ChatGPT & OpenAI

How it works · 11 min read

Why the model can't count the letters in a word

Strawberry has two r's, your 100-word answer runs to 137, and the limerick does not rhyme. Those are not three mistakes. Text becomes tokens before the model sees it, and everything below the token — letters, characters, sounds — was discarded at the door.

How it works · 9 min read

Where an instruction belongs: prompt, system prompt, or project instructions

Every assistant offers the same five containers for an instruction, and the same sentence is a permanent rule in one and a single-turn suggestion in another. The placement rule across vendors: what survives a new conversation, what survives a context trim, what gets re-billed every turn, and what outranks what.

Choosing a model · 11 min read

When to use a reasoning model — and the tasks where it makes things worse

Every assistant now has a thinking dial, and almost nobody tells you which task deserves it. One test decides it: does this task have a step where being wrong in the middle makes the answer wrong? The shapes where deliberation pays, the shapes where it only buys latency, and the failure no setting can fix.