diff --git a/src/layers/6_client/chainExtensions/scalar.test-d.ts b/src/layers/6_client/chainExtensions/scalar.test-d.ts
new file mode 100644
index 000000000..892070510
--- /dev/null
+++ b/src/layers/6_client/chainExtensions/scalar.test-d.ts
@@ -0,0 +1,11 @@
+import { schemaMap } from '../../../../tests/_/schemas/kitchen-sink/graffle/__.js'
+import { Graffle } from '../../../entrypoints/__Graffle.js'
+import { assertEqual } from '../../../lib/assert-equal.js'
+import type { SomeFunction } from '../../../lib/prelude.js'
+import type { TypeErrorMissingSchemaMap } from './scalar.js'
+
+const g1 = Graffle.create({ schema: `foo` })
+assertEqual<typeof g1.scalar, TypeErrorMissingSchemaMap>()
+
+const g2 = Graffle.create({ schema: `foo`, schemaMap })
+assertEqual<typeof g2.scalar, SomeFunction>()
diff --git a/src/layers/6_client/chainExtensions/scalar.ts b/src/layers/6_client/chainExtensions/scalar.ts
index a0922bf68..1fe3448c4 100644
--- a/src/layers/6_client/chainExtensions/scalar.ts
+++ b/src/layers/6_client/chainExtensions/scalar.ts
@@ -7,15 +7,25 @@ import { type Context } from '../context.js'
 export interface Scalar_ extends Chain.Extension {
   context: Context
   // @ts-expect-error untyped params
-  return: Scalar<this['params']>
+  return: Simplify<ScalarExtension<this['params']>>
 }
 
-type Scalar<$Args extends Chain.Extension.Parameters<Scalar_>> = {
+interface ScalarExtension<$Args extends Chain.Extension.Parameters<Scalar_>> {
+  /**
+   * TODO Docs.
+   */
+  scalar: null extends $Args['context']['schemaMap'] ? TypeErrorMissingSchemaMap : ScalarMethod<$Args>
+}
+
+export type TypeErrorMissingSchemaMap =
+  `Error: Your client must have a schemaMap in order to apply registered scalars. Therefore we're providing this static error type message here instead of allowing you continue registering scalars that will never be applied.`
+
+type ScalarMethod<$Args extends Chain.Extension.Parameters<Scalar_>> = {
   /**
    * TODO Docs.
    */
   // TODO limit $Name to what is in the schema.
-  scalar<$Name extends string, $Decoded>(name: $Name, $Codec: {
+  <$Name extends string, $Decoded>(name: $Name, $Codec: {
     decode: (value: string) => $Decoded
     encode: (value: $Decoded) => string
   }): Chain.Definition.MaterializeWithNewContext<
@@ -29,10 +39,10 @@ type Scalar<$Args extends Chain.Extension.Parameters<Scalar_>> = {
     >
   >
 
-  /**
+  /*
    * TODO Docs.
    */
-  scalar<$Scalar extends Schema.Scalar>(scalar: $Scalar): Chain.Definition.MaterializeWithNewContext<
+  <$Scalar extends Schema.Scalar>(scalar: $Scalar): Chain.Definition.MaterializeWithNewContext<
     $Args['chain'],
     ConfigManager.SetAtPath<
       $Args['context'],
@@ -64,5 +74,5 @@ export const scalarProperties = Chain.Extension.create<Scalar_>((builder, state)
         },
       })
     },
-  }
+  } as any
 })
diff --git a/src/lib/prelude.ts b/src/lib/prelude.ts
index ba3ce1908..47177d057 100644
--- a/src/lib/prelude.ts
+++ b/src/lib/prelude.ts
@@ -255,7 +255,7 @@ export const capitalizeFirstLetter = (string: string) => string.charAt(0).toUppe
 
 export type SomeAsyncFunction = (...args: unknown[]) => Promise<unknown>
 
-export type SomeFunction = (...args: unknown[]) => MaybePromise<unknown>
+export type SomeFunction = (...args: unknown[]) => MaybePromise<any>
 
 export type Deferred<T> = {
   promise: Promise<T>
diff --git a/tests/_/helpers.ts b/tests/_/helpers.ts
index 20e063dde..9e70039ee 100644
--- a/tests/_/helpers.ts
+++ b/tests/_/helpers.ts
@@ -5,7 +5,7 @@ import * as Path from 'node:path'
 import type { Mock } from 'vitest'
 import { test as testBase, vi } from 'vitest'
 import { Graffle } from '../../src/entrypoints/main.js'
-import type { Context } from '../../src/entrypoints/utilities-for-generated.js'
+import type { Context, SchemaDrivenDataMap } from '../../src/entrypoints/utilities-for-generated.js'
 import type { Client } from '../../src/layers/6_client/client.js'
 import type { ConfigManager } from '../../src/lib/config-manager/__.js'
 import { Grafaid } from '../../src/lib/grafaid/__.js'
@@ -37,8 +37,8 @@ interface Fixtures {
   fetch: Mock<(request: Request) => Promise<Response>>
   pokemonService: SchemaService
   graffle: Client<Context>
-  kitchenSink: Client<ConfigManager.SetAtPath<Context, ['name'], 'default'>>
-  kitchenSinkHttp: Client<ConfigManager.SetAtPath<Context, ['name'], 'default'>>
+  kitchenSink: Client<ConfigManager.SetProperties<Context, { name: `default`; schemaMap: SchemaDrivenDataMap }>>
+  kitchenSinkHttp: Client<ConfigManager.SetProperties<Context, { name: `default`; schemaMap: SchemaDrivenDataMap }>>
   kitchenSinkData: typeof db
   project: Project
 }