Signal Pattern Selection

Decision Flow

Start with S1 (Zero-Shot). Upgrade only when you can measure the gap.

Is format control or style matching the core problem?
  → S2 (Few-Shot): static examples if possible; dynamic only if required
    ⚠ Dynamic S2 breaks prefix cache for all upstream stable patterns

Does the task need domain expertise framing or a specific tone?
  → S3 (Persona): bundle with S5/S6/S9 in a single stable system prompt

Are there specific behaviours the model must never exhibit?
  → S5 (Constraint Framing): explicit prohibition list alongside task description

Does a downstream system need consistent structured output?
  → S6 (Output Template): output skeleton in system prompt

Does the task have multiple steps where order matters?
  → S4 (Instruction Decomposition): numbered steps in the instruction

Do values or principles need runtime enforcement?
  → S9 (Constitutional Framing): self-critique loop against explicit principles

Does the prompt itself need to be optimised automatically?
  → S8 (Meta-Prompt): requires V15 (LLM-as-Judge) or R17 as evaluator
    ⚠ Measure cost before using; much more expensive than S1–S6/S9

Caching Guide

S3, S5, S6, and S9 are setup-band patterns. Bundle them together in a single stable system prompt — this is the cacheable prefix unit. Provider prefix caching (Anthropic: ~5 min TTL, ~10% cost on cache hits) reduces the cost of this bundle to near-zero for all calls within the TTL window.