diff --git a/.trellis/spec/guides/cross-layer-thinking-guide.md b/.trellis/spec/guides/cross-layer-thinking-guide.md
index d9bec4e..b080f4e 100644
--- a/.trellis/spec/guides/cross-layer-thinking-guide.md
+++ b/.trellis/spec/guides/cross-layer-thinking-guide.md
@@ -144,20 +144,22 @@ OSM way 的端点不一定在原始 XML 中有三个以上相连 way；osm2stree
 
 **教训**：**跨阶段契约必须随产物保存；兼容旧产物的字符串回退也要被审查**。
 
-### 坑 6：部分构建复用了过期的交通信号锚点
+### 坑 6：部分构建复用了过期的交通信号运行时数据
 
-`scripts/lib/traffic-signals.js` 根据当前 OSM 的 `highway=traffic_signals` 控制节点、
-`vehicle_stop_lines.geojson` 和 `intersection_surface.geojson` 派生
-`osm2streets_web_out/traffic_signals.json`。Blender 将这份文件中的每个 signal id 导出为
-三个动态灯节点和一组倒计时节点，`scripts/lib/cesium-preview.js` 再按相同 id 控制它们。
+`intermediates` 才能根据当前 OSM 的 `highway=traffic_signals` 控制节点、
+`vehicle_stop_lines.geojson` 和 `intersection_surface.geojson` 初始化可编辑的
+`traffic_signal_assemblies.geojson`。此后该 GeoJSON 是 QGIS 编辑生命周期内的事实源；
+`traffic_signals.json` 只是严格校验后派生的运行时数据。Blender 将其中每个稳定的
+`signal_uid` 导出为静态设施、三个动态灯节点和一组倒计时节点，
+`scripts/lib/cesium-preview.js` 再按相同 id 控制它们。
 
-因此执行 `blender,cesium,preview` 这类部分构建时，必须在 Blender stage 入口重新写入
-交通信号文件。若沿用旧文件，GLB 可能已经包含新增 T/十字路口，但预览仍只控制旧的
-signal id，表现为灯不切换、数字叠加或路口整体异常。该刷新由
+因此执行 `blender,cesium,preview` 这类部分构建时，必须在 Blender stage 入口从当前
+`traffic_signal_assemblies.geojson` 重建运行时 JSON，但绝不能重新从 OSM 初始化位置，
+否则会覆盖 QGIS 中移动、旋转或禁用设施的编辑。该刷新由
 `scripts/build-area.js:buildBlenderScene()` 负责。
 
-**教训**：**任何由输入 OSM 或归一化图层派生、又被多个后续 stage 共享的中间 JSON，
-都必须在最早消费它的 stage 重新生成，不能只在完整 `intermediates` 构建时生成。**
+**教训**：**跨阶段运行时 JSON 必须在最早消费它的 stage 从当前权威产物重建；同时要
+区分“初始化来源”和“编辑后的事实源”，不能用早期输入覆盖人工编辑。**
 
 ---
 
diff --git a/.trellis/spec/pipeline/cli-and-stages.md b/.trellis/spec/pipeline/cli-and-stages.md
index 06ba84e..25c2c6e 100644
--- a/.trellis/spec/pipeline/cli-and-stages.md
+++ b/.trellis/spec/pipeline/cli-and-stages.md
@@ -343,13 +343,14 @@ out.vehicleStopLines = crosswalkData.stopLines;
 // 原生 lane_markings 停止线不得复制到输出。
 ```
 
-## 信号锚点的跨阶段消费
+## 可编辑信号设施与运行时锚点的跨阶段消费
 
 ### 1. Scope / Trigger
 
 路口信号设施需要同时被 Blender 主 GLB 和 Cesium 预览消费时，使用
-`<geojsonDir>/traffic_signals.json`。它是附属 intermediates 产物，而不是第十个
-osm2streets/QGIS 图层。
+`<geojsonDir>/traffic_signal_assemblies.geojson` 是 GeoPackage/QGIS 中的附属可编辑点图层；
+`<geojsonDir>/traffic_signals.json` 是从它严格校验并派生的运行时产物。前者不属于九个
+`SCENE_LAYERS`，后者不进入 GeoPackage。
 
 ### 2. Signatures
 
@@ -366,15 +367,19 @@ area.outputs.trafficSignals
 
 ### 3. Contracts
 
-- `build-area.js:writeTrafficSignals()` 是锚点 JSON 的生产者，调用
-  `traffic-signals.js:readTrafficSignals()`，输入为 `vehicle_stop_lines.geojson` 和
-  `intersection_surface.geojson`。
-- `intermediates` 与 `reimport` 都必须在其 GeoJSON 产物稳定后重写锚点，确保 QGIS
-  人工修补反导入后，Blender 和 preview 仍使用同一事实。
+- `intermediates` 从 OSM control、停止线和路口面初始化 `traffic_signal_assemblies.geojson`，
+  并将其作为附属点层导入 GeoPackage；完整重跑 intermediates 会像道路图层一样覆盖人工编辑。
+- `reimport` 必须与九个场景层一起暂存导出附属层，先校验全部信号要素，再替换任何输出。
+- `build-area.js:writeTrafficSignals()` 只从当前 `traffic_signal_assemblies.geojson` 重建运行时
+  `traffic_signals.json`。Blender 入口也执行这一步，但不得重新从 OSM 初始化位置。
 - `blender` 和 `preview` 在启动前必须检查该文件存在；前者把静态设施写进 `05_Props`，
   后者只叠加动态灯珠、倒计时和车辆相位。
-- `traffic_signals.json` 不得加入 `SCENE_LAYERS`、GeoPackage 或 QGIS 工程；这些层只能
-  继续包含九个道路场景图层。
+- `traffic_signal_assemblies.geojson` 必须加入 GeoPackage/QGIS 工程，但不得加入
+  `SCENE_LAYERS`、合并道路场景或栅格预览；`traffic_signals.json` 仍不得加入 GeoPackage。
+- `signal_uid` 必须由 control id、source way id 和相邻 arm node id 确定性生成；运行时 `id`
+  使用该技术 id。`display_id` 可编辑且非空时唯一，修改它不得重命名 GLB 节点。
+- Point 几何是灯杆地面点；`stop_lon`/`stop_lat` 独立保存，移动杆件不得移动车辆停止点。
+- `enabled=false` 的要素保留在编辑层但不进入运行时 signals。
 - `layout.countdownLateralMeters` 等几何字段是 Blender/preview 的共同事实源；横向正值统一
   表示相对来车方向的右侧。不得在任一消费方用独立的负号约定替代它。
 - `layout.mastHeightMeters` 与 `layout.headCenterHeightMeters` 必须相等，表示横杆与灯壳的
@@ -385,9 +390,9 @@ area.outputs.trafficSignals
 
 | 条件 | 结果 |
 |---|---|
-| `intermediates` 或 `reimport` 有合法停止线和路口面 | 写出 `version` 与 `signals` 数组，即使数组为空 |
+| `intermediates` 或 `reimport` 有合法编辑层 | 写出 `version` 与 `signals` 数组，即使数组为空 |
 | 直接运行 `blender` / `preview` 但锚点不存在 | 在启动外部工具前报 `Traffic signal anchors not found` |
-| 单个停止线无法可靠关联路口 | 锚点生成器跳过该项，其他进口照常输出 |
+| `signal_uid` 缺失/重复、非空 `display_id` 重复、字段或 Point 无效 | 重导入在替换任何输出前失败 |
 | 用户仅修改 QGIS 后运行 `reimport` | 重新生成锚点，不沿用旧坐标 |
 
 ### 5. Good/Base/Bad Cases
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/check.jsonl b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/check.jsonl
new file mode 100644
index 0000000..113b732
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/check.jsonl
@@ -0,0 +1,5 @@
+{"file":".trellis/spec/pipeline/cli-and-stages.md","reason":"Check stage ownership, diagnostics, and traffic signal contract compliance"}
+{"file":".trellis/spec/pipeline/external-tools.md","reason":"Check atomic reimport behavior and external-tool handling"}
+{"file":".trellis/spec/guides/cross-layer-thinking-guide.md","reason":"Check full editable-layer to runtime JSON to Blender/Cesium data flow"}
+{"file":".trellis/spec/guides/artifact-parity-guide.md","reason":"Check intended and unintended scene/GLB structural differences"}
+{"file":".trellis/spec/blender/testing.md","reason":"Check appropriate pure and Blender validation coverage"}
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/design.md b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/design.md
new file mode 100644
index 0000000..d7114ab
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/design.md
@@ -0,0 +1,100 @@
+# Design: QGIS Traffic Signal Overrides
+
+## Architecture
+
+Introduce a separate auxiliary-edit-layer registry rather than adding traffic signals to `SCENE_LAYERS`. The initial registry contains one layer:
+
+```text
+traffic_signal_assemblies.geojson
+  geometry: Point (pole ground position, EPSG:4326)
+  properties: stable identity, source identity, heading, phase, reach, stop point, enabled, z offset
+```
+
+The existing runtime file remains:
+
+```text
+traffic_signals.json
+  version/layout/signals[] with full pose.* data
+```
+
+The editable GeoJSON is the placement source; the runtime JSON is a derived consumer artifact.
+
+## Data Flow
+
+```text
+OSM controls + topology + stop lines + intersections
+                         |
+                   intermediates only
+                         v
+             traffic_signal_assemblies.geojson
+                         |
+                import into GeoPackage
+                         |
+                    edit in QGIS
+                         |
+                      reimport
+                         v
+             traffic_signal_assemblies.geojson
+                         |
+                 validate + derive pose
+                         v
+                  traffic_signals.json
+                    /             \
+                 Blender         preview/Cesium
+```
+
+`blender` reruns the final validation/derivation arrow from the editable GeoJSON so derived JSON cannot be stale, but it never reruns the OSM initialization arrow.
+
+## Editable Feature Contract
+
+Recommended properties:
+
+| Property | Type | Ownership |
+|---|---|---|
+| `signal_uid` | string | generated, immutable technical identity |
+| `display_id` | string | user-editable unique label/number |
+| `control_id` | string | generated OSM control id |
+| `approach_id` | string | generated physical approach identity |
+| `source_way_id` | string | generated matching/diagnostic field |
+| `heading_deg` | number | user-editable assembly facing direction |
+| `phase_group` | integer 0/1 | user-editable current two-phase group |
+| `mast_reach_m` | positive number | user-editable arm reach |
+| `stop_lon`, `stop_lat` | finite numbers | generated vehicle stop point, preserved when pole moves |
+| `enabled` | boolean/integer | user-editable suppression flag |
+| `z_offset_m` | finite number | user-editable vertical adjustment |
+
+Point geometry is the pole longitude/latitude. The runtime `id` should be derived from `signal_uid`, not display numbering, so changing `display_id` does not rename GLB nodes or break preview control.
+
+## Stable Identity
+
+Extend parsed OSM arm data to retain enough deterministic source identity (control node, way, adjacent arm direction/node). Generate a technical key from those source values. Do not use sorted array index or rounded heading as the primary key.
+
+If topology changes on a future `intermediates` run, the rebuilt GeoPackage may produce new identities. This is consistent with current road-edit lifecycle and is explicitly out of scope for MVP migration. Validation still reports duplicate identities and malformed source fields.
+
+## QGIS Integration
+
+- Add an auxiliary layer definition separate from the nine render layers.
+- Import it into the same GeoPackage after render layers.
+- Include it in the generated project but exclude it from the merged scene and 2D raster preview unless deliberately enabled for editing visibility.
+- Use a point marker plus rotated direction indicator driven by `heading_deg` and label by `display_id`, falling back to `signal_uid`.
+- Configure read-only/editor widgets where practical: technical/source ids read-only; phase group constrained to 0/1; numeric fields constrained to valid ranges; enabled as checkbox.
+
+## Reimport and Atomicity
+
+Extend the reimport layer manifest to include auxiliary editable layers while keeping render-scene merge derived only from `SCENE_LAYERS`. Export every layer into staging, parse and validate all editable features, then replace output files. Runtime JSON is written only after the staged auxiliary layer passes validation.
+
+## Compatibility
+
+- The next `intermediates` run bootstraps existing areas; no old JSON migration is required.
+- Main `.blend`/GLB geometry changes intentionally when a QGIS edit changes a signal.
+- Dynamic and countdown GLBs continue using runtime signal ids, now stable across ordinary reimport edits.
+- Current two-phase simulation remains unchanged.
+
+## Risks and Controls
+
+- **OSM way splitting changes source ids:** accepted across a full intermediates rebuild; ordinary reimport is stable.
+- **QGIS boolean/string coercion:** normalize known GDAL representations before strict validation and test the round-trip output.
+- **Accidental source-field editing:** mark technical fields read-only in QGIS and validate identity format during reimport.
+- **Partial overwrite on invalid auxiliary data:** retain the existing staging-before-replace discipline.
+- **Old spec conflict:** update pipeline specs that currently forbid traffic-signal anchors in GeoPackage, clarifying the distinction between editable assembly points and derived runtime anchors.
+
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/implement.jsonl b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/implement.jsonl
new file mode 100644
index 0000000..f965b3b
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/implement.jsonl
@@ -0,0 +1,6 @@
+{"file":".trellis/spec/pipeline/cli-and-stages.md","reason":"Traffic signal stage ownership, reimport lifecycle, manifests, and current anchor contract"}
+{"file":".trellis/spec/pipeline/layer-registry.md","reason":"Keep the auxiliary editable layer separate from the nine render layers and preserve their order"}
+{"file":".trellis/spec/pipeline/external-tools.md","reason":"GeoPackage import/export and staging-before-replace requirements"}
+{"file":".trellis/spec/guides/cross-layer-thinking-guide.md","reason":"OSM to GeoJSON/GPKG to Blender/Cesium contract review"}
+{"file":".trellis/spec/blender/asset-generation.md","reason":"Signal pose and dynamic asset generation constraints"}
+{"file":".trellis/spec/preview/vehicle-routes.md","reason":"Vehicle stop coordinates and runtime signal data coupling"}
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/implement.md b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/implement.md
new file mode 100644
index 0000000..98768ad
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/implement.md
@@ -0,0 +1,53 @@
+# Implementation Plan: QGIS Traffic Signal Overrides
+
+## 1. Contracts and Pure Logic
+
+- [x] Add an auxiliary editable-layer definition without modifying `SCENE_LAYERS` ordering.
+- [x] Extend OSM arm parsing with deterministic approach identity inputs.
+- [x] Split traffic-signal logic into automatic editable-feature generation, feature validation/normalization, and runtime pose derivation.
+- [x] Use stable technical ids for runtime signal ids; keep `display_id` as editable metadata.
+- [x] Add pure Node tests for T/cross counts, stable ids, movement/heading reconstruction, disabled features, duplicate ids, and invalid values.
+
+## 2. Intermediates and QGIS
+
+- [x] Write `traffic_signal_assemblies.geojson` after stop-line/intersection outputs are stable.
+- [x] Import the auxiliary point layer into the GeoPackage after the nine render layers.
+- [x] Extend generated QGIS project code with point/direction styling, labels, and field widgets/constraints.
+- [x] Confirm the auxiliary layer is excluded from merged road scene ordering and raster preview behavior.
+
+## 3. Reimport and Stage Ownership
+
+- [x] Extend `reimport-gpkg.js` to discover/export render and auxiliary layers through staging.
+- [x] Validate the staged editable layer before replacing any output artifact.
+- [x] Rebuild runtime `traffic_signals.json` from editable GeoJSON after `intermediates`, `reimport`, and at Blender entry.
+- [x] Remove Blender-entry OSM placement regeneration so QGIS edits remain authoritative.
+- [x] Extend stage manifests and diagnostics with auxiliary input/output records and feature counts.
+
+## 4. Cross-Layer Consumers
+
+- [x] Preserve `display_id` and stable runtime ids through Blender and Cesium metadata where useful.
+- [x] Verify static signal objects, dynamic lenses, countdown nodes, and vehicle stop behavior all consume the same enabled runtime records.
+- [x] Update pipeline specifications to replace the old prohibition with the editable-layer/derived-runtime distinction.
+
+## 5. Validation
+
+- [x] Run Node syntax checks and focused unit tests.
+- [x] Run existing preview-assets, preflight, budget, and relevant pipeline tests.
+- [x] Run `intermediates` and inspect the GeoPackage/QGIS project feature schema and styling.
+- [ ] Make a controlled QGIS edit to one signal (display id, point, heading), run `reimport,blender,cesium,preview`, and verify only the intended assembly changes. (`reimport` and Blender passed; Cesium/preview refresh was not repeated.)
+- [x] Confirm an invalid/duplicate edit fails before overwriting valid outputs.
+- [ ] Inspect Blender/Cesium structural digests and Safari preview for T and cross junctions. (Blocked this run by Blender 4.5.12 Metal startup SIGSEGV before project Python.)
+
+## Risky Files / Rollback Points
+
+- `scripts/lib/traffic-signals.js`: identity and pose contract; land pure tests before pipeline integration.
+- `scripts/build-osm2streets-qgis.js`: GeoPackage recreation and generated QGIS Python; verify auxiliary import independently before styling.
+- `scripts/reimport-gpkg.js`: atomic overwrite boundary; preserve staging semantics.
+- `scripts/build-area.js`: stage ownership; ensure Blender derives from editable GeoJSON rather than overwriting it.
+- `blender/osmassets/traffic_signals.py` and preview runtime should require minimal or no geometry changes; unexpected edits here indicate contract leakage.
+
+## Review Gate Before Start
+
+- [ ] User approves the final planning summary.
+- [ ] `prd.md`, `design.md`, and `implement.md` agree on full editable layer ownership and out-of-scope intermediates persistence.
+- [ ] No unresolved product decision remains.
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/notes.md b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/notes.md
new file mode 100644
index 0000000..dc97d04
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/notes.md
@@ -0,0 +1,14 @@
+# Debug Notes
+
+## 2026-08-07 countdown node-name regression
+
+Stable `signal_uid` values are intentionally descriptive and can exceed Blender's
+63-byte object-name limit. Using them directly in dynamic lens/countdown node
+names caused Blender to truncate names while Cesium looked up the untruncated
+strings. The countdown GLBs then exposed all digits without the runtime being
+able to hide the inactive values, appearing as overlapping/blurred numbers.
+
+Runtime signal records now carry a deterministic short `nodeKey` (`ts_` plus
+the first 16 hex characters of SHA-256 of `signal_uid`). Blender uses it for
+dynamic object names and Cesium uses the same key for lookups. Preview keeps a
+fallback to `signal.id` for older metadata files.
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/prd.md b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/prd.md
new file mode 100644
index 0000000..6488b26
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/prd.md
@@ -0,0 +1,67 @@
+# QGIS Traffic Signal Overrides
+
+## Goal
+
+Make every automatically generated vehicle traffic signal independently identifiable and editable in QGIS. A user must be able to assign a display number, move a pole, rotate its assembly, adjust supported placement attributes, run `reimport`, and have Blender and Cesium consume that edited result without OSM regeneration overwriting it.
+
+## Background
+
+- Current traffic signals are derived from OSM `highway=traffic_signals` controls, road topology, `vehicle_stop_lines.geojson`, and `intersection_surface.geojson` by `scripts/lib/traffic-signals.js`.
+- Current sequential ids such as `signal-1` depend on generation order and are not suitable as persistent edit identities.
+- Current `<geojsonDir>/traffic_signals.json` contains fully derived `pose.*` data but is deliberately excluded from the GeoPackage and QGIS project.
+- Existing road editing establishes the desired lifecycle: `intermediates` initializes a GeoPackage, the user edits it in QGIS, and `reimport` exports the edited data back to GeoJSON. Running `intermediates` again may discard manual edits; that behavior remains explicit and unchanged.
+
+## Requirements
+
+### R1. Editable auxiliary layer
+
+- `intermediates` must create a point FeatureCollection containing one feature per physical signal assembly and import it into the area GeoPackage.
+- The generated QGIS project must expose the layer with a visible directional symbol and a label suitable for identifying individual signals.
+- The auxiliary layer must not join `SCENE_LAYERS` or the merged road scene because it is an editing/control artifact, not a road render layer.
+
+### R2. Stable identity and numbering
+
+- Every generated feature must contain an immutable technical `signal_uid` derived deterministically from its OSM control and physical approach identity, rather than array order.
+- Every feature must contain an editable `display_id` intended for user-facing numbering.
+- Build/reimport validation must reject duplicate or missing `signal_uid` values and duplicate non-empty `display_id` values with an actionable error.
+
+### R3. Editable placement contract
+
+- Point geometry represents the pole ground position.
+- Editable attributes must include at least `display_id`, `heading_deg`, `phase_group`, `mast_reach_m`, `enabled`, and `z_offset_m`.
+- Source/control attributes required for matching and diagnostics must be preserved, including `control_id` and approach identity.
+- Vehicle stop coordinates remain independent attributes; moving the pole must not silently move the vehicle stop point.
+- After reimport, the pipeline must deterministically rebuild `pose.pole`, `pose.arm`, `pose.head`, `pose.lenses`, and `pose.countdown` from the edited point and attributes.
+
+### R4. Stage ownership
+
+- `intermediates` initializes the editable signal layer from current OSM/topology and derives the runtime `traffic_signals.json` from it.
+- `reimport` must stage, validate, and export the editable signal layer along with the existing road layers, then rebuild the runtime JSON.
+- `blender` must rebuild runtime `traffic_signals.json` from the current editable signal GeoJSON. It must not recompute signal placement directly from OSM and erase QGIS edits.
+- `cesium` and `preview` continue consuming artifacts derived from the same runtime JSON and retain matching signal node ids.
+
+### R5. Diagnostics and compatibility
+
+- Invalid geometry, invalid numeric fields, duplicate identities, unsupported phase groups, and unmatched source references must fail before replacing valid output artifacts.
+- `enabled=false` suppresses a signal without requiring feature deletion, so automatic regeneration cannot accidentally resurrect an intentionally disabled assembly within the same edit lifecycle.
+- Existing areas without an editable signal layer must receive one on their next `intermediates` run. No migration of previously hand-edited traffic signal JSON is required.
+
+## Acceptance Criteria
+
+- [ ] A clean `intermediates` run creates the editable traffic-signal GeoJSON, a GeoPackage layer with the same feature count, and a QGIS project layer with labels and directional symbols.
+- [ ] T junctions produce three editable features and cross junctions produce four, each with a unique deterministic `signal_uid`.
+- [ ] Moving one point in QGIS and changing its `display_id` and `heading_deg`, followed by `reimport,blender,cesium,preview`, changes only that signal assembly's placement/identity-facing metadata while preserving its vehicle stop point.
+- [ ] Re-running `blender` after reimport does not overwrite the QGIS-edited pole position or heading from OSM.
+- [ ] Setting one feature to disabled removes its static and dynamic signal assets while leaving the other signals intact.
+- [ ] Duplicate `signal_uid` or non-empty `display_id`, invalid geometry, and invalid placement fields abort reimport without partially replacing GeoJSON outputs.
+- [ ] Blender/Cesium node counts and ids match the enabled features in the final runtime JSON; lights and countdowns continue switching correctly.
+- [ ] Existing road GeoPackage import/reimport behavior and merged scene layer order remain unchanged.
+- [ ] Unit/integration tests cover stable ids, editable-feature validation, override-to-pose reconstruction, auxiliary GeoPackage round-trip, and stage ownership.
+
+## Out Of Scope
+
+- Preserving QGIS edits across a subsequent full `intermediates` rebuild; as with road edits, users must preserve or reapply edits before regenerating the GeoPackage.
+- A complete traffic-controller timing editor or arbitrary multi-phase signal program.
+- Independent editing of each lens or countdown glyph position; those remain derived from the assembly point, heading, and shared layout.
+- Automatically assigning a stable identity to a brand-new signal feature drawn manually in QGIS.
+
diff --git a/.trellis/tasks/08-07-qgis-traffic-signal-overrides/task.json b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/task.json
new file mode 100644
index 0000000..afe91b0
--- /dev/null
+++ b/.trellis/tasks/08-07-qgis-traffic-signal-overrides/task.json
@@ -0,0 +1,26 @@
+{
+  "id": "qgis-traffic-signal-overrides",
+  "name": "qgis-traffic-signal-overrides",
+  "title": "QGIS traffic signal overrides",
+  "description": "",
+  "status": "in_progress",
+  "dev_type": null,
+  "scope": null,
+  "package": null,
+  "priority": "P2",
+  "creator": "dingkang",
+  "assignee": "dingkang",
+  "createdAt": "2026-08-07",
+  "completedAt": null,
+  "branch": null,
+  "base_branch": "main",
+  "worktree_path": null,
+  "commit": null,
+  "pr_url": null,
+  "subtasks": [],
+  "children": [],
+  "parent": null,
+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}
\ No newline at end of file
diff --git a/assets/qgis/traffic-signal-direction.svg b/assets/qgis/traffic-signal-direction.svg
new file mode 100644
index 0000000..1aef48a
--- /dev/null
+++ b/assets/qgis/traffic-signal-direction.svg
@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
+  <path d="M 50 96 L 24 50 L 76 50 Z"
+        fill="#e12d37" stroke="#7d0f19" stroke-width="4" stroke-linejoin="round"/>
+</svg>
diff --git a/blender/osmassets/traffic_signals.py b/blender/osmassets/traffic_signals.py
index c417312..1417207 100644
--- a/blender/osmassets/traffic_signals.py
+++ b/blender/osmassets/traffic_signals.py
@@ -129,8 +129,9 @@ def assemble_dynamic(signal_data, projector, collection, materials):
         active_lens_depth = min(0.025, layout["lensDepthMeters"])
         active_lens_radius = layout["lensRadiusMeters"] * 0.88
         active_lens_offset = (layout["lensDepthMeters"] + active_lens_depth) / 2 + 0.003
+        node_key = signal.get("nodeKey") or signal["id"]
         for state in ("red", "yellow", "green"):
-            batch = MeshBatch("TrafficSignalDynamic_%s_%s" % (signal["id"], state), collection, materials[state])
+            batch = MeshBatch("TrafficSignalDynamic_%s_%s" % (node_key, state), collection, materials[state])
             for index in (0, 1, 2):
                 point = pose["lenses"][index]
                 if point["state"] == state:
@@ -149,7 +150,7 @@ def assemble_dynamic(signal_data, projector, collection, materials):
         phase_group = int(signal.get("phaseGroup") or 0) % 2
         for value, mesh in countdown_meshes[phase_group].items():
             objects.append(_countdown_instance(
-                "TrafficSignalDynamic_%s_countdown_%s" % (signal["id"], value),
+                "TrafficSignalDynamic_%s_countdown_%s" % (node_key, value),
                 mesh, collection, text_x, text_y, board_z, lateral, face))
     return objects
 
diff --git a/package.json b/package.json
index 5d6783f..7190021 100644
--- a/package.json
+++ b/package.json
@@ -16,6 +16,7 @@
     "test:preview-assets": "node scripts/test-preview-assets.js",
     "test:compress-glb": "node scripts/test-compress-glb.js",
     "test:turn-lane-arrows": "node scripts/test-turn-lane-arrows.js",
+    "test:traffic-signals": "node scripts/test-traffic-signals.js",
     "render:turn-lane-arrow-samples": "node scripts/render-turn-lane-arrow-samples.js"
   },
   "dependencies": {
diff --git a/scripts/build-area.js b/scripts/build-area.js
index 8156306..a930609 100755
--- a/scripts/build-area.js
+++ b/scripts/build-area.js
@@ -153,6 +153,7 @@ function writeDerivedConfig(area) {
     gpkg: area.outputs.gpkg,
     project: area.outputs.qgisProject,
     preview: area.outputs.qgisPreview,
+    trafficSignalAssemblies: area.outputs.trafficSignalAssemblies,
     arrowScale: area.qgis.arrowScale,
     arrowMergeTriangles: area.qgis.arrowMergeTriangles,
     arrowOutlineSimplifyMeters: area.qgis.arrowOutlineSimplifyMeters,
@@ -200,6 +201,7 @@ function buildIntermediates(area) {
       derivedConfig: fileRecord(derivedConfigPath),
       geojsonDir: fileRecord(area.outputs.geojsonDir),
       ...sceneGeojsonRecords(area),
+      trafficSignalAssemblies: fileRecord(area.outputs.trafficSignalAssemblies),
       trafficSignals: fileRecord(area.outputs.trafficSignals),
       gpkg: fileRecord(area.outputs.gpkg),
       qgisProject: fileRecord(area.outputs.qgisProject),
@@ -207,6 +209,7 @@ function buildIntermediates(area) {
     },
     summary: {
       geojson: geojsonFeatureCounts(area),
+      trafficSignalAssemblies: featureCount(area.outputs.trafficSignalAssemblies),
     },
     warnings: [],
   });
@@ -241,10 +244,12 @@ function reimportGpkg(area) {
     outputs: {
       geojsonDir: fileRecord(area.outputs.geojsonDir),
       ...sceneGeojsonRecords(area),
+      trafficSignalAssemblies: fileRecord(area.outputs.trafficSignalAssemblies),
       trafficSignals: fileRecord(area.outputs.trafficSignals),
     },
     summary: {
       geojson: geojsonFeatureCounts(area),
+      trafficSignalAssemblies: featureCount(area.outputs.trafficSignalAssemblies),
     },
     warnings: [],
   });
@@ -253,10 +258,9 @@ function reimportGpkg(area) {
 function buildBlenderScene(area) {
   ensureFile(blenderExecutable(area), "Blender executable");
   ensureFile(path.join(repoRoot, "blender", "generate_scene.py"), "Blender scene generator");
-  // Traffic signal anchors are derived from the current OSM input plus the
-  // normalized stop-line/intersection layers. Regenerate them for every
-  // Blender build so partial runs cannot reuse a stale signal topology after
-  // the source OSM has changed.
+  ensureFile(area.outputs.trafficSignalAssemblies, "Editable traffic signal assemblies");
+  // Blender consumes the editable assembly layer; OSM only initializes it in
+  // intermediates, so QGIS edits remain authoritative across later stages.
   writeTrafficSignals(area);
   ensureFile(area.outputs.trafficSignals, "Traffic signal anchors");
   fs.mkdirSync(path.dirname(area.outputs.blend), { recursive: true });
@@ -300,6 +304,7 @@ function buildBlenderScene(area) {
       osm: fileRecord(area.input),
       geojsonDir: fileRecord(area.outputs.geojsonDir),
       ...sceneGeojsonRecords(area),
+      trafficSignalAssemblies: fileRecord(area.outputs.trafficSignalAssemblies),
       trafficSignals: fileRecord(area.outputs.trafficSignals),
     },
     outputs: {
@@ -529,11 +534,7 @@ function writeCesiumPreview(area) {
 }
 
 function writeTrafficSignals(area) {
-  const signals = readTrafficSignals(
-    path.join(area.outputs.geojsonDir, "vehicle_stop_lines.geojson"),
-    path.join(area.outputs.geojsonDir, "intersection_surface.geojson"),
-    area.input,
-  );
+  const signals = readTrafficSignals(area.outputs.trafficSignalAssemblies, area.input);
   fs.writeFileSync(area.outputs.trafficSignals, `${JSON.stringify(signals, null, 2)}\n`);
   console.log(`Traffic signals: ${signals.signals.length} anchors in ${area.outputs.trafficSignals}`);
 }
diff --git a/scripts/build-osm2streets-qgis.js b/scripts/build-osm2streets-qgis.js
index 47ce5ee..0208d79 100755
--- a/scripts/build-osm2streets-qgis.js
+++ b/scripts/build-osm2streets-qgis.js
@@ -7,8 +7,10 @@ const { execFileSync } = require("child_process");
 const { JsStreetNetwork } = require("osm2streets-js-node");
 const { qgisPaths } = require("./lib/tool-paths");
 const { buildCustomTurnLaneArrows } = require("./lib/turn-lane-arrows");
+const { readTrafficSignalFeatures } = require("./lib/traffic-signals");
 const {
   SCENE_LAYERS,
+  AUXILIARY_EDIT_LAYERS,
   SCENE_FILE,
   SCENE_STYLE_FILE,
   layerFile,
@@ -39,6 +41,11 @@ const clipPad = Number(config.clipPad);
 const canvasPad = Number(config.canvasPad);
 const previewPad = Number(config.previewPad);
 const layerPrefix = config.layerPrefix || "osm2streets";
+const trafficSignalLayer = AUXILIARY_EDIT_LAYERS.find((layer) => layer.id === "traffic_signal_assemblies");
+if (!trafficSignalLayer) throw new Error("Missing traffic_signal_assemblies auxiliary layer definition");
+const trafficSignalAssembliesPath = path.resolve(
+  config.trafficSignalAssemblies || path.join(outDir, trafficSignalLayer.file),
+);
 
 if (!Number.isFinite(arrowScale) || arrowScale <= 0) {
   throw new Error(`Invalid arrowScale: ${config.arrowScale}`);
@@ -116,6 +123,11 @@ fs.writeFileSync(
 for (const layer of SCENE_LAYERS) {
   writeJson(path.join(outDir, layerFile(layer)), split[layer.splitKey]);
 }
+writeJson(trafficSignalAssembliesPath, readTrafficSignalFeatures(
+  path.join(outDir, "vehicle_stop_lines.geojson"),
+  path.join(outDir, "intersection_surface.geojson"),
+  inputPath,
+));
 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"));
@@ -134,6 +146,7 @@ const ogrEnv = qgis.env;
 SCENE_LAYERS.forEach((layer, index) => {
   importLayer(gpkgPath, path.join(outDir, layerFile(layer)), layer.id, index > 0, ogrEnv);
 });
+importLayer(gpkgPath, trafficSignalAssembliesPath, trafficSignalLayer.id, true, ogrEnv);
 
 const qgisScript = path.join(outDir, "_create_qgis_project.py");
 const previewFeature = split.crosswalks.features[0] || split.laneArrows.features[0] || split.roadSurface.features[0];
@@ -149,6 +162,7 @@ fs.writeFileSync(qgisScript, makeQgisScript({
   layerPrefix,
   canvasExtent: config.canvasExtent || extentString(expandBounds(bbox, canvasPad)),
   previewExtent: config.previewExtent || defaultPreviewExtent,
+  trafficSignalSymbolPath: path.join(repoRoot, "assets", "qgis", "traffic-signal-direction.svg"),
 }));
 
 execFileSync(qgisPython, [qgisScript], {
@@ -1437,16 +1451,24 @@ from qgis.PyQt.QtGui import QColor, QImage, QPainter
 from qgis.core import (
     QgsApplication,
     QgsCoordinateReferenceSystem,
+    QgsEditorWidgetSetup,
     QgsFillSymbol,
+    QgsMarkerSymbol,
     QgsMapRendererCustomPainterJob,
     QgsMapSettings,
     QgsProject,
+    QgsPalLayerSettings,
+    QgsProperty,
     QgsRectangle,
     QgsSingleSymbolRenderer,
+    QgsSymbolLayer,
+    QgsSvgMarkerSymbolLayer,
+    QgsVectorLayerSimpleLabeling,
     QgsVectorLayer,
 )
 
 QGIS_PREFIX = ${JSON.stringify(options.qgisPrefix)}
+TRAFFIC_SIGNAL_SYMBOL = ${JSON.stringify(options.trafficSignalSymbolPath)}
 GPKG = ${JSON.stringify(options.gpkgPath)}
 PROJECT_PATH = ${JSON.stringify(options.projectPath)}
 PREVIEW_PATH = ${JSON.stringify(options.previewPath)}
@@ -1475,6 +1497,38 @@ def make_layer(layer_name, title, color, outline="0,0,0,0", outline_width="0"):
     layer.setRenderer(QgsSingleSymbolRenderer(fill_symbol(color, outline, outline_width)))
     return layer
 
+def make_signal_layer():
+    layer = QgsVectorLayer(f"{GPKG}|layername=traffic_signal_assemblies", f"{LAYER_PREFIX} traffic signal assemblies", "ogr")
+    if not layer.isValid():
+        raise RuntimeError("Invalid traffic signal assemblies layer")
+    symbol = QgsMarkerSymbol()
+    svg_layer = QgsSvgMarkerSymbolLayer(TRAFFIC_SIGNAL_SYMBOL, 9)
+    svg_layer.setDataDefinedProperty(
+        QgsSymbolLayer.Property.Angle,
+        QgsProperty.fromField("heading_deg"),
+    )
+    symbol.changeSymbolLayer(0, svg_layer)
+    layer.setRenderer(QgsSingleSymbolRenderer(symbol))
+    labels = QgsPalLayerSettings()
+    labels.fieldName = "if(trim(display_id) = '', signal_uid, display_id)"
+    labels.isExpression = True
+    layer.setLabeling(QgsVectorLayerSimpleLabeling(labels))
+    layer.setLabelsEnabled(True)
+    for field_name in ("signal_uid", "control_id", "approach_id", "source_way_id", "stop_lon", "stop_lat"):
+        index = layer.fields().indexOf(field_name)
+        if index >= 0:
+            layer.setFieldConstraint(index, 1)
+            form = layer.editFormConfig()
+            form.setReadOnly(index, True)
+            layer.setEditFormConfig(form)
+    enabled_index = layer.fields().indexOf("enabled")
+    if enabled_index >= 0:
+        layer.setEditorWidgetSetup(enabled_index, QgsEditorWidgetSetup("CheckBox", {"CheckedState": "1", "UncheckedState": "0"}))
+    phase_index = layer.fields().indexOf("phase_group")
+    if phase_index >= 0:
+        layer.setEditorWidgetSetup(phase_index, QgsEditorWidgetSetup("ValueMap", {"map": [{"Phase 0": 0}, {"Phase 1": 1}]}))
+    return layer
+
 QgsApplication.setPrefixPath(QGIS_PREFIX, True)
 app = QgsApplication([], False)
 app.initQgis()
@@ -1495,12 +1549,16 @@ layers = {
     )
     for spec in LAYER_SPECS
 }
+signal_layer = make_signal_layer()
+layers["traffic_signal_assemblies"] = signal_layer
 draw_order = [spec["id"] for spec in LAYER_SPECS]
 for key in draw_order:
     project.addMapLayer(layers[key], False)
+project.addMapLayer(signal_layer, False)
 root = project.layerTreeRoot()
 for key in draw_order:
     root.insertLayer(0, layers[key])
+root.insertLayer(0, signal_layer)
 if not project.write(PROJECT_PATH):
     raise RuntimeError(f"Failed to write {PROJECT_PATH}")
 
diff --git a/scripts/lib/area-config.js b/scripts/lib/area-config.js
index eda1ce9..0191615 100644
--- a/scripts/lib/area-config.js
+++ b/scripts/lib/area-config.js
@@ -58,8 +58,11 @@ function normalizeAreaConfig(raw, options = {}) {
     ),
     vehicleRoute: path.resolve(outputOverrides.vehicleRoute || path.join(areaDir, `${fileStem}-vehicle-route.json`)),
     vehicleModel: path.resolve(outputOverrides.vehicleModel || path.join(areaDir, `${fileStem}-vehicle-car.gltf`)),
-    // Signals are an auxiliary intermediates artifact shared by Blender and
-    // the browser preview. They deliberately are not one of the QGIS layers.
+    trafficSignalAssemblies: path.resolve(
+      outputOverrides.trafficSignalAssemblies || path.join(geojsonDir, "traffic_signal_assemblies.geojson"),
+    ),
+    // Runtime poses are derived from the editable assembly layer and shared by
+    // Blender and the browser preview.
     trafficSignals: path.resolve(outputOverrides.trafficSignals || path.join(geojsonDir, "traffic_signals.json")),
     pipelineDir,
     stageManifestDir: path.resolve(outputOverrides.stageManifestDir || path.join(pipelineDir, "stages")),
diff --git a/scripts/lib/area-diagnostics.js b/scripts/lib/area-diagnostics.js
index b3a8fd5..94f29b4 100644
--- a/scripts/lib/area-diagnostics.js
+++ b/scripts/lib/area-diagnostics.js
@@ -327,6 +327,8 @@ function artifactStatus(area) {
     ["GeoPackage", area.outputs.gpkg, true, "file"],
     ["QGIS project", area.outputs.qgisProject, true, "file"],
     ["QGIS preview", area.outputs.qgisPreview, true, "file"],
+    ["Traffic signal assemblies", area.outputs.trafficSignalAssemblies, true, "file"],
+    ["Traffic signal runtime", area.outputs.trafficSignals, true, "file"],
     ["Blend scene", area.outputs.blend, true, "file"],
     ["Render PNG", area.outputs.render, true, "file"],
     ["Cesium GLB", area.outputs.glb, true, "file"],
@@ -400,6 +402,8 @@ function stageManifestStatus(area, configPath = null) {
         derivedConfig,
         geojsonDir: area.outputs.geojsonDir,
         ...sceneGeojsonFiles(area),
+        trafficSignalAssemblies: area.outputs.trafficSignalAssemblies,
+        trafficSignals: area.outputs.trafficSignals,
         gpkg: area.outputs.gpkg,
         qgisProject: area.outputs.qgisProject,
         qgisPreview: optionalExpectedFile(area.outputs.qgisPreview),
@@ -416,6 +420,8 @@ function stageManifestStatus(area, configPath = null) {
       outputs: {
         geojsonDir: area.outputs.geojsonDir,
         ...sceneGeojsonFiles(area),
+        trafficSignalAssemblies: area.outputs.trafficSignalAssemblies,
+        trafficSignals: area.outputs.trafficSignals,
       },
     },
     {
@@ -426,6 +432,8 @@ function stageManifestStatus(area, configPath = null) {
         osm: area.input,
         geojsonDir: area.outputs.geojsonDir,
         ...sceneGeojsonFiles(area),
+        trafficSignalAssemblies: area.outputs.trafficSignalAssemblies,
+        trafficSignals: area.outputs.trafficSignals,
       },
       outputs: {
         blend: area.outputs.blend,
diff --git a/scripts/lib/cesium-preview.js b/scripts/lib/cesium-preview.js
index 7fabdb5..75e536b 100644
--- a/scripts/lib/cesium-preview.js
+++ b/scripts/lib/cesium-preview.js
@@ -514,11 +514,12 @@
         let changed = false;
         const groupPhases = new Map();
         for (const signal of signals) {
+          const nodeKey = signal.nodeKey || signal.id;
           const phase = signalPhase(signal.phaseGroup, phaseTime, start);
           groupPhases.set(signal.phaseGroup, phase.active);
           if (signal === signals[0]) state.phase = `${phase.active} ${String(phase.remaining).padStart(2, "0")}`;
           for (const state of ["red", "yellow", "green"]) {
-            const value = node(`TrafficSignalDynamic_${signal.id}_${state}`);
+            const value = node(`TrafficSignalDynamic_${nodeKey}_${state}`);
             if (value && value.show !== (state === phase.active)) {
               value.show = state === phase.active;
               changed = true;
@@ -527,7 +528,7 @@
           const visibleCountdown = String(phase.remaining).padStart(2, "0");
           const countdownModel = countdownModels.get(Number(signal.phaseGroup));
           for (let value = 0; value < 20; value += 1) {
-            const name = `TrafficSignalDynamic_${signal.id}_countdown_${String(value).padStart(2, "0")}`;
+            const name = `TrafficSignalDynamic_${nodeKey}_countdown_${String(value).padStart(2, "0")}`;
             let countdown = null;
             countdown = countdownNode(countdownModel, name);
             if (countdown && countdown.show !== (String(value).padStart(2, "0") === visibleCountdown)) {
diff --git a/scripts/lib/osm.js b/scripts/lib/osm.js
index c192df3..03e8f75 100644
--- a/scripts/lib/osm.js
+++ b/scripts/lib/osm.js
@@ -44,7 +44,11 @@ function parseOsm(xml) {
           const neighbor = way.refs[neighborIndex];
           if (!neighbor || !nodes.has(neighbor)) continue;
           const neighborPoint = nodes.get(neighbor);
-          arms.push({ headingDegrees: headingBetween(control, neighborPoint), wayId: way.id });
+          arms.push({
+            headingDegrees: headingBetween(control, neighborPoint),
+            wayId: String(way.id),
+            neighborNodeId: String(neighbor),
+          });
         }
       }
     }
diff --git a/scripts/lib/scene-layers.js b/scripts/lib/scene-layers.js
index faceb3a..2b2c4d8 100644
--- a/scripts/lib/scene-layers.js
+++ b/scripts/lib/scene-layers.js
@@ -97,6 +97,17 @@ const SCENE_LAYERS = [
   },
 ];
 
+// Editable control layers share the GeoPackage/QGIS lifecycle but never enter
+// the merged render scene or its draw order.
+const AUXILIARY_EDIT_LAYERS = [
+  {
+    id: "traffic_signal_assemblies",
+    file: "traffic_signal_assemblies.geojson",
+    title: "traffic signal assemblies",
+    geometry: "Point",
+  },
+];
+
 const SCENE_FILE = "osm2streets_scene.geojson";
 const SCENE_STYLE_FILE = "osm2streets_scene_style.json";
 
@@ -155,6 +166,7 @@ function qgisRgba(hex, alpha = 255) {
 
 module.exports = {
   SCENE_LAYERS,
+  AUXILIARY_EDIT_LAYERS,
   SCENE_FILE,
   SCENE_STYLE_FILE,
   layerFile,
diff --git a/scripts/lib/traffic-signals.js b/scripts/lib/traffic-signals.js
index 1101fe6..859cd01 100644
--- a/scripts/lib/traffic-signals.js
+++ b/scripts/lib/traffic-signals.js
@@ -1,39 +1,24 @@
 "use strict";
 
 const fs = require("fs");
+const crypto = require("crypto");
 const { parseOsm } = require("./osm");
 
 const EARTH_RADIUS = 6371008.8;
 const CURB_OFFSET_METERS = 5.2;
 const MAST_REACH_METERS = 4.5;
-// This layout is serialized with the anchors so Blender's static structure and
-// Cesium's dynamic overlay cannot independently drift in size or handedness.
-// Lateral offsets use the approach travel direction: positive is the driver's
-// right. The countdown board therefore sits at +1.15m from the signal head.
 const SIGNAL_LAYOUT = Object.freeze({
-  poleHeightMeters: 6.7,
-  poleRadiusMeters: 0.13,
-  armWidthMeters: 0.21,
-  // The mast arm and the signal head share this centre elevation.
-  mastHeightMeters: 6.25,
-  headCenterHeightMeters: 6.25,
-  headWidthMeters: 0.68,
-  headDepthMeters: 0.30,
-  headBodyHeightMeters: 1.62,
-  lensRadiusMeters: 0.22,
-  lensDepthMeters: 0.07,
-  lensFaceOffsetMeters: 0.18,
+  poleHeightMeters: 6.7, poleRadiusMeters: 0.13, armWidthMeters: 0.21,
+  mastHeightMeters: 6.25, headCenterHeightMeters: 6.25,
+  headWidthMeters: 0.68, headDepthMeters: 0.30, headBodyHeightMeters: 1.62,
+  lensRadiusMeters: 0.22, lensDepthMeters: 0.07, lensFaceOffsetMeters: 0.18,
   lensVerticalOffsetsMeters: [0.49, -0.01, -0.51],
-  countdownLateralMeters: 1.15,
-  countdownFaceOffsetMeters: 0.05,
-  countdownWidthMeters: 0.82,
-  countdownDepthMeters: 0.14,
-  countdownHeightMeters: 0.56,
-  // The countdown board is fixed on the mast arm, not hung below it.
-  countdownVerticalOffsetMeters: 0.0,
+  countdownLateralMeters: 1.15, countdownFaceOffsetMeters: 0.05,
+  countdownWidthMeters: 0.82, countdownDepthMeters: 0.14,
+  countdownHeightMeters: 0.56, countdownVerticalOffsetMeters: 0.0,
 });
 
-function buildTrafficSignals(stopLines, intersections, controls = []) {
+function buildTrafficSignalFeatures(stopLines, intersections, controls = []) {
   const centers = (intersections.features || []).map((feature, index) => {
     const point = polygonCenter(feature.geometry);
     return { id: `intersection-${index + 1}`, point, radius: polygonRadius(feature.geometry, point) };
@@ -46,215 +31,238 @@ function buildTrafficSignals(stopLines, intersections, controls = []) {
     if (!intersection || metersBetween(center, intersection.point) > 32) continue;
     const axis = roadAxis(feature.geometry, center, intersection.point);
     if (!axis) continue;
-    // A vehicle signal belongs beyond the junction, facing back toward the
-    // approaching stop line. Use the far edge of the intersection, never the
-    // near-side stop-line area where it would read as a pedestrian signal.
     const right = [axis[1], -axis[0]];
     const farSide = moveMeters(intersection.point, axis, intersection.radius + 3.2);
-    // The pole is on the far-side sidewalk, not at the stop line or inside
-    // the intersection. Its mast then reaches back above the approach lanes.
-    const point = moveMeters(farSide, right, CURB_OFFSET_METERS);
     candidates.push({
-      intersectionId: intersection.id,
-      center,
-      axis,
-      point,
+      intersectionId: intersection.id, center, axis,
+      point: moveMeters(farSide, right, CURB_OFFSET_METERS),
       headingDegrees: normalizeDegrees(Math.atan2(axis[0], axis[1]) * 180 / Math.PI),
     });
   }
-  const signals = [];
+  const features = [];
   for (const control of controls) {
     const controlPoint = [Number(control.longitude), Number(control.latitude)];
-    if (!controlPoint.every(Number.isFinite)) continue;
-    // A traffic-signal node on a through road is not a controlled vehicle
-    // junction. Its connected motor-road arms are the source of truth.
-    if (!Array.isArray(control.arms) || control.arms.length < 3) continue;
+    if (!controlPoint.every(Number.isFinite) || !Array.isArray(control.arms) || control.arms.length < 3) continue;
     const intersection = nearestCenter(controlPoint, centers);
     if (!intersection || metersBetween(controlPoint, intersection.point) > 32) continue;
-    const arms = matchOsmArms(candidates.filter((candidate) => candidate.intersectionId === intersection.id), controlPoint, control.arms);
+    const arms = matchOsmArms(candidates.filter((item) => item.intersectionId === intersection.id), controlPoint, control.arms);
     const groups = phaseGroups(arms);
-    for (const [index, candidate] of arms.entries()) {
-      signals.push({
-        id: `signal-${signals.length + 1}`,
-        controlId: String(control.id || ""),
-        intersectionId: intersection.id,
-        phaseGroup: groups[index],
-        longitude: candidate.point[0],
-        latitude: candidate.point[1],
-        stopLongitude: candidate.center[0],
-        stopLatitude: candidate.center[1],
-        headingDegrees: candidate.headingDegrees,
-        mastReachMeters: MAST_REACH_METERS,
-        pose: buildSignalPose(candidate.point, candidate.axis, MAST_REACH_METERS),
+    arms.forEach((candidate, index) => {
+      const fallbackArmId = `heading-${Math.round(normalizeDegrees(candidate.osmArm?.headingDegrees || 0) * 1000)}`;
+      const sourceWayId = String(candidate.osmArm?.wayId || "legacy");
+      const neighborNodeId = String(candidate.osmArm?.neighborNodeId || fallbackArmId);
+      const approachId = `${sourceWayId}:${neighborNodeId}`;
+      const signalUid = `osm-${String(control.id)}-${sourceWayId}-${neighborNodeId}`;
+      features.push({
+        type: "Feature",
+        geometry: { type: "Point", coordinates: candidate.point.slice() },
+        properties: {
+          signal_uid: signalUid, display_id: signalUid, control_id: String(control.id),
+          approach_id: approachId, source_way_id: sourceWayId,
+          heading_deg: candidate.headingDegrees, phase_group: groups[index],
+          mast_reach_m: MAST_REACH_METERS,
+          stop_lon: candidate.center[0], stop_lat: candidate.center[1],
+          enabled: true, z_offset_m: 0,
+        },
       });
-    }
+    });
   }
+  return validateTrafficSignalFeatures({ type: "FeatureCollection", features });
+}
+
+function validateTrafficSignalFeatures(collection) {
+  if (collection?.type !== "FeatureCollection" || !Array.isArray(collection.features)) {
+    throw new Error("Traffic signal assemblies must be a FeatureCollection");
+  }
+  const uids = new Set();
+  const displayIds = new Set();
+  const features = collection.features.map((feature, index) => {
+    const label = `traffic signal feature ${index + 1}`;
+    if (feature?.geometry?.type !== "Point" || !Array.isArray(feature.geometry.coordinates) ||
+        feature.geometry.coordinates.length < 2 || !feature.geometry.coordinates.slice(0, 2).every(Number.isFinite)) {
+      throw new Error(`${label}: geometry must be a finite Point`);
+    }
+    const input = feature.properties || {};
+    const text = (key, required = true) => {
+      const value = input[key] == null ? "" : String(input[key]).trim();
+      if (required && !value) throw new Error(`${label}: missing ${key}`);
+      return value;
+    };
+    const number = (key, options = {}) => {
+      if (input[key] === null || input[key] === undefined || input[key] === "") {
+        throw new Error(`${label}: missing ${key}`);
+      }
+      const value = Number(input[key]);
+      if (!Number.isFinite(value) || (options.min != null && value < options.min) || (options.max != null && value > options.max)) {
+        throw new Error(`${label}: invalid ${key} '${input[key]}'`);
+      }
+      return value;
+    };
+    const signalUid = text("signal_uid");
+    if (!/^osm-[A-Za-z0-9_.:-]+$/.test(signalUid)) throw new Error(`${label}: invalid signal_uid '${signalUid}'`);
+    if (uids.has(signalUid)) throw new Error(`Duplicate signal_uid '${signalUid}'`);
+    uids.add(signalUid);
+    const displayId = text("display_id", false);
+    if (displayId && displayIds.has(displayId)) throw new Error(`Duplicate display_id '${displayId}'`);
+    if (displayId) displayIds.add(displayId);
+    const phaseGroup = number("phase_group", { min: 0, max: 1 });
+    if (!Number.isInteger(phaseGroup)) throw new Error(`${label}: phase_group must be 0 or 1`);
+    const enabled = normalizeBoolean(input.enabled, label);
+    const controlId = text("control_id");
+    const approachId = text("approach_id");
+    const sourceWayId = text("source_way_id");
+    if (!approachId.startsWith(`${sourceWayId}:`)) throw new Error(`${label}: approach_id does not match source_way_id`);
+    const expectedUid = `osm-${controlId}-${approachId.replace(":", "-")}`;
+    if (signalUid !== expectedUid) throw new Error(`${label}: signal_uid does not match source identity (expected '${expectedUid}')`);
+    return {
+      type: "Feature",
+      geometry: { type: "Point", coordinates: feature.geometry.coordinates.slice(0, 2).map(Number) },
+      properties: {
+        ...input, signal_uid: signalUid, display_id: displayId,
+        control_id: controlId, approach_id: approachId,
+        source_way_id: sourceWayId, heading_deg: normalizeDegrees(number("heading_deg")),
+        phase_group: phaseGroup, mast_reach_m: number("mast_reach_m", { min: 0.1, max: 30 }),
+        stop_lon: number("stop_lon", { min: -180, max: 180 }),
+        stop_lat: number("stop_lat", { min: -90, max: 90 }),
+        enabled, z_offset_m: number("z_offset_m", { min: -20, max: 100 }),
+      },
+    };
+  });
+  return { type: "FeatureCollection", features };
+}
+
+function buildTrafficSignalsFromFeatures(collection) {
+  const normalized = validateTrafficSignalFeatures(collection);
+  const signals = normalized.features.filter((feature) => feature.properties.enabled).map((feature) => {
+    const p = feature.properties;
+    const point = feature.geometry.coordinates;
+    const axis = headingVector(p.heading_deg);
+    return {
+      id: p.signal_uid, signalUid: p.signal_uid, displayId: p.display_id,
+      nodeKey: signalNodeKey(p.signal_uid),
+      controlId: p.control_id, approachId: p.approach_id, sourceWayId: p.source_way_id,
+      phaseGroup: p.phase_group, longitude: point[0], latitude: point[1],
+      stopLongitude: p.stop_lon, stopLatitude: p.stop_lat,
+      headingDegrees: p.heading_deg, mastReachMeters: p.mast_reach_m,
+      zOffsetMeters: p.z_offset_m,
+      pose: buildSignalPose(point, axis, p.mast_reach_m, p.z_offset_m),
+    };
+  });
   return { version: 3, layout: SIGNAL_LAYOUT, signals };
 }
 
-function uniqueApproachArms(candidates, controlPoint) {
-  const sorted = candidates.map((candidate) => ({
-    ...candidate,
-    armHeading: normalizeDegrees(headingBetween(controlPoint, candidate.center)),
-    controlDistance: metersBetween(controlPoint, candidate.center),
-  })).sort((a, b) => a.armHeading - b.armHeading || a.controlDistance - b.controlDistance);
-  const arms = [];
-  for (const candidate of sorted) {
-    const duplicate = arms.find((arm) => angularDistance(arm.armHeading, candidate.armHeading) <= 25);
-    if (!duplicate) arms.push(candidate);
+function signalNodeKey(signalUid) {
+  return `ts_${crypto.createHash("sha256").update(signalUid).digest("hex").slice(0, 16)}`;
+}
+
+function validateTrafficSignalSourceReferences(collection, controls) {
+  const normalized = validateTrafficSignalFeatures(collection);
+  const approachesByControl = new Map((controls || []).map((control) => [
+    String(control.id),
+    new Set((control.arms || []).map((arm) => `${String(arm.wayId)}:${String(arm.neighborNodeId)}`)),
+  ]));
+  for (const [index, feature] of normalized.features.entries()) {
+    const { control_id: controlId, approach_id: approachId } = feature.properties;
+    const approaches = approachesByControl.get(controlId);
+    if (!approaches) {
+      throw new Error(`traffic signal feature ${index + 1}: control_id '${controlId}' is not present in the current OSM`);
+    }
+    if (!approaches.has(approachId)) {
+      throw new Error(
+        `traffic signal feature ${index + 1}: approach_id '${approachId}' is not present on OSM control '${controlId}'`,
+      );
+    }
   }
+  return normalized;
+}
+
+function buildTrafficSignals(stopLines, intersections, controls = []) {
+  return buildTrafficSignalsFromFeatures(buildTrafficSignalFeatures(stopLines, intersections, controls));
+}
+
+function readTrafficSignalFeatures(stopLinePath, intersectionPath, osmPath) {
+  const controls = parseOsm(fs.readFileSync(osmPath, "utf8")).trafficSignalControls;
+  return buildTrafficSignalFeatures(
+    JSON.parse(fs.readFileSync(stopLinePath, "utf8")),
+    JSON.parse(fs.readFileSync(intersectionPath, "utf8")), controls,
+  );
+}
+
+function readTrafficSignals(editablePath, osmPath = null) {
+  const collection = JSON.parse(fs.readFileSync(editablePath, "utf8"));
+  if (osmPath) {
+    const controls = parseOsm(fs.readFileSync(osmPath, "utf8")).trafficSignalControls;
+    validateTrafficSignalSourceReferences(collection, controls);
+  }
+  return buildTrafficSignalsFromFeatures(collection);
+}
+
+function normalizeBoolean(value, label) {
+  if (value === true || value === 1 || value === "1" || String(value).toLowerCase() === "true" || String(value).toLowerCase() === "yes") return true;
+  if (value === false || value === 0 || value === "0" || String(value).toLowerCase() === "false" || String(value).toLowerCase() === "no") return false;
+  throw new Error(`${label}: invalid enabled '${value}'`);
+}
+
+function uniqueApproachArms(candidates, controlPoint) {
+  const sorted = candidates.map((candidate) => ({ ...candidate, armHeading: normalizeDegrees(headingBetween(controlPoint, candidate.center)), controlDistance: metersBetween(controlPoint, candidate.center) }))
+    .sort((a, b) => a.armHeading - b.armHeading || a.controlDistance - b.controlDistance);
+  const arms = [];
+  for (const candidate of sorted) if (!arms.some((arm) => angularDistance(arm.armHeading, candidate.armHeading) <= 25)) arms.push(candidate);
   return arms;
 }
 
 function matchOsmArms(candidates, controlPoint, osmArms) {
-  const withHeadings = candidates.map((candidate) => ({
-    ...candidate,
-    armHeading: normalizeDegrees(headingBetween(controlPoint, candidate.center)),
-  }));
-  if (!Array.isArray(osmArms) || !osmArms.length) return uniqueApproachArms(withHeadings, controlPoint);
-  const remaining = withHeadings.slice();
-  const matched = [];
-  for (const osmArm of osmArms) {
-    let bestIndex = -1;
-    let bestDistance = Infinity;
-    for (let index = 0; index < remaining.length; index += 1) {
-      const distance = angularDistance(remaining[index].armHeading, osmArm.headingDegrees);
-      if (distance < bestDistance) { bestDistance = distance; bestIndex = index; }
-    }
-    if (bestIndex >= 0 && bestDistance <= 45) {
-      matched.push(remaining.splice(bestIndex, 1)[0]);
-    } else {
-      matched.push(fallbackCandidate(controlPoint, osmArm));
-    }
-  }
-  return matched;
+  const remaining = candidates.map((candidate) => ({ ...candidate, armHeading: normalizeDegrees(headingBetween(controlPoint, candidate.center)) }));
+  if (!osmArms.length) return uniqueApproachArms(remaining, controlPoint);
+  return osmArms.map((osmArm) => {
+    let bestIndex = -1; let bestDistance = Infinity;
+    remaining.forEach((item, index) => { const distance = angularDistance(item.armHeading, osmArm.headingDegrees); if (distance < bestDistance) { bestDistance = distance; bestIndex = index; } });
+    const candidate = bestIndex >= 0 && bestDistance <= 45 ? remaining.splice(bestIndex, 1)[0] : fallbackCandidate(controlPoint, osmArm);
+    return { ...candidate, osmArm };
+  });
 }
 
 function fallbackCandidate(controlPoint, osmArm) {
-  const outward = headingVector(osmArm.headingDegrees);
-  const axis = [-outward[0], -outward[1]];
-  const stopDistance = 8.0;
-  const stop = moveMeters(controlPoint, outward, stopDistance);
-  const farSide = moveMeters(controlPoint, axis, 3.2);
-  return {
-    center: stop,
-    axis,
-    point: moveMeters(farSide, [axis[1], -axis[0]], CURB_OFFSET_METERS),
-    headingDegrees: normalizeDegrees(Math.atan2(axis[0], axis[1]) * 180 / Math.PI),
-    fallback: true,
-  };
+  const outward = headingVector(osmArm.headingDegrees); const axis = [-outward[0], -outward[1]];
+  const center = moveMeters(controlPoint, outward, 8); const farSide = moveMeters(controlPoint, axis, 3.2);
+  return { center, axis, point: moveMeters(farSide, [axis[1], -axis[0]], CURB_OFFSET_METERS), armHeading: normalizeDegrees(osmArm.headingDegrees), headingDegrees: normalizeDegrees(Math.atan2(axis[0], axis[1]) * 180 / Math.PI), fallback: true };
 }
 
 function phaseGroups(arms) {
-  const groups = Array(arms.length).fill(1);
-  if (arms.length < 2) return groups;
-  let main = [0, 1];
-  let bestOpposition = -1;
-  for (let left = 0; left < arms.length; left += 1) {
-    for (let right = left + 1; right < arms.length; right += 1) {
-      const opposition = angularDistance(arms[left].armHeading, arms[right].armHeading);
-      if (opposition > bestOpposition) {
-        bestOpposition = opposition;
-        main = [left, right];
-      }
-    }
-  }
-  groups[main[0]] = 0;
-  groups[main[1]] = 0;
-  return groups;
+  const groups = Array(arms.length).fill(1); if (arms.length < 2) return groups;
+  let main = [0, 1]; let best = -1;
+  for (let a = 0; a < arms.length; a += 1) for (let b = a + 1; b < arms.length; b += 1) { const opposition = angularDistance(arms[a].armHeading, arms[b].armHeading); if (opposition > best) { best = opposition; main = [a, b]; } }
+  groups[main[0]] = 0; groups[main[1]] = 0; return groups;
 }
 
-function buildSignalPose(pole, axis, mastReach) {
-  const lateral = [axis[1], -axis[0]];
-  const face = [-axis[0], -axis[1]];
-  const head = moveMeters(pole, lateral, -mastReach);
-  const faceHeadingDegrees = Math.atan2(face[0], face[1]) * 180 / Math.PI;
-  const position = (point, height) => ({ longitude: point[0], latitude: point[1], height });
+function buildSignalPose(pole, axis, mastReach, zOffset = 0) {
+  const lateral = [axis[1], -axis[0]]; const face = [-axis[0], -axis[1]];
+  const head = moveMeters(pole, lateral, -mastReach); const faceHeadingDegrees = Math.atan2(face[0], face[1]) * 180 / Math.PI;
+  const position = (point, height) => ({ longitude: point[0], latitude: point[1], height: height + zOffset });
   const lensPoint = moveMeters(head, face, SIGNAL_LAYOUT.lensFaceOffsetMeters);
-  const board = moveMeters(
-    moveMeters(head, lateral, SIGNAL_LAYOUT.countdownLateralMeters),
-    face, SIGNAL_LAYOUT.countdownFaceOffsetMeters,
-  );
-  return {
-    pole: position(pole, 0),
-    arm: {
-      from: position(pole, SIGNAL_LAYOUT.mastHeightMeters),
-      to: position(head, SIGNAL_LAYOUT.mastHeightMeters),
-    },
-    head: { ...position(head, SIGNAL_LAYOUT.headCenterHeightMeters), faceHeadingDegrees },
-    lenses: ["red", "yellow", "green"].map((state, index) => ({
-      state,
-      ...position(lensPoint, SIGNAL_LAYOUT.headCenterHeightMeters + SIGNAL_LAYOUT.lensVerticalOffsetsMeters[index]),
-    })),
-    countdown: { ...position(board, SIGNAL_LAYOUT.mastHeightMeters), faceHeadingDegrees },
-  };
+  const board = moveMeters(moveMeters(head, lateral, SIGNAL_LAYOUT.countdownLateralMeters), face, SIGNAL_LAYOUT.countdownFaceOffsetMeters);
+  return { pole: position(pole, 0), arm: { from: position(pole, SIGNAL_LAYOUT.mastHeightMeters), to: position(head, SIGNAL_LAYOUT.mastHeightMeters) }, head: { ...position(head, SIGNAL_LAYOUT.headCenterHeightMeters), faceHeadingDegrees }, lenses: ["red", "yellow", "green"].map((state, index) => ({ state, ...position(lensPoint, SIGNAL_LAYOUT.headCenterHeightMeters + SIGNAL_LAYOUT.lensVerticalOffsetsMeters[index]) })), countdown: { ...position(board, SIGNAL_LAYOUT.mastHeightMeters), faceHeadingDegrees } };
 }
 
-function readTrafficSignals(stopLinePath, intersectionPath, osmPath) {
-  const controls = osmPath ? parseOsm(fs.readFileSync(osmPath, "utf8")).trafficSignalControls : [];
-  return buildTrafficSignals(JSON.parse(fs.readFileSync(stopLinePath, "utf8")), JSON.parse(fs.readFileSync(intersectionPath, "utf8")), controls);
-}
+function polygonCenter(geometry) { const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null; if (!ring || ring.length < 4) return null; const points = ring.slice(0, -1); return [points.reduce((s, p) => s + p[0], 0) / points.length, points.reduce((s, p) => s + p[1], 0) / points.length]; }
+function polygonRadius(geometry, center) { const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null; return ring && center ? Math.max(...ring.slice(0, -1).map((point) => metersBetween(center, point)), 0) : 0; }
+function roadAxis(geometry, center, target) { const ring = geometry?.coordinates?.[0]; if (!ring || ring.length < 3) return null; let longest; for (let i = 0; i < ring.length - 1; i += 1) { const dx = (ring[i + 1][0] - ring[i][0]) * Math.cos(center[1] * Math.PI / 180); const dy = ring[i + 1][1] - ring[i][1]; const length = Math.hypot(dx, dy); if (!longest || length > longest.length) longest = { dx, dy, length }; } if (!longest?.length) return null; let axis = [-longest.dy / longest.length, longest.dx / longest.length]; const toward = [(target[0] - center[0]) * Math.cos(center[1] * Math.PI / 180), target[1] - center[1]]; if (axis[0] * toward[0] + axis[1] * toward[1] < 0) axis = [-axis[0], -axis[1]]; return axis; }
+function nearestCenter(point, centers) { return centers.map((entry) => ({ ...entry, distance: metersBetween(point, entry.point) })).sort((a, b) => a.distance - b.distance)[0] || null; }
+function metersBetween(a, b) { const lat = (a[1] + b[1]) / 2 * Math.PI / 180; return Math.hypot((a[0] - b[0]) * Math.cos(lat), a[1] - b[1]) * Math.PI / 180 * EARTH_RADIUS; }
+function moveMeters(point, vector, meters) { const scale = 180 / Math.PI / EARTH_RADIUS; return [point[0] + vector[0] * meters * scale / Math.cos(point[1] * Math.PI / 180), point[1] + vector[1] * meters * scale]; }
+function headingBetween(from, to) { const latitude = (from[1] + to[1]) / 2 * Math.PI / 180; return Math.atan2((to[0] - from[0]) * Math.cos(latitude), to[1] - from[1]) * 180 / Math.PI; }
+function headingVector(degrees) { const radians = degrees * Math.PI / 180; return [Math.sin(radians), Math.cos(radians)]; }
+function normalizeDegrees(value) { return ((value % 360) + 360) % 360; }
+function angularDistance(a, b) { return Math.abs(((a - b + 540) % 360) - 180); }
 
-function polygonCenter(geometry) {
-  const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null;
-  if (!ring || ring.length < 4) return null;
-  const points = ring.slice(0, -1);
-  return [points.reduce((sum, point) => sum + point[0], 0) / points.length, points.reduce((sum, point) => sum + point[1], 0) / points.length];
-}
-
-function polygonRadius(geometry, center) {
-  const ring = geometry?.type === "Polygon" ? geometry.coordinates?.[0] : null;
-  if (!ring || !center) return 0;
-  return Math.max(...ring.slice(0, -1).map((point) => metersBetween(center, point)), 0);
-}
-
-function roadAxis(geometry, center, target) {
-  const ring = geometry?.coordinates?.[0];
-  if (!ring || ring.length < 3) return null;
-  let longest = null;
-  for (let i = 0; i < ring.length - 1; i += 1) {
-    const dx = (ring[i + 1][0] - ring[i][0]) * Math.cos(center[1] * Math.PI / 180);
-    const dy = ring[i + 1][1] - ring[i][1];
-    const length = Math.hypot(dx, dy);
-    if (!longest || length > longest.length) longest = { dx, dy, length };
-  }
-  if (!longest?.length) return null;
-  let axis = [-longest.dy / longest.length, longest.dx / longest.length];
-  const toward = [(target[0] - center[0]) * Math.cos(center[1] * Math.PI / 180), target[1] - center[1]];
-  if (axis[0] * toward[0] + axis[1] * toward[1] < 0) axis = [-axis[0], -axis[1]];
-  return axis;
-}
-
-function nearestCenter(point, centers) {
-  return centers.map((entry) => ({ ...entry, distance: metersBetween(point, entry.point) })).sort((a, b) => a.distance - b.distance)[0] || null;
-}
-
-function metersBetween(a, b) {
-  const lat = (a[1] + b[1]) / 2 * Math.PI / 180;
-  return Math.hypot((a[0] - b[0]) * Math.cos(lat), a[1] - b[1]) * Math.PI / 180 * EARTH_RADIUS;
-}
-
-function moveMeters(point, vector, meters) {
-  const scale = 180 / Math.PI / EARTH_RADIUS;
-  return [point[0] + vector[0] * meters * scale / Math.cos(point[1] * Math.PI / 180), point[1] + vector[1] * meters * scale];
-}
-
-function headingBetween(from, to) {
-  const latitude = (from[1] + to[1]) / 2 * Math.PI / 180;
-  return Math.atan2((to[0] - from[0]) * Math.cos(latitude), to[1] - from[1]) * 180 / Math.PI;
-}
-
-function headingVector(headingDegrees) {
-  const radians = headingDegrees * Math.PI / 180;
-  return [Math.sin(radians), Math.cos(radians)];
-}
-
-function normalizeDegrees(value) {
-  return ((value % 360) + 360) % 360;
-}
-
-function angularDistance(a, b) {
-  return Math.abs(((a - b + 540) % 360) - 180);
-}
-
-module.exports = { SIGNAL_LAYOUT, buildTrafficSignals, readTrafficSignals };
+module.exports = {
+  SIGNAL_LAYOUT,
+  signalNodeKey,
+  buildTrafficSignalFeatures,
+  validateTrafficSignalFeatures,
+  validateTrafficSignalSourceReferences,
+  buildTrafficSignalsFromFeatures,
+  buildTrafficSignals,
+  readTrafficSignalFeatures,
+  readTrafficSignals,
+};
diff --git a/scripts/reimport-gpkg.js b/scripts/reimport-gpkg.js
index 85c39ab..f0a25b8 100755
--- a/scripts/reimport-gpkg.js
+++ b/scripts/reimport-gpkg.js
@@ -17,8 +17,13 @@ const path = require("path");
 const os = require("os");
 const { execFileSync } = require("child_process");
 const { qgisPaths } = require("./lib/tool-paths");
+const { parseOsm } = require("./lib/osm");
+const {
+  validateTrafficSignalSourceReferences,
+} = require("./lib/traffic-signals");
 const {
   SCENE_LAYERS,
+  AUXILIARY_EDIT_LAYERS,
   SCENE_FILE,
   SCENE_STYLE_FILE,
   layerFile,
@@ -34,6 +39,10 @@ const ogr2ogr = qgis.ogr2ogr;
 const ogrinfo = qgis.ogrinfo;
 const outDir = path.resolve(requireText(config.outDir, "outDir"));
 const gpkgPath = path.resolve(requireText(config.gpkg, "gpkg"));
+const inputPath = path.resolve(requireText(config.input, "input"));
+const trafficSignalAssembliesPath = path.resolve(
+  config.trafficSignalAssemblies || path.join(outDir, "traffic_signal_assemblies.geojson"),
+);
 
 for (const exe of [ogr2ogr, ogrinfo]) {
   if (!fs.existsSync(exe)) {
@@ -43,6 +52,9 @@ for (const exe of [ogr2ogr, ogrinfo]) {
 if (!fs.existsSync(gpkgPath)) {
   throw new Error(`GeoPackage not found: ${gpkgPath}\nRun the intermediates stage first.`);
 }
+if (!fs.existsSync(inputPath)) {
+  throw new Error(`Input OSM XML not found: ${inputPath}`);
+}
 if (!fs.existsSync(outDir)) {
   throw new Error(`GeoJSON output directory not found: ${outDir}`);
 }
@@ -51,6 +63,7 @@ console.log(`Reimport: ${gpkgPath}`);
 console.log(`Target:   ${outDir}`);
 
 const present = gpkgLayers();
+const trafficSignalControls = parseOsm(fs.readFileSync(inputPath, "utf8")).trafficSignalControls;
 const missing = SCENE_LAYERS.filter((layer) => !present.has(layer.id)).map((layer) => layer.id);
 if (missing.length) {
   throw new Error(
@@ -68,11 +81,25 @@ try {
     console.log(`${layer.id}\tfeatures=${collection.features.length}`);
     return { layer, stagedPath, collection };
   });
+  const auxiliary = AUXILIARY_EDIT_LAYERS.map((layer) => {
+    if (!present.has(layer.id)) throw new Error(`GeoPackage is missing auxiliary layer '${layer.id}'`);
+    const stagedPath = path.join(stagingDir, layer.file);
+    exportLayer(layer.id, stagedPath);
+    const collection = readCollection(stagedPath, layer.id);
+    const validated = validateTrafficSignalSourceReferences(collection, trafficSignalControls);
+    console.log(`${layer.id}\tfeatures=${validated.features.length}`);
+    return { layer, stagedPath, collection: validated };
+  });
 
   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)));
   }
+  for (const item of auxiliary) {
+    const destination = item.layer.id === "traffic_signal_assemblies"
+      ? trafficSignalAssembliesPath : path.join(outDir, item.layer.file);
+    fs.copyFileSync(item.stagedPath, destination);
+  }
 
   const byId = new Map(staged.map((item) => [item.layer.id, item.collection]));
   const scene = mergeScene((layer) => byId.get(layer.id));
@@ -117,7 +144,7 @@ function loadConfig(cliArgs) {
     }
     Object.assign(base, JSON.parse(fs.readFileSync(file, "utf8")));
   }
-  for (const key of ["qgisApp", "outDir", "gpkg"]) {
+  for (const key of ["qgisApp", "input", "outDir", "gpkg", "trafficSignalAssemblies"]) {
     if (cliArgs[key] !== undefined) base[key] = cliArgs[key];
   }
   return base;
diff --git a/scripts/test-asset-budgets.js b/scripts/test-asset-budgets.js
index a7f62e8..22bd9e8 100644
--- a/scripts/test-asset-budgets.js
+++ b/scripts/test-asset-budgets.js
@@ -40,6 +40,10 @@ assert.equal(
   normalizeAreaConfig(base).outputs.trafficSignals,
   path.join(tempDir, "test-area", "osm2streets_web_out", "traffic_signals.json"),
 );
+assert.equal(
+  normalizeAreaConfig(base).outputs.trafficSignalAssemblies,
+  path.join(tempDir, "test-area", "osm2streets_web_out", "traffic_signal_assemblies.geojson"),
+);
 assert.equal(normalizeAreaConfig({ ...base, budget: { nodes: 800 } }).budget.glbNodes, 800);
 assert.throws(
   () => normalizeAreaConfig({ ...base, budget: { nodes: 1200 } }),
diff --git a/scripts/test-preview-assets.js b/scripts/test-preview-assets.js
index 90da8f2..f99a321 100644
--- a/scripts/test-preview-assets.js
+++ b/scripts/test-preview-assets.js
@@ -135,7 +135,7 @@ assert.doesNotMatch(previewRuntime, /cylinder: \{ length: 6\.7/);
 assert.doesNotMatch(previewRuntime, /Traffic Signal Housing/);
 assert.match(previewRuntime, /asset\.category === "dynamic"/);
 assert.match(previewRuntime, /TrafficSignalDynamic_/);
-assert.match(previewRuntime, /countdown_\$\{String\(value\)\.padStart\(2, "0"\)\}/);
+assert.match(previewRuntime, /TrafficSignalDynamic_\$\{nodeKey\}_countdown_\$\{String\(value\)\.padStart\(2, "0"\)\}/);
 assert.match(previewRuntime, /ColorBlendMode\.REPLACE/);
 assert.match(previewRuntime, /asset\.category === "countdown"/);
 assert.doesNotMatch(previewRuntime, /createCountdownDigits/);
diff --git a/scripts/test-traffic-signals.js b/scripts/test-traffic-signals.js
new file mode 100644
index 0000000..bc95a06
--- /dev/null
+++ b/scripts/test-traffic-signals.js
@@ -0,0 +1,113 @@
+#!/usr/bin/env node
+
+"use strict";
+
+const assert = require("assert");
+const {
+  buildTrafficSignalFeatures,
+  buildTrafficSignalsFromFeatures,
+  validateTrafficSignalFeatures,
+  validateTrafficSignalSourceReferences,
+} = require("./lib/traffic-signals");
+
+function rectangle(lon, lat, dx = 0.00003, dy = 0.000006) {
+  return { type: "Feature", geometry: { type: "Polygon", coordinates: [[
+    [lon - dx, lat - dy], [lon + dx, lat - dy], [lon + dx, lat + dy],
+    [lon - dx, lat + dy], [lon - dx, lat - dy],
+  ]] }, properties: {} };
+}
+
+const intersections = { type: "FeatureCollection", features: [rectangle(120.0001, 30.00005, 0.0003, 0.00025)] };
+const stops = { type: "FeatureCollection", features: [
+  rectangle(119.99995, 30.00005), rectangle(120.00010, 30.00025),
+  rectangle(120.00035, 30.00005), rectangle(120.00010, 29.99985),
+] };
+const arms = [
+  { headingDegrees: 270, wayId: "west", neighborNodeId: "w1" },
+  { headingDegrees: 0, wayId: "north", neighborNodeId: "n1" },
+  { headingDegrees: 90, wayId: "east", neighborNodeId: "e1" },
+  { headingDegrees: 180, wayId: "south", neighborNodeId: "s1" },
+];
+const control = { id: "control-1", longitude: 120.0001, latitude: 30.00005, arms };
+
+const cross = buildTrafficSignalFeatures(stops, intersections, [control]);
+assert.equal(cross.features.length, 4);
+assert.equal(new Set(cross.features.map((feature) => feature.properties.signal_uid)).size, 4);
+const t = buildTrafficSignalFeatures(stops, intersections, [{ ...control, arms: arms.slice(0, 3) }]);
+assert.equal(t.features.length, 3);
+assert.deepEqual(
+  buildTrafficSignalFeatures(stops, intersections, [control]).features.map((feature) => feature.properties.signal_uid),
+  cross.features.map((feature) => feature.properties.signal_uid),
+  "technical ids are deterministic",
+);
+
+const edited = structuredClone(cross);
+const first = edited.features[0];
+const originalStop = [first.properties.stop_lon, first.properties.stop_lat];
+first.geometry.coordinates[0] += 0.0001;
+first.properties.display_id = "A-01";
+first.properties.heading_deg = 42;
+first.properties.z_offset_m = 1.25;
+const runtime = buildTrafficSignalsFromFeatures(edited);
+assert.equal(new Set(runtime.signals.map((signal) => signal.nodeKey)).size, runtime.signals.length);
+for (const signal of runtime.signals) {
+  assert.match(signal.nodeKey, /^ts_[0-9a-f]{16}$/);
+  assert.ok(
+    `TrafficSignalDynamic_${signal.nodeKey}_countdown_19`.length <= 63,
+    "dynamic node names must stay below Blender's name limit",
+  );
+}
+const changed = runtime.signals.find((signal) => signal.id === first.properties.signal_uid);
+assert.equal(changed.displayId, "A-01");
+assert.equal(changed.longitude, first.geometry.coordinates[0]);
+assert.equal(changed.headingDegrees, 42);
+assert.deepEqual([changed.stopLongitude, changed.stopLatitude], originalStop, "moving a pole preserves the stop point");
+assert.equal(changed.pose.pole.height, 1.25);
+assert.equal(changed.pose.arm.from.height, 7.5);
+
+edited.features[1].properties.enabled = "0";
+assert.equal(buildTrafficSignalsFromFeatures(edited).signals.length, 3, "disabled assemblies are omitted");
+
+const duplicateUid = structuredClone(cross);
+duplicateUid.features[1].properties.signal_uid = duplicateUid.features[0].properties.signal_uid;
+assert.throws(() => validateTrafficSignalFeatures(duplicateUid), /Duplicate signal_uid/);
+const duplicateDisplay = structuredClone(cross);
+duplicateDisplay.features[1].properties.display_id = duplicateDisplay.features[0].properties.display_id;
+assert.throws(() => validateTrafficSignalFeatures(duplicateDisplay), /Duplicate display_id/);
+const invalid = structuredClone(cross);
+invalid.features[0].properties.mast_reach_m = -1;
+assert.throws(() => validateTrafficSignalFeatures(invalid), /invalid mast_reach_m/);
+const invalidGeometry = structuredClone(cross);
+invalidGeometry.features[0].geometry = { type: "LineString", coordinates: [[120, 30], [121, 31]] };
+assert.throws(() => validateTrafficSignalFeatures(invalidGeometry), /geometry must be a finite Point/);
+const mismatchedIdentity = structuredClone(cross);
+mismatchedIdentity.features[0].properties.approach_id = "other-way:w1";
+assert.throws(() => validateTrafficSignalFeatures(mismatchedIdentity), /approach_id does not match source_way_id/);
+const invalidEnabled = structuredClone(cross);
+invalidEnabled.features[0].properties.enabled = "maybe";
+assert.throws(() => validateTrafficSignalFeatures(invalidEnabled), /invalid enabled/);
+assert.doesNotThrow(() => validateTrafficSignalSourceReferences(cross, [control]));
+assert.throws(
+  () => validateTrafficSignalSourceReferences(cross, [{ ...control, arms: arms.slice(1) }]),
+  /approach_id .* is not present on OSM control/,
+);
+assert.throws(
+  () => validateTrafficSignalSourceReferences(cross, []),
+  /control_id .* is not present in the current OSM/,
+);
+for (const disabledValue of [false, 0, "0", "false", "no"]) {
+  const disabled = structuredClone(cross);
+  disabled.features[0].properties.enabled = disabledValue;
+  assert.equal(buildTrafficSignalsFromFeatures(disabled).signals.length, 3);
+}
+for (const key of ["heading_deg", "phase_group", "stop_lon", "stop_lat", "z_offset_m"]) {
+  const missingNumber = structuredClone(cross);
+  missingNumber.features[0].properties[key] = null;
+  assert.throws(
+    () => validateTrafficSignalFeatures(missingNumber),
+    new RegExp(`missing ${key}`),
+    `${key} must not silently coerce null to zero`,
+  );
+}
+
+console.log("Traffic signal tests passed.");