// Section 1 — The Model · 2 MIN READ
Model★
A model is a mathematical file containing billions of floating-point weights (parameters). It acts as a stateless, pure function: it accepts a sequence of input tokens and returns a probability distribution for the next token.
Day-to-day developers often conflate the model with the harness (the application code surrounding it). Mechanically, a model has no agency:
- It cannot read your workspace files.
- It cannot execute console commands.
- It cannot remember prior requests or yesterday's conversation.
- It has no internal timer or clock.
All apparent "agentic" capabilities are orchestrations run by the harness, which calls the model in a loop, parses its output strings, and feeds tool results back as fresh input tokens.
Configuration in code
When setting up APIs, always select the model tier based on the task requirement (heavy planning vs fast execution):
// Configured in a Node.js harness
const plannerModel = "claude-3-5-sonnet"; // Large parameter count, high reasoning
const parserModel = "claude-3-5-haiku"; // Smaller parameter count, low latency
# AVOID
Do not blame the model for failures in state preservation or loop execution. That is a harness responsibility.
- Avoid: "The model forgot my previous file modifications."
- Write: "The harness failed to append the file changes back into the context window for the next turn."
# USAGE
Developer A: "Why is this model not executing my git commit command?"
Developer B: "Because the model is just a stateless parameters file. You need to verify if the client harness parsed the tool call correctly and ran the child shell process on your terminal."
// SEE_ALSO
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