Add get_parent method to issue_read

Add an upward parent read to issue_read, the counterpart to the existing
downward get_sub_issues. Uses the GraphQL Issue.parent field and returns a
null parent when the issue is not a sub-issue. Kept always-on (not feature
gated) to mirror get_sub_issues; the dependency tools remain flag-gated.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: zwick

README.md

@@ -859,8 +859,9 @@ The following sets of tools are available:
     Options are:
     1. get - Get details of a specific issue.
     2. get_comments - Get issue comments.
-    3. get_sub_issues - Get sub-issues of the issue.
-    4. get_labels - Get labels assigned to the issue.
+    3. get_sub_issues - Get sub-issues (children) of the issue.
+    4. get_parent - Get the parent issue, if this issue is a sub-issue of another.
+    5. get_labels - Get labels assigned to the issue.
      (string, required)
   - `owner`: The owner of the repository (string, required)
   - `page`: Page number for pagination (min 1) (number, optional)

pkg/github/__toolsnaps__/issue_read.snap

@@ -11,11 +11,12 @@
         "type": "number"
       },
       "method": {
-        "description": "The read operation to perform on a single issue.\nOptions are:\n1. get - Get details of a specific issue.\n2. get_comments - Get issue comments.\n3. get_sub_issues - Get sub-issues of the issue.\n4. get_labels - Get labels assigned to the issue.\n",
+        "description": "The read operation to perform on a single issue.\nOptions are:\n1. get - Get details of a specific issue.\n2. get_comments - Get issue comments.\n3. get_sub_issues - Get sub-issues (children) of the issue.\n4. get_parent - Get the parent issue, if this issue is a sub-issue of another.\n5. get_labels - Get labels assigned to the issue.\n",
         "enum": [
           "get",
           "get_comments",
           "get_sub_issues",
+          "get_parent",
           "get_labels"
         ],
         "type": "string"

pkg/github/issues.go

@@ -733,10 +733,11 @@ func IssueRead(t translations.TranslationHelperFunc) inventory.ServerTool {
 Options are:
 1. get - Get details of a specific issue.
 2. get_comments - Get issue comments.
-3. get_sub_issues - Get sub-issues of the issue.
-4. get_labels - Get labels assigned to the issue.
+3. get_sub_issues - Get sub-issues (children) of the issue.
+4. get_parent - Get the parent issue, if this issue is a sub-issue of another.
+5. get_labels - Get labels assigned to the issue.
 `,
-				Enum: []any{"get", "get_comments", "get_sub_issues", "get_labels"},
+				Enum: []any{"get", "get_comments", "get_sub_issues", "get_parent", "get_labels"},
 			},
 			"owner": {
 				Type:        "string",
@@ -816,6 +817,9 @@ Options are:
 			case "get_sub_issues":
 				result, err := GetSubIssues(ctx, client, deps, owner, repo, issueNumber, pagination)
 				return attachIFC(result), nil, err
+			case "get_parent":
+				result, err := GetIssueParent(ctx, gqlClient, owner, repo, issueNumber)
+				return attachIFC(result), nil, err
 			case "get_labels":
 				result, err := GetIssueLabels(ctx, gqlClient, owner, repo, issueNumber)
 				return attachIFC(result), nil, err
@@ -1015,6 +1019,52 @@ func GetSubIssues(ctx context.Context, client *github.Client, deps ToolDependenc
 	return utils.NewToolResultText(string(r)), nil
 }
 
+// GetIssueParent returns the parent issue of the given issue, or a null parent
+// when the issue is not a sub-issue of any other issue. It reads the GraphQL
+// Issue.parent field, the upward counterpart to the downward get_sub_issues read.
+func GetIssueParent(ctx context.Context, client *githubv4.Client, owner string, repo string, issueNumber int) (*mcp.CallToolResult, error) {
+	var query struct {
+		Repository struct {
+			Issue struct {
+				Parent *struct {
+					Number     githubv4.Int
+					Title      githubv4.String
+					State      githubv4.String
+					URL        githubv4.String
+					Repository struct {
+						NameWithOwner githubv4.String
+					}
+				}
+			} `graphql:"issue(number: $issueNumber)"`
+		} `graphql:"repository(owner: $owner, name: $repo)"`
+	}
+
+	vars := map[string]any{
+		"owner":       githubv4.String(owner),
+		"repo":        githubv4.String(repo),
+		"issueNumber": githubv4.Int(issueNumber), // #nosec G115 - issue numbers are always small positive integers
+	}
+
+	if err := client.Query(ctx, &query, vars); err != nil {
+		return ghErrors.NewGitHubGraphQLErrorResponse(ctx, "failed to get issue parent", err), nil
+	}
+
+	parent := query.Repository.Issue.Parent
+	if parent == nil {
+		return MarshalledTextResult(map[string]any{"parent": nil}), nil
+	}
+
+	return MarshalledTextResult(map[string]any{
+		"parent": map[string]any{
+			"number":     int(parent.Number),
+			"title":      string(parent.Title),
+			"state":      string(parent.State),
+			"url":        string(parent.URL),
+			"repository": string(parent.Repository.NameWithOwner),
+		},
+	}), nil
+}
+
 func GetIssueLabels(ctx context.Context, client *githubv4.Client, owner string, repo string, issueNumber int) (*mcp.CallToolResult, error) {
 	// Get current labels on the issue using GraphQL
 	var query struct {

pkg/github/issues_test.go

@@ -3822,6 +3822,128 @@ func Test_GetIssueLabels(t *testing.T) {
 	}
 }
 
+func Test_GetIssueParent(t *testing.T) {
+	t.Parallel()
+
+	serverTool := IssueRead(translations.NullTranslationHelper)
+
+	parentMatcherStruct := struct {
+		Repository struct {
+			Issue struct {
+				Parent *struct {
+					Number     githubv4.Int
+					Title      githubv4.String
+					State      githubv4.String
+					URL        githubv4.String
+					Repository struct {
+						NameWithOwner githubv4.String
+					}
+				}
+			} `graphql:"issue(number: $issueNumber)"`
+		} `graphql:"repository(owner: $owner, name: $repo)"`
+	}{}
+
+	vars := map[string]any{
+		"owner":       githubv4.String("owner"),
+		"repo":        githubv4.String("repo"),
+		"issueNumber": githubv4.Int(123),
+	}
+
+	tests := []struct {
+		name            string
+		mockedClient    *http.Client
+		expectToolError bool
+		expectedText    string
+	}{
+		{
+			name: "issue has a parent",
+			mockedClient: githubv4mock.NewMockedHTTPClient(
+				githubv4mock.NewQueryMatcher(
+					parentMatcherStruct,
+					vars,
+					githubv4mock.DataResponse(map[string]any{
+						"repository": map[string]any{
+							"issue": map[string]any{
+								"parent": map[string]any{
+									"number": githubv4.Int(42),
+									"title":  githubv4.String("Parent issue"),
+									"state":  githubv4.String("OPEN"),
+									"url":    githubv4.String("https://github.com/owner/repo/issues/42"),
+									"repository": map[string]any{
+										"nameWithOwner": githubv4.String("owner/repo"),
+									},
+								},
+							},
+						},
+					}),
+				),
+			),
+			expectedText: `"number":42`,
+		},
+		{
+			name: "issue has no parent",
+			mockedClient: githubv4mock.NewMockedHTTPClient(
+				githubv4mock.NewQueryMatcher(
+					parentMatcherStruct,
+					vars,
+					githubv4mock.DataResponse(map[string]any{
+						"repository": map[string]any{
+							"issue": map[string]any{
+								"parent": nil,
+							},
+						},
+					}),
+				),
+			),
+			expectedText: `"parent":null`,
+		},
+		{
+			name: "graphql error",
+			mockedClient: githubv4mock.NewMockedHTTPClient(
+				githubv4mock.NewQueryMatcher(
+					parentMatcherStruct,
+					vars,
+					githubv4mock.ErrorResponse("issue not found"),
+				),
+			),
+			expectToolError: true,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			gqlClient := githubv4.NewClient(tc.mockedClient)
+			client := mustNewGHClient(t, nil)
+			deps := BaseDeps{
+				Client:          client,
+				GQLClient:       gqlClient,
+				RepoAccessCache: stubRepoAccessCache(nil, 15*time.Minute),
+				Flags:           stubFeatureFlags(map[string]bool{"lockdown-mode": false}),
+			}
+			handler := serverTool.Handler(deps)
+
+			request := createMCPRequest(map[string]any{
+				"method":       "get_parent",
+				"owner":        "owner",
+				"repo":         "repo",
+				"issue_number": float64(123),
+			})
+			result, err := handler(ContextWithDeps(context.Background(), deps), &request)
+
+			require.NoError(t, err)
+			require.NotNil(t, result)
+
+			if tc.expectToolError {
+				assert.True(t, result.IsError)
+				return
+			}
+			assert.False(t, result.IsError)
+			textContent := getTextResult(t, result)
+			assert.Contains(t, textContent.Text, tc.expectedText)
+		})
+	}
+}
+
 func Test_AddSubIssue(t *testing.T) {
 	// Verify tool definition once
 	serverTool := SubIssueWrite(translations.NullTranslationHelper)