debugium
Provides debugging capabilities for C++ programs via lldb-dap adapter.
Provides debugging capabilities for JavaScript programs (via Node.js/TypeScript adapter).
Provides debugging capabilities for Node.js programs via js-debug adapter.
Provides debugging capabilities for Python programs, including breakpoints, stepping, variable inspection, and more.
Provides debugging capabilities for Rust programs via lldb-dap adapter.
Provides debugging capabilities for Scala programs via Metals DAP server.
Provides debugging capabilities for TypeScript programs (via Node.js/TypeScript adapter).
Provides debugging capabilities for WebAssembly programs via lldb-dap adapter.
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@debugiumdebug my Python script script.py with breakpoint at line 5"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
Debugium
A multi-language debugger with a real-time web UI and LLM integration via MCP.
Debug Python, JavaScript, TypeScript, C, C++, Rust, Java, Scala, and WebAssembly programs from your browser — with AI-driven analysis through the Model Context Protocol.

Features
Web UI
Real-time web UI — source viewer, breakpoints, variables (recursive expansion), call stack, console, timeline, watch expressions, findings — all updated live via WebSocket
Multi-tab source viewer — open multiple files, click stack frames to navigate
Variable search — filter variables by name with recursive expansion
Changed-variable highlighting — variables that changed since last stop shown in orange
Thread selector — switch between threads in multi-threaded programs
Panel collapse & resize — drag to resize, toggle to collapse; Slim / Standard / Full layout presets
Dark / light mode toggle
Auto-reconnect — UI reconnects after a dropped WebSocket, with visual status indicator
Keyboard shortcuts — F5 continue, F10 step over, F11 step in, Shift+F11 step out, Ctrl/Cmd+D dark mode
Button animations — in-flight spinner and completion flash for debug commands
Debugging
Multi-language — Python (debugpy), Node.js/TypeScript (js-debug), C/C++/Rust (lldb-dap), Java (java-debug), Scala (Metals), WebAssembly (lldb-dap), or any DAP adapter via
dap.jsonComprehensive DAP coverage — 35+ DAP requests: breakpoints, stepping, goto, memory read/write, disassembly, and more
Breakpoints — conditional, logpoints, hit-count, function, data (watchpoints), exception, run-to-cursor (
continue_until)Multi-session — debug multiple programs simultaneously, with child session routing (js-debug)
Remote debugging — attach to debugpy, JDWP, or Node inspector running on another machine or container
LLM / MCP Integration
64 MCP tools — the full debug session exposed to Claude or any LLM
Capability-gated tools — tools automatically shown/hidden based on adapter capabilities
Compound tools —
get_debug_context(orient in one call),step_until,step_until_change,run_until_exception,explain_exception,get_call_tree,compare_snapshots,find_first_changeExecution timeline — every stop recorded with changed variables and stack summary
Watch expressions — evaluated automatically at every breakpoint, manageable by LLM or UI
Annotations & findings — pin notes to source lines, record conclusions visible in the UI
Session export/import — save and restore debugging knowledge across sessions
CLI Control
Full CLI — 13 subcommands to drive sessions from a second terminal without the web UI
Auto-discovery — port file at
~/.debugium/port, session logs in~/.debugium/sessions/
Install
Claude Code Plugin (recommended)
/plugin marketplace add Algiras/debugium
/plugin install debugium@debugiumThen add to your project's .mcp.json (see MCP Tools below).
macOS / Linux binary
curl -fsSL https://raw.githubusercontent.com/Algiras/debugium/main/install.sh | bashFrom source
# Prerequisites: Rust stable + wasm-pack
cargo install wasm-pack
# Build UI
wasm-pack build crates/debugium-ui --target web --out-dir pkg
cp crates/debugium-ui/pkg/cm_init.js crates/debugium-ui/dist/pkg/
cp crates/debugium-ui/pkg/debugium_ui.js crates/debugium-ui/dist/pkg/
cp crates/debugium-ui/pkg/debugium_ui_bg.wasm crates/debugium-ui/dist/pkg/
# Build & install server
cargo install --path crates/debugium-serverUsage
Debug a Python file
debugium launch my_script.py --adapter pythonDebug a Node.js / TypeScript file
debugium launch app.js --adapter node
debugium launch app.ts --adapter typescriptDebug C / C++ / Rust
# C or C++ (compile with -g for debug info)
cc -g -O0 main.c -o main && debugium launch ./main --adapter lldb
c++ -g -O0 main.cpp -o main && debugium launch ./main --adapter lldb
# Rust
cargo build && debugium launch target/debug/my_binary --adapter lldbDebug Java / Scala
# Java (requires microsoft/java-debug adapter)
debugium launch MainClass --adapter java
# Scala (connect to a running Metals DAP server)
debugium launch build-target --adapter metals
debugium launch build-target --adapter metals:5005 # custom portAttach to a running process (remote debugging)
# Python (debugpy listening on port 5678)
debugium attach --port 5678 --adapter python
# Java (JDWP on port 5005)
debugium attach --port 5005 --adapter java
# Node.js (inspector on port 9229)
debugium attach --port 9229 --adapter nodeOr via MCP: attach_session(port=5678, adapter="python", breakpoints=["/path/app.py:42"])
Use a custom adapter via dap.json
# Create a dap.json (see dap.json.example) then:
debugium launch my_program --config ./dap.json
# Or place dap.json in cwd / .debugium/ for auto-discovery:
debugium launch my_program # finds ./dap.json automaticallySet initial breakpoints
debugium launch my_script.py --adapter python \
--breakpoint /abs/path/my_script.py:42 \
--breakpoint /abs/path/helpers.py:15Enable LLM / MCP integration
Add a .mcp.json to your project root (Claude Code picks this up automatically):
{
"mcpServers": {
"debugium": {
"command": "debugium",
"args": ["mcp"]
}
}
}Then launch the session normally — the MCP server connects to whichever port is active:
debugium launch my_script.py --adapter python --breakpoint /abs/path/my_script.py:42Claude Code will now have access to all Debugium MCP tools. See CLAUDE.md for the recommended workflow and SKILL.md for the full tool reference.
CLI Control Commands
Once a session is running (debugium launch …), you can drive it from a second terminal — or from an LLM agent — without touching the web UI.
Port is auto-discovered from ~/.debugium/port; override with --port.
Global flags (all subcommands)
Flag | Default | Description |
|
| Server port to connect to |
|
| Session to target |
| off | Print raw JSON instead of human-readable output |
Inspection
debugium sessions # list active sessions
debugium threads # list threads
debugium stack # show call stack
debugium vars # show local variables (auto-resolves top frame)
debugium vars --frame-id 2 # show variables for a specific frame
debugium eval "len(fibs)" # evaluate expression in top frame
debugium eval "x + 1" --frame-id 2
debugium source path/to/file.py # print full source file
debugium source path/to/file.py --line 43 # windowed ±10 lines with → marker
debugium context # full snapshot: paused-at, stack, locals, source, breakpoints
debugium context --compact # same but truncated (3 frames, 10 vars)Breakpoints
debugium bp set FILE:LINE [FILE:LINE …] # set breakpoints (replaces existing in that file)
debugium bp list # list all breakpoints
debugium bp clear # clear all breakpointsExecution control
debugium continue # resume execution
debugium step over # step over (next line)
debugium step in # step into a function call
debugium step out # step out of current functionUI annotations (visible in the web UI)
debugium annotate FILE:LINE "message" [--color info|warning|error]
debugium finding "message" [--level info|warning|error]Example workflow
# Terminal A — start the session
debugium launch tests/target_python.py --adapter python \
--breakpoint "$(pwd)/tests/target_python.py:43"
# Terminal B (or LLM agent) — inspect and drive it
debugium sessions
debugium stack
debugium vars
debugium eval "len(fibs)"
debugium bp set tests/target_python.py:49
debugium continue # runs to line 49
debugium vars
debugium step over
debugium context --json # machine-readable snapshot
debugium annotate tests/target_python.py:43 "called here" --color info
debugium finding "fibs has 10 elements" --level info
debugium bp clearMCP Tools
When connected via MCP, 64 tools are available. Key ones:
Category | Tools |
Orient |
|
Breakpoints |
|
Execution |
|
Inspection |
|
Mutation |
|
Output |
|
Memory |
|
History |
|
Annotations |
|
Watches |
|
Compound |
|
Session |
|
Control |
|
Note:
step_over,step_in, andstep_outare blocking — they wait for the adapter to pause before returning. Safe to chain back-to-back without sleeps.continue_executionreturnsconsole_line_countfor use withwait_for_output. Tools likeread_memory,goto, andrestart_frameonly appear when the adapter supports them.
See SKILL.md for the full reference with input schemas.
Keyboard Shortcuts
Key | Action |
| Continue |
| Step Over |
| Step Into |
| Step Out |
| Toggle dark/light mode |
Architecture
debugium-server (Rust + Axum)
├── DAP proxy — spawns / attaches to debug adapters (debugpy, js-debug, lldb-dap, java-debug, Metals, custom)
├── HTTP API — /state, /sessions, /annotations, /findings, /watches, /timeline
├── WebSocket — broadcasts DAP events + enriched stop data (changed vars, timeline) to UI
├── MCP stdio — JSON-RPC 2.0 server exposing 64 tools for LLM integration
├── CLI control — 13 subcommands to drive sessions from a second terminal
└── ~/.debugium/ — port file, session logs (events.ndjson), debug log
debugium-ui (Leptos + WASM)
├── CodeMirror 6 — source viewer with breakpoint gutters, exec arrow, LLM annotations, multi-tab
├── Reactive panels — Variables, Stack, Breakpoints, Findings, Watch, Timeline, Console (18 components)
└── WebSocket — receives events, sends DAP commands, auto-reconnects with status indicatorSupported Languages & Adapters
Language |
| Prerequisite | Verified |
Python |
|
| ✅ |
Node.js |
| js-debug (bundled or build from vscode-js-debug) | ✅ |
TypeScript |
| js-debug + | ✅ |
C / C++ |
|
| ✅ |
Rust |
|
| ✅ |
Java |
| microsoft/java-debug adapter JAR | ✅ |
Scala |
| Running Metals DAP server | ⚠️ (requires running Metals) |
WebAssembly |
|
| ⚠️ (requires WASM-aware LLVM) |
Any DAP adapter |
| See | ✅ |
Remote debugging
Connect to a DAP server running on another machine (or in a container):
{
"adapterId": "debugpy",
"request": "attach",
"host": "192.168.1.100",
"port": 5678,
"pathMappings": [{ "localRoot": ".", "remoteRoot": "/app" }]
}debugium launch app.py --config remote.jsonLicense
MIT
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