diff --git a/package-lock.json b/package-lock.json
index f0fb618770..56822c60a2 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -23314,10 +23314,6 @@
       "license": "MIT",
       "dependencies": {
         "escape-string-regexp": "^5.0.0",
-        "fast-safe-stringify": "^2.0.7",
-        "is-plain-obj": "^4.0.0",
-        "map-obj": "^5.0.0",
-        "path-exists": "^5.0.0",
         "smol-toml": "^1.5.2"
       },
       "devDependencies": {
diff --git a/packages/headers-parser/package.json b/packages/headers-parser/package.json
index dab51c540f..6f149a1a41 100644
--- a/packages/headers-parser/package.json
+++ b/packages/headers-parser/package.json
@@ -27,11 +27,7 @@
   "license": "MIT",
   "dependencies": {
     "smol-toml": "^1.5.2",
-    "escape-string-regexp": "^5.0.0",
-    "fast-safe-stringify": "^2.0.7",
-    "is-plain-obj": "^4.0.0",
-    "map-obj": "^5.0.0",
-    "path-exists": "^5.0.0"
+    "escape-string-regexp": "^5.0.0"
   },
   "devDependencies": {
     "@types/node": "^22.12.0",
diff --git a/packages/headers-parser/src/line_parser.ts b/packages/headers-parser/src/line_parser.ts
index fc61ba4958..874927b4e3 100644
--- a/packages/headers-parser/src/line_parser.ts
+++ b/packages/headers-parser/src/line_parser.ts
@@ -1,7 +1,5 @@
 import fs from 'fs/promises'
 
-import { pathExists } from 'path-exists'
-
 import { splitResults } from './results.js'
 import type { MinimalHeader } from './types.js'
 
@@ -23,7 +21,9 @@ export const parseFileHeaders = async function (headersFile: string): Promise<Pa
 }
 
 const parseHeaders = async function (headersFile: string): Promise<(Error | RawHeaderFileLine)[]> {
-  if (!(await pathExists(headersFile))) {
+  try {
+    await fs.access(headersFile)
+  } catch {
     return []
   }
 
diff --git a/packages/headers-parser/src/merge.ts b/packages/headers-parser/src/merge.ts
index f408981f39..66fb49682b 100644
--- a/packages/headers-parser/src/merge.ts
+++ b/packages/headers-parser/src/merge.ts
@@ -1,5 +1,3 @@
-import stringify from 'fast-safe-stringify'
-
 import { splitResults } from './results.js'
 import type { Header, MinimalHeader } from './types.js'
 
@@ -47,12 +45,12 @@ const removeDuplicates = function (headers: MinimalHeader[] | Header[]) {
   return result.reverse()
 }
 
-// We generate a unique header key based on JSON stringify. However, because some
-// properties can be regexes, we need to replace those by their toString representation
-// given the default will be and empty object
+// We generate a unique header key based on JSON stringify. The `values` keys
+// are sorted so that key order does not affect the result. `forRegExp` is
+// derived from `for`, so it does not need to be part of the key.
 const generateHeaderKey = function (header: MinimalHeader | Header): string {
-  return stringify.default.stableStringify(header, (_, value) => {
-    if (value instanceof RegExp) return value.toString()
-    return value
-  })
+  return JSON.stringify([
+    header.for,
+    Object.entries(header.values).sort(([keyA], [keyB]) => (keyA < keyB ? -1 : keyA > keyB ? 1 : 0)),
+  ])
 }
diff --git a/packages/headers-parser/src/netlify_config_parser.ts b/packages/headers-parser/src/netlify_config_parser.ts
index 7500df3e43..1f466a1247 100644
--- a/packages/headers-parser/src/netlify_config_parser.ts
+++ b/packages/headers-parser/src/netlify_config_parser.ts
@@ -1,7 +1,6 @@
 import { promises as fs } from 'fs'
 
 import { parse as loadToml } from 'smol-toml'
-import { pathExists } from 'path-exists'
 
 import { splitResults } from './results.js'
 import type { MinimalHeader } from './types.js'
@@ -10,7 +9,9 @@ import type { MinimalHeader } from './types.js'
 // This field is already an array of objects, so it only validates and
 // normalizes it.
 export const parseConfigHeaders = async function (netlifyConfigPath: string) {
-  if (!(await pathExists(netlifyConfigPath))) {
+  try {
+    await fs.access(netlifyConfigPath)
+  } catch {
     return splitResults([])
   }
 
diff --git a/packages/headers-parser/src/normalize.ts b/packages/headers-parser/src/normalize.ts
index 45aa1081dc..030d75e813 100644
--- a/packages/headers-parser/src/normalize.ts
+++ b/packages/headers-parser/src/normalize.ts
@@ -1,11 +1,10 @@
-import isPlainObj from 'is-plain-obj'
-import mapObj from 'map-obj'
-import type { Mapper } from 'map-obj'
-
 import { getForRegExp } from './for_regexp.js'
 import { splitResults } from './results.js'
 import type { Header, MinimalHeader } from './types.js'
 
+const isObject = (value: unknown): value is Record<string, unknown> =>
+  typeof value === 'object' && value !== null && !Array.isArray(value)
+
 export interface MinimalNormalizedHeaders {
   headers: MinimalHeader[]
   errors: Error[]
@@ -50,7 +49,7 @@ function parseHeader(
   index: number,
   minimal: boolean,
 ): undefined | Error | MinimalHeader | Header {
-  if (!isPlainObj(header)) {
+  if (!isObject(header)) {
     return new TypeError(`Header must be an object not: ${header}`)
   }
 
@@ -112,15 +111,15 @@ const normalizePath = function (rawPath?: string): string {
 
 // Normalize and validate the `values` field
 const normalizeValues = function (rawValues: Record<string, string | string[]>): Record<string, string> {
-  if (!isPlainObj(rawValues)) {
+  if (!isObject(rawValues)) {
     throw new TypeError(`"values" must be an object not: ${rawValues}`)
   }
 
-  return mapObj(rawValues, normalizeValue)
+  return Object.fromEntries(Object.entries(rawValues).map(([rawKey, rawValue]) => normalizeValue(rawKey, rawValue)))
 }
 
 // Normalize and validate each header `values`
-const normalizeValue: Mapper<Record<string, string | string[]>, string, string> = function (rawKey, rawValue) {
+const normalizeValue = function (rawKey: string, rawValue: string | string[]): [string, string] {
   const key: string = rawKey.trim()
   if (key === '' || key === 'undefined') {
     throw new Error('Empty header name')