fix: filter PRs by timestamp to avoid returning stale results

When polling for a linked PR after assigning Copilot to an issue,
we now capture the assignment time before the mutation and filter
to only return PRs created after that time. This prevents the tool
from incorrectly returning old PRs from previous Copilot assignments.

Author: SamMorrowDrums

pkg/github/issues.go

@@ -1611,10 +1611,11 @@ func (d *mvpDescription) String() string {
 
 // linkedPullRequest represents a PR linked to an issue by Copilot.
 type linkedPullRequest struct {
-	Number int
-	URL    string
-	Title  string
-	State  string
+	Number    int
+	URL       string
+	Title     string
+	State     string
+	CreatedAt time.Time
 }
 
 // pollConfigKey is a context key for polling configuration.
@@ -1644,7 +1645,8 @@ func getPollConfig(ctx context.Context) PollConfig {
 
 // findLinkedCopilotPR searches for a PR created by the copilot-swe-agent bot that references the given issue.
 // It queries the issue's timeline for CrossReferencedEvent items from PRs authored by copilot-swe-agent.
-func findLinkedCopilotPR(ctx context.Context, client *githubv4.Client, owner, repo string, issueNumber int) (*linkedPullRequest, error) {
+// The createdAfter parameter filters to only return PRs created after the specified time.
+func findLinkedCopilotPR(ctx context.Context, client *githubv4.Client, owner, repo string, issueNumber int, createdAfter time.Time) (*linkedPullRequest, error) {
 	// Query timeline items looking for CrossReferencedEvent from PRs by copilot-swe-agent
 	var query struct {
 		Repository struct {
@@ -1655,11 +1657,12 @@ func findLinkedCopilotPR(ctx context.Context, client *githubv4.Client, owner, re
 						CrossReferencedEvent struct {
 							Source struct {
 								PullRequest struct {
-									Number int
-									URL    string
-									Title  string
-									State  string
-									Author struct {
+									Number    int
+									URL       string
+									Title     string
+									State     string
+									CreatedAt githubv4.DateTime
+									Author    struct {
 										Login string
 									}
 								} `graphql:"... on PullRequest"`
@@ -1681,19 +1684,23 @@ func findLinkedCopilotPR(ctx context.Context, client *githubv4.Client, owner, re
 		return nil, err
 	}
 
-	// Look for a PR from copilot-swe-agent
+	// Look for a PR from copilot-swe-agent created after the assignment time
 	for _, node := range query.Repository.Issue.TimelineItems.Nodes {
 		if node.TypeName != "CrossReferencedEvent" {
 			continue
 		}
 		pr := node.CrossReferencedEvent.Source.PullRequest
 		if pr.Number > 0 && pr.Author.Login == "copilot-swe-agent" {
-			return &linkedPullRequest{
-				Number: pr.Number,
-				URL:    pr.URL,
-				Title:  pr.Title,
-				State:  pr.State,
-			}, nil
+			// Only return PRs created after the assignment time
+			if pr.CreatedAt.Time.After(createdAfter) {
+				return &linkedPullRequest{
+					Number:    pr.Number,
+					URL:       pr.URL,
+					Title:     pr.Title,
+					State:     pr.State,
+					CreatedAt: pr.CreatedAt.Time,
+				}, nil
+			}
 		}
 	}
 
@@ -1882,6 +1889,9 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 			// The header will be read by the HTTP transport if it's configured to do so
 			ctxWithFeatures := withGraphQLFeatures(ctx, "issues_copilot_assignment_api_support")
 
+			// Capture the time before assignment to filter out older PRs during polling
+			assignmentTime := time.Now().UTC()
+
 			if err := client.Mutate(
 				ctxWithFeatures,
 				&updateIssueMutation,
@@ -1895,7 +1905,7 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 				return nil, nil, fmt.Errorf("failed to update issue with agent assignment: %w", err)
 			}
 
-			// Poll for a linked PR created by Copilot
+			// Poll for a linked PR created by Copilot after the assignment
 			pollConfig := getPollConfig(ctx)
 
 			var linkedPR *linkedPullRequest
@@ -1904,7 +1914,7 @@ func AssignCopilotToIssue(t translations.TranslationHelperFunc) inventory.Server
 					time.Sleep(pollConfig.Delay)
 				}
 
-				pr, err := findLinkedCopilotPR(ctx, client, params.Owner, params.Repo, int(params.IssueNumber))
+				pr, err := findLinkedCopilotPR(ctx, client, params.Owner, params.Repo, int(params.IssueNumber), assignmentTime)
 				if err != nil {
 					// Log but don't fail - polling errors are non-fatal
 					continue