GitHub - theletterf/claude64: Commodore 64 client for Claude

A Claude chat client for the Commodore 64.

Type a message on the C64, get a streaming response from Claude — over a real (emulated) RS-232 serial connection.

 C64 (VICE)                proxy (Python)             Anthropic API
 ──────────────            ──────────────             ─────────────
 claude64.prg  ←─ IP232 ─→ claude_proxy.py  ←─ HTTPS ─→ claude-haiku
 Swiftlink drv    TCP       127.0.0.1:25232

The C64 side is a ~200-byte-per-turn chat UI written in C and compiled with cc65. The proxy handles IP232 framing, conversation history, and streaming the Anthropic Messages API back to the C64 one character at a time.

Requirements

Tool	Purpose
cc65 (`cl65`)	Cross-compiler for the C64
VICE (`x64sc`)	C64 emulator
Python 3.9+	Proxy server
Anthropic API key	`ANTHROPIC_API_KEY` env var

Build

Produces c64/build/claude64.prg and copies the Swiftlink driver to c64/build/c64-swlink.ser.

Run

export ANTHROPIC_API_KEY=sk-ant-...
./scripts/run.sh

This starts the proxy and launches VICE in one step. The C64 loads the Swiftlink driver from device 8, connects, and shows the chat prompt.

Usage

Type a message and press Return to send. The response streams in as it arrives. Press RUN/STOP to cancel the current input line. Press F1 to clear the screen.

Built-in debug commands:

Command	What it does
`/rx`	Send the current line and hex-dump the raw bytes received
`/raw`	Same but print printable ASCII instead of hex
`/local`	Enter offline echo mode (no API calls); `/exit` to leave

Echo mode (no API key needed)

Echoes input back without calling Anthropic. Useful for testing the serial link and UI without spending tokens.

License

MIT — see LICENSE.