diff --git a/src/lib/canvas-core/document.ts b/src/lib/canvas-core/document.ts
index 38e0973..c4d19b6 100644
--- a/src/lib/canvas-core/document.ts
+++ b/src/lib/canvas-core/document.ts
@@ -1,3 +1,8 @@
+/**
+ * 规范化文档与条件变化：canvases/elements/tombstones 是按 ID 查找的只读表。
+ * 这里负责记录/树/连线校验、私有副本上的修改、条件回放与反向变化；不拥有 history、
+ * 网络或公开订阅。applyChanges 只生成候选文档，最终合法性与统一发布由调用方完成。
+ */
 import {detachElementData,hasOwnedElementData,componentDataValid} from './element-data.ts';
 import type { CanvasRecord, Change, Document, ElementRecord, Geometry, Id, Registry, Target } from './types.ts';
 import { clone, equal, fault, freeze, readMap, validJson } from './values.ts';
@@ -5,24 +10,31 @@ import { clone, equal, fault, freeze, readMap, validJson } from './values.ts';
 // This owns only the envelope and fixed table membership, not validation or
 // immutability of values inherited by applyChanges from an external document.
 const factoryDocuments=new WeakSet<object>();
+/** 冻结最外层文档并标记工厂来源；该标记只证明 envelope 来源，不代替数据校验。 */
 function documentEnvelope(document:Document):Document{const value=Object.freeze(document);factoryDocuments.add(value);return value;}
+/** 查询工厂来源，供调用方选择可信结构路径；不能据此信任所有外来字段。 */
 export const isFactoryDocument=(document:Document)=>factoryDocuments.has(document);
 
+/** 捕获输入记录、拒绝同一表内重复 ID，并脱离调用者的可变数据。
+ * 不在此处验证整棵树或所有跨记录引用；完整发布前仍需 validateDocument。 */
 export function createDocument(projectId: Id, canvases: readonly CanvasRecord[], elements: readonly ElementRecord[] = [], tombstones: ReadonlyMap<Id, number> = new Map()): Document {
   for (const element of elements) { const id = element.id; if (!staticElementProofs.has(element)&&!validJson(element)) throw fault('invalid_element', [id]); }
   for (const canvas of canvases) if (!validJson(canvas)) throw fault('invalid_canvas');
   if (!projectId || new Set(canvases.map(item => item.id)).size !== canvases.length || new Set(elements.map(item => item.id)).size !== elements.length) throw fault('duplicate_identity');
   return documentEnvelope({ projectId, canvases: readMap(new Map(canvases.map(item => [item.id, freeze(clone(item))]))), elements: readMap(new Map(elements.map(item => [item.id, detachElementData(item)]))), tombstones: readMap(tombstones) });
 }
+/** 节点几何必须有限、宽高为正且旋转在 [0,360)；不把无效值静默修正。 */
 export function geometryValid(value: Geometry): boolean {
   return !!value && typeof value === 'object' && [value.x, value.y, value.width, value.height, value.rotation].every(Number.isFinite) && value.width > 0 && value.height > 0 && value.rotation >= 0 && value.rotation < 360;
 }
+/** 通过 ID+incarnation 定位活元素，阻止旧手势/异步回调命中删除后重建的同 ID 对象。 */
 export function targetElement(document: Document, target: Target): ElementRecord {
   const element = document.elements.get(target.id);
   if (!element) throw fault('element_missing', [target.id]);
   if (element.incarnation !== target.incarnation) throw fault('stale_incarnation', [target.id]);
   return element;
 }
+/** 从当前 canvas 向根收集路径（包含自身）；Set 检测循环，缺失父项明确报告未加载。 */
 export function ancestors(document: Document, canvasId: Id): Id[] {
   const result: Id[] = [], visited = new Set<Id>();
   let next: Id | undefined = canvasId;
@@ -35,6 +47,7 @@ export function ancestors(document: Document, canvasId: Id): Id[] {
   }
   return result;
 }
+/** 找最近共同上级：先收集左路径，再从右侧逐级向上找首次交点。用于确定连线 owner。 */
 export function commonCanvas(document: Document, left: Id, right: Id): Id {
   const parents = new Set(ancestors(document, left));
   const result = ancestors(document, right).find(id => parents.has(id));
@@ -45,6 +58,8 @@ export function commonCanvas(document: Document, left: Id, right: Id): Id {
 const staticElementProofs=new WeakSet<object>();
 /** Validate one record before its graph dependencies have arrived. This does not
  * prove owner membership, endpoint existence or connection common ownership. */
+/** 校验单条记录的基础形状、墓碑代次和已知组件数据。
+ * staticElementProofs 仅缓存已捕获记录的固有形状；墓碑和 registry 相关检查每次仍执行。 */
 export function validateElementRecord(element: ElementRecord, registry: Registry, tombstones: ReadonlyMap<Id,number> = new Map(), componentData = true): void {
   const proven=!!element&&staticElementProofs.has(element);
   if (!proven&&(!element || !validJson(element) || typeof element.id !== 'string' || !element.id || typeof element.ownerCanvasId !== 'string' || !element.ownerCanvasId || typeof element.componentId !== 'string' || !element.componentId || !['node','connection'].includes(element.structure) || !Number.isSafeInteger(element.incarnation) || element.incarnation < 1 || !Number.isSafeInteger(element.dataVersion) || element.dataVersion < 1 || !element.data || typeof element.data !== 'object' || Array.isArray(element.data) || !validJson(element.data))) throw fault('invalid_element', [element?.id]);
@@ -57,9 +72,12 @@ export function validateElementRecord(element: ElementRecord, registry: Registry
   if(hasOwnedElementData(element))staticElementProofs.add(element);
 }
 
+/** 墓碑保存已死亡的最大 incarnation，必须是非空 ID 对应的正安全整数。 */
 function validateTombstone(id:Id,incarnation:number){
   if(!id||!Number.isSafeInteger(incarnation)||incarnation<1)throw fault('invalid_tombstone',[id]);
 }
+/** 校验父链与入口：入口是父 canvas 的节点，且不能被多个子 canvas 共用。
+ * 返回 1 表示根，供整文档校验要求恰好一个根。 */
 function validateCanvasInDocument(document:Document,canvas:CanvasRecord,entries:Set<Id>):number{
   if(typeof canvas.id!=='string'||!canvas.id||!Object.hasOwn(canvas,'parent')||canvas.parent!==null&&(!canvas.parent||typeof canvas.parent.canvasId!=='string'||typeof canvas.parent.entryElementId!=='string'))throw fault('invalid_canvas');
   ancestors(document,canvas.id);
@@ -68,6 +86,7 @@ function validateCanvasInDocument(document:Document,canvas:CanvasRecord,entries:
   if(!entry||entry.structure!=='node'||entry.ownerCanvasId!==canvas.parent.canvasId||entries.has(entry.id))throw fault('invalid_canvas_entry',[canvas.id]);
   entries.add(entry.id);return 0;
 }
+/** 在单记录校验之上检查 owner、真实端点及最近共同上级；只允许节点作为边端点。 */
 function validateElementInDocument(document:Document,element:ElementRecord,registry:Registry,componentData:boolean){
   validateElementRecord(element,registry,document.tombstones,componentData);
   if(!document.canvases.has(element.ownerCanvasId))throw fault('invalid_element',[element.id]);
@@ -78,6 +97,7 @@ function validateElementInDocument(document:Document,element:ElementRecord,regis
   }
 }
 /** Cooperative and synchronous paths use the same per-record checks and order. */
+/** 每项检查前 yield，让异步调度调用方可以分片；迭代器本身不等待或调度。 */
 function* validateDocumentChecks(document:Document,registry:Registry,componentData:boolean):Generator<void,void>{
   if(!document.canvases.size)throw fault('missing_root');
   for(const[id,incarnation]of document.tombstones){yield;validateTombstone(id,incarnation);}
@@ -87,8 +107,11 @@ function* validateDocumentChecks(document:Document,registry:Registry,componentDa
   for(const element of document.elements.values()){yield;validateElementInDocument(document,element,registry,componentData);}
 }
 /** Structural indexes contain no component payload; use only for source planning, never editor publication. */
+/** 仅结构检查的分片迭代器：跳过组件 payload schema，供源结构规划使用。 */
 export function* validateDocumentTopologySteps(document:Document,registry:Registry):Generator<void,void>{yield* validateDocumentChecks(document,registry,false);}
+/** 含组件 payload 的完整分片校验；必须迭代到结束才证明整份文档通过。 */
 export function* validateDocumentSteps(document:Document,registry:Registry):Generator<void,void>{yield* validateDocumentChecks(document,registry,true);}
+/** 同步完整校验，要求恰好一个根，所有拥有关系、端点和组件数据均合法。 */
 export function validateDocument(document:Document,registry:Registry):void{
   if(!document.canvases.size)throw fault('missing_root');
   for(const[id,incarnation]of document.tombstones)validateTombstone(id,incarnation);
@@ -97,15 +120,21 @@ export function validateDocument(document:Document,registry:Registry):void{
   if(roots!==1)throw fault('invalid_roots');
   for(const element of document.elements.values())validateElementInDocument(document,element,registry,true);
 }
+/** 一批有序修改及其允许的 canvas 上下文；回放不能跨越已冻结的操作范围。 */
 export type ReplayChangeBatch = {readonly changes:readonly Change[];readonly canvasIds?:readonly Id[]};
+/** 在私有表副本中应用一批变化；默认校验 before 条件，失败不会修改输入文档。 */
 export function applyChanges(document: Document, changes: readonly Change[], conditional = true): Document {
   return applyChangeBatches(document,[{changes}],conditional,false);
 }
 /** Ordered conditional replay against one private draft; no intermediate document escapes. */
+/** 顺序回放多批变化，已经满足的 after 可跳过，但仍检查目标的 scope。 */
 export function replayChanges(document:Document,batches:Iterable<ReplayChangeBatch>):Document {
   return applyChangeBatches(document,batches,true,true);
 }
+/** 三类变化共用的执行器：field 改字段、element 增删元素、canvas 改树记录。
+ * 仅在全部循环成功后返回冻结 envelope，不泄漏半成品；此处不做整图合法性校验。 */
 function applyChangeBatches(document:Document,batches:Iterable<ReplayChangeBatch>,conditional:boolean,replay:boolean):Document {
+  // 复制表成员而复用未改记录；出错时丢弃这些私有 Map，输入快照保持不变。
   const elements = new Map(document.elements), canvases = new Map(document.canvases), tombstones = new Map(document.tombstones);
   for (const batch of batches) for (const change of batch.changes) {
     if(replay){
@@ -113,11 +142,13 @@ function applyChangeBatches(document:Document,batches:Iterable<ReplayChangeBatch
       if(change.kind==='field'){const owner=elements.get(change.target.id)?.ownerCanvasId;if(owner&&batch.canvasIds?.length&&!batch.canvasIds.includes(owner))throw fault('operation_context_changed',[change.target.id]);}
       if(changeSatisfied(elements,canvases,change))continue;
     }
+    // 字段级条件检查同时比较值与“字段是否存在”，区分缺失和显式 null。
     if (change.kind === 'field') {
       if (!validJson(change.after)) throw fault('invalid_change');
       if (!change.field.startsWith('data.') && !['geometry', 'ownerCanvasId', 'source', 'target', 'path'].includes(change.field)) throw fault('invalid_field');
       const element = elements.get(change.target.id);
       if (!element || element.incarnation !== change.target.incarnation) throw fault('stale_incarnation', [change.target.id]);
+      // data. 后面的部分是一个顶层数据键，不在这里按点路径递归写嵌套对象。
       const dataKey = change.field.startsWith('data.') ? change.field.slice(5) : null;
       const prior = dataKey !== null ? element.data[dataKey] ?? null : (element as unknown as Record<string, unknown>)[change.field];
       if (conditional && (dataKey !== null && Object.hasOwn(element.data, dataKey) !== (change.beforePresent ?? true) || !equal(prior, change.before))) throw fault('field_conflict', [element.id]);
@@ -127,6 +158,7 @@ function applyChangeBatches(document:Document,batches:Iterable<ReplayChangeBatch
         if (change.afterPresent === false) delete data[dataKey]; else data[dataKey] = clone(change.after);
         elements.set(element.id, freeze({ ...element, data }));
       } else elements.set(element.id, freeze({ ...element, [change.field]: clone(change.after) }) as ElementRecord);
+    // 整元素修改必须匹配 before；删除同时保留墓碑，使旧 incarnation 永远不能复活。
     } else if (change.kind === 'element') {
       if (conditional && !equal(elements.get(change.id) || null, change.before)) throw fault('element_conflict', [change.id]);
       if (change.after) {
@@ -138,6 +170,7 @@ function applyChangeBatches(document:Document,batches:Iterable<ReplayChangeBatch
         if (old) tombstones.set(change.id, Math.max(tombstones.get(change.id) || 0, old.incarnation));
         elements.delete(change.id);
       }
+    // canvas 删除只移除该记录；子树/连线清理由 structure 规划器显式生成，避免隐藏副作用。
     } else if (change.kind === 'canvas') {
       if (conditional && !equal(canvases.get(change.id) || null, change.before)) throw fault('canvas_conflict', [change.id]);
       if (change.after) {
@@ -149,6 +182,7 @@ function applyChangeBatches(document:Document,batches:Iterable<ReplayChangeBatch
   }
   return documentEnvelope({ projectId: document.projectId, elements: readMap(elements), canvases: readMap(canvases), tombstones: readMap(tombstones) });
 }
+/** 检测回放目标效果是否已经存在；字段目标必须仍是同一个 incarnation 才可视为满足。 */
 function changeSatisfied(elements:ReadonlyMap<Id,ElementRecord>,canvases:ReadonlyMap<Id,CanvasRecord>,change:Change):boolean {
   if(change.kind==='canvas')return equal(canvases.get(change.id)??null,change.after);
   if(change.kind==='element')return equal(elements.get(change.id)??null,change.after);
@@ -157,6 +191,8 @@ function changeSatisfied(elements:ReadonlyMap<Id,ElementRecord>,canvases:Readonl
   if(change.field.startsWith('data.')){const key=change.field.slice(5);return Object.hasOwn(element.data,key)===(change.afterPresent??true)&&equal(element.data[key]??null,change.after);}
   return equal((element as unknown as Record<string,unknown>)[change.field],change.after);
 }
+/** 倒序并交换 before/after，生成撤销变化；字段存在性标记也一起交换。
+ * 如先创建再改名，撤销必须先撤改名再撤创建，因此不能只交换值而保持原顺序。 */
 export function invert(changes: readonly Change[]): readonly Change[] {
   return changes.slice().reverse().map(change => {
     if(change.kind==='field'){const{beforePresent,afterPresent,...record}=change;return freeze({...record,before:change.after,after:change.before,...(afterPresent===undefined?{}:{beforePresent:afterPresent}),...(beforePresent===undefined?{}:{afterPresent:beforePresent})});}
diff --git a/src/lib/canvas-core/history-transition.ts b/src/lib/canvas-core/history-transition.ts
index 5304c61..af6343d 100644
--- a/src/lib/canvas-core/history-transition.ts
+++ b/src/lib/canvas-core/history-transition.ts
@@ -1,14 +1,25 @@
+/**
+ * history 的可逆增量记录：保存两栈 ID 顺序，以及历史项发生变化的数组区间。
+ * 与 history.ts 的区别：这里恢复“历史元数据”，不执行文档修改或发送请求。
+ * journal/恢复与资源 pin 扫描使用这些记录，既能回放，也保留被清 redo/淘汰的旧内容。
+ */
 import type { Change, HistoryEntry, HistoryState, Id } from './types.ts';
 import { equal, fault, freeze, readMap, validJson } from './values.ts';
 
+/** 数组区间补丁：共同前缀后的 offset、两边总长度与替换前后区间；共同后缀不重复保存。 */
 type Splice<T>={readonly offset:number;readonly beforeLength:number;readonly afterLength:number;readonly before:readonly T[];readonly after:readonly T[]};
+/** 历史项的展示/分组元数据；变化数组和 operation IDs 分开描述。 */
 type Meta={readonly label:string;readonly groupId?:Id};
+/** 同一 entry 的元数据与两个数组补丁；null 表示该侧不存在这个历史项。 */
 type EntryPatch={readonly id:Id;readonly before:Meta|null;readonly after:Meta|null;readonly changes:Splice<Change>;readonly operationIds:Splice<Id>};
+/** version 控制解释器兼容性，rootRevision 关联发布版本；不等同于服务端版本号。 */
 export type HistoryTransition={readonly version:1;readonly rootRevision:number;readonly entryId?:Id;readonly before:{readonly undo:readonly Id[];readonly redo:readonly Id[]};readonly after:{readonly undo:readonly Id[];readonly redo:readonly Id[]};readonly entries:readonly EntryPatch[]};
 // Resource scans revisit the same transition across many durability cuts. Cache
 // only its flattened changes, never registry-dependent references or callbacks.
 const transitionChanges=new WeakMap<HistoryTransition,readonly Change[]>();
 const immutableData=new WeakSet<object>();
+/** 检查可安全跨持久切点复用的深不可变普通数据，最多 64 层。
+ * 冻结的 getter 仍可能返回不同值，稀疏数组也不是完整区间，因此都不允许缓存。 */
 function immutablePlainData(value:unknown,depth=0):boolean{
   if(depth>64)return false;
   if(value===null||typeof value!=='object')return typeof value!=='function';
@@ -23,48 +34,65 @@ function immutablePlainData(value:unknown,depth=0):boolean{
   }
   immutableData.add(value);return true;
 }
+/** 提取除 id/changes/operationIds 外的元数据，缺项用 null 表示，以便正反向校验。 */
 const meta=(entry:HistoryEntry|undefined):Meta|null=>{if(!entry)return null;const{id:_id,changes:_changes,operationIds:_operations,...remaining}=entry;return remaining;};
+/** 去掉相等的共同前缀、后缀，只保存真正变化的中间区间；后缀不能与前缀重叠。 */
 function splice<T>(before:readonly T[],after:readonly T[]):Splice<T>{
   let offset=0,suffix=0;while(offset<before.length&&offset<after.length&&equal(before[offset],after[offset]))offset++;
   while(suffix<before.length-offset&&suffix<after.length-offset&&equal(before[before.length-suffix-1],after[after.length-suffix-1]))suffix++;
   return{offset,beforeLength:before.length,afterLength:after.length,before:before.slice(offset,before.length-suffix),after:after.slice(offset,after.length-suffix)};
 }
 /** Store changed ranges only. Clearing redo/eviction still retains the removed entry records needed to reverse that transition. */
+/** 对比两份 history，记录新增、删除和修改的 entry 及两栈顺序。
+ * 默认无变化不造记录；recordNoop 用于调用方显式需要记录发布边界的情形。 */
 export function describeHistoryTransition(before:HistoryState,after:HistoryState,rootRevision:number,entryId?:Id,recordNoop=false):HistoryTransition|undefined{
   const entries:EntryPatch[]=[];
   for(const id of new Set([...before.entries.keys(),...after.entries.keys()])){const a=before.entries.get(id),b=after.entries.get(id);if(equal(a,b))continue;entries.push({id,before:meta(a),after:meta(b),changes:splice(a?.changes??[],b?.changes??[]),operationIds:splice(a?.operationIds??[],b?.operationIds??[])});}
   if(!recordNoop&&!entries.length&&equal(before.undo,after.undo)&&equal(before.redo,after.redo))return undefined;
   return freeze({version:1,rootRevision,...(entryId?{entryId}:{}),before:{undo:before.undo,redo:before.redo},after:{undo:after.undo,redo:after.redo},entries});
 }
+/** 验证外部/恢复的增量 DTO，未知 version 明确要求其它解释器。
+ * checkChanges 可由调用方注入更严格的 Change 校验，本函数本身不依赖 registry。 */
 export function validateHistoryTransition(value:unknown,checkChanges?:(value:unknown)=>unknown):asserts value is HistoryTransition{
+  // 四个局部校验器统一抛领域错误，分别约束普通记录、非负整数、单 ID 和 ID 数组。
   const object=(v:unknown):Record<string,unknown>=>{if(!v||typeof v!=='object'||Array.isArray(v))throw fault('invalid_history_transition');return v as Record<string,unknown>;};
   const integer=(v:unknown)=>{if(typeof v!=='number'||!Number.isSafeInteger(v)||v<0)throw fault('invalid_history_transition');};
   const id=(v:unknown)=>{if(typeof v!=='string'||!v)throw fault('invalid_history_transition');};
   const ids=(v:unknown):string[]=>{if(!Array.isArray(v))throw fault('invalid_history_transition');v.forEach(id);return v;};
   const raw=object(value);if(raw.version!==1)throw fault('history_transition_interpreter_unavailable');if(!validJson(value))throw fault('invalid_history_transition');integer(raw.rootRevision);if(raw.entryId!==undefined)id(raw.entryId);
+  // 同一侧 undo/redo 中不允许重复 ID，避免同一项同时处于两个栈或重复出现。
   for(const side of [raw.before,raw.after]){const s=object(side),list=[...ids(s.undo),...ids(s.redo)];if(new Set(list).size!==list.length)throw fault('invalid_history_transition');}
   if(!Array.isArray(raw.entries))throw fault('invalid_history_transition');const seen=new Set<string>();
   for(const item of raw.entries){const p=object(item);id(p.id);if(seen.has(p.id as string))throw fault('invalid_history_transition');seen.add(p.id as string);
     for(const side of [p.before,p.after])if(side!==null){const m=object(side);if(typeof m.label!=='string'||['id','changes','operationIds'].some(key=>Object.hasOwn(m,key)))throw fault('invalid_history_transition');if(m.groupId!==undefined)id(m.groupId);}
+    // 两边保留的前后缀长度必须一致；不存在的历史项不允许带非零原数组长度。
     for(const key of ['changes','operationIds']){const patch=object(p[key]);for(const field of ['offset','beforeLength','afterLength'])integer(patch[field]);if(!Array.isArray(patch.before)||!Array.isArray(patch.after))throw fault('invalid_history_transition');const{offset,beforeLength,afterLength}=patch as unknown as Splice<unknown>;if(offset+patch.before.length>beforeLength||offset+patch.after.length>afterLength||beforeLength-patch.before.length!==afterLength-patch.after.length)throw fault('invalid_history_transition');if(key==='operationIds'){ids(patch.before);ids(patch.after);}else{checkChanges?.(patch.before);checkChanges?.(patch.after);}
       if(p.before===null&&beforeLength!==0||p.after===null&&afterLength!==0)throw fault('invalid_history_transition');
     }
   }
 }
 /** Conditional metadata-only replay. A mismatch leaves the supplied history untouched. */
+/** 先检查栈和每个区间仍匹配预期，再在私有副本上正向/反向回放元数据。
+ * 任一冲突抛出而不修改输入 history；不能拿旧 journal 覆盖新的历史顺序。 */
 export function applyHistoryTransition(history:HistoryState,transition:HistoryTransition,direction:'forward'|'reverse'):HistoryState{
   validateHistoryTransition(transition);const reverse=direction==='reverse',source=reverse?transition.after:transition.before,destination=reverse?transition.before:transition.after;
   if(!equal({undo:history.undo,redo:history.redo},source))throw fault('history_transition_conflict');
+  /** 按方向交换 expected/insert；同时比较总长度和旧区间，防止错位拼接。 */
   function apply<T>(current:readonly T[],patch:Splice<T>):readonly T[]{const expected=reverse?patch.after:patch.before,insert=reverse?patch.before:patch.after,length=reverse?patch.afterLength:patch.beforeLength;if(current.length!==length||!equal(current.slice(patch.offset,patch.offset+expected.length),expected))throw fault('history_transition_conflict');return[...current.slice(0,patch.offset),...insert,...current.slice(patch.offset+expected.length)];}
+  // 各 entry 使用独立数组补丁，新增/删除也校验旧元数据，不直接拿整份快照覆盖。
   const entries=new Map(history.entries);
   for(const patch of transition.entries){const entry=entries.get(patch.id),expected=reverse?patch.after:patch.before,next=reverse?patch.before:patch.after;if(!equal(meta(entry),expected))throw fault('history_transition_conflict');const changes=apply(entry?.changes??[],patch.changes),operationIds=apply(entry?.operationIds??[],patch.operationIds);if(next)entries.set(patch.id,freeze({id:patch.id,...next,changes,operationIds}));else entries.delete(patch.id);}
+  // 最终两栈必须精确覆盖 entries 表，不能留下孤立项或指向缺失 entry 的栈 ID。
   const ids=[...destination.undo,...destination.redo];if(ids.length!==entries.size||ids.some(id=>!entries.has(id)))throw fault('history_transition_conflict');
   return Object.freeze({undo:freeze([...destination.undo]),redo:freeze([...destination.redo]),entries:readMap(entries)});
 }
+/** 汇总增量两侧出现的 Change，供资源保留扫描使用；不执行这些修改。
+ * 只有自有区间且整条 transition 深不可变时才缓存，否则每次重新计算。 */
 export function historyTransitionChanges(transition:HistoryTransition):readonly Change[]{
   const cached=transitionChanges.get(transition);if(cached)return cached;
   validateHistoryTransition(transition);
   const changes=transition.entries.flatMap(patch=>[...patch.changes.before,...patch.changes.after]);
+  // 属性来自原型或 getter 时不可把一次结果当永久事实，避免错误释放资源 pin。
   const ownRanges=Object.hasOwn(transition,'entries')&&transition.entries.every(patch=>Object.hasOwn(patch,'changes')&&Object.hasOwn(patch.changes,'before')&&Object.hasOwn(patch.changes,'after'));
   if(!ownRanges||!immutablePlainData(transition))return changes;
   const result=Object.freeze(changes);transitionChanges.set(transition,result);return result;
diff --git a/src/lib/canvas-core/history.ts b/src/lib/canvas-core/history.ts
index 4bfb544..2ce48d6 100644
--- a/src/lib/canvas-core/history.ts
+++ b/src/lib/canvas-core/history.ts
@@ -1,22 +1,35 @@
+/**
+ * 历史执行规划：把 undo/redo 给出的 changes 应用到私有文档副本。
+ * 本模块不移动 undo/redo 栈、不发请求；editor/coordinator 在规划成功后统一发布。
+ * 删除后恢复的元素沿用 ID，但必须获得大于墓碑的新 incarnation，使旧异步回调失效。
+ */
 import type { Change, Document, ElementRecord, Id, Registry } from './types.ts';
 import { applyChanges, validateDocument } from './document.ts';
 import { freeze } from './values.ts';
 
 /** Pure history execution, also used to validate recovery proposals before publication. */
+/** 顺序回放一组历史修改，完成整份文档校验后返回候选文档和实际 changes。
+ * remap 供调用者把其它历史目标同步映射到恢复后的 incarnation；失败时原文档不变。 */
 export function planHistoryChanges(initial:Document,planned:readonly Change[],registry:Registry){
+  // ID →（旧 incarnation → 新 incarnation）；同一批恢复可能形成多级映射链。
   const generations=new Map<Id,Map<number,number>>();
+  // 追踪到最终代次，避免后面的字段修改仍指向本批较早的已替换代次。
   const incarnation=(id:Id,value:number)=>{const mapping=generations.get(id);while(mapping?.has(value))value=mapping.get(value)!;return value;};
+  // 只改生命周期身份：字段目标与整元素 before/after 都要一致，canvas 变更原样通过。
   const remap=(change:Change):Change=>{
     if(change.kind==='field'){const next=incarnation(change.target.id,change.target.incarnation);return next===change.target.incarnation?change:freeze({...change,target:{...change.target,incarnation:next}});}
     if(change.kind==='element'){const record=(value:ElementRecord|null)=>value?{...value,incarnation:incarnation(value.id,value.incarnation)}:null;return freeze({...change,before:record(change.before),after:record(change.after)});}
     return change;
   };
   let document=initial;const changes:Change[]=[];
+  // 私有 draft 逐项推进，因此同一批后面的恢复可以看到前面已写入的墓碑。
   for(const original of planned){
     let change=remap(original);
+    // 从不存在恢复为存在时，若原代次已死，分配 dead+1 并重写本条及后续相关变化。
     if(change.kind==='element'&&!change.before&&change.after){const dead=document.tombstones.get(change.id);if(dead!==undefined&&change.after.incarnation<=dead){const mapping=generations.get(change.id)??new Map<number,number>();mapping.set(change.after.incarnation,dead+1);generations.set(change.id,mapping);change=remap(change);}}
     document=applyChanges(document,[change]);changes.push(change);
   }
+  // 暂态允许先恢复端点再恢复边；只有整批完成后才检查最终树、引用和 owner 一致性。
   validateDocument(document,registry);
   return{document,changes:freeze(changes),remap,restored:generations.size>0};
 }
diff --git a/src/lib/canvas-core/structure.ts b/src/lib/canvas-core/structure.ts
index 5d98ed7..0deee89 100644
--- a/src/lib/canvas-core/structure.ts
+++ b/src/lib/canvas-core/structure.ts
@@ -1,3 +1,7 @@
+/**
+ * 文档结构修改的纯规划函数：删除拥有子树，以及重挂后的连线 owner 修复。
+ * 只返回条件 Change，不直接发布 editor 状态；调用方把它们合入一次事务再校验。
+ */
 import type {DocumentQueries} from './queries.ts';
 import type { Change, Document, Id, Target } from './types.ts';
 import { commonCanvas, targetElement } from './document.ts';
@@ -5,17 +9,23 @@ import { canvasTransform, convertPath } from './coordinates.ts';
 import { equal, freeze, fault } from './values.ts';
 
 /** Own the subtree explicitly; geometry/visibility never selects which descendants are deleted. */
+/** 删除目标、由它作为入口拥有的全部子 canvas/成员，以及这些成员关联的边。
+ * queries 是可选的同版本关系索引；没有索引时扫描规范化文档，删除范围不依赖 DOM。 */
 export function removalChanges(document:Document,target:Target,queries?:DocumentQueries):readonly Change[] {
+  // 索引快路径：先核对 snapshot 身份，再用显式 DFS stack 遍历拥有树。
   if(queries){
     if(queries.document!==document)throw fault('stale_query_snapshot');const element=targetElement(document,target),elements=new Set<Id>([element.id]),canvases=new Set<Id>(),child=queries.relations.childCanvasByEntry.get(element.id),stack=child?[child]:[];
     while(stack.length){const id=stack.pop()!;if(canvases.has(id))continue;canvases.add(id);stack.push(...queries.childCanvases(id));for(const member of queries.members(id))elements.add(member);}
+    // 关联边可能属于更上级 canvas，即使不在子树成员表中也必须随端点删除。
     for(const id of [...elements])for(const edge of queries.incident(id))elements.add(edge);
     return freeze([...queries.orderedElements(elements).map(id=>({kind:'element' as const,id,before:document.elements.get(id)!,after:null})),...queries.orderedCanvases(canvases).map(id=>({kind:'canvas' as const,id,before:document.canvases.get(id)!,after:null}))]);
   }
+  // 扫描路径构造 parent→children 临时表；Set 去重，stack 避免 JS 递归调用栈增长。
   const element=targetElement(document,target),elements=new Set<Id>([element.id]),canvases=new Set<Id>(),children=new Map<Id,Id[]>();
   for(const canvas of document.canvases.values())if(canvas.parent){const list=children.get(canvas.parent.canvasId)??[];list.push(canvas.id);children.set(canvas.parent.canvasId,list);}
   const stack=[...document.canvases.values()].filter(canvas=>canvas.parent?.entryElementId===element.id).map(canvas=>canvas.id);
   while(stack.length){const id=stack.pop()!;if(canvases.has(id))continue;canvases.add(id);for(const child of children.get(id)??[])stack.push(child);}
+  // 先收集全部被删成员，再找相关边，防止边扫描先后顺序影响删除结果。
   for(const record of document.elements.values())if(canvases.has(record.ownerCanvasId))elements.add(record.id);
   for(const record of document.elements.values())if(record.structure==='connection'&&(elements.has(record.source.elementId)||elements.has(record.target.elementId)))elements.add(record.id);
   return freeze([
@@ -25,11 +35,14 @@ export function removalChanges(document:Document,target:Target,queries?:Document
 }
 
 /** Ownership changes and their curve coordinates are one operation, with the same stable edge identity. */
+/** 端点重挂后，把边移到两端所属 canvas 的最近共同上级，保持边 ID/incarnation。
+ * 曲线坐标属于旧 owner 空间，因此 owner 与 path 必须作为同一操作一起转换。 */
 export function repairConnectionOwners(before:Document,document:Document):readonly Change[] {
   const changes:Change[]=[];
   for(const edge of document.elements.values())if(edge.structure==='connection'){
     const source=document.elements.get(edge.source.elementId),target=document.elements.get(edge.target.elementId);if(!source||!target)continue;
     const owner=commonCanvas(document,source.ownerCanvasId,target.ownerCanvasId);if(owner===edge.ownerCanvasId)continue;
+    // 旧 owner 可能已从新文档移除：优先用 before 的变换解释旧曲线，再转到新 owner。
     const path=convertPath(edge.path,canvasTransform(before.canvases.has(edge.ownerCanvasId)?before:document,edge.ownerCanvasId),canvasTransform(document,owner));
     changes.push({kind:'field',target:{id:edge.id,incarnation:edge.incarnation},field:'ownerCanvasId',before:edge.ownerCanvasId,after:owner});
     if(!equal(edge.path,path))changes.push({kind:'field',target:{id:edge.id,incarnation:edge.incarnation},field:'path',before:edge.path,after:path});
diff --git a/src/lib/canvas-core/units.ts b/src/lib/canvas-core/units.ts
index 75c0414..fd8ca79 100644
--- a/src/lib/canvas-core/units.ts
+++ b/src/lib/canvas-core/units.ts
@@ -1,27 +1,40 @@
+/**
+ * 表现单位换算：presentation.unitScale 表示视觉尺度，不改变元素的归属关系。
+ * 没有 unitScale 时按 1 解释；其它 presentation 字段可能属于宿主，必须无损保留。
+ */
 import type { Json } from './types.ts';
 import { fault } from './values.ts';
 
+/** 框架保留的表现元数据字段；可选表示使用默认比例。 */
 export type PresentationUnits = { readonly unitScale?: number };
 
 /** Reserved presentation metadata, independent of canvas ownership. Absence means one visual unit per owner unit. */
+/** 这里只校验可识别的 unitScale；非对象值交给更严格的写入路径决定是否支持。 */
 export function presentationUnitsValid(value:Json|undefined):boolean {
   if(!value||typeof value!=='object'||Array.isArray(value))return true;
   return value.unitScale===undefined||typeof value.unitScale==='number'&&Number.isFinite(value.unitScale)&&value.unitScale>0;
 }
+/** 读取有效比例，缺省为 1；对象中显式出现非法比例时拒绝继续计算。 */
 export function unitScale(value:Json|undefined):number {
   if(!presentationUnitsValid(value))throw fault('invalid_presentation_units');
   return value&&typeof value==='object'&&!Array.isArray(value)&&typeof value.unitScale==='number'?value.unitScale:1;
 }
+/** 普通数值比较有绝对误差下限，适合判断计算结果是否应归一到 1。 */
 export const closeNumber=(a:number,b:number)=>Math.abs(a-b)<=Number.EPSILON*64*Math.max(1,Math.abs(a),Math.abs(b));
+/** 比例比较使用相对误差，避免极小但不同的有效比例被绝对阈值吞掉。 */
 export const closeScale=(a:number,b:number)=>Math.abs(a-b)<=Number.EPSILON*64*Math.max(Number.MIN_VALUE,Math.abs(a),Math.abs(b));
+/** 获取可合并的对象元数据；空值当空表，原始值/数组拒绝，以免合并时丢失原值。 */
 export function presentationRecord(value:Json|undefined):Readonly<Record<string,Json>> {
   if(value===undefined||value===null)return{};
   if(typeof value!=='object'||Array.isArray(value))throw fault('unsupported_presentation_units');
   unitScale(value);return value;
 }
 /** Normalize only the framework-owned unit field; all other presentation properties survive. */
+/** 返回替换比例后的元数据：等效值复用原对象，比例为 1 时省略保留字段。
+ * 仅更新 unitScale，不清掉宿主扩展字段；字段全部清空时返回 undefined。 */
 export function withUnitScale(value:Json|undefined,scale:number):Json|undefined {
   if(!Number.isFinite(scale)||scale<=0)throw fault('invalid_presentation_units');
+  // 坐标换算可能产生接近 1 的浮点误差，统一表示能减少无意义的模型修改。
   const normalized=closeNumber(scale,1)?1:scale;
   if(closeScale(unitScale(value),normalized))return value;
   const fields=new Map(Object.entries(presentationRecord(value)));
diff --git a/src/lib/canvas-core/values.ts b/src/lib/canvas-core/values.ts
index 480dc91..b3f5226 100644
--- a/src/lib/canvas-core/values.ts
+++ b/src/lib/canvas-core/values.ts
@@ -1,12 +1,21 @@
+/**
+ * 内核共享的值操作：错误归一化、JSON 值复制/比较，以及运行时只读集合。
+ * 这些工具不读取网络或编辑器状态。注意类型上的 readonly 与运行时不可修改不是一回事；
+ * readMap/readSet 通过隐藏可变容器实现后者，freeze 不会使 Map 的 set 方法失效。
+ */
 import type { Id, Json, ReadonlyValueSet } from './types.ts';
 
+/** 构造携带稳定错误码和相关对象 ID 的错误，供命令层返回可解释的拒绝结果。 */
 export function fault(code: string, targets: readonly Id[] = []): Error & { code: string; targets: readonly Id[] } {
   return Object.assign(new Error(code), { code, targets });
 }
+/** 将捕获的异常归一化为只读 rejected 结果；无领域错误码时使用 invalid_command。 */
 export function reject(error: unknown) {
   const value = error as { code?: string; targets?: readonly string[] };
   return Object.freeze({ status: 'rejected' as const, code: value?.code || 'invalid_command', targets: value?.targets || [] });
 }
+/** 递归冻结普通对象/数组的可枚举值；已冻结对象直接返回，不继续检查其子树。
+ * 调用者负责提供适合此工具的数据，不能用它证明任意外部对象已经深度不可变。 */
 export function freeze<T>(value: T): T {
   if (value && typeof value === 'object' && !Object.isFrozen(value)) {
     for (const child of Object.values(value)) freeze(child);
@@ -14,30 +23,40 @@ export function freeze<T>(value: T): T {
   }
   return value;
 }
+/** JSON 往返复制已验证的数据，切断共享引用；undefined 原样返回。
+ * 此处不是校验器：JSON 会丢弃某些非法字段，因此外部输入必须在复制前验证。 */
 export function clone<T>(value: T): T {
   if (value === undefined) return value;
   return JSON.parse(JSON.stringify(value)) as T;
 }
+/** 按可枚举自有键递归比较 JSON 风格的值；数组与对象不能互相视为相等。
+ * 不处理任意循环对象，也不把 Map/Set 等实例当成业务值来比较。 */
 export function equal(a: unknown, b: unknown): boolean {
   if (Object.is(a, b)) return true;
   if (!a || !b || typeof a !== 'object' || typeof b !== 'object' || Array.isArray(a) !== Array.isArray(b)) return false;
   const left = Object.keys(a), right = Object.keys(b);
   return left.length === right.length && left.every(key => Object.prototype.hasOwnProperty.call(b, key) && equal((a as Record<string, unknown>)[key], (b as Record<string, unknown>)[key]));
 }
+// 只在本模块中标记只读视图的来源，WeakSet 不会阻止无引用的视图被回收。
 const ownedMapViews=new WeakSet<object>();
 /** Internal provenance only; table ownership does not imply immutable values. */
+/** 查询“是否由 readMap 创建”，不证明表内每个 value 已冻结或通过 schema。 */
 export function isOwnedMapView(value:object){return ownedMapViews.has(value);}
 /** A capability-safe read view: unlike TS ReadonlyMap, no .set is exposed at runtime. */
+/** 复制表成员并仅暴露读取能力，外部既拿不到原 Map，也拿不到 set/delete。
+ * value 保留原引用，深度不可变性由生产这些 value 的模块负责。 */
 export function readMap<K, V>(input: ReadonlyMap<K, V>): ReadonlyMap<K, V> {
   const map = new Map(input);
   const view: ReadonlyMap<K, V> = {
     get size() { return map.size; }, get: key => map.get(key), has: key => map.has(key),
     entries: () => map.entries(), keys: () => map.keys(), values: () => map.values(),
     [Symbol.iterator]: () => map[Symbol.iterator](),
+    // 回调的第三个参数也必须是安全视图，不能把内部可变 Map 泄漏出去。
     forEach: (callback, thisArg) => map.forEach((value, key) => callback.call(thisArg, value, key, view)),
   };
   const result=Object.freeze(view);ownedMapViews.add(result);return result;
 }
+/** 捕获一份成员集合并隐藏 add/delete；回调同样只接触只读视图。 */
 export function readSet<T>(input: Iterable<T>): ReadonlyValueSet<T> {
   const set = new Set(input);
   const view: ReadonlyValueSet<T> = {
@@ -46,6 +65,8 @@ export function readSet<T>(input: Iterable<T>): ReadonlyValueSet<T> {
   };
   return Object.freeze(view);
 }
+/** 递归检查 JSON 值域：排除 undefined/函数/非有限数，最多允许 64 层。
+ * 这里只检查值形状，不验证组件 schema，也不是所有原型/属性描述符的严格捕获器。 */
 export function validJson(value: unknown, depth = 0): value is Json {
   if (depth > 64) return false;
   if (value === null || typeof value === 'string' || typeof value === 'boolean') return true;