diff --git a/lib/cmd-build.js b/lib/cmd-build.js
index 003a16e..2abff85 100644
--- a/lib/cmd-build.js
+++ b/lib/cmd-build.js
@@ -4,7 +4,9 @@ const fs = require('fs')
 const path = require('path')
 const { pipeline } = require('stream/promises')
 
-const { FilemapWithOutput } = require('./core-filemap-with-output')
+const { ListItem } = require('./core-data-structures')
+const { Filemap } = require('./core-filemap-build')
+const { Urlmap } = require('./core-urlmap')
 const { ProcessingFactory } = require('./core-processing-factory')
 const { ProcessingWithCache } = require('./core-processing-with-cache')
 const { copy, mkdir } = require('./util-fs')
@@ -42,10 +44,12 @@ async function build (options, logger) {
   const visited = new Set()
 
   const plugins = loadCustomPlugins(settings.wave?.plugins, packageScope).concat(corePlugins)
-  const filemap = new FilemapWithOutput({ packageScope, wd })
+  const staticDirs = ListItem.from(publicDirectory)
+  const filemap = new Filemap({ packageScope, staticDirs, wd })
+  const urlmap = new Urlmap({ packageScope, staticDirs })
   const cmd = 'build'
 
-  const factoryOptions = { plugins, filemap, cmd, env, settings, logger }
+  const factoryOptions = { plugins, filemap, urlmap, cmd, env, settings, logger }
   if (options.cache) factoryOptions.product = ProcessingWithCache
 
   const processingFactory = new ProcessingFactory(factoryOptions)
@@ -56,7 +60,7 @@ async function build (options, logger) {
 
   const cwd = process.cwd()
   for (const input of options._) {
-    const filepath = path.resolve(cwd, input)
+    const filepath = './' + path.relative(wd, path.resolve(cwd, input))
     const processing = processingFactory.resolve(filepath, fakeReferer)
     enqueue(processing)
   }
@@ -68,9 +72,9 @@ async function build (options, logger) {
   function enqueue (processing) {
     if (processing == null) return
 
-    const publicUrl = processing.publicUrl()
-    if (visited.has(publicUrl)) return
-    visited.add(publicUrl)
+    const id = processing.id
+    if (visited.has(id)) return
+    visited.add(id)
 
     q.push(processing)
   }
diff --git a/lib/cmd-serve.js b/lib/cmd-serve.js
index 5751c6c..30f0247 100644
--- a/lib/cmd-serve.js
+++ b/lib/cmd-serve.js
@@ -3,12 +3,12 @@
 const chokidar = require('chokidar')
 const fs = require('fs')
 const path = require('path')
-const { finished, pipeline } = require('stream')
 
-const { FilemapWithAliases } = require('./core-filemap-with-aliases')
+const { Filemap } = require('./core-filemap-serve')
+const { ListItem } = require('./core-data-structures')
 const { ProcessingFactory } = require('./core-processing-factory')
 const { ProcessingWithCache } = require('./core-processing-with-cache')
-const { UrlmapWithAliases } = require('./core-urlmap-with-aliases')
+const { Urlmap } = require('./core-urlmap')
 const { abc } = require('./util-hash')
 const { broadcast, createSocket } = require('./util-socket')
 const { contentType } = require('./util-mime-types')
@@ -18,6 +18,7 @@ const { debounce } = require('./util-scheduler')
 const { isFile } = require('./util-fs')
 const { loadCustomPlugins, loadPackageSettings } = require('./core-settings')
 const { nodeModules } = require('./core-resolve')
+const { pipe } = require('./util-stream')
 const { scope } = require('./util-scope')
 
 const corePlugins = [
@@ -37,7 +38,7 @@ async function serve (options, logger) {
   const packageScope = await scope(wd) ?? wd
   const settings = await loadPackageSettings(packageScope)
   const publicDirectory = path.join(packageScope, 'public')
-  const innerPublicDirectory = path.resolve(__dirname, '../public')
+  const internalDirectory = path.resolve(__dirname, '../public')
 
   logger.debug('environment variables %o', env)
   logger.debug('package settings %o', settings)
@@ -52,14 +53,15 @@ async function serve (options, logger) {
   const modulesDirs = nodeModules(path.dirname(packageScope))
   if (modulesDirs != null) {
     for (const directory of modulesDirs) {
-      const alias = `/~nm${abc(aliases.size)}`
+      const alias = `~nm${abc(aliases.size)}`
       aliases.set(alias, directory)
     }
   }
 
   const plugins = loadCustomPlugins(settings.wave?.plugins, packageScope).concat(corePlugins)
-  const filemap = new FilemapWithAliases({ aliases, packageScope, wd })
-  const urlmap = new UrlmapWithAliases({ aliases }); urlmap.cache = cache
+  const staticDirs = ListItem.from(publicDirectory)
+  const filemap = new Filemap({ aliases, packageScope, staticDirs, wd })
+  const urlmap = new Urlmap({ aliases, packageScope, staticDirs }); urlmap.cache = cache
   const cmd = 'serve'
 
   const factoryOptions = { plugins, filemap, urlmap, cmd, env, settings, logger }
@@ -70,8 +72,7 @@ async function serve (options, logger) {
   async function middleware (req, res) {
     const startTime = Date.now()
 
-    let url = new URL(req.url, `http://localhost:${port}/`).pathname
-    if (url.endsWith('/')) url += 'index.html'
+    const url = new URL(req.url, `http://localhost:${port}/`).pathname
 
     if (req.method !== 'GET') {
       res.writeHead(405, { allow: 'GET' })
@@ -79,6 +80,29 @@ async function serve (options, logger) {
       return
     }
 
+    if (url.startsWith('/-internal-/')) {
+      const internalFile = path.join(internalDirectory, url.substring(12))
+      if (await isFile(internalFile)) {
+        res.writeHead(200, {
+          'content-type': contentType(internalFile),
+          'server-timing': [
+            'internalFile',
+            `routing;dur=${Date.now() - startTime}`
+          ].join(', ')
+        })
+
+        pipe(fs.createReadStream(internalFile), res, err => {
+          if (err != null) handleRequestError(err, res)
+        })
+      } else {
+        // nothing to serve
+        res.writeHead(404, 'not found')
+        res.end()
+      }
+
+      return
+    }
+
     // serve project files and apply transformation if necessary
     const processing = processingFactory.resolve('.' + url, fakeReferer) // treat urls as relative paths
     if (processing != null) {
@@ -90,67 +114,13 @@ async function serve (options, logger) {
         ].join(', ')
       })
 
-      const streams = await processing.transform()
-      if (streams.length > 1) {
-        pipeline(
-          ...streams,
-          err => {
-            if (err != null) handleRequestError(err, res)
-          }
-        ).pipe(res)
-      } else {
-        finished(
-          streams[0].pipe(res),
-          err => {
-            if (err != null) handleRequestError(err, res)
-          }
-        )
-      }
-      return
-    }
-
-    // serve files from "public" directory
-    const publicFile = path.join(publicDirectory, url)
-    if (await isFile(publicFile)) {
-      res.writeHead(200, {
-        'content-type': contentType(publicFile),
-        'server-timing': [
-          'publicFile',
-          `routing;dur=${Date.now() - startTime}`
-        ].join(', ')
+      pipe(await processing.transform(), res, err => {
+        if (err != null) handleRequestError(err, res)
       })
 
-      finished(
-        fs.createReadStream(publicFile).pipe(res),
-        err => {
-          if (err != null) handleRequestError(err, res)
-        }
-      )
       return
     }
 
-    // serve development helpers from internal "public" directory
-    if (url.startsWith('/~/')) {
-      const innerFile = url.replace('/~', innerPublicDirectory)
-      if (await isFile(innerFile)) {
-        res.writeHead(200, {
-          'content-type': contentType(innerFile),
-          'server-timing': [
-            'internalFile',
-            `routing;dur=${Date.now() - startTime}`
-          ].join(', ')
-        })
-
-        finished(
-          fs.createReadStream(innerFile).pipe(res),
-          err => {
-            if (err != null) handleRequestError(err, res)
-          }
-        )
-        return
-      }
-    }
-
     // nothing to serve
     res.writeHead(404, 'not found')
     res.end()
diff --git a/lib/core-filemap-build.js b/lib/core-filemap-build.js
new file mode 100644
index 0000000..4ab5b5b
--- /dev/null
+++ b/lib/core-filemap-build.js
@@ -0,0 +1,44 @@
+'use strict'
+
+const path = require('path')
+
+const { IFilemap } = require('./core-filemap-i')
+const { extname } = require('./util-path')
+const { hash } = require('./util-hash')
+
+class Filemap extends IFilemap {
+  constructor (options) {
+    super(options)
+
+    this.packageScope = options.packageScope
+    this.staticDirs = options.staticDirs
+    this.wd = options.wd
+  }
+
+  map (abspath, referer) {
+    super.map(abspath, referer)
+
+    if (this.staticDirs != null) {
+      for (const directory of this.staticDirs) {
+        if (abspath.startsWith(directory)) return '/' + path.relative(directory, abspath)
+      }
+    }
+
+    const ext = extname(abspath)
+    const genericName = hash(path.relative(this.packageScope, abspath))
+
+    switch (ext) {
+      case '.html':
+        return '/' + path.relative(this.wd, abspath)
+      case '.css':
+      case '.js':
+        return '/' + path.join('static', ext.substring(1), genericName + ext)
+      default:
+        return '/' + path.join('static', 'media', genericName + ext)
+    }
+  }
+}
+
+module.exports = {
+  Filemap
+}
diff --git a/lib/core-filemap-i.js b/lib/core-filemap-i.js
new file mode 100644
index 0000000..c76f4a2
--- /dev/null
+++ b/lib/core-filemap-i.js
@@ -0,0 +1,14 @@
+'use strict'
+
+const assert = require('assert')
+
+class IFilemap {
+  map (abspath, referer, options) {
+    assert(typeof abspath === 'string')
+    return null
+  }
+}
+
+module.exports = {
+  IFilemap
+}
diff --git a/lib/core-filemap-serve.js b/lib/core-filemap-serve.js
new file mode 100644
index 0000000..cd748b5
--- /dev/null
+++ b/lib/core-filemap-serve.js
@@ -0,0 +1,68 @@
+'use strict'
+
+const path = require('path')
+
+const { IFilemap } = require('./core-filemap-i')
+const { hash } = require('./util-hash')
+const { foldLevels } = require('./util-path')
+
+const workdir = Symbol('workdir')
+
+class Filemap extends IFilemap {
+  constructor (options) {
+    super(options)
+
+    this.aliases = options.aliases
+    this.packageScope = options.packageScope
+    this.staticDirs = options.staticDirs
+    this.wd = options.wd
+
+    this[workdir] = path.relative(this.packageScope, this.wd)
+  }
+
+  map (abspath, referer) {
+    super.map(abspath, referer)
+
+    if (this.staticDirs != null) {
+      for (const directory of this.staticDirs) {
+        if (abspath.startsWith(directory)) return '/' + path.relative(directory, abspath)
+      }
+    }
+
+    const relative = path.relative(this.packageScope, abspath)
+
+    if (relative.startsWith(this[workdir])) {
+      return '/' + path.relative(this[workdir], relative)
+    }
+
+    if (relative.startsWith('../')) {
+      if (relative.includes('node_modules')) {
+        const base = abspath.substring(0, abspath.indexOf('node_modules') + 'node_modules'.length)
+        for (const [alias, directory] of this.aliases) {
+          if (base === directory) return '/' + path.join(alias, abspath.substring(base.length + 1))
+        }
+      }
+
+      return null
+    }
+
+    const right = foldLevels(path.relative(this[workdir], relative))
+    const middle = relative.substring(0, relative.lastIndexOf(right))
+
+    const alias = `~${hash(middle)}` // todo a readable solution
+    if (!this.aliases.has(alias)) {
+      const base = path.join(this.packageScope, middle.substring(0, middle.length - path.sep.length))
+      this.aliases.set(alias, base)
+    }
+
+    return '/' + path.join(alias, right)
+  }
+
+  output (relative) {
+    return relative
+  }
+}
+
+module.exports = {
+  Filemap
+}
diff --git a/lib/core-filemap-with-aliases.js b/lib/core-filemap-with-aliases.js
deleted file mode 100644
index 95cf3b5..0000000
--- a/lib/core-filemap-with-aliases.js
+++ /dev/null
@@ -1,52 +0,0 @@
-'use strict'
-
-const assert = require('assert')
-const path = require('path')
-
-const { Filemap } = require('./core-filemap')
-const { hash } = require('./util-hash')
-const { foldLevels } = require('./util-path')
-
-class FilemapWithAliases extends Filemap {
-  constructor (options) {
-    super(options)
-
-    assert(options.aliases != null)
-    this.aliases = options.aliases
-    assert(typeof options.packageScope === 'string')
-    this.packageScope = options.packageScope
-  }
-
-  map (abspath, referer, options) {
-    assert(typeof abspath === 'string')
-
-    if (abspath.startsWith(this.wd)) {
-      return super.map(abspath, referer, options)
-    }
-
-    if (abspath.startsWith(this.packageScope)) {
-      const middleRight = path.relative(this.packageScope, abspath)
-      const right = foldLevels(path.relative(this.wd, abspath))
-      const middle = middleRight.substring(0, middleRight.lastIndexOf(right))
-
-      const alias = `/~${hash(middle)}` // todo a readable solution
-      if (!this.aliases.has(alias)) {
-        const base = path.join(this.packageScope, middle.substring(0, middle.length - path.sep.length))
-        this.aliases.set(alias, base)
-      }
-
-      return path.join(alias, right)
-    }
-
-    if (abspath.includes('node_modules')) {
-      const base = abspath.substring(0, abspath.indexOf('node_modules') + 'node_modules'.length)
-      for (const [alias, directory] of this.aliases) {
-        if (base === directory) return path.join(alias, abspath.substring(base.length + 1))
-      }
-    }
-
-    return null
-  }
-}
-
-module.exports = { FilemapWithAliases }
diff --git a/lib/core-filemap-with-output.js b/lib/core-filemap-with-output.js
deleted file mode 100644
index b60a149..0000000
--- a/lib/core-filemap-with-output.js
+++ /dev/null
@@ -1,37 +0,0 @@
-'use strict'
-
-const assert = require('assert')
-const path = require('path')
-
-const { Filemap } = require('./core-filemap')
-const { hash } = require('./util-hash')
-
-class FilemapWithOutput extends Filemap {
-  constructor (options) {
-    super(options)
-
-    assert(typeof options.packageScope === 'string')
-    this.packageScope = options.packageScope
-  }
-
-  map (abspath, referer, options) {
-    assert(typeof abspath === 'string')
-
-    const ext = options?.extension ?? path.extname(abspath)
-    const genericName = hash(path.relative(this.packageScope, abspath))
-
-    switch (ext) {
-      case '.html':
-        return super.map(abspath, referer, options)
-      case '.css':
-      case '.js':
-        return path.join('/static', ext.substring(1), genericName + ext)
-      default:
-        return path.join('/static/media', genericName + ext)
-    }
-  }
-}
-
-module.exports = {
-  FilemapWithOutput
-}
diff --git a/lib/core-filemap.js b/lib/core-filemap.js
deleted file mode 100644
index 75a6845..0000000
--- a/lib/core-filemap.js
+++ /dev/null
@@ -1,36 +0,0 @@
-'use strict'
-
-const assert = require('assert')
-const path = require('path')
-
-const { extname } = require('./util-path')
-
-class Filemap {
-  constructor (options) {
-    assert(options.wd != null)
-    this.wd = options.wd
-  }
-
-  map (abspath, referer, options) {
-    assert(typeof abspath === 'string')
-
-    const customExtension = options?.extension
-    if (customExtension != null && !abspath.endsWith(customExtension)) {
-      abspath = path.join(
-        path.dirname(abspath),
-        path.basename(abspath, extname(abspath, true)) + customExtension
-      )
-    }
-
-    if (referer != null) {
-      const directory = path.dirname(referer)
-      if (abspath.startsWith(directory)) return './' + path.relative(directory, abspath)
-    }
-
-    return '/' + path.relative(this.wd, abspath)
-  }
-}
-
-module.exports = {
-  Filemap
-}
diff --git a/lib/core-processing-factory.js b/lib/core-processing-factory.js
index 05fb78f..4e6462e 100644
--- a/lib/core-processing-factory.js
+++ b/lib/core-processing-factory.js
@@ -4,22 +4,35 @@ const assert = require('assert')
 const { inspect } = require('util')
 
 const { ILogger } = require('./util-logger-i')
+const { IUrlmap } = require('./core-urlmap-i')
 const { Processing } = require('./core-processing')
-const { Urlmap } = require('./core-urlmap')
 const { extname } = require('./util-path')
 
 const customInspect = inspect.custom ?? 'inspect'
 
 class ProcessingFactory {
+  static validatePlugin (plugin) {
+    assert(typeof plugin.type === 'string' && plugin.type.length > 0)
+    if (!Array.isArray(plugin.extensions)) throw new Error(`plugin "${plugin.type}": "extensions" should be an array of file extensions that can be used as input`)
+    if (typeof plugin.for !== 'string') throw new Error(`plugin "${plugin.type}": "for" should be an extension for an output file`)
+    if (typeof plugin.transform !== 'function') throw new Error(`plugin "${plugin.type}": "transform" should be a function`)
+
+    if (plugin.type !== 'identity') {
+      assert(plugin.extensions.every(ext => ext !== ''))
+      assert(plugin.for !== '')
+    }
+  }
+
   constructor (options) {
     // mandatory for resolve
-    assert(Array.isArray(options.plugins)) // properly validate plugins
+    assert(Array.isArray(options.plugins))
+    for (const plugin of options.plugins) ProcessingFactory.validatePlugin(plugin)
     this.plugins = options.plugins
     this.product = options.product ?? Processing
 
     // required for processing
     this.filemap = options.filemap
-    this.urlmap = options.urlmap ?? new Urlmap()
+    this.urlmap = options.urlmap ?? new IUrlmap()
     this.cmd = options.cmd
     this.env = options.env
     this.settings = options.settings
@@ -31,6 +44,8 @@ class ProcessingFactory {
     assert(typeof url === 'string')
     assert(typeof referer === 'string')
 
+    if (url.endsWith('/')) url += 'index.html'
+
     const ext = extname(url) ?? extname(referer)
     const matchingPlugins = this.plugins.filter(plugin => plugin.for === ext || plugin.for === '')
 
@@ -41,7 +56,11 @@ class ProcessingFactory {
       const abspath = this.urlmap.map(url, referer)
       if (abspath == null) continue
 
+      // first plugin that may apply custom transformation,
+      // for example ".md" → ".html"
       const plugins = [plugin]
+      // other plugins that can be applied after,
+      // should have a matching extension among "extensions".
       for (let k = n + 1; k < matchingPlugins.length; ++k) {
         const nextPlugin = matchingPlugins[k]
         if (nextPlugin.extensions.includes(ext)) plugins.push(nextPlugin)
@@ -51,12 +70,12 @@ class ProcessingFactory {
       const processingOptions = { url, abspath, plugins, filemap, cmd, env, settings }
       const processing = new Product(processingOptions, this)
 
-      this.logger.debug({ url, referer, abspath }, 'url resolved')
+      this.logger.debug('resolve completed %o', { url, referer, abspath })
 
       return processing
     }
 
-    this.logger.debug({ url, referer }, 'url not resolved')
+    this.logger.debug('resolve errored %o', { url, referer })
 
     return null
   }
diff --git a/lib/core-processing.js b/lib/core-processing.js
index 4df535e..ce86ea9 100644
--- a/lib/core-processing.js
+++ b/lib/core-processing.js
@@ -1,6 +1,7 @@
 'use strict'
 
 const fs = require('fs')
+const path = require('path')
 const { inspect } = require('util')
 const { pipeline } = require('stream/promises')
 
@@ -9,6 +10,7 @@ const { createBufferStream, createTransformStream } = require('./util-stream')
 const { extname } = require('./util-path')
 
 const customInspect = inspect.custom ?? 'inspect'
+const internal = /^\/-internal-\//
 const protocol = /^[a-z]{2,6}:\/\//i
 
 const context = Symbol('context')
@@ -33,9 +35,25 @@ class Processing {
     this[factory] = processingFactory
   }
 
-  publicUrl () {
-    const options = { extension: extname(this.url) }
-    return this.filemap.map(this.abspath, null, options)
+  get id () {
+    return this.publicUrl()
+  }
+
+  publicUrl (referer) {
+    const ext = extname(this.url) ?? extname(this.abspath)
+    const request = !this.abspath.endsWith(ext)
+      ? path.join(
+          path.dirname(this.abspath),
+          path.basename(this.abspath, extname(this.abspath, true)) + ext
+        )
+      : this.abspath
+
+    const url = this.filemap.map(request, null)
+    if (url.endsWith('index.html') && referer != null) {
+      return url.substring(0, url.length - 'index.html'.length)
+    }
+
+    return url
   }
 
   resolve (url, options) {
@@ -49,23 +67,26 @@ class Processing {
   }
 
   requestDependency (url) {
+    if (internal.test(url)) throw new Error('requestDependency does not handle internal files')
     if (protocol.test(url)) throw new Error('requestDependency does not support urls')
 
     const dependency = this.resolve(url, { captureDependency: false })
-    if (dependency) return null
+    if (dependency == null) return null
 
     const bufferStream = createBufferStream()
-    return pipeline(...dependency.transform(), bufferStream)
+    return dependency.transform()
+      .then(streams => pipeline(...streams, bufferStream))
       .then(() => bufferStream.buffer.toString('utf8'))
   }
 
   resolveDependency (url) {
+    if (internal.test(url)) return url
     if (protocol.test(url)) return url
 
     const dependency = this.resolve(url, { captureDependency: true })
     if (dependency == null) console.log('can not resolve', url)
 
-    return dependency?.publicUrl() ?? url
+    return dependency?.publicUrl(this.abspath) ?? url
   }
 
   async transform () {
diff --git a/lib/core-resolve.js b/lib/core-resolve.js
index a455a04..9e66a9f 100644
--- a/lib/core-resolve.js
+++ b/lib/core-resolve.js
@@ -111,5 +111,7 @@ function resolveUrl (url, referer, options) {
 
 module.exports = {
   nodeModules,
+  resolveAsFile,
+  resolveAsDirectory,
   resolveUrl
 }
diff --git a/lib/core-urlmap-i.js b/lib/core-urlmap-i.js
new file mode 100644
index 0000000..999ab41
--- /dev/null
+++ b/lib/core-urlmap-i.js
@@ -0,0 +1,15 @@
+'use strict'
+
+const assert = require('assert')
+
+class IUrlmap {
+  map (url, referer) {
+    assert(typeof url === 'string')
+    assert(typeof referer === 'string')
+    return null
+  }
+}
+
+module.exports = {
+  IUrlmap
+}
diff --git a/lib/core-urlmap-with-aliases.js b/lib/core-urlmap-with-aliases.js
deleted file mode 100644
index 2104837..0000000
--- a/lib/core-urlmap-with-aliases.js
+++ /dev/null
@@ -1,41 +0,0 @@
-'use strict'
-
-const assert = require('assert')
-const path = require('path')
-
-const { Urlmap } = require('./core-urlmap')
-const { resolveUrl } = require('./core-resolve')
-
-const isAlias = /\/~[a-z]+/i
-
-class UrlmapWithAliases extends Urlmap {
-  constructor (options) {
-    super(options)
-
-    assert(options.aliases != null)
-    this.aliases = options.aliases
-  }
-
-  map (url, referer) {
-    assert(typeof url === 'string')
-    assert(typeof referer === 'string')
-
-    if (isAlias.test(url)) {
-      const offset = url.startsWith('./') ? 1 : 0
-      const alias = url.substring(offset, url.indexOf('/', offset + 1))
-
-      if (this.aliases.has(alias)) {
-        url = path.join(this.aliases.get(alias), url.substring(offset + alias.length + 1))
-
-        const options = { extensions: this.extensions }
-        return resolveUrl(url, referer, options)
-      }
-    }
-
-    return super.map(url, referer)
-  }
-}
-
-module.exports = {
-  UrlmapWithAliases
-}
diff --git a/lib/core-urlmap.js b/lib/core-urlmap.js
index 60703f9..27b5c6e 100644
--- a/lib/core-urlmap.js
+++ b/lib/core-urlmap.js
@@ -1,21 +1,72 @@
 'use strict'
 
-const assert = require('assert')
+const path = require('path')
 
+const { IUrlmap } = require('./core-urlmap-i')
 const { ListItem } = require('./core-data-structures')
+const { isFileSync } = require('./util-fs')
 const { resolveUrl } = require('./core-resolve')
 
-class Urlmap {
-  constructor () {
+class Urlmap extends IUrlmap {
+  static isAliasPath (url) {
+    return /^(?:\.\/)?~[a-z0-9]+/i.test(url)
+  }
+
+  static isRootPath (url) {
+    return (
+      url.startsWith('./~/') ||
+      url.startsWith('~/')
+    )
+  }
+
+  constructor (options) {
+    super(options)
+
+    this.aliases = options.aliases
     this.cache = null
     this.extensions = ListItem.from('')
+    this.packageScope = options.packageScope
+    this.staticDirs = options.staticDirs
   }
 
   map (url, referer) {
-    assert(typeof url === 'string')
-    assert(typeof referer === 'string')
+    super.map(url, referer)
+
+    // resolved aliases or package path will start from "/~",
+    // thus turn it into "./~" to properly resolve it
+    if (url.startsWith('/~')) url = '.' + url
 
     const options = { cache: this.cache, extensions: this.extensions }
+
+    if (url.startsWith('/')) {
+      const abspath = resolveUrl(url, referer, options)
+      if (abspath != null) return abspath
+
+      if (this.staticDirs != null) {
+        for (const directory of this.staticDirs) {
+          const staticPath = path.join(directory, url)
+          if (isFileSync(staticPath)) return staticPath
+        }
+      }
+
+      return null
+    }
+
+    if (Urlmap.isAliasPath(url)) {
+      const offset = url.indexOf('~')
+      const alias = url.substring(offset, url.indexOf('/', offset))
+
+      if (this.aliases.has(alias)) {
+        url = path.join(this.aliases.get(alias), url.substring(offset + alias.length + 1))
+      }
+    }
+
+    if (Urlmap.isRootPath(url)) {
+      const offset = url.indexOf('~/')
+      const base = url.substring(offset + 2)
+      url = path.join(this.packageScope, base)
+    }
+
     return resolveUrl(url, referer, options)
   }
 }
diff --git a/lib/util-stream.js b/lib/util-stream.js
index 80e9c8b..72a9ba1 100644
--- a/lib/util-stream.js
+++ b/lib/util-stream.js
@@ -1,7 +1,7 @@
 'use strict'
 
 const assert = require('assert')
-const { PassThrough, Transform } = require('stream')
+const { PassThrough, Transform, finished, pipeline } = require('stream')
 
 function createBufferStream () {
   const bufferStream = new Transform({
@@ -39,16 +39,20 @@ function createTransformStream (tf, context) {
   })
 }
 
-function pipe (...streams) {
-  if (streams.length === 0) return null
-
-  let cursor = streams[0]
-  for (let i = 1; i < streams.length; i++) {
-    const stream = streams[i]
-    cursor = cursor.pipe(stream)
+function pipe (streams, destination, callback) {
+  if (!Array.isArray(streams)) {
+    finished(
+      streams.pipe(destination),
+      callback
+    )
+  } else if (streams.length === 1) {
+    finished(
+      streams[0].pipe(destination),
+      callback
+    )
+  } else {
+    pipeline(...streams, callback).pipe(destination)
   }
-
-  return streams[0]
 }
 
 function tee (output) {
diff --git a/package.json b/package.json
index 01b4b10..379c952 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "under-the-wave",
-  "version": "1.3.5",
+  "version": "1.3.6",
   "bin": {
     "under-the-wave": "./lib/bin.js",
     "wave": "./lib/bin.js"
diff --git a/plugins/p-markdown.js b/plugins/p-markdown.js
index 82f2460..e9c9d29 100644
--- a/plugins/p-markdown.js
+++ b/plugins/p-markdown.js
@@ -21,13 +21,18 @@ function transformMarkdownPlugin (string, context, done) {
     return
   }
 
-  context.request(meta.layout)
-    .then(buffer => {
-      const template = buffer.toString('utf8')
-      // keep in mind that matching html plugins will be applied one more time after,
-      // thus some plugins may be applied twice
-      return posthtml(markdownPlugin(meta.__content)).process(template)
-    })
+  const file = context.request(meta.layout)
+  if (file == null) {
+    done(new Error('request failed for "' + meta.layout + '"'))
+    return
+  }
+
+  file.then(buffer => {
+    const template = buffer.toString('utf8')
+    // keep in mind that matching html plugins will be applied one more time after,
+    // thus some plugins may be applied twice
+    return posthtml(markdownPlugin(meta.__content)).process(template)
+  })
     .then(result => done(null, result.html), done)
 }
 
diff --git a/plugins/p-style.js b/plugins/p-style.js
index 793fae7..ca70a2b 100644
--- a/plugins/p-style.js
+++ b/plugins/p-style.js
@@ -6,8 +6,9 @@ const updateAssetPathStylePlugin = require('./t-style-update-asset-path')
 
 module.exports = {
   extensions: ['.css'],
-  type: 'css',
-  transform: transformStyleCorePlugin
+  for: '.css',
+  transform: transformStyleCorePlugin,
+  type: 'style'
 }
 
 function transformStyleCorePlugin (string, context, done) {
diff --git a/plugins/t-markup-inject-bridge.js b/plugins/t-markup-inject-bridge.js
index 8d2f180..2c2cf01 100644
--- a/plugins/t-markup-inject-bridge.js
+++ b/plugins/t-markup-inject-bridge.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const bridgeUrl = '/~/bridge.js'
+const bridgeUrl = '/-internal-/bridge.js'
 const indent = /^[\n\s]+$/
 
 const scriptNode = {
diff --git a/tests/core-filemap-with-aliases.test.js b/tests/core-filemap-with-aliases.test.js
deleted file mode 100644
index a0fd91f..0000000
--- a/tests/core-filemap-with-aliases.test.js
+++ /dev/null
@@ -1,20 +0,0 @@
-'use strict'
-
-const assert = require('uvu/assert')
-const { test } = require('uvu')
-
-const { FilemapWithAliases } = require('../lib/core-filemap-with-aliases')
-
-const packageScope = '/www'
-const wd = '/www/pages'
-
-test('FilemapWithAliases.map', () => {
-  const aliases = new Map()
-  const filemap = new FilemapWithAliases({ aliases, packageScope, wd })
-
-  assert.is(filemap.map('/www/lib/abc.js'), '/~hldurme/abc.js')
-  assert.is(filemap.map('/www/lib/utils.js'), '/~hldurme/utils.js')
-  assert.is(filemap.map('/www/static/css/tachyons.css'), '/~jdrquyi/css/tachyons.css')
-})
-
-test.run()
diff --git a/tests/core-filemap.test.js b/tests/core-filemap.test.js
deleted file mode 100644
index 688199e..0000000
--- a/tests/core-filemap.test.js
+++ /dev/null
@@ -1,16 +0,0 @@
-'use strict'
-
-const assert = require('uvu/assert')
-const { test } = require('uvu')
-
-const { Filemap } = require('../lib/core-filemap')
-
-test('IFilemap.map', () => {
-  const filemap = new Filemap({ wd: '/www' })
-  // map file to url
-  assert.is(filemap.map('/www/index.html'), '/index.html')
-  // map file to relative url
-  assert.is(filemap.map('/www/static/js/app.js', '/www/index.html'), './static/js/app.js')
-})
-
-test.run()
diff --git a/tests/core-processing-factory.test.js b/tests/core-processing-factory.test.js
index ab68509..649bb3f 100644
--- a/tests/core-processing-factory.test.js
+++ b/tests/core-processing-factory.test.js
@@ -4,16 +4,27 @@ const assert = require('uvu/assert')
 const path = require('path')
 const { test } = require('uvu')
 
+const { ListItem } = require('../lib/core-data-structures')
 const { ProcessingFactory } = require('../lib/core-processing-factory')
 const { Processing } = require('../lib/core-processing')
+const { resolveAsFile } = require('../lib/core-resolve')
 
 const projectRoot = path.resolve(__dirname, 'fixture')
 const referer = path.join(projectRoot, 'index.html')
 
+const urlmap = {
+  extensions: ListItem.from(''),
+  map (url, referer) {
+    const abspath = path.join(path.dirname(referer), url)
+    const options = { extensions: this.extensions }
+    if (resolveAsFile(abspath, options)) return abspath
+    return null
+  }
+}
+
 test('ProcessingFactory.create returns processing instance', () => {
   const plugins = [require('../plugins/p-identity')]
-  const processingFactory = new ProcessingFactory({ plugins })
-  processingFactory.cmd = 'test'
+  const processingFactory = new ProcessingFactory({ plugins, urlmap })
 
   const processing = processingFactory.resolve('./static/hello.js', referer)
 
@@ -25,8 +36,7 @@ test('ProcessingFactory.create returns processing instance', () => {
 
 test('ProcessingFactory.create maps ".html" file to ".md"', () => {
   const plugin = require('../plugins/p-markdown')
-  const processingFactory = new ProcessingFactory({ plugins: [plugin] })
-  processingFactory.cmd = 'test'
+  const processingFactory = new ProcessingFactory({ plugins: [plugin], urlmap })
 
   assert.not.ok(plugin.extensions.includes(plugin.for))
   assert.instance(processingFactory.resolve('./readme.html', referer), Processing)
diff --git a/tests/core-urlmap-with-aliases.test.js b/tests/core-urlmap-with-aliases.test.js
deleted file mode 100644
index 9d09c03..0000000
--- a/tests/core-urlmap-with-aliases.test.js
+++ /dev/null
@@ -1,21 +0,0 @@
-'use strict'
-
-const assert = require('uvu/assert')
-const path = require('path')
-const { test } = require('uvu')
-
-const { UrlmapWithAliases } = require('../lib/core-urlmap-with-aliases')
-
-const projectRoot = path.resolve(__dirname, 'fixture')
-const referer = path.join(projectRoot, '_')
-const output = path.join(projectRoot, 'index.html')
-
-test('Urlmap.map "./x" path', () => {
-  const aliases = new Map()
-  const urlmap = new UrlmapWithAliases({ aliases })
-
-  aliases.set('/~w', projectRoot)
-  assert.is(urlmap.map('/~w/index.html', referer), output)
-})
-
-test.run()
diff --git a/tests/core-urlmap.test.js b/tests/core-urlmap.test.js
index 1eea474..af5d713 100644
--- a/tests/core-urlmap.test.js
+++ b/tests/core-urlmap.test.js
@@ -4,20 +4,58 @@ const assert = require('uvu/assert')
 const path = require('path')
 const { test } = require('uvu')
 
+const { ListItem } = require('../lib/core-data-structures')
 const { Urlmap } = require('../lib/core-urlmap')
 
-const projectRoot = path.resolve(__dirname, 'fixture')
-const referer = path.join(projectRoot, '_')
-const output = path.join(projectRoot, 'index.html')
+const packageScope = path.resolve(__dirname, 'fixture')
+const referer = path.join(packageScope, '_')
+
+const output = path.join(packageScope, 'index.html')
 
 test('Urlmap.map "./x" path', () => {
-  const urlmap = new Urlmap()
+  const aliases = new Map()
+  const urlmap = new Urlmap({ aliases, packageScope })
 
   assert.is(urlmap.map('./index.html', referer), output)
 })
 
+test('Urlmap.map "/x" path', () => {
+  const aliases = new Map()
+  const urlmap = new Urlmap({ aliases, packageScope })
+
+  assert.is(urlmap.map(output, referer), output)
+})
+
+test('Urlmap.map "~/x" path', () => {
+  const aliases = new Map()
+  const urlmap = new Urlmap({ aliases, packageScope })
+
+  assert.is(urlmap.map('./~/index.html', referer), output)
+  assert.is(urlmap.map('~/index.html', referer), output)
+})
+
+test('Urlmap.map "~st/x" path', () => {
+  const aliasPath = path.join(packageScope, 'static')
+  const aliases = new Map([['~st', aliasPath]])
+  const output = path.join(packageScope, 'static/hello.js')
+  const urlmap = new Urlmap({ aliases, packageScope })
+
+  assert.is(urlmap.map('./~st/hello.js', referer), output)
+  assert.is(urlmap.map('~st/hello.js', referer), output)
+})
+
+test('Urlmap.map → public file', () => {
+  const aliases = new Map()
+  const staticDirs = ListItem.from(path.join(packageScope, 'public'))
+  const output = path.join(packageScope, 'public/robots.txt')
+  const urlmap = new Urlmap({ aliases, packageScope, staticDirs })
+
+  assert.is(urlmap.map('/robots.txt', referer), output)
+})
+
 test('Urlmap.map → "null" for not existing file', () => {
-  const urlmap = new Urlmap()
+  const aliases = new Map()
+  const urlmap = new Urlmap({ aliases, packageScope })
 
   assert.is(urlmap.map('./unknown.html', referer), null)
 })
diff --git a/tests/t-markup-inject-bridge.test.js b/tests/t-markup-inject-bridge.test.js
index 08d25b3..ae0934b 100644
--- a/tests/t-markup-inject-bridge.test.js
+++ b/tests/t-markup-inject-bridge.test.js
@@ -21,7 +21,7 @@ test('inject bridge script into head', async () => {
     <html lang="en">
       <head>
         <meta charset="UTF-8">
-        <script type="module" src="/~/bridge.js" async></script>
+        <script type="module" src="/-internal-/bridge.js" async></script>
       </head>
       <body></body>
     </html>
@@ -45,7 +45,7 @@ test('inject bridge script into minified head', async () => {
   const expected = `
     <!DOCTYPE html>
     <html lang="en">
-      <head><meta charset="UTF-8"><script type="module" src="/~/bridge.js" async></script></head>
+      <head><meta charset="UTF-8"><script type="module" src="/-internal-/bridge.js" async></script></head>
       <body></body>
     </html>
   `