Prompt Engineering

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 · 11 min read

Where you edit your prompt decides what it costs

The session was fast for twenty turns, then you added one line to the top of a file and the next answer crawled. A prompt cache is keyed on an exact prefix, so cost and latency depend on where you changed something, not how much. The ordering rule that falls out of it.

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.