fix: Empty assignees array should clear assignees (#2600)

* fix: Empty assignees array should clear assignees
advancedresearcharray · Jun 4, 2026 · Jun 5, 2026 · Jun 3, 2026 · Jun 3, 2026 · Jun 3, 2026
commit 33849e98eb4797107d033b6d29ffbd5f6d9e8a2b
diff --git a/pkg/github/issues.go b/pkg/github/issues.go
@@ -1972,12 +1972,16 @@ Options are:
 			if err != nil {
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
+			assigneesValue, assigneesProvided := args["assignees"]
+			assigneesProvided = assigneesProvided && assigneesValue != nil
 
 			// Get labels
 			labels, err := OptionalStringArrayParam(args, "labels")
 			if err != nil {
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
+			labelsValue, labelsProvided := args["labels"]
+			labelsProvided = labelsProvided && labelsValue != nil
 
 			// Get optional milestone
 			milestone, err := OptionalIntParam(args, "milestone")
@@ -2049,7 +2053,10 @@ Options are:
 				if err != nil {
 					return utils.NewToolResultError(err.Error()), nil, nil
 				}
-				result, err := UpdateIssue(ctx, client, gqlClient, owner, repo, issueNumber, title, body, assignees, labels, milestoneNum, issueType, issueFieldValues, fieldIDsToDelete, state, stateReason, duplicateOf)
+				result, err := UpdateIssue(ctx, client, gqlClient, owner, repo, issueNumber, title, body, assignees, labels, milestoneNum, issueType, issueFieldValues, fieldIDsToDelete, state, stateReason, duplicateOf, UpdateIssueOptions{
+					AssigneesProvided: assigneesProvided,
+					LabelsProvided:    labelsProvided,
+				})
 				return result, nil, err
 			default:
 				return utils.NewToolResultError("invalid method, must be either 'create' or 'update'"), nil, nil
@@ -2204,12 +2211,16 @@ Options are:
 			if err != nil {
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
+			assigneesValue, assigneesProvided := args["assignees"]
+			assigneesProvided = assigneesProvided && assigneesValue != nil
 
 			// Get labels
 			labels, err := OptionalStringArrayParam(args, "labels")
 			if err != nil {
 				return utils.NewToolResultError(err.Error()), nil, nil
 			}
+			labelsValue, labelsProvided := args["labels"]
+			labelsProvided = labelsProvided && labelsValue != nil
 
 			// Get optional milestone
 			milestone, err := OptionalIntParam(args, "milestone")
@@ -2266,7 +2277,10 @@ Options are:
 				if err != nil {
 					return utils.NewToolResultError(err.Error()), nil, nil
 				}
-				result, err := UpdateIssue(ctx, client, gqlClient, owner, repo, issueNumber, title, body, assignees, labels, milestoneNum, issueType, nil, nil, state, stateReason, duplicateOf)
+				result, err := UpdateIssue(ctx, client, gqlClient, owner, repo, issueNumber, title, body, assignees, labels, milestoneNum, issueType, nil, nil, state, stateReason, duplicateOf, UpdateIssueOptions{
+					AssigneesProvided: assigneesProvided,
+					LabelsProvided:    labelsProvided,
+				})
 				return result, nil, err
 			default:
 				return utils.NewToolResultError("invalid method, must be either 'create' or 'update'"), nil, nil
@@ -2330,7 +2344,24 @@ func CreateIssue(ctx context.Context, client *github.Client, owner string, repo
 	return utils.NewToolResultText(string(r)), nil
 }
 
-func UpdateIssue(ctx context.Context, client *github.Client, gqlClient *githubv4.Client, owner string, repo string, issueNumber int, title string, body string, assignees []string, labels []string, milestoneNum int, issueType string, issueFieldValues []*github.IssueRequestFieldValue, fieldIDsToDelete []int64, state string, stateReason string, duplicateOf int) (*mcp.CallToolResult, error) {
+// UpdateIssueOptions controls which optional fields are included in an issue update request.
+type UpdateIssueOptions struct {
+	// AssigneesProvided sends the assignees field even when the slice is empty.
+	AssigneesProvided bool
+	// LabelsProvided sends the labels field even when the slice is empty.
+	LabelsProvided bool
+}
+
+func UpdateIssue(ctx context.Context, client *github.Client, gqlClient *githubv4.Client, owner string, repo string, issueNumber int, title string, body string, assignees []string, labels []string, milestoneNum int, issueType string, issueFieldValues []*github.IssueRequestFieldValue, fieldIDsToDelete []int64, state string, stateReason string, duplicateOf int, opts ...UpdateIssueOptions) (*mcp.CallToolResult, error) {
+	updateOptions := UpdateIssueOptions{
+		AssigneesProvided: len(assignees) > 0,
+		LabelsProvided:    len(labels) > 0,
+	}
+	for _, opt := range opts {
+		updateOptions.AssigneesProvided = updateOptions.AssigneesProvided || opt.AssigneesProvided
+		updateOptions.LabelsProvided = updateOptions.LabelsProvided || opt.LabelsProvided
+	}
+
 	// Create the issue request with only provided fields
 	issueRequest := &github.IssueRequest{}
 
@@ -2343,11 +2374,11 @@ func UpdateIssue(ctx context.Context, client *github.Client, gqlClient *githubv4
 		issueRequest.Body = github.Ptr(body)
 	}
 
-	if len(labels) > 0 {
+	if updateOptions.LabelsProvided {
 		issueRequest.Labels = &labels
 	}
 
-	if len(assignees) > 0 {
+	if updateOptions.AssigneesProvided {
 		issueRequest.Assignees = &assignees
 	}
 

diff --git a/pkg/github/issues_test.go b/pkg/github/issues_test.go
@@ -2987,6 +2987,33 @@ func Test_UpdateIssue(t *testing.T) {
 			expectError:   false,
 			expectedIssue: mockUpdatedIssue,
 		},
+		{
+			name: "partial update clears labels and assignees",
+			mockedRESTClient: MockHTTPClientWithHandlers(map[string]http.HandlerFunc{
+				PatchReposIssuesByOwnerByRepoByIssueNumber: expectRequestBody(t, map[string]any{
+					"labels":    []any{},
+					"assignees": []any{},
+				}).andThen(
+					mockResponse(t, http.StatusOK, &github.Issue{
+						Number:  github.Ptr(123),
+						HTMLURL: github.Ptr("https://github.com/owner/repo/issues/123"),
+					}),
+				),
+			}),
+			mockedGQLClient: githubv4mock.NewMockedHTTPClient(),
+			requestArgs: map[string]any{
+				"method":       "update",
+				"owner":        "owner",
+				"repo":         "repo",
+				"issue_number": float64(123),
+				"labels":       []any{},
+				"assignees":    []any{},
+			},
+			expectError: false,
+			expectedIssue: &github.Issue{
+				HTMLURL: github.Ptr("https://github.com/owner/repo/issues/123"),
+			},
+		},
 		{
 			name: "partial update with issue fields reconciled by names",
 			mockedRESTClient: MockHTTPClientWithHandlers(map[string]http.HandlerFunc{
@@ -3406,6 +3433,47 @@ func Test_UpdateIssue(t *testing.T) {
 	}
 }
 
+func Test_LegacyUpdateIssueClearsLabelsAndAssignees(t *testing.T) {
+	serverTool := LegacyIssueWrite(translations.NullTranslationHelper)
+	updatedIssue := &github.Issue{
+		Number:  github.Ptr(8),
+		HTMLURL: github.Ptr("https://github.com/owner/repo/issues/8"),
+	}
+
+	client := mustNewGHClient(t, MockHTTPClientWithHandlers(map[string]http.HandlerFunc{
+		PatchReposIssuesByOwnerByRepoByIssueNumber: expectRequestBody(t, map[string]any{
+			"labels":    []any{},
+			"assignees": []any{},
+		}).andThen(mockResponse(t, http.StatusOK, updatedIssue)),
+	}))
+	gqlClient := githubv4.NewClient(githubv4mock.NewMockedHTTPClient())
+	deps := BaseDeps{
+		Client:    client,
+		GQLClient: gqlClient,
+	}
+	handler := serverTool.Handler(deps)
+
+	request := createMCPRequest(map[string]any{
+		"method":       "update",
+		"owner":        "owner",
+		"repo":         "repo",
+		"issue_number": float64(8),
+		"labels":       []any{},
+		"assignees":    []any{},
+	})
+	result, err := handler(ContextWithDeps(context.Background(), deps), &request)
+
+	require.NoError(t, err)
+	if result.IsError {
+		t.Fatalf("Unexpected error result: %s", getErrorResult(t, result).Text)
+	}
+	textContent := getTextResult(t, result)
+
+	var updateResp MinimalResponse
+	require.NoError(t, json.Unmarshal([]byte(textContent.Text), &updateResp))
+	assert.Equal(t, updatedIssue.GetHTMLURL(), updateResp.URL)
+}
+
 func Test_ParseISOTimestamp(t *testing.T) {
 	tests := []struct {
 		name         string