Show HN: Copperhead – Cursor for circuit boards | AI Paper Digest

TL;DR Highlight

Open-source PCB design agent that only advances when KiCad checks pass

Who Should Read

Embedded and hardware developers who want an LLM agent to keep schematics and docs from drifting apart

Core Mechanics

It stops when a gate fails
- copperhead is an open-source AI agent for PCB design, installed with npm i -g copperhead.
- Each stage must leave its artifact on disk before the next starts, and a failed gate stops the run.
Eight stages from brief to package
- Stages are spec, architecture, parts, schematic, layout, outputs, firmware and dev plan, each its own agent run.
- Each stage gets one commit.
Drift is the core problem
- One decision spreads across schematic, BOM, power budget and docs, and nothing breaks when they diverge.
- Finding it at bring-up means a respin costing $5,000 to $50,000 and six to eight weeks, per the site.
Validated proposal before any edit
- It refuses to edit design files before a validated change proposal exists.
- It refuses changes that break a documented budget or constraint, citing the line.
- It refuses to run on a dirty git tree.

Community Reactions

Opinion: look at tscircuit
- One commenter says KiCad wasn't built for AI-generated designs with auto routing/placement or footprint orientation checks.
- They worry everyone is getting bound to KiCad s-expressions.
Pushback: general agents may be enough
- Commenters report editing and debugging KiCad schematics with Claude and Gemini and finding it pretty good.
- Another says regular coding agents handle Skidl schematics and layout review well.
Placement is still NP-hard
- One commenter says the real question is whether LLMs beat classical autorouters.
- Another tested Astra over a weekend and found it could edit schematics and route, though the routing was unsatisfying.
Complaints about copy and a bug
- Several commenters disliked the site's AI-written copy.
- One reported inputs in Start a board not accepting text on desktop Chrome on macOS.

How to Apply

Run init on an existing design repo
- In a clean git repo with KiCad files, run npm i -g copperhead and then copperhead init.
- Request one small change and check how small the diff is.
Add stage gates to your own agent
- Require an artifact on disk and a passing check before each pipeline stage starts.
- Stop the run and skip the commit when a check fails.
Add a proposal check before edits
- Make the agent write a change proposal first and compare it to documented constraints.
- Reject violations by quoting the line they would break.

Try It

copy & run

# Paste into Claude or ChatGPT (simplified prompt version of copperhead's verify-first approach)

You are a design assistant that verifies before changing. Read the design docs below and handle the request.

[Design docs]
{{docs}}

[Request]
{{change request}}

Follow this order.
1. Write a change proposal first, listing affected docs, parts and budgets.
2. If it breaks a documented constraint or budget, quote the violated line and stop.
3. If it passes, give the edit.
4. Finally check for inconsistencies between docs and write a one-line decision record.

Next: send a request that deliberately breaks a budget and see whether it refuses.

Terminology

ERC/DRCElectrical and design rule checks. Like a linter and compiler warnings for schematics and board layout.

driftSchematic, BOM and docs falling out of sync. Like code and comments diverging.

BOMBill of Materials, the table of part numbers and quantities that go on the board.

GerberThe manufacturing file format sent to the fab. Like a build artifact for the board.

bring-upThe first power-on and testing of a fabricated board.

Show HN: Copperhead – Cursor for circuit boards