Early development ยท Open source, MIT
Inspired by Rider: an editor of its own over Roslyn, a debugger and a profiler of its own, unit tests, Git, NuGet and a terminal. And an MCP server, so your agent works in the same IDE you do.
For Windows and macOS, with builds for Linux.
Everything in Passenger is .NET, from the window to the debugger, built on the libraries a C# IDE needs: Roslyn, MSBuild, ICorDebug, EventPipe and VSTest.
A text control of its own over an immutable rope: multiple carets, code folding, Extend Selection, live and postfix templates, and Rider's Visual Studio keymaps with their chords. It keeps up with every keystroke in a 50,000-line file.
Colours, diagnostics, completion, hovers and signature help, quick fixes and refactorings, rename, Go to Declaration and Implementation, Find Usages, call and type hierarchies, and decompiled library sources.
A Solution view of your projects, builds with their errors in Problems, run configurations from your launch
profiles, and Hot Reload under dotnet watch.
xUnit, NUnit and MSTest found and run through VSTest, run marks in the gutter, results by project, class and method, failures rerun, and any test debugged.
Search nuget.org, then install, update and remove packages for each project, with central package management.
A terminal emulator of its own with a shell per tab, where vim, less and htop run full-screen.
Over the runtime's ICorDebug: breakpoints with conditions, hit counts and log messages, stepping through async code, Run to Cursor and Set Next Statement, the call stack and threads, variables you can open and set, watches and evaluation, and the values each line used drawn after it.
Sampling over EventPipe, from a program's first instruction: its call tree, hot spots, flame graph, allocations and garbage collections, narrowed to any stretch of the timeline. A memory snapshot counts a running program's heap by type.
The Commit window with its changes, the log with its branch graph, side-by-side diffs, blame, change bars in the gutter that roll a change back, branches, stashes, push, pull and fetch.
Search Everywhere, Go to File, Go to Symbol and Find Action, Find and Replace in Files with a preview, Recent Files, bookmarks and File Structure.
Passenger is a Model Context Protocol server. A coding agent can ask Roslyn about your code and use its fixes and renames, build and run, run tests, debug (breakpoints, stepping, evaluation, the stopped program's variables), use Git and NuGet, type into the terminal, and see the window in screenshots.
Attach it to the window you have open, and its breakpoints and stops show there as you watch. A window listens on a socket only you can reach.
# a Passenger of the agent's own, with no window claude mcp add passenger -- \ /path/to/Passenger --mcp /path/to/solution # the Passenger window you have open claude mcp add passenger -- \ /path/to/Passenger --mcp-attach
Those are Claude Code's commands; any MCP client works the same way.
Passenger