diff --git a/js/package.json b/js/package.json
index b85271cb8..7b68f64a1 100644
--- a/js/package.json
+++ b/js/package.json
@@ -37,6 +37,13 @@
       "require": "./dist/index.js",
       "default": "./dist/index.mjs"
     },
+    "./custom-views": {
+      "types": "./dist/custom-views.d.ts",
+      "import": "./dist/custom-views.mjs",
+      "module": "./dist/custom-views.mjs",
+      "require": "./dist/custom-views.js",
+      "default": "./dist/custom-views.mjs"
+    },
     "./workerd": {
       "import": "./dist/workerd.mjs",
       "require": "./dist/workerd.js",
diff --git a/js/src/custom-views/exports.test.ts b/js/src/custom-views/exports.test.ts
new file mode 100644
index 000000000..44935887d
--- /dev/null
+++ b/js/src/custom-views/exports.test.ts
@@ -0,0 +1,145 @@
+import { describe, expect, expectTypeOf, test } from "vitest";
+import * as customViewsExports from "./exports";
+import { customDatasetView, customTraceView } from "./exports";
+
+describe("custom views", () => {
+  test("only exposes the public custom view helpers", () => {
+    expect(Object.keys(customViewsExports).sort()).toEqual([
+      "customDatasetView",
+      "customTraceView",
+    ]);
+  });
+
+  test("creates trace custom view definitions", () => {
+    const component = (props: { span: { span_id: string } }) =>
+      props.span.span_id;
+
+    const returned = customTraceView(
+      {
+        name: "Trace Summary",
+        slug: "trace-summary",
+        project: { name: "my-project" },
+      },
+      component,
+    );
+
+    expect(returned).toEqual({
+      kind: "trace",
+      name: "Trace Summary",
+      slug: "trace-summary",
+      project: { name: "my-project" },
+      component,
+    });
+  });
+
+  test("creates dataset custom view definitions", () => {
+    const component = (props: { id: string }) => props.id;
+
+    const returned = customDatasetView(
+      {
+        name: "Dataset Row",
+        slug: "dataset-row",
+        dataset: { id: "dataset-id" },
+        project: "my-project",
+      },
+      component,
+    );
+
+    expect(returned).toEqual({
+      kind: "dataset",
+      name: "Dataset Row",
+      slug: "dataset-row",
+      dataset: { id: "dataset-id" },
+      project: "my-project",
+      component,
+    });
+  });
+
+  test("allows default-export-friendly view values", () => {
+    const first = () => "first";
+    const second = () => "second";
+
+    const traceView = customTraceView(
+      {
+        name: "First",
+        slug: "shared",
+      },
+      first,
+    );
+    const datasetView = customDatasetView(
+      {
+        name: "Second",
+        slug: "shared",
+        dataset: { name: "rows" },
+      },
+      second,
+    );
+
+    const defaultTraceExport = traceView;
+    const defaultDatasetExport = datasetView;
+    expect(defaultTraceExport.component).toBe(first);
+    expect(defaultDatasetExport.component).toBe(second);
+  });
+
+  test("preserves trace view generic prop types", () => {
+    type Input = { prompt: string };
+    type Output = { answer: string };
+    type Expected = { answer: string };
+    type Metadata = { topic: string };
+
+    const returned = customTraceView<Input, Output, Expected, Metadata>(
+      {
+        name: "Typed Trace",
+        slug: "typed-trace",
+      },
+      (props) => {
+        expectTypeOf(props.span.data.input).toEqualTypeOf<Input | undefined>();
+        expectTypeOf(props.span.data.output).toEqualTypeOf<
+          Output | undefined
+        >();
+        expectTypeOf(props.span.data.expected).toEqualTypeOf<
+          Expected | undefined
+        >();
+        expectTypeOf(props.span.data.metadata).toEqualTypeOf<
+          Metadata | undefined
+        >();
+        expectTypeOf(props.trace.spans["span-id"].data.metadata).toEqualTypeOf<
+          Metadata | undefined
+        >();
+        expectTypeOf(props.trace.update).parameter(0).toEqualTypeOf<{
+          target?: "selected" | "root" | { spanId: string };
+          metadata?: Partial<Metadata> & Record<string, unknown>;
+          tags?: string[] | null;
+        }>();
+        return null;
+      },
+    );
+
+    expectTypeOf(returned.kind).toEqualTypeOf<"trace">();
+    expect(returned.kind).toBe("trace");
+  });
+
+  test("preserves dataset view generic prop types", () => {
+    type Input = { prompt: string };
+    type Expected = { answer: string };
+    type Metadata = { difficulty: number };
+
+    const returned = customDatasetView<Input, Expected, Metadata>(
+      {
+        name: "Typed Dataset",
+        slug: "typed-dataset",
+        dataset: { name: "rows" },
+      },
+      (props) => {
+        expectTypeOf(props.input).toEqualTypeOf<Input | undefined>();
+        expectTypeOf(props.expected).toEqualTypeOf<Expected | undefined>();
+        expectTypeOf(props.metadata).toEqualTypeOf<Metadata | undefined>();
+        expectTypeOf(props.tags).toEqualTypeOf<string[] | undefined>();
+        return null;
+      },
+    );
+
+    expectTypeOf(returned.kind).toEqualTypeOf<"dataset">();
+    expect(returned.kind).toBe("dataset");
+  });
+});
diff --git a/js/src/custom-views/exports.ts b/js/src/custom-views/exports.ts
new file mode 100644
index 000000000..44f3b357e
--- /dev/null
+++ b/js/src/custom-views/exports.ts
@@ -0,0 +1 @@
+export { customDatasetView, customTraceView } from "./registry";
diff --git a/js/src/custom-views/registry.ts b/js/src/custom-views/registry.ts
new file mode 100644
index 000000000..78280de97
--- /dev/null
+++ b/js/src/custom-views/registry.ts
@@ -0,0 +1,175 @@
+type SpanFieldName = "input" | "output" | "expected" | "metadata";
+
+type SpanFields<
+  TInput = unknown,
+  TOutput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  input?: TInput;
+  output?: TOutput;
+  expected?: TExpected;
+  metadata?: TMetadata;
+};
+
+type TraceViewSpan<
+  TInput = unknown,
+  TOutput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  id: string;
+  span_id: string;
+  root_span_id: string;
+  parent_span_id?: string | null;
+  span_parents?: string[];
+  data: {
+    input?: TInput;
+    output?: TOutput;
+    expected?: TExpected;
+    metadata?: TMetadata;
+    scores?: Record<string, number>;
+    metrics?: Record<string, number | string>;
+    error?: string;
+    tags?: string[];
+    span_attributes?: Record<string, unknown>;
+    [key: string]: unknown;
+  };
+  children: string[];
+};
+
+type CustomViewUpdateTarget = "selected" | "root" | { spanId: string };
+
+type CustomViewUpdateResult = {
+  transactionId: string | null;
+};
+
+type CustomViewSpanUpdate<
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  target?: CustomViewUpdateTarget;
+  metadata?: Partial<TMetadata> & Record<string, unknown>;
+  tags?: string[] | null;
+};
+
+type TraceViewTrace<
+  TInput = unknown,
+  TOutput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  rootSpanId: string;
+  selectedSpanId: string;
+  spanOrder: string[];
+  spans: Record<string, TraceViewSpan<TInput, TOutput, TExpected, TMetadata>>;
+  fetchSpanFields: (
+    spanIds: string | string[],
+    fields?: SpanFieldName[],
+  ) => Promise<
+    Record<string, SpanFields<TInput, TOutput, TExpected, TMetadata>>
+  >;
+  update: (
+    update: CustomViewSpanUpdate<TMetadata>,
+  ) => Promise<CustomViewUpdateResult>;
+};
+
+type TraceViewUpdate<
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  (field: string, value: unknown): void;
+  (patch: Partial<{ metadata: TMetadata; tags: string[] | null }>): void;
+};
+
+type TraceViewProps<
+  TInput = unknown,
+  TOutput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  trace: TraceViewTrace<TInput, TOutput, TExpected, TMetadata>;
+  span: TraceViewSpan<TInput, TOutput, TExpected, TMetadata>;
+  selectSpan?: (spanId: string) => void;
+  update?: TraceViewUpdate<TMetadata>;
+};
+
+type DatasetViewProps<
+  TInput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = {
+  id: string;
+  input?: TInput;
+  expected?: TExpected;
+  metadata?: TMetadata;
+  tags?: string[];
+};
+
+type Component<Props> = (props: Props) => unknown;
+
+type ProjectRef = string | { id: string } | { name: string };
+type DatasetRef = { id: string } | { name: string };
+
+type CustomTraceViewDefinition = {
+  name: string;
+  slug: string;
+  project?: ProjectRef;
+};
+
+type CustomTraceView<
+  TInput = unknown,
+  TOutput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = CustomTraceViewDefinition & {
+  kind: "trace";
+  component: Component<TraceViewProps<TInput, TOutput, TExpected, TMetadata>>;
+};
+
+type CustomDatasetViewDefinition = {
+  name: string;
+  slug: string;
+  dataset: DatasetRef;
+  project?: ProjectRef;
+};
+
+type CustomDatasetView<
+  TInput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+> = CustomDatasetViewDefinition & {
+  kind: "dataset";
+  component: Component<DatasetViewProps<TInput, TExpected, TMetadata>>;
+};
+
+/**
+ * Defines a trace custom view for discovery by the `bt views` CLI.
+ *
+ * @experimental This API is not yet stabilized and may change across non-major versions.
+ */
+export function customTraceView<
+  TInput = unknown,
+  TOutput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+>(
+  definition: CustomTraceViewDefinition,
+  component: Component<TraceViewProps<TInput, TOutput, TExpected, TMetadata>>,
+): CustomTraceView<TInput, TOutput, TExpected, TMetadata> {
+  return { ...definition, component, kind: "trace" };
+}
+
+/**
+ * Defines a dataset custom view for discovery by the `bt views` CLI.
+ *
+ * @experimental This API is not yet stabilized and may change across non-major versions.
+ */
+export function customDatasetView<
+  TInput = unknown,
+  TExpected = unknown,
+  TMetadata extends Record<string, unknown> = Record<string, unknown>,
+>(
+  definition: CustomDatasetViewDefinition,
+  component: Component<DatasetViewProps<TInput, TExpected, TMetadata>>,
+): CustomDatasetView<TInput, TExpected, TMetadata> {
+  return { ...definition, component, kind: "dataset" };
+}
diff --git a/js/tsup.config.ts b/js/tsup.config.ts
index 9ee12a9d0..2559747de 100644
--- a/js/tsup.config.ts
+++ b/js/tsup.config.ts
@@ -5,6 +5,7 @@ export default defineConfig([
   {
     entry: {
       index: "src/node/index.ts",
+      "custom-views": "src/custom-views/exports.ts",
       "apply-auto-instrumentation":
         "src/node/apply-auto-instrumentation-entry.ts",
       "vitest-evals-reporter": "src/wrappers/vitest-evals/reporter.ts",