What is NATS?
NATS is a messaging server: programs publish messages to named subjects (such as tasks.summarise) and any program subscribed to that subject receives them. Out of the box this is fire-and-forget: a message reaches whoever is listening at that moment and is never replayed. JetStream, built into the same server, adds persistence. Messages are stored in streams on memory or disk, survive restarts, are redelivered until a worker acknowledges them, and can be read again from any point. JetStream also provides a key-value store and an object store for files larger than one message.
For teams running agents, that covers the plumbing between independent workers: a planner hands jobs to a pool of tool-running workers, results flow back, and nothing is lost if a worker crashes mid-task. The server runs on-premise, in the cloud, at the edge or on a Raspberry Pi, and the README counts over 40 client language implementations.
NATS is a CNCF project under the Apache 2.0 licence. Synadia, its main maintainer, tried in April 2025 to take the project out of the CNCF and move future releases to the Business Source Licence; the dispute was settled on 1 May 2025, with Synadia assigning the NATS trademarks to the Linux Foundation and the code staying Apache 2.0. Synadia sells a hosted service, Synadia Cloud, and in 2026 launched an Agents SDK built on a draft NATS Agent Protocol.
How much does NATS cost?
| Plan | Price | What you get |
|---|---|---|
| Personal | Free | 10 connections, 5 GiB storage |
| Starter | $49/month | 100 connections |
| Pro | $199/month | 1,000 connections, 1 TiB network data |
| Enterprise | Custom |
Free and open source under Apache 2.0. Synadia Cloud (hosted NATS): Personal free (10 connections, 10 GiB network data, 5 GiB storage); Starter $49/month (100 connections); Pro $199/month (1,000 connections, 1 TiB network data); Enterprise by quote. Overage from $0.01 to $0.09 per GiB; Remote System add-on $49/month to manage your own cluster.
Is NATS worth it?
NATS is the least ceremonial way to give independent agent workers a shared, durable queue. One Go binary started with JetStream enabled gives you subjects to publish to, streams that keep messages until a worker acknowledges them, and a key-value store for small shared state such as a task's status. Kafka asks for far more operational care for the same job, and a Redis list has no replay. The project is mature: about 21,000 GitHub stars, Apache 2.0, and version 2.15.2 released on 26 October 2026.
The guarantees are worth understanding before an agent depends on them. Core NATS delivers at most once: a worker that is offline misses the message for good. JetStream redelivers anything not acknowledged in time, which is at-least-once, so a slow tool call can run twice unless the worker is idempotent. The docs describe exactly-once publishing through a Nats-Msg-Id header, but the duplicate window defaults to 2 minutes, shorter than many LLM retries. Long agent runs that must resume halfway through after a crash still need a workflow engine or your own checkpoints; NATS moves the work, it does not remember where a plan had got to.
Security is the heaviest line in the ledger. The repository lists 27 security advisories published in 2026 alone, 12 of them rated high, mostly in MQTT, WebSocket, leaf node and authorisation code, including pre-authentication crashes. None is unusual for a server exposed to a network, and fixes ship promptly, but a team that installs NATS once and never upgrades is carrying real risk. A Trail of Bits audit, commissioned through OSTIF, was published in April 2025.
Synadia's 2025 attempt to relicense under the BSL failed, and the settlement left the trademark with the Linux Foundation, which makes the open-source core safer to build on than it looked that spring. Its 2026 Agents SDK and draft NATS Agent Protocol, at version 0.3.0, are interesting for agents that must find each other across networks, but they are Synadia's layer, not the CNCF project, and the spec itself still marks guaranteed delivery as future work.
Where it earns its place
A platform engineer at a 30-person start-up running a research agent
Hand web-scraping and summarising jobs to a pool of workers and survive a worker crash
The planner publishes each job to a JetStream work-queue stream; workers pull, process and acknowledge, and unacknowledged jobs are redelivered. One three-node cluster on small VMs covers it; the cost is the VMs and keeping the server patched.
An AI team at a logistics firm with agents on warehouse edge devices
Move events from sites with patchy connectivity to central models
Leaf nodes at each site buffer locally and forward to the central cluster when the link returns. This is the case NATS was designed for, though leaf node code accounted for several 2026 advisories, so the edge fleet needs an upgrade path.
A head of engineering at a 10-person agency prototyping multi-agent tools
Try agent messaging without running servers
Synadia Cloud's free Personal plan allows 10 connections and 5 GiB of storage, enough for a prototype; Starter at $49 a month raises connections to 100. Personal drops connections when it exceeds its limits rather than billing overage.
Before you commit
- Setup
- Download the nats-server binary or run the official Docker image with JetStream enabled (nats-server -js); no other dependencies are needed. Production clusters use the Helm chart on Artifact Hub.
- Integrations
- Official clients in over 40 languages, including Go, Python, TypeScript, Java, Rust and .NET; MQTT and WebSocket listeners; Synadia's Agents SDK for TypeScript and Python sits on top.
- Data and privacy
- Self-hosted messages stay on your servers; JetStream stores them in memory or on disk according to each stream's retention rules. Apache 2.0, no commercial-use limits. 27 GitHub security advisories published in 2026, 12 rated high.
- Cost at scale
- Self-hosting costs only the machines. Synadia Cloud Pro is $199 a month for 1,000 connections, 1 TiB of network data and 50 GiB of storage, with client egress overage at $0.09 per GiB; Enterprise is quoted.
- Limits
- At-least-once delivery means duplicate jobs unless workers are idempotent; the deduplication window defaults to 2 minutes; Synadia Cloud caps message size at 1 MiB on Personal and Starter and 8 MiB on Enterprise. About 475 open issues and pull requests.
What’s good
- Single binary; JetStream adds persistence without a second system
- Durable work queues, replay, key-value and object store in one server
- Over 40 client languages and runs from a Raspberry Pi to multi-region clusters
- Apache 2.0, with the trademark held by the Linux Foundation since 2025
What’s not
- 27 security advisories in 2026; upgrades cannot wait
- At-least-once by default; workers must tolerate duplicate jobs
- No workflow state or resumable steps for long agent runs
- Agent protocol is Synadia's and still a draft
Best for
Teams running several independent agent or tool workers that need durable job queues and fan-out without operating Kafka.
NATS: common questions
- Is NATS worth it?
- Light enough to run beside a single agent and sturdy enough to carry work between hundreds of them, provided you treat its security patches as urgent. We rate it 4.2 out of 5.
- How much does NATS cost?
- Free and open source under Apache 2.0. Synadia Cloud (hosted NATS): Personal free (10 connections, 10 GiB network data, 5 GiB storage); Starter $49/month (100 connections); Pro $199/month (1,000 connections, 1 TiB network data); Enterprise by quote. Overage from $0.01 to $0.09 per GiB; Remote System add-on $49/month to manage your own cluster.
- What are the downsides of NATS?
- 27 security advisories in 2026; upgrades cannot wait; at-least-once by default; workers must tolerate duplicate jobs; no workflow state or resumable steps for long agent runs; agent protocol is Synadia's and still a draft.
- Who is NATS best for?
- Teams running several independent agent or tool workers that need durable job queues and fan-out without operating Kafka.
- How much does NATS cost for a team or in production?
- Self-hosting costs only the machines. Synadia Cloud Pro is $199 a month for 1,000 connections, 1 TiB of network data and 50 GiB of storage, with client egress overage at $0.09 per GiB; Enterprise is quoted.
- Is NATS safe for company data?
- Self-hosted messages stay on your servers; JetStream stores them in memory or on disk according to each stream's retention rules. Apache 2.0, no commercial-use limits. 27 GitHub security advisories published in 2026, 12 rated high.
Answers checked Nov 9, 2026.
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