diff --git a/ts/packages/benchmarks/src/translationBench/synthesizer/generationCandidate.ts b/ts/packages/benchmarks/src/translationBench/synthesizer/generationCandidate.ts
index d96ae1589..ffdfc807e 100644
--- a/ts/packages/benchmarks/src/translationBench/synthesizer/generationCandidate.ts
+++ b/ts/packages/benchmarks/src/translationBench/synthesizer/generationCandidate.ts
@@ -289,13 +289,18 @@ function stripEmptyGoldPlaceholdersFromActions(
     actions: TranslationBenchBenchmarkAction[],
 ): TranslationBenchBenchmarkAction[] {
     return actions.map((action) => {
+        if (action.parameters === undefined) {
+            return action;
+        }
         const { parameters } = stripEmptyGoldPlaceholders(action.parameters);
         if (parameters === action.parameters) {
             return action;
         }
         if (parameters === undefined) {
-            const { parameters: _drop, ...rest } = action;
-            return rest;
+            // Keep parameters:{} when nested empties strip to nothing. Schemas
+            // like code.getSelection / desktop.ListThemes require the key
+            // (empty object type); dropping it fails validateAction.
+            return { ...action, parameters: {} };
         }
         return { ...action, parameters };
     });
diff --git a/ts/packages/benchmarks/test/translationBench.keepEmptyParams.spec.ts b/ts/packages/benchmarks/test/translationBench.keepEmptyParams.spec.ts
new file mode 100644
index 000000000..2323993b2
--- /dev/null
+++ b/ts/packages/benchmarks/test/translationBench.keepEmptyParams.spec.ts
@@ -0,0 +1,164 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+import { describe, expect, it } from "@jest/globals";
+
+import { stripEmptyGoldPlaceholdersFromCandidate } from "../src/translationBench/synthesizer/generationCandidate.js";
+
+describe("keep empty parameters after gold placeholder strip", () => {
+    it("keeps parameters:{} when nested empties strip to nothing", () => {
+        const stripped = stripEmptyGoldPlaceholdersFromCandidate({
+            seed: {
+                utterance: "get the current selection",
+                expectedActions: [
+                    {
+                        schemaName: "code",
+                        actionName: "getSelection",
+                        parameters: {
+                            unused: "",
+                            nested: { flag: null },
+                        },
+                    },
+                ],
+                order: "strict",
+            },
+            genCases: [
+                {
+                    id: "pos-1",
+                    role: "positive",
+                    utterance: "what text is selected",
+                    expectedActions: [
+                        {
+                            schemaName: "code",
+                            actionName: "getSelection",
+                            parameters: { unused: "   " },
+                        },
+                    ],
+                    order: "strict",
+                    dimensions: { variation: "paraphrase" },
+                },
+                {
+                    id: "neg-1",
+                    role: "negative",
+                    utterance: "leave my editor alone",
+                    expectedActions: [],
+                    order: "strict",
+                    dimensions: { negativeKind: "pure_refusal" },
+                },
+            ],
+        });
+
+        expect(stripped.seed.expectedActions[0]).toEqual({
+            schemaName: "code",
+            actionName: "getSelection",
+            parameters: {},
+        });
+        expect(stripped.genCases[0]!.expectedActions[0]).toEqual({
+            schemaName: "code",
+            actionName: "getSelection",
+            parameters: {},
+        });
+        // Negatives are not rewritten by the strip helper.
+        expect(stripped.genCases[1]!.expectedActions).toEqual([]);
+    });
+
+    it("does not invent parameters when gold omitted the key", () => {
+        const stripped = stripEmptyGoldPlaceholdersFromCandidate({
+            seed: {
+                utterance: "list themes",
+                expectedActions: [
+                    {
+                        schemaName: "desktop",
+                        actionName: "ListThemes",
+                    },
+                ],
+                order: "strict",
+            },
+            genCases: [
+                {
+                    id: "pos-1",
+                    role: "positive",
+                    utterance: "show desktop themes",
+                    expectedActions: [
+                        {
+                            schemaName: "desktop",
+                            actionName: "ListThemes",
+                        },
+                    ],
+                    order: "strict",
+                    dimensions: { variation: "paraphrase" },
+                },
+                {
+                    id: "neg-1",
+                    role: "negative",
+                    utterance: "do not list themes",
+                    expectedActions: [],
+                    order: "strict",
+                    dimensions: { negativeKind: "pure_refusal" },
+                },
+            ],
+        });
+
+        expect(stripped.seed.expectedActions[0]).toEqual({
+            schemaName: "desktop",
+            actionName: "ListThemes",
+        });
+        expect(stripped.seed.expectedActions[0]).not.toHaveProperty(
+            "parameters",
+        );
+    });
+
+    it("still strips empty nested fields while keeping non-empty siblings", () => {
+        const stripped = stripEmptyGoldPlaceholdersFromCandidate({
+            seed: {
+                utterance: "open apple.com",
+                expectedActions: [
+                    {
+                        schemaName: "browser",
+                        actionName: "openWebPage",
+                        parameters: {
+                            site: "apple.com",
+                            tab: "",
+                            extras: {},
+                        },
+                    },
+                ],
+                order: "strict",
+            },
+            genCases: [
+                {
+                    id: "pos-1",
+                    role: "positive",
+                    utterance: "navigate to apple.com",
+                    expectedActions: [
+                        {
+                            schemaName: "browser",
+                            actionName: "openWebPage",
+                            parameters: {
+                                site: "apple.com",
+                                tab: null,
+                            },
+                        },
+                    ],
+                    order: "strict",
+                    dimensions: { variation: "paraphrase" },
+                },
+                {
+                    id: "neg-1",
+                    role: "negative",
+                    utterance: "leave browser alone",
+                    expectedActions: [],
+                    order: "strict",
+                    dimensions: { negativeKind: "pure_refusal" },
+                },
+            ],
+        });
+
+        expect(stripped.seed.expectedActions[0]!.parameters).toEqual({
+            site: "apple.com",
+        });
+        expect(stripped.genCases[0]!.expectedActions[0]!.parameters).toEqual({
+            site: "apple.com",
+        });
+    });
+});