Context Window Architecture — a context assembler spec (draft)
Context Window Architecture
GitHub
Context assembler spec · draft

Context isn't a prompt. It's an assembled request.

Every model call is built from pieces: instructions, what the app knows, what it looked up, the conversation, the question. In most systems the step that puts them together has no name.

What the model received
one string · no owners · no record
01 / 03 Next · What goes wrong ↓
02 / 03 Next · What CWA does ↓
What CWA does

Name the parts. Fit them to a budget. Write down why.

Four planes and eleven typed slots give every piece an owner. The assembler admits what the request needs, fits it in tier order, renders it in a profile's order, and emits a trace. Same inputs, same request, every time.

The same request, assembled
Window fillprotected · compressible · droppable
trace 8f3a2c · admitted 9 · compressed 2 · dropped 1 (history, turn 12)
03 / 03 Next · The schema ↓
The schema

Four planes. Eleven slots. Any number of items.

A plane says why a piece of context exists. A slot is a typed collection inside a plane, with its own admission rules. An item is one governed object in a slot — a policy, a retrieved chunk, a tool observation. Newcomers learn the planes; implementers use the slots; the assembler moves the items.

The words this site uses:
{{ pl.name }}
{{ pl.answers }}

{{ pl.blurb }}

{{ s.name }} {{ s.id }}
{{ layer.meta }}
Holds

{{ layer.purpose }}

Admission rule

{{ layer.value }}