fable-agent/PHASES/phase-04-feedback-loop.md

Phase 4: Feedback Loop

Purpose: The core primitive — plan → execute → observe → reflect → refine. TS Module: src/tier2-primitives/loops/feedback-loop.ts

What It Does

Runs the phase machine for N iterations until convergence:

plan → execute → observe → reflect → refine
  ↑                                      │
  └──────────────────────────────────────┘

Each phase produces structured output stored in the state accumulator.

PhaseExecutor Interface

Implement this to connect any model:

interface PhaseExecutor {
  plan(task: string, previousIteration: LoopIteration | null): Promise<string>;
  execute(plan: string): Promise<string>;
  observe(executed: string): Promise<string>;
  reflect(observation: string, previousIteration: LoopIteration | null): Promise<string>;
  refine(reflection: string): Promise<string>;
}

Usage

fable-agent run "Your goal" --loop 10

Key Rules

• The executor determines the model — swap it to route phases differently
• Hooks: onPhase, onIteration, onConverge for observability
• The loop converges via rubric criteria, not iteration count