atmosphere is a free, open source ai development platforms project written in Java and released under Apache-2.0. It has 3,812 GitHub stars, 761 forks and 10 open issues, and was last pushed 4 days ago. On this registry it ranks #97 of 116 tracked projects in AI Development Platforms, with 5 head-to-head comparisons available.

Atmosphere

The real-time engine for AI agents on the JVM. Tokens flow from the LLM runtime to the client through a broadcaster you can filter, gate, and observe — over WebSocket, SSE, long-polling, or gRPC, and out through MCP, A2A, and AG-UI. A plain @Agent is a full deep agent, batteries-included, and Atmosphere handles reconnect, authorization, and governance.

Maven Central npm CI: Core CI: E2E CI: atmosphere.js


Atmosphere is built for teams that need AI agents to behave like production services: streaming over real transports, guarded before every tool call, observable by tenant and run, and portable across AI frameworks without rewriting the endpoint.

Why Atmosphere

Need What Atmosphere provides
Stream to real clients WebSocket, SSE, long-polling, and gRPC run through one broadcaster pipeline as always-on defaults; WebTransport over HTTP/3 is optional
Swap AI integrations One AgentRuntime SPI with twelve runtime adapters and contract-tested capability flags
Ship a deep agent A plain @Agent is batteries-included — memory, a plan (write_todos), a virtual filesystem, and sub-agent delegation (task), on by default via the harness
Govern execution Policy admission, @AgentScope, human approval, plan-and-verify, cost ceilings, PII rewriting, and admin kill switches
Pause for humans Durable HITL approvals hibernate without holding a thread, persist workflow state, and resume through REST approval surfaces
Resume long runs Durable sessions, run IDs, replay buffers, checkpoints, and reconnect-safe continuation
Observe and replay An opt-in session tape records session-boundary AI events (SQLite-durable) — reconstruct a run or a coordination tree with no model call, then distill a smaller model from it
Expose the same agent everywhere Browser endpoints plus MCP (stateless RC on the MCP 2026-07-28 spec, sessions back to 2024-11-05), A2A, AG-UI, Slack, Telegram, Discord, WhatsApp, and Messenger modules

Scope

Atmosphere is a real-time, event-driven framework, not an agent-hosting platform. We ship the primitives your application uses at runtime; the host you choose (Tomcat, Jetty, Netty, Undertow, Quarkus, Spring Boot, or any servlet container) owns compute and scheduling. Payment rails and commerce primitives are out of scope. Compared to the agent-platform stack vocabulary that has emerged around offerings like Cloudflare Agents, AWS Bedrock Agents, and Vertex AI Agents:

Layer What Atmosphere ships Provided by your stack
Streaming transport atmosphere-runtime over WebSocket, SSE, long-polling (always-on defaults), gRPC, plus optional WebTransport/HTTP-3 (needs jetty-http3-server or reactor-netty-http on the classpath plus a dev cert)
Runtime dispatch atmosphere-ai AgentRuntime SPI + 12 adapters with contract-tested capability flags Model hosting (we call providers; we do not host weights)
Orchestration @Coordinator, AgentFleet, handoffs, conditional routing, an event-sourced coordination journal with causal lineage, result evaluation, and durable hibernating Workflow over CheckpointStore (Temporal-backed if you add atmosphere-checkpoint-temporal) — durable step execution, not wall-clock triggering Cron / wall-clock scheduling (your container scheduler or a dedicated scheduler fires the workflow)
Memory AiConversationMemory per-conversation history and LongTermMemory per-user facts — in-memory, or durable SQLite/Redis via atmosphere-durable-sessions{-sqlite,-redis} — plus SemanticRecallInterceptor for BYO vector-store recall Managed vector stores (use Spring AI's VectorStore, LangChain4j embeddings, or your own)
Governance Policy admission, @AgentScope, plan-and-verify, PII redaction, cost ceilings, durable HITL approvals, admin kill switches
Protocol surface MCP, A2A, AG-UI, Slack/Telegram/Discord/WhatsApp/Messenger channel adapters
Code execution atmosphere-sandbox SandboxProvider SPI + DockerSandboxProvider default Browser automation, headless Chromium
SDK atmosphere.js (React, Vue, Svelte, React Native, vanilla TS), wasync (JVM client)

The differentiator is the streaming + JVM + governance combination: long-lived stateful agent sessions over real-time transports, with policy admission on the critical path. For stateless, bursty, autonomous agents that should hibernate when idle, a serverless agent platform is usually the better fit. For human-in-the-loop, multi-channel, governed agents inside an existing JVM stack, Atmosphere is the right fit.

Quick Start

Run a sample

brew install Atmosphere/tap/atmosphere

# Or:
curl -fsSL https://raw.githubusercontent.com/Atmosphere/atmosphere/main/cli/install.sh | sh

atmosphere run spring-boot-multi-agent-startup-team

Create an app

atmosphere new my-agent --template ai-chat
cd my-agent
LLM_API_KEY=your-key ./mvnw spring-boot:run

Swap the runtime adapter

# Built-in is the default. --runtime spring-ai scaffolds the app against the
# Spring AI adapter instead (a CLI overlay injects its Maven dependencies).
atmosphere new my-agent --template ai-chat --runtime spring-ai

# Use --force when a sample already pins a runtime adapter.
atmosphere new my-agent --template ai-tools --runtime langchain4j --force

Import a skill

atmosphere import https://github.com/anthropics/skills/blob/main/skills/frontend-design/SKILL.md
cd frontend-design
LLM_API_KEY=your-key ./mvnw spring-boot:run

@Agent

One annotation declares the agent. Modules on the classpath decide which endpoints and integrations are registered.

@Agent(name = "my-agent", description = "What this agent does")
public class MyAgent {

    @Prompt
    public void onMessage(String message, StreamingSession session) {
        session.stream(message);
    }

    @Command(value = "/status", description = "Show status")
    public String status() {
        return "All systems operational";
    }

    @Command(value = "/reset", description = "Reset data",
             confirm = "This will delete all data. Are you sure?")
    public String reset() {
        return dataService.resetAll();
    }

    @AiTool(name = "lookup", description = "Look up data")
    public String lookup(@Param("query") String query) {
        return dataService.find(query);
    }
}
Module on classpath What gets registered
atmosphere-agent Browser endpoint at /atmosphere/agent/my-agent, streaming AI dispatch, memory, commands, /help
atmosphere-mcp MCP endpoint at /atmosphere/agent/my-agent/mcp — session protocol plus the stateless RC on the MCP 2026-07-28 spec (Tasks, MCP Apps, OAuth resource server)
atmosphere-a2a A2A endpoint at /atmosphere/agent/my-agent/a2a with Agent Card discovery
atmosphere-agui AG-UI endpoint at `/atmosphere/agent/my-agent/a

readme truncated — read the full docs on github

Frequently asked questions

Is atmosphere free to use?

atmosphere is open source under the Apache-2.0 licence. There is no licence fee and no seat count — you can self-host it or, where the project offers one, pay a vendor for a managed version instead.

What does atmosphere do?

Portable AI agent runtime for the JVM. One @Agent class runs on Spring AI, LangChain4j, Anthropic, or 9 more behind one SPI. Token streaming, tool calls, human

What is atmosphere written in?

atmosphere is primarily written in Java. Its source is publicly available at https://github.com/Atmosphere/atmosphere, and it has 3,812 GitHub stars.