> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.nvidia.com/nemo/relay/v0.9.4/reference/api/rust-library-reference/nemo-relay/error/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.nvidia.com/nemo/relay/_mcp/server.

# Module error

> Error types for the NeMo Relay runtime.

Generated from `cargo doc --no-deps -p nemo-relay -p nemo-relay-adaptive -p nemo-relay-pii-redaction -p nemo-relay-ffi -p nemo-relay-types -p nemo-relay-plugin -p nemo-relay-worker-proto -p nemo-relay-worker`.

Error types for the NeMo Relay runtime.

All fallible operations in the runtime return [`Result<T>`](/reference/api/rust-library-reference/nemo-relay/error/type-result), which uses [`FlowError`](/reference/api/rust-library-reference/nemo-relay/error/enum-flowerror) as the error type. Errors are categorized by cause (duplicate registration, missing entity, guardrail rejection, etc.).

## Structs

* [UpstreamFailure](/reference/api/rust-library-reference/nemo-relay/error/struct-upstreamfailure): Structured failure returned by one upstream provider attempt.

## Enums

* [FlowError](/reference/api/rust-library-reference/nemo-relay/error/enum-flowerror): The error type for all NeMo Relay runtime operations.
* [UpstreamFailureClass](/reference/api/rust-library-reference/nemo-relay/error/enum-upstreamfailureclass): Stable classification for a failure from an upstream provider attempt.

## Type Aliases

* [Result](/reference/api/rust-library-reference/nemo-relay/error/type-result): A specialized [`Result`](https://doc.rust-lang.org/1.96.1/core/result/enum.Result.html) type for NeMo Relay operations.

> Error types for the NeMo Relay runtime.

## Docs

- [Struct Upstream Failure](https://docs.nvidia.com/nemo/relay/v0.9.4/reference/api/rust-library-reference/nemo-relay/error/struct-upstreamfailure.md): Structured failure returned by one upstream provider attempt.
- [Enum Flow Error](https://docs.nvidia.com/nemo/relay/v0.9.4/reference/api/rust-library-reference/nemo-relay/error/enum-flowerror.md): The error type for all NeMo Relay runtime operations.
- [Enum Upstream Failure Class](https://docs.nvidia.com/nemo/relay/v0.9.4/reference/api/rust-library-reference/nemo-relay/error/enum-upstreamfailureclass.md): Stable classification for a failure from an upstream provider attempt.
- [Type Alias Result](https://docs.nvidia.com/nemo/relay/v0.9.4/reference/api/rust-library-reference/nemo-relay/error/type-result.md): A specialized `Result` type for NeMo Relay operations.