Codecell: Python JS TS Tracer

Codecell is a code editor that shows you what your program actually did.

Write Python, JavaScript or TypeScript in one library. The language belongs to the script, not to the app, so a Python file and a TypeScript file sit side by side and each runs on the engine that suits it.

STEP THROUGH YOUR CODE

Run a program and scrub back through it line by line. At every step you see which line is executing, the call depth, and what each variable held at that moment. The editor highlights the line you are looking at. It is the difference between guessing why a loop is wrong and watching it go wrong.

A LIVE SESSION PER LANGUAGE

The REPL keeps its namespace between entries, so a value you define stays defined. Each language gets its own session, and tracing a program never disturbs it.

EVERYTHING RUNS ON YOUR PHONE

Real CPython 3.13 is embedded in the app. JavaScript and TypeScript run in the device's own engine, and TypeScript is compiled by the real tsc, bundled in the app, with the standard library alongside it. No account, no sign-in, no server, and it all works with the network switched off.

AN ASSISTANT THAT ACTUALLY RUNS THINGS

On supported devices, the built-in assistant answers questions about your code using the on-device model. It is not a chat box guessing at output: it can run your program and trace it with the same engines the editor uses, then show you what it found. Nothing you write is sent anywhere, and a suggested change is never applied until you tap Apply.

ALSO INSIDE

- Syntax highlighting, auto-indent and a key bar built for code

- Abstract and concrete syntax trees

- Capture code from a photo

- Share a snippet as an image

- Open a source file from anywhere on your device

The assistant requires a device with on-device AI support and is hidden, with a reason, everywhere else. Everything else works on any phone running Android 7 or later.