MODULE 05 · INCLUDED IN FOUNDATIONS

The brain: Claude

What this module is

The model choice, the system prompt, the call itself, three layers of memory, and cost control. This is where the character's personality actually lives.

What you'll build

A Claude Haiku call that returns a one-line, in-character reply with an emotion tag
A cached system prompt so input cost drops 80–90%
Working, session and long-term memory
Hard spend limits and per-hour token caps

Lessons

01Model choice
02The system prompt
03The call
04Memory
05Cost control

Checkpoint

reply() returns an in-character, correctly formatted [emotion] answer in under 1.5 seconds, and the Anthropic console shows cache hits.

The system prompt template, annotated

This section contains the full written walkthrough for this part of the module.

It includes the step-by-step instructions, the settings to change, and the reasoning behind each choice.

Screenshots and short clips show exactly what the screen should look like at every stage.

The commands and configuration files are provided in full so you can copy them directly.

Common failure points are listed with the fix for each one, in the order you are likely to hit them.

A short recap closes the section with the one thing that must be working before you move on.

Everything here is tested on the reference build before it is published to the program.

Locked

Included in Foundations

Unlock with Foundations — $847

The call code (src/brain.py) with prompt caching

This section contains the full written walkthrough for this part of the module.

It includes the step-by-step instructions, the settings to change, and the reasoning behind each choice.

Screenshots and short clips show exactly what the screen should look like at every stage.

The commands and configuration files are provided in full so you can copy them directly.

Common failure points are listed with the fix for each one, in the order you are likely to hit them.

A short recap closes the section with the one thing that must be working before you move on.

Everything here is tested on the reference build before it is published to the program.

Locked

Included in Foundations

Unlock with Foundations — $847

The three memory layers and what never gets stored

This section contains the full written walkthrough for this part of the module.

It includes the step-by-step instructions, the settings to change, and the reasoning behind each choice.

Screenshots and short clips show exactly what the screen should look like at every stage.

The commands and configuration files are provided in full so you can copy them directly.

Common failure points are listed with the fix for each one, in the order you are likely to hit them.

A short recap closes the section with the one thing that must be working before you move on.

Everything here is tested on the reference build before it is published to the program.

Locked

Included in Foundations

Unlock with Foundations — $847

Cost control: limits, caps and what a streamed hour actually costs

This section contains the full written walkthrough for this part of the module.

It includes the step-by-step instructions, the settings to change, and the reasoning behind each choice.

Screenshots and short clips show exactly what the screen should look like at every stage.

The commands and configuration files are provided in full so you can copy them directly.

Common failure points are listed with the fix for each one, in the order you are likely to hit them.

A short recap closes the section with the one thing that must be working before you move on.

Everything here is tested on the reference build before it is published to the program.

Locked

Included in Foundations

Unlock with Foundations — $847