@@ -1,4 +1,5 @@
 const abbrev = require('abbrev')
+const debug = require('./debug')
 const defaultTypeDefs = require('./type-defs')
 
 const hasOwn = (o, k) => Object.prototype.hasOwnProperty.call(o, k)
@@ -30,6 +31,8 @@ function nopt (args, {
   typeDefault,
   dynamicTypes,
 } = {}) {
+  debug(types, shorthands, args, typeDefs)
+
   const data = {}
   const argv = {
     remain: [],
@@ -86,6 +89,7 @@ function clean (data, {
       return
     }
     let val = data[k]
+    debug('val=%j', val)
     const isArray = Array.isArray(val)
     let [hasType, rawType] = getType(k, { types, dynamicTypes })
     let type = rawType
@@ -102,19 +106,25 @@ function clean (data, {
       type = [type]
     }
 
+    debug('val=%j', val)
+    debug('types=', type)
     val = val.map((v) => {
       // if it's an unknown value, then parse false/true/null/numbers/dates
       if (typeof v === 'string') {
+        debug('string %j', v)
         v = v.trim()
         if ((v === 'null' && ~type.indexOf(null))
             || (v === 'true' &&
                (~type.indexOf(true) || hasTypeDef(type, BooleanType)))
             || (v === 'false' &&
                (~type.indexOf(false) || hasTypeDef(type, BooleanType)))) {
           v = JSON.parse(v)
+          debug('jsonable %j', v)
         } else if (hasTypeDef(type, NumberType) && !isNaN(v)) {
+          debug('convert to number', v)
           v = +v
         } else if (hasTypeDef(type, DateType) && !isNaN(Date.parse(v))) {
+          debug('convert to date', v)
           v = new Date(v)
         }
       }
@@ -138,24 +148,32 @@ function clean (data, {
 
       const d = {}
       d[k] = v
+      debug('prevalidated val', d, v, rawType)
       if (!validate(d, k, v, rawType, { typeDefs })) {
         if (invalidHandler) {
           invalidHandler(k, v, rawType, data)
+        } else if (invalidHandler !== false) {
+          debug('invalid: ' + k + '=' + v, rawType)
         }
         return remove
       }
+      debug('validated v', d, v, rawType)
       return d[k]
     }).filter((v) => v !== remove)
 
     // if we allow Array specifically, then an empty array is how we
     // express 'no value here', not null.  Allow it.
     if (!val.length && doesNotHaveTypeDef(type, ArrayType)) {
+      debug('VAL HAS NO LENGTH, DELETE IT', val, k, type.indexOf(ArrayType))
       delete data[k]
     } else if (isArray) {
+      debug(isArray, data[k], val)
       data[k] = val
     } else {
       data[k] = val[0]
     }
+
+    debug('k=%s val=%j', k, val, data[k])
   })
 }
 
@@ -181,21 +199,21 @@ function validate (data, k, val, type, { typeDefs } = {}) {
   }
 
   // Original comment:
-  // NaN is poisonous, it means that something is not allowed.
-
-  // New comment:
-  // Changing this to an isNaN check breaks a lot of tests.
-  // Something is being assumed here that is not actually what happens in practice.
-  // Fixing it is outside the scope of getting linting to pass in this repo.
-  // Leaving as-is for now.
+  // NaN is poisonous.  Means that something is not allowed.
+  // New comment: Changing this to an isNaN check breaks a lot of tests.
+  // Something is being assumed here that is not actually what happens in
+  // practice.  Fixing it is outside the scope of getting linting to pass in
+  // this repo. Leaving as-is for now.
   /* eslint-disable-next-line no-self-compare */
   if (type !== type) {
+    debug('Poison NaN', k, val, type)
     delete data[k]
     return false
   }
 
   // explicit list of values
   if (val === type) {
+    debug('Explicitly allowed %j', val)
     data[k] = val
     return true
   }
@@ -204,6 +222,7 @@ function validate (data, k, val, type, { typeDefs } = {}) {
   let ok = false
   const types = Object.keys(typeDefs)
   for (let i = 0, l = types.length; i < l; i++) {
+    debug('test type %j %j %j', k, val, types[i])
     const t = typeDefs[types[i]]
     if (t && (
       (type && type.name && t.type && t.type.name) ?
@@ -219,6 +238,7 @@ function validate (data, k, val, type, { typeDefs } = {}) {
       }
     }
   }
+  debug('OK? %j (%j %j %j)', ok, k, val, types[types.length - 1])
 
   if (!ok) {
     delete data[k]
@@ -238,11 +258,16 @@ function parse (args, data, remain, {
   const NumberType = typeDefs.Number?.type
   const ArrayType = typeDefs.Array?.type
   const BooleanType = typeDefs.Boolean?.type
+
+  debug('parse', args, data, remain)
+
   const abbrevs = abbrev(Object.keys(types))
+  debug('abbrevs=%j', abbrevs)
   const shortAbbr = abbrev(Object.keys(shorthands))
 
   for (let i = 0; i < args.length; i++) {
     let arg = args[i]
+    debug('arg', arg)
 
     if (arg.match(/^-{2,}$/)) {
       // done with keys.
@@ -264,6 +289,7 @@ function parse (args, data, remain, {
       // see if it's a shorthand
       // if so, splice and back up to re-parse it.
       const shRes = resolveShort(arg, shortAbbr, abbrevs, { shorthands, abbrevHandler })
+      debug('arg=%j shRes=%j', arg, shRes)
       if (shRes) {
         args.splice.apply(args, [i, 1].concat(shRes))
         if (arg !== shRes[0]) {
@@ -282,6 +308,8 @@ function parse (args, data, remain, {
       if (abbrevs[arg] && abbrevs[arg] !== arg) {
         if (abbrevHandler) {
           abbrevHandler(arg, abbrevs[arg])
+        } else if (abbrevHandler !== false) {
+          debug(`abbrev: ${arg} -> ${abbrevs[arg]}`)
         }
         arg = abbrevs[arg]
       }
@@ -324,6 +352,11 @@ function parse (args, data, remain, {
           } else {
             unknownHandler(arg)
           }
+        } else if (unknownHandler !== false) {
+          debug(`unknown: ${arg}`)
+          if (hangingLa) {
+            debug(`unknown: ${la} parsed as normal opt`)
+          }
         }
       }
 
@@ -409,6 +442,7 @@ const singleCharacters = (arg, shorthands) => {
       return l
     }, {})
     shorthands[SINGLES] = singles
+    debug('shorthand singles', singles)
   }
   const chrs = arg.split('').filter((c) => singles[c])
   return chrs.join('') === arg ? chrs : null
@@ -456,6 +490,8 @@ function resolveShort (arg, ...rest) {
   if (shortAbbr[arg]) {
     if (abbrevHandler) {
       abbrevHandler(arg, shortAbbr[arg])
+    } else if (abbrevHandler !== false) {
+      debug(`abbrev: ${arg} -> ${shortAbbr[arg]}`)
     }
     arg = shortAbbr[arg]
   }
 
@@ -1,8 +1,10 @@
 const lib = require('./nopt-lib')
 const defaultTypeDefs = require('./type-defs')
 
-// This is the version of nopt's API that requires setting typeDefs and invalidHandler on the required `nopt` object since it is a singleton.
-// To not do a breaking change an API that requires all options be passed in is located in `nopt-lib.js` and exported here as lib.
+// This is the version of nopt's API that requires setting typeDefs and invalidHandler
+// on the required `nopt` object since it is a singleton. To not do a breaking change
+// an API that requires all options be passed in is located in `nopt-lib.js` and
+// exported here as lib.
 // TODO(breaking): make API only work in non-singleton mode
 
 module.exports = exports = nopt
 
@@ -1,7 +1,8 @@
-const os = require('node:os')
-const path = require('node:path')
-const { Stream } = require('node:stream')
-const { URL } = require('node:url')
+const url = require('url')
+const path = require('path')
+const Stream = require('stream').Stream
+const os = require('os')
+const debug = require('./debug')
 
 function validateString (data, k, val) {
   data[k] = String(val)
@@ -30,6 +31,7 @@ function validatePath (data, k, val) {
 }
 
 function validateNumber (data, k, val) {
+  debug('validate Number %j %j %j', k, val, isNaN(val))
   if (isNaN(val)) {
     return false
   }
@@ -38,6 +40,7 @@ function validateNumber (data, k, val) {
 
 function validateDate (data, k, val) {
   const s = Date.parse(val)
+  debug('validate Date %j %j %j', k, val, s)
   if (isNaN(s)) {
     return false
   }
@@ -60,11 +63,13 @@ function validateBoolean (data, k, val) {
 }
 
 function validateUrl (data, k, val) {
-  const parsed = URL.parse(String(val))
-  if (!parsed) {
+  // Changing this would be a breaking change in the npm cli
+  /* eslint-disable-next-line node/no-deprecated-api */
+  val = url.parse(String(val))
+  if (!val.host) {
     return false
   }
-  data[k] = parsed.href
+  data[k] = val.href
 }
 
 function validateStream (data, k, val) {
@@ -77,7 +82,7 @@ function validateStream (data, k, val) {
 module.exports = {
   String: { type: String, validate: validateString },
   Boolean: { type: Boolean, validate: validateBoolean },
-  url: { type: URL, validate: validateUrl },
+  url: { type: url, validate: validateUrl },
   Number: { type: Number, validate: validateNumber },
   path: { type: path, validate: validatePath },
   Stream: { type: Stream, validate: validateStream },
 
@@ -1,20 +1,18 @@
 {
   "name": "nopt",
-  "version": "10.0.1",
+  "version": "9.0.0",
   "description": "Option parsing for Node, supporting types, shorthands, etc. Used by npm.",
   "author": "GitHub Inc.",
   "main": "lib/nopt.js",
   "scripts": {
-    "test": "node --test './test/**/*.js'",
+    "test": "tap",
     "lint": "npm run eslint",
     "postlint": "template-oss-check",
     "template-oss-apply": "template-oss-apply --force",
     "lintfix": "npm run eslint -- --fix",
-    "snap": "node --test --test-update-snapshots './test/**/*.js'",
+    "snap": "tap",
     "posttest": "npm run lint",
-    "eslint": "eslint \"**/*.{js,cjs,ts,mjs,jsx,tsx}\"",
-    "test:node20": "node --test test",
-    "test:cover": "node --test --experimental-test-coverage --test-timeout=3000 --test-coverage-lines=100 --test-coverage-functions=100 --test-coverage-branches=100 './test/**/*.js'"
+    "eslint": "eslint \"**/*.{js,cjs,ts,mjs,jsx,tsx}\""
   },
   "repository": {
     "type": "git",
@@ -25,26 +23,30 @@
   },
   "license": "ISC",
   "dependencies": {
-    "abbrev": "^5.0.0"
+    "abbrev": "^4.0.0"
   },
   "devDependencies": {
-    "@npmcli/eslint-config": "^7.0.0",
-    "@npmcli/template-oss": "5.1.0"
+    "@npmcli/eslint-config": "^5.0.0",
+    "@npmcli/template-oss": "4.27.1",
+    "tap": "^16.3.0"
+  },
+  "tap": {
+    "nyc-arg": [
+      "--exclude",
+      "tap-snapshots/**"
+    ]
   },
   "files": [
     "bin/",
     "lib/"
   ],
   "engines": {
-    "node": "^22.22.2 || ^24.15.0 || >=26.0.0"
+    "node": "^20.17.0 || >=22.9.0"
   },
   "templateOSS": {
     "//@npmcli/template-oss": "This file is partially managed by @npmcli/template-oss. Edits may be overwritten.",
     "windowsCI": false,
-    "version": "5.1.0",
-    "publish": true,
-    "testRunner": "node:test",
-    "latestCiVersion": 24,
-    "updateNpm": false
+    "version": "4.27.1",
+    "publish": true
   }
 }