diff --git a/.changeset/yellow-crabs-attend.md b/.changeset/yellow-crabs-attend.md
new file mode 100644
index 000000000..c36539820
--- /dev/null
+++ b/.changeset/yellow-crabs-attend.md
@@ -0,0 +1,5 @@
+---
+"braintrust": minor
+---
+
+(feat) Add experiment dataset filters to experiment metadata
diff --git a/js/src/logger.test.ts b/js/src/logger.test.ts
index c4536bb78..21231d8e0 100644
--- a/js/src/logger.test.ts
+++ b/js/src/logger.test.ts
@@ -484,6 +484,156 @@ function mockInitGitMetadata() {
   ).mockResolvedValue([]);
 }
 
+test("init forwards dataset _internal_btql to experiment register", async () => {
+  const state = await _exportsForTestingOnly.simulateLoginForTests();
+
+  try {
+    vi.spyOn(state, "login").mockResolvedValue(state);
+    mockInitGitMetadata();
+
+    const datasetFilter = {
+      filter: [
+        {
+          op: "eq",
+          left: { op: "ident", name: ["metadata", "model"] },
+          right: { op: "literal", value: "gpt-5-mini" },
+        },
+        {
+          op: "isnotnull",
+          expr: { op: "ident", name: ["expected"] },
+        },
+      ],
+    };
+
+    let experimentRegisterBody: unknown;
+    vi.spyOn(state.appConn(), "post_json")
+      .mockResolvedValueOnce({
+        project: {
+          id: "00000000-0000-0000-0000-000000000001",
+          name: "test-project",
+        },
+        dataset: {
+          id: "00000000-0000-0000-0000-000000000002",
+          name: "test-dataset",
+        },
+      })
+      .mockImplementationOnce(async (_path, body) => {
+        experimentRegisterBody = body;
+        return {
+          project: {
+            id: "00000000-0000-0000-0000-000000000001",
+            name: "test-project",
+          },
+          experiment: {
+            id: "00000000-0000-0000-0000-000000000003",
+            project_id: "00000000-0000-0000-0000-000000000001",
+            name: "test-experiment",
+            public: false,
+          },
+        };
+      });
+
+    const dataset = initDataset({
+      project: "test-project",
+      dataset: "test-dataset",
+      version: "123",
+      _internal_btql: datasetFilter,
+      state,
+    });
+
+    const experiment = init({
+      project: "test-project",
+      experiment: "test-experiment",
+      dataset,
+      setCurrent: false,
+      state,
+    });
+
+    await experiment.id;
+
+    expect(experimentRegisterBody).toEqual(
+      expect.objectContaining({
+        internal_metadata: {
+          dataset_filter: datasetFilter,
+        },
+      }),
+    );
+  } finally {
+    _exportsForTestingOnly.simulateLogoutForTests();
+    vi.restoreAllMocks();
+  }
+});
+
+test("dataset fetch forwards _internal_btql filter arrays to btql", async () => {
+  const state = await _exportsForTestingOnly.simulateLoginForTests();
+
+  try {
+    vi.spyOn(state, "login").mockResolvedValue(state);
+
+    const datasetFilter = {
+      filter: [
+        {
+          op: "eq",
+          left: { op: "ident", name: ["metadata", "model"] },
+          right: { op: "literal", value: "gpt-5-mini" },
+        },
+        {
+          op: "isnotnull",
+          expr: { op: "ident", name: ["expected"] },
+        },
+      ],
+      limit: 5,
+    };
+
+    vi.spyOn(state.appConn(), "post_json").mockResolvedValue({
+      project: {
+        id: "00000000-0000-0000-0000-000000000001",
+        name: "test-project",
+      },
+      dataset: {
+        id: "00000000-0000-0000-0000-000000000002",
+        name: "test-dataset",
+      },
+    });
+
+    let btqlBody: unknown;
+    vi.spyOn(state.apiConn(), "post").mockImplementation(
+      async (_path, body) => {
+        btqlBody = body;
+        return new Response(JSON.stringify({ data: [] }), {
+          status: 200,
+          headers: { "Content-Type": "application/json" },
+        });
+      },
+    );
+
+    const dataset = initDataset({
+      project: "test-project",
+      dataset: "test-dataset",
+      _internal_btql: datasetFilter,
+      state,
+    });
+
+    const rows: unknown[] = [];
+    for await (const row of dataset) {
+      rows.push(row);
+    }
+
+    expect(rows).toEqual([]);
+    expect(btqlBody).toEqual(
+      expect.objectContaining({
+        query: expect.objectContaining({
+          filter: datasetFilter.filter,
+          limit: 5,
+        }),
+      }),
+    );
+  } finally {
+    _exportsForTestingOnly.simulateLogoutForTests();
+    vi.restoreAllMocks();
+  }
+});
+
 test("initDataset prefers version over environment in eval data", async () => {
   const state = await _exportsForTestingOnly.simulateLoginForTests();
   vi.spyOn(state, "login").mockResolvedValue(state);
@@ -948,7 +1098,6 @@ test("init keeps plain dataset refs attached to the experiment", async () => {
   });
 
   await experiment.id;
-
   expect(experiment.dataset).toMatchObject({
     id: "00000000-0000-0000-0000-000000000002",
   });
diff --git a/js/src/logger.ts b/js/src/logger.ts
index ef8ed3a65..81da807fe 100644
--- a/js/src/logger.ts
+++ b/js/src/logger.ts
@@ -3472,6 +3472,7 @@ export type InitOptions<IsOpen extends boolean> = FullLoginOptions & {
   experiment?: string;
   description?: string;
   dataset?: AnyDataset | DatasetRef;
+  _internal_btql?: Record<string, unknown>;
   parameters?: ParametersRef | RemoteEvalParameters<boolean, boolean>;
   update?: boolean;
   baseExperiment?: string;
@@ -3490,6 +3491,32 @@ export type FullInitOptions<IsOpen extends boolean> = {
   project?: string;
 } & InitOptions<IsOpen>;
 
+function getExperimentDatasetFilter({
+  dataset,
+  _internal_btql,
+}: {
+  dataset?: AnyDataset | DatasetRef;
+  _internal_btql?: Record<string, unknown>;
+}): Record<string, unknown> | undefined {
+  if (_internal_btql !== undefined) {
+    return _internal_btql;
+  }
+
+  if (!(dataset instanceof Dataset)) {
+    return undefined;
+  }
+
+  const datasetFilter = Reflect.get(dataset, "_internal_btql");
+  return isObject(datasetFilter) ? datasetFilter : undefined;
+}
+
+function getInternalBtqlLimit(
+  internalBtql?: Record<string, unknown>,
+): number | undefined {
+  const limit = internalBtql?.["limit"];
+  return typeof limit === "number" ? limit : undefined;
+}
+
 type InitializedExperiment<IsOpen extends boolean | undefined> =
   IsOpen extends true ? ReadonlyExperiment : Experiment;
 
@@ -3556,6 +3583,7 @@ export function init<IsOpen extends boolean = false>(
     experiment,
     description,
     dataset,
+    _internal_btql,
     parameters,
     baseExperiment,
     isPublic,
@@ -3697,6 +3725,16 @@ export function init<IsOpen extends boolean = false>(
         }
       }
 
+      const datasetFilter = getExperimentDatasetFilter({
+        dataset,
+        _internal_btql,
+      });
+      if (datasetFilter !== undefined) {
+        args["internal_metadata"] = {
+          dataset_filter: datasetFilter,
+        };
+      }
+
       if (parameters !== undefined) {
         if (RemoteEvalParameters.isParameters(parameters)) {
           args["parameters_id"] = parameters.id;
@@ -6046,9 +6084,7 @@ export class ObjectFetcher<RecordType> implements AsyncIterable<
     const state = await this.getState();
     const objectId = await this.id;
     const batchLimit = batchSize ?? DEFAULT_FETCH_BATCH_SIZE;
-    const internalLimit = (
-      this._internal_btql as { limit?: number } | undefined
-    )?.limit;
+    const internalLimit = getInternalBtqlLimit(this._internal_btql);
     const limit =
       batchSize !== undefined ? batchSize : (internalLimit ?? batchLimit);
     const internalBtqlWithoutReservedQueryKeys = Object.fromEntries(