> For the complete documentation index, see [llms.txt](https://kerno.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kerno.gitbook.io/docs/getting-started/faqs.md).

# FAQs

<details>

<summary>What is Kerno?</summary>

Kerno is local CI for AI-generated backend code. It gives your coding agent (or IDE) the feedback loop it needs to verify and fix its work in context, so what ships works as part of your system.

Unlike static code review tools or unit tests that run in isolation, Kerno runs every change against your real stack and validates it across functional behavior, error handling, edge cases, security, auth, and response content.

</details>

<details>

<summary>What makes Kerno different from other tools</summary>

Most code tools either statically analyze your code or run unit tests in isolation against mocks. Kerno does neither.

**It knows the exact blast radius of every change.** Kerno indexes your code deterministically, so it can tell you precisely which endpoints a change affects, following the call graph rather than returning approximate matches from vector embeddings.

**It tests against your real stack.** Scenarios run against your actual running application and its real databases and queues, not mocks.

**You don't write or maintain the tests.** Kerno generates them, and updates them when your endpoints change on purpose, always showing you a plan before it touches your repository.

</details>

<details>

<summary>Does Kerno support my backend stack?</summary>

Most likely, yes. Kerno detects endpoints in TypeScript, JavaScript, Python, Java, Kotlin, Scala, Go, Ruby, PHP, C#, Rust, and Swift, across the common web framework for each.

Your scenarios are always written in TypeScript and reach your application over HTTP, so the language your service is written in doesn't change how tests run.

Kerno can also connect directly to PostgreSQL, MySQL, MariaDB, MongoDB, Redis, Kafka, RabbitMQ, ClickHouse, Azure Storage, S3-compatible object storage, and Zitadel, for setting up and verifying state your API can't express.

The full matrix lives in [Supported technologies](/docs/references/supported-technologies.md).

</details>

<details>

<summary>Does Kerno store my code</summary>

No. Kerno never stores your source code on its servers. Relevant excerpts pass through Kerno's proxy to LLM providers (Anthropic and OpenAI) configured with zero-data-retention tiers, so nothing is persisted on the provider side either.

Note that when you review a test run in the IDE extension, the run report is uploaded so your team can view it in the portal. That report includes the request and response payloads your application produced during the run. See [Security & Privacy](/docs/references/security-and-privacy.md).

</details>

<details>

<summary>Does Kerno use my code for training or fine tuning LLMs?</summary>

No. Kerno doesn't train models. The LLM providers Kerno uses run on zero-data-retention tiers, so your code isn't stored, logged, or used for training on their side.

</details>

<details>

<summary>Are there discounts available for startups?</summary>

Kerno offers free usage for qualified Open Source Projects and a significant discounts for pre-Series A startups. [Drop us a note](https://www.kerno.io/contact) to check your availability.

</details>

<details>

<summary>Does Kerno work with my coding agent?</summary>

Yes, if your agent supports MCP. Kerno exposes a set of MCP tools your agent calls to connect to your running app, generate tests, and validate changes. Claude Code, Cursor, Windsurf, and Codex are the verified setups.

For Claude Code, Cursor, and Codex there is also a plugin that installs and wires everything up for you. See the [Quickstart](/docs/getting-started/quickstart.md).

</details>

<details>

<summary>Do I need an IDE extension?</summary>

No. You can drive Kerno entirely from your coding agent via MCP. The IDE extension is an alternative for editor-driven workflows, with a panel that shows endpoints, scenario plans, diffs, and reports. You can use both surfaces side by side.

See the [Quickstart](/docs/getting-started/quickstart.md) for connection details.

</details>

<details>

<summary>What if I'm not using a coding agent?</summary>

Kerno still works. The IDE extension gives you a panel-driven workflow for the same loop: connect Kerno to your running app, generate tests for an endpoint, and validate a change.

</details>

{% hint style="info" %}
If you encounter issues or have questions, [message us on Discord](https://discord.gg/k8yA9tZdP9), and we’ll gladly help.
{% endhint %}