RAW
LLM
reasoning
OBSERVER
STATE MANAGER
PROMPT ASSEMBLER
EXECUTION LOOP
Harness Layers
Execution loop
runs perceive/think/act/remember, enforces stop conditions + retries
Prompt assembler
builds context from system prompt, history, retrieved docs, tool results
State manager
tracks subtasks + decisions, checkpoints to durable storage
Observer
structured logging of every step, queryable by run ID