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c64bridge

C64 Bridge MCP server for Commodore 64 Ultimate hardware and VICE emulator control

Source

npm

Version: 0.9.3

Version published: 2 months ago

Weekly downloads: 46

Maintainers: 1

Weekly downloads

Created: 11 months ago

Source

C64 Bridge

Your AI Command Bridge for the Commodore 64.

C64 Bridge is an MCP server for controlling and working with a Commodore 64 from an AI client.

It lets you run programs, read and write memory, render graphics, and play sound on a real Commodore 64 Ultimate or Ultimate 64. You can also switch to a VICE emulator session at any time, so the same MCP conversation works with both hardware and emulator.

It is built on the official TypeScript @modelcontextprotocol/sdk and supports both stdio for local AI integration and an optional HTTP bridge for manual inspection.

C64 Bridge is listed in the Official MCP Registry.

C64 Bridge

Overview

C64 Bridge gives an AI agent one place to drive program execution, memory access, graphics, sound, storage, printer workflows, and knowledge retrieval for a Commodore 64 environment.

The core workflow is simple:

Start the MCP server.
Point it at C64 Ultimate hardware, VICE, or both.
Let the client call grouped MCP tools such as c64_program, c64_memory, c64_graphics, and c64_sound.
Switch backends at runtime with c64_select_backend when both are configured.

Features

Program runners for BASIC, 6510 assembly, and PRG or CRT execution
Full memory access, including raw reads and writes plus screen polling
System integration for drives, files, printers, and task orchestration
SID music tools for playback, composition, generation, and verification
Built-in knowledge resources and prompts for safer LLM workflows
Mixed runtime support for hardware c64u and emulator vice

Quick Start

If you want the shortest path, do these four things:

Install Node.js 24+ and npm.
Start the server.
Add backend configuration for C64 Ultimate, VICE, or both.
Connect from VS Code or another MCP client.

1. Install Node.js 24+ and npm

Linux (Ubuntu or Debian):

Recommended:

sudo apt update
sudo apt install -y curl ca-certificates
curl -fsSL https://deb.nodesource.com/setup_24.x | sudo -E bash -
sudo apt install -y nodejs

Fallback:

sudo apt install -y nodejs npm

macOS:

brew install node@24
brew link --overwrite node@24

Windows:

# winget
winget install OpenJS.NodeJS.LTS
# or Chocolatey
choco install nodejs-lts -y

Verify the installation:

node --version

Expected result: v24.x

2. Start the Server

Use one of the following entry points.

Run from npx with zero setup:

npx -y c64bridge@latest

Run from a local npm install:

mkdir -p ~/c64bridge && cd ~/c64bridge
npm init -y
npm install c64bridge
node ./node_modules/c64bridge/dist/index.js

Run from source for development or testing:

git clone https://github.com/chrisgleissner/c64bridge.git
cd c64bridge
./build install
npm start

On startup, the server probes the selected target, performs connectivity checks, and then announces that it is running on stdio.

3. Add Backend Configuration

The server can run against:

only C64 Ultimate hardware
only VICE
both backends in one session, with runtime switching

The detailed lookup order, merge rules, backend examples, and override model are in the Configuration section below.

4. Connect from an MCP Client

C64 Bridge ships a single canonical stdio entry point that every MCP client uses:

VS Code (GitHub Copilot) — see VS Code MCP Setup.
Claude Code (CLI and VS Code plugin) — see Claude Code.
Cursor, Visual Studio, VS Code Insiders — use the install badges at the top of this README.
Any other MCP client — point it at the same stdio server, with the environment variables documented in Runtime Environment Variable Reference and the registry manifest in mcp.json.

The startup command is the same across clients: npx -y c64bridge@latest for the published package, or node scripts/start.mjs from a local checkout. Backend selection (c64u vs vice) and credentials live in the shared Configuration files and environment variables — clients only need to know the command.

Configuration

Configuration File Order

The server reads configuration in this order:

C64BRIDGE_CONFIG, if it points to a config file
.c64bridge.json in the project root
~/.c64bridge.json in the home directory

Configuration Merge Rules

Configuration is merged per backend section while scanning those files in order.

The first file that contains a c64u section supplies the C64 Ultimate configuration.
The first file that contains a vice section supplies the VICE configuration.
This allows a project-local .c64bridge.json to define c64u while ~/.c64bridge.json defines vice, with both backends available at runtime.

Backend Configuration: C64 Ultimate

Use this for a C64 Ultimate or Ultimate 64:

{
  "c64u": {
    "host": "c64u",
    "port": 80,
    "networkPassword": "secret"
  }
}

If no file is found, the default target is c64u:80 with no network password.
networkPassword is only needed when you enabled a password in the C64 Ultimate network settings.
C64U_HOST, C64U_PORT, and C64U_PASSWORD override the configured host, port, and network password.

Backend Configuration: VICE

C64 Bridge can either connect to an already running VICE Binary Monitor or manage a local VICE process for you. The usual managed setup only needs the emulator binary and, when auto-detection cannot find it, the VICE resource directory:

{
  "vice": {
    "exe": "/usr/bin/x64sc",
    "directory": "/usr/local/share/vice"
  }
}

exe is optional when x64sc or x64 is on PATH. If no explicit binary is configured, the runtime prefers /usr/local/bin/x64sc when present, then falls back to x64sc or x64 on PATH.
directory is optional. When omitted, C64 Bridge auto-detects a VICE resource directory by looking for the standard C64 ROM set near the emulator binary and in common system locations.
host and port are optional and default to 127.0.0.1:6502, the Binary Monitor endpoint C64 Bridge starts for managed local sessions. On local endpoints, C64 Bridge first tries to reuse an already running monitor before starting its own process.
visible, warp, and args are optional runtime controls. They can live in JSON config, but most users set their environment-variable equivalents from the MCP client because they are per-session preferences.
By default, VICE is started lazily on first access. When setting the environment variable VICE_PREWARM=1, C64 Bridge starts or connects VICE in the background during MCP startup.
VICE_BINARY, VICE_DIRECTORY, VICE_HOST, VICE_PORT, VICE_VISIBLE, VICE_WARP, VICE_ARGS, and VICE_PREWARM override the JSON values without editing config files.

VICE Window Modes

Choose the window mode based on where the MCP server runs:

Mode	Configuration	What happens	Use when
Visible	`VICE_VISIBLE=true`	VICE opens a normal desktop window. Warp defaults to off.	You are developing locally and want to watch or interact with the emulator.
Minimized	`VICE_VISIBLE=true`, `VICE_ARGS="-minimized"`	VICE still runs as a normal desktop app, but its window starts iconified. Binary Monitor operations, screen reads, frame capture, and keyboard input continue to work.	You are using an agent locally and do not want the emulator stealing focus, but still want the option to restore the window.
Headless/Xvfb	`VICE_VISIBLE=false`	C64 Bridge launches VICE without a user-facing desktop window, using Xvfb unless disabled. Warp defaults to on.	CI, unattended tests, servers, or any session where no one needs to inspect the emulator window.

Minimized and headless are not the same thing. Minimized is still a visible desktop session with a real VICE window; it is simply hidden by the window manager at startup. Headless/Xvfb has no user-facing window, so it is better for automation but less convenient when you need to debug by looking at the emulator.

For normal local MCP use, prefer minimized VICE. It avoids focus stealing while preserving the ability to restore the window for visual inspection. Prefer headless/Xvfb for CI and remote or display-less environments.

FORCE_XVFB=1 forces the Xvfb path even if a graphical session is available. DISABLE_XVFB=1 disables that fallback and uses the current display, which is mainly useful for troubleshooting display detection.

Recommended VICE Configurations

Local agent session, VICE starts minimized:

{
  "servers": {
    "c64bridge": {
      "command": "npx",
      "args": ["-y", "c64bridge@latest"],
      "env": {
        "C64_MODE": "vice",
        "VICE_VISIBLE": "true",
        "VICE_ARGS": "-minimized",
        "VICE_WARP": "false"
      }
    }
  }
}

Headless automation, VICE runs without a visible desktop window:

{
  "servers": {
    "c64bridge": {
      "command": "npx",
      "args": ["-y", "c64bridge@latest"],
      "env": {
        "C64_MODE": "vice",
        "VICE_VISIBLE": "false",
        "VICE_WARP": "true"
      }
    }
  }
}

If VICE is installed outside the usual search paths, add VICE_BINARY and, if ROM/resource auto-detection fails, VICE_DIRECTORY to either example.

[!NOTE] VICE supports only the operations marked with a VICE checkmark in the MCP API Reference. Unsupported operations return unsupported_platform.

Runtime Backend Switching

When both c64u and vice are configured, C64 Bridge starts with one active backend and keeps the other available for runtime switching.

C64_MODE chooses the initial backend: c64u or vice
c64_select_backend switches backends without restarting the MCP server
c64://platform/status reports the active backend and the full configured backend set
In prompts, say things like use vice, vice: run this program, use c64u, or run this on the real machine
In VS Code, include the backend preference in the same prompt when you want to force emulator versus hardware execution

Prompt illustration (issued via Copilot in VS Code, using GPT 5.4 Medium):

c64u: write a small BASIC program that clears the screen and prints HELLO C64U

vice: write a small BASIC program that clears the screen and prints HELLO VICE

The screenshots below were captured from actual backend bitmap responses after those prompts ran, using the same c64_graphics capture_frame MCP tool on both backends. The C64U implementation captures streamed video frames, while the VICE implementation captures and normalizes the emulator display frame. Both images were then verified optically against the expected text with the C64 character generator, and both matched exactly.

Backend	Screenshot
C64 Ultimate
VICE

VS Code MCP Setup

This section covers the GitHub Copilot integration that ships with VS Code. For the Claude Code VS Code plugin, see Claude Code — it reads .mcp.json, not .vscode/mcp.json.

If this repository is checked out locally, open the prepared .vscode/mcp.json.

Otherwise, put the following into your own .vscode/mcp.json:

{
  "servers": {
    "c64bridge": {
      "command": "npx",
      "args": [
        "-y",
        "c64bridge@latest"
      ]
    }
  }
}

Then click the start button shown above the c64bridge entry.

Your MCP server should now be running:

VS Code Started MCP server

For more details, see the official VS Code MCP Server documentation.

Enable the C64 Agent

After the server is running, switch to the C64 agent in VS Code.

This agent is preconfigured for Commodore 64 work. It steers Copilot toward c64bridge workflows for BASIC, 6502 assembly, SID audio, VIC-II graphics, memory inspection, disk operations, printing, streaming, and device control.

VS Code C64 agent

Optional Overrides

You can add env entries in .vscode/mcp.json to select a config file, override C64 Ultimate connection details, or force an initial backend:

{
  "servers": {
    "c64bridge": {
      "command": "npx",
      "args": [
        "-y",
        "c64bridge@latest"
      ],
      "env": {
        "C64BRIDGE_CONFIG": "/home/you/.c64bridge.json",
        "C64U_HOST": "192.168.1.99",
        "C64U_PORT": "80",
        "C64U_PASSWORD": "secret",
        "C64_MODE": "c64u",
        "LOG_LEVEL": "debug"
      }
    }
  }
}

C64BRIDGE_CONFIG points to a specific config file
C64U_HOST, C64U_PORT, and C64U_PASSWORD override the C64 Ultimate connection without editing config files
C64_MODE forces the initial backend to c64u or vice
LOG_LEVEL=debug enables verbose logging

For VICE-specific overrides such as VICE_ARGS=-minimized, VICE_VISIBLE=false, or custom VICE paths, use the patterns in Backend Configuration: VICE.

Environment Variables in MCP Client Configs

Every runtime environment variable documented in the root mcp.json can be supplied by your MCP client configuration, including .vscode/mcp.json under servers.c64bridge.env.

When an environment variable maps to a JSON config field, the override order is always:

the explicit environment variable from your MCP client config or shell
the merged JSON config section loaded from C64BRIDGE_CONFIG, the repo .c64bridge.json, then ~/.c64bridge.json
the built-in default compiled into the server

When an environment variable has no JSON config equivalent, the order is:

the explicit environment variable from your MCP client config or shell
the built-in default

That rule applies uniformly across the documented runtime environment variables below.

Example: start on minimized VICE with a specific ROM or resource directory, plus a hardware fallback that can still be selected instantly at runtime:

{
  "servers": {
    "c64bridge": {
      "command": "node",
      "args": ["${workspaceFolder}/scripts/start.mjs"],
      "type": "stdio",
      "env": {
        "C64_MODE": "vice",
        "C64U_HOST": "c64u",
        "C64U_PORT": "80",
        "VICE_BINARY": "/usr/local/bin/x64sc",
        "VICE_DIRECTORY": "/usr/local/share/vice",
        "VICE_VISIBLE": "true",
        "VICE_ARGS": "-minimized",
        "VICE_WARP": "false"
      }
    }
  }
}

Example: keep JSON config files for backend endpoints, but override diagnostics, polling, and RAG behavior from VS Code:

{
  "servers": {
    "c64bridge": {
      "command": "node",
      "args": ["${workspaceFolder}/scripts/start.mjs"],
      "type": "stdio",
      "env": {
        "C64BRIDGE_CONFIG": "/home/you/.c64bridge.json",
        "LOG_LEVEL": "debug",
        "C64BRIDGE_POLL_MAX_MS": "8000",
        "C64BRIDGE_POLL_INTERVAL_MS": "200",
        "RAG_BUILD_ON_START": "1",
        "RAG_EMBEDDINGS_DIR": "/home/you/c64bridge-data"
      }
    }
  }
}

Runtime Environment Variable Reference

Every runtime environment variable documented in mcp.json can be set in your MCP client configuration, including .vscode/mcp.json under servers.c64bridge.env.

Server Runtime

Variable	Default	JSON Config Key	Description
`C64_MODE`	c64u	—	Select active backend (c64u for Ultimate hardware, vice for emulator)
`C64_TASK_STATE_FILE`	auto	—	Override the path used to persist MCP background-task state
`C64BRIDGE_CONFIG`	~/.c64bridge.json	config path	Path to configuration JSON
`C64BRIDGE_DIAGNOSTICS_DIR`	~/.c64bridge/diagnostics	—	Override the directory where persistent MCP diagnostics files are written
`C64BRIDGE_DISABLE_DIAGNOSTICS`	0	—	Set to 1 to disable persistent diagnostics logging
`C64BRIDGE_POLL_INTERVAL_MS`	200	—	Interval between screen polls during program-output validation in normal runtime mode
`C64BRIDGE_POLL_MAX_MS`	2000	—	Maximum time to poll for program-output validation before timing out in normal runtime mode
`C64BRIDGE_POLL_STABILIZE_MS`	100	—	Extra settle time after a successful poll match before considering output stable
`LOG_LEVEL`	info	—	Logger verbosity (debug, info, warn, error)

C64 Ultimate

Variable	Default	JSON Config Key	Description
`C64U_HOST`	c64u	c64u.host	Override the C64 Ultimate host name or IP address
`C64U_PASSWORD`		c64u.networkPassword	Override the C64 Ultimate network password sent as X-Password
`C64U_PORT`	80	c64u.port	Override the C64 Ultimate REST port

VICE Runtime

Variable	Default	JSON Config Key	Description
`DISABLE_XVFB`	0	—	Set to 1 to disable Xvfb fallback and use the current display only
`FORCE_XVFB`	0	—	Set to 1 to force managed VICE launches to use Xvfb even when a graphical session is detected
`VICE_ARGS`		vice.args	Extra command-line arguments forwarded to managed VICE launches, such as -minimized for a visible window that starts iconified
`VICE_BINARY`	x64sc	vice.exe	VICE binary to launch for managed emulator sessions and audio capture; automatic search is used only when this override is missing or invalid
`VICE_DIRECTORY`	auto-detect	vice.directory	Override the VICE resource directory used for ROM and UI asset discovery; automatic search is used only when this override is missing or invalid
`VICE_HOST`	127.0.0.1	vice.host	Override the VICE Binary Monitor host
`VICE_PORT`	6502	vice.port	Override the VICE Binary Monitor port
`VICE_PREWARM`	0	vice.prewarm	Set to 1 to start/connect VICE in the background during MCP startup; disabled by default so VICE starts lazily on first use
`VICE_VISIBLE`	true	vice.visible	Launch VICE as a desktop window when true; use headless/Xvfb managed launch when false
`VICE_WARP`	false when visible, true when headless	vice.warp	Enable warp mode for managed VICE sessions
`VICE_XVFB_DISPLAY`	:99	—	Display number to use when managed VICE launches under Xvfb

VICE Audio Capture

Variable	Default	JSON Config Key	Description
`VICE_LIMIT_CYCLES`	120000000	—	Maximum CPU cycles to render when VICE generates audio
`VICE_MODE`	ntsc	—	Default video standard for VICE audio capture (ntsc\|pal)
`VICE_RUN_TIMEOUT_MS`	10000	—	Timeout for headless VICE runs in milliseconds

SID Playback

Variable	Default	JSON Config Key	Description
`SIDPLAY_BINARY`	sidplayfp	—	sidplayfp binary to launch when generating audio
`SIDPLAY_LIMIT_CYCLES`	120000000	—	Maximum CPU cycles to render when sidplayfp generates audio
`SIDPLAY_MODE`	ntsc	—	Default SID playback mode (ntsc\|pal)
`SIDPLAYFP_BINARY`		—	Legacy alias for SIDPLAY_BINARY (sidplayfp executable name)

RAG

Variable	Default	JSON Config Key	Description
`GITHUB_TOKEN`		—	Personal access token used for optional RAG discovery against GitHub
`RAG_BUILD_ON_START`	0	—	Set to 1 to rebuild embeddings on server start
`RAG_DISCOVER_FORCE_REFRESH`	0	—	Set to 1 to ignore cached discovery results when fetching external docs
`RAG_DOC_FILES`		—	Comma-separated extra docs to include in RAG
`RAG_EMBEDDINGS_DIR`	data	—	Directory containing RAG embedding JSON files
`RAG_REINDEX_INTERVAL_MS`	0	—	Periodic reindex interval in ms (0 disables)

Testing

Variable	Default	JSON Config Key	Description
`C64_TEST_TARGET`		—	Overrides integration tests to hit mock or real hardware (mock\|real)

Claude Code

Claude Code is supported as a first-class MCP client. It uses the same canonical start command and the same backend Configuration files and environment variables as every other client — only the discovery file differs.

Claude Code CLI — register the published server in one command:

claude mcp add c64bridge -- npx -y c64bridge@latest

Use --scope user to make it available across all your projects, or --scope project to write a .mcp.json next to the current repo. Backend selection (c64u vs vice), host, port, and password come from the same files documented in Configuration; per-shell overrides come from the variables in Runtime Environment Variable Reference.

Project-scoped discovery — this repository ships a checked-in .mcp.json that points Claude Code at the local source via node scripts/start.mjs. When you open the repo with claude (CLI or VS Code plugin), Claude Code prompts to enable the project-scoped server on first run. Approve it once and the c64_* tools become discoverable in that workspace.

Claude Code VS Code plugin — the plugin reads the same .mcp.json and the same user-scope claude mcp add registrations as the CLI. No extra setup is required beyond installing the plugin and approving the project server prompt. The existing .vscode/mcp.json is read by GitHub Copilot, not by Claude Code; the two files coexist without conflict because they target different clients with different config schemas.

Verify it works — after registration, run claude mcp list (CLI) or open the MCP panel (plugin) and look for c64bridge. Then ask Claude Code something like “use vice: write a small BASIC program that clears the screen and prints HELLO CLAUDE” — it should call c64_select_backend and c64_program directly. If tools do not appear, confirm Node 24+ is on PATH, that the server was approved at the requested scope, and that the backend is reachable per the Configuration section.

Example Workflow

Compose a children’s song with ChatGPT and VS Code:

duck song

Then render PETSCII art for it:

duck petscii

This is representative of the intended workflow:

Ask the MCP client to generate or refine C64-oriented content.
Use grouped tools such as c64_program, c64_graphics, and c64_sound to execute it.
Verify the result via screen reads, frame capture, memory inspection, or audio analysis.

HTTP Invocation

Preferred transport is stdio.
The HTTP bridge is disabled by default and is intended only for manual testing.
The following curl commands are illustrative so you can see what grouped MCP calls look like over HTTP.

# Upload and run BASIC
curl -s -X POST -H 'Content-Type: application/json' \
  -d '{"op":"upload_run_basic","program":"10 PRINT \"HELLO\"\n20 GOTO 10"}' \
  http://localhost:8000/tools/c64_program | jq

# Read current screen (PETSCII→ASCII)
curl -s -X POST -H 'Content-Type: application/json' \
  -d '{"op":"read_screen"}' \
  http://localhost:8000/tools/c64_memory | jq

# Reset the machine
curl -s -X POST -H 'Content-Type: application/json' \
  -d '{"op":"reset"}' \
  http://localhost:8000/tools/c64_system

Build and Test

The ./build script at the project root wraps all development tasks behind a single, self-documented interface:

./build --help                                       # full command reference
./build                                              # install + build + test matrix (full CI run)
./build --skip-tests                                 # install + build only
./build build                                        # TypeScript compile + doc generation
./build test                                         # integration tests (mock backend)
./build test --real                                  # test against real hardware
./build test --platform vice --target mock           # single test leg
./build test:matrix                                  # full matrix (c64u/mock · vice/mock · vice/device)
./build coverage                                     # merged coverage report
./build coverage:single --platform c64u --target mock
./build check                                        # build + test matrix (no install)
./build rag:rebuild                                  # rebuild RAG embeddings
./build release --version 1.2.3                      # prepare a release

Starting the MCP server is not managed by ./build. Use npm start (from source) or npx -y c64bridge@latest (published package) as shown in the Quick Start section above.

Documentation

DeepWiki - architecture and implementation overview
doc/developer.md - development workflow and RAG details
data/context/bootstrap.md - primer injected ahead of prompts
doc/c64u/c64-openapi.yaml - REST surface (OpenAPI 3.1)
AGENTS.md - LLM-facing quick setup, usage, and personas

Static MCP Interface

The repository contains an auto-generated static mirror of the MCP server interface in the ./mcp folder.

This allows agents to inspect the available tools, resources, prompts, and schemas without connecting to the server.

MCP API Reference

This MCP server exposes 17 tools, 27 resources, and 10 prompts for controlling your Commodore 64.

Tools

Address range convention: address + length means start address plus byte count; startAddress + endAddress means inclusive bounds.

c64_batch

Execute multiple c64bridge tool calls in a single request. Reduces latency for multi-step workflows.

No operations defined.

c64_config

Grouped entry point for configuration reads/writes, diagnostics, and snapshots.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`batch_update`	Apply multiple configuration updates in a single request.	—	—	—	✅	✅
`diff`	Compare the current configuration with a snapshot.	`path`	—	—	✅	✅
`get`	Read a configuration category or specific item.	`category`	`item`	—	✅	✅
`info`	Retrieve Ultimate hardware information and status.	—	—	—	✅	✅
`list`	List configuration categories reported by the firmware.	—	—	—	✅	✅
`load_flash`	Load configuration from flash storage.	—	—	—	✅
`read_debugreg`	Read the Ultimate debug register ($D7FF).	—	—	—	✅
`reset_defaults`	Reset firmware configuration to factory defaults.	—	—	—	✅
`restore`	Restore configuration from a snapshot file.	`path`	`applyToFlash=false`	—	✅	✅
`save_flash`	Persist the current configuration to flash storage.	—	—	—	✅
`set`	Write a configuration value in the selected category.	`category`, `item`, `value`	—	—	✅	✅
`shuffle`	Discover PRG/CRT files and run each with optional screen capture.	—	`root="/"`, `extensions=["prg","crt"]`, `durationMs=5000`, `captureScreen=true`, `maxPrograms=10`, `outputPath`, `resetDelayMs=100`	—	✅
`snapshot`	Snapshot configuration to disk for later restore or diff.	`path`	—	—	✅	✅
`version`	Fetch firmware version details.	—	—	—	✅	✅
`write_debugreg`	Write a hex value to the Ultimate debug register ($D7FF).	`value`	—	—	✅

c64_debug

Grouped entry point for VICE debugger operations (breakpoints, registers, stepping).

Operation	Description	Required Inputs	Optional Inputs	Notes	VICE
`continue_execution`	Exit the Binary Monitor and resume CPU execution (BM 0xAA Exit).	—	—	—	✅
`create_checkpoint`	Create a new checkpoint (breakpoint) in VICE.	`address`	`endAddress`, `stopOnHit=true`, `enabled=true`, `temporary=false`, `label`, `operations`, `memspace`	—	✅
`delete_checkpoint`	Remove a checkpoint by id.	`id`	—	—	✅
`get_checkpoint`	Fetch a single checkpoint by id.	`id`	—	—	✅
`get_monitor_state`	Read CPU registers and return the current monitor state.	—	`memspace`	—	✅
`get_registers`	Read register values, optionally filtered by name or id.	—	`memspace`, `registers`	—	✅
`list_checkpoints`	List all active VICE checkpoints (breakpoints).	—	—	—	✅
`list_registers`	List available registers (metadata).	—	`memspace`	—	✅
`nuclear_reset`	Kill and restart the VICE process (managed instances only).	—	—	—	✅
`set_condition`	Attach a conditional expression to a checkpoint.	`id`, `expression`	—	—	✅
`set_registers`	Write register values.	`writes`	`memspace`	—	✅
`step`	Single-step CPU execution.	—	`count=1`, `mode`	—	✅
`step_return`	Continue execution until the current routine returns.	—	—	—	✅
`toggle_checkpoint`	Enable or disable a checkpoint by id.	`id`, `enabled`	—	—	✅
`wait_for_state`	Poll CPU registers until PC equals expectedPC or timeout elapses.	—	`expectedPC`, `timeoutMs=5000`, `pollMs=100`	—	✅

c64_disk

Grouped entry point for disk mounts, listings, image creation, and program discovery.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`create_image`	Create a blank disk image of the specified format.	`format`, `path`	`diskname`, `tracks`	—	✅
`file_info`	Inspect metadata for a file on the Ultimate filesystem.	`path`	—	—	✅
`find_and_run`	Search for a PRG/CRT by name substring and run the first match.	`nameContains`	`root="/"`, `extensions`, `caseInsensitive=true`, `sort="discovered"`, `waitMs=0`, `captureCandidates=10`	—	✅
`list_drives`	List Ultimate drive slots and their mounted images.	—	—	—	✅	✅
`mount`	Mount a disk image with optional verification and retries.	`drive`, `image`	`type`, `attachmentMode`, `driveMode`, `verify=false`, `powerOnIfNeeded=true`, `resetAfterMount=true`, `maxRetries=2`, `retryDelayMs=500`	supports verify	✅	✅
`unmount`	Remove the mounted image from an Ultimate drive slot.	`drive`	—	—	✅	✅

c64_drive

Grouped entry point for drive power, mode, reset, and ROM operations.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`load_rom`	Temporarily load a custom ROM into an Ultimate drive slot.	`drive`, `path`	—	—	✅
`power_off`	Power off a specific Ultimate drive slot.	`drive`	—	—	✅	✅
`power_on`	Power on a specific Ultimate drive slot.	`drive`	—	—	✅	✅
`reset`	Issue an IEC reset for the selected drive slot.	`drive`	—	—	✅	✅
`set_mode`	Set the emulation mode for a drive slot (1541/1571/1581).	`drive`, `mode`	—	—	✅	✅

c64_extract

Grouped entry point for sprite/charset extraction, memory dumps, filesystem stats, and firmware health checks.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U
`charset`	Locate and extract 2KB character sets from RAM.	—	`address`, `scanRange="common"`, `outputPath`, `pauseDuringRead=true`, `minNonEmptyChars=32`, `minEntropy=0.3`	—	✅
`firmware_health`	Run firmware readiness checks and report status metrics.	—	—	—	✅
`fs_stats`	Walk the filesystem and aggregate counts/bytes by extension.	—	`root="/"`, `extensions`, `includeContainers=true`, `maxSamplesPerExtension=3`	—	✅
`memory_dump`	Dump a RAM range to hex or binary files with manifest metadata.	`address`, `length`, `outputPath`	`format="hex"`, `chunkSize=512`, `pauseDuringRead=true`, `retries=1`	—	✅
`sprites`	Scan RAM for sprites and optionally export .spr files.	`address`, `length`	`stride=64`, `maxSprites=16`, `minNonZeroRows=4`, `minSetBits=12`, `includeBase64=true`, `outputDir`, `pauseDuringRead=true`	—	✅

c64_graphics

Grouped entry point for frame capture and graphics rendering workflows.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`capture_frame`	Capture one or more complete video frames from the active backend.	—	`count=1`, `includePixels=true`, `encoding="base64"`	—	✅	✅
`get_display_state`	Read VIC-II and CIA2 registers to determine the current graphics mode and memory layout. Works on C64U and VICE; both backends are read through shared memory primitives so the response shape is identical.	—	—	—	✅	✅
`render_bitmap`	Import an image file, convert it to VIC-II bitmap memory, write it into RAM, and display it.	`imagePath`, `format`	`bitmapAddress=8192`, `screenAddress=1024`, `borderColor=0`, `backgroundColor=0`, `preserveAspect=true`	—	✅	✅
`render_petscii_art`	Create PETSCII art from prompts, text, or explicit bitmap data, and optionally display it on the C64.	—	`prompt`, `text`, `maxWidth`, `maxHeight`, `borderColor`, `backgroundColor`, `foregroundColor`, `dryRun=false`, `bitmap`	—	✅	✅
`render_petscii_text`	Display PETSCII text with optional border and background colours.	`text`	`borderColor`, `backgroundColor`	—	✅	✅
`render_sprite`	Display supplied 63-byte sprite data at the requested position and colour by writing memory and patching VIC-II registers directly.	`sprite`	`index=0`, `x=100`, `y=100`, `color=1`, `multicolour=false`	—	✅	✅

c64_input

Keyboard buffer injection (cross-platform) and joystick simulation (VICE only).

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`joystick`	Simulate joystick input by writing directly to CIA1 Port A/B registers.	`port`, `controls`, `action`	`durationMs=80`	—		✅
`key`	Tap a single key or hold it for a duration.	`key`	`durationMs=0`, `count=1`	—	✅	✅
`write_text`	Send a text string to the keyboard buffer, with PETSCII token expansion.	`text`	`delayMs=0`	—	✅	✅

c64_memory

Grouped entry point for memory I/O, screen reads, and screen polling.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`compare_memory`	Compare two memory regions byte-by-byte and report differences.	`address1`, `address2`, `length`	`maxDiffs=10`	—	✅	✅
`copy_memory`	Copy a RAM region to another address.	`source`, `dest`, `length`	—	—	✅	✅
`disassemble`	Disassemble a memory region into annotated 6502/6510 instructions, including undocumented opcodes with canonical names. Symbol annotations from `.vs` files are applied when available. Works on both C64U and VICE.	`address`	`length=64`, `instructionCount`	—	✅	✅
`fill_memory`	Fill a memory range with a repeating byte pattern.	`address`, `length`, `pattern`	—	—	✅	✅
`read`	Read a range of bytes and return a hex dump with address metadata.	`address`	`length=256`	—	✅	✅
`read_screen`	Return the current 40x25 text screen converted to ASCII.	—	—	—	✅	✅
`save_memory`	Dump a memory range to a local file, with an optional PRG load-address header.	`startAddress`, `endAddress`, `filePath`	`asPrg=true`	—	✅	✅
`search_memory`	Search for a byte pattern within a memory range and return matching addresses.	`startAddress`, `endAddress`, `pattern`	`maxResults=10`	—	✅	✅
`wait_for_text`	Poll the screen until a substring or regex appears, or timeout elapses.	`pattern`	`isRegex=false`, `caseInsensitive=true`, `timeoutMs=3000`, `intervalMs=100`	—	✅	✅
`write`	Write a hexadecimal byte sequence into RAM.	`address`, `bytes`	`verify=false`, `expected`, `mask`, `abortOnMismatch=true`	supports verify	✅	✅

c64_printer

Grouped entry point for Commodore and Epson printing helpers.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U
`define_chars`	Define custom printer characters (Commodore DLL mode).	`firstChar`, `chars`	`secondaryAddress`	—	✅
`print_bitmap`	Print a bitmap row via Commodore (BIM) or Epson ESC/P workflows.	`printer="commodore"`, `columns`	`repeats`, `useSubRepeat`, `secondaryAddress`, `ensureMsb=true`, `mode`, `density`, `timesPerLine`	—	✅
`print_text`	Generate BASIC that prints text to device 4.	`text`	`target="commodore"`, `secondaryAddress`, `formFeed=false`	—	✅

c64_program

Grouped entry point for program upload, execution, and batch workflows.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`batch_run`	Run multiple PRG/CRT programs with post-run assertions.	`programs`	`continueOnError=false`, `durationMs=2000`, `outputPath`, `resetDelayMs=100`	—	✅	✅
`bundle_run`	Capture screen, memory, and debug registers into an artifact bundle.	`runId`, `outputPath`	`captureScreen=true`, `memoryRanges`, `captureDebugReg=true`	—	✅
`cross_platform_greeting`	Show a platform-customized greeting on one or more configured backends, capture screenshots, and verify the results.	—	`platforms=["vice","c64u"]`, `messageTemplate="HAVE A GREAT DAY, {PLATFORM}!"`, `verify=true`, `captureScreenshot=true`, `outputPath`, `restoreActiveBackend=true`, `timeoutMs=1500`, `pollIntervalMs=100`	supports verify	✅	✅
`load_prg`	Load a PRG from Ultimate storage without executing it.	`path`	`symbolsFile`	—	✅
`run_crt`	Mount and run a CRT cartridge image.	`path`	—	—	✅
`run_prg`	Load and execute a PRG from Ultimate-visible storage on c64u or a host-local path on VICE.	`path`	`symbolsFile`	—	✅	✅
`upload_run_asm`	Assemble 6502/6510 source, upload the PRG, and execute it.	`program`	`verify=false`	supports verify	✅	✅
`upload_run_basic`	Upload Commodore BASIC v2 source and execute it immediately.	`program`	`verify=false`	supports verify	✅	✅

c64_rag

Grouped entry point for BASIC and assembly RAG lookups.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`asm`	Retrieve 6502/6510 assembly references from the local knowledge base.	`q`	`k=3`	—	✅	✅
`basic`	Retrieve BASIC references and snippets from the local knowledge base.	`q`	`k=3`	—	✅	✅

c64_select_backend

Switch the active backend between C64U hardware and the VICE emulator at runtime.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`select`	Switch the active runtime backend without restarting the MCP server.	`backend`	—	—	✅	✅

c64_sound

Grouped entry point for SID control, playback, composition, and analysis workflows.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`analyze`	Automatically analyze SID playback when verification is requested.	`request`	`durationSeconds`, `expectedSidwave`	—	✅
`capture_samples`	Capture raw stereo PCM samples from the C64 Ultimate audio UDP stream.	—	`count=256`, `encoding="base64"`	—	✅
`compile_play`	Compile SIDWAVE or CPG source and optionally play it immediately.	—	`sidwave`, `cpg`, `format`, `output="prg"`, `dryRun=false`	—	✅	✅
`generate`	Generate a lightweight SID arpeggio playback sequence.	—	`root="C4"`, `pattern="0,4,7"`, `steps=16`, `tempoMs=120`, `waveform="tri"`, `preset="classic"`	—	✅	✅
`note_off`	Release a SID voice by clearing its gate bit.	`voice`	—	—	✅	✅
`note_on`	Trigger a SID voice with configurable waveform, ADSR, and pitch.	—	`voice=1`, `note`, `frequencyHz`, `system="PAL"`, `waveform="pulse"`, `pulseWidth=2048`, `attack=1`, `decay=1`, `sustain=15`, `release=3`	—	✅	✅
`pipeline`	Compile a SIDWAVE score, play it, and analyze the recording.	—	`sidwave`, `cpg`, `output="prg"`, `waitBeforeCaptureMs=500`, `analysisDurationSeconds=3`, `expectedSidwave`, `verifySilenceBefore=true`, `verifySilenceAfter=true`, `silenceDurationSeconds=1.5`, `silenceRmsThreshold=0.02`, `postSilenceWaitMs=200`, `silenceWaitMs=150`	supports verify	✅
`play_mod_file`	Play a MOD tracker module via the Ultimate SID player.	`path`	—	—	✅
`play_preset`	Compile and play a built-in SID preset such as Für Elise by Beethoven.	—	`preset="fuer_elise"`, `platforms`, `verify=true`, `analysisDurationSeconds=4`, `waitBeforeCaptureMs=400`, `restoreActiveBackend=true`	supports verify	✅	✅
`play_sid_file`	Play a SID file stored on the Ultimate filesystem.	`path`	`songnr`	—	✅
`record_analyze`	Record audio for a fixed duration and return SID analysis metrics.	`durationSeconds`	`expectedSidwave`	—	✅
`reset`	Soft or hard reset of SID registers to clear glitches.	—	`hard=false`	—	✅	✅
`set_volume`	Set the SID master volume register at $D418 (0-15).	`volume`	—	—	✅	✅
`silence_all`	Silence all SID voices with optional audio verification.	—	`verify=false`	supports verify	✅	✅

c64_stream

Grouped entry point for starting and stopping Ultimate streaming sessions.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`start`	Start an Ultimate streaming session toward a host:port target.	`stream`, `target`	—	—	✅
`stop`	Stop an active Ultimate streaming session.	`stream`	—	—	✅

c64_system

Grouped entry point for power, reset, menu, and background task control.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`list_tasks`	List known background tasks with status metadata.	—	—	—	✅	✅
`menu`	Toggle the Ultimate menu button for navigation.	—	—	—	✅
`pause`	Pause the machine until resumed.	—	—	—	✅
`performance_report`	Summarize diagnostics spans and tool latencies from the current or latest MCP session.	—	`scope="current"`, `includeTimeline=true`, `maxEntries=25`	—	✅	✅
`poweroff`	Request a controlled shutdown via the Ultimate firmware.	—	—	—	✅	✅
`reboot`	Trigger a firmware reboot to recover from faults.	—	—	—	✅	✅
`reset`	Issue a soft reset without cutting power.	—	—	—	✅	✅
`resume`	Resume CPU execution after a pause.	—	—	—	✅
`start_task`	Start a named background task that runs on an interval.	`name`, `operation`	`arguments={}`, `intervalMs=1000`, `maxIterations`	—	✅	✅
`stop_all_tasks`	Stop every running background task and persist state.	—	—	—	✅	✅
`stop_task`	Stop a specific background task and clear its timer.	`name`	—	—	✅	✅

c64_vice

Grouped entry point for reading and updating selected VICE resources.

Operation	Description	Required Inputs	Optional Inputs	Notes	C64U	VICE
`resource_get`	Read a VICE configuration resource (safe prefixes only).	`name`	—	—		✅
`resource_set`	Write a VICE configuration resource (safe prefixes only).	`name`, `value`	—	—		✅

Resources

Name	Summary
`c64://guide/index`	Explains how to approach each knowledge bundle and when to consult it.
`c64://guide/bootstrap`	Step-by-step rules for safe automation, verification, and rollback on the C64.
`c64://guide/fast-paths`	Condensed routing guide for one-call demos, backend switching, and when to prefer orchestration over manual tool composition.
`c64://vice/binary-monitor-spec`	Transport framing, single-client constraints, command semantics, and monitor side effects that shape all VICE-backed operations.
`c64://basic/spec`	Token definitions, syntax rules, and device I/O guidance for BASIC v2.
`c64://basic/pitfalls`	Quickref covering quotation handling, line length, tokenization, variable names, and other BASIC traps.
`c64://assembly/6510-spec`	Official opcode matrix, addressing modes, and zero-page strategy for the 6510 CPU.
`c64://sound/sid/spec`	Register map, waveform behaviour, and ADSR envelopes for expressive SID playback.
`c64://sound/sidwave/spec`	Defines the SIDWAVE interchange format used by the SID composer workflow.
`c64://sound/sid/file-format`	Explains PSID/RSID headers, metadata blocks, and compatibility notes for imported music.
`c64://sound/sid/best-practices`	Captures proven waveforms, ADSR presets, phrasing, and verification workflow for pleasant SID music.
`c64://graphics/vic/spec`	Covers raster timing, sprite control, colour RAM, and bitmap modes on the VIC-II.
`c64://graphics/character-set`	Character code table mapping PETSCII codes to screen codes, glyphs, and keyboard input.
`c64://graphics/petscii/style-guide`	Documents colour palette, readability presets, dithering patterns, and best practices for creating artistic and readable PETSCII displays.
`c64://graphics/sprite-charset/best-practices`	Documents sprite and charset workflows, memory layout, VIC-II configuration, common pitfalls, and proven techniques for hardware-accelerated graphics.
`c64://memory/map`	Page-by-page breakdown of the 64 KB address space with hardware, ROM, and RAM regions.
`c64://memory/zero-page-and-workspace`	Documents zero-page variables, BASIC pointers, and KERNAL workspace addresses.
`c64://basic/rom-routines`	Maps BASIC ROM landmarks, reusable interpreter routines, numeric helpers, string helpers, and C64-specific BASIC continuation entries.
`c64://kernal/rom-routines`	Maps KERNAL ROM vectors, jump table entries, internal routines, serial/tape/screen services, and reset handlers.
`c64://io/spec`	Covers VIC-II, SID, CIA, and system control registers with address ranges and usage notes.
`c64://io/cia/spec`	Details CIA 1/2 registers, timers, interrupts, and keyboard matrix layout.
`c64://printer/spec`	Covers device setup, control codes, and Ultimate 64 integration for printers.
`c64://printer/commodore/text`	Character sets, control codes, and formatting for Commodore MPS text output.
`c64://printer/commodore/bitmap`	Details bitmap modes, graphics commands, and data layout for MPS bitmap printing.
`c64://printer/epson/text`	Lists ESC/P control codes and formatting advice for Epson FX text output.
`c64://printer/epson/bitmap`	Explains bit-image modes, density options, and data packing for Epson bitmap jobs.
`c64://printer/prompt-guide`	Reusable prompt templates that drive complex printer jobs through the MCP server.

Prompts

Name	Description
`assembly-program`	Route 6502/6510 routine requests to the canonical assembly skill.
`basic-program`	Route bespoke Commodore BASIC v2 requests to the canonical BASIC skill.
`cross-platform-demo`	Route quick visible demo requests to the cross-platform demo skill.
`drive-manager`	Route disk-image and drive-state requests to the canonical drive skill.
`graphics-demo`	Route graphics requests to the canonical graphics skill.
`hello-world`	Route ultra-fast hello-world and smoke-test requests to the canonical greeting skill.
`memory-debug`	Route reversible memory inspection or patching work to the canonical memory skill.
`preset-music-demo`	Route quick recognizable tune requests to the SID music skill.
`printer-job`	Route printer work to the canonical printer skill.
`sid-music`	Route SID playback and composition work to the canonical SID skill.

Keywords

mcp

mcp-server

model-context-protocol

c64

commodore-64

commodore-64-ultimate

FAQs

What is c64bridge?

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Package last updated on 12 Jul 2026

c64bridge

C64 Bridge

Contents

Overview

Features

Quick Start

1. Install Node.js 24+ and npm

2. Start the Server

3. Add Backend Configuration

4. Connect from an MCP Client

Configuration

Configuration File Order

Configuration Merge Rules

Backend Configuration: C64 Ultimate

Backend Configuration: VICE

VICE Window Modes

Recommended VICE Configurations

Runtime Backend Switching

VS Code MCP Setup

Enable the C64 Agent

Optional Overrides

Environment Variables in MCP Client Configs

Runtime Environment Variable Reference

Server Runtime

C64 Ultimate

VICE Runtime

VICE Audio Capture

SID Playback

RAG

Testing

Claude Code

Example Workflow

HTTP Invocation

Build and Test

Documentation

Static MCP Interface

MCP API Reference

Tools

c64_batch

c64_config

c64_debug

c64_disk

c64_drive

c64_extract

c64_graphics

c64_input

c64_memory

c64_printer

c64_program

c64_rag

c64_select_backend

c64_sound

c64_stream

c64_system

c64_vice

Resources

Prompts

Keywords

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