3 files changed, 61 insertions, 2 deletions
diff --git a/src/bun.js/builtins/cpp/ReadableStreamInternalsBuiltins.cpp b/src/bun.js/builtins/cpp/ReadableStreamInternalsBuiltins.cpp
index 8f3caa3a2..a2b13e770 100644
--- a/src/bun.js/builtins/cpp/ReadableStreamInternalsBuiltins.cpp
+++ b/src/bun.js/builtins/cpp/ReadableStreamInternalsBuiltins.cpp
@@ -751,7 +751,7 @@ const char* const s_readableStreamInternalsPipeToFinalizeCode =
 const JSC::ConstructAbility s_readableStreamInternalsReadableStreamTeeCodeConstructAbility = JSC::ConstructAbility::CannotConstruct;
 const JSC::ConstructorKind s_readableStreamInternalsReadableStreamTeeCodeConstructorKind = JSC::ConstructorKind::None;
 const JSC::ImplementationVisibility s_readableStreamInternalsReadableStreamTeeCodeImplementationVisibility = JSC::ImplementationVisibility::Public;
-const int s_readableStreamInternalsReadableStreamTeeCodeLength = 1689;
+const int s_readableStreamInternalsReadableStreamTeeCodeLength = 1839;
 static const JSC::Intrinsic s_readableStreamInternalsReadableStreamTeeCodeIntrinsic = JSC::NoIntrinsic;
 const char* const s_readableStreamInternalsReadableStreamTeeCode =
     "(function (stream, shouldClone) {\n" \
@@ -760,6 +760,12 @@ const char* const s_readableStreamInternalsReadableStreamTeeCode =
     "  @assert(@isReadableStream(stream));\n" \
     "  @assert(typeof shouldClone === \"boolean\");\n" \
     "\n" \
+    "  var start_ = @getByIdDirectPrivate(stream, \"start\");\n" \
+    "  if (start_) {\n" \
+    "      @putByIdDirectPrivate(stream, \"start\", @undefined);\n" \
+    "      start_();\n" \
+    "  }\n" \
+    "\n" \
     "  const reader = new @ReadableStreamDefaultReader(stream);\n" \
     "\n" \
     "  const teeState = {\n" \
diff --git a/src/bun.js/builtins/js/ReadableStreamInternals.js b/src/bun.js/builtins/js/ReadableStreamInternals.js
index e59372d24..ca1edaee8 100644
--- a/src/bun.js/builtins/js/ReadableStreamInternals.js
+++ b/src/bun.js/builtins/js/ReadableStreamInternals.js
@@ -609,6 +609,12 @@ function readableStreamTee(stream, shouldClone) {
   @assert(@isReadableStream(stream));
   @assert(typeof shouldClone === "boolean");
 
+  var start_ = @getByIdDirectPrivate(stream, "start");
+  if (start_) {
+      @putByIdDirectPrivate(stream, "start", @undefined);
+      start_();
+  }
+
   const reader = new @ReadableStreamDefaultReader(stream);
 
   const teeState = {
diff --git a/test/bun.js/streams.test.js b/test/bun.js/streams.test.js
index 8ca424495..6488eb37f 100644
--- a/test/bun.js/streams.test.js
+++ b/test/bun.js/streams.test.js
@@ -4,7 +4,7 @@ import {
   readableStreamToArray,
   readableStreamToText,
 } from "bun";
-import { expect, it, beforeEach, afterEach } from "bun:test";
+import { expect, it, beforeEach, afterEach, describe } from "bun:test";
 import { mkfifo } from "mkfifo";
 import { unlinkSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
@@ -14,6 +14,53 @@ new Uint8Array();
 beforeEach(() => gc());
 afterEach(() => gc());
 
+describe("ReadableStream.prototype.tee", async () => {
+  it("class", () => {
+    const [a, b] = new ReadableStream().tee();
+    expect(a instanceof ReadableStream).toBe(true);
+    expect(b instanceof ReadableStream).toBe(true);
+  });
+
+  describe("default stream", () => {
+    it("works", async () => {
+      var [a, b] = new ReadableStream({
+        start(controller) {
+          controller.enqueue("a");
+          controller.enqueue("b");
+          controller.enqueue("c");
+          controller.close();
+        },
+      }).tee();
+
+      expect(await readableStreamToText(a)).toBe("abc");
+      expect(await readableStreamToText(b)).toBe("abc");
+    });
+  });
+
+  describe("direct stream", () => {
+    it("works", async () => {
+      try {
+        var [a, b] = new ReadableStream({
+          pull(controller) {
+            controller.write("a");
+            controller.write("b");
+            controller.write("c");
+            controller.close();
+          },
+          type: "direct",
+        }).tee();
+
+        expect(await readableStreamToText(a)).toBe("abc");
+        expect(await readableStreamToText(b)).toBe("abc");
+      } catch (e) {
+        console.log(e.message);
+        console.log(e.stack);
+        throw e;
+      }
+    });
+  });
+});
+
 it("ReadableStream.prototype[Symbol.asyncIterator]", async () => {
   const stream = new ReadableStream({
     start(controller) {