AI Coding Assistant for VS Code

The problem

An in-editor agent has to do two things that pull against each other: act with enough autonomy to be faster than doing the work yourself, and never make a change you cannot see or undo. Get the balance wrong in one direction and it is a novelty; wrong in the other and it is a liability.

What I built

I worked across the stack on the memory and conversational-memory systems, the skills and commands frameworks, the expanded tooling layer, multi-model support, and the upgrade from a single agent to a multi-agent model with sub-agents.

The extension owns the hands, the backend owns the reasoning

A deliberate split. Tool execution, file access, diff application and local indexing live in the editor, where they belong — they need filesystem access and they must be fast. The agent loop, tool selection and multi-turn control live server-side. The extension holds no model credentials and runs no prompt loop.

That boundary is also what makes multi-model support tractable: the client asks which models are available rather than knowing anything about providers.

Reviewable changes, not applied changes

Edits surface as a vertical diff with per-hunk accept and reject. The mechanism that makes this reliable is revert-then-replay: rather than tracking incremental state as a user accepts and rejects hunks, the file returns to its original content and the accepted hunks are re-applied. Incremental application accumulates drift; replay from a known state cannot.

Ordering preserved across an async stream

Text, reasoning and tool-call blocks arrive interleaved over the stream and are stamped with a sequence number, then merged into a single timeline for rendering. Without that, a slow tool result renders after text that logically preceded it and the transcript reads as nonsense.

Autonomy as a ladder, not a switch

Approval runs through tiers: always-ask for anything at the tool limit, an allowlist for low-risk reads, then project-level and session-level rules. A user can grant standing permission for the safe things without granting it for everything.

Honest limitations

The extension has no automated test suite, and its CI runs security scanning only — no lint, no typecheck, no tests. Around a thousand lines of built-but-unwired features sit in the tree. Both are the predictable cost of shipping fast against a moving product, and both are the first things I would fix.