Resolving Tenant IDs

Arc resolves tenant IDs through pluggable strategies. Each request is evaluated by the configured resolver, and the resulting tenant ID becomes the active tenant context for the request lifecycle.

Built-In Resolvers

Header Resolver (Default)

Resolves the tenant ID from an HTTP header.

builder.AddCratisArcCore(options =>
{
    options.UseHeaderTenancy("X-Tenant-ID");
});

Default header name: x-cratis-tenant-id

Query Parameter Resolver

Resolves the tenant ID from a query string parameter.

builder.AddCratisArcCore(options =>
{
    options.UseQueryTenancy("tenant");
});

Default parameter name: tenantId

Claim Resolver

Resolves the tenant ID from a claim on the authenticated user.

builder.AddCratisArcCore(options =>
{
    options.UseClaimTenancy("tenant_id");
});

Default claim type: tenant_id

Subdomain Resolver

Resolves the tenant ID from the first segment of the request hostname. When the hostname has no subdomain (a single segment), it falls back to the configured HTTP header.

builder.AddCratisArcCore(options =>
{
    options.UseSubdomainTenancy("X-Tenant-ID");
});

A request to acme.myapp.com resolves the tenant as acme. A request to myapp.com falls back to the X-Tenant-ID header. This pattern is useful for SaaS applications where each tenant is routed through its own subdomain.

Default fallback header: x-cratis-tenant-id

Development Resolver

Uses a fixed tenant ID for local development.

builder.AddCratisArcCore(options =>
{
    options.UseDevelopmentTenancy("my-test-tenant");
});

Default tenant ID: development