CHN File Format

CHN is Schemify's native schematic interchange format. It is designed to be human-readable, LLM-optimized, and round-trip lossless with xschem's .sch/.sym format and SPICE netlists.

Design philosophy: .chn is to xschem what TOON is to JSON — same circuit data model, different encoding, optimized for LLM consumption instead of GUI rendering.

File Types

Extension	Has SYMBOL	Has SCHEMATIC	Use
.chn	Yes	Yes	Reusable component (subcircuit)
.chn_prim	Yes	No	Leaf device backed by SPICE .lib
.chn_testbench	No	Yes	Top-level simulation harness

The type is enforced by the file extension and the parser — a testbench cannot be instantiated as a component by accident.

Core Axioms

1. Zero geometry in connectivity. Coordinates are rendering concerns, banished to a low-priority drawing: section.
2. Explicit named nets. No implicit "wires touching = connected." Every connection is a declared net -> inst.pin statement.
3. Schema-once, rows-stream. Instance lists are tabular (TOON-style): field names appear once in a header, device rows are positional.
4. [N] guardrails everywhere. Every list declares its length. Validators detect truncation, duplication, and drift.
5. Lossless round-trip. .chn ↔ xschem .sch ↔ SPICE netlist. No information is invented or destroyed.
6. Annotations are inline and timestamped. Simulation results live in the file with a freshness status, not in a sidecar.

File Structure

<header>

SYMBOL <name>
  desc: <description>
  pins [N]:
    ...
  params [N]:
    ...
  spice_prefix: <letter>

SCHEMATIC
  nmos [N]{name, w, l, nf, model}:
    ...
  nets [N]:
    ...
  annotations:
    status: fresh|stale
    ...

Token Efficiency

Circuit	Approx tokens (no annotations)	vs xschem .sch
Simple inverter	~80	5× smaller
Diff pair	~150	4× smaller
Two-stage opamp	~300	3× smaller
Full PLL (~200 devices)	~2,500	3× smaller

The same two-stage opamp in xschem .sch format ≈ 900 tokens (60% geometry waste).

Syntax Rules

Rule	Detail
Encoding	UTF-8
Comments	# to end of line
Indentation	2 spaces per level
Strings	Unquoted unless containing special chars
Expressions	{expr} — e.g. {wp*2}, {vdd/2}
Net arrow	-> separates net name from pin list
Pin reference	instance.pin — dot notation
File header	First line: chn 1.0, chn_prim 1.0, or chn_testbench 1.0
List headers	section_name [N]: — N = item count guardrail
Tabular headers	section_name [N]{col1, col2, ...}: — TOON-style