diff --git a/.github/workflows/campaign-generator.lock.yml b/.github/workflows/campaign-generator.lock.yml
index 8994565ea5..330a000343 100644
--- a/.github/workflows/campaign-generator.lock.yml
+++ b/.github/workflows/campaign-generator.lock.yml
@@ -525,10 +525,13 @@ jobs:
                   "maxLength": 128
                 },
                 "issue_number": {
-                  "required": true,
-                  "positiveInteger": true
+                  "optionalPositiveInteger": true
+                },
+                "pull_number": {
+                  "optionalPositiveInteger": true
                 }
-              }
+              },
+              "customValidation": "requiresOneOf:issue_number,pull_number"
             },
             "create_project": {
               "defaultMax": 1,
diff --git a/.github/workflows/issue-monster.lock.yml b/.github/workflows/issue-monster.lock.yml
index dac2b5c813..7dc7dcc24c 100644
--- a/.github/workflows/issue-monster.lock.yml
+++ b/.github/workflows/issue-monster.lock.yml
@@ -342,10 +342,13 @@ jobs:
                   "maxLength": 128
                 },
                 "issue_number": {
-                  "required": true,
-                  "positiveInteger": true
+                  "optionalPositiveInteger": true
+                },
+                "pull_number": {
+                  "optionalPositiveInteger": true
                 }
-              }
+              },
+              "customValidation": "requiresOneOf:issue_number,pull_number"
             },
             "missing_tool": {
               "defaultMax": 20,
diff --git a/.github/workflows/workflow-generator.lock.yml b/.github/workflows/workflow-generator.lock.yml
index 087fc36f6f..be74cdf4a4 100644
--- a/.github/workflows/workflow-generator.lock.yml
+++ b/.github/workflows/workflow-generator.lock.yml
@@ -360,10 +360,13 @@ jobs:
                   "maxLength": 128
                 },
                 "issue_number": {
-                  "required": true,
-                  "positiveInteger": true
+                  "optionalPositiveInteger": true
+                },
+                "pull_number": {
+                  "optionalPositiveInteger": true
                 }
-              }
+              },
+              "customValidation": "requiresOneOf:issue_number,pull_number"
             },
             "missing_tool": {
               "defaultMax": 20,
diff --git a/actions/setup/js/safe_output_type_validator.test.cjs b/actions/setup/js/safe_output_type_validator.test.cjs
index f984515282..e723036aff 100644
--- a/actions/setup/js/safe_output_type_validator.test.cjs
+++ b/actions/setup/js/safe_output_type_validator.test.cjs
@@ -46,6 +46,15 @@ const SAMPLE_VALIDATION_CONFIG = {
       issue_number: { issueOrPRNumber: true },
     },
   },
+  assign_to_agent: {
+    defaultMax: 1,
+    customValidation: "requiresOneOf:issue_number,pull_number",
+    fields: {
+      issue_number: { optionalPositiveInteger: true },
+      pull_number: { optionalPositiveInteger: true },
+      agent: { type: "string", sanitize: true, maxLength: 128 },
+    },
+  },
   create_pull_request_review_comment: {
     defaultMax: 1,
     customValidation: "startLineLessOrEqualLine",
@@ -356,6 +365,33 @@ describe("safe_output_type_validator", () => {
       expect(result.isValid).toBe(false);
       expect(result.error).toContain("requires at least one of");
     });
+
+    it("should pass for assign_to_agent with issue_number", async () => {
+      const { validateItem } = await import("./safe_output_type_validator.cjs");
+
+      const result = validateItem({ type: "assign_to_agent", issue_number: 123 }, "assign_to_agent", 1);
+
+      expect(result.isValid).toBe(true);
+    });
+
+    it("should pass for assign_to_agent with pull_number", async () => {
+      const { validateItem } = await import("./safe_output_type_validator.cjs");
+
+      const result = validateItem({ type: "assign_to_agent", pull_number: 456 }, "assign_to_agent", 1);
+
+      expect(result.isValid).toBe(true);
+    });
+
+    it("should fail for assign_to_agent without issue_number or pull_number", async () => {
+      const { validateItem } = await import("./safe_output_type_validator.cjs");
+
+      const result = validateItem({ type: "assign_to_agent", agent: "copilot" }, "assign_to_agent", 1);
+
+      expect(result.isValid).toBe(false);
+      expect(result.error).toContain("requires at least one of");
+      expect(result.error).toContain("issue_number");
+      expect(result.error).toContain("pull_number");
+    });
   });
 
   describe("custom validation: startLineLessOrEqualLine", () => {
diff --git a/pkg/workflow/safe_output_validation_config.go b/pkg/workflow/safe_output_validation_config.go
index 0ecb965379..a7cd677f57 100644
--- a/pkg/workflow/safe_output_validation_config.go
+++ b/pkg/workflow/safe_output_validation_config.go
@@ -98,9 +98,11 @@ var ValidationConfig = map[string]TypeValidationConfig{
 		},
 	},
 	"assign_to_agent": {
-		DefaultMax: 1,
+		DefaultMax:       1,
+		CustomValidation: "requiresOneOf:issue_number,pull_number",
 		Fields: map[string]FieldValidation{
-			"issue_number": {Required: true, PositiveInteger: true},
+			"issue_number": {OptionalPositiveInteger: true},
+			"pull_number":  {OptionalPositiveInteger: true},
 			"agent":        {Type: "string", Sanitize: true, MaxLength: 128},
 		},
 	},
diff --git a/pkg/workflow/safe_output_validation_config_test.go b/pkg/workflow/safe_output_validation_config_test.go
index 4335116eb6..d8c9c971fb 100644
--- a/pkg/workflow/safe_output_validation_config_test.go
+++ b/pkg/workflow/safe_output_validation_config_test.go
@@ -232,10 +232,11 @@ func TestFieldValidationMarshaling(t *testing.T) {
 func TestValidationConfigConsistency(t *testing.T) {
 	// Verify that all types with customValidation have valid validation rules
 	validCustomValidations := map[string]bool{
-		"requiresOneOf:status,title,body": true,
-		"requiresOneOf:title,body":        true,
-		"startLineLessOrEqualLine":        true,
-		"parentAndSubDifferent":           true,
+		"requiresOneOf:status,title,body":        true,
+		"requiresOneOf:title,body":               true,
+		"requiresOneOf:issue_number,pull_number": true,
+		"startLineLessOrEqualLine":               true,
+		"parentAndSubDifferent":                  true,
 	}
 
 	for typeName, config := range ValidationConfig {