Add base_ref parameter and GraphQL-Features header support to assign_copilot_to_issue tool

README.md

@@ -751,6 +751,7 @@ The following sets of tools are available:
 
 - **assign_copilot_to_issue** - Assign Copilot to issue
   - **Required OAuth Scopes**: `repo`
+  - `base_ref`: Git reference (e.g., branch) that the agent will start its work from. If not specified, defaults to the repository's default branch (string, optional)
   - `issue_number`: Issue number (number, required)
   - `owner`: Repository owner (string, required)
   - `repo`: Repository name (string, required)

internal/ghmcp/server.go

@@ -622,6 +622,12 @@ type bearerAuthTransport struct {
 func (t *bearerAuthTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	req = req.Clone(req.Context())
 	req.Header.Set("Authorization", "Bearer "+t.token)
+
+	// Check for GraphQL-Features in context and add header if present
+	if features := github.GetGraphQLFeatures(req.Context()); len(features) > 0 {
+		req.Header.Set("GraphQL-Features", strings.Join(features, ", "))
+	}
+
 	return t.transport.RoundTrip(req)
 }
 

pkg/github/__toolsnaps__/assign_copilot_to_issue.snap

@@ -7,6 +7,10 @@
   "inputSchema": {
     "type": "object",
     "properties": {
+      "base_ref": {
+        "type": "string",
+        "description": "Git reference (e.g., branch) that the agent will start its work from. If not specified, defaults to the repository's default branch"
+      },
       "issue_number": {
         "type": "number",
         "description": "Issue number"

pkg/github/issues.go

@@ -1646,6 +1646,10 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 						Type:        "number",
 						Description: "Issue number",
 					},
+					"base_ref": {
+						Type:        "string",
+						Description: "Git reference (e.g., branch) that the agent will start its work from. If not specified, defaults to the repository's default branch",
+					},
 				},
 				Required: []string{"owner", "repo", "issue_number"},
 			},
@@ -1656,6 +1660,7 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 				Owner       string `mapstructure:"owner"`
 				Repo        string `mapstructure:"repo"`
 				IssueNumber int32  `mapstructure:"issue_number"`
+				BaseRef     string `mapstructure:"base_ref"`
 			}
 			if err := mapstructure.Decode(args, &params); err != nil {
 				return utils.NewToolResultError(err.Error()), nil, nil
@@ -1724,10 +1729,10 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 				return utils.NewToolResultError("copilot isn't available as an assignee for this issue. Please inform the user to visit https://docs.github.com/en/copilot/using-github-copilot/using-copilot-coding-agent-to-work-on-tasks/about-assigning-tasks-to-copilot for more information."), nil, nil
 			}
 
-			// Next let's get the GQL Node ID and current assignees for this issue because the only way to
-			// assign copilot is to use replaceActorsForAssignable which requires the full list.
+			// Next, get the issue ID and repository ID
 			var getIssueQuery struct {
 				Repository struct {
+					ID    githubv4.ID
 					Issue struct {
 						ID        githubv4.ID
 						Assignees struct {
@@ -1749,30 +1754,54 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 				return ghErrors.NewGitHubGraphQLErrorResponse(ctx, "failed to get issue ID", err), nil, nil
 			}
 
-			// Finally, do the assignment. Just for reference, assigning copilot to an issue that it is already
-			// assigned to seems to have no impact (which is a good thing).
-			var assignCopilotMutation struct {
-				ReplaceActorsForAssignable struct {
-					Typename string `graphql:"__typename"` // Not required but we need a selector or GQL errors
-				} `graphql:"replaceActorsForAssignable(input: $input)"`
-			}
-
+			// Build the assignee IDs list including copilot
 			actorIDs := make([]githubv4.ID, len(getIssueQuery.Repository.Issue.Assignees.Nodes)+1)
 			for i, node := range getIssueQuery.Repository.Issue.Assignees.Nodes {
 				actorIDs[i] = node.ID
 			}
 			actorIDs[len(getIssueQuery.Repository.Issue.Assignees.Nodes)] = copilotAssignee.ID
 
+			// Prepare agent assignment input
+			emptyString := githubv4.String("")
+			agentAssignment := &AgentAssignmentInput{
+				CustomAgent:        &emptyString,
+				CustomInstructions: &emptyString,
+				TargetRepositoryID: getIssueQuery.Repository.ID,
+			}
+
+			// Add base ref if provided
+			if params.BaseRef != "" {
+				baseRef := githubv4.String(params.BaseRef)
+				agentAssignment.BaseRef = &baseRef
+			}
+
+			// Execute the updateIssue mutation with the GraphQL-Features header
+			// This header is required for the agent assignment API which is not GA yet
+			var updateIssueMutation struct {
+				UpdateIssue struct {
+					Issue struct {
+						ID     githubv4.ID
+						Number githubv4.Int
+						URL    githubv4.String
+					}
+				} `graphql:"updateIssue(input: $input)"`
+			}
+
+			// Add the GraphQL-Features header for the agent assignment API
+			// The header will be read by the HTTP transport if it's configured to do so
+			ctxWithFeatures := withGraphQLFeatures(ctx, "issues_copilot_assignment_api_support")
+
 			if err := client.Mutate(
-				ctx,
-				&assignCopilotMutation,
-				ReplaceActorsForAssignableInput{
-					AssignableID: getIssueQuery.Repository.Issue.ID,
-					ActorIDs:     actorIDs,
+				ctxWithFeatures,
+				&updateIssueMutation,
+				UpdateIssueInput{
+					ID:              getIssueQuery.Repository.Issue.ID,
+					AssigneeIDs:     actorIDs,
+					AgentAssignment: agentAssignment,
 				},
 				nil,
 			); err != nil {
-				return nil, nil, fmt.Errorf("failed to replace actors for assignable: %w", err)
+				return nil, nil, fmt.Errorf("failed to update issue with agent assignment: %w", err)
 			}
 
 			return utils.NewToolResultText("successfully assigned copilot to issue"), nil, nil
@@ -1784,6 +1813,21 @@ type ReplaceActorsForAssignableInput struct {
 	ActorIDs     []githubv4.ID `json:"actorIds"`
 }
 
+// AgentAssignmentInput represents the input for assigning an agent to an issue.
+type AgentAssignmentInput struct {
+	BaseRef            *githubv4.String `json:"baseRef,omitempty"`
+	CustomAgent        *githubv4.String `json:"customAgent,omitempty"`
+	CustomInstructions *githubv4.String `json:"customInstructions,omitempty"`
+	TargetRepositoryID githubv4.ID      `json:"targetRepositoryId"`
+}
+
+// UpdateIssueInput represents the input for updating an issue with agent assignment.
+type UpdateIssueInput struct {
+	ID              githubv4.ID           `json:"id"`
+	AssigneeIDs     []githubv4.ID         `json:"assigneeIds"`
+	AgentAssignment *AgentAssignmentInput `json:"agentAssignment,omitempty"`
+}
+
 // parseISOTimestamp parses an ISO 8601 timestamp string into a time.Time object.
 // Returns the parsed time or an error if parsing fails.
 // Example formats supported: "2023-01-15T14:30:00Z", "2023-01-15"
@@ -1869,3 +1913,19 @@ func AssignCodingAgentPrompt(t translations.TranslationHelperFunc) inventory.Ser
 		},
 	)
 }
+
+// graphQLFeaturesKey is a context key for GraphQL feature flags
+type graphQLFeaturesKey struct{}
+
+// withGraphQLFeatures adds GraphQL feature flags to the context
+func withGraphQLFeatures(ctx context.Context, features ...string) context.Context {
+	return context.WithValue(ctx, graphQLFeaturesKey{}, features)
+}
+
+// GetGraphQLFeatures retrieves GraphQL feature flags from the context
+func GetGraphQLFeatures(ctx context.Context) []string {
+	if features, ok := ctx.Value(graphQLFeaturesKey{}).([]string); ok {
+		return features
+	}
+	return nil
+}