JavaChat

JavaChat is a web application and command-line research assistant for software developers. It searches a version-aware library of technical documentation before generating an answer. Use it to learn an unfamiliar API, compare documented behavior across releases, or find the commands, configuration, and migration details needed to move development work forward. Answers can include links to the retrieved pages, and JavaChat is designed to make missing source coverage visible.

Use JavaChat in whichever form fits your workflow:

• Web: open javachat.ai for chat and guided lessons.
• Terminal: install the JavaChat CLI to research from any directory and receive source links when retrieval finds supporting documentation.
• Self-hosted development: run the Svelte and Spring Boot application locally and connect it to Qdrant and an OpenAI-compatible gateway.

What JavaChat helps you do

• Learn APIs and platforms: request a focused explanation, short example, applicable version, and source pages you can inspect.
• Research technical decisions: investigate releases, migration paths, commands, configuration rules, prerequisites, and operational caveats.
• Move real work forward: keep the CLI beside your code while implementing an integration, debugging a library, planning an upgrade, or configuring a deployment.
• See the source boundary: JavaChat can retrieve the exact requested release or nearby releases of the same technology when they are indexed, and can report when the requested evidence is absent.

Example queries possible with JavaChat

• “What does Thread.ofVirtual() return in Java 25, and what is the shortest documented example?”
• “When should I use MULTISET instead of a flat join in jOOQ 3.21.7?”
• “How do I add a 30-second delay between tasks in a Docker Swarm rolling update?”
• “What defaults can I configure with Spring AI 1.1.2 ChatClient.Builder?”
• “How does a Clerk session token differ from a backend Secret Key?”

Representative coverage in the shared JavaChat knowledge index includes:

• Languages: Java SE 21, 25, and 26; Kotlin 2.4.10; Groovy 5.0.7; Scala 3; and Python 3.14.7.
• Libraries: Spring Framework 7.0.7; Spring AI 1.1.x; four indexed Jackson 2.x/3.x releases; jOOQ 3.21.7; HikariCP 7.x; and Lombok 1.18.46.
• Platforms: PostgreSQL 17/18, Docker, Cloudflare, Clerk, Dokploy, Traefik, Doppler, and Infisical.
• Repository snapshots: OpenAI Java, Anthropic SDKs, Langfuse, Dokploy, Infisical, and Traefik.

Run javachat list all for the complete current inventory. Chat retrieves supporting material from the documentation collections.

Install the CLI

The CLI supports macOS and Linux and requires Node.js 24.18 or newer.

npm install --global @wcallahan/javachat-cli
javachat auth login
javachat ask "How do Java records work?"

Upgrade an npm-installed copy with javachat update. The command updates the project-local package that owns the invoked binary, or the active global npm installation.

Use javachat list all to see the documentation packages, source repositories, versions, and revisions available on the selected deployment. See the CLI README for all commands, non-interactive authentication, local development, and package verification.

How it works

1. JavaChat searches the documentation index for material relevant to the question and requested version.
2. The strongest matches are supplied as context for the answer.
3. The answer streams to the web app or CLI, with source links when retrieval returns citations. When matching source documents are absent, JavaChat still answers from the model's general knowledge and labels that limitation in the answer.
4. Guided lessons keep their own conversations, while ordinary chat can continue a prior session.

The repository also contains the pipeline that fetches, chunks, embeds, deduplicates, and indexes the source material. See Architecture for Qdrant, dense and sparse search, reciprocal-rank fusion, and streaming details.

Run the application locally

Prerequisites

• BellSoft Liberica JDK 25
• Node.js 24.18
• Docker, when running the local Qdrant service
• mise or another Java version manager for the pinned development toolchain

Install the pinned Java version:

mise install

Install and select the frontend's pinned Node.js version with nvm:

nvm install 24.18.0
nvm use 24.18.0

Then configure and start the full application:

cp .env.example .env
# Set OPENAI_BASE_URL and OPENAI_API_KEY in .env.
make compose-up
make dev

Open http://localhost:8085. The local commands create missing Qdrant schemas only for loopback connections; remote Qdrant deployments remain fail-closed.

For a fuller explanation of the environment variables, local collection setup, and optional documentation ingestion, read Getting started.

Useful development commands

make help       # list repository-owned commands
make build      # build the frontend and backend
make test       # run shell contracts and JVM tests
make lint       # run frontend and JVM static analysis
make health     # check the running application

To work only on the npm package:

cd cli
npm install
npm run dev -- --help
npm test

Index documentation and repositories

Documentation ingestion is optional for ordinary application development. Run it only after the gateway and Qdrant preflight checks pass.

make full-pipeline
REPO_PATH=/absolute/path/to/repository make process-github-repo
REPO_URL=https://github.com/owner/repository make process-github-repo
SYNC_EXISTING=1 make process-github-repo

See Pipeline commands for source selection and ingestion controls, and GitHub repository ingestion for repository synchronization.

Documentation

• Documentation index
• Getting started
• Architecture
• HTTP and streaming API
• Contributing

License

See LICENSE.md.