diff --git a/apps/api/internal/service/access.go b/apps/api/internal/service/access.go
new file mode 100644
index 00000000..2d526132
--- /dev/null
+++ b/apps/api/internal/service/access.go
@@ -0,0 +1,49 @@
+package service
+
+import (
+	"context"
+
+	"github.com/google/uuid"
+
+	"github.com/Devlaner/devlane/api/internal/model"
+	"github.com/Devlaner/devlane/api/internal/store"
+)
+
+// enforceProjectVisibility rejects access to a project whose visibility
+// (`network`) is not public, unless the caller is a workspace admin/owner or a
+// member of the project itself. Public projects are visible to any workspace
+// member.
+//
+// It mirrors the gate in ProjectService.GetByID so that project sub-resources
+// (issues, states, labels, cycles, modules, estimates, intake, comments, pages,
+// views, attachments, …) respect the same rules — otherwise a plain workspace
+// member could reach a secret project's data through its sub-resource routes
+// even though the project itself returns 404.
+//
+// It returns ErrProjectNotFound when the project is hidden from the caller, to
+// match GetByID's 404 behaviour and avoid leaking the project's existence.
+// Callers should invoke it only after they have already confirmed workspace
+// membership and that the project belongs to the workspace.
+func enforceProjectVisibility(
+	ctx context.Context,
+	ps *store.ProjectStore,
+	ws *store.WorkspaceStore,
+	workspaceID, projectID, userID uuid.UUID,
+) error {
+	p, err := ps.GetByID(ctx, projectID)
+	if err != nil {
+		return ErrProjectNotFound
+	}
+	if p.Network == model.NetworkPublic {
+		return nil
+	}
+	// Secret project: workspace admins/owners can always see it.
+	if wm, err := ws.GetMember(ctx, workspaceID, userID); err == nil && wm != nil && wm.Role >= model.RoleAdmin {
+		return nil
+	}
+	// Otherwise the caller must be a member of the project.
+	if pm, err := ps.GetProjectMember(ctx, projectID, userID); err == nil && pm != nil {
+		return nil
+	}
+	return ErrProjectNotFound
+}
diff --git a/apps/api/internal/service/access_test.go b/apps/api/internal/service/access_test.go
new file mode 100644
index 00000000..a7167127
--- /dev/null
+++ b/apps/api/internal/service/access_test.go
@@ -0,0 +1,109 @@
+package service_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/google/uuid"
+	"gorm.io/gorm"
+
+	"github.com/Devlaner/devlane/api/internal/model"
+	"github.com/Devlaner/devlane/api/internal/service"
+	"github.com/Devlaner/devlane/api/internal/store"
+	"github.com/Devlaner/devlane/api/internal/testutil"
+)
+
+func makeProjectSecret(t *testing.T, db *gorm.DB, projectID uuid.UUID) {
+	t.Helper()
+	if err := db.Model(&model.Project{}).Where("id = ?", projectID).
+		Update("network", model.NetworkSecret).Error; err != nil {
+		t.Fatalf("make project secret: %v", err)
+	}
+}
+
+// A secret (non-public) project's sub-resources must respect the same
+// visibility rule as ProjectService.GetByID: reachable only by a workspace
+// admin/owner or a member of the project — never by a plain workspace member
+// who was never added to the project, even though workspace membership and
+// project-in-workspace both pass. Exercised through real service methods so the
+// gate is verified end-to-end for every sub-resource that shares
+// ensureProjectAccess.
+func TestSecretProjectVisibility(t *testing.T) {
+	ts := testutil.NewTestServer(t)
+	db := ts.DB
+	ctx := context.Background()
+
+	owner := testutil.CreateUser(t, db)
+	wrk := testutil.CreateWorkspace(t, db, owner.ID) // workspace owner + auto project lead
+
+	admin := testutil.CreateUser(t, db)
+	testutil.AddWorkspaceMember(t, db, wrk.ID, admin.ID, model.RoleAdmin)
+
+	// Plain workspace member, not added to the project.
+	outsider := testutil.CreateUser(t, db)
+	testutil.AddWorkspaceMember(t, db, wrk.ID, outsider.ID, model.RoleMember)
+
+	// Plain workspace member who IS a member of the project.
+	insider := testutil.CreateUser(t, db)
+	testutil.AddWorkspaceMember(t, db, wrk.ID, insider.ID, model.RoleMember)
+
+	proj := testutil.CreateProject(t, db, wrk.ID, owner.ID)
+	testutil.AddProjectMember(t, db, proj.ID, wrk.ID, insider.ID, model.RoleMember)
+
+	intakeSvc := service.NewIntakeService(
+		store.NewIntakeStore(db),
+		store.NewIssueStore(db),
+		store.NewProjectStore(db),
+		store.NewWorkspaceStore(db),
+	)
+	stateSvc := service.NewStateService(
+		store.NewStateStore(db),
+		store.NewProjectStore(db),
+		store.NewWorkspaceStore(db),
+	)
+
+	// listErr returns the access error surfaced by two independent
+	// sub-resource services (intake and states), so the assertion isn't tied
+	// to one code path.
+	listErr := func(userID uuid.UUID) (error, error) {
+		_, e1 := intakeSvc.List(ctx, wrk.Slug, proj.ID, userID, nil)
+		_, e2 := stateSvc.List(ctx, wrk.Slug, proj.ID, userID)
+		return e1, e2
+	}
+
+	// While public, every workspace member can read the sub-resources.
+	if e1, e2 := listErr(outsider.ID); e1 != nil || e2 != nil {
+		t.Fatalf("public project should be readable by a workspace member: intake=%v state=%v", e1, e2)
+	}
+
+	makeProjectSecret(t, db, proj.ID)
+
+	t.Run("outsider-denied", func(t *testing.T) {
+		e1, e2 := listErr(outsider.ID)
+		if !errors.Is(e1, service.ErrProjectNotFound) {
+			t.Errorf("intake: want ErrProjectNotFound, got %v", e1)
+		}
+		if !errors.Is(e2, service.ErrProjectNotFound) {
+			t.Errorf("states: want ErrProjectNotFound, got %v", e2)
+		}
+	})
+
+	t.Run("workspace-admin-allowed", func(t *testing.T) {
+		if e1, e2 := listErr(admin.ID); e1 != nil || e2 != nil {
+			t.Errorf("workspace admin should see the secret project: intake=%v state=%v", e1, e2)
+		}
+	})
+
+	t.Run("project-member-allowed", func(t *testing.T) {
+		if e1, e2 := listErr(insider.ID); e1 != nil || e2 != nil {
+			t.Errorf("project member should see the secret project: intake=%v state=%v", e1, e2)
+		}
+	})
+
+	t.Run("project-lead-allowed", func(t *testing.T) {
+		if e1, e2 := listErr(owner.ID); e1 != nil || e2 != nil {
+			t.Errorf("project lead should see the secret project: intake=%v state=%v", e1, e2)
+		}
+	})
+}
diff --git a/apps/api/internal/service/attachment.go b/apps/api/internal/service/attachment.go
index 94e083d4..543a7a23 100644
--- a/apps/api/internal/service/attachment.go
+++ b/apps/api/internal/service/attachment.go
@@ -81,6 +81,9 @@ func (s *AttachmentService) ensureProjectAccess(ctx context.Context, workspaceSl
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
@@ -118,6 +121,9 @@ func (s *AttachmentService) AuthorizeDownload(ctx context.Context, issueID, asse
 	if !ok {
 		return ErrProjectForbidden
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, att.WorkspaceID, att.ProjectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/comment.go b/apps/api/internal/service/comment.go
index 0ad7a6a8..c1e347d7 100644
--- a/apps/api/internal/service/comment.go
+++ b/apps/api/internal/service/comment.go
@@ -74,6 +74,9 @@ func (s *CommentService) ensureProjectAccess(ctx context.Context, workspaceSlug
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/cycle.go b/apps/api/internal/service/cycle.go
index 04ee1a58..76e0d573 100644
--- a/apps/api/internal/service/cycle.go
+++ b/apps/api/internal/service/cycle.go
@@ -97,6 +97,9 @@ func (s *CycleService) ensureProjectAccess(ctx context.Context, workspaceSlug st
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/estimate.go b/apps/api/internal/service/estimate.go
index 4078e941..386a5672 100644
--- a/apps/api/internal/service/estimate.go
+++ b/apps/api/internal/service/estimate.go
@@ -42,6 +42,9 @@ func (s *EstimateService) ensureProjectAccess(ctx context.Context, workspaceSlug
 	if !inWorkspace {
 		return nil, ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return nil, err
+	}
 	return wrk, nil
 }
 
diff --git a/apps/api/internal/service/export.go b/apps/api/internal/service/export.go
index d73af7b8..26568c1a 100644
--- a/apps/api/internal/service/export.go
+++ b/apps/api/internal/service/export.go
@@ -58,6 +58,9 @@ func (s *ExportService) ExportIssues(ctx context.Context, slug string, userID uu
 		if !in {
 			return "", nil, ErrProjectNotFound
 		}
+		if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, pid, userID); err != nil {
+			return "", nil, err
+		}
 	}
 
 	data, err := s.buildWorkbook(ctx, projectIDs)
diff --git a/apps/api/internal/service/intake.go b/apps/api/internal/service/intake.go
index dae90d97..94a0487f 100644
--- a/apps/api/internal/service/intake.go
+++ b/apps/api/internal/service/intake.go
@@ -58,6 +58,9 @@ func (s *IntakeService) ensureProjectAccess(ctx context.Context, workspaceSlug s
 	if !inWorkspace {
 		return nil, ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return nil, err
+	}
 	return wrk, nil
 }
 
diff --git a/apps/api/internal/service/issue.go b/apps/api/internal/service/issue.go
index 5d651e82..bdbdb25d 100644
--- a/apps/api/internal/service/issue.go
+++ b/apps/api/internal/service/issue.go
@@ -226,6 +226,9 @@ func (s *IssueService) ensureProjectAccess(ctx context.Context, workspaceSlug st
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/issue_view.go b/apps/api/internal/service/issue_view.go
index 9f1e10cc..68f72dec 100644
--- a/apps/api/internal/service/issue_view.go
+++ b/apps/api/internal/service/issue_view.go
@@ -48,6 +48,9 @@ func (s *IssueViewService) ensureProjectAccess(ctx context.Context, workspaceSlu
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/label.go b/apps/api/internal/service/label.go
index 9a3ec9a5..607de470 100644
--- a/apps/api/internal/service/label.go
+++ b/apps/api/internal/service/label.go
@@ -35,6 +35,9 @@ func (s *LabelService) ensureProjectAccess(ctx context.Context, workspaceSlug st
 	if !inWorkspace {
 		return uuid.Nil, ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return uuid.Nil, err
+	}
 	return wrk.ID, nil
 }
 
diff --git a/apps/api/internal/service/module.go b/apps/api/internal/service/module.go
index 1b6223f4..9cda28d9 100644
--- a/apps/api/internal/service/module.go
+++ b/apps/api/internal/service/module.go
@@ -55,6 +55,9 @@ func (s *ModuleService) ensureProjectAccess(ctx context.Context, workspaceSlug s
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/page.go b/apps/api/internal/service/page.go
index 2be5bb43..d665096e 100644
--- a/apps/api/internal/service/page.go
+++ b/apps/api/internal/service/page.go
@@ -123,6 +123,9 @@ func (s *PageService) ensureProjectAccess(ctx context.Context, workspaceSlug str
 	if !inWorkspace {
 		return ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.projectStore, s.ws, wrk.ID, projectID, userID); err != nil {
+		return err
+	}
 	return nil
 }
 
diff --git a/apps/api/internal/service/state.go b/apps/api/internal/service/state.go
index 3543417b..27f61632 100644
--- a/apps/api/internal/service/state.go
+++ b/apps/api/internal/service/state.go
@@ -47,6 +47,9 @@ func (s *StateService) ensureProjectAccess(ctx context.Context, workspaceSlug st
 	if !inWorkspace {
 		return uuid.Nil, ErrProjectNotFound
 	}
+	if err := enforceProjectVisibility(ctx, s.ps, s.ws, wrk.ID, projectID, userID); err != nil {
+		return uuid.Nil, err
+	}
 	return wrk.ID, nil
 }