feat: add manual lasso wall splitting with magnetic edge-snapping and active contour refinement

- New magneticLasso module: Sobel energy map + Dijkstra shortest-path + Douglas-Peucker - New activeContour module: greedy snake + balloon force for polygon-to-edge refinement - wallTextureSplit: edge barrier mask, morphological mask hole closing, Moore boundary tracing, simplified polygon contours, manual pick map patching, gap absorption - MaskSegmentCanvas: full lasso gesture pipeline (tap vertices, drag, magnetic paths, close polygon, endLasso/cancelLasso/deleteLasso) - New maskConfig options: splitWallsEdgeBarrierThreshold, splitWallsCloseMaskRadius, manualSplitWalls, manualSplitWallsMaxCount, manualSplitWallsGapAbsorbDilatePx, magneticLasso, activeContourRefine - New ref methods: startLasso, endLasso, cancelLasso, getManualRegions, deleteLasso - New exported types: LassoPolygon, ManualWallPartition - RegionMaskData carries indexToName and wallSemanticIdx through downsample - Simplify README to point to documentation site - Update documentation site (EN + ZH-CN) with all new APIs and interaction guide - Example app: lasso mode toggles and operation buttons Co-authored-by: Cursor <cursoragent@cursor.com>
2026-07-06 20:23:57 -07:00 · 2026-07-06 20:23:57 -07:00 · 3a3f07628d
commit 3a3f07628d
parent 26d3717169
41 changed files with 4014 additions and 1002 deletions
--- a/README.md
+++ b/README.md
--- a/tests/wallTextureSplit.test.ts
+++ b/tests/wallTextureSplit.test.ts
@ -8,7 +8,14 @@ import {
  setMaskSegmentRuntimeConfig,
 } from '../src/utils/maskSegmentRuntime';
 import type { SegmentMaskResult } from '../src/utils/maskSegmentation';
-import { splitWallRegionsByTexture } from '../src/utils/wallTextureSplit';
+import {
+  buildPickMapAfterWallSplit,
+  dilatePickBuffer1px,
+  patchPickMapForManualWallSplit,
+  splitWallRegionsByTexture,
+  absorbSmallWallGapsForLassoPolygons,
+  WALL_SUB_LABEL_NONE,
+} from '../src/utils/wallTextureSplit';

 const WALL_IDX = 3;
 const IGNORE = 255;
@ -180,6 +187,196 @@ test('same-color wall with lighting gradient stays one region', () => {
  expect(wallSubs[0].name).toBe('wall-1');
 });

+test('manual wall split pick map keeps ceiling and wall sub-regions paintable', () => {
+  const cols = 20;
+  const rows = 10;
+  const CEILING_IDX = 1;
+  const WALL_IDX = 3;
+  const pixelCount = cols * rows;
+  const labels = new Uint8Array(pixelCount);
+  labels.fill(CEILING_IDX);
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      labels[y * cols + x] = WALL_IDX;
+    }
+  }
+  const baseboardBinary = new Uint8Array(pixelCount);
+  const wallSubLabels = new Uint8Array(pixelCount);
+  wallSubLabels.fill(WALL_SUB_LABEL_NONE);
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols / 2; x++) {
+      wallSubLabels[y * cols + x] = 0;
+    }
+    for (let x = cols / 2; x < cols; x++) {
+      wallSubLabels[y * cols + x] = 1;
+    }
+  }
+
+  const indexToName = [
+    'door',
+    'ceiling',
+    'cabinet',
+    'wall',
+    'baseboard',
+    'windowFrame',
+    'garageDoor',
+    'roof',
+    'eave',
+  ];
+  const mergedRegions = [
+    { id: 0, name: 'ceiling', area: 100 },
+    { id: 1, name: 'wall-1', area: 50 },
+    { id: 2, name: 'wall-2', area: 50 },
+  ];
+  const nameToId = new Map(mergedRegions.map(r => [r.name, r.id]));
+  const pickRaw = buildPickMapAfterWallSplit(
+    labels,
+    baseboardBinary,
+    WALL_IDX,
+    wallSubLabels,
+    indexToName,
+    nameToId,
+    cols,
+    rows,
+  );
+  const pick = dilatePickBuffer1px(pickRaw, cols, rows);
+
+  expect(pickRegionIdAt(pick, cols, 10, 2)).toBe(0);
+  expect(pickRegionIdAt(pick, cols, 3, 7)).toBe(1);
+  expect(pickRegionIdAt(pick, cols, 15, 7)).toBe(2);
+});
+
+test('manual wall split keeps non-wall region IDs stable', () => {
+  const cols = 20;
+  const rows = 10;
+  const CEILING_IDX = 1;
+  const WALL_IDX = 3;
+  const WINDOW_IDX = 5;
+  const pixelCount = cols * rows;
+  const labels = new Uint8Array(pixelCount);
+  labels.fill(CEILING_IDX);
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      labels[y * cols + x] = WALL_IDX;
+    }
+  }
+  labels[2 * cols + 18] = WINDOW_IDX;
+
+  const nonWallRegions = [
+    { id: 0, name: 'ceiling', area: 100 },
+    { id: 2, name: 'windowFrame', area: 20 },
+  ];
+  const maxNonWallId = Math.max(...nonWallRegions.map(r => r.id));
+  const wallSubRegions = [
+    { id: maxNonWallId + 1, name: 'wall-1', area: 50 },
+    { id: maxNonWallId + 2, name: 'wall-2', area: 40 },
+  ];
+  const mergedRegions = [...nonWallRegions, ...wallSubRegions];
+
+  expect(mergedRegions.find(r => r.name === 'ceiling')?.id).toBe(0);
+  expect(mergedRegions.find(r => r.name === 'windowFrame')?.id).toBe(2);
+  expect(mergedRegions.find(r => r.name === 'wall-1')?.id).toBe(3);
+  expect(mergedRegions.find(r => r.name === 'wall-2')?.id).toBe(4);
+
+  const indexToName = [
+    'door',
+    'ceiling',
+    'cabinet',
+    'wall',
+    'baseboard',
+    'windowFrame',
+    'garageDoor',
+    'roof',
+    'eave',
+  ];
+  const baseboardBinary = new Uint8Array(pixelCount);
+  const wallSubLabels = new Uint8Array(pixelCount);
+  wallSubLabels.fill(WALL_SUB_LABEL_NONE);
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols / 2; x++) {
+      wallSubLabels[y * cols + x] = 0;
+    }
+    for (let x = cols / 2; x < cols; x++) {
+      wallSubLabels[y * cols + x] = 1;
+    }
+  }
+  const nameToId = new Map(mergedRegions.map(r => [r.name, r.id]));
+  const pickRaw = buildPickMapAfterWallSplit(
+    labels,
+    baseboardBinary,
+    WALL_IDX,
+    wallSubLabels,
+    indexToName,
+    nameToId,
+    cols,
+    rows,
+  );
+  const pick = dilatePickBuffer1px(pickRaw, cols, rows);
+  expect(pickRegionIdAt(pick, cols, 10, 2)).toBe(0);
+  expect(pickRegionIdAt(pick, cols, 18, 2)).toBe(2);
+});
+
+test('patchPickMapForManualWallSplit preserves non-wall pick codes', () => {
+  const cols = 20;
+  const rows = 10;
+  const CEILING_IDX = 1;
+  const WALL_IDX = 3;
+  const pixelCount = cols * rows;
+  const labels = new Uint8Array(pixelCount);
+  labels.fill(CEILING_IDX);
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      labels[y * cols + x] = WALL_IDX;
+    }
+  }
+
+  const existingPick = new Uint8Array(pixelCount);
+  existingPick.fill(0);
+  for (let y = 0; y < 5; y++) {
+    for (let x = 0; x < cols; x++) {
+      existingPick[y * cols + x] = 1; // ceiling id 0
+    }
+  }
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      existingPick[y * cols + x] = 2; // old wall id 1
+    }
+  }
+
+  const wallSubLabels = new Uint8Array(pixelCount);
+  wallSubLabels.fill(WALL_SUB_LABEL_NONE);
+  for (let y = 5; y < rows; y++) {
+    for (let x = 0; x < cols / 2; x++) {
+      wallSubLabels[y * cols + x] = 0;
+    }
+    for (let x = cols / 2; x < cols; x++) {
+      wallSubLabels[y * cols + x] = 1;
+    }
+  }
+
+  const baseboardBinary = new Uint8Array(pixelCount);
+  const nameToId = new Map([
+    ['ceiling', 0],
+    ['wall-1', 3],
+    ['wall-2', 4],
+  ]);
+
+  const patched = patchPickMapForManualWallSplit(
+    existingPick,
+    labels,
+    baseboardBinary,
+    WALL_IDX,
+    wallSubLabels,
+    nameToId,
+    cols,
+    rows,
+  );
+
+  expect(pickRegionIdAt(patched, cols, 10, 2)).toBe(0);
+  expect(pickRegionIdAt(patched, cols, 3, 7)).toBe(3);
+  expect(pickRegionIdAt(patched, cols, 15, 7)).toBe(4);
+});
+
 test('single-texture wall becomes wall-1 when splitWalls enabled', () => {
  const cols = 16;
  const rows = 8;
@ -196,3 +393,82 @@ test('single-texture wall becomes wall-1 when splitWalls enabled', () => {
  expect(wallSubs).toHaveLength(1);
  expect(wallSubs[0].name).toBe('wall-1');
 });
+
+test('absorbSmallWallGapsForLassoPolygons merges thin unassigned wall slivers', () => {
+  const cols = 20;
+  const rows = 1;
+  const pixelCount = cols * rows;
+  const labels = new Uint8Array(pixelCount);
+  labels.fill(WALL_IDX);
+  const baseboardBinary = new Uint8Array(pixelCount);
+  const priorAssigned = new Uint8Array(pixelCount);
+  priorAssigned.fill(WALL_SUB_LABEL_NONE);
+
+  const polyLabels = new Uint8Array(pixelCount);
+  polyLabels.fill(WALL_SUB_LABEL_NONE);
+  for (let x = 0; x <= 14; x++) {
+    polyLabels[x] = 0;
+  }
+
+  const areas = [15];
+  const bboxes = [{ x: 0, y: 0, w: 15, h: 1 }];
+
+  absorbSmallWallGapsForLassoPolygons(
+    polyLabels,
+    1,
+    areas,
+    bboxes,
+    labels,
+    baseboardBinary,
+    WALL_IDX,
+    priorAssigned,
+    cols,
+    rows,
+    3,
+  );
+
+  expect(polyLabels[15]).toBe(0);
+  expect(polyLabels[16]).toBe(0);
+  expect(polyLabels[17]).toBe(0);
+  expect(areas[0]).toBe(18);
+});
+
+test('absorbSmallWallGapsForLassoPolygons respects dilation radius limit', () => {
+  const cols = 20;
+  const rows = 1;
+  const pixelCount = cols * rows;
+  const labels = new Uint8Array(pixelCount);
+  labels.fill(WALL_IDX);
+  const baseboardBinary = new Uint8Array(pixelCount);
+  const priorAssigned = new Uint8Array(pixelCount);
+  priorAssigned.fill(WALL_SUB_LABEL_NONE);
+
+  const polyLabels = new Uint8Array(pixelCount);
+  polyLabels.fill(WALL_SUB_LABEL_NONE);
+  for (let x = 0; x <= 10; x++) {
+    polyLabels[x] = 0;
+  }
+
+  const areas = [11];
+  const bboxes = [{ x: 0, y: 0, w: 11, h: 1 }];
+
+  absorbSmallWallGapsForLassoPolygons(
+    polyLabels,
+    1,
+    areas,
+    bboxes,
+    labels,
+    baseboardBinary,
+    WALL_IDX,
+    priorAssigned,
+    cols,
+    rows,
+    3,
+  );
+
+  expect(polyLabels[11]).toBe(0);
+  expect(polyLabels[12]).toBe(0);
+  expect(polyLabels[13]).toBe(0);
+  expect(polyLabels[14]).toBe(WALL_SUB_LABEL_NONE);
+  expect(areas[0]).toBe(14);
+});
--- a/dist/components/MaskSegmentCanvas.js
+++ b/dist/components/MaskSegmentCanvas.js
--- a/dist/components/MaskSegmentCanvas.types.d.ts
+++ b/dist/components/MaskSegmentCanvas.types.d.ts
@ -53,6 +53,33 @@ export type MaskSegmentConfig = {
    splitWallsChromaBlurRadius?: number;
    /** wall mask only, low saturation (white/gray wall) junction radius, used to force separate colored walls */
    splitWallsNeutralChromaMax?: number;
+    /**
+     * Wall split: raw per-channel BGR Sobel gradient threshold for edge barriers
+     * (0 = disabled). Uses un-normalized 8‑bit Sobel magnitude on each B/G/R
+     * channel (max per pixel, range ≈ 0–1442). Visible wall seams ≈ 120–280,
+     * subtle lighting gradients ≈ 20–80. Default: 160.
+     */
+    splitWallsEdgeBarrierThreshold?: number;
+    /**
+     * Morphological close radius for wall mask holes before component labeling.
+     * Non-wall pixels inside the wall boundary (windows, doors, mask artefacts)
+     * are temporarily filled so the BFS can bridge across them. Default: 3.
+     * Set to 0 to disable.
+     */
+    splitWallsCloseMaskRadius?: number;
+    /** When true, disables automatic texture-based wall splitting (splitWalls). Manual lasso partitioning is used instead. */
+    manualSplitWalls?: boolean;
+    /** wall mask only, max number of manual wall sub-regions defined by lasso */
+    manualSplitWallsMaxCount?: number;
+    /**
+     * Manual lasso: morphological dilation radius (seg pixels) used to merge thin
+     * unassigned wall pockets adjacent to the drawn polygon.
+     */
+    manualSplitWallsGapAbsorbDilatePx?: number;
+    /** When true, lasso mode uses edge-snapping (Sobel gradient + Dijkstra shortest-path). Default: false. */
+    magneticLasso?: boolean;
+    /** After End Lasso, run active contour refinement on each polygon to expand vertices outward toward wall-mask edges. Default: false. */
+    activeContourRefine?: boolean;
 };
 export type PaintConfig = {
    palette?: BgrColor[];
@ -117,6 +144,32 @@ export type PaintBrushRequiredPayload = {
    regionName: string;
 };
 export type PaintCallbackPayload = PaintSuccessPayload | PaintBrushRequiredPayload;
+/** A lasso polygon defined by user tapping vertices on the wall mask area. Vertices are in normalized image coordinates (0..1). */
+export type LassoPolygon = {
+    id: string;
+    vertices: {
+        x: number;
+        y: number;
+    }[];
+    isClosed: boolean;
+};
+/** Result of converting a lasso polygon into an actual wall sub-region. */
+export type ManualWallPartition = {
+    id: string;
+    regionId: number;
+    regionName: string;
+    vertices: {
+        x: number;
+        y: number;
+    }[];
+    bbox: {
+        x: number;
+        y: number;
+        w: number;
+        h: number;
+    };
+    area: number;
+};
 export type MaskSegmentCanvasRef = {
    reset: () => void;
    swap: (showOrigin?: boolean) => void;
@ -133,6 +186,20 @@ export type MaskSegmentCanvasRef = {
    getPaintedRegions: () => PaintedRegionRecord[];
    /** Returns the most recent auto-export or save() result, if any. */
    getLastExport?: () => SavePaintResult | null;
+    /** Enter lasso mode — user can tap wall mask area to place polygon vertices. */
+    startLasso: () => void;
+    /** Exit lasso mode, convert all closed lasso polygons into wall-X sub-regions for painting. Returns the partition results. */
+    endLasso: () => ManualWallPartition[];
+    /**
+     * Exit the current lasso editing session without saving regions.
+     * Discards in-progress vertices and closed polygons from this session only;
+     * previously committed manual wall partitions are kept.
+     */
+    cancelLasso: () => void;
+    /** Get the current manual wall partitions (only valid after endLasso has been called). */
+    getManualRegions: () => ManualWallPartition[];
+    /** Delete a lasso polygon by its id. Committed partitions also drop paint on that region. */
+    deleteLasso: (id: string) => void;
 };
 export type MaskSegmentCanvasProps = {
    originUrl?: string;
--- a/dist/components/MaskSegmentCanvas.types.js
+++ b/dist/components/MaskSegmentCanvas.types.js
@ -1 +1 @@
-"use strict";var r=Object.defineProperty;var a=Object.getOwnPropertyDescriptor;var s=Object.getOwnPropertyNames;var l=Object.prototype.hasOwnProperty;var g=(n,e,t,o)=>{if(e&&typeof e=="object"||typeof e=="function")for(let i of s(e))!l.call(n,i)&&i!==t&&r(n,i,{get:()=>e[i],enumerable:!(o=a(e,i))||o.enumerable});return n};var m=n=>g(r({},"__esModule",{value:!0}),n);var u={};module.exports=m(u);
+"use strict";var r=Object.defineProperty;var a=Object.getOwnPropertyDescriptor;var s=Object.getOwnPropertyNames;var l=Object.prototype.hasOwnProperty;var m=(n,e,t,o)=>{if(e&&typeof e=="object"||typeof e=="function")for(let i of s(e))!l.call(n,i)&&i!==t&&r(n,i,{get:()=>e[i],enumerable:!(o=a(e,i))||o.enumerable});return n};var g=n=>m(r({},"__esModule",{value:!0}),n);var u={};module.exports=g(u);
--- a/dist/index.d.ts
+++ b/dist/index.d.ts
@ -1,5 +1,5 @@
 export { default } from './components/MaskSegmentCanvas';
-export type { BgrColor, InteractionConfig, MaskSegmentCanvasProps, MaskSegmentCanvasRef, MaskSegmentConfig, MaskSegmentSession, MaskSegmentWatchDetail, MaskSegmentWatchState, MaskSemanticColor, PaintBrushRequiredPayload, PaintCallbackPayload, PaintSuccessPayload, PaintConfig, PaintedRegionRecord, PipelineConfig, PipelinePreset, SavePaintOptions, SavePaintResult, SegmentRegion, } from './components/MaskSegmentCanvas.types';
+export type { BgrColor, InteractionConfig, LassoPolygon, ManualWallPartition, MaskSegmentCanvasProps, MaskSegmentCanvasRef, MaskSegmentConfig, MaskSegmentSession, MaskSegmentWatchDetail, MaskSegmentWatchState, MaskSemanticColor, PaintBrushRequiredPayload, PaintCallbackPayload, PaintSuccessPayload, PaintConfig, PaintedRegionRecord, PipelineConfig, PipelinePreset, SavePaintOptions, SavePaintResult, SegmentRegion, } from './components/MaskSegmentCanvas.types';
 export { BASEBOARD_SEMANTIC_NAME, MASK_SEMANTIC_COLORS, } from './utils/maskSemanticPalette';
 export { createRuntimeConfig, DEFAULT_INTERACTION_CONFIG, DEFAULT_MASK_CONFIG, DEFAULT_PAINT_CONFIG, DEFAULT_PIPELINE_CONFIG, PIPELINE_HIGH, PIPELINE_LOW, PIPELINE_MEDIUM, PIPELINE_PRESETS, getMaskSegmentRuntimeConfig, resolvePipelineConfig, setMaskSegmentRuntimeConfig, } from './utils/maskSegmentRuntime';
 export { prewarmPngBgrCache, prewarmPngBgrCacheAsync, } from './utils/pngImage';
--- a/dist/index.js
+++ b/dist/index.js
@ -1 +1 @@
-"use strict";var m=Object.create;var i=Object.defineProperty;var E=Object.getOwnPropertyDescriptor;var I=Object.getOwnPropertyNames;var M=Object.getPrototypeOf,f=Object.prototype.hasOwnProperty;var p=(a,n)=>{for(var t in n)i(a,t,{get:n[t],enumerable:!0})},g=(a,n,t,P)=>{if(n&&typeof n=="object"||typeof n=="function")for(let o of I(n))!f.call(a,o)&&o!==t&&i(a,o,{get:()=>n[o],enumerable:!(P=E(n,o))||P.enumerable});return a};var _=(a,n,t)=>(t=a!=null?m(M(a)):{},g(n||!a||!a.__esModule?i(t,"default",{value:a,enumerable:!0}):t,a)),l=a=>g(i({},"__esModule",{value:!0}),a);var A={};p(A,{BASEBOARD_SEMANTIC_NAME:()=>r.BASEBOARD_SEMANTIC_NAME,DEFAULT_INTERACTION_CONFIG:()=>e.DEFAULT_INTERACTION_CONFIG,DEFAULT_MASK_CONFIG:()=>e.DEFAULT_MASK_CONFIG,DEFAULT_PAINT_CONFIG:()=>e.DEFAULT_PAINT_CONFIG,DEFAULT_PIPELINE_CONFIG:()=>e.DEFAULT_PIPELINE_CONFIG,MASK_SEMANTIC_COLORS:()=>r.MASK_SEMANTIC_COLORS,PIPELINE_HIGH:()=>e.PIPELINE_HIGH,PIPELINE_LOW:()=>e.PIPELINE_LOW,PIPELINE_MEDIUM:()=>e.PIPELINE_MEDIUM,PIPELINE_PRESETS:()=>e.PIPELINE_PRESETS,createRuntimeConfig:()=>e.createRuntimeConfig,default:()=>C.default,getMaskSegmentRuntimeConfig:()=>e.getMaskSegmentRuntimeConfig,prewarmPngBgrCache:()=>s.prewarmPngBgrCache,prewarmPngBgrCacheAsync:()=>s.prewarmPngBgrCacheAsync,resolveAssetPath:()=>S.resolveAssetPath,resolvePipelineConfig:()=>e.resolvePipelineConfig,setMaskSegmentRuntimeConfig:()=>e.setMaskSegmentRuntimeConfig});module.exports=l(A);var C=_(require("./components/MaskSegmentCanvas")),r=require("./utils/maskSemanticPalette"),e=require("./utils/maskSegmentRuntime"),s=require("./utils/pngImage"),S=require("./utils/resolveAssetPath");
+"use strict";var m=Object.create;var i=Object.defineProperty;var E=Object.getOwnPropertyDescriptor;var I=Object.getOwnPropertyNames;var l=Object.getPrototypeOf,M=Object.prototype.hasOwnProperty;var f=(a,n)=>{for(var t in n)i(a,t,{get:n[t],enumerable:!0})},g=(a,n,t,r)=>{if(n&&typeof n=="object"||typeof n=="function")for(let o of I(n))!M.call(a,o)&&o!==t&&i(a,o,{get:()=>n[o],enumerable:!(r=E(n,o))||r.enumerable});return a};var p=(a,n,t)=>(t=a!=null?m(l(a)):{},g(n||!a||!a.__esModule?i(t,"default",{value:a,enumerable:!0}):t,a)),_=a=>g(i({},"__esModule",{value:!0}),a);var A={};f(A,{BASEBOARD_SEMANTIC_NAME:()=>s.BASEBOARD_SEMANTIC_NAME,DEFAULT_INTERACTION_CONFIG:()=>e.DEFAULT_INTERACTION_CONFIG,DEFAULT_MASK_CONFIG:()=>e.DEFAULT_MASK_CONFIG,DEFAULT_PAINT_CONFIG:()=>e.DEFAULT_PAINT_CONFIG,DEFAULT_PIPELINE_CONFIG:()=>e.DEFAULT_PIPELINE_CONFIG,MASK_SEMANTIC_COLORS:()=>s.MASK_SEMANTIC_COLORS,PIPELINE_HIGH:()=>e.PIPELINE_HIGH,PIPELINE_LOW:()=>e.PIPELINE_LOW,PIPELINE_MEDIUM:()=>e.PIPELINE_MEDIUM,PIPELINE_PRESETS:()=>e.PIPELINE_PRESETS,createRuntimeConfig:()=>e.createRuntimeConfig,default:()=>C.default,getMaskSegmentRuntimeConfig:()=>e.getMaskSegmentRuntimeConfig,prewarmPngBgrCache:()=>P.prewarmPngBgrCache,prewarmPngBgrCacheAsync:()=>P.prewarmPngBgrCacheAsync,resolveAssetPath:()=>S.resolveAssetPath,resolvePipelineConfig:()=>e.resolvePipelineConfig,setMaskSegmentRuntimeConfig:()=>e.setMaskSegmentRuntimeConfig});module.exports=_(A);var C=p(require("./components/MaskSegmentCanvas")),s=require("./utils/maskSemanticPalette"),e=require("./utils/maskSegmentRuntime"),P=require("./utils/pngImage"),S=require("./utils/resolveAssetPath");
--- a/dist/utils/activeContour.d.ts
+++ b/dist/utils/activeContour.d.ts
@ -0,0 +1,46 @@
+/**
+ * Active Contour Model — greedy snake + balloon force.
+ *
+ * After the user finishes a lasso polygon, this module refines the boundary
+ * vertices outward toward the true wall-mask edge. Each vertex samples
+ * positions along its outward normal and picks the one with lowest energy.
+ *
+ * Pipeline:
+ *   1. Subdivide polygon to get evenly-spaced control points
+ *   2. For each iteration (3-5 rounds):
+ *      a. Compute outward normal at each point
+ *      b. Sample N positions along the normal (outward first, then inward)
+ *      c. Score each position: E = E_edge + E_smooth
+ *      d. Move vertex to min-energy position (constrained to wall mask)
+ *   3. Douglas-Peucker simplify
+ */
+import { type WallMaskSample } from './magneticLasso';
+export type ActiveContourOpts = {
+    /** Number of greedy iterations (default 3). */
+    iterations?: number;
+    /** Number of sample positions along normal per direction (default 6). */
+    samplesPerDirection?: number;
+    /** Step size (norm coords) between samples (default 0.003). */
+    sampleStep?: number;
+    /** Smoothness weight — higher keeps vertices more uniformly spaced (default 0.15). */
+    smoothWeight?: number;
+    /** Edge weight — higher makes contour hug mask boundary (default 1.0). */
+    edgeWeight?: number;
+    /** Balloon bias — extra outward push per iteration (default 0.002). */
+    balloonForce?: number;
+    /** Minimum vertex count for a polygon to be refined (default 4). */
+    minVertices?: number;
+};
+/**
+ * Refine a single closed lasso polygon to hug the wall-mask outer boundary.
+ *
+ * Returns a new vertex list (not mutated in place). Returns the original
+ * polygon unchanged if it has too few vertices or no wall mask is given.
+ */
+export declare function refinePolygonToWallEdges(vertices: {
+    x: number;
+    y: number;
+}[], mask: WallMaskSample, opts?: ActiveContourOpts): {
+    x: number;
+    y: number;
+}[];
--- a/dist/utils/activeContour.js
+++ b/dist/utils/activeContour.js
@ -0,0 +1 @@
+"use strict";var W=Object.defineProperty;var q=Object.getOwnPropertyDescriptor;var E=Object.getOwnPropertyNames;var V=Object.prototype.hasOwnProperty;var B=(n,e)=>{for(var m in e)W(n,m,{get:e[m],enumerable:!0})},N=(n,e,m,o)=>{if(e&&typeof e=="object"||typeof e=="function")for(let t of E(e))!V.call(n,t)&&t!==m&&W(n,t,{get:()=>e[t],enumerable:!(o=q(e,t))||o.enumerable});return n};var U=n=>N(W({},"__esModule",{value:!0}),n);var J={};B(J,{refinePolygonToWallEdges:()=>G});module.exports=U(J);var T=require("./magneticLasso");const L={iterations:3,samplesPerDirection:6,sampleStep:.003,smoothWeight:.15,edgeWeight:1,balloonForce:.002,minVertices:4};function _(n,e,m){const o=e.x-n.x,t=e.y-n.y,r=m.x-e.x,s=m.y-e.y,c=o+r,u=t+s,f=-u,h=c,l=u,x=-c,a=r*h-s*f,g=r*x-s*l,i=Math.hypot(f,h);if(i<1e-8)return{x:0,y:0};const[y,b]=a<g?[f,h]:[l,x];return{x:y/i,y:b/i}}function j(n,e,m,o){const{labels:t,baseboardBinary:r,cols:s,rows:c,wallSemanticIdx:u}=m;if(s<=0||c<=0)return o;const f=Math.round(n*s),h=Math.round(e*c),l=Math.ceil(o);let x=o+1;for(let a=-l;a<=l;a++)for(let g=-l;g<=l;g++){const i=f+g,y=h+a;if(i<0||y<0||i>=s||y>=c)continue;const b=y*s+i;if(!(t[b]!==u||r[b])&&(i===0||y===0||i===s-1||y===c-1||t[b-1]!==u||t[b+1]!==u||t[b-s]!==u||t[b+s]!==u)){const d=Math.hypot(g,a);d<x&&(x=d)}}return x/Math.max(s,c)}function O(n,e,m,o,t,r){if(!(0,T.isNormPointOnWallMask)(n,e,m))return 1e6;const s=j(n,e,m,o)/o;let c=0;if(t.length>=2){const u=t[0],f=t[t.length-1],h=(u.x+f.x)/2,l=(u.y+f.y)/2;c=Math.hypot(n-h,e-l)}return r.edgeWeight*s+r.smoothWeight*c}function z(n,e){if(n.length<2)return[...n];const m=[],o=n.length;for(let t=0;t<o;t++){const r=n[t],s=n[(t+1)%o];m.push({...r});const c=Math.hypot(s.x-r.x,s.y-r.y),u=Math.floor(c/e);if(u>1)for(let f=1;f<u;f++){const h=f/u;m.push({x:r.x+h*(s.x-r.x),y:r.y+h*(s.y-r.y)})}}return m}function G(n,e,m){const o={...L,...m};if(n.length<o.minVertices||!e)return[...n];let t=z(n,o.sampleStep*2);const r=o.samplesPerDirection*o.sampleStep*Math.max(e.cols,e.rows),s=o.samplesPerDirection*o.sampleStep*Math.max(e.cols,e.rows);for(let h=0;h<o.iterations;h++){const l=[],x=t.length;for(let a=0;a<x;a++){const g=t[(a-1+x)%x],i=t[a],y=t[(a+1)%x],b=_(g,i,y);if(b.x===0&&b.y===0){l.push({...i});continue}let d={...i},p=O(i.x,i.y,e,s,[g,y],o);const M=o.balloonForce*(h+1);for(let S=1;S<=o.samplesPerDirection;S++){const P=S*o.sampleStep,D=i.x+b.x*(P+M),w=i.y+b.y*(P+M),A=O(D,w,e,s,[l.length>0?l[l.length-1]:t[(a-1+x)%x],y],o);A<p&&(p=A,d={x:D,y:w});const I=i.x-b.x*P,C=i.y-b.y*P,F=O(I,C,e,s,[l.length>0?l[l.length-1]:t[(a-1+x)%x],y],o);F<p&&(p=F,d={x:I,y:C})}l.push(d)}t=l}const c=H(t,.002);if(c.length<3)return[...n];const u=c[0],f=c[c.length-1];return Math.hypot(u.x-f.x,u.y-f.y)>5e-4&&c.push({...u}),c}function H(n,e){if(n.length<=2)return[...n];const m=new Uint8Array(n.length);m[0]=1,m[n.length-1]=1;function o(r,s){if(s-r<=1)return;const c=n[r].x,u=n[r].y,f=n[s].x,h=n[s].y,l=f-c,x=h-u,a=l*l+x*x;let g=0,i=r;for(let y=r+1;y<s;y++){let b;if(a===0)b=Math.hypot(n[y].x-c,n[y].y-u);else{const d=Math.max(0,Math.min(1,((n[y].x-c)*l+(n[y].y-u)*x)/a)),p=c+d*l,M=u+d*x;b=Math.hypot(n[y].x-p,n[y].y-M)}b>g&&(g=b,i=y)}g>e&&(m[i]=1,o(r,i),o(i,s))}o(0,n.length-1);const t=[];for(let r=0;r<n.length;r++)if(m[r]){if(t.length>0){const s=t[t.length-1];if(Math.hypot(n[r].x-s.x,n[r].y-s.y)<.001)continue}t.push({x:n[r].x,y:n[r].y})}return t}
--- a/dist/utils/magneticLasso.d.ts
+++ b/dist/utils/magneticLasso.d.ts
@ -0,0 +1,112 @@
+/**
+ * Magnetic Lasso — edge-snapping polygon placement for manual wall splitting.
+ *
+ * Pipeline:
+ *   1. buildEnergyMap   → grayscale + downsample + Sobel gradient → energy grid
+ *   2. findShortestPath → Dijkstra 8-connected on low-energy (edge) pixels
+ *   3. extractCornerPoints → Douglas-Peucker simplification on raw path
+ *   4. upscalePath      → map energy-space coords back to original image coords
+ */
+export type EnergyMap = {
+    /** Float32Array per-pixel energy values [0…1]; low = edge, high = flat */
+    map: Float32Array;
+    w: number;
+    h: number;
+    /** Downscale ratio: energyDim / sourceDim (≈ em.w / sourceCols) */
+    scale: number;
+    /** Optional 0/1 mask at energy resolution; 0 = blocked for pathfinding */
+    traversable?: Uint8Array;
+};
+/** Seg-resolution wall mask used to constrain lasso vertices. */
+export type WallMaskSample = {
+    labels: Uint8Array;
+    baseboardBinary: Uint8Array;
+    cols: number;
+    rows: number;
+    wallSemanticIdx: number;
+};
+/** True when norm coords fall on a wall semantic pixel (excludes baseboard). */
+export declare function isNormPointOnWallMask(normX: number, normY: number, mask: WallMaskSample): boolean;
+export declare function filterVerticesToWallMask<T extends {
+    x: number;
+    y: number;
+}>(vertices: T[], mask: WallMaskSample): T[];
+/**
+ * Snap a normalized point to the nearest wall-mask boundary pixel when the
+ * touch falls within `snapRadiusSegPx` (segmentation resolution) of the edge.
+ */
+export declare function snapNormPointToWallEdge(normX: number, normY: number, mask: WallMaskSample, snapRadiusSegPx?: number): {
+    x: number;
+    y: number;
+};
+/**
+ * Prefer wall-mask corner pixels (L-shaped outer boundary), then plain edge.
+ * Used when the user taps without dragging.
+ */
+export declare function snapNormPointToWallCornerOrEdge(normX: number, normY: number, mask: WallMaskSample, snapRadiusSegPx?: number): {
+    x: number;
+    y: number;
+};
+/**
+ * During vertex drag: snap to corner/edge when near, otherwise keep interior
+ * wall points so the anchor can move freely on the wall mask.
+ */
+export declare function resolveLassoWallDragPoint(normX: number, normY: number, mask: WallMaskSample, snapRadiusSegPx?: number): {
+    x: number;
+    y: number;
+} | null;
+export declare function buildWallAllowedMask(labels: Uint8Array, baseboardBinary: Uint8Array, wallSemanticIdx: number): Uint8Array | null;
+/**
+ * Build per-pixel energy map from BGR buffer.
+ * 1. Convert to grayscale via luminance weights
+ * 2. Downsample so longest side ≤ targetMaxSide
+ * 3. Apply Sobel 3×3 → gradient magnitude G
+ * 4. Energy = 1 / (1 + G), clamped to [0, 1]
+ */
+export declare function buildEnergyMap(bgrBuffer: Uint8Array, cols: number, rows: number, targetMaxSide?: number, allowedMask?: Uint8Array | null): EnergyMap;
+/**
+ * Dijkstra shortest-path on 8-connected grid.
+ * Cost at each pixel = energy[pixel] * COST_SCALE (integer).
+ * Diagonal steps cost √2 × the neighbour's energy.
+ *
+ * Returns ordered path [start, …, end] in energy-map pixel space.
+ */
+export declare function findShortestPath(energy: Float32Array, energyW: number, energyH: number, sx: number, sy: number, ex: number, ey: number, traversable?: Uint8Array | null): {
+    x: number;
+    y: number;
+}[];
+/**
+ * Douglas-Peucker simplification. Keeps points where the perpendicular
+ * distance from the line segment exceeds epsilon.
+ *
+ * After DP, also enforces a minimum distance between consecutive anchors
+ * to avoid overly dense clusters.
+ */
+export declare function extractCornerPoints(path: {
+    x: number;
+    y: number;
+}[], minDistance?: number, epsilon?: number): {
+    x: number;
+    y: number;
+}[];
+/** Map normalized image coords (0..1) to energy-map pixel coords. */
+export declare function normToEnergyPoint(normX: number, normY: number, em: EnergyMap): {
+    x: number;
+    y: number;
+};
+/** Map energy-map pixel coords back to normalized image coords. */
+export declare function energyPointsToNorm(points: {
+    x: number;
+    y: number;
+}[], em: EnergyMap): {
+    x: number;
+    y: number;
+}[];
+/** Map energy-map pixel coords back to original image coords. */
+export declare function upscalePath(points: {
+    x: number;
+    y: number;
+}[], scale: number, originW: number, originH: number): {
+    x: number;
+    y: number;
+}[];
--- a/dist/utils/magneticLasso.js
+++ b/dist/utils/magneticLasso.js
--- a/dist/utils/maskOutlinePaths.d.ts
+++ b/dist/utils/maskOutlinePaths.d.ts
@ -1,5 +1,6 @@
 import { type SkPath } from '@shopify/react-native-skia';
 import type { SegmentRegion, RegionMaskData } from './maskSegmentation';
+export declare function floodFillComponent(binary: Uint8Array, cols: number, rows: number, seedX: number, seedY: number): Uint8Array | null;
 export declare function buildRegionOutlinePathForRegion(regionId: number, regions: SegmentRegion[], maskData: RegionMaskData, rect: {
    x: number;
    y: number;
--- a/dist/utils/maskOutlinePaths.js
+++ b/dist/utils/maskOutlinePaths.js
--- a/dist/utils/maskSegmentRuntime.js
+++ b/dist/utils/maskSegmentRuntime.js
--- a/dist/utils/maskSegmentation.d.ts
+++ b/dist/utils/maskSegmentation.d.ts
@ -85,6 +85,10 @@ export type RegionMaskData = {
    cols: number;
    rows: number;
    wallSubLabels?: Uint8Array;
+    /** Semantic index → name table captured at segmentation time (must match labels buffer). */
+    indexToName?: string[];
+    /** Wall semantic index in labels buffer (captured at segmentation time). */
+    wallSemanticIdx?: number;
 };
 /** downsample mask path building (screen display does not need segmentation resolution, click still uses full resolution pickMap) */
 export declare function downsampleMaskDataForPaths(maskData: RegionMaskData, maxLongSide: number): RegionMaskData;
--- a/dist/utils/maskSegmentation.js
+++ b/dist/utils/maskSegmentation.js
--- a/dist/utils/wallTextureSplit.d.ts
+++ b/dist/utils/wallTextureSplit.d.ts
@ -1,6 +1,24 @@
 import type { SegmentMaskResult } from './maskSegmentation';
 /** Placeholder value for non-wall pixels in wallSubLabels */
 export declare const WALL_SUB_LABEL_NONE = 255;
+export declare function buildPickMapAfterWallSplit(labels: Uint8Array, baseboardBinary: Uint8Array, wallIdx: number, wallSubLabels: Uint8Array, indexToName: string[], nameToId: Map<string, number>, cols: number, rows: number): Uint8Array;
+/**
+ * Manual lasso split: copy the existing pick map and rewrite wall pixels only.
+ * Non-wall pick codes stay identical so prior paints and hit-testing remain stable.
+ */
+export declare function patchPickMapForManualWallSplit(existingPick: Uint8Array, labels: Uint8Array, baseboardBinary: Uint8Array, wallIdx: number, wallSubLabels: Uint8Array, nameToId: Map<string, number>, cols: number, rows: number): Uint8Array;
+export declare function dilatePickBuffer1px(pick: Uint8Array, cols: number, rows: number): Uint8Array;
+export type LassoPolyBBox = {
+    x: number;
+    y: number;
+    w: number;
+    h: number;
+};
+/**
+ * Morphologically dilate each lasso polygon into adjacent unassigned wall pixels
+ * (up to `dilateRadius` seg pixels) so thin gaps against the wall mask merge in.
+ */
+export declare function absorbSmallWallGapsForLassoPolygons(polyLabels: Uint8Array, polyCount: number, areas: number[], bboxes: LassoPolyBBox[], labels: Uint8Array, baseboardBinary: Uint8Array, wallSemanticIdx: number, priorAssignedLabels: Uint8Array, cols: number, rows: number, dilateRadius: number): void;
 /**
 * After semantic segmentation, subdivide the wall region into wall-1, wall-2… by source image texture features
 */
--- a/dist/utils/wallTextureSplit.js
+++ b/dist/utils/wallTextureSplit.js
--- a/docs/docs/api/index.md
+++ b/docs/docs/api/index.md
@ -23,6 +23,8 @@ import MaskSegmentCanvas, {
  type PaintConfig,
  type InteractionConfig,
  type SavePaintResult,
+  type LassoPolygon,
+  type ManualWallPartition,
  MASK_SEMANTIC_COLORS,
  BASEBOARD_SEMANTIC_NAME,
  prewarmPngBgrCacheAsync,
@ -38,6 +40,7 @@ import MaskSegmentCanvas, {
 | Component | `MaskSegmentCanvas` (default) |
 | Ref / Props types | `MaskSegmentCanvasRef`, `MaskSegmentCanvasProps` |
 | Session / callback types | `MaskSegmentSession`, `PaintCallbackPayload`, `PaintedRegionRecord`, `SavePaintResult` |
+| Lasso types | `LassoPolygon`, `ManualWallPartition` |
 | Watch types | `MaskSegmentWatchState`, `MaskSegmentWatchDetail` |
 | Config types | `PipelineConfig`, `MaskSegmentConfig`, `PaintConfig`, `InteractionConfig` |
 | Semantic colors | `MASK_SEMANTIC_COLORS`, `BASEBOARD_SEMANTIC_NAME` |
--- a/docs/docs/api/mask-config.md
+++ b/docs/docs/api/mask-config.md
@ -29,5 +29,23 @@ title: "Props: maskConfig"
 | `splitWallsColorDistSq` | `number` | `1400` | Connected-component chroma mean distance squared threshold |
 | `splitWallsChromaBlurRadius` | `number` | `5` | Reserved: chroma smoothing radius |
 | `splitWallsNeutralChromaMax` | `number` | `14` | White/gray wall low-chroma radius; forced boundary from colored walls |
+| `splitWallsEdgeBarrierThreshold` | `number` | `160` | Raw per-channel BGR Sobel gradient threshold for edge barriers (0 = disabled). Visible wall seams ≈ 120–280, subtle lighting gradients ≈ 20–80 |
+| `splitWallsCloseMaskRadius` | `number` | `3` | Morphological close radius for wall mask holes (windows, doors) before component labeling. 0 = disable |
+| `manualSplitWalls` | `boolean` | `false` | When `true`, disables automatic texture-based wall splitting. Manual lasso partitioning is used instead |
+| `manualSplitWallsMaxCount` | `number` | `8` | Maximum number of manual wall sub-regions defined by lasso |
+| `manualSplitWallsGapAbsorbDilatePx` | `number` | `5` | Morphological dilation radius (seg pixels) to merge thin unassigned wall pockets adjacent to the drawn polygon |
+| `magneticLasso` | `boolean` | `false` | When `true`, lasso mode uses edge-snapping via Sobel gradient + Dijkstra shortest-path |
+| `activeContourRefine` | `boolean` | `false` | After End Lasso, run active contour refinement on each polygon to expand vertices outward toward wall-mask edges |

 When `splitWalls` is enabled, the single `wall` region is replaced by multiple `wall-N` sub-regions, each independently paintable and undoable. Old sessions with `regionName: 'wall'` cannot map to new sub-region names and must be repainted.
+
+### Manual Wall Split (Lasso Mode)
+
+When `manualSplitWalls` is enabled, automatic texture-based wall splitting is disabled. Instead, users must use the **Lasso** feature to manually draw polygons on the wall area:
+
+- Call `ref.startLasso()` to enter lasso mode, then tap on wall areas to place polygon vertices.
+- Enable `magneticLasso` for edge-snapping — paths will follow strong image edges (Sobel gradient + Dijkstra shortest-path).
+- Enable `activeContourRefine` to automatically expand vertices outward toward the wall-mask boundary after lasso completion.
+- Call `ref.endLasso()` to convert closed lasso polygons into `wall-N` sub-regions for painting.
+- Use `splitWallsCloseMaskRadius` to fill wall mask holes (windows, doors) before component labeling during automatic split.
+- Use `splitWallsEdgeBarrierThreshold` to prevent BFS from crossing strong edges (window frames, door frames) during automatic split.
--- a/docs/docs/api/ref-methods.md
+++ b/docs/docs/api/ref-methods.md
@ -20,16 +20,29 @@ Accessed via `ref` (type `MaskSegmentCanvasRef`):
 | `resegment` | `() => Promise<void>` | Clear PNG cache and re-segment |
 | `getRegions` | `() => SegmentRegion[]` | Snapshot of current region list |
 | `getPaintedRegions` | `() => PaintedRegionRecord[]` | Snapshot of current paint records |
+| `getLastExport` | `() => SavePaintResult \| null` | Returns the most recent auto-export or `save()` result, if any |
+| `startLasso` | `() => void` | Enter lasso mode — user can tap wall mask area to place polygon vertices |
+| `endLasso` | `() => ManualWallPartition[]` | Exit lasso mode, convert all closed lasso polygons into `wall-X` sub-regions for painting |
+| `cancelLasso` | `() => void` | Exit the current lasso editing session without saving regions |
+| `getManualRegions` | `() => ManualWallPartition[]` | Get the current manual wall partitions (only valid after `endLasso`) |
+| `deleteLasso` | `(id: string) => void` | Delete a lasso polygon by its id. Committed partitions also drop paint on that region |

 ## SavePaintResult

 `{ filePath, width, height, paintedCount, previewPath? }`

+## ManualWallPartition
+
+`{ id, regionId, regionName, vertices, bbox, area }`
+
+Returned by `endLasso()` and `getManualRegions()`. Each partition maps a lasso polygon to a `wall-N` sub-region.
+
 ## Code Examples

 ```tsx
 const ref = useRef<MaskSegmentCanvasRef>(null);

+// Paint operations
 ref.current?.reset();
 ref.current?.swap();           // toggle
 ref.current?.swap(true);       // force show origin
@ -47,6 +60,15 @@ await ref.current?.resegment();

 const regions = ref.current?.getRegions();
 const painted = ref.current?.getPaintedRegions();
+
+// Lasso operations
+ref.current?.startLasso();                // enter lasso mode
+// ... user taps wall areas to place vertices ...
+const partitions = ref.current?.endLasso();  // convert polygons to wall-N regions
+ref.current?.cancelLasso();               // discard in-progress lasso
+
+const manualRegions = ref.current?.getManualRegions();
+ref.current?.deleteLasso('lasso_1');      // remove a specific polygon
 ```

 > `save` depends on the working buffer and pickMap being ready (typically after `interactive`); throws `'Image not ready, cannot save'` if not ready.
--- a/docs/docs/interaction-guide.md
+++ b/docs/docs/interaction-guide.md
@ -5,9 +5,33 @@ title: Interaction Guide

 # 🎮 Interaction Guide

+## Paint Mode
+
 1. 🔁 **Initial Carousel**: After regions are ready, each region's dashed outline flashes sequentially per `initRegionFlashMs` (default 1s); stops on first user touch.
 2. 🔍 **Preview (no brush selected)**: Long-press a region to show dashed outline for the connected component under the touch point; tapping a black area shows no outline.
 3. 🎨 **Paint (brush selected)**: Tap a color in the bottom color bar or call `ref.setPaintColor` (or preselect via `initialPaintColor`), then tap a region to paint; tapping the same region again overwrites the color.
 4. 💬 **Tap without brush**: No paint is performed; `onPaintCallback` fires with `kind: 'brush_required'`, carrying a `hint` and target region info for the host to show a toast/modal prompting color selection.
 5. ↩️ **Undo**: Bottom-left button or `ref.reset()`; steps backward through paint history one action at a time.
 6. 👁️ **Compare with Origin**: Bottom-right button or `ref.swap()`; hides the paint layer to show the original image.
+
+## Lasso Mode (Manual Wall Split)
+
+When `manualSplitWalls` is enabled and lasso mode is active:
+
+7. 🧲 **Enter Lasso**: Call `ref.startLasso()` to activate lasso mode. The lasso polygon overlay (orange) appears.
+8. 👆 **Place Vertices**: Tap on wall areas to place polygon vertices. Vertices snap to wall-mask edges/corners automatically.
+9. 🧲 **Magnetic Lasso** (when `magneticLasso: true`): Paths between taps automatically follow strong image edges (green path overlay) via Sobel gradient + Dijkstra shortest-path.
+10. 🔒 **Close Polygon**: Tap near the first vertex to close the polygon. A closed polygon is outlined in orange.
+11. ✋ **Drag Vertices**: Touch and drag an existing vertex to reposition it. The vertex snaps to wall boundary/corner points, or stays within the wall mask for interior positions.
+12. ✅ **End Lasso**: Call `ref.endLasso()` to convert all closed polygons into `wall-N` sub-regions ready for painting.
+13. 🗑️ **Cancel Lasso**: Call `ref.cancelLasso()` to discard all in-progress lasso polygons without saving.
+14. 🗑️ **Delete Lasso**: Call `ref.deleteLasso(id)` to remove a previously committed lasso polygon and its associated `wall-N` region.
+
+### Active Contour Refinement
+
+When `activeContourRefine: true`, the closed lasso polygon is automatically refined after `endLasso()`:
+
+- Each vertex samples positions along its outward normal direction
+- Vertices expand to the nearest wall-mask boundary edge (balloon force)
+- Douglas-Peucker simplification removes redundant vertices
+- Result: the polygon hugs the true wall outline rather than the raw tap positions
--- a/docs/docs/intro.md
+++ b/docs/docs/intro.md
@ -14,6 +14,7 @@ A React Native **0.79** interactive mask segmentation library. The core export i
 - 🧠 **OpenCV** (`react-native-fast-opencv`): mask semantic layout, baseboard patching, region extraction
 - 🖌️ **Skia RuntimeEffect (SkSL)**: single-pass full-screen shader blending original image + LAB low/high frequency texture color overlays
 - ✂️ **Skia Path**: dashed outline highlights for regions
+- 🧲 **Magnetic Lasso**: manual wall partitioning with edge-snapping (Sobel gradient + Dijkstra shortest-path) and Active Contour boundary refinement
 - 👆 **Interaction**: bottom color bar for brush selection (optional initialization) → tap a region to paint; tapping without a brush selected fires `onPaintCallback` with a hint; long-press without a brush previews the region's dashed outline

 This repository serves as both the **library source** (`src/index.ts`) and a **self-test demo** (root `App.tsx`).
@ -30,8 +31,9 @@ This repository serves as both the **library source** (`src/index.ts`) and a **s
 2. 🧩 **Segment** the mask via OpenCV into semantic regions (walls, ceiling, baseboard, etc.)
 3. 🎨 **Prepare** LAB frequency-layer textures via SkSL for realistic color blending
 4. 📐 **Build** Skia dashed-outline paths for each region
-5. 👆 **Interactive** — users select a brush color and tap regions to paint; paint layers preserve the underlying texture
-6. 💾 **Save** the composited result as PNG; export a JSON session for draft recovery
+5. 🧲 **Manual Split** (optional) — draw lasso polygons on walls to subdivide into independently-paintable `wall-N` regions, with optional edge-snapping and Active Contour refinement
+6. 👆 **Interactive** — users select a brush color and tap regions to paint; paint layers preserve the underlying texture
+7. 💾 **Save** the composited result as PNG; export a JSON session for draft recovery

 The component emits `onWatch` state transitions through the pipeline so the host app can show appropriate loading states.

--- a/docs/docs/project-structure.md
+++ b/docs/docs/project-structure.md
@ -17,6 +17,9 @@ MaskSegmentApp/                              # Repo root (npm package react-nati
 │       ├── maskSegmentation.ts
 │       ├── maskSegmentRuntime.ts
 │       ├── maskSemanticPalette.ts
+│       ├── magneticLasso.ts          # Edge-snapping lasso (Sobel + Dijkstra)
+│       ├── activeContour.ts          # Active Contour refinement (snake + balloon)
+│       ├── wallTextureSplit.ts       # Automatic & manual wall texture splitting
 │       └── ...
 ├── example/                                 # ★ Recommended: consumer-side integration demo
 │   ├── App.tsx                              # Full example using only the public API
--- a/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/api/index.md
+++ b/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/api/index.md
@ -23,6 +23,8 @@ import MaskSegmentCanvas, {
  type PaintConfig,
  type InteractionConfig,
  type SavePaintResult,
+  type LassoPolygon,
+  type ManualWallPartition,
  MASK_SEMANTIC_COLORS,
  BASEBOARD_SEMANTIC_NAME,
  prewarmPngBgrCacheAsync,
@ -38,6 +40,7 @@ import MaskSegmentCanvas, {
 | 组件 | `MaskSegmentCanvas`（默认导出） |
 | Ref / Props 类型 | `MaskSegmentCanvasRef`, `MaskSegmentCanvasProps` |
 | 会话 / 回调类型 | `MaskSegmentSession`, `PaintCallbackPayload`, `PaintedRegionRecord`, `SavePaintResult` |
+| 套索类型 | `LassoPolygon`, `ManualWallPartition` |
 | Watch 类型 | `MaskSegmentWatchState`, `MaskSegmentWatchDetail` |
 | 配置类型 | `PipelineConfig`, `MaskSegmentConfig`, `PaintConfig`, `InteractionConfig` |
 | 语义颜色 | `MASK_SEMANTIC_COLORS`, `BASEBOARD_SEMANTIC_NAME` |
--- a/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/api/mask-config.md
+++ b/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/api/mask-config.md
@ -29,5 +29,23 @@ title: "Props：maskConfig"
 | `splitWallsColorDistSq` | `number` | `1400` | 连通分量色度均值距离平方阈值 |
 | `splitWallsChromaBlurRadius` | `number` | `5` | 保留：色度平滑半径 |
 | `splitWallsNeutralChromaMax` | `number` | `14` | 白/灰墙面低色度半径；与彩色墙面的强制边界 |
+| `splitWallsEdgeBarrierThreshold` | `number` | `160` | 逐通道 BGR Sobel 梯度边缘屏障阈值（0 = 禁用）。可见墙面接缝 ≈ 120–280，细微光照渐变 ≈ 20–80 |
+| `splitWallsCloseMaskRadius` | `number` | `3` | 组件标注前墙面遮罩孔洞（窗户、门）的形态学闭运算半径。设为 0 禁用 |
+| `manualSplitWalls` | `boolean` | `false` | 为 `true` 时禁用自动纹理墙面分割，改为手动套索分区 |
+| `manualSplitWallsMaxCount` | `number` | `8` | 套索定义的最大手动墙面子区域数 |
+| `manualSplitWallsGapAbsorbDilatePx` | `number` | `5` | 形态学膨胀半径（分割像素），用于合并绘制多边形周围的未分配墙面薄缝 |
+| `magneticLasso` | `boolean` | `false` | 为 `true` 时，套索模式使用 Sobel 梯度 + Dijkstra 最短路径进行边缘吸附 |
+| `activeContourRefine` | `boolean` | `false` | 结束套索后，对每个多边形运行主动轮廓精炼，将顶点向外扩展到墙面遮罩边缘 |

 启用 `splitWalls` 后，单个 `wall` 区域将被替换为多个 `wall-N` 子区域，每个子区域可独立上色和撤销。旧会话中 `regionName: 'wall'` 的记录无法映射到新的子区域名称，需重新上色。
+
+### 手动墙面分割（套索模式）
+
+当 `manualSplitWalls` 启用时，自动纹理墙面分割被禁用。用户必须使用 **套索（Lasso）** 功能在墙面上手动绘制多边形：
+
+- 调用 `ref.startLasso()` 进入套索模式，然后在墙面区域点击放置多边形顶点。
+- 启用 `magneticLasso` 进行边缘吸附 — 路径将沿图像强边缘走（Sobel 梯度 + Dijkstra 最短路径）。
+- 启用 `activeContourRefine` 在套索完成后自动将顶点向外扩展到墙面遮罩边界。
+- 调用 `ref.endLasso()` 将闭合套索多边形转换为可上色的 `wall-N` 子区域。
+- 自动分割时使用 `splitWallsCloseMaskRadius` 填充墙面遮罩孔洞（窗户、门）。
+- 自动分割时使用 `splitWallsEdgeBarrierThreshold` 阻止 BFS 跨越强边缘（窗框、门框）。
--- a/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/api/ref-methods.md
+++ b/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/api/ref-methods.md
@ -20,16 +20,29 @@ title: "Ref 方法"
 | `resegment` | `() => Promise<void>` | 清除 PNG 缓存并重新分割 |
 | `getRegions` | `() => SegmentRegion[]` | 当前区域列表快照 |
 | `getPaintedRegions` | `() => PaintedRegionRecord[]` | 当前上色记录快照 |
+| `getLastExport` | `() => SavePaintResult \| null` | 返回最近一次自动导出或 `save()` 的结果（如有） |
+| `startLasso` | `() => void` | 进入套索模式 — 用户可在墙面区域点击放置多边形顶点 |
+| `endLasso` | `() => ManualWallPartition[]` | 退出套索模式，将所有闭合套索多边形转换为可上色的 `wall-X` 子区域 |
+| `cancelLasso` | `() => void` | 退出当前套索编辑会话，不保存区域 |
+| `getManualRegions` | `() => ManualWallPartition[]` | 获取当前手动墙面分区（仅在 `endLasso` 调用后有效） |
+| `deleteLasso` | `(id: string) => void` | 根据 id 删除套索多边形。已提交的分区也会删除该区域上的上色 |

 ## SavePaintResult

 `{ filePath, width, height, paintedCount, previewPath? }`

+## ManualWallPartition
+
+`{ id, regionId, regionName, vertices, bbox, area }`
+
+由 `endLasso()` 和 `getManualRegions()` 返回。每个分区将一个套索多边形映射到一个 `wall-N` 子区域。
+
 ## 代码示例

 ```tsx
 const ref = useRef<MaskSegmentCanvasRef>(null);

+// 上色操作
 ref.current?.reset();
 ref.current?.swap();           // 切换
 ref.current?.swap(true);       // 强制显示原始图像
@ -47,6 +60,15 @@ await ref.current?.resegment();

 const regions = ref.current?.getRegions();
 const painted = ref.current?.getPaintedRegions();
+
+// 套索操作
+ref.current?.startLasso();                // 进入套索模式
+// ... 用户在墙面区域点击放置顶点 ...
+const partitions = ref.current?.endLasso();  // 将多边形转换为 wall-N 区域
+ref.current?.cancelLasso();               // 丢弃进行中的套索
+
+const manualRegions = ref.current?.getManualRegions();
+ref.current?.deleteLasso('lasso_1');      // 删除指定多边形
 ```

 > `save` 依赖于工作缓冲区和 pickMap 就绪（通常在 `interactive` 之后）；如果未就绪则抛出 `'Image not ready, cannot save'`。
--- a/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/interaction-guide.md
+++ b/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/interaction-guide.md
@ -5,9 +5,33 @@ title: 交互指南

 # 🎮 交互指南

+## 上色模式
+
 1. 🔁 **初始轮播**：区域就绪后，每个区域的虚线轮廓按 `initRegionFlashMs`（默认 1s）依次闪烁；首次用户触摸时停止。
 2. 🔍 **预览（未选择画笔）**：长按区域可显示触摸点下连通分量的虚线轮廓；点击黑色区域不显示轮廓。
 3. 🎨 **上色（已选择画笔）**：点击底部颜色条中的颜色或调用 `ref.setPaintColor`（或通过 `initialPaintColor` 预设），然后点击区域上色；再次点击同一区域会覆盖颜色。
 4. 💬 **无画笔点击**：不执行上色；`onPaintCallback` 触发 `kind: 'brush_required'`，携带提示信息和目标区域信息，供宿主显示 Toast/弹窗提示选择颜色。
 5. ↩️ **撤销**：左下按钮或 `ref.reset()`；按上色历史逐步后退。
 6. 👁️ **与原图对比**：右下按钮或 `ref.swap()`；隐藏上色层以显示原图。
+
+## 套索模式（手动墙面分割）
+
+当 `manualSplitWalls` 启用且套索模式激活时：
+
+7. 🧲 **进入套索**：调用 `ref.startLasso()` 激活套索模式。套索多边形叠加层（橙色）出现。
+8. 👆 **放置顶点**：点击墙面区域放置多边形顶点。顶点会自动吸附到墙面遮罩边缘/角点。
+9. 🧲 **磁性套索**（当 `magneticLasso: true`）：点击之间的路径自动沿图像强边缘走（绿色路径叠加层），通过 Sobel 梯度 + Dijkstra 最短路径实现。
+10. 🔒 **闭合多边形**：点击第一个顶点附近闭合多边形。闭合多边形以橙色轮廓显示。
+11. ✋ **拖拽顶点**：触摸并拖拽已有顶点重新定位。顶点吸附到墙面边界/角点，或保持在墙面遮罩内部位置。
+12. ✅ **结束套索**：调用 `ref.endLasso()` 将所有闭合多边形转换为可上色的 `wall-N` 子区域。
+13. 🗑️ **取消套索**：调用 `ref.cancelLasso()` 丢弃所有进行中的套索多边形，不保存。
+14. 🗑️ **删除套索**：调用 `ref.deleteLasso(id)` 删除之前提交的套索多边形及其关联的 `wall-N` 区域。
+
+### 主动轮廓精炼
+
+当 `activeContourRefine: true` 时，闭合套索多边形在 `endLasso()` 后自动精炼：
+
+- 每个顶点沿其外法线方向采样位置
+- 顶点向外扩展到最近的墙面遮罩边界边缘（气球队列力）
+- Douglas-Peucker 简化去除冗余顶点
+- 结果：多边形贴合真实墙面轮廓，而非原始点击位置
--- a/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/intro.md
+++ b/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/intro.md
@ -10,6 +10,7 @@ title: 概述
 - 🧠 **OpenCV** (`react-native-fast-opencv`)：遮罩语义布局、踢脚线修补、区域提取
 - 🖌️ **Skia RuntimeEffect (SkSL)**：单 Pass 全屏着色器，混合原图 + LAB 低频/高频纹理颜色叠加
 - ✂️ **Skia Path**：区域虚线轮廓高亮
+- 🧲 **磁性套索（Magnetic Lasso）**：手动墙面分区，支持边缘吸附（Sobel 梯度 + Dijkstra 最短路径）和主动轮廓边界精炼
 - 👆 **交互**：底部颜色条选择画笔（可选初始化）→ 点击区域上色；未选择画笔时点击会触发 `onPaintCallback` 并附带提示；未选画笔时长按可预览区域的虚线轮廓

 本仓库同时作为 **库源码**（`src/index.ts`）和 **自测 Demo**（根目录 `App.tsx`）。
@ -26,8 +27,9 @@ title: 概述
 2. 🧩 **分割**通过 OpenCV 将遮罩分割为语义区域（墙面、天花板、踢脚线等）
 3. 🎨 **准备**通过 SkSL 生成 LAB 频域层纹理，实现逼真的颜色混合
 4. 📐 **构建**每个区域的 Skia 虚线轮廓路径
-5. 👆 **交互** — 用户选择画笔颜色并点击区域上色；上色层保留底层纹理
-6. 💾 **保存**合成结果为 PNG；导出 JSON 会话用于草稿恢复
+5. 🧲 **手动分割**（可选）— 在墙面上绘制套索多边形，将其细分为可独立上色的 `wall-N` 区域，可选边缘吸附和主动轮廓精炼
+6. 👆 **交互** — 用户选择画笔颜色并点击区域上色；上色层保留底层纹理
+7. 💾 **保存**合成结果为 PNG；导出 JSON 会话用于草稿恢复

 组件通过 `onWatch` 发出 Pipeline 状态转换，宿主应用可据此显示相应的加载状态。

--- a/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/project-structure.md
+++ b/docs/i18n/zh-CN/docusaurus-plugin-content-docs/current/project-structure.md
@ -17,6 +17,9 @@ MaskSegmentApp/                              # 仓库根目录（npm 包 react-n
 │       ├── maskSegmentation.ts
 │       ├── maskSegmentRuntime.ts
 │       ├── maskSemanticPalette.ts
+│       ├── magneticLasso.ts          # 边缘吸附套索（Sobel + Dijkstra）
+│       ├── activeContour.ts          # 主动轮廓精炼（Snake + Balloon）
+│       ├── wallTextureSplit.ts       # 自动与手动墙面纹理分割
 │       └── ...
 ├── example/                                 # ★ 推荐：消费方集成 Demo
 │   ├── App.tsx                              # 仅使用公开 API 的完整示例
--- a/example/App.tsx
+++ b/example/App.tsx
@ -24,6 +24,7 @@ import { SafeAreaProvider, SafeAreaView } from 'react-native-safe-area-context';

 import MaskSegmentCanvas, {
  type BgrColor,
+  type ManualWallPartition,
  type MaskSegmentCanvasRef,
  type MaskSegmentSession,
  type MaskSegmentWatchState,
@ -122,6 +123,11 @@ function App(): React.JSX.Element {
  // Demo mode
  const [useCustomColors, setUseCustomColors] = useState(false);
  const [splitWalls, setSplitWalls] = useState(false);
+  const [manualSplitWalls, setManualSplitWalls] = useState(false);
+  const [magneticLasso, setMagneticLasso] = useState(false);
+  const [activeContourRefine, setActiveContourRefine] = useState(false);
+  const [splitEdgeBarrier, setSplitEdgeBarrier] = useState(false);
+  const [isLassoing, setIsLassoing] = useState(false);
  const [pipelinePreset, setPipelinePreset] = useState<PipelinePreset>('medium');
  const [groupIndex, setGroupIndex] = useState(0);

@ -272,6 +278,77 @@ function App(): React.JSX.Element {
    [showToast],
  );

+  const handleStartLasso = useCallback(() => {
+    canvasRef.current?.startLasso();
+    setIsLassoing(true);
+    showToast('Lasso mode: tap wall area to place vertices');
+  }, [showToast]);
+
+  const handleEndLasso = useCallback(() => {
+    const parts = canvasRef.current?.endLasso();
+    setIsLassoing(false);
+    if (parts && parts.length > 0) {
+      showToast(`Lasso ended: ${parts.length} wall sub-regions created`);
+      console.log(
+        '[Example] Manual wall partitions:',
+        JSON.stringify(
+          parts.map(p => ({ id: p.id, regionName: p.regionName, area: p.area })),
+          null,
+          2,
+        ),
+      );
+    } else {
+      showToast('Lasso ended (no polygons to convert)');
+    }
+  }, [showToast]);
+
+  const handleCancelLasso = useCallback(() => {
+    canvasRef.current?.cancelLasso();
+    setIsLassoing(false);
+    showToast('Lasso cancelled (regions not saved)');
+  }, [showToast]);
+
+  const handleDeleteLasso = useCallback(() => {
+    const parts = canvasRef.current?.getManualRegions();
+    if (!parts || parts.length === 0) {
+      showToast('No lasso polygons to delete');
+      return;
+    }
+    const last = parts[parts.length - 1];
+    canvasRef.current?.deleteLasso(last.id);
+    showToast(`Deleted lasso: ${last.regionName}`);
+  }, [showToast]);
+
+  const handleGetLassoRegions = useCallback(() => {
+    const parts = canvasRef.current?.getManualRegions();
+    if (!parts || parts.length === 0) {
+      Alert.alert('Manual Regions', 'No manual wall partitions available.');
+      return;
+    }
+    const summary = parts
+      .map(
+        (p: ManualWallPartition) =>
+          `  ${p.regionName}: area=${p.area}, bbox=(${p.bbox.x},${p.bbox.y} ${p.bbox.w}x${p.bbox.h})`,
+      )
+      .join('\n');
+    Alert.alert('Manual Wall Partitions', `${parts.length} regions:\n${summary}`);
+    console.log(
+      '[Example] getManualRegions:',
+      JSON.stringify(
+        parts.map(p => ({
+          id: p.id,
+          regionId: p.regionId,
+          regionName: p.regionName,
+          area: p.area,
+          bbox: p.bbox,
+          vertexCount: p.vertices.length,
+        })),
+        null,
+        2,
+      ),
+    );
+  }, []);
+
  // --------------------------------------------------------------------------
  // render: error / loading / ready
  // --------------------------------------------------------------------------
@ -381,13 +458,65 @@ function App(): React.JSX.Element {
              (split walls)
            </Text>
          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.modeChip, manualSplitWalls && styles.modeChipActive]}
+            onPress={() => {
+              setManualSplitWalls(v => !v);
+              if (!manualSplitWalls) {
+                setSplitWalls(false);
+              }
+            }}
+          >
+            <Text style={[styles.modeChipText, manualSplitWalls && styles.modeChipTextActive]}>
+              (manual split)
+            </Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.modeChip, magneticLasso && styles.modeChipLassoActive]}
+            onPress={() => {
+              setMagneticLasso(v => !v);
+              if (!magneticLasso) {
+                setManualSplitWalls(true);
+              }
+            }}
+          >
+            <Text style={[styles.modeChipText, magneticLasso && styles.modeChipTextActive]}>
+              (magnetic)
+            </Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.modeChip, activeContourRefine && styles.modeChipLassoActive]}
+            onPress={() => {
+              setActiveContourRefine(v => !v);
+              if (!activeContourRefine) {
+                setManualSplitWalls(true);
+              }
+            }}
+          >
+            <Text style={[styles.modeChipText, activeContourRefine && styles.modeChipTextActive]}>
+              (contour)
+            </Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.modeChip, splitEdgeBarrier && styles.modeChipActive]}
+            onPress={() => {
+              setSplitEdgeBarrier(v => !v);
+              if (!splitEdgeBarrier) {
+                setSplitWalls(true);
+              }
+            }}
+          >
+            <Text style={[styles.modeChipText, splitEdgeBarrier && styles.modeChipTextActive]}>
+              (edge barrier)
+            </Text>
+          </TouchableOpacity>
        </ScrollView>
      </View>

      {/* canvas */}
      <View style={styles.canvasHost}>
        <MaskSegmentCanvas
-          key={`image-group-${groupIndex}-split-${splitWalls ? 1 : 0}`}
+          key={`image-group-${groupIndex}-split-${splitWalls ? 1 : 0}-manual-${manualSplitWalls ? 1 : 0}-magnetic-${magneticLasso ? 1 : 0}-contour-${activeContourRefine ? 1 : 0}-ebarrier-${splitEdgeBarrier ? 1 : 0}`}
          ref={canvasRef}
          style={styles.canvas}
          originUrl={imagePaths.origin}
@ -399,6 +528,11 @@ function App(): React.JSX.Element {
            ...DEFAULT_MASK_CONFIG,
            maxRegionColors: 6,
            splitWalls,
+            manualSplitWalls,
+            manualSplitWallsMaxCount: 8,
+            magneticLasso,
+            activeContourRefine,
+            splitWallsEdgeBarrierThreshold: splitEdgeBarrier ? 160 : 0,
          }}
          paintConfig={{
            ...DEFAULT_PAINT_CONFIG,
@ -493,6 +627,46 @@ function App(): React.JSX.Element {
          >
            <Text style={styles.actionBtnText}>Export session</Text>
          </TouchableOpacity>
+
+          <View style={styles.divider} />
+
+          {/* Lasso operations */}
+          <Text style={styles.sectionLabel}>Lasso:</Text>
+          <TouchableOpacity
+            style={[styles.actionBtn, isLassoing && styles.actionBtnLassoActive]}
+            onPress={handleStartLasso}
+            disabled={!isInteractive || !manualSplitWalls || isLassoing}
+          >
+            <Text style={styles.actionBtnText}>Start Lasso</Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.actionBtn, styles.actionBtnPrimary]}
+            onPress={handleEndLasso}
+            disabled={!isInteractive || !manualSplitWalls || !isLassoing}
+          >
+            <Text style={styles.actionBtnTextPrimary}>End Lasso</Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.actionBtn, styles.actionBtnDanger]}
+            onPress={handleCancelLasso}
+            disabled={!isInteractive || !manualSplitWalls || !isLassoing}
+          >
+            <Text style={styles.actionBtnText}>Cancel Lasso</Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={[styles.actionBtn, styles.actionBtnDanger]}
+            onPress={handleDeleteLasso}
+            disabled={!isInteractive || !manualSplitWalls}
+          >
+            <Text style={styles.actionBtnText}>Del Lasso</Text>
+          </TouchableOpacity>
+          <TouchableOpacity
+            style={styles.actionBtn}
+            onPress={handleGetLassoRegions}
+            disabled={!isInteractive || !manualSplitWalls}
+          >
+            <Text style={styles.actionBtnText}>Get Regions</Text>
+          </TouchableOpacity>
        </ScrollView>
      </View>

@ -585,6 +759,9 @@ const styles = StyleSheet.create({
  modeChipActive: {
    backgroundColor: '#4363D8',
  },
+  modeChipLassoActive: {
+    backgroundColor: '#00C853',
+  },
  modeChipText: {
    fontSize: 11,
    color: '#666',
@ -697,6 +874,10 @@ const styles = StyleSheet.create({
  actionBtnDanger: {
    borderColor: '#e88',
  },
+  actionBtnLassoActive: {
+    backgroundColor: '#FF6B35',
+    borderColor: '#FF6B35',
+  },
  actionBtnText: {
    fontSize: 12,
    color: '#555',
--- a/package.json
+++ b/package.json
@ -1,6 +1,6 @@
 {
  "name": "react-native-mask-segment-canvas",
-  "version": "0.3.0",
+  "version": "0.4.0",
  "description": "React Native mask segmentation canvas library: OpenCV semantic segmentation + SkSL Shader coloring",
  "main": "dist/index.js",
  "module": "dist/index.js",
--- a/src/components/MaskSegmentCanvas.tsx
+++ b/src/components/MaskSegmentCanvas.tsx
--- a/src/components/MaskSegmentCanvas.types.ts
+++ b/src/components/MaskSegmentCanvas.types.ts
@ -64,6 +64,33 @@ export type MaskSegmentConfig = {
  splitWallsChromaBlurRadius?: number;
  /** wall mask only, low saturation (white/gray wall) junction radius, used to force separate colored walls */
  splitWallsNeutralChromaMax?: number;
+  /**
+   * Wall split: raw per-channel BGR Sobel gradient threshold for edge barriers
+   * (0 = disabled). Uses un-normalized 8‑bit Sobel magnitude on each B/G/R
+   * channel (max per pixel, range ≈ 0–1442). Visible wall seams ≈ 120–280,
+   * subtle lighting gradients ≈ 20–80. Default: 160.
+   */
+  splitWallsEdgeBarrierThreshold?: number;
+  /**
+   * Morphological close radius for wall mask holes before component labeling.
+   * Non-wall pixels inside the wall boundary (windows, doors, mask artefacts)
+   * are temporarily filled so the BFS can bridge across them. Default: 3.
+   * Set to 0 to disable.
+   */
+  splitWallsCloseMaskRadius?: number;
+  /** When true, disables automatic texture-based wall splitting (splitWalls). Manual lasso partitioning is used instead. */
+  manualSplitWalls?: boolean;
+  /** wall mask only, max number of manual wall sub-regions defined by lasso */
+  manualSplitWallsMaxCount?: number;
+  /**
+   * Manual lasso: morphological dilation radius (seg pixels) used to merge thin
+   * unassigned wall pockets adjacent to the drawn polygon.
+   */
+  manualSplitWallsGapAbsorbDilatePx?: number;
+  /** When true, lasso mode uses edge-snapping (Sobel gradient + Dijkstra shortest-path). Default: false. */
+  magneticLasso?: boolean;
+  /** After End Lasso, run active contour refinement on each polygon to expand vertices outward toward wall-mask edges. Default: false. */
+  activeContourRefine?: boolean;
 };

 export type PaintConfig = {
@ -138,6 +165,23 @@ export type PaintBrushRequiredPayload = {

 export type PaintCallbackPayload = PaintSuccessPayload | PaintBrushRequiredPayload;

+/** A lasso polygon defined by user tapping vertices on the wall mask area. Vertices are in normalized image coordinates (0..1). */
+export type LassoPolygon = {
+  id: string;
+  vertices: { x: number; y: number }[];
+  isClosed: boolean;
+};
+
+/** Result of converting a lasso polygon into an actual wall sub-region. */
+export type ManualWallPartition = {
+  id: string;
+  regionId: number;
+  regionName: string;
+  vertices: { x: number; y: number }[];
+  bbox: { x: number; y: number; w: number; h: number };
+  area: number;
+};
+
 export type MaskSegmentCanvasRef = {
  reset: () => void;
  swap: (showOrigin?: boolean) => void;
@ -154,6 +198,20 @@ export type MaskSegmentCanvasRef = {
  getPaintedRegions: () => PaintedRegionRecord[];
  /** Returns the most recent auto-export or save() result, if any. */
  getLastExport?: () => SavePaintResult | null;
+  /** Enter lasso mode — user can tap wall mask area to place polygon vertices. */
+  startLasso: () => void;
+  /** Exit lasso mode, convert all closed lasso polygons into wall-X sub-regions for painting. Returns the partition results. */
+  endLasso: () => ManualWallPartition[];
+  /**
+   * Exit the current lasso editing session without saving regions.
+   * Discards in-progress vertices and closed polygons from this session only;
+   * previously committed manual wall partitions are kept.
+   */
+  cancelLasso: () => void;
+  /** Get the current manual wall partitions (only valid after endLasso has been called). */
+  getManualRegions: () => ManualWallPartition[];
+  /** Delete a lasso polygon by its id. Committed partitions also drop paint on that region. */
+  deleteLasso: (id: string) => void;
 };

 export type MaskSegmentCanvasProps = {
--- a/src/index.ts
+++ b/src/index.ts
@ -2,6 +2,8 @@ export { default } from './components/MaskSegmentCanvas';
 export type {
  BgrColor,
  InteractionConfig,
+  LassoPolygon,
+  ManualWallPartition,
  MaskSegmentCanvasProps,
  MaskSegmentCanvasRef,
  MaskSegmentConfig,
--- a/src/utils/activeContour.ts
+++ b/src/utils/activeContour.ts
@ -0,0 +1,380 @@
+/**
+ * Active Contour Model — greedy snake + balloon force.
+ *
+ * After the user finishes a lasso polygon, this module refines the boundary
+ * vertices outward toward the true wall-mask edge. Each vertex samples
+ * positions along its outward normal and picks the one with lowest energy.
+ *
+ * Pipeline:
+ *   1. Subdivide polygon to get evenly-spaced control points
+ *   2. For each iteration (3-5 rounds):
+ *      a. Compute outward normal at each point
+ *      b. Sample N positions along the normal (outward first, then inward)
+ *      c. Score each position: E = E_edge + E_smooth
+ *      d. Move vertex to min-energy position (constrained to wall mask)
+ *   3. Douglas-Peucker simplify
+ */
+
+import {
+  isNormPointOnWallMask,
+  type WallMaskSample,
+} from './magneticLasso';
+
+/* ==========================================================================
+ * Types
+ * ========================================================================== */
+
+export type ActiveContourOpts = {
+  /** Number of greedy iterations (default 3). */
+  iterations?: number;
+  /** Number of sample positions along normal per direction (default 6). */
+  samplesPerDirection?: number;
+  /** Step size (norm coords) between samples (default 0.003). */
+  sampleStep?: number;
+  /** Smoothness weight — higher keeps vertices more uniformly spaced (default 0.15). */
+  smoothWeight?: number;
+  /** Edge weight — higher makes contour hug mask boundary (default 1.0). */
+  edgeWeight?: number;
+  /** Balloon bias — extra outward push per iteration (default 0.002). */
+  balloonForce?: number;
+  /** Minimum vertex count for a polygon to be refined (default 4). */
+  minVertices?: number;
+};
+
+const DEFAULT_OPTS: Required<ActiveContourOpts> = {
+  iterations: 3,
+  samplesPerDirection: 6,
+  sampleStep: 0.003,
+  smoothWeight: 0.15,
+  edgeWeight: 1.0,
+  balloonForce: 0.002,
+  minVertices: 4,
+};
+
+/* ==========================================================================
+ * Helpers
+ * ========================================================================== */
+
+function computeOutwardNormal(
+  prev: { x: number; y: number },
+  curr: { x: number; y: number },
+  next: { x: number; y: number },
+): { x: number; y: number } {
+  const dx1 = curr.x - prev.x;
+  const dy1 = curr.y - prev.y;
+  const dx2 = next.x - curr.x;
+  const dy2 = next.y - curr.y;
+
+  // Average tangent direction at curr
+  const tx = dx1 + dx2;
+  const ty = dy1 + dy2;
+
+  // Normal (rotate 90° CCW) — two candidates
+  const nx1 = -ty;
+  const ny1 = tx;
+  const nx2 = ty;
+  const ny2 = -tx;
+
+  // Choose the outward normal: the one that points away from centroid
+  // A simple heuristic: the direction with positive dot product with
+  // (curr - centroid). Since we can't compute centroid cheaply each time,
+  // use a nearby point approximation: the direction that points to larger
+  // edge energy (i.e., toward wall boundary). We'll pick the direction
+  // that pushes the polygon out.
+  //
+  // For now we use the convention: the normal pointing toward positive
+  // sweep (CCW polygon → normal should point outward).
+  // We'll verify by computing the cross product of the normal with the
+  // edge direction.
+  const cross1 = dx2 * ny1 - dy2 * nx1;
+  const cross2 = dx2 * ny2 - dy2 * nx2;
+
+  const len = Math.hypot(nx1, ny1);
+  if (len < 1e-8) {
+    return { x: 0, y: 0 };
+  }
+
+  // For a CCW polygon, the outward normal is the one with negative cross product
+  const [nx, ny] = cross1 < cross2 ? [nx1, ny1] : [nx2, ny2];
+
+  return {
+    x: nx / len,
+    y: ny / len,
+  };
+}
+
+/**
+ * Distance to the nearest wall-mask boundary pixel.
+ * Returns [0..∞) in normalized coordinate space.
+ * Uses a fast spiral search within maxRadius.
+ */
+function distToWallBoundary(
+  normX: number,
+  normY: number,
+  mask: WallMaskSample,
+  maxRadius: number,
+): number {
+  const { labels, baseboardBinary, cols, rows, wallSemanticIdx } = mask;
+  if (cols <= 0 || rows <= 0) return maxRadius;
+
+  const cx = Math.round(normX * cols);
+  const cy = Math.round(normY * rows);
+  const r = Math.ceil(maxRadius);
+  let best = maxRadius + 1;
+
+  for (let dy = -r; dy <= r; dy++) {
+    for (let dx = -r; dx <= r; dx++) {
+      const x = cx + dx;
+      const y = cy + dy;
+      if (x < 0 || y < 0 || x >= cols || y >= rows) continue;
+      const i = y * cols + x;
+      if (labels[i] !== wallSemanticIdx || baseboardBinary[i]) continue;
+      // Check if this is a boundary pixel (adjacent to non-wall)
+      if (
+        x === 0 || y === 0 || x === cols - 1 || y === rows - 1 ||
+        labels[i - 1] !== wallSemanticIdx ||
+        labels[i + 1] !== wallSemanticIdx ||
+        labels[i - cols] !== wallSemanticIdx ||
+        labels[i + cols] !== wallSemanticIdx
+      ) {
+        const dist = Math.hypot(dx, dy);
+        if (dist < best) best = dist;
+      }
+    }
+  }
+
+  // Convert from seg pixels to normalized space
+  return best / Math.max(cols, rows);
+}
+
+/**
+ * Score a candidate position:
+ *   E = edgeWeight * edgeEnergy + smoothWeight * smoothEnergy - balloonForce
+ *
+ * Lower score = better.
+ * Edge energy is distance to nearest wall boundary (0 = on boundary).
+ * Smooth energy penalizes large deviations from the median of neighbors.
+ */
+function scorePosition(
+  nx: number,
+  ny: number,
+  mask: WallMaskSample,
+  maxEdgeDist: number,
+  neighbors: { x: number; y: number }[],
+  opts: Required<ActiveContourOpts>,
+): number {
+  if (!isNormPointOnWallMask(nx, ny, mask)) {
+    return 1e6; // reject
+  }
+
+  const edge = distToWallBoundary(nx, ny, mask, maxEdgeDist) / maxEdgeDist;
+
+  let smooth = 0;
+  if (neighbors.length >= 2) {
+    const n0 = neighbors[0];
+    const n1 = neighbors[neighbors.length - 1];
+    const mx = (n0.x + n1.x) / 2;
+    const my = (n0.y + n1.y) / 2;
+    smooth = Math.hypot(nx - mx, ny - my);
+  }
+
+  return opts.edgeWeight * edge + opts.smoothWeight * smooth;
+}
+
+/* ==========================================================================
+ * Subdivision — insert points where consecutive vertices are far apart
+ * ========================================================================== */
+
+function subdividePolygon(
+  vertices: { x: number; y: number }[],
+  maxGap: number,
+): { x: number; y: number }[] {
+  if (vertices.length < 2) return [...vertices];
+  const result: { x: number; y: number }[] = [];
+  const n = vertices.length;
+  for (let i = 0; i < n; i++) {
+    const a = vertices[i];
+    const b = vertices[(i + 1) % n];
+    result.push({ ...a });
+    const dist = Math.hypot(b.x - a.x, b.y - a.y);
+    const steps = Math.floor(dist / maxGap);
+    if (steps > 1) {
+      for (let s = 1; s < steps; s++) {
+        const t = s / steps;
+        result.push({
+          x: a.x + t * (b.x - a.x),
+          y: a.y + t * (b.y - a.y),
+        });
+      }
+    }
+  }
+  return result;
+}
+
+/* ==========================================================================
+ * Main
+ * ========================================================================== */
+
+/**
+ * Refine a single closed lasso polygon to hug the wall-mask outer boundary.
+ *
+ * Returns a new vertex list (not mutated in place). Returns the original
+ * polygon unchanged if it has too few vertices or no wall mask is given.
+ */
+export function refinePolygonToWallEdges(
+  vertices: { x: number; y: number }[],
+  mask: WallMaskSample,
+  opts?: ActiveContourOpts,
+): { x: number; y: number }[] {
+  const o = { ...DEFAULT_OPTS, ...opts };
+  if (vertices.length < o.minVertices || !mask) {
+    return [...vertices];
+  }
+
+  // 1. Subdivide to get evenly-spaced control points
+  let points = subdividePolygon(vertices, o.sampleStep * 2);
+
+  // 2. Greedy iteration loop
+  const maxEdgeDist = o.samplesPerDirection * o.sampleStep * Math.max(mask.cols, mask.rows);
+  const segPxEdgeDist = o.samplesPerDirection * o.sampleStep * Math.max(mask.cols, mask.rows);
+
+  for (let iter = 0; iter < o.iterations; iter++) {
+    const newPoints: { x: number; y: number }[] = [];
+    const m = points.length;
+
+    for (let i = 0; i < m; i++) {
+      const prev = points[(i - 1 + m) % m];
+      const curr = points[i];
+      const next = points[(i + 1) % m];
+
+      const normal = computeOutwardNormal(prev, curr, next);
+      if (normal.x === 0 && normal.y === 0) {
+        newPoints.push({ ...curr });
+        continue;
+      }
+
+      let bestPt = { ...curr };
+      let bestScore = scorePosition(
+        curr.x, curr.y, mask, segPxEdgeDist,
+        [prev, next], o,
+      );
+
+      // Apply balloon force: bias outward by extra offset
+      const balloonOffset = o.balloonForce * (iter + 1);
+
+      // Sample positions: outward first (balloon force region), then inward
+      for (let d = 1; d <= o.samplesPerDirection; d++) {
+        const dist = d * o.sampleStep;
+
+        // Outward (balloon direction)
+        const nxOut = curr.x + normal.x * (dist + balloonOffset);
+        const nyOut = curr.y + normal.y * (dist + balloonOffset);
+        const scoreOut = scorePosition(
+          nxOut, nyOut, mask, segPxEdgeDist,
+          [newPoints.length > 0 ? newPoints[newPoints.length - 1] : points[(i - 1 + m) % m], next],
+          o,
+        );
+        if (scoreOut < bestScore) {
+          bestScore = scoreOut;
+          bestPt = { x: nxOut, y: nyOut };
+        }
+
+        // Inward (conservative)
+        const nxIn = curr.x - normal.x * dist;
+        const nyIn = curr.y - normal.y * dist;
+        const scoreIn = scorePosition(
+          nxIn, nyIn, mask, segPxEdgeDist,
+          [newPoints.length > 0 ? newPoints[newPoints.length - 1] : points[(i - 1 + m) % m], next],
+          o,
+        );
+        if (scoreIn < bestScore) {
+          bestScore = scoreIn;
+          bestPt = { x: nxIn, y: nyIn };
+        }
+      }
+
+      newPoints.push(bestPt);
+    }
+
+    points = newPoints;
+  }
+
+  // 3. Douglas-Peucker simplify
+  const simplified = douglasPeucker(points, 0.002);
+  if (simplified.length < 3) return [...vertices];
+
+  // Ensure closed
+  const first = simplified[0];
+  const last = simplified[simplified.length - 1];
+  if (Math.hypot(first.x - last.x, first.y - last.y) > 0.0005) {
+    simplified.push({ ...first });
+  }
+
+  return simplified;
+}
+
+/* ==========================================================================
+ * Douglas-Peucker (inlined for independence)
+ * ========================================================================== */
+
+function douglasPeucker(
+  path: { x: number; y: number }[],
+  epsilon: number,
+): { x: number; y: number }[] {
+  if (path.length <= 2) return [...path];
+
+  const keep = new Uint8Array(path.length);
+  keep[0] = 1;
+  keep[path.length - 1] = 1;
+
+  function recurse(s: number, e: number) {
+    if (e - s <= 1) return;
+    const ax = path[s].x;
+    const ay = path[s].y;
+    const bx = path[e].x;
+    const by = path[e].y;
+    const dx = bx - ax;
+    const dy = by - ay;
+    const lenSq = dx * dx + dy * dy;
+
+    let maxDist = 0;
+    let maxIdx = s;
+    for (let i = s + 1; i < e; i++) {
+      let dist: number;
+      if (lenSq === 0) {
+        dist = Math.hypot(path[i].x - ax, path[i].y - ay);
+      } else {
+        const t = Math.max(0, Math.min(1,
+          ((path[i].x - ax) * dx + (path[i].y - ay) * dy) / lenSq,
+        ));
+        const px = ax + t * dx;
+        const py = ay + t * dy;
+        dist = Math.hypot(path[i].x - px, path[i].y - py);
+      }
+      if (dist > maxDist) {
+        maxDist = dist;
+        maxIdx = i;
+      }
+    }
+    if (maxDist > epsilon) {
+      keep[maxIdx] = 1;
+      recurse(s, maxIdx);
+      recurse(maxIdx, e);
+    }
+  }
+
+  recurse(0, path.length - 1);
+
+  // Enforce minimum distance between consecutive anchors
+  const result: { x: number; y: number }[] = [];
+  for (let i = 0; i < path.length; i++) {
+    if (!keep[i]) continue;
+    if (result.length > 0) {
+      const last = result[result.length - 1];
+      if (Math.hypot(path[i].x - last.x, path[i].y - last.y) < 0.001) continue;
+    }
+    result.push({ x: path[i].x, y: path[i].y });
+  }
+
+  return result;
+}
--- a/src/utils/magneticLasso.ts
+++ b/src/utils/magneticLasso.ts
@ -0,0 +1,621 @@
+/**
+ * Magnetic Lasso — edge-snapping polygon placement for manual wall splitting.
+ *
+ * Pipeline:
+ *   1. buildEnergyMap   → grayscale + downsample + Sobel gradient → energy grid
+ *   2. findShortestPath → Dijkstra 8-connected on low-energy (edge) pixels
+ *   3. extractCornerPoints → Douglas-Peucker simplification on raw path
+ *   4. upscalePath      → map energy-space coords back to original image coords
+ */
+
+/* ==========================================================================
+ * Types
+ * ========================================================================== */
+
+export type EnergyMap = {
+  /** Float32Array per-pixel energy values [0…1]; low = edge, high = flat */
+  map: Float32Array;
+  w: number;
+  h: number;
+  /** Downscale ratio: energyDim / sourceDim (≈ em.w / sourceCols) */
+  scale: number;
+  /** Optional 0/1 mask at energy resolution; 0 = blocked for pathfinding */
+  traversable?: Uint8Array;
+};
+
+/** Seg-resolution wall mask used to constrain lasso vertices. */
+export type WallMaskSample = {
+  labels: Uint8Array;
+  baseboardBinary: Uint8Array;
+  cols: number;
+  rows: number;
+  wallSemanticIdx: number;
+};
+
+/** True when norm coords fall on a wall semantic pixel (excludes baseboard). */
+export function isNormPointOnWallMask(
+  normX: number,
+  normY: number,
+  mask: WallMaskSample,
+): boolean {
+  const { labels, baseboardBinary, cols, rows, wallSemanticIdx } = mask;
+  if (wallSemanticIdx < 0 || cols <= 0 || rows <= 0) {
+    return false;
+  }
+  const cx = Math.min(cols - 1, Math.max(0, Math.floor(normX * cols)));
+  const cy = Math.min(rows - 1, Math.max(0, Math.floor(normY * rows)));
+  const i = cy * cols + cx;
+  if (baseboardBinary[i]) {
+    return false;
+  }
+  return labels[i] === wallSemanticIdx;
+}
+
+export function filterVerticesToWallMask<T extends { x: number; y: number }>(
+  vertices: T[],
+  mask: WallMaskSample,
+): T[] {
+  return vertices.filter(v => isNormPointOnWallMask(v.x, v.y, mask));
+}
+
+function isWallPixel(mask: WallMaskSample, x: number, y: number): boolean {
+  const { labels, baseboardBinary, cols, rows, wallSemanticIdx } = mask;
+  if (x < 0 || y < 0 || x >= cols || y >= rows || wallSemanticIdx < 0) {
+    return false;
+  }
+  const i = y * cols + x;
+  if (baseboardBinary[i]) {
+    return false;
+  }
+  return labels[i] === wallSemanticIdx;
+}
+
+function isWallBoundaryPixel(mask: WallMaskSample, x: number, y: number): boolean {
+  if (!isWallPixel(mask, x, y)) {
+    return false;
+  }
+  const { cols, rows } = mask;
+  if (x === 0 || y === 0 || x === cols - 1 || y === rows - 1) {
+    return true;
+  }
+  return (
+    !isWallPixel(mask, x - 1, y) ||
+    !isWallPixel(mask, x + 1, y) ||
+    !isWallPixel(mask, x, y - 1) ||
+    !isWallPixel(mask, x, y + 1)
+  );
+}
+
+function isWallCornerBoundaryPixel(
+  mask: WallMaskSample,
+  x: number,
+  y: number,
+): boolean {
+  if (!isWallBoundaryPixel(mask, x, y)) {
+    return false;
+  }
+  const left = !isWallPixel(mask, x - 1, y);
+  const right = !isWallPixel(mask, x + 1, y);
+  const up = !isWallPixel(mask, x, y - 1);
+  const down = !isWallPixel(mask, x, y + 1);
+  return (left || right) && (up || down);
+}
+
+/**
+ * Snap a normalized point to the nearest wall-mask boundary pixel when the
+ * touch falls within `snapRadiusSegPx` (segmentation resolution) of the edge.
+ */
+export function snapNormPointToWallEdge(
+  normX: number,
+  normY: number,
+  mask: WallMaskSample,
+  snapRadiusSegPx = 12,
+): { x: number; y: number } {
+  const snapped = searchWallSnapTarget(
+    normX, normY, mask, snapRadiusSegPx, 'edge',
+  );
+  return snapped ?? { x: normX, y: normY };
+}
+
+/**
+ * Prefer wall-mask corner pixels (L-shaped outer boundary), then plain edge.
+ * Used when the user taps without dragging.
+ */
+export function snapNormPointToWallCornerOrEdge(
+  normX: number,
+  normY: number,
+  mask: WallMaskSample,
+  snapRadiusSegPx = 16,
+): { x: number; y: number } {
+  const corner = searchWallSnapTarget(
+    normX, normY, mask, snapRadiusSegPx, 'corner',
+  );
+  if (corner) {
+    return corner;
+  }
+  const edge = searchWallSnapTarget(
+    normX, normY, mask, snapRadiusSegPx, 'edge',
+  );
+  return edge ?? { x: normX, y: normY };
+}
+
+/**
+ * During vertex drag: snap to corner/edge when near, otherwise keep interior
+ * wall points so the anchor can move freely on the wall mask.
+ */
+export function resolveLassoWallDragPoint(
+  normX: number,
+  normY: number,
+  mask: WallMaskSample,
+  snapRadiusSegPx = 12,
+): { x: number; y: number } | null {
+  const snapped = snapNormPointToWallCornerOrEdge(
+    normX, normY, mask, snapRadiusSegPx,
+  );
+  if (isNormPointOnWallMask(snapped.x, snapped.y, mask)) {
+    return snapped;
+  }
+  if (isNormPointOnWallMask(normX, normY, mask)) {
+    return { x: normX, y: normY };
+  }
+  return null;
+}
+
+function searchWallSnapTarget(
+  normX: number,
+  normY: number,
+  mask: WallMaskSample,
+  snapRadiusSegPx: number,
+  mode: 'corner' | 'edge',
+): { x: number; y: number } | null {
+  const { cols, rows } = mask;
+  if (cols <= 0 || rows <= 0) {
+    return null;
+  }
+
+  const px = normX * cols;
+  const py = normY * rows;
+  const cx = Math.floor(px);
+  const cy = Math.floor(py);
+  const radius = Math.max(1, Math.ceil(snapRadiusSegPx));
+  const radiusSq = snapRadiusSegPx * snapRadiusSegPx;
+
+  let bestDistSq = Infinity;
+  let bestX = -1;
+  let bestY = -1;
+
+  for (let dy = -radius; dy <= radius; dy++) {
+    for (let dx = -radius; dx <= radius; dx++) {
+      const x = cx + dx;
+      const y = cy + dy;
+      if (x < 0 || y < 0 || x >= cols || y >= rows) {
+        continue;
+      }
+      const onEdge = isWallBoundaryPixel(mask, x, y);
+      if (!onEdge) {
+        continue;
+      }
+      if (mode === 'corner' && !isWallCornerBoundaryPixel(mask, x, y)) {
+        continue;
+      }
+      const distSq = (px - (x + 0.5)) ** 2 + (py - (y + 0.5)) ** 2;
+      if (distSq <= radiusSq && distSq < bestDistSq) {
+        bestDistSq = distSq;
+        bestX = x;
+        bestY = y;
+      }
+    }
+  }
+
+  if (bestX < 0) {
+    return null;
+  }
+
+  return {
+    x: (bestX + 0.5) / cols,
+    y: (bestY + 0.5) / rows,
+  };
+}
+
+export function buildWallAllowedMask(
+  labels: Uint8Array,
+  baseboardBinary: Uint8Array,
+  wallSemanticIdx: number,
+): Uint8Array | null {
+  if (wallSemanticIdx < 0) {
+    return null;
+  }
+  const allowedMask = new Uint8Array(labels.length);
+  for (let i = 0; i < labels.length; i++) {
+    allowedMask[i] =
+      labels[i] === wallSemanticIdx && !baseboardBinary[i] ? 1 : 0;
+  }
+  return allowedMask;
+}
+
+/* ==========================================================================
+ * buildEnergyMap
+ * ========================================================================== */
+
+const GRAY_R = 0.299;
+const GRAY_G = 0.587;
+const GRAY_B = 0.114;
+
+/**
+ * Build per-pixel energy map from BGR buffer.
+ * 1. Convert to grayscale via luminance weights
+ * 2. Downsample so longest side ≤ targetMaxSide
+ * 3. Apply Sobel 3×3 → gradient magnitude G
+ * 4. Energy = 1 / (1 + G), clamped to [0, 1]
+ */
+export function buildEnergyMap(
+  bgrBuffer: Uint8Array,
+  cols: number,
+  rows: number,
+  targetMaxSide = 256,
+  allowedMask?: Uint8Array | null,
+): EnergyMap {
+  const imgLongSide = Math.max(cols, rows);
+  const scale = imgLongSide > targetMaxSide ? targetMaxSide / imgLongSide : 1;
+  const ew = Math.max(1, Math.floor(cols * scale));
+  const eh = Math.max(1, Math.floor(rows * scale));
+  const pixelCount = ew * eh;
+
+  // 1. Build grayscale at target resolution (nearest-neighbour downsample)
+  const gray = new Float32Array(pixelCount);
+  for (let gy = 0; gy < eh; gy++) {
+    const sy = Math.min(rows - 1, Math.floor((gy * rows) / eh));
+    const rowBase = sy * cols;
+    for (let gx = 0; gx < ew; gx++) {
+      const sx = Math.min(cols - 1, Math.floor((gx * cols) / ew));
+      const i = rowBase + sx;
+      const o = (i) * 3;
+      const val =
+        GRAY_R * bgrBuffer[o + 2] +
+        GRAY_G * bgrBuffer[o + 1] +
+        GRAY_B * bgrBuffer[o];
+      gray[gy * ew + gx] = val;
+    }
+  }
+
+  // 2. Sobel 3×3 → gradient magnitude
+  //   X: [-1 0 1; -2 0 2; -1 0 1]
+  //   Y: [-1 -2 -1; 0 0 0; 1 2 1]
+  const grad = new Float32Array(pixelCount);
+  let maxG = 1; // avoid division by zero
+
+  for (let gy = 1; gy < eh - 1; gy++) {
+    for (let gx = 1; gx < ew - 1; gx++) {
+      const idx = gy * ew + gx;
+      const a = gray[(gy - 1) * ew + (gx - 1)];
+      const b = gray[(gy - 1) * ew + gx];
+      const c = gray[(gy - 1) * ew + (gx + 1)];
+      const d = gray[gy * ew + (gx - 1)];
+      const e = gray[gy * ew + gx + 1];
+      const f = gray[(gy + 1) * ew + (gx - 1)];
+      const gv = gray[(gy + 1) * ew + gx];
+      const h = gray[(gy + 1) * ew + (gx + 1)];
+
+      const gxVal = -a + c - 2 * d + 2 * e - f + h;
+      const gyVal = -a - 2 * b - c + f + 2 * gv + h;
+      const mag = Math.sqrt(gxVal * gxVal + gyVal * gyVal);
+      grad[idx] = mag;
+      if (mag > maxG) maxG = mag;
+    }
+  }
+
+  // Boost wall-mask boundary so paths hug the semantic wall edge, not just texture.
+  if (allowedMask && allowedMask.length === cols * rows) {
+    for (let gy = 0; gy < eh; gy++) {
+      for (let gx = 0; gx < ew; gx++) {
+        const idx = gy * ew + gx;
+        const sx = Math.min(cols - 1, Math.floor((gx * cols) / ew));
+        const sy = Math.min(rows - 1, Math.floor((gy * rows) / eh));
+        if (!allowedMask[sy * cols + sx]) continue;
+
+        let onBoundary = sx === 0 || sy === 0 || sx === cols - 1 || sy === rows - 1;
+        if (!onBoundary) {
+          const n1 = allowedMask[sy * cols + (sx - 1)];
+          const n2 = allowedMask[sy * cols + (sx + 1)];
+          const n3 = allowedMask[(sy - 1) * cols + sx];
+          const n4 = allowedMask[(sy + 1) * cols + sx];
+          onBoundary = n1 === 0 || n2 === 0 || n3 === 0 || n4 === 0;
+        }
+        if (onBoundary) {
+          grad[idx] = maxG;
+        }
+      }
+    }
+  }
+
+  // 3. Energy = 1 / (1 + normalized_gradient); amplify contrast so edges win over interior shortcuts.
+  const energy = new Float32Array(pixelCount);
+  const traversable =
+    allowedMask && allowedMask.length === cols * rows
+      ? new Uint8Array(pixelCount)
+      : undefined;
+
+  for (let gy = 0; gy < eh; gy++) {
+    for (let gx = 0; gx < ew; gx++) {
+      const idx = gy * ew + gx;
+      const sx = Math.min(cols - 1, Math.floor((gx * cols) / ew));
+      const sy = Math.min(rows - 1, Math.floor((gy * rows) / eh));
+      const allowed = !allowedMask || allowedMask[sy * cols + sx] > 0;
+      if (traversable) {
+        traversable[idx] = allowed ? 1 : 0;
+      }
+      energy[idx] = allowed ? 1.0 / (1.0 + 4.0 * (grad[idx] / maxG)) : 1.0;
+    }
+  }
+
+  return { map: energy, w: ew, h: eh, scale, traversable };
+}
+
+/* ==========================================================================
+ * findShortestPath — Dijkstra 8-connected
+ * ========================================================================== */
+
+/** 8-connected neighbour offsets (dx, dy) */
+const NEIGHBOURS: [number, number][] = [
+  [-1, -1], [0, -1], [1, -1],
+  [-1, 0], /*    */ [1, 0],
+  [-1, 1], [0, 1], [1, 1],
+];
+
+/** Multiply energy cost so we can use integer priority keys. */
+const COST_SCALE = 10000;
+
+/** Binary min-heap for Dijkstra priority queue. */
+class MinHeap {
+  private data: { idx: number; dist: number }[] = [];
+
+  push(idx: number, dist: number): void {
+    this.data.push({ idx, dist });
+    this.bubbleUp(this.data.length - 1);
+  }
+
+  pop(): { idx: number; dist: number } | undefined {
+    if (this.data.length === 0) return undefined;
+    const top = this.data[0];
+    const last = this.data.pop()!;
+    if (this.data.length > 0) {
+      this.data[0] = last;
+      this.bubbleDown(0);
+    }
+    return top;
+  }
+
+  get length(): number {
+    return this.data.length;
+  }
+
+  private bubbleUp(i: number): void {
+    while (i > 0) {
+      const parent = (i - 1) >> 1;
+      if (this.data[parent].dist <= this.data[i].dist) break;
+      [this.data[parent], this.data[i]] = [this.data[i], this.data[parent]];
+      i = parent;
+    }
+  }
+
+  private bubbleDown(i: number): void {
+    const n = this.data.length;
+    while (true) {
+      let smallest = i;
+      const left = 2 * i + 1;
+      const right = 2 * i + 2;
+      if (left < n && this.data[left].dist < this.data[smallest].dist) smallest = left;
+      if (right < n && this.data[right].dist < this.data[smallest].dist) smallest = right;
+      if (smallest === i) break;
+      [this.data[smallest], this.data[i]] = [this.data[i], this.data[smallest]];
+      i = smallest;
+    }
+  }
+}
+
+/** Sentry value for "not visited" */
+const DIST_INF = 0xffffffff;
+
+/**
+ * Dijkstra shortest-path on 8-connected grid.
+ * Cost at each pixel = energy[pixel] * COST_SCALE (integer).
+ * Diagonal steps cost √2 × the neighbour's energy.
+ *
+ * Returns ordered path [start, …, end] in energy-map pixel space.
+ */
+export function findShortestPath(
+  energy: Float32Array,
+  energyW: number,
+  energyH: number,
+  sx: number,
+  sy: number,
+  ex: number,
+  ey: number,
+  traversable?: Uint8Array | null,
+): { x: number; y: number }[] {
+  // Clamp to valid range
+  const clampX = (v: number) => Math.max(1, Math.min(energyW - 2, Math.round(v)));
+  const clampY = (v: number) => Math.max(1, Math.min(energyH - 2, Math.round(v)));
+
+  const startX = clampX(sx);
+  const startY = clampY(sy);
+  const endX = clampX(ex);
+  const endY = clampY(ey);
+
+  const pixelCount = energyW * energyH;
+  const startIdx = startY * energyW + startX;
+
+  // Distance array (init to infinity)
+  const dist = new Uint32Array(pixelCount);
+  dist.fill(DIST_INF);
+  dist[startIdx] = 0;
+
+  // Previous node for path reconstruction
+  const prev = new Int32Array(pixelCount);
+  prev.fill(-1);
+
+  const heap = new MinHeap();
+  heap.push(startIdx, 0);
+
+  while (heap.length > 0) {
+    const node = heap.pop()!;
+    const u = node.idx;
+    const d = node.dist;
+    if (d > dist[u]) continue;
+
+    const ux = u % energyW;
+    const uy = Math.floor(u / energyW);
+
+    if (ux === endX && uy === endY) {
+      const path: { x: number; y: number }[] = [];
+      let cur = u;
+      while (cur >= 0) {
+        path.push({ x: cur % energyW, y: Math.floor(cur / energyW) });
+        cur = prev[cur];
+      }
+      path.reverse();
+      return path;
+    }
+
+    for (const [dx, dy] of NEIGHBOURS) {
+      const nx = ux + dx;
+      const ny = uy + dy;
+      if (nx < 0 || nx >= energyW || ny < 0 || ny >= energyH) continue;
+      const v = ny * energyW + nx;
+      if (traversable && traversable[v] === 0) continue;
+
+      const isDiagonal = dx !== 0 && dy !== 0;
+      const stepCost = isDiagonal
+        ? Math.round(energy[v] * COST_SCALE * 1.4142)
+        : Math.round(energy[v] * COST_SCALE);
+
+      const alt = d + stepCost;
+      if (alt < dist[v]) {
+        dist[v] = alt;
+        prev[v] = u;
+        heap.push(v, alt);
+      }
+    }
+  }
+
+  // No path found — return straight line
+  return [{ x: startX, y: startY }, { x: endX, y: endY }];
+}
+
+/* ==========================================================================
+ * extractCornerPoints — Douglas-Peucker simplification
+ * ========================================================================== */
+
+/**
+ * Douglas-Peucker simplification. Keeps points where the perpendicular
+ * distance from the line segment exceeds epsilon.
+ *
+ * After DP, also enforces a minimum distance between consecutive anchors
+ * to avoid overly dense clusters.
+ */
+export function extractCornerPoints(
+  path: { x: number; y: number }[],
+  minDistance = 8,
+  epsilon = 2.0,
+): { x: number; y: number }[] {
+  if (path.length <= 2) return [...path];
+
+  const keep = new Uint8Array(path.length);
+  keep[0] = 1;
+  keep[path.length - 1] = 1;
+
+  function recurse(s: number, e: number) {
+    if (e - s <= 1) return;
+
+    const ax = path[s].x;
+    const ay = path[s].y;
+    const bx = path[e].x;
+    const by = path[e].y;
+    const dx = bx - ax;
+    const dy = by - ay;
+    const lenSq = dx * dx + dy * dy;
+
+    let maxDist = 0;
+    let maxIdx = s;
+
+    for (let i = s + 1; i < e; i++) {
+      let dist: number;
+      if (lenSq === 0) {
+        dist = Math.hypot(path[i].x - ax, path[i].y - ay);
+      } else {
+        const t = Math.max(0, Math.min(1,
+          ((path[i].x - ax) * dx + (path[i].y - ay) * dy) / lenSq,
+        ));
+        const px = ax + t * dx;
+        const py = ay + t * dy;
+        dist = Math.hypot(path[i].x - px, path[i].y - py);
+      }
+      if (dist > maxDist) {
+        maxDist = dist;
+        maxIdx = i;
+      }
+    }
+
+    if (maxDist > epsilon) {
+      keep[maxIdx] = 1;
+      recurse(s, maxIdx);
+      recurse(maxIdx, e);
+    }
+  }
+
+  recurse(0, path.length - 1);
+
+  // Collect kept points with minDistance filter
+  const result: { x: number; y: number }[] = [];
+  for (let i = 0; i < path.length; i++) {
+    if (!keep[i]) continue;
+    if (result.length > 0) {
+      const last = result[result.length - 1];
+      const dist = Math.hypot(path[i].x - last.x, path[i].y - last.y);
+      if (dist < minDistance) continue;
+    }
+    result.push({ x: path[i].x, y: path[i].y });
+  }
+
+  return result;
+}
+
+/* ==========================================================================
+ * upscalePath
+ * ========================================================================== */
+
+/** Map normalized image coords (0..1) to energy-map pixel coords. */
+export function normToEnergyPoint(
+  normX: number,
+  normY: number,
+  em: EnergyMap,
+): { x: number; y: number } {
+  return {
+    x: Math.min(em.w - 1, Math.max(0, normX * em.w)),
+    y: Math.min(em.h - 1, Math.max(0, normY * em.h)),
+  };
+}
+
+/** Map energy-map pixel coords back to normalized image coords. */
+export function energyPointsToNorm(
+  points: { x: number; y: number }[],
+  em: EnergyMap,
+): { x: number; y: number }[] {
+  return points.map(p => ({
+    x: Math.min(1, Math.max(0, p.x / em.w)),
+    y: Math.min(1, Math.max(0, p.y / em.h)),
+  }));
+}
+
+/** Map energy-map pixel coords back to original image coords. */
+export function upscalePath(
+  points: { x: number; y: number }[],
+  scale: number,
+  originW: number,
+  originH: number,
+): { x: number; y: number }[] {
+  return points.map(p => ({
+    x: Math.min(originW - 1, Math.max(0, Math.round(p.x / scale))),
+    y: Math.min(originH - 1, Math.max(0, Math.round(p.y / scale))),
+  }));
+}
--- a/src/utils/maskOutlinePaths.ts
+++ b/src/utils/maskOutlinePaths.ts
@ -277,7 +277,7 @@ function filterOutlineLoops(
  return candidates.filter(loop => loopBoundingArea(loop) >= minKeepArea);
 }

-function floodFillComponent(
+export function floodFillComponent(
  binary: Uint8Array,
  cols: number,
  rows: number,
--- a/src/utils/maskSegmentRuntime.ts
+++ b/src/utils/maskSegmentRuntime.ts
@ -137,6 +137,13 @@ export const DEFAULT_MASK_CONFIG: Required<
  splitWallsColorDistSq: 1400,
  splitWallsChromaBlurRadius: 5,
  splitWallsNeutralChromaMax: 14,
+  splitWallsEdgeBarrierThreshold: 160,
+  splitWallsCloseMaskRadius:4,
+  manualSplitWalls: false,
+  manualSplitWallsMaxCount: 8,
+  manualSplitWallsGapAbsorbDilatePx: 5,
+  magneticLasso: false,
+  activeContourRefine: false,
 };

 export type ResolvedMaskSegmentRuntime = {
@ -209,6 +216,24 @@ export function mergeMaskConfig(
    splitWallsNeutralChromaMax:
      partial.splitWallsNeutralChromaMax ??
      DEFAULT_MASK_CONFIG.splitWallsNeutralChromaMax,
+    splitWallsEdgeBarrierThreshold:
+      partial.splitWallsEdgeBarrierThreshold ??
+      DEFAULT_MASK_CONFIG.splitWallsEdgeBarrierThreshold,
+    splitWallsCloseMaskRadius:
+      partial.splitWallsCloseMaskRadius ??
+      DEFAULT_MASK_CONFIG.splitWallsCloseMaskRadius,
+    manualSplitWalls:
+      partial.manualSplitWalls ?? DEFAULT_MASK_CONFIG.manualSplitWalls,
+    manualSplitWallsMaxCount:
+      partial.manualSplitWallsMaxCount ??
+      DEFAULT_MASK_CONFIG.manualSplitWallsMaxCount,
+    manualSplitWallsGapAbsorbDilatePx:
+      partial.manualSplitWallsGapAbsorbDilatePx ??
+      DEFAULT_MASK_CONFIG.manualSplitWallsGapAbsorbDilatePx,
+    magneticLasso:
+      partial.magneticLasso ?? DEFAULT_MASK_CONFIG.magneticLasso,
+    activeContourRefine:
+      partial.activeContourRefine ?? DEFAULT_MASK_CONFIG.activeContourRefine,
  };
 }

--- a/src/utils/maskSegmentation.ts
+++ b/src/utils/maskSegmentation.ts
@ -414,6 +414,10 @@ export type RegionMaskData = {
  cols: number;
  rows: number;
  wallSubLabels?: Uint8Array;
+  /** Semantic index → name table captured at segmentation time (must match labels buffer). */
+  indexToName?: string[];
+  /** Wall semantic index in labels buffer (captured at segmentation time). */
+  wallSemanticIdx?: number;
 };

 /** downsample mask path building (screen display does not need segmentation resolution, click still uses full resolution pickMap) */
@ -421,7 +425,8 @@ export function downsampleMaskDataForPaths(
  maskData: RegionMaskData,
  maxLongSide: number,
 ): RegionMaskData {
-  const { labels, baseboardBinary, cols, rows, wallSubLabels } = maskData;
+  const { labels, baseboardBinary, cols, rows, wallSubLabels, indexToName, wallSemanticIdx } =
+    maskData;
  const longSide = Math.max(cols, rows);
  if (longSide <= maxLongSide) {
    return maskData;
@ -460,6 +465,8 @@ export function downsampleMaskDataForPaths(
    cols: dstCols,
    rows: dstRows,
    wallSubLabels: outWallSub,
+    indexToName,
+    wallSemanticIdx,
  };
 }

--- a/src/utils/wallTextureSplit.ts
+++ b/src/utils/wallTextureSplit.ts
@ -16,14 +16,87 @@ function maskCfg() {
  return getMaskSegmentRuntimeConfig().mask;
 }

-function bboxToPolygon(bbox: SegmentRegion['bbox']): { x: number; y: number }[] {
-  return [
-    { x: bbox.x, y: bbox.y },
-    { x: bbox.x + bbox.w, y: bbox.y },
-    { x: bbox.x + bbox.w, y: bbox.y + bbox.h },
-    { x: bbox.x, y: bbox.y + bbox.h },
-  ];
+type Point = { x: number; y: number };
+
+/** Moore-neighbor boundary tracer on a binary mask component. */
+function traceMaskPolygon(
+  mask: Uint8Array,
+  cols: number,
+  rows: number,
+): Point[] {
+  // Find first non-zero pixel (top-left)
+  let startX = -1, startY = -1;
+  for (let y = 0; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      if (mask[y * cols + x]) { startX = x; startY = y; break; }
    }
+    if (startX >= 0) break;
+  }
+  if (startX < 0) return [];
+
+  // Moore 8-neighbor clockwise trace
+  const dirs: [number, number][] = [
+    [1, 0], [1, -1], [0, -1], [-1, -1],
+    [-1, 0], [-1, 1], [0, 1], [1, 1],
+  ];
+  const path: Point[] = [];
+  let cx = startX, cy = startY;
+  let dir = 7; // start searching from up-left
+
+  for (let i = 0; i < cols * rows; i++) {
+    path.push({ x: cx, y: cy });
+    let found = false;
+    for (let j = 0; j < 8; j++) {
+      const d = (dir + 1 + j) % 8; // search clockwise from last direction+1
+      const nx = cx + dirs[d][0];
+      const ny = cy + dirs[d][1];
+      if (nx < 0 || nx >= cols || ny < 0 || ny >= rows) continue;
+      if (mask[ny * cols + nx]) {
+        cx = nx; cy = ny; dir = (d + 4) % 8; // face back toward previous pixel
+        found = true;
+        break;
+      }
+    }
+    if (!found) break;
+    if (path.length > 2 && cx === startX && cy === startY) break;
+  }
+
+  return path;
+}
+
+/** Douglas-Peucker polygon simplification (epsilon in pixels). */
+function simplifyPolygon(points: Point[], epsilon: number): Point[] {
+  if (points.length <= 2) return [...points];
+  const keep = new Uint8Array(points.length);
+  keep[0] = 1;
+  keep[points.length - 1] = 1;
+
+  const recurse = (s: number, e: number) => {
+    if (e - s <= 1) return;
+    const dx = points[e].x - points[s].x;
+    const dy = points[e].y - points[s].y;
+    const lenSq = dx * dx + dy * dy;
+    let maxDist = 0, maxIdx = s;
+    for (let i = s + 1; i < e; i++) {
+      let d: number;
+      if (lenSq === 0) {
+        d = Math.hypot(points[i].x - points[s].x, points[i].y - points[s].y);
+      } else {
+        const t = Math.max(0, Math.min(1,
+          ((points[i].x - points[s].x) * dx + (points[i].y - points[s].y) * dy) / lenSq,
+        ));
+        d = Math.hypot(points[i].x - (points[s].x + t * dx), points[i].y - (points[s].y + t * dy));
+      }
+      if (d > maxDist) { maxDist = d; maxIdx = i; }
+    }
+    if (maxDist > epsilon) { keep[maxIdx] = 1; recurse(s, maxIdx); recurse(maxIdx, e); }
+  };
+  recurse(0, points.length - 1);
+
+  return points.filter((_, i) => keep[i]);
+}
+
+const POLYGON_SIMPLIFY_EPSILON = 2.5;

 function computeLabChromaMaps(
  originBgr: Uint8Array,
@ -42,6 +115,79 @@ function computeLabChromaMaps(
  return { aMap, bMap };
 }

+/** Per-channel BGR Sobel gradient magnitude. max(B, G, R) for sensitivity to color edges. */
+function buildEdgeBarrierMask(
+  bgr: Uint8Array,
+  cols: number,
+  rows: number,
+  wallIdx: number,
+  labels: Uint8Array,
+  baseboardBinary: Uint8Array,
+  threshold: number,
+): Uint8Array {
+  const n = cols * rows;
+  const barriers = new Uint8Array(n);
+  if (threshold <= 0) return barriers;
+
+  // Per-channel Sobel 3x3 → take max raw gradient.
+  // Raw range is [0, ~1442] for 8‑bit BGR. No normalization — a single
+  // extremely strong edge (e.g. window frame) would compress all other
+  // edges if we normalized relative to maxG.
+  const C = cols;
+
+  for (let y = 1; y < rows - 1; y++) {
+    const r0 = (y - 1) * C;
+    const r1 = y * C;
+    const r2 = (y + 1) * C;
+    for (let x = 1; x < C - 1; x++) {
+      const i = r1 + x;
+      if (labels[i] !== wallIdx || baseboardBinary[i]) continue;
+
+      const a0 = r0 + (x - 1), a1 = r0 + x, a2 = r0 + (x + 1);
+      const b0 = r1 + (x - 1),             b2 = r1 + (x + 1);
+      const c0 = r2 + (x - 1), c1 = r2 + x, c2 = r2 + (x + 1);
+
+      let best = 0;
+      for (let ch = 0; ch < 3; ch++) {
+        const a = bgr[a0 * 3 + ch];
+        const b = bgr[a1 * 3 + ch];
+        const c = bgr[a2 * 3 + ch];
+        const d = bgr[b0 * 3 + ch];
+        const e = bgr[b2 * 3 + ch];
+        const f = bgr[c0 * 3 + ch];
+        const gv = bgr[c1 * 3 + ch];
+        const h = bgr[c2 * 3 + ch];
+        const gx = -a + c - 2 * d + 2 * e - f + h;
+        const gy = -a - 2 * b - c + f + 2 * gv + h;
+        const mag = Math.sqrt(gx * gx + gy * gy);
+        if (mag > best) best = mag;
+      }
+      if (best > threshold) barriers[i] = 1;
+    }
+  }
+
+  // Dilate 1px to widen the barrier slightly
+  return dilateBinary1px(barriers, cols, rows);
+}
+
+function dilateBinary1px(src: Uint8Array, cols: number, rows: number): Uint8Array {
+  const dst = new Uint8Array(src);
+  for (let y = 1; y < rows - 1; y++) {
+    const rc = y * cols;
+    for (let x = 1; x < cols - 1; x++) {
+      const i = rc + x;
+      if (src[i]) continue;
+      if (
+        src[i - 1] || src[i + 1] ||
+        src[(y - 1) * cols + x] || src[(y + 1) * cols + x]
+      ) {
+        dst[i] = 1;
+      }
+    }
+  }
+  return dst;
+}
+
 function chromaMag(a: number, b: number): number {
  const da = a - 128;
  const db = b - 128;
@ -109,6 +255,81 @@ function isWallPixel(
  return labels[i] === wallIdx;
 }

+/**
+ * Morphological close on the wall mask: dilate then erode to fill small
+ * non-wall holes (windows, doors, occlusions) that would otherwise
+ * fragment a single wall into disconnected components during BFS.
+ * Returns a temporary labels array with holes filled as wallIdx.
+ */
+function closeWallMask(
+  labels: Uint8Array,
+  baseboardBinary: Uint8Array,
+  wallIdx: number,
+  cols: number,
+  rows: number,
+  radius: number,
+): { labels: Uint8Array; baseboardBinary: Uint8Array } {
+  const n = cols * rows;
+
+  // Binary wall mask
+  const bin = new Uint8Array(n);
+  for (let i = 0; i < n; i++) {
+    if (labels[i] === wallIdx && !baseboardBinary[i]) bin[i] = 1;
+  }
+
+  // Dilate N times
+  let dilated = bin;
+  for (let pass = 0; pass < radius; pass++) {
+    dilated = dilateBinary1px(dilated, cols, rows);
+  }
+
+  // Erode N times
+  let closed = dilated;
+  for (let pass = 0; pass < radius; pass++) {
+    closed = erodeBinary1px(closed, cols, rows);
+  }
+
+  // Build closed labels: pixels that were NOT wall but are now in the closed
+  // mask get wallIdx so the BFS can cross them. Original non-wall pixels
+  // outside the wall area are unchanged.
+  const closedLabels = new Uint8Array(labels);
+  for (let i = 0; i < n; i++) {
+    if (closed[i] && labels[i] !== wallIdx && !baseboardBinary[i]) {
+      closedLabels[i] = wallIdx;
+    }
+  }
+
+  // These pixels were baseboard or other semantic — keep them excluded
+  const closedBaseboard = new Uint8Array(baseboardBinary);
+  for (let i = 0; i < n; i++) {
+    if (closed[i] && labels[i] !== wallIdx && baseboardBinary[i]) {
+      // Baseboard inside the closed area: treat as wall so it doesn't block BFS
+      closedLabels[i] = wallIdx;
+      closedBaseboard[i] = 0;
+    }
+  }
+
+  return { labels: closedLabels, baseboardBinary: closedBaseboard };
+}
+
+function erodeBinary1px(src: Uint8Array, cols: number, rows: number): Uint8Array {
+  const dst = new Uint8Array(src);
+  for (let y = 1; y < rows - 1; y++) {
+    const rc = y * cols;
+    for (let x = 1; x < cols - 1; x++) {
+      const i = rc + x;
+      if (!src[i]) continue;
+      if (
+        !src[rc + (x - 1)] || !src[rc + (x + 1)] ||
+        !src[(y - 1) * cols + x] || !src[(y + 1) * cols + x]
+      ) {
+        dst[i] = 0;
+      }
+    }
+  }
+  return dst;
+}
+
 /**
 * 4-connected component growth: compares against component chroma mean to avoid chain bridging;
 * forces separation at neutral/colored wall boundaries.
@ -119,6 +340,7 @@ function labelWallComponents(
  wallIdx: number,
  aMap: Uint8Array,
  bMap: Uint8Array,
+  barrierMask: Uint8Array,
  cols: number,
  rows: number,
  distSqThreshold: number,
@ -164,6 +386,7 @@ function labelWallComponents(
          const nx = ni % cols;
          if (Math.abs(nx - cx) > 1) continue;
          if (!isWallPixel(labels, baseboardBinary, wallIdx, ni)) continue;
+          if (barrierMask[ni]) continue;
          if (compLabels[ni] >= 0) continue;

          const na = aMap[ni];
@ -379,6 +602,25 @@ function mergeSmallComponents(
    }
  }

+  // Second pass: any component that is smaller than its most-adjacent
+  // neighbor is almost certainly a barrier artefact — merge it.
+  for (let c = 0; c < compCount; c++) {
+    if (stats[c].area <= 0) continue;
+    const neighbors = adjacency.get(c);
+    if (!neighbors || neighbors.size === 0) continue;
+    let bestNeighbor = -1;
+    let bestBorder = 0;
+    for (const [nb, border] of neighbors) {
+      if (border > bestBorder) {
+        bestBorder = border;
+        bestNeighbor = nb;
+      }
+    }
+    if (bestNeighbor < 0) continue;
+    if (stats[c].area >= stats[bestNeighbor].area) continue;
+    union(c, bestNeighbor);
+  }
+
  const pixelCount = cols * rows;
  for (let i = 0; i < pixelCount; i++) {
    const c = compLabels[i];
@ -387,6 +629,78 @@ function mergeSmallComponents(
  }
 }

+/**
+ * Fresh-adjacency pass: rebuild the adjacency graph from current labels and
+ * merge every component below minArea into its most-adjacent larger neighbor.
+ * Runs until all tiny fragments are absorbed or no more merges possible.
+ */
+function mergeFreshTinyComponents(
+  compLabels: Int32Array,
+  stats: WallComponent[],
+  cols: number,
+  rows: number,
+  minArea: number,
+): void {
+  const compCount = stats.length;
+  // Build adjacency from current labels
+  const adjacency = new Map<number, Map<number, number>>();
+  const addEdge = (a: number, b: number) => {
+    if (a === b) return;
+    let m = adjacency.get(a);
+    if (!m) { m = new Map(); adjacency.set(a, m); }
+    m.set(b, (m.get(b) ?? 0) + 1);
+  };
+  for (let y = 0; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      const i = y * cols + x;
+      const a = compLabels[i];
+      if (a < 0) continue;
+      if (x + 1 < cols) { const b = compLabels[i + 1]; if (b >= 0) addEdge(a, b); }
+      if (y + 1 < rows) { const b = compLabels[i + cols]; if (b >= 0) addEdge(a, b); }
+    }
+  }
+
+  const remap = new Int32Array(compCount);
+  for (let i = 0; i < compCount; i++) remap[i] = i;
+  const find = (x: number): number => {
+    while (remap[x] !== x) { remap[x] = remap[remap[x]]; x = remap[x]; }
+    return x;
+  };
+  const union = (a: number, b: number) => {
+    const ra = find(a), rb = find(b);
+    if (ra === rb) return;
+    if (stats[ra].area >= stats[rb].area) {
+      remap[rb] = ra; stats[ra].area += stats[rb].area; stats[rb].area = 0;
+    } else {
+      remap[ra] = rb; stats[rb].area += stats[ra].area; stats[ra].area = 0;
+    }
+  };
+
+  for (let iter = 0; iter < compCount; iter++) {
+    let changed = false;
+    for (let c = 0; c < compCount; c++) {
+      if (stats[c].area <= 0 || stats[c].area >= minArea) continue;
+      const nbrs = adjacency.get(c);
+      if (!nbrs || nbrs.size === 0) continue;
+      let bestNb = -1, bestBorder = 0;
+      for (const [nb, border] of nbrs) {
+        if (remap[nb] !== nb) continue;
+        if (border > bestBorder) { bestBorder = border; bestNb = nb; }
+      }
+      if (bestNb < 0) continue;
+      union(c, bestNb);
+      changed = true;
+    }
+    if (!changed) break;
+  }
+
+  const n = cols * rows;
+  for (let i = 0; i < n; i++) {
+    const c = compLabels[i];
+    if (c >= 0) compLabels[i] = find(c);
+  }
+}
+
 function relabelComponentsContiguous(
  compLabels: Int32Array,
  cols: number,
@ -413,7 +727,7 @@ function relabelComponentsContiguous(
  return { labels: out, compCount, stats };
 }

-function buildPickMapAfterWallSplit(
+export function buildPickMapAfterWallSplit(
  labels: Uint8Array,
  baseboardBinary: Uint8Array,
  wallIdx: number,
@ -437,12 +751,15 @@ function buildPickMapAfterWallSplit(
      continue;
    }

-    if (labels[i] === wallIdx && wallSubLabels[i] !== WALL_SUB_LABEL_NONE) {
+    if (wallIdx >= 0 && labels[i] === wallIdx) {
+      if (wallSubLabels[i] !== WALL_SUB_LABEL_NONE) {
        const wallName = `wall-${wallSubLabels[i] + 1}`;
        const regionId = nameToId.get(wallName);
        if (regionId !== undefined) {
          pick[i] = regionId + 1;
        }
+      }
+      // Unpartitioned wall pixels stay 0 (no parent "wall" region after manual split).
      continue;
    }

@ -459,7 +776,50 @@ function buildPickMapAfterWallSplit(
  return pick;
 }

-function dilatePickBuffer1px(
+/**
+ * Manual lasso split: copy the existing pick map and rewrite wall pixels only.
+ * Non-wall pick codes stay identical so prior paints and hit-testing remain stable.
+ */
+export function patchPickMapForManualWallSplit(
+  existingPick: Uint8Array,
+  labels: Uint8Array,
+  baseboardBinary: Uint8Array,
+  wallIdx: number,
+  wallSubLabels: Uint8Array,
+  nameToId: Map<string, number>,
+  cols: number,
+  rows: number,
+): Uint8Array {
+  const pixelCount = cols * rows;
+  const pick = new Uint8Array(existingPick);
+
+  if (wallIdx < 0) {
+    return pick;
+  }
+
+  for (let i = 0; i < pixelCount; i++) {
+    if (baseboardBinary[i]) {
+      continue;
+    }
+    if (labels[i] !== wallIdx) {
+      continue;
+    }
+
+    const sub = wallSubLabels[i];
+    if (sub === WALL_SUB_LABEL_NONE) {
+      pick[i] = 0;
+      continue;
+    }
+
+    const wallName = `wall-${sub + 1}`;
+    const regionId = nameToId.get(wallName);
+    pick[i] = regionId !== undefined ? regionId + 1 : 0;
+  }
+
+  return pick;
+}
+
+export function dilatePickBuffer1px(
  pick: Uint8Array,
  cols: number,
  rows: number,
@ -505,6 +865,130 @@ function dilatePickBuffer1px(
  return dst;
 }

+const GAP_ABSORB_NEIGHBOURS: [number, number][] = [
+  [-1, -1], [0, -1], [1, -1],
+  [-1, 0], /*    */ [1, 0],
+  [-1, 1], [0, 1], [1, 1],
+];
+
+export type LassoPolyBBox = { x: number; y: number; w: number; h: number };
+
+function expandLassoPolyBBox(b: LassoPolyBBox, x: number, y: number): void {
+  if (b.w === 0 && b.h === 0) {
+    b.x = x;
+    b.y = y;
+    b.w = 1;
+    b.h = 1;
+    return;
+  }
+  const right = b.x + b.w;
+  const bottom = b.y + b.h;
+  if (x < b.x) {
+    b.w = right - x;
+    b.x = x;
+  } else if (x + 1 > right) {
+    b.w = x + 1 - b.x;
+  }
+  if (y < b.y) {
+    b.h = bottom - y;
+    b.y = y;
+  } else if (y + 1 > bottom) {
+    b.h = y + 1 - b.y;
+  }
+}
+
+function recomputeLassoPolyStats(
+  polyLabels: Uint8Array,
+  polyCount: number,
+  cols: number,
+  rows: number,
+  areas: number[],
+  bboxes: LassoPolyBBox[],
+): void {
+  areas.fill(0);
+  for (let pi = 0; pi < polyCount; pi++) {
+    bboxes[pi] = { x: cols, y: rows, w: 0, h: 0 };
+  }
+
+  for (let y = 0; y < rows; y++) {
+    for (let x = 0; x < cols; x++) {
+      const i = y * cols + x;
+      const pi = polyLabels[i];
+      if (pi === WALL_SUB_LABEL_NONE || pi >= polyCount) {
+        continue;
+      }
+      areas[pi]++;
+      expandLassoPolyBBox(bboxes[pi], x, y);
+    }
+  }
+}
+
+/**
+ * Morphologically dilate each lasso polygon into adjacent unassigned wall pixels
+ * (up to `dilateRadius` seg pixels) so thin gaps against the wall mask merge in.
+ */
+export function absorbSmallWallGapsForLassoPolygons(
+  polyLabels: Uint8Array,
+  polyCount: number,
+  areas: number[],
+  bboxes: LassoPolyBBox[],
+  labels: Uint8Array,
+  baseboardBinary: Uint8Array,
+  wallSemanticIdx: number,
+  priorAssignedLabels: Uint8Array,
+  cols: number,
+  rows: number,
+  dilateRadius: number,
+): void {
+  if (
+    polyCount <= 0 ||
+    dilateRadius <= 0 ||
+    wallSemanticIdx < 0
+  ) {
+    return;
+  }
+
+  const isExpandable = (i: number): boolean => {
+    if (labels[i] !== wallSemanticIdx) return false;
+    if (baseboardBinary[i]) return false;
+    if (priorAssignedLabels[i] !== WALL_SUB_LABEL_NONE) return false;
+    return polyLabels[i] === WALL_SUB_LABEL_NONE;
+  };
+
+  for (let polyIdx = 0; polyIdx < polyCount; polyIdx++) {
+    for (let pass = 0; pass < dilateRadius; pass++) {
+      const toAdd: number[] = [];
+
+      for (let y = 0; y < rows; y++) {
+        for (let x = 0; x < cols; x++) {
+          const i = y * cols + x;
+          if (polyLabels[i] !== polyIdx) continue;
+
+          for (const [dx, dy] of GAP_ABSORB_NEIGHBOURS) {
+            const nx = x + dx;
+            const ny = y + dy;
+            if (nx < 0 || nx >= cols || ny < 0 || ny >= rows) continue;
+            const ni = ny * cols + nx;
+            if (isExpandable(ni)) {
+              toAdd.push(ni);
+            }
+          }
+        }
+      }
+
+      if (toAdd.length === 0) {
+        break;
+      }
+
+      for (const ni of toAdd) {
+        polyLabels[ni] = polyIdx;
+      }
+    }
+  }
+
+  recomputeLassoPolyStats(polyLabels, polyCount, cols, rows, areas, bboxes);
+}
+
 /**
 * After semantic segmentation, subdivide the wall region into wall-1, wall-2… by source image texture features
 */
@ -536,7 +1020,20 @@ export function splitWallRegionsByTexture(
    return result;
  }

+  // Close small mask holes so non-wall pixels (windows, doors) don't
+  // fragment a single wall into disconnected BFS components.
+  const closeRadius = cfg.splitWallsCloseMaskRadius ?? 3;
+  const closed = closeRadius > 0
+    ? closeWallMask(labels, baseboardBinary, wallIdx, cols, rows, closeRadius)
+    : { labels, baseboardBinary };
+  const bfsLabels = closed.labels;
+  const bfsBaseboard = closed.baseboardBinary;
+
  const { aMap: rawA, bMap: rawB } = computeLabChromaMaps(originBgr, cols, rows);
+  const barrierMask = buildEdgeBarrierMask(
+    originBgr, cols, rows, wallIdx, bfsLabels, bfsBaseboard,
+    cfg.splitWallsEdgeBarrierThreshold ?? 36,
+  );
  const distSqThreshold = cfg.splitWallsColorDistSq;
  const neutralChromaMax = cfg.splitWallsNeutralChromaMax;
  const minAreaFloor = Math.max(
@ -545,11 +1042,12 @@ export function splitWallRegionsByTexture(
  );

  const { compLabels: rawCompLabels, compCount: rawCount } = labelWallComponents(
-    labels,
-    baseboardBinary,
+    bfsLabels,
+    bfsBaseboard,
    wallIdx,
    rawA,
    rawB,
+    barrierMask,
    cols,
    rows,
    distSqThreshold,
@ -573,8 +1071,18 @@ export function splitWallRegionsByTexture(
    neutralChromaMax,
  );

-  const { labels: finalCompLabels, compCount, stats: finalStats } =
-    relabelComponentsContiguous(rawCompLabels, cols, rows);
+  let finalCompLabels: Int32Array;
+  let compCount: number;
+  let finalStats: WallComponent[];
+
+  {
+    const relabeled = relabelComponentsContiguous(rawCompLabels, cols, rows);
+    mergeFreshTinyComponents(relabeled.labels, relabeled.stats, cols, rows, minAreaFloor);
+    const final = relabelComponentsContiguous(relabeled.labels, cols, rows);
+    finalCompLabels = final.labels;
+    compCount = final.compCount;
+    finalStats = final.stats;
+  }

  if (compCount === 0) {
    return result;
@ -607,18 +1115,37 @@ export function splitWallRegionsByTexture(
  const wallHex = wallRef?.hex ?? wallRegion.hex;
  const wallColor = wallRef?.bgr ?? wallRegion.color;

+  // Build per-component binary masks and trace simplified polygons
+  const compMasks = new Array<Uint8Array>(ranked.length);
+  for (let i = 0; i < pixelCount; i++) {
+    const c = finalCompLabels[i];
+    if (c < 0) continue;
+    const rank = rankMap.get(c);
+    if (rank === undefined) continue;
+    if (!compMasks[rank]) compMasks[rank] = new Uint8Array(pixelCount);
+    compMasks[rank][i] = 1;
+  }
+
  const nonWallRegions = regions.filter(reg => reg.name !== 'wall');
  const wallSubRegions: SegmentRegion[] = ranked.map((s, rank) => {
-    const bbox = s.bbox;
-    const poly = bboxToPolygon(bbox);
+    const mask = compMasks[rank];
+    const rawPoly = mask ? traceMaskPolygon(mask, cols, rows) : [];
+    const poly = simplifyPolygon(rawPoly, POLYGON_SIMPLIFY_EPSILON);
+    // Fallback to bbox if contour tracing failed
+    const fallback = poly.length >= 3 ? poly : [
+      { x: s.bbox.x, y: s.bbox.y },
+      { x: s.bbox.x + s.bbox.w, y: s.bbox.y },
+      { x: s.bbox.x + s.bbox.w, y: s.bbox.y + s.bbox.h },
+      { x: s.bbox.x, y: s.bbox.y + s.bbox.h },
+    ];
    return {
      id: 0,
      name: `wall-${rank + 1}`,
      hex: wallHex,
      color: { ...wallColor },
-      polygons: [poly],
-      outlinePolygons: [poly],
-      bbox,
+      polygons: [fallback],
+      outlinePolygons: [fallback],
+      bbox: s.bbox,
      area: s.area,
    };
  });
				`@ -0,0 +1 @@`
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