Layer stack · Diagram Design

AI app stack · Where the work actually happens

Five layers between silicon and the user. Most teams over-invest in the model and under-invest in the harness — which is the layer that decides whether the app feels magical or flaky.

ABSTRACTION SILICON L5 UI surface chat, editor, canvas L4 Agent harness tools, memory, loop L3 Prompt layer system, few-shot, caching L2 SDK / client auth, retries, streaming L1 Model weights opus, sonnet, haiku FOCAL LAYER The harness is where most product differentiation actually lives — tools, memory, and the loop that stitches model calls into useful work.

THE HEADLINE

Coral marks the layer that pays rent

Swapping models is a knob. Rewriting the harness is a product decision. The coral band says: this is the layer where you out-execute the competition, not the one where you chase leaderboards.

Reading the stack

  • Abstraction rises up the left column
  • L-index on the left, note on the right
  • Hairlines between layers, no shadows
  • Fill shade shifts from paper-2 to white

Why only five

Six-plus layers become a legend, not a diagram. Five holds the whole thing on one screen — every band readable without squinting, every note a scan away.

ai app stack · layer hierarchy example · schematic skill