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.trace/rules.md is a plain Markdown file that tells the AI how you want to design. Write your preferences once; the AI follows them every session — no repeating yourself.
For a full conceptual overview, examples, and best practices, see Core Concepts → TraceRules.

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File Location

my-project/
├── my-board.kicad_sch
├── my-board.kicad_pcb
└── .trace/
    ├── rules.md       ← Your preferences (you edit this)
    └── context.md     ← AI-maintained notebook (AI edits this)
The AI loads rules from the first file it finds, in priority order:
  1. .trace/rules.md (recommended)
  2. .tracerules in the .kicad_pro directory
  3. .tracerules in the project root

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What You Can Configure

CategoryExample Rules
Placement strategy”Place decoupling caps within 2mm of IC power pins”, “Group by functional block”
Manufacturer target”Preferred fab: JLCPCB 4-layer”, “Min trace width: 6mil”, “Surface finish: ENIG”
Passive sizes”0402 imperial default”, “0201 where space-constrained”
Clearance & trace width”Power traces: minimum 20mil for 1A”, “USB diff pair: 90Ω impedance”
Thermal relief”Thermal relief on all ground pads”, “Direct connect for high-current pads”
DRC ignore categories”Ignore silkscreen overlap warnings”, “Skip courtyard checks on test points”
Routing conventions”No acute angles on high-speed signals”, “Route clocks on inner layers”
Component preferences”Prefer parts with JLCPCB stock”, “AEC-Q200 rated passives”

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Quick Setup

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From the Desktop App

Open the TraceRules editor from the chat panel menu: ⋮ → TraceRules

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From the CLI

buildwithtrace rules init                    # create starter .trace/rules.md
buildwithtrace rules set "Use 0402 passives" # append a rule
buildwithtrace rules show                    # print current rules
buildwithtrace rules edit                    # open in $EDITOR

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By Hand

Create .trace/rules.md in your project and write in plain Markdown: 
# Design Rules

## Manufacturer
- Fab: PCBWay 4-layer, 1.6mm, 1oz copper
- Min trace/space: 0.127mm/0.127mm
- Min via: 0.3mm drill, 0.6mm pad

## Components
- Passives: 0402 imperial
- All parts must be in-stock at LCSC

## Layout
- Decoupling caps within 2mm of power pins
- USB connector on top edge
- Programming header accessible without disassembly

## Routing
- USB: 90Ω differential impedance
- Power: 0.5mm minimum width
- SPI clock: inner layer preferred

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How the AI Uses Rules

Every time you start a conversation, the AI:
  1. Reads .trace/rules.md for your explicit preferences
  2. Reads .trace/context.md for accumulated project knowledge
  3. Applies manufacturer DFM constraints if you’ve specified a fab
  4. Follows your conventions throughout the session
If a rule conflicts with electrical safety or engineering best practices, the AI prioritizes correctness and explains why.

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Workspace Context (.trace/context.md)

This companion file is maintained by the AI automatically. It acts as a design notebook that persists learnings across conversations:
  • Component decisions and rationale
  • Custom-generated symbols and footprints (parts created from a datasheet or by request, rather than pulled from a library)
  • Layout constraints discovered during routing
  • DFM feedback from previous manufacturing attempts
  • Design history and tradeoffs
You can read it to see what the AI has learned, but generally should not edit it — the AI keeps it current. Each project has its own independent context file.

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Tips

Be specific. “Use 10K pull-ups on I2C” is better than “use appropriate pull-ups.” Concrete rules produce consistent results.
Layer preferences by priority. Put your most important constraints first — the AI weighs earlier rules more heavily when resolving conflicts.
Combine with DRC Import. Import your manufacturer’s .kicad_dru file to get machine-checked constraints in addition to your natural-language preferences. See DRC Import.