Dart hosts the runtime

Tools, event streams, workspaces and child execution in your application.

Loading worker…

Observed output

Events, files and structured errors


Runtime API
final runtime = await MontyRuntime.start(pool: pool, os: files.call,
  externalModules: {'tools': tools});
final value = await runtime.execute('import tools\ntools.add(2, 3)').result;
await runtime.dispose();
await pool.close();
Runtime code lives in lib/src/runtime/, bridge/, extensions/, host/ and os_call/. Core owns the engine, process pool and worker assets.


Engine examples and compatibility → dart_monty_core


Quick Start


One-shot execution
final pool = await Monty.start();
try {
  final result = await pool.withSession((session) => session.feedRun('2 + 2'));
  print(result.dartValue);
} finally { await pool.close(); }


Stateful runtime with extensions
final runtime = await MontyRuntime.start(
  pool: pool, os: OSAccess().call, extensions: [SandboxExtension()]);
await runtime.execute('x = 42').result;
print((await runtime.execute('x + 1').result).dartValue);
await runtime.dispose();


Persistent Python sessions


MontySession supplies feedRun and feedStart/resume. MontyRuntime adds host dispatch, extensions and bridge events. Variables and functions survive across executions. The REPL keeps memory files until Reset.


Interactive REPL · Lifecycle and concurrency


Extensions and filesystems


SandboxExtension supplies sandbox_spawn, sandbox_await, sandbox_gather and sandbox_free. Children have explicit filesystem and external-module grants.


OSAccess supports writable memory files, read-only host mounts and copy-on-write overlays. Host functions register typed schemas and handlers.


Workspace ownership · Extension guide · Filesystem policy


Architecture


dart_monty: lib/src/runtime/, bridge/, extensions/, host/, os_call/
dart_monty_core: engine sessions, worker processes and WASM assets


Native applications communicate with core's worker process. Web applications use js_interop and a Web Worker. MontyRuntime dispatches host callbacks and publishes BridgeEvents as execution suspends and resumes.


Architecture overview




  

    
Interactive Demos

    

      All demos run in your browser via WebAssembly. No server required.
    


    

      
        
REPL

        
Interactive Python REPL with persistent session state.

      
      
        
Basic Execution

        
One-shot Python execution, error handling, external functions.

      
      
        
Async/Sync Matrix

        
Six-cell walkthrough of the (Dart × Python) async matrix, including useFutures: true.

      
      
        
Virtual Filesystem

        
Python pathlib operations against in-memory VFS.

      
      
        
Agent Session

        
Stateful agent with plugins, telemetry, and event streaming.

      
      
        
Python Ladder

        
Measured fixture compatibility with explicit outcome classifications.

      
      
        
Sorting Visualizer

        
Step-by-step sorting algorithm animations in Python.

      
    

  







  

    
Get Started


    
Install


dart pub add dart_monty --git-url https://github.com/runyaga/dart_monty.git \
  --git-ref vX.Y.Z-dev.N


    
Native

    
Python runs in dart_monty_core's worker process, found
       by core's discovery or passed to Monty.start as
       workerLocation.


    
Web

    
Python runs in a Web Worker built from core's
       dart_monty_core_worker.js and
       dart_monty_core_worker.wasm. Flutter web builds ship
       them as core's package assets; plain-Dart-web consumers copy them
       from core's lib/assets/ to
       web/packages/dart_monty_core/assets/, or anywhere else
       named by workerLocation:


cp dart_monty_core/lib/assets/dart_monty_core_worker.js web/
cp dart_monty_core/lib/assets/dart_monty_core_worker.wasm web/


    
Documentation