diff --git a/request.go b/request.go
index f5a02d1..6a82415 100644
--- a/request.go
+++ b/request.go
@@ -84,7 +84,8 @@ const (
 	termSendFailed terminateReason = iota
 	termCloseSent
 	termReceivedClosed
-	termExternal
+	termDone
+	termCancelled
 )
 
 // ----------------------------------------------------------------------------
@@ -178,9 +179,33 @@ func (m *RequestManager) Query(
 	return
 }
 
+func (m *RequestManager) Cancel(id string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	req, ok := m.reqs[id]
+	if !ok {
+		return fmt.Errorf("Cancel: unknown id %q", id)
+	}
+
+	if sess, ok := m.sessions[id]; ok {
+		sess.Close()
+	}
+
+	req.once.Do(func() {
+		close(req.buffer)
+		close(req.closed)
+	})
+	delete(m.reqs, id)
+
+	return nil
+}
+
 func (m *RequestManager) Close() {
 	m.cancel()
 	m.wg.Wait()
+	// call session.Close for each open session
+	// manually deregister and close each registered request.
 }
 
 func (m *RequestManager) spawnSession(req *request) {
@@ -356,10 +381,11 @@ func (s *session) run() {
 				return
 			}
 		case <-s.done:
-			s.terminate(termExternal)
+			s.terminate(termDone)
 			return
 		case <-s.ctx.Done():
-			s.terminate(termExternal)
+			s.send(envelope.EncloseClose(s.id))
+			s.terminate(termCancelled)
 			return
 		case <-s.eose:
 			if s.closeOnEOSE {
diff --git a/request_test.go b/request_test.go
index 0db27fe..d39ee65 100644
--- a/request_test.go
+++ b/request_test.go
@@ -142,11 +142,11 @@ func TestRequestManager_Session(t *testing.T) {
 		Eventually(t, func() bool {
 			select {
 			case r := <-h.terminatedWith:
-				return r == termExternal
+				return r == termDone
 			default:
 				return false
 			}
-		}, "expected termExternal after done closed")
+		}, "expected termDone after done closed")
 	})
 
 	t.Run("terminates on context cancel", func(t *testing.T) {
@@ -170,11 +170,11 @@ func TestRequestManager_Session(t *testing.T) {
 		Eventually(t, func() bool {
 			select {
 			case r := <-h.terminatedWith:
-				return r == termExternal
+				return r == termCancelled
 			default:
 				return false
 			}
-		}, "expected termExternal after context cancel")
+		}, "expected termCancelled after context cancel")
 	})
 
 	t.Run("terminates on closed signal", func(t *testing.T) {
@@ -408,12 +408,84 @@ func TestRequestManager_Stream(t *testing.T) {
 
 func TestRequestManager_Cancel(t *testing.T) {
 	t.Run("sends close, terminates session, deregisters", func(t *testing.T) {
-		// connect, call Stream, hold the id
-		// call Cancel(id)
-		// assert mock send was called with a CLOSE envelope for the id
-		// assert the session is removed from sessions
-		// assert the registration is removed from reqs
-		// assert the caller's events channel eventually closes
+		p, envoy := newMockEnvoy(t)
+		p.connect()
+		Eventually(t, envoy.IsConnected, "envoy should be connected")
+
+		m := NewRequestManager(envoy)
+		filters := [][]byte{[]byte(`{}`)}
+		id, events, _ := m.Stream(filters)
+
+		// drain the REQ send
+		Eventually(t, func() bool {
+			select {
+			case <-p.sent:
+				return true
+			default:
+				return false
+			}
+		}, "expected REQ send")
+
+		err := m.Cancel(id)
+		assert.NoError(t, err)
+
+		var got []byte
+		Eventually(t, func() bool {
+			select {
+			case got = <-p.sent:
+				return true
+			default:
+				return false
+			}
+		}, "expected CLOSE send")
+		assert.Equal(t, []byte(envelope.EncloseClose(id)), got)
+
+		Eventually(t, func() bool {
+			m.mu.RLock()
+			_, ok := m.sessions[id]
+			m.mu.RUnlock()
+			return !ok
+		}, "session should be removed")
+
+		m.mu.RLock()
+		_, ok := m.reqs[id]
+		m.mu.RUnlock()
+		assert.False(t, ok, "registration should be removed from reqs")
+
+		Eventually(t, func() bool {
+			select {
+			case _, ok := <-events:
+				return !ok
+			default:
+				return false
+			}
+		}, "events channel should close after cancel")
+	})
+
+	t.Run("deregisters when no session is active", func(t *testing.T) {
+		_, envoy := newMockEnvoy(t)
+		// do not connect — no session will be spawned
+
+		m := NewRequestManager(envoy)
+		filters := [][]byte{[]byte(`{}`)}
+		id, events, _ := m.Stream(filters)
+
+		err := m.Cancel(id)
+		assert.NoError(t, err)
+
+		m.mu.RLock()
+		_, ok := m.reqs[id]
+		m.mu.RUnlock()
+		assert.False(t, ok, "registration should be removed from reqs")
+
+		Eventually(t, func() bool {
+			select {
+			case _, ok := <-events:
+				return !ok
+			default:
+				return false
+			}
+		}, "events channel should close after cancel")
 	})
 
 	t.Run("returns error for unknown id", func(t *testing.T) {
@@ -532,10 +604,13 @@ func TestRequestManager_Close(t *testing.T) {
 		// assert all sessions are terminated (sessions map empty)
 	})
 
-	t.Run("does not deregister requests on close", func(t *testing.T) {
+	t.Run("deregisters all requests on close", func(t *testing.T) {
 		// connect, open two streams
 		// call manager.Close()
-		// assert registrations remain in reqs
-		// termExternal does not deregister; that is the caller's domain via Cancel
+		// -- calls session.Close for each registration
+		// -- manually cleans up the rest
+		// all sessions are stopped
+		// all request registrations are removed
+		// all registration channels close
 	})
 }