React 19 Migration Agent — Backend

Async pipeline that migrates React codebases to React 19 using AST-based static analysis, RAG-augmented documentation retrieval, and LLM-powered code rewriting.

react.migration.latest.1.1.mov

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How It Works

Upload .tsx files
      │
      ▼
AST audit (Tree-sitter) → detect React 19 violations
      │
      ▼
RAG retrieval (ChromaDB + HuggingFace) → fetch relevant React 19 docs
      │
      ▼
LLM rewrite (Groq) → fix code using rules + docs context
      │
      ▼
Migrated files stored in S3 → download via API

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Tech Stack

Layer	Technology
API	FastAPI (Python 3.12, uv)
AST Analysis	Tree-sitter
LLM	Groq (openai/gpt-oss-120b)
Embeddings	HuggingFace (all-mpnet-base-v2)
Vector Store	ChromaDB
Storage	AWS S3 (LocalStack locally)
Infrastructure	Terraform

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Project Structure

├── api/
│   ├── main.py              # FastAPI app
│   └── routes/              # upload, migrate, status, results, download
├── auditor.py               # Tree-sitter AST scanner
├── migration.py             # Pipeline + RAG retrieval
├── job_store.py             # Async job tracking
├── s3_client.py             # S3 client
├── ingest.py                # One-time ingestion script
├── terraform/               # Infrastructure as code
├── data/                    # Scraped React 19 docs (auto-generated)
├── chroma_db/               # ChromaDB (auto-generated)
└── migration_rules.yaml     # 14 React 19 migration rules

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Getting Started

Prerequisites (macOS)

brew install uv localstack pipx hashicorp/tap/terraform
pipx install awscli-local

Quick Start (Docker)

# copy and configure environment
cp .env.example .env
# add your GROQ_API_KEY

# start everything
docker-compose up --build

API at http://localhost:8000 — docs at http://localhost:8000/docs.

Manual Setup

# 1. install dependencies
uv sync

# 2. configure environment
cp .env.example .env
# add your GROQ_API_KEY

# 3. start localstack
localstack start

# 4. provision s3 buckets
cd terraform && terraform init && terraform apply

# 5. ingest react 18 to 19 upgrade guid (one time only)
python ingest.py

# 6. start api
uvicorn api.main:app --reload

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API

Method	Endpoint	Description
POST	/upload	Upload .tsx files, returns job_id
POST	/migrate/{job_id}	Trigger async migration pipeline
GET	/status/{job_id}	Poll progress
GET	/results/{job_id}	Full results when complete
GET	/download/{job_id}/{filename}	Download migrated file

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Migration Rules

14 rules covering refs, ReactDOM APIs, PropTypes, context, and TypeScript patterns. See migration_rules.yaml for the full list.

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RAG Pipeline

React 19 documentation is scraped from react.dev, chunked, embedded with HuggingFace (all-mpnet-base-v2), and stored in ChromaDB.

At migration time, relevant documentation chunks are retrieved using semantic search and injected into the LLM prompt alongside the migration rules — giving the LLM richer context for accurate rewrites.

To refresh the documentation:

python ingest.py

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LocalStack Persistence

Add to ~/.zshrc to persist data between restarts:

export LOCALSTACK_VOLUME_DIR=~/.localstack/volume

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Production Deployment

cd terraform
terraform apply -var-file="terraform.prod.tfvars"

Set real AWS credentials via environment variables — never in files.

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Related

• Frontend: react_migration_rag_frontend