diff --git a/src/doc/Document.ts b/src/doc/Document.ts
index de666740..2fb90a6f 100644
--- a/src/doc/Document.ts
+++ b/src/doc/Document.ts
@@ -205,7 +205,7 @@ export class Document<
       const keyToStr = (v: unknown) =>
         typeof v === 'number' || v instanceof String || v instanceof Number
       const asStr = replacer.filter(keyToStr).map(String)
-      if (asStr.length > 0) replacer = replacer.concat(asStr)
+      if (asStr.length > 0) replacer = [...replacer, ...asStr]
       nc = new NodeCreator(this, options, replacer)
     } else {
       options ??= replacer ?? undefined
diff --git a/src/nodes/Alias.ts b/src/nodes/Alias.ts
index 25922ab1..eee15eac 100644
--- a/src/nodes/Alias.ts
+++ b/src/nodes/Alias.ts
@@ -110,8 +110,7 @@ export class Alias implements NodeBase {
     }
     if (maxAliasCount >= 0) {
       data.count += 1
-      if (data.aliasCount === 0)
-        data.aliasCount = getAliasCount(doc, source, anchors)
+      data.aliasCount ||= getAliasCount(doc, ctx, source, anchors)
       if (data.count * data.aliasCount > maxAliasCount) {
         const msg =
           'Excessive alias count indicates a resource exhaustion attack'
@@ -142,21 +141,22 @@ export class Alias implements NodeBase {
 
 function getAliasCount(
   doc: Document,
+  ctx: ToJSContext,
   node: Node | Pair | null,
   anchors: ToJSContext['anchors']
 ): number {
   if (node instanceof Alias) {
-    const source = node.resolve(doc)
+    const source = node.resolve(doc, ctx)
     const anchor = anchors && source && anchors.get(source)
     return anchor ? anchor.count * anchor.aliasCount : 0
   } else if (node instanceof Pair) {
-    const kc = getAliasCount(doc, node.key, anchors)
-    const vc = getAliasCount(doc, node.value, anchors)
+    const kc = getAliasCount(doc, ctx, node.key, anchors)
+    const vc = getAliasCount(doc, ctx, node.value, anchors)
     return Math.max(kc, vc)
   } else if (node && 'items' in node) {
     let count = 0
     for (const item of node.items) {
-      const c = getAliasCount(doc, item, anchors)
+      const c = getAliasCount(doc, ctx, item, anchors)
       if (c > count) count = c
     }
     return count
diff --git a/src/parse/cst-visit.ts b/src/parse/cst-visit.ts
index 214d549a..ab7b6914 100644
--- a/src/parse/cst-visit.ts
+++ b/src/parse/cst-visit.ts
@@ -75,7 +75,7 @@ export const visit: {
 } = function visit(cst, visitor) {
   if ('type' in cst && cst.type === 'document')
     cst = { start: cst.start, value: cst.value }
-  _visit(Object.freeze([]), cst, visitor)
+  _visit([], cst, visitor)
 }
 
 visit.BREAK = BREAK
@@ -118,11 +118,7 @@ function _visit(
     const token = item[field]
     if (token && 'items' in token) {
       for (let i = 0; i < token.items.length; ++i) {
-        const ci = _visit(
-          Object.freeze(path.concat([[field, i]])),
-          token.items[i],
-          visitor
-        )
+        const ci = _visit([...path, [field, i]], token.items[i], visitor)
         if (typeof ci === 'number') i = ci - 1
         else if (ci === BREAK) return BREAK
         else if (ci === REMOVE) {
diff --git a/src/parse/parser.ts b/src/parse/parser.ts
index 422bbffe..1443cc11 100644
--- a/src/parse/parser.ts
+++ b/src/parse/parser.ts
@@ -641,7 +641,7 @@ export class Parser {
               })
             } else if (start.length > 0) {
               // Not actually at next item
-              it.sep = it.sep.concat(start, this.sourceToken)
+              it.sep = [...it.sep, ...start, this.sourceToken]
             } else {
               it.sep.push(this.sourceToken)
             }
diff --git a/src/schema/tags.ts b/src/schema/tags.ts
index 3b1a8403..c25c1694 100644
--- a/src/schema/tags.ts
+++ b/src/schema/tags.ts
@@ -98,7 +98,7 @@ export function getTags(
   const schemaTags = schemas.get(schemaName)
   if (schemaTags && !customTags) {
     return addMergeTag && !schemaTags.includes(merge)
-      ? schemaTags.concat(merge)
+      ? [...schemaTags, merge]
       : schemaTags.slice()
   }
 
@@ -121,7 +121,7 @@ export function getTags(
   } else if (typeof customTags === 'function') {
     tags = customTags(tags.slice())
   }
-  if (addMergeTag) tags = tags.concat(merge)
+  if (addMergeTag) tags = [...tags, merge]
 
   return tags.reduce<(CollectionTag | ScalarTag)[]>((tags, tag) => {
     const tagObj = typeof tag === 'string' ? tagsByName[tag] : tag
diff --git a/src/schema/yaml-1.1/merge.ts b/src/schema/yaml-1.1/merge.ts
index bc424cf3..f6bca109 100644
--- a/src/schema/yaml-1.1/merge.ts
+++ b/src/schema/yaml-1.1/merge.ts
@@ -49,7 +49,7 @@ export function addMergeToJSMap(
   map: MapLike,
   value: unknown
 ): void {
-  value = ctx && value instanceof Alias ? value.resolve(doc) : value
+  value = ctx && value instanceof Alias ? value.resolve(doc, ctx) : value
   if (value instanceof YAMLSeq)
     for (const it of value.items) mergeValue(doc, ctx, map, it)
   else if (Array.isArray(value))
@@ -63,7 +63,7 @@ function mergeValue(
   map: MapLike,
   value: unknown
 ) {
-  const source = value instanceof Alias ? value.resolve(doc) : value
+  const source = value instanceof Alias ? value.resolve(doc, ctx) : value
   const srcMap = (source as YAMLMap).toJS(doc, ctx, Map<any, any>)
   if (!(srcMap instanceof Map))
     throw new Error('Merge sources must be maps or map aliases')
diff --git a/src/visit.ts b/src/visit.ts
index 01db124d..67e1d70f 100644
--- a/src/visit.ts
+++ b/src/visit.ts
@@ -99,9 +99,9 @@ export const visit: {
 } = function visit(node, visitor) {
   const visitor_ = initVisitor(visitor)
   if (node instanceof Document) {
-    const cd = visit_(null, node.value, visitor_, Object.freeze([node]))
+    const cd = visit_(null, node.value, visitor_, [node])
     if (cd === REMOVE) node.value = new Scalar(null)
-  } else visit_(null, node, visitor_, Object.freeze([]))
+  } else visit_(null, node, visitor_, [])
 }
 
 visit.BREAK = BREAK
@@ -123,7 +123,7 @@ function visit_(
 
   if (typeof ctrl !== 'symbol') {
     if (node instanceof YAMLMap || node instanceof YAMLSeq) {
-      path = Object.freeze([...path, node])
+      path = [...path, node]
       for (let i = 0; i < node.items.length; ++i) {
         const ci = visit_(i, node.items[i], visitor, path)
         if (typeof ci === 'number') i = ci - 1
@@ -134,7 +134,7 @@ function visit_(
         }
       }
     } else if (node instanceof Pair) {
-      path = Object.freeze([...path, node])
+      path = [...path, node]
       const ck = visit_('key', node.key, visitor, path)
       if (ck === BREAK) return BREAK
       else if (ck === REMOVE) node.key = new Scalar(null)
@@ -193,14 +193,9 @@ export const visitAsync: {
 } = async function visitAsync(node, visitor) {
   const visitor_ = initVisitor(visitor)
   if (node instanceof Document) {
-    const cd = await visitAsync_(
-      null,
-      node.value,
-      visitor_,
-      Object.freeze([node])
-    )
+    const cd = await visitAsync_(null, node.value, visitor_, [node])
     if (cd === REMOVE) node.value = new Scalar(null)
-  } else await visitAsync_(null, node, visitor_, Object.freeze([]))
+  } else await visitAsync_(null, node, visitor_, [])
 }
 
 visitAsync.BREAK = BREAK
@@ -222,7 +217,7 @@ async function visitAsync_(
 
   if (typeof ctrl !== 'symbol') {
     if (node instanceof YAMLMap || node instanceof YAMLSeq) {
-      path = Object.freeze([...path, node])
+      path = [...path, node]
       for (let i = 0; i < node.items.length; ++i) {
         const ci = await visitAsync_(i, node.items[i], visitor, path)
         if (typeof ci === 'number') i = ci - 1
@@ -233,7 +228,7 @@ async function visitAsync_(
         }
       }
     } else if (node instanceof Pair) {
-      path = Object.freeze([...path, node])
+      path = [...path, node]
       const ck = await visitAsync_('key', node.key, visitor, path)
       if (ck === BREAK) return BREAK
       else if (ck === REMOVE) node.key = new Scalar(null)