Copperhead is 'Cursor for circuit boards,' and it's open source
Apache-2.0 CLI edits real .kicad_sch/.kicad_pcb files, runs ERC/DRC until they pass, and drives it with your Claude subscription — no API keys.
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It edits your .kicad_sch, not a chat window
Copperhead reads and edits real KiCad s-expression files and keeps markdown design docs as its memory, the way a coding agent works a repo. `copperhead create` turns a natural-language brief into spec, architecture, part selection, schematic, first-draft layout, gerbers and a firmware scaffold; `copperhead do "<change>"` iterates on an existing board.
Nothing is 'done' until ERC/DRC passes
Two hard invariants keep it honest: no edits without a documented spec, and no task finishes until it runs KiCad's ERC/DRC, reads the errors back and fixes them. That gate is what separates a plausible-looking schematic from one that actually survives fabrication.
Runs on your Claude subscription, no API keys
Point it at Claude with `--model claude-code` and it uses your saved Claude login through the Agent SDK — no separate API billing to wire up. The CLI is Apache-2.0 and runs locally for free; the hosted tier is $49/user/mo and free for open-hardware repos.
Build this weekend: a real board from one paragraph
The examples start with a USB-C power breakout as the 'hello world,' and the team's showcase — the Open Telegraph, an ESP32-S3 Morse key — was built end-to-end through the workflow. Write the brief, get gerbers and a firmware scaffold, no EE background required.
Elsewhere: the KiCad-agent space is filling fast
Copperhead isn't alone. kicad-happy (1.1k stars) packages KiCad skills for Claude Code and Codex, and native plugins like Konnect expose 217 design tools to any LLM. 'Hardware as code' is quietly becoming its own category.