←All projects

Developer Tools/Case StudyShipped/ 2026

Forge Dev Tools

AI pair-programmer for legacy codebases.

DevToolsLLMAST
/forge-devtools
forge dev tools / onlineDevTools · LLM · AST

Problem and solution

01/Problem

AI pair-programmers lose their minds in unfamiliar codebases. They hallucinate APIs, miss patterns, and ignore the conventions the team actually uses.

02/Solution

Forge indexes the repo into a typed symbol graph, then serves precise, scoped context per request. The model only sees what it needs to see — and always grounded in real files.

03/How it works

The system, end to end.

  1. 01next →

    Index

    Build a typed symbol graph of the repo.

  2. 02next →

    Locate

    Locate candidate symbols per request.

  3. 03next →

    Score

    Rank by recency, similarity, and use.

  4. 04next →

    Compose

    Build a tight, grounded context window.

  5. 05loop

    Respond

    Model reasons against actual files.

04/Architecture

Components and data flow.

How the moving parts fit together. Solid arrows are synchronous calls; dashed arrows are queued or batched.

  1. 01

    Editor / CLI

  2. 02

    Indexer (TS / Python / Go)

  3. 03

    Symbol graph store

  4. 04

    Retriever

  5. 05

    Context composer

  6. 06

    Model adapter

  7. 07

    Local model fallback

↓ flow continues

05/Technology

The stack.

AI / ML
GPT-class modelsLocal GGUF fallbackCodeT5+ embeddings
Frontend
VS Code extensionCLI
Backend
RustNode.js
Database
SQLiteLanceDB
Infrastructure
Local-firstDocker
APIs
OpenAIAnthropicOllama

06/Engineering decisions

What we picked, and why.

  1. 01

    Symbol graph instead of chunked text

    Choice

    AST + references, not raw file slices

    Alternatives

    • Sliding window chunks
    • Vector-only retrieval

    Why

    Chunked retrieval pulled in stale or wrong-version code. The symbol graph made references exact.

  2. 02

    Local model fallback

    Choice

    Route simple requests to a local GGUF model

    Alternatives

    • All requests to hosted models

    Why

    Cut cost on routine edits and kept private repos fully on-prem when needed.

07/Evaluation

What we measured.

  • 01

    61%

    Acceptance rate

  • 02

    0.9s

    Latency p50

  • 03

    34%

    Local fallback share

08/Challenges

What almost broke us.

  • 01

    Multi-language repos

    What happened

    Different AST strategies per language.

    What we did

    Pluggable indexer adapters with a shared symbol schema.

09/Results

Used daily by ~40 engineers. Reduced 'wrong API' rejections by 38% in the first month.

10/Future improvements

  • ›Incremental indexing
  • ›Test-aware suggestions

Have an interesting AI problem?

Let's build something.

If you're working on something that needs real AI engineering — not just a demo — let's talk.

© 2026
Motion-Y

Hello, I'm your Motion-Y Assistant. How can I help you today?