diff --git a/platform/internal/handlers/handlers_extended_test.go b/platform/internal/handlers/handlers_extended_test.go
index 68df80ed..1e6f3a53 100644
--- a/platform/internal/handlers/handlers_extended_test.go
+++ b/platform/internal/handlers/handlers_extended_test.go
@@ -73,6 +73,11 @@ func TestExtended_WorkspaceUpdate(t *testing.T) {
 	broadcaster := newTestBroadcaster()
 	handler := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", "/tmp/configs")
 
+	// #120 fix: existence check runs first — workspace must be found before updates proceed.
+	mock.ExpectQuery("SELECT EXISTS").
+		WithArgs("ws-upd").
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(true))
+
 	// Expect name update
 	mock.ExpectExec("UPDATE workspaces SET name").
 		WithArgs("ws-upd", "New Name").
@@ -110,6 +115,48 @@ func TestExtended_WorkspaceUpdate(t *testing.T) {
 	}
 }
 
+// TestExtended_WorkspaceUpdate_NotFound verifies the #120 fix: PATCH /workspaces/:id
+// returns 404 (not 200) when the workspace does not exist in the DB.
+//
+// Before PR #125, the handler ran blind UPDATEs that matched zero rows and still
+// returned {"status":"updated"} HTTP 200 — allowing an attacker to probe and
+// speculatively modify workspace attributes (name, tier, parent_id, runtime,
+// workspace_dir) without any observable error.  The existence guard must fire
+// and return 404 before any UPDATE is attempted.
+func TestExtended_WorkspaceUpdate_NotFound(t *testing.T) {
+	mock := setupTestDB(t)
+	setupTestRedis(t)
+	broadcaster := newTestBroadcaster()
+	handler := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", "/tmp/configs")
+
+	// Existence check returns false — workspace does not exist.
+	mock.ExpectQuery("SELECT EXISTS").
+		WithArgs("00000000-0000-0000-0000-000000000000").
+		WillReturnRows(sqlmock.NewRows([]string{"exists"}).AddRow(false))
+
+	// No UPDATE or INSERT should follow — the handler must short-circuit at 404.
+
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Params = gin.Params{{Key: "id", Value: "00000000-0000-0000-0000-000000000000"}}
+
+	body := `{"name":"probe"}`
+	c.Request = httptest.NewRequest("PATCH",
+		"/workspaces/00000000-0000-0000-0000-000000000000",
+		bytes.NewBufferString(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	handler.Update(c)
+
+	if w.Code != http.StatusNotFound {
+		t.Errorf("#120 regression: expected 404 for nonexistent workspace, got %d: %s",
+			w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet sqlmock expectations: %v", err)
+	}
+}
+
 // ---------- TestWorkspaceRestart (Extended) ----------
 
 func TestExtended_WorkspaceRestart_NoProvisioner(t *testing.T) {
diff --git a/platform/internal/middleware/wsauth_middleware_test.go b/platform/internal/middleware/wsauth_middleware_test.go
index 50ba5b91..95b79bbb 100644
--- a/platform/internal/middleware/wsauth_middleware_test.go
+++ b/platform/internal/middleware/wsauth_middleware_test.go
@@ -472,3 +472,50 @@ func TestAdminAuth_InvalidBearer_Returns401(t *testing.T) {
 		t.Errorf("unmet sqlmock expectations: %v", err)
 	}
 }
+
+// ────────────────────────────────────────────────────────────────────────────
+// Issue #120 regression — unauthenticated PATCH /workspaces/:id
+//
+// Before PR #125, PATCH /workspaces/:id was registered outside the wsAdmin
+// group and did NOT enforce AdminAuth.  An attacker could change workspace
+// name, tier, parent_id, runtime, or workspace_dir without any token.
+// Security Auditor confirmed the live exploit:
+//   curl -X PATCH .../workspaces/00000000-.../  -d '{"name":"probe"}' → 200
+//
+// This test asserts AdminAuth applied to the PATCH route blocks unauthenticated
+// requests — the route-level fix in router.go is the enforcement point.
+// ────────────────────────────────────────────────────────────────────────────
+
+// TestAdminAuth_Issue120_PatchWorkspace_NoBearer_Returns401 documents the #120
+// attack vector and verifies that AdminAuth returns 401 for PATCH without a token.
+func TestAdminAuth_Issue120_PatchWorkspace_NoBearer_Returns401(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("sqlmock.New: %v", err)
+	}
+	defer mockDB.Close()
+
+	// HasAnyLiveTokenGlobal returns 1 — at least one workspace is token-enrolled.
+	mock.ExpectQuery(hasAnyLiveTokenGlobalQuery).
+		WillReturnRows(sqlmock.NewRows([]string{"count"}).AddRow(1))
+
+	r := gin.New()
+	// Mirror the PR #125 router change: PATCH is inside the wsAdmin AdminAuth group.
+	r.PATCH("/workspaces/:id", AdminAuth(mockDB), func(c *gin.Context) {
+		c.JSON(http.StatusOK, gin.H{"status": "updated"})
+	})
+
+	w := httptest.NewRecorder()
+	// #120 attack: no Authorization header on PATCH.
+	req, _ := http.NewRequest(http.MethodPatch,
+		"/workspaces/00000000-0000-0000-0000-000000000000",
+		nil)
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusUnauthorized {
+		t.Errorf("#120 PATCH no-bearer: expected 401, got %d: %s", w.Code, w.Body.String())
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("unmet sqlmock expectations: %v", err)
+	}
+}