diff --git a/README.md b/README.md
index 4ab94f7..6cab0cc 100644
--- a/README.md
+++ b/README.md
@@ -111,6 +111,7 @@ This is just a taster. Places you can go next:
     - [Input Defaults](#input-defaults)
     - [Input Transformation](#input-transformation)
     - [Input Validation](#input-validation)
+    - [Update](#update)
     - [Metadata](#metadata)
     - [Chaining API](#chaining-api)
     - [Codecs](#codecs)
@@ -456,6 +457,14 @@ const circle = circle.create({ radius: -10 })
 // throws
 ```
 
+### Update
+
+You can update records. Updating creates shallow copies of data. The validation, transformations, defaults etc. setup on the zod schema will re-run on the update function ensuring data integrity. Any errors there will be thrown.
+
+```ts
+const circleUpdated = circle.update(circle, { radius: 5 })
+```
+
 ### Metadata
 
 The controller gives you access to metadata about your record:
diff --git a/src/record/runtime.ts b/src/record/runtime.ts
index 09daaa4..5d1224a 100644
--- a/src/record/runtime.ts
+++ b/src/record/runtime.ts
@@ -100,8 +100,14 @@ export function record<Name extends string>(
           return current.schema.passthrough().parse(data) as object
         },
         //eslint-disable-next-line
-        is$: (value: unknown) => is(value, symbol),
-        is: (value: unknown) => is(value, symbol),
+        is$: (value) => is(value, symbol),
+        is: (record) => is(record, symbol),
+        update: (record, changes) => {
+          return controller.create({
+            ...record,
+            ...changes,
+          }) as object
+        },
         from: {
           json: (json: string) => {
             const data = tryOrNull(() => JSON.parse(json) as object)
diff --git a/src/record/types/controller.ts b/src/record/types/controller.ts
index 2e579e8..7487227 100644
--- a/src/record/types/controller.ts
+++ b/src/record/types/controller.ts
@@ -1,5 +1,5 @@
 import { SomeSchema, SomeSchemaDef } from '../../core/internal.js'
-import { Encoder, SomeName, StoredRecords } from '../../core/types.js'
+import { Encoder, OmitTag, SomeName, StoredRecords } from '../../core/types.js'
 import { OmitRequired, Rest } from '../../lib/utils.js'
 import { z } from '../../lib/z/index.js'
 import { SomeDecodeOrThrowJson, SomeDecoderJson, SomeDefaultsProvider, SomeEncoderJson } from './internal.js'
@@ -24,9 +24,13 @@ export type SomeRecordController = {
   }
   name: string
   schema: SomeSchema
+  // !! HACK not-using any here results in test type errors that I don't understand yet.
   // eslint-disable-next-line
-  is: (value: any) => boolean
+  is: (record: any) => boolean
   is$: (value: unknown) => boolean
+  // !! HACK not-using any here results in test type errors that I don't understand yet.
+  // eslint-disable-next-line
+  update: (record: any, changes: object) => object
   // eslint-disable-next-line
   create: (params?: any) => any
   from: {
@@ -92,6 +96,11 @@ export type RecordController<Rs extends StoredRecords, R extends SomeStoredRecor
   }
   name: R[`name`]
   schema: R['schema']
+  /**
+   * 
+   * @throws If zod schema violated: bad types, failed validation, throw from a transformer.
+   */
+  update(record: StoredRecord.GetType<R>, changes: Partial<OmitTag<StoredRecord.GetType<R>>>): StoredRecord.GetType<R>
   /**
    * Decoders for this record. Decoders are used to transform other representations of your record back into a record instance.
    */
@@ -101,13 +110,13 @@ export type RecordController<Rs extends StoredRecords, R extends SomeStoredRecor
      *
      * @remarks This is a built in decoder.
      */
-    json: (value: string) => null | StoredRecord.GetType<R>
+    json(value: string): null | StoredRecord.GetType<R>
     /**
      * Decode JSON into this record. Throws if it fails for any reason.
      *
      * @remarks This is a built in decoder.
      */
-    jsonOrThrow: (value: string) => StoredRecord.GetType<R>
+    jsonOrThrow(value: string): StoredRecord.GetType<R>
   } & Decoders<R['codec'], R>
   // & {
   //   [I in IndexKeys<V['codec']> as AsString<V['codec'][I]>]: Decoder<V['codec']>,V>
@@ -121,7 +130,7 @@ export type RecordController<Rs extends StoredRecords, R extends SomeStoredRecor
      *
      * @remarks This is a built in encoder.
      */
-    json: (record: StoredRecord.GetType<R>) => string
+    json(record: StoredRecord.GetType<R>): string
   } & Encoders<R['codec'], R>
   /**
    * Strict predicate/type guard for this record.
diff --git a/tests/record/other/update.spec.ts b/tests/record/other/update.spec.ts
new file mode 100644
index 0000000..169fb39
--- /dev/null
+++ b/tests/record/other/update.spec.ts
@@ -0,0 +1,32 @@
+import { Alge } from '../../../src/index.js'
+import { A, a } from '../../__helpers__.js'
+import { expectType } from 'tsd'
+import { z } from 'zod'
+
+it(`updates record by copy`, () => {
+  // eslint-disable-next-line
+  expectType<(data: A, changes: Partial<A>) => A>(A.update)
+  const a_ = A.update(a, { m: `updated` })
+  expect(a).toMatchObject({ m: `m` })
+  expect(a_).not.toBe(a)
+  expect(a_).toEqual({ _tag: `A`, m: `updated`, _: { tag: `A`, symbol: A._.symbol } })
+})
+
+it(`updates triggers validate etc.`, () => {
+  const A = Alge.record(`A`, {
+    m: z.string().regex(/abc/),
+  })
+  const a = A.create({ m: `abc` })
+  expect(() => A.update(a, { m: `updated` })).toThrowErrorMatchingInlineSnapshot(`
+    "[
+      {
+        "validation": "regex",
+        "code": "invalid_string",
+        "message": "Invalid",
+        "path": [
+          "m"
+        ]
+      }
+    ]"
+  `)
+})