diff --git a/apps/backend/cmd/kandev/services.go b/apps/backend/cmd/kandev/services.go
index 59c3a894ec..a8bcb8445f 100644
--- a/apps/backend/cmd/kandev/services.go
+++ b/apps/backend/cmd/kandev/services.go
@@ -104,6 +104,7 @@ func provideServices(cfg *config.Config, log *logger.Logger, repos *Repositories
 	// inside their own container).
 	if githubSvc != nil {
 		taskSvc.SetRemoteBranchLister(githubBranchListerAdapter{svc: githubSvc})
+		taskSvc.SetPRTaskResolver(githubSvc)
 	}
 
 	// Initialize Automation service
diff --git a/apps/backend/internal/github/service_pr_watch.go b/apps/backend/internal/github/service_pr_watch.go
index b6c4e4e6c1..454fdfddb7 100644
--- a/apps/backend/internal/github/service_pr_watch.go
+++ b/apps/backend/internal/github/service_pr_watch.go
@@ -344,6 +344,12 @@ func (s *Service) ListTaskPRs(ctx context.Context, taskIDs []string) (map[string
 	return s.store.ListTaskPRsByTaskIDs(ctx, taskIDs)
 }
 
+// FindTaskIDsByPRNumber returns the IDs of tasks in a workspace associated with
+// the given PR number. Used by task search to surface a task by its PR number.
+func (s *Service) FindTaskIDsByPRNumber(ctx context.Context, workspaceID string, prNumber int) ([]string, error) {
+	return s.store.ListTaskIDsByPRNumber(ctx, workspaceID, prNumber)
+}
+
 // ListWorkspaceTaskPRs returns all PR associations for a workspace, grouped by
 // task_id. Multi-repo tasks may have more than one PR per task. It returns
 // cached data immediately and triggers background refresh for stale entries.
diff --git a/apps/backend/internal/github/store.go b/apps/backend/internal/github/store.go
index 3f283723d4..894f011385 100644
--- a/apps/backend/internal/github/store.go
+++ b/apps/backend/internal/github/store.go
@@ -191,6 +191,10 @@ func (s *Store) initSchema() error {
 	if err := s.backfillPRWatchesRepositoryID(); err != nil {
 		return fmt.Errorf("backfill github_pr_watches.repository_id: %w", err)
 	}
+	// pr_number is the 3rd column of UNIQUE(task_id, repository_id, pr_number),
+	// so SQLite can't use that index for the PR-number task search. Add a
+	// dedicated leading-key index so lookups by PR number stay index-backed.
+	_, _ = s.db.Exec(`CREATE INDEX IF NOT EXISTS idx_github_task_prs_pr_number ON github_task_prs (pr_number)`)
 	return nil
 }
 
@@ -744,6 +748,21 @@ func (s *Store) ListTaskPRsByWorkspaceID(ctx context.Context, workspaceID string
 	return groupTaskPRsByTask(prs), nil
 }
 
+// ListTaskIDsByPRNumber returns the IDs of tasks in a workspace that have a PR
+// association with the given PR number. Workspace-scoped via the JOIN on tasks
+// so a PR number shared across workspaces never leaks results. A task with
+// multiple PR rows for the same number (multi-repo) is returned once.
+func (s *Store) ListTaskIDsByPRNumber(ctx context.Context, workspaceID string, prNumber int) ([]string, error) {
+	var ids []string
+	if err := s.ro.SelectContext(ctx, &ids,
+		`SELECT DISTINCT gtp.task_id FROM github_task_prs gtp
+		 INNER JOIN tasks t ON gtp.task_id = t.id
+		 WHERE t.workspace_id = ? AND gtp.pr_number = ?`, workspaceID, prNumber); err != nil {
+		return nil, err
+	}
+	return ids, nil
+}
+
 func groupTaskPRsByTask(prs []TaskPR) map[string][]*TaskPR {
 	result := make(map[string][]*TaskPR)
 	for i := range prs {
diff --git a/apps/backend/internal/github/store_multi_repo_test.go b/apps/backend/internal/github/store_multi_repo_test.go
index 92159ac2e9..e274eb2d43 100644
--- a/apps/backend/internal/github/store_multi_repo_test.go
+++ b/apps/backend/internal/github/store_multi_repo_test.go
@@ -21,7 +21,7 @@ func newTestStore(t *testing.T) *Store {
 	}
 	sqlxDB := sqlx.NewDb(dbConn, "sqlite3")
 	t.Cleanup(func() { _ = sqlxDB.Close() })
-	if _, err := sqlxDB.Exec(`CREATE TABLE tasks (id TEXT PRIMARY KEY, archived_at DATETIME)`); err != nil {
+	if _, err := sqlxDB.Exec(`CREATE TABLE tasks (id TEXT PRIMARY KEY, workspace_id TEXT, archived_at DATETIME)`); err != nil {
 		t.Fatalf("create tasks table: %v", err)
 	}
 	store, err := NewStore(sqlxDB, sqlxDB)
diff --git a/apps/backend/internal/github/store_pr_lookup_test.go b/apps/backend/internal/github/store_pr_lookup_test.go
new file mode 100644
index 0000000000..3ee143a0d8
--- /dev/null
+++ b/apps/backend/internal/github/store_pr_lookup_test.go
@@ -0,0 +1,61 @@
+package github
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestListTaskIDsByPRNumber(t *testing.T) {
+	// newTestStore's tasks table carries workspace_id, which the
+	// workspace-scoped PR-number lookup needs.
+	store := newTestStore(t)
+	ctx := context.Background()
+	now := time.Now().UTC()
+
+	// task-1 (ws-1) has PR #1243, task-2 (ws-1) has PR #99,
+	// task-3 (ws-2) also has PR #1243 — must not leak into ws-1.
+	exec := store.db
+	for _, q := range []string{
+		`INSERT INTO tasks (id, workspace_id) VALUES ('task-1', 'ws-1')`,
+		`INSERT INTO tasks (id, workspace_id) VALUES ('task-2', 'ws-1')`,
+		`INSERT INTO tasks (id, workspace_id) VALUES ('task-3', 'ws-2')`,
+	} {
+		if _, err := exec.Exec(q); err != nil {
+			t.Fatalf("seed task: %v", err)
+		}
+	}
+	mkPR := func(id, taskID string, num int) *TaskPR {
+		return &TaskPR{
+			ID: id, TaskID: taskID, RepositoryID: "repo-" + id,
+			Owner: "kdlbs", Repo: "kandev", PRNumber: num,
+			PRURL: "https://github.com/kdlbs/kandev/pull/1", PRTitle: "x",
+			HeadBranch: "feat/x", BaseBranch: "main", State: "open", CreatedAt: now,
+		}
+	}
+	for _, pr := range []*TaskPR{
+		mkPR("p1", "task-1", 1243),
+		mkPR("p2", "task-2", 99),
+		mkPR("p3", "task-3", 1243),
+	} {
+		if err := store.CreateTaskPR(ctx, pr); err != nil {
+			t.Fatalf("create PR: %v", err)
+		}
+	}
+
+	got, err := store.ListTaskIDsByPRNumber(ctx, "ws-1", 1243)
+	if err != nil {
+		t.Fatalf("lookup: %v", err)
+	}
+	if len(got) != 1 || got[0] != "task-1" {
+		t.Errorf("expected [task-1] for ws-1 PR #1243, got %v", got)
+	}
+
+	none, err := store.ListTaskIDsByPRNumber(ctx, "ws-1", 7777)
+	if err != nil {
+		t.Fatalf("lookup unknown: %v", err)
+	}
+	if len(none) != 0 {
+		t.Errorf("expected no tasks for unknown PR number, got %v", none)
+	}
+}
diff --git a/apps/backend/internal/orchestrator/executor/executor_mocks_test.go b/apps/backend/internal/orchestrator/executor/executor_mocks_test.go
index 58641715fb..9eb366e2c0 100644
--- a/apps/backend/internal/orchestrator/executor/executor_mocks_test.go
+++ b/apps/backend/internal/orchestrator/executor/executor_mocks_test.go
@@ -394,6 +394,15 @@ func (m *mockRepository) GetTask(ctx context.Context, id string) (*models.Task,
 	}
 	return nil, nil
 }
+func (m *mockRepository) GetTasksByIDs(ctx context.Context, ids []string) ([]*models.Task, error) {
+	var out []*models.Task
+	for _, id := range ids {
+		if task, ok := m.tasks[id]; ok {
+			out = append(out, task)
+		}
+	}
+	return out, nil
+}
 func (m *mockRepository) UpdateTask(ctx context.Context, task *models.Task) error { return nil }
 func (m *mockRepository) DeleteTask(ctx context.Context, id string) error         { return nil }
 func (m *mockRepository) ListTasks(ctx context.Context, workflowID string) ([]*models.Task, error) {
diff --git a/apps/backend/internal/task/handlers/process_handlers_test.go b/apps/backend/internal/task/handlers/process_handlers_test.go
index a1c104d6d3..1c8bc5f409 100644
--- a/apps/backend/internal/task/handlers/process_handlers_test.go
+++ b/apps/backend/internal/task/handlers/process_handlers_test.go
@@ -52,6 +52,9 @@ func (m *mockRepository) CreateTask(ctx context.Context, task *models.Task) erro
 func (m *mockRepository) GetTask(ctx context.Context, id string) (*models.Task, error) {
 	return nil, nil
 }
+func (m *mockRepository) GetTasksByIDs(ctx context.Context, ids []string) ([]*models.Task, error) {
+	return nil, nil
+}
 func (m *mockRepository) UpdateTask(ctx context.Context, task *models.Task) error {
 	return nil
 }
diff --git a/apps/backend/internal/task/repository/interface.go b/apps/backend/internal/task/repository/interface.go
index 9f2549c14b..2811560a38 100644
--- a/apps/backend/internal/task/repository/interface.go
+++ b/apps/backend/internal/task/repository/interface.go
@@ -22,6 +22,7 @@ type WorkspaceRepository interface {
 type TaskRepository interface {
 	CreateTask(ctx context.Context, task *models.Task) error
 	GetTask(ctx context.Context, id string) (*models.Task, error)
+	GetTasksByIDs(ctx context.Context, ids []string) ([]*models.Task, error)
 	UpdateTask(ctx context.Context, task *models.Task) error
 	DeleteTask(ctx context.Context, id string) error
 	ListTasks(ctx context.Context, workflowID string) ([]*models.Task, error)
diff --git a/apps/backend/internal/task/repository/sqlite/task.go b/apps/backend/internal/task/repository/sqlite/task.go
index 637f3d72fa..6a8fb1b5ef 100644
--- a/apps/backend/internal/task/repository/sqlite/task.go
+++ b/apps/backend/internal/task/repository/sqlite/task.go
@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -653,6 +654,29 @@ func (r *Repository) scanTasks(rows *sql.Rows) ([]*models.Task, error) {
 	return result, rows.Err()
 }
 
+// GetTasksByIDs fetches multiple tasks in a single query. Missing IDs are
+// silently omitted; result order is not guaranteed, so callers that need a
+// specific order should reorder by ID themselves.
+func (r *Repository) GetTasksByIDs(ctx context.Context, ids []string) ([]*models.Task, error) {
+	if len(ids) == 0 {
+		return nil, nil
+	}
+	placeholders := make([]string, len(ids))
+	args := make([]interface{}, len(ids))
+	for i, id := range ids {
+		placeholders[i] = "?"
+		args[i] = id
+	}
+	query := fmt.Sprintf(`SELECT %s FROM tasks t WHERE t.id IN (%s)`,
+		taskSelectColumns("t"), strings.Join(placeholders, ","))
+	rows, err := r.ro.QueryContext(ctx, r.ro.Rebind(query), args...)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = rows.Close() }()
+	return r.scanTasks(rows)
+}
+
 // ArchiveTask sets the archived_at timestamp on a task
 func (r *Repository) ArchiveTask(ctx context.Context, id string) error {
 	now := time.Now().UTC()
diff --git a/apps/backend/internal/task/repository/task_repository_test.go b/apps/backend/internal/task/repository/task_repository_test.go
index 8c90aea949..749ca08cfb 100644
--- a/apps/backend/internal/task/repository/task_repository_test.go
+++ b/apps/backend/internal/task/repository/task_repository_test.go
@@ -201,6 +201,40 @@ func TestSQLiteRepository_ListTasks(t *testing.T) {
 	}
 }
 
+func TestSQLiteRepository_GetTasksByIDs(t *testing.T) {
+	repo, cleanup := createTestSQLiteRepo(t)
+	defer cleanup()
+	ctx := context.Background()
+
+	_ = repo.CreateWorkspace(ctx, &models.Workspace{ID: "ws-1", Name: "Workspace"})
+	_ = repo.CreateWorkflow(ctx, &models.Workflow{ID: "wf-1", WorkspaceID: "ws-1", Name: "WF"})
+	for _, id := range []string{"task-1", "task-2", "task-3"} {
+		_ = repo.CreateTask(ctx, &models.Task{ID: id, WorkspaceID: "ws-1", WorkflowID: "wf-1", WorkflowStepID: "step-1", Title: id})
+	}
+
+	// Empty input returns no tasks and no error.
+	none, err := repo.GetTasksByIDs(ctx, nil)
+	if err != nil {
+		t.Fatalf("GetTasksByIDs(nil): %v", err)
+	}
+	if len(none) != 0 {
+		t.Errorf("expected 0 tasks for empty input, got %d", len(none))
+	}
+
+	// Existing + missing IDs: only the existing ones come back.
+	got, err := repo.GetTasksByIDs(ctx, []string{"task-1", "task-3", "missing"})
+	if err != nil {
+		t.Fatalf("GetTasksByIDs: %v", err)
+	}
+	ids := map[string]bool{}
+	for _, tk := range got {
+		ids[tk.ID] = true
+	}
+	if len(got) != 2 || !ids["task-1"] || !ids["task-3"] {
+		t.Errorf("expected [task-1 task-3], got %v", ids)
+	}
+}
+
 func TestSQLiteRepository_ListTasksByWorkflowStep(t *testing.T) {
 	repo, cleanup := createTestSQLiteRepo(t)
 	defer cleanup()
diff --git a/apps/backend/internal/task/service/handoff_access_test.go b/apps/backend/internal/task/service/handoff_access_test.go
index 3e586591c5..2a7fab091e 100644
--- a/apps/backend/internal/task/service/handoff_access_test.go
+++ b/apps/backend/internal/task/service/handoff_access_test.go
@@ -19,6 +19,15 @@ func (f *fakeTaskLookup) GetTask(ctx context.Context, id string) (*models.Task,
 	}
 	return nil, nil
 }
+func (f *fakeTaskLookup) GetTasksByIDs(ctx context.Context, ids []string) ([]*models.Task, error) {
+	var out []*models.Task
+	for _, id := range ids {
+		if t, ok := f.tasks[id]; ok {
+			out = append(out, t)
+		}
+	}
+	return out, nil
+}
 
 func newGraph(tasks ...*models.Task) *fakeTaskLookup {
 	m := make(map[string]*models.Task, len(tasks))
diff --git a/apps/backend/internal/task/service/handoff_workspace_test.go b/apps/backend/internal/task/service/handoff_workspace_test.go
index 77cf1699d3..ebbb8b09db 100644
--- a/apps/backend/internal/task/service/handoff_workspace_test.go
+++ b/apps/backend/internal/task/service/handoff_workspace_test.go
@@ -225,6 +225,18 @@ func (f *fakeTaskRepo) GetTask(_ context.Context, id string) (*models.Task, erro
 	return f.tasks[id], nil
 }
 
+func (f *fakeTaskRepo) GetTasksByIDs(_ context.Context, ids []string) ([]*models.Task, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	var out []*models.Task
+	for _, id := range ids {
+		if t, ok := f.tasks[id]; ok {
+			out = append(out, t)
+		}
+	}
+	return out, nil
+}
+
 func (f *fakeTaskRepo) ListChildren(_ context.Context, parentID string) ([]*models.Task, error) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
@@ -291,6 +303,9 @@ type phase4TaskRepo struct {
 func (r *phase4TaskRepo) GetTask(ctx context.Context, id string) (*models.Task, error) {
 	return r.base.GetTask(ctx, id)
 }
+func (r *phase4TaskRepo) GetTasksByIDs(ctx context.Context, ids []string) ([]*models.Task, error) {
+	return r.base.GetTasksByIDs(ctx, ids)
+}
 func (r *phase4TaskRepo) ListChildren(ctx context.Context, parentID string) ([]*models.Task, error) {
 	return r.base.ListChildren(ctx, parentID)
 }
diff --git a/apps/backend/internal/task/service/service.go b/apps/backend/internal/task/service/service.go
index 0e2e2112aa..a5ab04433e 100644
--- a/apps/backend/internal/task/service/service.go
+++ b/apps/backend/internal/task/service/service.go
@@ -80,6 +80,13 @@ type WorkflowStepGetter interface {
 	GetNextStepByPosition(ctx context.Context, workflowID string, currentPosition int) (*wfmodels.WorkflowStep, error)
 }
 
+// PRTaskResolver resolves which tasks are associated with a GitHub PR number.
+// Implemented by the github service; injected so the task service can surface a
+// task by its PR number in search without coupling to the github schema.
+type PRTaskResolver interface {
+	FindTaskIDsByPRNumber(ctx context.Context, workspaceID string, prNumber int) ([]string, error)
+}
+
 // StartStepResolver resolves the starting step for a workflow.
 type StartStepResolver interface {
 	ResolveStartStep(ctx context.Context, workflowID string) (string, error)
@@ -152,6 +159,7 @@ type Service struct {
 	workflowStepCreator   WorkflowStepCreator
 	workflowStepGetter    WorkflowStepGetter
 	startStepResolver     StartStepResolver
+	prTaskResolver        PRTaskResolver
 	quickChatDir          string // Directory for quick-chat workspaces (e.g., ~/.kandev/quick-chat)
 	branchFetcher         *branchFetcher
 	envDestroyer          EnvironmentDestroyer
@@ -222,6 +230,12 @@ func (s *Service) SetStartStepResolver(resolver StartStepResolver) {
 	s.startStepResolver = resolver
 }
 
+// SetPRTaskResolver wires the GitHub PR→task resolver for PR-number search.
+// Optional — when unset, search by PR number is a no-op.
+func (s *Service) SetPRTaskResolver(resolver PRTaskResolver) {
+	s.prTaskResolver = resolver
+}
+
 // SetQuickChatDir sets the directory for quick-chat workspaces.
 // When set, task cleanup deletes the session directory under this path for all tasks.
 func (s *Service) SetQuickChatDir(dir string) {
diff --git a/apps/backend/internal/task/service/service_pr_search_test.go b/apps/backend/internal/task/service/service_pr_search_test.go
new file mode 100644
index 0000000000..23b75239af
--- /dev/null
+++ b/apps/backend/internal/task/service/service_pr_search_test.go
@@ -0,0 +1,197 @@
+package service
+
+import (
+	"context"
+	"testing"
+
+	"github.com/kandev/kandev/internal/task/models"
+	v1 "github.com/kandev/kandev/pkg/api/v1"
+)
+
+// fakePRResolver is a stand-in for the github service in PR-number search tests.
+type fakePRResolver struct {
+	byPR   map[int][]string
+	err    error
+	called bool
+}
+
+func (f *fakePRResolver) FindTaskIDsByPRNumber(_ context.Context, _ string, prNumber int) ([]string, error) {
+	f.called = true
+	if f.err != nil {
+		return nil, f.err
+	}
+	return f.byPR[prNumber], nil
+}
+
+func seedPRSearchTasks(t *testing.T, repo interface {
+	CreateWorkspace(context.Context, *models.Workspace) error
+	CreateWorkflow(context.Context, *models.Workflow) error
+	CreateTask(context.Context, *models.Task) error
+}) {
+	t.Helper()
+	ctx := context.Background()
+	if err := repo.CreateWorkspace(ctx, &models.Workspace{ID: "ws-1", Name: "WS"}); err != nil {
+		t.Fatalf("create workspace: %v", err)
+	}
+	if err := repo.CreateWorkflow(ctx, &models.Workflow{ID: "wf-1", WorkspaceID: "ws-1", Name: "WF"}); err != nil {
+		t.Fatalf("create workflow: %v", err)
+	}
+	tasks := []*models.Task{
+		{ID: "task-pr", WorkspaceID: "ws-1", WorkflowID: "wf-1", WorkflowStepID: "step-1", Title: "Unrelated work", State: v1.TaskStateCreated, Priority: "medium"},
+		{ID: "task-title", WorkspaceID: "ws-1", WorkflowID: "wf-1", WorkflowStepID: "step-1", Title: "Bug in PR 1243 handler", State: v1.TaskStateCreated, Priority: "medium"},
+	}
+	for _, tk := range tasks {
+		if err := repo.CreateTask(ctx, tk); err != nil {
+			t.Fatalf("create task %s: %v", tk.ID, err)
+		}
+	}
+}
+
+func taskIDSet(tasks []*models.Task) map[string]bool {
+	set := make(map[string]bool, len(tasks))
+	for _, t := range tasks {
+		set[t.ID] = true
+	}
+	return set
+}
+
+func TestListTasksByWorkspace_PRNumberSurfacesTask(t *testing.T) {
+	svc, _, repo := createTestService(t)
+	seedPRSearchTasks(t, repo)
+	svc.SetPRTaskResolver(&fakePRResolver{byPR: map[int][]string{1243: {"task-pr"}}})
+	ctx := context.Background()
+
+	// "#1243" — task-pr has no "1243" in its title, only the PR association.
+	tasks, total, err := svc.ListTasksByWorkspace(ctx, "ws-1", "", "", "#1243", 1, 5, true, false, false, false)
+	if err != nil {
+		t.Fatalf("search: %v", err)
+	}
+	got := taskIDSet(tasks)
+	if !got["task-pr"] {
+		t.Errorf("expected task-pr surfaced by PR number, got %v", got)
+	}
+	if total < 1 {
+		t.Errorf("expected total >= 1, got %d", total)
+	}
+}
+
+func TestListTasksByWorkspace_PRNumberDedupes(t *testing.T) {
+	svc, _, repo := createTestService(t)
+	seedPRSearchTasks(t, repo)
+	// Resolver returns task-title, which ALSO matches the LIKE search for "1243".
+	svc.SetPRTaskResolver(&fakePRResolver{byPR: map[int][]string{1243: {"task-title"}}})
+	ctx := context.Background()
+
+	tasks, _, err := svc.ListTasksByWorkspace(ctx, "ws-1", "", "", "1243", 1, 5, true, false, false, false)
+	if err != nil {
+		t.Fatalf("search: %v", err)
+	}
+	count := 0
+	for _, tk := range tasks {
+		if tk.ID == "task-title" {
+			count++
+		}
+	}
+	if count != 1 {
+		t.Errorf("expected task-title exactly once, got %d", count)
+	}
+}
+
+func TestListTasksByWorkspace_NonNumericQuerySkipsResolver(t *testing.T) {
+	svc, _, repo := createTestService(t)
+	seedPRSearchTasks(t, repo)
+	resolver := &fakePRResolver{byPR: map[int][]string{1243: {"task-pr"}}}
+	svc.SetPRTaskResolver(resolver)
+	ctx := context.Background()
+
+	tasks, _, err := svc.ListTasksByWorkspace(ctx, "ws-1", "", "", "unrelated", 1, 5, true, false, false, false)
+	if err != nil {
+		t.Fatalf("search: %v", err)
+	}
+	if resolver.called {
+		t.Error("resolver should not be consulted for a non-numeric query")
+	}
+	// task-pr matches the title LIKE search, task-title does not.
+	if got := taskIDSet(tasks); !got["task-pr"] {
+		t.Errorf("expected title match task-pr, got %v", got)
+	}
+}
+
+func TestListTasksByWorkspace_NilResolverNoPanic(t *testing.T) {
+	svc, _, repo := createTestService(t)
+	seedPRSearchTasks(t, repo)
+	ctx := context.Background()
+
+	// No resolver wired — PR-number search must be a safe no-op.
+	tasks, _, err := svc.ListTasksByWorkspace(ctx, "ws-1", "", "", "#1243", 1, 5, true, false, false, false)
+	if err != nil {
+		t.Fatalf("search: %v", err)
+	}
+	// task-pr is only reachable via the resolver, so it must be absent.
+	if got := taskIDSet(tasks); got["task-pr"] {
+		t.Errorf("did not expect task-pr without a resolver, got %v", got)
+	}
+}
+
+func TestListTasksByWorkspace_PRMatchRespectsArchivedFilter(t *testing.T) {
+	svc, _, repo := createTestService(t)
+	seedPRSearchTasks(t, repo)
+	if err := repo.ArchiveTask(context.Background(), "task-pr"); err != nil {
+		t.Fatalf("archive: %v", err)
+	}
+	svc.SetPRTaskResolver(&fakePRResolver{byPR: map[int][]string{1243: {"task-pr"}}})
+	ctx := context.Background()
+
+	// includeArchived=false → archived PR task excluded.
+	excluded, _, err := svc.ListTasksByWorkspace(ctx, "ws-1", "", "", "#1243", 1, 5, false, false, false, false)
+	if err != nil {
+		t.Fatalf("search excluded: %v", err)
+	}
+	if taskIDSet(excluded)["task-pr"] {
+		t.Error("archived task-pr should be excluded when includeArchived=false")
+	}
+
+	// includeArchived=true → archived PR task included.
+	included, _, err := svc.ListTasksByWorkspace(ctx, "ws-1", "", "", "#1243", 1, 5, true, false, false, false)
+	if err != nil {
+		t.Fatalf("search included: %v", err)
+	}
+	if !taskIDSet(included)["task-pr"] {
+		t.Error("archived task-pr should be included when includeArchived=true")
+	}
+}
+
+func TestListTasksByWorkspace_PRMatchSkippedOnLaterPagesAndScopedSearches(t *testing.T) {
+	ctx := context.Background()
+	cases := []struct {
+		name       string
+		page       int
+		workflowID string
+		repoID     string
+	}{
+		{name: "page 2", page: 2},
+		{name: "workflow-scoped", page: 1, workflowID: "wf-1"},
+		{name: "repository-scoped", page: 1, repoID: "repo-x"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			svc, _, repo := createTestService(t)
+			seedPRSearchTasks(t, repo)
+			resolver := &fakePRResolver{byPR: map[int][]string{1243: {"task-pr"}}}
+			svc.SetPRTaskResolver(resolver)
+
+			tasks, _, err := svc.ListTasksByWorkspace(ctx, "ws-1", tc.workflowID, tc.repoID, "#1243", tc.page, 5, true, false, false, false)
+			if err != nil {
+				t.Fatalf("search: %v", err)
+			}
+			if resolver.called {
+				t.Error("resolver should not be consulted for later pages or scoped searches")
+			}
+			if taskIDSet(tasks)["task-pr"] {
+				t.Errorf("task-pr should not be augmented for %s, got %v", tc.name, taskIDSet(tasks))
+			}
+		})
+	}
+}
+
+var _ PRTaskResolver = (*fakePRResolver)(nil)
diff --git a/apps/backend/internal/task/service/service_tasks.go b/apps/backend/internal/task/service/service_tasks.go
index 8d4642145b..f8f7ebe651 100644
--- a/apps/backend/internal/task/service/service_tasks.go
+++ b/apps/backend/internal/task/service/service_tasks.go
@@ -1075,6 +1075,19 @@ func (s *Service) ListTasksByWorkspace(ctx context.Context, workspaceID, workflo
 		return nil, 0, err
 	}
 
+	tasks, total = s.augmentWithPRMatches(ctx, tasks, total, prSearchOptions{
+		workspaceID:      workspaceID,
+		workflowID:       workflowID,
+		repositoryID:     repositoryID,
+		query:            query,
+		page:             page,
+		pageSize:         pageSize,
+		includeArchived:  includeArchived,
+		includeEphemeral: includeEphemeral,
+		onlyEphemeral:    onlyEphemeral,
+		excludeConfig:    excludeConfig,
+	})
+
 	if err := s.loadTaskRepositoriesBatch(ctx, tasks); err != nil {
 		s.logger.Error("failed to batch-load task repositories", zap.Error(err))
 	}
@@ -1082,6 +1095,145 @@ func (s *Service) ListTasksByWorkspace(ctx context.Context, workspaceID, workflo
 	return tasks, total, nil
 }
 
+type prSearchOptions struct {
+	workspaceID      string
+	workflowID       string
+	repositoryID     string
+	query            string
+	page             int
+	pageSize         int
+	includeArchived  bool
+	includeEphemeral bool
+	onlyEphemeral    bool
+	excludeConfig    bool
+}
+
+// parsePRQuery extracts a positive PR number from a search query, accepting an
+// optional leading '#'. Returns (0, false) when the query is not a PR number.
+func parsePRQuery(query string) (int, bool) {
+	trimmed := strings.TrimPrefix(strings.TrimSpace(query), "#")
+	if trimmed == "" {
+		return 0, false
+	}
+	n, err := strconv.Atoi(trimmed)
+	if err != nil || n <= 0 {
+		return 0, false
+	}
+	return n, true
+}
+
+// isConfigTask reports whether a task is a config-mode task (mirrors the SQL
+// `json_extract(metadata, '$.config_mode') IS NOT 1` filter). JSON-decoded
+// numbers arrive as float64, so accept both numeric 1 and bool true.
+func isConfigTask(task *models.Task) bool {
+	switch v := task.Metadata["config_mode"].(type) {
+	case float64:
+		return v == 1
+	case int:
+		return v == 1
+	case bool:
+		return v
+	default:
+		return false
+	}
+}
+
+// augmentWithPRMatches surfaces tasks associated with a PR number when the
+// search query looks like one. PR matches are prepended (most relevant) and
+// deduped against the existing results; `total` grows by the net-new count.
+// Best-effort: a missing resolver or a lookup error leaves results unchanged.
+//
+// Augmentation only applies to the first page of an unscoped search. It is
+// skipped for page > 1 (the prepend+truncate only makes sense against page 1,
+// otherwise a PR match would re-appear on every page and push out a real
+// result) and when a workflow or repository filter is set (a PR-matched task
+// isn't guaranteed to satisfy those filters, and the only caller that searches
+// by PR number — the Cmd+K command panel — sets neither).
+func (s *Service) augmentWithPRMatches(ctx context.Context, tasks []*models.Task, total int, opts prSearchOptions) ([]*models.Task, int) {
+	if opts.page > 1 || opts.workflowID != "" || opts.repositoryID != "" {
+		return tasks, total
+	}
+	prNum, ok := parsePRQuery(opts.query)
+	if !ok || s.prTaskResolver == nil {
+		return tasks, total
+	}
+	ids, err := s.prTaskResolver.FindTaskIDsByPRNumber(ctx, opts.workspaceID, prNum)
+	if err != nil {
+		s.logger.Warn("PR-number task lookup failed", zap.Int("pr_number", prNum), zap.Error(err))
+		return tasks, total
+	}
+
+	matched := s.fetchPRMatchedTasks(ctx, ids, tasks, opts)
+	if len(matched) == 0 {
+		return tasks, total
+	}
+
+	merged := make([]*models.Task, 0, len(matched)+len(tasks))
+	merged = append(merged, matched...)
+	merged = append(merged, tasks...)
+	total += len(matched)
+	if len(merged) > opts.pageSize {
+		merged = merged[:opts.pageSize]
+	}
+	return merged, total
+}
+
+// fetchPRMatchedTasks batch-loads the resolver's task IDs that aren't already in
+// `existing`, applies the same visibility filters as the repository search, and
+// returns the survivors in resolver order. The resolver returns distinct IDs,
+// so excluding the already-present ones is enough to keep the result deduped.
+func (s *Service) fetchPRMatchedTasks(ctx context.Context, ids []string, existing []*models.Task, opts prSearchOptions) []*models.Task {
+	seen := make(map[string]struct{}, len(existing))
+	for _, t := range existing {
+		seen[t.ID] = struct{}{}
+	}
+	var fetchIDs []string
+	for _, id := range ids {
+		if _, ok := seen[id]; !ok {
+			fetchIDs = append(fetchIDs, id)
+		}
+	}
+	if len(fetchIDs) == 0 {
+		return nil
+	}
+	fetched, err := s.tasks.GetTasksByIDs(ctx, fetchIDs)
+	if err != nil {
+		s.logger.Warn("PR-match task fetch failed", zap.Error(err))
+		return nil
+	}
+	byID := make(map[string]*models.Task, len(fetched))
+	for _, t := range fetched {
+		byID[t.ID] = t
+	}
+	var matched []*models.Task
+	for _, id := range fetchIDs {
+		task := byID[id]
+		if task == nil || s.prMatchFilteredOut(task, opts) {
+			continue
+		}
+		matched = append(matched, task)
+	}
+	return matched
+}
+
+// prMatchFilteredOut applies the same visibility filters the repository search
+// uses, so a PR-matched task respects includeArchived / ephemeral / config flags.
+func (s *Service) prMatchFilteredOut(task *models.Task, opts prSearchOptions) bool {
+	if !opts.includeArchived && task.ArchivedAt != nil {
+		return true
+	}
+	if opts.onlyEphemeral && !task.IsEphemeral {
+		return true
+	}
+	if !opts.includeEphemeral && !opts.onlyEphemeral && task.IsEphemeral {
+		return true
+	}
+	if opts.excludeConfig && isConfigTask(task) {
+		return true
+	}
+	return false
+}
+
 // loadTaskRepositoriesBatch loads repositories for multiple tasks in a single query.
 func (s *Service) loadTaskRepositoriesBatch(ctx context.Context, tasks []*models.Task) error {
 	if len(tasks) == 0 {