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redis-vl-dotnet

SemanticRouter

SemanticRouter maps an input embedding to the nearest stored route reference. It is useful when one incoming request needs to be classified into a workflow, intent, or tool category before the application continues.

Schema and options

Each router instance builds a HASH-backed index with:

  • routeName

  • reference

  • one vector field for the route embedding

SemanticRouterOptions configures the router name, vector field attributes, distance threshold, optional namespace, and optional field names.

DistanceThreshold is the key routing control. When the nearest route falls outside the threshold, RouteAsync returns null.

Add and route flows

API Behavior

AddRouteAsync(routeName, reference, embedding)

Stores one route document keyed from the route name plus reference text.

AddRouteAsync(routeName, reference, vectorizer)

Vectorizes the reference text before storing the route.

RouteAsync(input, embedding)

Returns the nearest SemanticRouteMatch inside the configured threshold.

RouteAsync(input, vectorizer)

Vectorizes the incoming input before matching.

As with the other higher-level vector workflows, prefer ITextVectorizer rather than the obsolete ITextEmbeddingGenerator shim.

Practical routing pattern

A common pattern is:

  1. create the router during startup

  2. seed a small route set such as billing, support, and sales

  3. vectorize each incoming utterance

  4. route to the matching workflow only when the distance threshold is acceptable

If you need to keep the original chat transcript and query it later, pair this API with MessageHistory or SemanticMessageHistory.

Example

The runnable example for this API is /examples/SemanticRouterExample.

It demonstrates:

  • creating a router with a local sample vectorizer

  • adding routes for multiple intents

  • routing a new utterance to the nearest stored reference

  • cleaning up the router index and documents

The contract details are also covered in tests/RedisVL.Tests/Workflows/SemanticRouterTests.cs and tests/RedisVL.Tests/Workflows/SemanticRouterIntegrationTests.cs.

Related sections