diff --git a/web/handlers/server.go b/web/handlers/server.go
index deb6c39..b52a7ad 100644
--- a/web/handlers/server.go
+++ b/web/handlers/server.go
@@ -15,6 +15,7 @@ import (
 	"path/filepath"
 
 	"github.com/oy/openyield/web/store"
+	windowtypes "github.com/oy/openyield/x/window/types"
 )
 
 // Server bundles the mock store + per-page templates + route registration.
@@ -40,6 +41,16 @@ func New(s *store.Store, templatesDir string) (*Server, error) {
 			}
 			return grain / unit
 		},
+		"string": func(v any) string {
+			switch t := v.(type) {
+			case string:
+				return t
+			case windowtypes.WindowStatus:
+				return string(t)
+			default:
+				return ""
+			}
+		},
 	}
 	basePath := filepath.Join(templatesDir, "base.html")
 	base, err := template.New("base.html").Funcs(funcs).ParseFiles(basePath)
@@ -75,7 +86,8 @@ func New(s *store.Store, templatesDir string) (*Server, error) {
 func (s *Server) Register(mux *http.ServeMux) {
 	s.registerReach(mux)
 	s.registerStash(mux)
-	// P3..P5 register their own routes (window, standing, bloom).
+	s.registerWindow(mux)
+	// P4..P5 register their own routes (standing, bloom).
 }
 
 // render executes the named page template with the given data, writing HTML
diff --git a/web/handlers/window.go b/web/handlers/window.go
new file mode 100644
index 0000000..1d1d177
--- /dev/null
+++ b/web/handlers/window.go
@@ -0,0 +1,119 @@
+package handlers
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	windowtypes "github.com/oy/openyield/x/window/types"
+)
+
+// registerWindow wires the Window authorization routes (REQ-042) into the mux.
+func (s *Server) registerWindow(mux *http.ServeMux) {
+	mux.HandleFunc("GET /window", s.handleWindowList)
+	mux.HandleFunc("GET /window/new", s.handleWindowNew)
+	mux.HandleFunc("POST /window", s.handleWindowOpen)
+	mux.HandleFunc("GET /window/{id}", s.handleWindowDetail)
+	mux.HandleFunc("POST /window/{id}/activate", s.handleWindowActivate)
+	mux.HandleFunc("POST /window/{id}/revoke", s.handleWindowRevoke)
+	mux.HandleFunc("POST /window/{id}/expire", s.handleWindowExpire)
+}
+
+// handleWindowList renders all Windows for a grantor holder (defaults to
+// holder-alia if no query param, so the list view has something to show).
+func (s *Server) handleWindowList(w http.ResponseWriter, r *http.Request) {
+	grantor := r.URL.Query().Get("grantor")
+	if grantor == "" {
+		grantor = "holder-alia"
+	}
+	windows := s.Store.ListWindows(grantor)
+	s.render(w, "window_list.html", map[string]any{"Windows": windows, "Grantor": grantor})
+}
+
+// handleWindowNew renders the "Open a Window" form.
+func (s *Server) handleWindowNew(w http.ResponseWriter, r *http.Request) {
+	s.render(w, "window_new.html", nil)
+}
+
+// handleWindowOpen handles the POST from the "Open a Window" form. Calls
+// store.OpenWindow (creates a Window status=Open + an initial AuditEntry).
+func (s *Server) handleWindowOpen(w http.ResponseWriter, r *http.Request) {
+	grantor := r.FormValue("grantor_holder")
+	grantee := r.FormValue("grantee")
+	scopeKind := windowtypes.ScopeKind(r.FormValue("scope_kind"))
+	resourceID := r.FormValue("resource_id")
+	startStr := r.FormValue("start_unix")
+	endStr := r.FormValue("end_unix")
+	maxActionsStr := r.FormValue("max_actions")
+
+	if grantor == "" {
+		http.Error(w, "grantor holder is required", http.StatusBadRequest)
+		return
+	}
+	if grantee == "" {
+		http.Error(w, "grantee is required", http.StatusBadRequest)
+		return
+	}
+	start, _ := strconv.ParseInt(startStr, 10, 64)
+	end, _ := strconv.ParseInt(endStr, 10, 64)
+	if start == 0 {
+		start = time.Now().Unix()
+	}
+	if end == 0 {
+		end = start + 3600
+	}
+	maxActions, _ := strconv.ParseUint(maxActionsStr, 10, 32)
+	if maxActions == 0 {
+		maxActions = 10
+	}
+	scope := windowtypes.Scope{Kind: scopeKind, ResourceID: resourceID}
+	rateLimit := windowtypes.RateLimit{MaxActions: uint32(maxActions), PerDurationSeconds: 3600}
+	win, err := s.Store.OpenWindow(grantor, grantee, scope, start, end, rateLimit)
+	if err != nil {
+		http.Error(w, "could not open a Window: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	http.Redirect(w, r, "/window/"+win.WindowID, http.StatusFound)
+}
+
+// handleWindowDetail renders one Window + its lifecycle state + audit log.
+func (s *Server) handleWindowDetail(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	win, ok := s.Store.GetWindow(id)
+	if !ok {
+		http.NotFound(w, r)
+		return
+	}
+	auditLog := s.Store.GetAuditLog(id)
+	s.render(w, "window_detail.html", map[string]any{"Window": win, "AuditLog": auditLog})
+}
+
+// handleWindowActivate transitions Open → Active (calls Window.Activate).
+func (s *Server) handleWindowActivate(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	if err := s.Store.ActivateWindow(id); err != nil {
+		http.Error(w, "could not activate: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	http.Redirect(w, r, "/window/"+id, http.StatusSeeOther)
+}
+
+// handleWindowRevoke transitions to Revoked (calls Window.Revoke; idempotent).
+func (s *Server) handleWindowRevoke(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	if err := s.Store.RevokeWindow(id); err != nil {
+		http.Error(w, "could not revoke: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	http.Redirect(w, r, "/window/"+id, http.StatusSeeOther)
+}
+
+// handleWindowExpire transitions to Expired (calls Window.Expire).
+func (s *Server) handleWindowExpire(w http.ResponseWriter, r *http.Request) {
+	id := r.PathValue("id")
+	if err := s.Store.ExpireWindow(id); err != nil {
+		http.Error(w, "could not expire: "+err.Error(), http.StatusBadRequest)
+		return
+	}
+	http.Redirect(w, r, "/window/"+id, http.StatusSeeOther)
+}
diff --git a/web/handlers/window_test.go b/web/handlers/window_test.go
new file mode 100644
index 0000000..5a3fc83
--- /dev/null
+++ b/web/handlers/window_test.go
@@ -0,0 +1,363 @@
+package handlers
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	windowtypes "github.com/oy/openyield/x/window/types"
+)
+
+func TestWindowOpenCreatesWindowStatusOpen(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	body := "grantor_holder=holder-alia&grantee=service-1&scope_kind=ReadStash&resource_id=stash-holder-alia&max_actions=5"
+	req := httptest.NewRequest("POST", "/window", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusFound {
+		t.Fatalf("POST /window: status %d, want 302", rec.Code)
+	}
+	loc := rec.Header().Get("Location")
+	if !strings.HasPrefix(loc, "/window/window-") {
+		t.Errorf("POST /window: Location %q, want /window/window-...", loc)
+	}
+	// Extract the windowID and verify it exists with Status=Open + an initial AuditEntry.
+	windowID := strings.TrimPrefix(loc, "/window/")
+	win, ok := srv.Store.GetWindow(windowID)
+	if !ok {
+		t.Fatalf("POST /window: GetWindow(%q) miss", windowID)
+	}
+	if win.Status != windowtypes.StatusOpen {
+		t.Errorf("POST /window: created Window status %q, want Open", win.Status)
+	}
+	audit := srv.Store.GetAuditLog(windowID)
+	if len(audit) != 1 {
+		t.Errorf("POST /window: audit log len %d, want 1 (initial entry)", len(audit))
+	}
+	if audit[0].Action != "open" {
+		t.Errorf("POST /window: initial audit action %q, want open", audit[0].Action)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowActivateTransitionsOpenToActive(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, err := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	if err != nil {
+		t.Fatalf("OpenWindow: %v", err)
+	}
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("POST", "/window/"+win.WindowID+"/activate", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("POST activate: status %d, want 303", rec.Code)
+	}
+	// Lifecycle correctness: assert the real Window.Activate() was invoked
+	// (the handler calls store.ActivateWindow which calls w.Activate()).
+	updated, ok := srv.Store.GetWindow(win.WindowID)
+	if !ok {
+		t.Fatal("window missing after activate")
+	}
+	if updated.Status != windowtypes.StatusActive {
+		t.Errorf("after activate: status %q, want Active (Window.Activate was NOT invoked)", updated.Status)
+	}
+	audit := srv.Store.GetAuditLog(win.WindowID)
+	if len(audit) != 2 {
+		t.Errorf("after activate: audit log len %d, want 2 (initial + activate)", len(audit))
+	}
+	if audit[1].Action != "activate" {
+		t.Errorf("after activate: audit[1].Action %q, want activate", audit[1].Action)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowRevokeTransitionsToRevoked(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	_ = srv.Store.ActivateWindow(win.WindowID)
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("POST", "/window/"+win.WindowID+"/revoke", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("POST revoke: status %d, want 303", rec.Code)
+	}
+	updated, _ := srv.Store.GetWindow(win.WindowID)
+	if updated.Status != windowtypes.StatusRevoked {
+		t.Errorf("after revoke: status %q, want Revoked (Window.Revoke was NOT invoked)", updated.Status)
+	}
+	if !updated.Revoked {
+		t.Errorf("after revoke: Revoked flag false, want true")
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowRevokeIdempotentOnAlreadyRevoked(t *testing.T) {
+	srv := newTestServer(t)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	_ = srv.Store.ActivateWindow(win.WindowID)
+	_ = srv.Store.RevokeWindow(win.WindowID)
+	auditBefore := len(srv.Store.GetAuditLog(win.WindowID))
+
+	// Second revoke is a no-op (idempotent): no new AuditEntry.
+	_ = srv.Store.RevokeWindow(win.WindowID)
+	auditAfter := len(srv.Store.GetAuditLog(win.WindowID))
+	if auditAfter != auditBefore {
+		t.Errorf("idempotent revoke: audit log grew %d -> %d (revoke on already-revoked must be a no-op)", auditBefore, auditAfter)
+	}
+}
+
+func TestWindowRevokeOnExpiredIsNoOp(t *testing.T) {
+	srv := newTestServer(t)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	_ = srv.Store.ActivateWindow(win.WindowID)
+	_ = srv.Store.ExpireWindow(win.WindowID)
+	auditBefore := len(srv.Store.GetAuditLog(win.WindowID))
+
+	// Revoke on an Expired window is a no-op (Expired is terminal — v0.2 contract).
+	_ = srv.Store.RevokeWindow(win.WindowID)
+	updated, _ := srv.Store.GetWindow(win.WindowID)
+	if updated.Status != windowtypes.StatusExpired {
+		t.Errorf("revoke-on-expired: status %q, want Expired (terminal state must win)", updated.Status)
+	}
+	auditAfter := len(srv.Store.GetAuditLog(win.WindowID))
+	if auditAfter != auditBefore {
+		t.Errorf("revoke-on-expired: audit log grew %d -> %d (must be a no-op)", auditBefore, auditAfter)
+	}
+}
+
+func TestWindowExpireTransitionsToExpired(t *testing.T) {
+	srv := newTestServer(t)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	_ = srv.Store.ActivateWindow(win.WindowID)
+
+	_ = srv.Store.ExpireWindow(win.WindowID)
+	updated, _ := srv.Store.GetWindow(win.WindowID)
+	if updated.Status != windowtypes.StatusExpired {
+		t.Errorf("after expire: status %q, want Expired (Window.Expire was NOT invoked)", updated.Status)
+	}
+}
+
+func TestWindowDetailRendersLifecycleAndAuditLog(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	_ = srv.Store.ActivateWindow(win.WindowID)
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/window/"+win.WindowID, nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("GET /window/%s: status %d, want 200", win.WindowID, rec.Code)
+	}
+	body := rec.Body.String()
+	if !strings.Contains(body, "Active") {
+		t.Errorf("detail: body missing Active badge")
+	}
+	if !strings.Contains(body, "activate") {
+		t.Errorf("detail: body missing activate audit-log entry")
+	}
+	if !strings.Contains(body, "open") {
+		t.Errorf("detail: body missing open audit-log entry")
+	}
+	assertNoBannedTerms(t, body)
+}
+
+func TestWindowDetailMissingReturns404(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/window/window-nobody", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusNotFound {
+		t.Fatalf("GET /window/window-nobody: status %d, want 404", rec.Code)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowOpenEmptyGrantorReturns400(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	body := "grantor_holder=&grantee=service-1&scope_kind=ReadStash"
+	req := httptest.NewRequest("POST", "/window", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("POST /window empty grantor: status %d, want 400", rec.Code)
+	}
+	// G-026: rendered-HTML lexicon check on the ERROR response body too.
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+// Compile-time assertion that the handler uses the real x/window/types struct
+// (D-067: the UI grounds in the real Go type definitions).
+var _ windowtypes.Window
+
+func TestWindowListRendersSeededEmpty(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/window", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("GET /window: status %d, want 200", rec.Code)
+	}
+	body := rec.Body.String()
+	// No windows yet for holder-alia (fresh store) -> empty message.
+	if !strings.Contains(body, "Open a Window") {
+		t.Errorf("GET /window: body missing 'Open a Window' link")
+	}
+	assertNoBannedTerms(t, body)
+}
+
+func TestWindowListRendersCreatedWindows(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 5, PerDurationSeconds: 3600}
+	w, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/window", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("GET /window: status %d, want 200", rec.Code)
+	}
+	body := rec.Body.String()
+	if !strings.Contains(body, w.WindowID) {
+		t.Errorf("GET /window: body missing created window %s", w.WindowID)
+	}
+	if !strings.Contains(body, "service-1") {
+		t.Errorf("GET /window: body missing grantee service-1")
+	}
+	assertNoBannedTerms(t, body)
+}
+
+func TestWindowNewRendersForm(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("GET", "/window/new", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("GET /window/new: status %d, want 200", rec.Code)
+	}
+	body := rec.Body.String()
+	if !strings.Contains(body, "Open a Window") {
+		t.Errorf("GET /window/new: body missing 'Open a Window' label")
+	}
+	if !strings.Contains(body, "ReadStash") {
+		t.Errorf("GET /window/new: body missing ScopeKind option ReadStash")
+	}
+	if !strings.Contains(body, "ProcessPassActForStand") {
+		t.Errorf("GET /window/new: body missing ScopeKind option ProcessPassActForStand")
+	}
+	assertNoBannedTerms(t, body)
+}
+
+func TestWindowOpenEmptyGranteeReturns400(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	body := "grantor_holder=holder-alia&grantee=&scope_kind=ReadStash"
+	req := httptest.NewRequest("POST", "/window", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("POST /window empty grantee: status %d, want 400", rec.Code)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowActivateNotFoundReturns400(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("POST", "/window/window-nobody/activate", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("POST activate nobody: status %d, want 400", rec.Code)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowRevokeNotFoundReturns400(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("POST", "/window/window-nobody/revoke", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("POST revoke nobody: status %d, want 400", rec.Code)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowExpireNotFoundReturns400(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("POST", "/window/window-nobody/expire", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("POST expire nobody: status %d, want 400", rec.Code)
+	}
+	assertNoBannedTerms(t, rec.Body.String())
+}
+
+func TestWindowRevokeAndExpireHandlersRedirect(t *testing.T) {
+	srv := newTestServer(t)
+	mux := http.NewServeMux()
+	srv.Register(mux)
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-holder-alia"}
+	rl := windowtypes.RateLimit{MaxActions: 10, PerDurationSeconds: 3600}
+	win, _ := srv.Store.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	_ = srv.Store.ActivateWindow(win.WindowID)
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest("POST", "/window/"+win.WindowID+"/revoke", nil)
+	mux.ServeHTTP(rec, req)
+	if rec.Code != http.StatusSeeOther {
+		t.Fatalf("POST revoke: status %d, want 303", rec.Code)
+	}
+
+	// Expire on a revoked window: revoked is not terminal for expire, so it
+	// transitions to Expired (Window.Expire sets status unconditionally).
+	rec2 := httptest.NewRecorder()
+	req2 := httptest.NewRequest("POST", "/window/"+win.WindowID+"/expire", nil)
+	mux.ServeHTTP(rec2, req2)
+	if rec2.Code != http.StatusSeeOther {
+		t.Fatalf("POST expire: status %d, want 303", rec2.Code)
+	}
+}
diff --git a/web/store/store.go b/web/store/store.go
index 4d6db21..b43a6f6 100644
--- a/web/store/store.go
+++ b/web/store/store.go
@@ -15,6 +15,7 @@ import (
 
 	identitytypes "github.com/oy/openyield/x/identity/types"
 	stashtypes "github.com/oy/openyield/x/stash/types"
+	windowtypes "github.com/oy/openyield/x/window/types"
 )
 
 // seedBalanceGrain is the test balance seeded to a new Stash at signup (D-071
@@ -27,6 +28,8 @@ type Store struct {
 	reaches         map[string]identitytypes.Reach
 	stashes         map[string]stashtypes.Stash
 	stashActivities map[string]stashtypes.StashActivity
+	windows         map[string]windowtypes.Window
+	auditLogs       map[string][]windowtypes.AuditEntry
 }
 
 // NewStore constructs a Store seeded from fixtures (fixtures.go).
@@ -35,6 +38,8 @@ func NewStore() *Store {
 		reaches:         map[string]identitytypes.Reach{},
 		stashes:         map[string]stashtypes.Stash{},
 		stashActivities: map[string]stashtypes.StashActivity{},
+		windows:         map[string]windowtypes.Window{},
+		auditLogs:       map[string][]windowtypes.AuditEntry{},
 	}
 	s.seed()
 	return s
@@ -117,6 +122,148 @@ func (s *Store) GetStashActivity(stashID string) (stashtypes.StashActivity, bool
 	return a, ok
 }
 
+// OpenWindow creates a new Window in the Open status (REQ-042) with an initial
+// AuditEntry. Returns the created Window. The Window is keyed by a generated
+// windowID derived from the grantor + a counter (mock; not cryptographic).
+func (s *Store) OpenWindow(grantorHolder, grantee string, scope windowtypes.Scope, start, end int64, rateLimit windowtypes.RateLimit) (windowtypes.Window, error) {
+	if grantorHolder == "" {
+		return windowtypes.Window{}, fmt.Errorf("grantor holder is required")
+	}
+	if grantee == "" {
+		return windowtypes.Window{}, fmt.Errorf("grantee is required")
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	windowID := fmt.Sprintf("window-%s-%d", grantorHolder, len(s.windows)+1)
+	now := time.Now().Unix()
+	w := windowtypes.Window{
+		WindowID:      windowID,
+		GrantorHolder: grantorHolder,
+		Grantee:       grantee,
+		Scope:         scope,
+		Start:         start,
+		End:           end,
+		RateLimit:     rateLimit,
+		Status:        windowtypes.StatusOpen,
+	}
+	s.windows[windowID] = w
+	entry := windowtypes.AuditEntry{
+		EntryID:    windowID + "-audit-1",
+		Timestamp:  now,
+		Action:     "open",
+		Result:     "created",
+		GranterRef: grantorHolder,
+	}
+	s.auditLogs[windowID] = []windowtypes.AuditEntry{entry}
+	w.AuditLogRefs = []string{entry.EntryID}
+	s.windows[windowID] = w
+	return w, nil
+}
+
+// ActivateWindow transitions a Window from Open to Active by calling the real
+// x/window/types.Window.Activate() method (not a reimplementation). Appends an
+// AuditEntry. Returns an error if the Window is not in the Open status.
+func (s *Store) ActivateWindow(windowID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	w, ok := s.windows[windowID]
+	if !ok {
+		return fmt.Errorf("window %q not found", windowID)
+	}
+	if err := w.Activate(); err != nil {
+		return err
+	}
+	s.windows[windowID] = w
+	s.appendAuditLocked(windowID, "activate", "active", w.GrantorHolder)
+	return nil
+}
+
+// RevokeWindow transitions a Window to Revoked by calling the real
+// x/window/types.Window.Revoke() method. Idempotent on already-revoked;
+// no-op on Expired (terminal state wins — v0.2 type contract). Appends an
+// AuditEntry only if the status actually changed.
+func (s *Store) RevokeWindow(windowID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	w, ok := s.windows[windowID]
+	if !ok {
+		return fmt.Errorf("window %q not found", windowID)
+	}
+	prevStatus := w.Status
+	if err := w.Revoke(); err != nil {
+		return err
+	}
+	s.windows[windowID] = w
+	if w.Status != prevStatus {
+		s.appendAuditLocked(windowID, "revoke", "revoked", w.GrantorHolder)
+	}
+	return nil
+}
+
+// ExpireWindow transitions a Window to Expired by calling the real
+// x/window/types.Window.Expire() method. Appends an AuditEntry.
+func (s *Store) ExpireWindow(windowID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	w, ok := s.windows[windowID]
+	if !ok {
+		return fmt.Errorf("window %q not found", windowID)
+	}
+	prevStatus := w.Status
+	w.Expire()
+	s.windows[windowID] = w
+	if w.Status != prevStatus {
+		s.appendAuditLocked(windowID, "expire", "expired", w.GrantorHolder)
+	}
+	return nil
+}
+
+// ListWindows returns all Windows for a grantor holder.
+func (s *Store) ListWindows(grantorHolder string) []windowtypes.Window {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	out := []windowtypes.Window{}
+	for _, w := range s.windows {
+		if w.GrantorHolder == grantorHolder {
+			out = append(out, w)
+		}
+	}
+	return out
+}
+
+// GetWindow returns the Window for a windowID.
+func (s *Store) GetWindow(windowID string) (windowtypes.Window, bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	w, ok := s.windows[windowID]
+	return w, ok
+}
+
+// GetAuditLog returns the audit-log entries for a windowID.
+func (s *Store) GetAuditLog(windowID string) []windowtypes.AuditEntry {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.auditLogs[windowID]
+}
+
+// appendAuditLocked appends an AuditEntry to the window's audit log. Caller
+// MUST hold s.mu.
+func (s *Store) appendAuditLocked(windowID, action, result, granterRef string) {
+	logs := s.auditLogs[windowID]
+	now := time.Now().Unix()
+	entry := windowtypes.AuditEntry{
+		EntryID:    fmt.Sprintf("%s-audit-%d", windowID, len(logs)+1),
+		Timestamp:  now,
+		Action:     action,
+		Result:     result,
+		GranterRef: granterRef,
+	}
+	s.auditLogs[windowID] = append(logs, entry)
+	w := s.windows[windowID]
+	w.AuditLogRefs = append(w.AuditLogRefs, entry.EntryID)
+	s.windows[windowID] = w
+}
+
 // validateReachInput enforces G-027: HolderID and PublicKey must be non-empty,
 // <=128 bytes, and contain no path separators or template syntax. This is a
 // prototype-robustness gate (the mock store uses holderID as a map key).
diff --git a/web/store/store_test.go b/web/store/store_test.go
index 13a863a..6d2405b 100644
--- a/web/store/store_test.go
+++ b/web/store/store_test.go
@@ -6,6 +6,7 @@ import (
 
 	identitytypes "github.com/oy/openyield/x/identity/types"
 	stashtypes "github.com/oy/openyield/x/stash/types"
+	windowtypes "github.com/oy/openyield/x/window/types"
 )
 
 func TestNewStoreSeedsFixtures(t *testing.T) {
@@ -214,3 +215,222 @@ func stringOf(r rune, n int) string {
 	}
 	return string(b)
 }
+
+// --- Window tests (P3) ---
+
+func TestOpenWindowCreatesStatusOpenWithInitialAudit(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash, ResourceID: "stash-x"}
+	rl := windowtypes.RateLimit{MaxActions: 5, PerDurationSeconds: 3600}
+	w, err := s.OpenWindow("holder-alia", "service-1", scope, 1000, 2000, rl)
+	if err != nil {
+		t.Fatalf("OpenWindow: %v", err)
+	}
+	if w.Status != windowtypes.StatusOpen {
+		t.Errorf("OpenWindow status %q, want Open", w.Status)
+	}
+	if w.WindowID == "" {
+		t.Error("OpenWindow: empty WindowID")
+	}
+	audit := s.GetAuditLog(w.WindowID)
+	if len(audit) != 1 {
+		t.Errorf("OpenWindow: audit log len %d, want 1", len(audit))
+	}
+	if audit[0].Action != "open" {
+		t.Errorf("OpenWindow: audit[0].Action %q, want open", audit[0].Action)
+	}
+}
+
+func TestOpenWindowValidation(t *testing.T) {
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	cases := []struct {
+		name, grantor, grantee string
+		wantErr                bool
+	}{
+		{"empty grantor", "", "g", true},
+		{"empty grantee", "h", "", true},
+		{"valid", "h", "g", false},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			s := NewStore()
+			_, err := s.OpenWindow(c.grantor, c.grantee, scope, 1, 2, rl)
+			if c.wantErr && err == nil {
+				t.Errorf("expected error, got nil")
+			}
+			if !c.wantErr && err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+		})
+	}
+}
+
+func TestActivateWindowTransitionsToActive(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	if err := s.ActivateWindow(w.WindowID); err != nil {
+		t.Fatalf("ActivateWindow: %v", err)
+	}
+	updated, _ := s.GetWindow(w.WindowID)
+	if updated.Status != windowtypes.StatusActive {
+		t.Errorf("after activate: %q, want Active", updated.Status)
+	}
+	audit := s.GetAuditLog(w.WindowID)
+	if len(audit) != 2 {
+		t.Errorf("after activate: audit len %d, want 2", len(audit))
+	}
+}
+
+func TestActivateWindowNotFound(t *testing.T) {
+	s := NewStore()
+	if err := s.ActivateWindow("window-nobody"); err == nil {
+		t.Error("ActivateWindow(nobody): expected error, got nil")
+	}
+}
+
+func TestActivateWindowOnActiveFails(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	_ = s.ActivateWindow(w.WindowID)
+	// Activate again should fail (can only activate Open windows).
+	if err := s.ActivateWindow(w.WindowID); err == nil {
+		t.Error("activate on Active: expected error, got nil (Window.Activate rejects non-Open)")
+	}
+}
+
+func TestRevokeWindowTransitionsToRevoked(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	if err := s.RevokeWindow(w.WindowID); err != nil {
+		t.Fatalf("RevokeWindow: %v", err)
+	}
+	updated, _ := s.GetWindow(w.WindowID)
+	if updated.Status != windowtypes.StatusRevoked {
+		t.Errorf("after revoke: %q, want Revoked", updated.Status)
+	}
+	if !updated.Revoked {
+		t.Error("after revoke: Revoked flag false, want true")
+	}
+}
+
+func TestRevokeWindowIdempotent(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	_ = s.RevokeWindow(w.WindowID)
+	before := len(s.GetAuditLog(w.WindowID))
+	_ = s.RevokeWindow(w.WindowID)
+	after := len(s.GetAuditLog(w.WindowID))
+	if after != before {
+		t.Errorf("idempotent revoke: audit grew %d -> %d", before, after)
+	}
+}
+
+func TestRevokeWindowOnExpiredIsNoOp(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	_ = s.ExpireWindow(w.WindowID)
+	before := len(s.GetAuditLog(w.WindowID))
+	_ = s.RevokeWindow(w.WindowID)
+	updated, _ := s.GetWindow(w.WindowID)
+	if updated.Status != windowtypes.StatusExpired {
+		t.Errorf("revoke-on-expired: %q, want Expired (terminal wins)", updated.Status)
+	}
+	after := len(s.GetAuditLog(w.WindowID))
+	if after != before {
+		t.Errorf("revoke-on-expired: audit grew %d -> %d (no-op)", before, after)
+	}
+}
+
+func TestRevokeWindowNotFound(t *testing.T) {
+	s := NewStore()
+	if err := s.RevokeWindow("window-nobody"); err == nil {
+		t.Error("RevokeWindow(nobody): expected error, got nil")
+	}
+}
+
+func TestExpireWindowTransitionsToExpired(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	if err := s.ExpireWindow(w.WindowID); err != nil {
+		t.Fatalf("ExpireWindow: %v", err)
+	}
+	updated, _ := s.GetWindow(w.WindowID)
+	if updated.Status != windowtypes.StatusExpired {
+		t.Errorf("after expire: %q, want Expired", updated.Status)
+	}
+}
+
+func TestExpireWindowNotFound(t *testing.T) {
+	s := NewStore()
+	if err := s.ExpireWindow("window-nobody"); err == nil {
+		t.Error("ExpireWindow(nobody): expected error, got nil")
+	}
+}
+
+func TestExpireWindowIdempotent(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	_ = s.ExpireWindow(w.WindowID)
+	before := len(s.GetAuditLog(w.WindowID))
+	_ = s.ExpireWindow(w.WindowID)
+	after := len(s.GetAuditLog(w.WindowID))
+	if after != before {
+		t.Errorf("idempotent expire: audit grew %d -> %d", before, after)
+	}
+}
+
+func TestListWindowsFiltersByGrantor(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	_, _ = s.OpenWindow("holder-alia", "svc1", scope, 1, 2, rl)
+	_, _ = s.OpenWindow("holder-alia", "svc2", scope, 1, 2, rl)
+	_, _ = s.OpenWindow("holder-bryn", "svc3", scope, 1, 2, rl)
+	alia := s.ListWindows("holder-alia")
+	if len(alia) != 2 {
+		t.Errorf("ListWindows(holder-alia) = %d, want 2", len(alia))
+	}
+	bryn := s.ListWindows("holder-bryn")
+	if len(bryn) != 1 {
+		t.Errorf("ListWindows(holder-bryn) = %d, want 1", len(bryn))
+	}
+	nobody := s.ListWindows("nobody")
+	if len(nobody) != 0 {
+		t.Errorf("ListWindows(nobody) = %d, want 0", len(nobody))
+	}
+}
+
+func TestGetWindowHitMiss(t *testing.T) {
+	s := NewStore()
+	scope := windowtypes.Scope{Kind: windowtypes.ScopeReadStash}
+	rl := windowtypes.RateLimit{MaxActions: 1}
+	w, _ := s.OpenWindow("holder-alia", "svc", scope, 1, 2, rl)
+	if _, ok := s.GetWindow(w.WindowID); !ok {
+		t.Errorf("GetWindow(%q) miss, want hit", w.WindowID)
+	}
+	if _, ok := s.GetWindow("window-nobody"); ok {
+		t.Error("GetWindow(nobody) hit, want miss")
+	}
+}
+
+func TestGetAuditLogEmptyForMissing(t *testing.T) {
+	s := NewStore()
+	if logs := s.GetAuditLog("window-nobody"); logs != nil {
+		t.Errorf("GetAuditLog(nobody) = %v, want nil", logs)
+	}
+}
diff --git a/web/templates/window_detail.html b/web/templates/window_detail.html
new file mode 100644
index 0000000..d370ef0
--- /dev/null
+++ b/web/templates/window_detail.html
@@ -0,0 +1,68 @@
+{{define "title"}}{{.Window.WindowID}} — OpenYield{{end}}
+
+{{define "content"}}
+<section class="panel">
+  <h1>{{.Window.WindowID}}</h1>
+  <table class="kv">
+    <tr><th>Window ID</th><td>{{.Window.WindowID}}</td></tr>
+    <tr><th>Grantor</th><td>{{.Window.GrantorHolder}}</td></tr>
+    <tr><th>Grantee</th><td>{{.Window.Grantee}}</td></tr>
+    <tr><th>Scope</th><td>{{.Window.Scope.Kind}} ({{.Window.Scope.ResourceID}})</td></tr>
+    <tr><th>Start</th><td>{{.Window.Start}}</td></tr>
+    <tr><th>End</th><td>{{.Window.End}}</td></tr>
+    <tr><th>Rate limit</th><td>{{.Window.RateLimit.ActionsConsumed}} / {{.Window.RateLimit.MaxActions}} per {{.Window.RateLimit.PerDurationSeconds}}s</td></tr>
+    <tr><th>Revoked</th><td>{{if .Window.Revoked}}yes{{else}}no{{end}}</td></tr>
+    <tr><th>Status</th><td>
+      {{if eq (string .Window.Status) "Open"}}<span class="badge amber">Open</span>{{end}}
+      {{if eq (string .Window.Status) "Active"}}<span class="badge green">Active</span>{{end}}
+      {{if eq (string .Window.Status) "Revoked"}}<span class="badge red">Revoked</span>{{end}}
+      {{if eq (string .Window.Status) "Expired"}}<span class="badge grey">Expired</span>{{end}}
+    </td></tr>
+  </table>
+</section>
+
+<section class="panel">
+  <h2>Lifecycle actions</h2>
+  <p>
+    {{if eq (string .Window.Status) "Open"}}
+    <form method="POST" action="/window/{{.Window.WindowID}}/activate" style="display:inline">
+      <button type="submit">Activate</button>
+    </form>
+    {{end}}
+    {{if or (eq (string .Window.Status) "Open") (eq (string .Window.Status) "Active")}}
+    <form method="POST" action="/window/{{.Window.WindowID}}/revoke" style="display:inline">
+      <button type="submit">Revoke</button>
+    </form>
+    {{end}}
+    {{if or (eq (string .Window.Status) "Open") (eq (string .Window.Status) "Active")}}
+    <form method="POST" action="/window/{{.Window.WindowID}}/expire" style="display:inline">
+      <button type="submit">Expire</button>
+    </form>
+    {{end}}
+  </p>
+</section>
+
+<section class="panel">
+  <h2>Audit log</h2>
+  {{if .AuditLog}}
+  <table>
+    <thead><tr><th>Entry ID</th><th>Timestamp</th><th>Action</th><th>Result</th><th>Granter</th></tr></thead>
+    <tbody>
+    {{range .AuditLog}}
+      <tr>
+        <td>{{.EntryID}}</td>
+        <td>{{.Timestamp}}</td>
+        <td>{{.Action}}</td>
+        <td>{{.Result}}</td>
+        <td>{{.GranterRef}}</td>
+      </tr>
+    {{end}}
+    </tbody>
+  </table>
+  {{else}}
+  <p>No audit entries yet.</p>
+  {{end}}
+</section>
+
+<p><a href="/window">Back to Window list</a></p>
+{{end}}
\ No newline at end of file
diff --git a/web/templates/window_list.html b/web/templates/window_list.html
new file mode 100644
index 0000000..32a15a6
--- /dev/null
+++ b/web/templates/window_list.html
@@ -0,0 +1,33 @@
+{{define "title"}}Window — OpenYield{{end}}
+
+{{define "content"}}
+<section class="panel">
+  <h1>Window</h1>
+  <p>A Window is a Holder-authorized, scope-bounded, time-limited, revocable
+    delegation of access (REQ-015). The Holder opens a Window so a partner or
+    service can read a Stash or process a Pass-Act — without giving up custody.
+    The Window is revocable, rate-limited, and audited.</p>
+  <p><a href="/window/new" class="btn">Open a Window</a></p>
+</section>
+
+<section class="panel">
+  <h2>Windows for {{.Grantor}}</h2>
+  {{if .Windows}}
+  <table>
+    <thead><tr><th>Window ID</th><th>Grantee</th><th>Scope</th><th>Status</th></tr></thead>
+    <tbody>
+    {{range .Windows}}
+      <tr>
+        <td><a href="/window/{{.WindowID}}">{{.WindowID}}</a></td>
+        <td>{{.Grantee}}</td>
+        <td>{{.Scope.Kind}} ({{.Scope.ResourceID}})</td>
+        <td>{{.Status}}</td>
+      </tr>
+    {{end}}
+    </tbody>
+  </table>
+  {{else}}
+  <p>No Windows yet for {{.Grantor}}. <a href="/window/new">Open a Window</a> to begin.</p>
+  {{end}}
+</section>
+{{end}}
\ No newline at end of file
diff --git a/web/templates/window_new.html b/web/templates/window_new.html
new file mode 100644
index 0000000..ea7bb70
--- /dev/null
+++ b/web/templates/window_new.html
@@ -0,0 +1,36 @@
+{{define "title"}}Open a Window — OpenYield{{end}}
+
+{{define "content"}}
+<section class="panel">
+  <h1>Open a Window</h1>
+  <p>A Window delegates scoped access to a partner or service without giving
+    up custody. The Holder sets the scope, the duration, and a rate-limit; the
+    Window is revocable at any time.</p>
+
+  <form method="POST" action="/window" hx-post="/window" hx-target="body">
+    <label for="grantor_holder">Grantor Holder ID</label>
+    <input type="text" id="grantor_holder" name="grantor_holder" required
+           maxlength="128" placeholder="the Holder opening the Window">
+    <label for="grantee">Grantee</label>
+    <input type="text" id="grantee" name="grantee" required
+           maxlength="128" placeholder="the partner or service receiving access">
+    <label for="scope_kind">Scope kind</label>
+    <select id="scope_kind" name="scope_kind">
+      <option value="ReadStash">ReadStash</option>
+      <option value="ReadStanding">ReadStanding</option>
+      <option value="ProcessPassActForStand">ProcessPassActForStand</option>
+    </select>
+    <label for="resource_id">Resource ID</label>
+    <input type="text" id="resource_id" name="resource_id"
+           maxlength="128" placeholder="the Stash or Stand this Window scopes to">
+    <label for="start_unix">Start (unix seconds, blank = now)</label>
+    <input type="number" id="start_unix" name="start_unix" placeholder="blank = now">
+    <label for="end_unix">End (unix seconds, blank = now+1h)</label>
+    <input type="number" id="end_unix" name="end_unix" placeholder="blank = now+1h">
+    <label for="max_actions">Max actions (rate-limit, blank = 10)</label>
+    <input type="number" id="max_actions" name="max_actions" placeholder="10">
+    <button type="submit">Open a Window</button>
+  </form>
+  <p><a href="/window">Back to Window list</a></p>
+</section>
+{{end}}
\ No newline at end of file