diff --git a/README.md b/README.md
index 1a3f58e..9bd0200 100644
--- a/README.md
+++ b/README.md
@@ -50,9 +50,10 @@ npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json
 npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json --stages blender
 npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json --stages cesium
 npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json --stages preview
+npm run build:area -- --config config/areas/nantaizi-lake-innovation-valley.json --stages reimport
 ```
 
-`intermediates` 会生成 osm2streets GeoJSON、GeoPackage、QGIS 工程和 QGIS 预览图。`blender` 使用 OSM 和 osm2streets GeoJSON 生成 `.blend`/`.png`。`cesium` 从 `.blend` 导出 `.glb`/`.json`，并生成 Cesium 预览 HTML。`preview` 只在已有 `.glb/.json` 时补生成 HTML。
+`intermediates` 会生成 osm2streets GeoJSON、GeoPackage、QGIS 工程和 QGIS 预览图。`blender` 使用 OSM 和 osm2streets GeoJSON 生成 `.blend`/`.png`。`cesium` 从 `.blend` 导出 `.glb`/`.json`，并生成 Cesium 预览 HTML。`preview` 只在已有 `.glb/.json` 时补生成 HTML。`reimport` 把手工编辑过的 GeoPackage 回导为 GeoJSON，不含在 `all` 里，详见 [QGIS 手工修正工作流](#qgis-手工修正工作流)。
 
 ## 区域配置
 
@@ -169,6 +170,34 @@ Cesium GLB 低层导出：
 
 详见 [blender/README.md](blender/README.md)。
 
+## QGIS 手工修正工作流
+
+如果已经在现成的 `.qgz` 项目里直接编辑了 `gpkg` 图层，不要再重跑 `intermediates`，否则会把手工修改覆盖掉。推荐流程是：
+
+1. 在 QGIS 中打开 `outputs/<area-id>/<area-id>.qgz`
+2. 直接编辑项目内关联的 `gpkg` 图层并保存
+3. 跑 `reimport` 回导 GeoJSON 并重建场景，再接 `blender,cesium`
+
+南台子湖创新谷当前可直接使用下面这条命令：
+
+```bash
+npm run build -- --config config/areas/nantaizi-lake-innovation-valley.json --stages reimport,blender,cesium
+```
+
+`reimport` 阶段（`scripts/reimport-gpkg.js`）做两件事：
+
+- 把 `<area-id>.gpkg` 里的 9 个图层逐个导出到 `osm2streets_web_out/<layer>.geojson`
+- 按 `scripts/lib/scene-layers.js` 的图层表重建 `osm2streets_scene.geojson`（写入 `render_layer` / `z_index`）和 `osm2streets_scene_style.json`
+
+说明：
+
+- 这套流程假设你的手工修改已经保存在 `outputs/<area-id>/<area-id>.gpkg` 中
+- 所有图层先导出到临时目录并校验通过后才写回 `osm2streets_web_out/`；任一图层缺失或导出结果不是合法 FeatureCollection，整批都不落盘（`ogr2ogr` 遇到不存在的图层会留下 0 字节文件，直接覆盖会静默损坏数据）
+- `intermediates` 与 `reimport` 互斥，同时指定会直接报错：前者用 OSM 重建 `gpkg`，正好会抹掉后者要读回的手工修改
+- `blender,cesium` 阶段读取的是 `osm2streets_web_out/*.geojson`，不是直接读取 `gpkg`
+- 如果 Blender 当前环境不稳定，先确认 `geojson` 已完成回导，再单独排查 Blender 本身
+- 增删图层或调整 `z_index` 只需改 `scripts/lib/scene-layers.js`，构建、场景合并、场景样式、QGIS 工程会一并同步
+
 ## 文档
 
 - [docs/input-cases.md](docs/input-cases.md) - 已验证的 OSM 输入案例
diff --git a/docs/changelog.md b/docs/changelog.md
index 16f0e52..995ae24 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -1,5 +1,15 @@
 # Changelog
 
+## 2026-07-28
+
+- 新增 `reimport` 阶段（`scripts/reimport-gpkg.js`），把 QGIS 手工修正过的 `<area-id>.gpkg` 回导为 `osm2streets_web_out/*.geojson` 并重建 `osm2streets_scene.geojson` / `osm2streets_scene_style.json`。手工修正流程从「`ogr2ogr` 循环 + 内联 node 脚本 + `npm run build`」三步压缩为一条命令：
+  ```bash
+  npm run build -- --config config/areas/<area-id>.json --stages reimport,blender,cesium
+  ```
+- `reimport` 先把全部图层导出到临时目录并逐个校验，全部通过才写回输出目录：`ogr2ogr` 对不存在的图层退出码非 0 但仍会留下 0 字节文件，逐图层直接覆盖会静默损坏数据。
+- `intermediates` 与 `reimport` 同时指定时直接报错：前者会用 OSM 重建 GeoPackage，正好抹掉后者要读回的手工修改。`reimport` 不含在 `all` 中。
+- 新增 `scripts/lib/scene-layers.js` 作为 9 个渲染图层的唯一定义源（id、`z_index`、配色、描边宽度）。此前该表在合并场景、场景样式 JSON、生成的 QGIS 工程、README 手工流程中各有一份副本，改一处漏其余会导致图层叠放顺序错误并流入 Blender/Cesium。构建产物（GeoJSON、GeoPackage、`.qgz` 符号、样式 JSON）与改动前逐字节一致。
+
 ## 2026-07-27
 
 - 实验分支新增 Cesium 车辆巡航预览：从 OSM 可行驶 `highway` 提取 bounds 内路线，输出 `<area-id>-vehicle-route.json`，并在预览页中驱动车辆循环移动。
diff --git a/scripts/build-area.js b/scripts/build-area.js
index 33f10ce..5237cf3 100755
--- a/scripts/build-area.js
+++ b/scripts/build-area.js
@@ -15,6 +15,16 @@ const requestedStages = args.stages
   : null;
 const stages = resolveStages(area.stages, requestedStages);
 
+// intermediates deletes and rebuilds the GeoPackage from OSM, which is exactly
+// the manual work reimport exists to recover. Refuse the combination instead of
+// silently letting one undo the other.
+if (stages.intermediates && stages.reimport) {
+  throw new Error(
+    "Stages 'intermediates' and 'reimport' are mutually exclusive: " +
+    "intermediates rebuilds the GeoPackage from OSM and would discard the QGIS edits reimport reads back.",
+  );
+}
+
 console.log(`Area: ${area.id}`);
 console.log(`Config: ${configPath}`);
 console.log(`Output: ${area.outputs.areaDir}`);
@@ -22,6 +32,9 @@ console.log(`Output: ${area.outputs.areaDir}`);
 if (stages.intermediates) {
   buildIntermediates(area);
 }
+if (stages.reimport) {
+  reimportGpkg(area);
+}
 if (stages.blender) {
   buildBlenderScene(area);
 }
@@ -97,6 +110,7 @@ function normalizeAreaConfig(raw) {
       intermediates: raw.stages?.intermediates ?? raw.stages?.qgis ?? true,
       blender: raw.stages?.blender ?? true,
       cesium: raw.stages?.cesium ?? true,
+      reimport: false,
       preview: false,
     },
     qgis: {
@@ -142,6 +156,8 @@ function splitList(value) {
 
 function resolveStages(defaults, requested) {
   if (!requested) return defaults;
+  // 'reimport' is deliberately absent from 'all': it is a recovery step for
+  // hand-edited GeoPackages, never part of a full build.
   const aliases = {
     all: ["intermediates", "blender", "cesium"],
     qgis: ["intermediates"],
@@ -149,6 +165,8 @@ function resolveStages(defaults, requested) {
     geojson: ["intermediates"],
     intermediate: ["intermediates"],
     intermediates: ["intermediates"],
+    reimport: ["reimport"],
+    gpkg: ["reimport"],
     blender: ["blender"],
     scene: ["blender"],
     cesium: ["cesium"],
@@ -157,18 +175,18 @@ function resolveStages(defaults, requested) {
     html: ["preview"],
     cesiumPreview: ["preview"],
   };
-  const out = { intermediates: false, blender: false, cesium: false, preview: false };
+  const out = { intermediates: false, reimport: false, blender: false, cesium: false, preview: false };
   for (const stage of requested) {
     const mapped = aliases[stage];
     if (!mapped) {
-      throw new Error(`Unknown stage '${stage}'. Use intermediates, blender, cesium, preview, or all.`);
+      throw new Error(`Unknown stage '${stage}'. Use intermediates, reimport, blender, cesium, preview, or all.`);
     }
     for (const key of mapped) out[key] = true;
   }
   return out;
 }
 
-function buildIntermediates(area) {
+function writeDerivedConfig(area) {
   fs.mkdirSync(area.outputs.pipelineDir, { recursive: true });
   const derivedConfig = {
     qgisApp: area.qgisApp,
@@ -191,6 +209,11 @@ function buildIntermediates(area) {
   };
   const derivedConfigPath = path.join(area.outputs.pipelineDir, "osm2streets-qgis.config.json");
   fs.writeFileSync(derivedConfigPath, `${JSON.stringify(derivedConfig, null, 2)}\n`);
+  return derivedConfigPath;
+}
+
+function buildIntermediates(area) {
+  const derivedConfigPath = writeDerivedConfig(area);
 
   console.log("Stage: intermediates (osm2streets GeoJSON + QGIS)");
   runCommand(process.execPath, [
@@ -200,6 +223,17 @@ function buildIntermediates(area) {
   ], "intermediates");
 }
 
+function reimportGpkg(area) {
+  const derivedConfigPath = writeDerivedConfig(area);
+
+  console.log("Stage: reimport (GeoPackage -> GeoJSON)");
+  runCommand(process.execPath, [
+    path.join(repoRoot, "scripts", "reimport-gpkg.js"),
+    "--config",
+    derivedConfigPath,
+  ], "reimport");
+}
+
 function buildBlenderScene(area) {
   ensureFile(blenderExecutable(area), "Blender executable");
   ensureFile(path.join(repoRoot, "blender", "generate_scene.py"), "Blender scene generator");
diff --git a/scripts/build-osm2streets-qgis.js b/scripts/build-osm2streets-qgis.js
index 771e586..c205b58 100755
--- a/scripts/build-osm2streets-qgis.js
+++ b/scripts/build-osm2streets-qgis.js
@@ -5,6 +5,15 @@ const path = require("path");
 const os = require("os");
 const { execFileSync } = require("child_process");
 const { JsStreetNetwork } = require("osm2streets-js-node");
+const {
+  SCENE_LAYERS,
+  SCENE_FILE,
+  SCENE_STYLE_FILE,
+  layerFile,
+  mergeScene,
+  sceneStyle,
+  qgisRgba,
+} = require("./lib/scene-layers");
 
 const repoRoot = path.resolve(__dirname, "..");
 const args = parseArgs(process.argv.slice(2));
@@ -79,22 +88,16 @@ const split = splitLayers(
   intersectionCornerSourceMaxDimensionMeters,
   osm,
 );
-writeJson(path.join(outDir, "road_surface.geojson"), split.roadSurface);
-writeJson(path.join(outDir, "intersection_surface.geojson"), split.intersectionSurface);
-writeJson(path.join(outDir, "sidewalks.geojson"), split.sidewalks);
-writeJson(path.join(outDir, "lane_separators.geojson"), split.laneSeparators);
-writeJson(path.join(outDir, "center_lines.geojson"), split.centerLines);
-writeJson(path.join(outDir, "vehicle_stop_lines.geojson"), split.vehicleStopLines);
-writeJson(path.join(outDir, "lane_arrows_webscale.geojson"), split.laneArrows);
+for (const layer of SCENE_LAYERS) {
+  writeJson(path.join(outDir, layerFile(layer)), split[layer.splitKey]);
+}
 if (arrowMergeTriangles) {
   normalizeLaneArrows(path.join(outDir, "lane_arrows_webscale.geojson"), arrowOutlineSimplifyMeters);
   split.laneArrows = JSON.parse(fs.readFileSync(path.join(outDir, "lane_arrows_webscale.geojson"), "utf8"));
 }
-writeJson(path.join(outDir, "sidewalk_corners.geojson"), split.sidewalkCorners);
-writeJson(path.join(outDir, "crosswalks.geojson"), split.crosswalks);
-writeJson(path.join(outDir, "osm2streets_scene.geojson"), mergedScene(split));
+writeJson(path.join(outDir, SCENE_FILE), mergeScene((layer) => split[layer.splitKey]));
 fs.writeFileSync(
-  path.join(outDir, "osm2streets_scene_style.json"),
+  path.join(outDir, SCENE_STYLE_FILE),
   JSON.stringify(sceneStyle(), null, 2),
 );
 
@@ -102,15 +105,10 @@ if (fs.existsSync(gpkgPath)) {
   fs.unlinkSync(gpkgPath);
 }
 const ogrEnv = qgisEnv();
-importLayer(gpkgPath, path.join(outDir, "road_surface.geojson"), "road_surface", false, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "intersection_surface.geojson"), "intersection_surface", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "sidewalks.geojson"), "sidewalks", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "sidewalk_corners.geojson"), "sidewalk_corners", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "lane_separators.geojson"), "lane_separators", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "center_lines.geojson"), "center_lines", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "vehicle_stop_lines.geojson"), "vehicle_stop_lines", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "lane_arrows_webscale.geojson"), "lane_arrows_webscale", true, ogrEnv);
-importLayer(gpkgPath, path.join(outDir, "crosswalks.geojson"), "crosswalks", true, ogrEnv);
+// First layer creates the GeoPackage; the rest append into it.
+SCENE_LAYERS.forEach((layer, index) => {
+  importLayer(gpkgPath, path.join(outDir, layerFile(layer)), layer.id, index > 0, ogrEnv);
+});
 
 const qgisScript = path.join(outDir, "_create_qgis_project.py");
 const previewFeature = split.crosswalks.features[0] || split.laneArrows.features[0] || split.roadSurface.features[0];
@@ -406,53 +404,6 @@ function emptyCollection() {
   return { type: "FeatureCollection", features: [] };
 }
 
-function mergedScene(split) {
-  const layers = [
-    ["road_surface", 10, split.roadSurface],
-    ["intersection_surface", 20, split.intersectionSurface],
-    ["sidewalks", 30, split.sidewalks],
-    ["sidewalk_corners", 40, split.sidewalkCorners],
-    ["lane_separators", 50, split.laneSeparators],
-    ["center_lines", 60, split.centerLines],
-    ["crosswalks", 70, split.crosswalks],
-    ["vehicle_stop_lines", 80, split.vehicleStopLines],
-    ["lane_arrows_webscale", 90, split.laneArrows],
-  ];
-  return {
-    type: "FeatureCollection",
-    features: layers.flatMap(([renderLayer, zIndex, collection]) => (
-      (collection.features || []).map((feature) => ({
-        ...feature,
-        properties: {
-          ...(feature.properties || {}),
-          render_layer: renderLayer,
-          z_index: zIndex,
-        },
-      }))
-    )),
-  };
-}
-
-function sceneStyle() {
-  return {
-    version: 1,
-    geometry: "polygon",
-    sortProperty: "z_index",
-    layerProperty: "render_layer",
-    layers: [
-      { id: "road_surface", zIndex: 10, fill: "#2b2b28", outline: "#1e1e1c", outlineWidth: 0.04 },
-      { id: "intersection_surface", zIndex: 20, fill: "#2b2b28", outline: "#1e1e1c", outlineWidth: 0.04 },
-      { id: "sidewalks", zIndex: 30, fill: "#bebeb6", outline: "#9c9c94", outlineWidth: 0.025 },
-      { id: "sidewalk_corners", zIndex: 40, fill: "#bebeb6", outline: "#9c9c94", outlineWidth: 0.025 },
-      { id: "lane_separators", zIndex: 50, fill: "#eeeee6", outline: null, outlineWidth: 0 },
-      { id: "center_lines", zIndex: 60, fill: "#f5be2a", outline: null, outlineWidth: 0 },
-      { id: "crosswalks", zIndex: 70, fill: "#fffff6", outline: null, outlineWidth: 0 },
-      { id: "vehicle_stop_lines", zIndex: 80, fill: "#fffff6", outline: null, outlineWidth: 0 },
-      { id: "lane_arrows_webscale", zIndex: 90, fill: "#fffff6", outline: "#2b2b28", outlineWidth: 0.015 },
-    ],
-  };
-}
-
 function splitLayers(dir, arrowScaleValue, maxCornerDimensionMeters, osm) {
   const plain = JSON.parse(fs.readFileSync(path.join(dir, "plain.geojson"), "utf8"));
   const lanePolygons = JSON.parse(fs.readFileSync(path.join(dir, "lane_polygons.geojson"), "utf8"));
@@ -1360,6 +1311,16 @@ function importLayer(gpkg, source, layerName, update, env) {
   execFileSync(ogr2ogr, args, { stdio: "inherit", env: { ...process.env, ...env } });
 }
 
+function qgisLayerSpecs() {
+  return SCENE_LAYERS.map((layer) => ({
+    id: layer.id,
+    title: layer.title,
+    fill: qgisRgba(layer.fill),
+    outline: qgisRgba(layer.outline, layer.outlineAlpha ?? 255),
+    outlineWidth: String(layer.outlineWidth),
+  }));
+}
+
 function makeQgisScript(options) {
   return `
 from pathlib import Path
@@ -1384,6 +1345,7 @@ PROJECT_PATH = ${JSON.stringify(options.projectPath)}
 PREVIEW_PATH = ${JSON.stringify(options.previewPath)}
 PREVIEW_EXTENT = [${options.previewExtent.split(",").map(Number).join(", ")}]
 LAYER_PREFIX = ${JSON.stringify(options.layerPrefix || "osm2streets")}
+LAYER_SPECS = ${JSON.stringify(qgisLayerSpecs(), null, 4)}
 
 def fill_symbol(color, outline="0,0,0,0", outline_width="0"):
     return QgsFillSymbol.createSimple({
@@ -1412,17 +1374,16 @@ project.setCrs(QgsCoordinateReferenceSystem("EPSG:4326"))
 project.setPresetHomePath(str(Path(PROJECT_PATH).parent))
 
 layers = {
-    "road_surface": make_layer("road_surface", f"{LAYER_PREFIX} road surface", "43,43,40,255", "30,30,28,255", "0.04"),
-    "intersection_surface": make_layer("intersection_surface", f"{LAYER_PREFIX} intersection surface", "43,43,40,255", "30,30,28,255", "0.04"),
-    "sidewalks": make_layer("sidewalks", f"{LAYER_PREFIX} sidewalks", "190,190,182,255", "156,156,148,255", "0.025"),
-    "sidewalk_corners": make_layer("sidewalk_corners", f"{LAYER_PREFIX} sidewalk corners", "190,190,182,255", "156,156,148,255", "0.025"),
-    "crosswalks": make_layer("crosswalks", f"{LAYER_PREFIX} crosswalks", "255,255,246,255"),
-    "lane_separators": make_layer("lane_separators", f"{LAYER_PREFIX} lane separators", "238,238,230,255"),
-    "center_lines": make_layer("center_lines", f"{LAYER_PREFIX} center lines", "245,190,42,255"),
-    "vehicle_stop_lines": make_layer("vehicle_stop_lines", f"{LAYER_PREFIX} vehicle stop lines", "255,255,246,255"),
-    "lane_arrows": make_layer("lane_arrows_webscale", f"{LAYER_PREFIX} lane arrows", "255,255,246,255", "43,43,40,200", "0.015"),
+    spec["id"]: make_layer(
+        spec["id"],
+        f"{LAYER_PREFIX} {spec['title']}",
+        spec["fill"],
+        spec["outline"],
+        spec["outlineWidth"],
+    )
+    for spec in LAYER_SPECS
 }
-draw_order = ["road_surface", "intersection_surface", "sidewalks", "sidewalk_corners", "lane_separators", "center_lines", "crosswalks", "vehicle_stop_lines", "lane_arrows"]
+draw_order = [spec["id"] for spec in LAYER_SPECS]
 for key in draw_order:
     project.addMapLayer(layers[key], False)
 root = project.layerTreeRoot()
diff --git a/scripts/lib/scene-layers.js b/scripts/lib/scene-layers.js
new file mode 100644
index 0000000..faceb3a
--- /dev/null
+++ b/scripts/lib/scene-layers.js
@@ -0,0 +1,164 @@
+"use strict";
+
+// Single source of truth for the osm2streets render layers.
+//
+// The same nine layers, in the same order, previously appeared four times:
+// the merged-scene z_index table, the scene style JSON, the generated QGIS
+// project (layer dict + draw_order), and the README's manual rebuild snippet.
+// Adding a layer or changing a z-index meant editing all of them in lockstep,
+// and a missed copy produces a silently mis-stacked scene downstream in
+// Blender/Cesium. Everything now derives from SCENE_LAYERS.
+//
+// zIndex doubles as draw order: lowest paints first (bottom of the stack).
+// outline: null means "no stroke" (QGIS gets a fully transparent outline).
+
+const SCENE_LAYERS = [
+  {
+    id: "road_surface",
+    splitKey: "roadSurface",
+    zIndex: 10,
+    title: "road surface",
+    fill: "#2b2b28",
+    outline: "#1e1e1c",
+    outlineWidth: 0.04,
+  },
+  {
+    id: "intersection_surface",
+    splitKey: "intersectionSurface",
+    zIndex: 20,
+    title: "intersection surface",
+    fill: "#2b2b28",
+    outline: "#1e1e1c",
+    outlineWidth: 0.04,
+  },
+  {
+    id: "sidewalks",
+    splitKey: "sidewalks",
+    zIndex: 30,
+    title: "sidewalks",
+    fill: "#bebeb6",
+    outline: "#9c9c94",
+    outlineWidth: 0.025,
+  },
+  {
+    id: "sidewalk_corners",
+    splitKey: "sidewalkCorners",
+    zIndex: 40,
+    title: "sidewalk corners",
+    fill: "#bebeb6",
+    outline: "#9c9c94",
+    outlineWidth: 0.025,
+  },
+  {
+    id: "lane_separators",
+    splitKey: "laneSeparators",
+    zIndex: 50,
+    title: "lane separators",
+    fill: "#eeeee6",
+    outline: null,
+    outlineWidth: 0,
+  },
+  {
+    id: "center_lines",
+    splitKey: "centerLines",
+    zIndex: 60,
+    title: "center lines",
+    fill: "#f5be2a",
+    outline: null,
+    outlineWidth: 0,
+  },
+  {
+    id: "crosswalks",
+    splitKey: "crosswalks",
+    zIndex: 70,
+    title: "crosswalks",
+    fill: "#fffff6",
+    outline: null,
+    outlineWidth: 0,
+  },
+  {
+    id: "vehicle_stop_lines",
+    splitKey: "vehicleStopLines",
+    zIndex: 80,
+    title: "vehicle stop lines",
+    fill: "#fffff6",
+    outline: null,
+    outlineWidth: 0,
+  },
+  {
+    id: "lane_arrows_webscale",
+    splitKey: "laneArrows",
+    zIndex: 90,
+    title: "lane arrows",
+    fill: "#fffff6",
+    outline: "#2b2b28",
+    outlineAlpha: 200,
+    outlineWidth: 0.015,
+  },
+];
+
+const SCENE_FILE = "osm2streets_scene.geojson";
+const SCENE_STYLE_FILE = "osm2streets_scene_style.json";
+
+function layerFile(layer) {
+  return `${layer.id}.geojson`;
+}
+
+// getCollection(layer) -> FeatureCollection, so callers can source layers from
+// the in-memory split (build) or from disk (reimport) with the same merge.
+function mergeScene(getCollection) {
+  return {
+    type: "FeatureCollection",
+    features: SCENE_LAYERS.flatMap((layer) => {
+      const collection = getCollection(layer) || {};
+      return (collection.features || []).map((feature) => ({
+        ...feature,
+        properties: {
+          ...(feature.properties || {}),
+          render_layer: layer.id,
+          z_index: layer.zIndex,
+        },
+      }));
+    }),
+  };
+}
+
+function sceneStyle() {
+  return {
+    version: 1,
+    geometry: "polygon",
+    sortProperty: "z_index",
+    layerProperty: "render_layer",
+    layers: SCENE_LAYERS.map((layer) => ({
+      id: layer.id,
+      zIndex: layer.zIndex,
+      fill: layer.fill,
+      outline: layer.outline,
+      outlineWidth: layer.outlineWidth,
+    })),
+  };
+}
+
+// QGIS symbol properties want "r,g,b,a" strings rather than hex.
+function qgisRgba(hex, alpha = 255) {
+  if (!hex) return "0,0,0,0";
+  const match = /^#?([0-9a-f]{6})$/i.exec(hex.trim());
+  if (!match) {
+    throw new Error(`Expected #rrggbb color, got: ${hex}`);
+  }
+  const value = parseInt(match[1], 16);
+  const r = (value >> 16) & 0xff;
+  const g = (value >> 8) & 0xff;
+  const b = value & 0xff;
+  return `${r},${g},${b},${alpha}`;
+}
+
+module.exports = {
+  SCENE_LAYERS,
+  SCENE_FILE,
+  SCENE_STYLE_FILE,
+  layerFile,
+  mergeScene,
+  sceneStyle,
+  qgisRgba,
+};
diff --git a/scripts/reimport-gpkg.js b/scripts/reimport-gpkg.js
new file mode 100755
index 0000000..51bf92b
--- /dev/null
+++ b/scripts/reimport-gpkg.js
@@ -0,0 +1,179 @@
+#!/usr/bin/env node
+
+"use strict";
+
+// Reverse of the intermediates stage: pull manually-edited layers back out of
+// <area>.gpkg into osm2streets_web_out/*.geojson and rebuild the merged scene.
+//
+// Use after hand-fixing geometry in QGIS. Re-running intermediates would
+// regenerate the GeoPackage from OSM and throw those edits away.
+//
+// Every layer is exported to a staging directory and parsed before anything in
+// outDir is touched: ogr2ogr exits non-zero on a missing layer but still leaves
+// a zero-byte file behind, so a partial export must not reach the output tree.
+
+const fs = require("fs");
+const path = require("path");
+const os = require("os");
+const { execFileSync } = require("child_process");
+const {
+  SCENE_LAYERS,
+  SCENE_FILE,
+  SCENE_STYLE_FILE,
+  layerFile,
+  mergeScene,
+  sceneStyle,
+} = require("./lib/scene-layers");
+
+const args = parseArgs(process.argv.slice(2));
+const config = loadConfig(args);
+const qgisApp = config.qgisApp || "/Applications/QGIS.app";
+const qgisMacOS = path.join(qgisApp, "Contents", "MacOS");
+const ogr2ogr = path.join(qgisMacOS, "ogr2ogr");
+const ogrinfo = path.join(qgisMacOS, "ogrinfo");
+const outDir = path.resolve(requireText(config.outDir, "outDir"));
+const gpkgPath = path.resolve(requireText(config.gpkg, "gpkg"));
+
+for (const exe of [ogr2ogr, ogrinfo]) {
+  if (!fs.existsSync(exe)) {
+    throw new Error(`QGIS executable not found: ${exe}`);
+  }
+}
+if (!fs.existsSync(gpkgPath)) {
+  throw new Error(`GeoPackage not found: ${gpkgPath}\nRun the intermediates stage first.`);
+}
+if (!fs.existsSync(outDir)) {
+  throw new Error(`GeoJSON output directory not found: ${outDir}`);
+}
+
+console.log(`Reimport: ${gpkgPath}`);
+console.log(`Target:   ${outDir}`);
+
+const present = gpkgLayers();
+const missing = SCENE_LAYERS.filter((layer) => !present.has(layer.id)).map((layer) => layer.id);
+if (missing.length) {
+  throw new Error(
+    `GeoPackage is missing ${missing.length} layer(s): ${missing.join(", ")}\n` +
+    `Present: ${[...present].join(", ") || "(none)"}`,
+  );
+}
+
+const stagingDir = fs.mkdtempSync(path.join(os.tmpdir(), "osm2streets-reimport-"));
+try {
+  const staged = SCENE_LAYERS.map((layer) => {
+    const stagedPath = path.join(stagingDir, layerFile(layer));
+    exportLayer(layer.id, stagedPath);
+    const collection = readCollection(stagedPath, layer.id);
+    console.log(`${layer.id}\tfeatures=${collection.features.length}`);
+    return { layer, stagedPath, collection };
+  });
+
+  for (const item of staged) {
+    // Copy rather than rename: the staging dir may be on another filesystem.
+    fs.copyFileSync(item.stagedPath, path.join(outDir, layerFile(item.layer)));
+  }
+
+  const byId = new Map(staged.map((item) => [item.layer.id, item.collection]));
+  const scene = mergeScene((layer) => byId.get(layer.id));
+  fs.writeFileSync(path.join(outDir, SCENE_FILE), JSON.stringify(scene));
+  fs.writeFileSync(
+    path.join(outDir, SCENE_STYLE_FILE),
+    JSON.stringify(sceneStyle(), null, 2),
+  );
+  console.log(`${path.join(outDir, SCENE_FILE)}\tfeatures=${scene.features.length}`);
+
+  const empty = staged.filter((item) => item.collection.features.length === 0);
+  if (empty.length) {
+    console.warn(`Warning: empty layer(s): ${empty.map((item) => item.layer.id).join(", ")}`);
+  }
+} finally {
+  fs.rmSync(stagingDir, { recursive: true, force: true });
+}
+
+function parseArgs(argv) {
+  const out = {};
+  for (let i = 0; i < argv.length; i += 1) {
+    const arg = argv[i];
+    if (!arg.startsWith("--")) continue;
+    const key = arg.slice(2).replace(/-([a-z])/g, (_, c) => c.toUpperCase());
+    const next = argv[i + 1];
+    if (!next || next.startsWith("--")) {
+      out[key] = "true";
+    } else {
+      out[key] = next;
+      i += 1;
+    }
+  }
+  return out;
+}
+
+function loadConfig(cliArgs) {
+  const base = {};
+  if (cliArgs.config) {
+    const file = path.resolve(cliArgs.config);
+    if (!fs.existsSync(file)) {
+      throw new Error(`Config file not found: ${file}`);
+    }
+    Object.assign(base, JSON.parse(fs.readFileSync(file, "utf8")));
+  }
+  for (const key of ["qgisApp", "outDir", "gpkg"]) {
+    if (cliArgs[key] !== undefined) base[key] = cliArgs[key];
+  }
+  return base;
+}
+
+function requireText(value, key) {
+  if (typeof value !== "string" || value.trim() === "") {
+    throw new Error(`Missing config key: ${key}`);
+  }
+  return value;
+}
+
+function gdalEnv() {
+  return {
+    PROJ_LIB: path.join(qgisApp, "Contents", "Resources", "qgis", "proj"),
+    GDAL_DATA: path.join(qgisApp, "Contents", "Resources", "qgis", "gdal"),
+  };
+}
+
+function gpkgLayers() {
+  const output = execFileSync(ogrinfo, ["-q", gpkgPath], {
+    encoding: "utf8",
+    env: { ...process.env, ...gdalEnv() },
+  });
+  const names = new Set();
+  for (const line of output.split("\n")) {
+    const match = /^\s*\d+:\s+(\S+)/.exec(line);
+    if (match) names.add(match[1]);
+  }
+  return names;
+}
+
+function exportLayer(layerName, destination) {
+  // No COORDINATE_PRECISION here on purpose: the default already round-trips
+  // full double precision, and setting it explicitly makes GDAL run its
+  // precision-reduction pass, which drops vertices that collapse at the given
+  // resolution (measured: 28 points lost across 7 lane-arrow polygons).
+  execFileSync(ogr2ogr, [
+    "-f", "GeoJSON",
+    destination,
+    gpkgPath,
+    layerName,
+  ], {
+    stdio: "inherit",
+    env: { ...process.env, ...gdalEnv() },
+  });
+}
+
+function readCollection(file, layerName) {
+  let parsed;
+  try {
+    parsed = JSON.parse(fs.readFileSync(file, "utf8"));
+  } catch (error) {
+    throw new Error(`Layer '${layerName}' did not export valid GeoJSON: ${error.message}`);
+  }
+  if (parsed.type !== "FeatureCollection" || !Array.isArray(parsed.features)) {
+    throw new Error(`Layer '${layerName}' did not export a FeatureCollection`);
+  }
+  return parsed;
+}