diff --git a/test/js-api/exception/basic.tentative.any.js b/test/js-api/exception/basic.tentative.any.js
new file mode 100644
index 00000000..c57c79cc
--- /dev/null
+++ b/test/js-api/exception/basic.tentative.any.js
@@ -0,0 +1,120 @@
+// META: global=window,dedicatedworker,jsshell,shadowrealm
+// META: script=/wasm/jsapi/wasm-module-builder.js
+
+function assert_throws_wasm(fn, message) {
+  try {
+    fn();
+    assert_not_reached(`expected to throw with ${message}`);
+  } catch (e) {
+    assert_true(e instanceof WebAssembly.Exception, `Error should be a WebAssembly.Exception with ${message}`);
+  }
+}
+
+promise_test(async () => {
+  const kSig_v_r = makeSig([kWasmExternRef], []);
+  const builder = new WasmModuleBuilder();
+  const tagIndex = builder.addTag(kSig_v_r);
+  builder.addFunction("throw_param", kSig_v_r)
+    .addBody([
+      kExprLocalGet, 0,
+      kExprThrow, tagIndex,
+    ])
+    .exportFunc();
+  const buffer = builder.toBuffer();
+  const {instance} = await WebAssembly.instantiate(buffer, {});
+  const values = [
+    undefined,
+    null,
+    true,
+    false,
+    "test",
+    Symbol(),
+    0,
+    1,
+    4.2,
+    NaN,
+    Infinity,
+    {},
+    () => {},
+  ];
+  for (const v of values) {
+    assert_throws_wasm(() => instance.exports.throw_param(v), String(v));
+  }
+}, "Wasm function throws argument");
+
+promise_test(async () => {
+  const builder = new WasmModuleBuilder();
+  const tagIndex = builder.addTag(kSig_v_a);
+  builder.addFunction("throw_null", kSig_v_v)
+    .addBody([
+      kExprRefNull, kAnyFuncCode,
+      kExprThrow, tagIndex,
+    ])
+    .exportFunc();
+  const buffer = builder.toBuffer();
+  const {instance} = await WebAssembly.instantiate(buffer, {});
+  assert_throws_wasm(() => instance.exports.throw_null());
+}, "Wasm function throws null");
+
+promise_test(async () => {
+  const builder = new WasmModuleBuilder();
+  const tagIndex = builder.addTag(kSig_v_i);
+  builder.addFunction("throw_int", kSig_v_v)
+    .addBody([
+      ...wasmI32Const(7),
+      kExprThrow, tagIndex,
+    ])
+    .exportFunc();
+  const buffer = builder.toBuffer();
+  const {instance} = await WebAssembly.instantiate(buffer, {});
+  assert_throws_wasm(() => instance.exports.throw_int());
+}, "Wasm function throws integer");
+
+promise_test(async () => {
+  const builder = new WasmModuleBuilder();
+  const fnIndex = builder.addImport("module", "fn", kSig_v_v);
+  const tagIndex= builder.addTag(kSig_v_r);
+  builder.addFunction("catch_exception", kSig_r_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, fnIndex,
+      kExprCatch, tagIndex,
+        kExprReturn,
+      kExprEnd,
+      kExprRefNull, kExternRefCode,
+    ])
+    .exportFunc();
+
+  const buffer = builder.toBuffer();
+
+  const error = new Error();
+  const fn = () => { throw error };
+  const {instance} = await WebAssembly.instantiate(buffer, {
+    module: { fn }
+  });
+  assert_throws_exactly(error, () => instance.exports.catch_exception());
+}, "Imported JS function throws");
+
+promise_test(async () => {
+  const builder = new WasmModuleBuilder();
+  const fnIndex = builder.addImport("module", "fn", kSig_v_v);
+  builder.addFunction("catch_and_rethrow", kSig_r_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, fnIndex,
+      kExprCatchAll,
+        kExprRethrow, 0x00,
+      kExprEnd,
+      kExprRefNull, kExternRefCode,
+    ])
+    .exportFunc();
+
+  const buffer = builder.toBuffer();
+
+  const error = new Error();
+  const fn = () => { throw error };
+  const {instance} = await WebAssembly.instantiate(buffer, {
+    module: { fn }
+  });
+  assert_throws_exactly(error, () => instance.exports.catch_and_rethrow());
+}, "Imported JS function throws, Wasm catches and rethrows");
diff --git a/test/js-api/exception/identity.tentative.any.js b/test/js-api/exception/identity.tentative.any.js
new file mode 100644
index 00000000..36651c7d
--- /dev/null
+++ b/test/js-api/exception/identity.tentative.any.js
@@ -0,0 +1,170 @@
+// META: global=window,dedicatedworker,jsshell,shadowrealm
+// META: script=/wasm/jsapi/assertions.js
+// META: script=/wasm/jsapi/wasm-module-builder.js
+
+test(() => {
+  const builder = new WasmModuleBuilder();
+
+  // Tag defined in JavaScript and imported into Wasm
+  const jsTag = new WebAssembly.Tag({ parameters: ["i32"] });
+  const jsTagIndex = builder.addImportedTag("module", "jsTag", kSig_v_i);
+  const jsTagExn = new WebAssembly.Exception(jsTag, [42]);
+  const jsTagExnSamePayload = new WebAssembly.Exception(jsTag, [42]);
+  const jsTagExnDiffPayload = new WebAssembly.Exception(jsTag, [53]);
+  const throwJSTagExnIndex = builder.addImport("module", "throwJSTagExn", kSig_v_v);
+
+  // Tag defined in Wasm and exported to JS
+  const wasmTagIndex = builder.addTag(kSig_v_i);
+  builder.addExportOfKind("wasmTag", kExternalTag, wasmTagIndex);
+  const throwWasmTagExnIndex = builder.addImport("module", "throwWasmTagExn", kSig_v_v);
+  // Will be assigned after an instance is created
+  let wasmTagExn = null;
+  let wasmTagExnSamePayload = null;
+  let wasmTagExnDiffPayload = null;
+
+  const imports = {
+    module: {
+      throwJSTagExn: function() { throw jsTagExn; },
+      throwWasmTagExn: function() { throw wasmTagExn; },
+      jsTag: jsTag
+    }
+  };
+
+  // Call a JS function that throws an exception using a JS-defined tag, catches
+  // it with a 'catch' instruction, and rethrows it.
+  builder
+    .addFunction("catch_js_tag_rethrow", kSig_v_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, throwJSTagExnIndex,
+      kExprCatch, jsTagIndex,
+        kExprDrop,
+        kExprRethrow, 0x00,
+      kExprEnd
+    ])
+    .exportFunc();
+
+  // Call a JS function that throws an exception using a Wasm-defined tag,
+  // catches it with a 'catch' instruction, and rethrows it.
+  builder
+    .addFunction("catch_wasm_tag_rethrow", kSig_v_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, throwWasmTagExnIndex,
+      kExprCatch, wasmTagIndex,
+        kExprDrop,
+        kExprRethrow, 0x00,
+      kExprEnd
+    ])
+    .exportFunc();
+
+  // Call a JS function that throws an exception using a JS-defined tag, catches
+  // it with a 'catch_all' instruction, and rethrows it.
+  builder
+    .addFunction("catch_all_js_tag_rethrow", kSig_v_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, throwJSTagExnIndex,
+      kExprCatchAll,
+        kExprRethrow, 0x00,
+      kExprEnd
+    ])
+    .exportFunc();
+
+  // Call a JS function that throws an exception using a Wasm-defined tag,
+  // catches it with a 'catch_all' instruction, and rethrows it.
+  builder
+    .addFunction("catch_all_wasm_tag_rethrow", kSig_v_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, throwWasmTagExnIndex,
+      kExprCatchAll,
+        kExprRethrow, 0x00,
+      kExprEnd
+    ])
+    .exportFunc();
+
+  // Call a JS function that throws an exception, catches it with a 'catch'
+  // instruction, and returns its i32 payload.
+  builder
+    .addFunction("catch_js_tag_return_payload", kSig_i_v)
+    .addBody([
+      kExprTry, kWasmI32,
+        kExprCallFunction, throwJSTagExnIndex,
+        kExprI32Const, 0x00,
+      kExprCatch, jsTagIndex,
+        kExprReturn,
+      kExprEnd
+    ])
+    .exportFunc();
+
+  // Call a JS function that throws an exception, catches it with a 'catch'
+  // instruction, and throws a new exception using that payload.
+  builder
+    .addFunction("catch_js_tag_throw_payload", kSig_v_v)
+    .addBody([
+      kExprTry, kWasmVoid,
+        kExprCallFunction, throwJSTagExnIndex,
+      kExprCatch, jsTagIndex,
+        kExprThrow, jsTagIndex,
+      kExprEnd
+    ])
+    .exportFunc();
+
+  const buffer = builder.toBuffer();
+
+  WebAssembly.instantiate(buffer, imports).then(result => {
+    // The exception object's identity should be preserved across 'rethrow's in
+    // Wasm code. Do tests with a tag defined in JS.
+    try {
+      result.instance.exports.catch_js_tag_rethrow();
+    } catch (e) {
+      assert_equals(e, jsTagExn);
+      // Even if they have the same payload, they are different objects, so they
+      // shouldn't compare equal.
+      assert_not_equals(e, jsTagExnSamePayload);
+      assert_not_equals(e, jsTagExnDiffPayload);
+    }
+    try {
+      result.instance.exports.catch_all_js_tag_rethrow();
+    } catch (e) {
+      assert_equals(e, jsTagExn);
+      assert_not_equals(e, jsTagExnSamePayload);
+      assert_not_equals(e, jsTagExnDiffPayload);
+    }
+
+    // Do the same tests with a tag defined in Wasm.
+    const wasmTag = result.instance.exports.wasmTag;
+    wasmTagExn = new WebAssembly.Exception(wasmTag, [42]);
+    wasmTagExnSamePayload = new WebAssembly.Exception(wasmTag, [42]);
+    wasmTagExnDiffPayload = new WebAssembly.Exception(wasmTag, [53]);
+    try {
+      result.instance.exports.catch_wasm_tag_rethrow();
+    } catch (e) {
+      assert_equals(e, wasmTagExn);
+      assert_not_equals(e, wasmTagExnSamePayload);
+      assert_not_equals(e, wasmTagExnDiffPayload);
+    }
+    try {
+      result.instance.exports.catch_all_wasm_tag_rethrow();
+    } catch (e) {
+      assert_equals(e, wasmTagExn);
+      assert_not_equals(e, wasmTagExnSamePayload);
+      assert_not_equals(e, wasmTagExnDiffPayload);
+    }
+
+    // This function catches the exception and returns its i32 payload, which
+    // should match the original payload.
+    assert_equals(result.instance.exports.catch_js_tag_return_payload(), 42);
+
+    // This function catches the exception and throws a new exception using the
+    // its payload. Even if the payload is reused, the exception objects should
+    // not compare equal.
+    try {
+      result.instance.exports.catch_js_tag_throw_payload();
+    } catch (e) {
+      assert_equals(e.getArg(jsTag, 0), 42);
+      assert_not_equals(e, jsTagExn);
+    }
+  });
+}, "Identity check");