “how concise, warm, or scannable results are” and control emoji usage, but that option doesn’t actually exist in the UI yet. Maybe soon. Maybe never. Hard to say.

 

A few minor changes from the step-by-step presented in this article I published a few days ago.

 
7. Legacy Models: Still Here (For Now)

If you miss the GPT-5 era — I won’t judge — you can still manually switch back to:

  • 5 Instant
  • 5 Thinking
  • 5 Thinking Mini
  • Various other older models (too many to list here)

Free users can’t choose models; paid users can.

Final Thoughts

GPT 5.1 isn’t revolutionary ( if it were, they’d call it 5.5 or 6.0 ) but it’s a meaningful update:

  • Warmer conversations
  • Better reasoning model
  • Clear(ish) usage limits
  • Larger (but not giant) context windows
  • Minor personalization tweaks

Try Instant and Thinking on a few of your real tasks and see what fits. Most people will notice small quality-of-life improvements more than big breakthroughs.

Let us know how it works for you.