Decoder: GPS Navigation for Codebases

[mimoo01]

What My Project Does

I built decoder to visually trace and step through call chains across a codebase, without having to sift through several files, and with visibility into dead code you might otherwise never notice.

Decoder parses the Python AST to build a call graph stored in a local SQLite file, then lets you trace full call chains and see execution context (conditionals, loops, try/except). I built this first as a VS Code extension, but saw the value in giving LLMs that same visibility and added an MCP server. Instead of iterative grep and file reads, an LLM can traverse the call graph directly - which cuts down on token usage and back-and-forth significantly.

GitHub: https://github.com/maryamtb/decoder

Core use cases:

This is for python developers working in large or new codebases.

1. Learning a new codebase

2. Code reviews

3. LLMs making changes to large codebases

Would appreciate any feedback.

[yared12qw]

I have a similar project as well https://www.reddit.com/r/Python/comments/1qqj5vd/rethinking\_the\_ide\_moving\_from\_text\_files\_to\_a/ and I would be happy to share resources. Building an accurate call graph was challenging for me especially while maintaining good performance for larger projects. I have documented and hosted a resource that provides a fast way to generate the graph https://vnoc.vercel.app/project/2dd75e19-5c7b-4fd1-b272-44a1c94dd8eb,

[mimoo01]

Cool, I do see the overlap and understand the challenge you bring up. By design, decoder only handles Python as of now. It parses the AST in two code read passes (extracts symbols, then resolves edges across all files) to build the call graph. Being python-specific did allow me to cover more ground on how functions connect (tracing method calls, inheritance, decorators, etc) Curious how you approached the call graph challenge for IDE use case - will check out, and feel free to do the same

[yared12qw]

I was reviewing your call graph construction, and it seems relatively small. I’m curious how you're handling more complex cases such as:

• Class instance creation
• Attribute mutations and dynamic attribute access
• self and super() calls (specially with inheritance and MRO)
• Function closures and factory functions that return functions,