diff --git a/ScrollSetCLI.js b/ScrollSetCLI.js
index 3f8d769da..65fceef9f 100644
--- a/ScrollSetCLI.js
+++ b/ScrollSetCLI.js
@@ -6,7 +6,6 @@ const { Utils } = require("scrollsdk/products/Utils.js")
 const { Disk } = require("scrollsdk/products/Disk.node.js")
 const { ScrollCli } = require("./scroll.js")
 const scrollFs = new ScrollCli().sfs
-const ScrollFile = scrollFs.defaultFileClass
 
 class ScrollSetCLI {
   constructor() {
@@ -57,7 +56,7 @@ class ScrollSetCLI {
   }
 
   async _formatAndSave(filePath, particle) {
-    const fusedFile = new ScrollFile(particle.toString(), filePath, scrollFs)
+    const fusedFile = scrollFs.newFile(particle.toString(), filePath)
     await fusedFile.fuse()
     // force a write
     const result = await scrollFs.write(filePath, fusedFile.scrollProgram.formatted)
diff --git a/package.json b/package.json
index 9b6a81b39..135c90bc6 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "scroll-cli",
-  "version": "176.0.1",
+  "version": "177.0.0",
   "description": "A language for scientists of all ages. A curated collection of tools for refining and sharing thoughts.",
   "main": "scroll.js",
   "engines": {
@@ -53,7 +53,7 @@
     "lodash": "^4.17.21",
     "minimist": "^1.2.5",
     "scroll-cli": "^170.2.0",
-    "scrollsdk": "^106.0.1"
+    "scrollsdk": "^107.0.0"
   },
   "devDependencies": {
     "prettier": "^2.8.8",
diff --git a/parsers/assertions.parsers b/parsers/assertions.parsers
index f2208390e..b43f2a983 100644
--- a/parsers/assertions.parsers
+++ b/parsers/assertions.parsers
@@ -9,11 +9,11 @@ abstractAssertionParser
     // If the previous particle is also an assertion particle, use the one before that.
     return this.previous.particleToTest ? this.previous.particleToTest : this.previous
   }
-  get format() { return "html"}
+  get outputFormat() { return "html"}
   get actual() {
-    let {format} = this
-    format = format.substr(0, 1).toUpperCase() + format.substr(1)
-    const methodName = `build${format}`
+    let {outputFormat} = this
+    outputFormat = outputFormat.substr(0, 1).toUpperCase() + outputFormat.substr(1)
+    const methodName = `build${outputFormat}`
     return this.particleToTest[methodName]()
    }
   getErrors() {
@@ -53,7 +53,7 @@ assertParser
   Hello
   assert txt includes Hello
  javascript
-  get format() {
+  get outputFormat() {
     return this.atoms[1]
   }
   get expected() {
@@ -92,6 +92,18 @@ assertBuildIncludesParser
   }
   get actual() { return this.particleToTest.buildOutput()}
 
+assertBuildEndsWithParser
+ extends assertBuildIncludesParser
+ string kind endsWith
+ example
+  buildCsv
+  assertBuildEndsWith virginica
+ javascript
+  areEqual(actual, expected) {
+    // Note that this does do a trim on both.
+    return actual.trim().endsWith(expected.trim())
+  }
+
 assertHtmlIncludesParser
  extends abstractAssertionParser
  string kind include
diff --git a/parsers/atomTypes.parsers b/parsers/atomTypes.parsers
index 0a7c07f5f..459966350 100644
--- a/parsers/atomTypes.parsers
+++ b/parsers/atomTypes.parsers
@@ -16,9 +16,9 @@ countAtom
 yearAtom
  extends integerAtom
 
-preBuildCommandAtom
+parseTimeCommandAtom
  extends cueAtom
- description Give build command atoms their own color.
+ description Give parse time command atoms their own color.
  paint constant.character.escape
 
 delimiterAtom
diff --git a/parsers/code.parsers b/parsers/code.parsers
index a75248754..6fda85af4 100644
--- a/parsers/code.parsers
+++ b/parsers/code.parsers
@@ -34,10 +34,13 @@ codeWithHeaderParser
    two = 1 + 1
  javascript
   buildHtml() {
-   return `<div class="codeWithHeader"><div class="codeHeader">${this.content}</div>${super.buildHtml()}</div>`
+   return `<div class="codeWithHeader"><div class="codeHeader">${this.header}</div>${super.buildHtml()}</div>`
   }
   buildTxt() {
-    return "```" + this.content + "\n" + this.code + "\n```"
+    return "```" + this.header + "\n" + this.code + "\n```"
+  }
+  get header() {
+    return this.content
   }
 
 codeFromFileParser
diff --git a/parsers/concepts.parsers b/parsers/concepts.parsers
index 93ea2f8d4..f3cce09d3 100644
--- a/parsers/concepts.parsers
+++ b/parsers/concepts.parsers
@@ -16,17 +16,52 @@ scrollConceptsParser
 
 loadConceptsParser
  // todo: clean this up. just add smarter imports with globs?
- // this currently removes any "import" statements.
+ // this currently removes first line of each (to ditch the imports).
  description Import all concepts in a folder.
- extends abstractBuildCommandParser
+ extends abstractScrollParser
  cueFromId
- atoms preBuildCommandAtom filePathAtom
+ atoms parseTimeCommandAtom filePathAtom
  javascript
-  async load() {
-   const { Disk, path, importRegex } = this.root
+  async wake() {
+   const { Disk, path } = this.root
    const folder = path.join(this.root.folderPath, this.getAtom(1))
-   const ONE_BIG_FILE = Disk.getFiles(folder).filter(file => file.endsWith(".scroll")).map(Disk.read).join("\n\n").replace(importRegex, "")
-    this.parent.concat(ONE_BIG_FILE)
+   const ONE_BIG_FILE = Disk.getFiles(folder).filter(file => file.endsWith(".scroll")).map(Disk.read).map(content => content.split("\n").slice(1).join("\n")).join("\n\n")
+   this.parent.concat(ONE_BIG_FILE)
+  }
+
+conceptTemplateParser
+ extends abstractScrollParser
+ description Loads a template after document is parsed.
+ example
+  conceptTemplate
+   # This is a page for {name}
+   His phone is {phone}
+ cueFromId
+ javascript
+  async wake() {
+    this.root.notifyOnReady(this)
+  }
+  onReady() {
+    if (this.root.has("importOnly")) return // Don't run on import only pages.
+    const concept = this.root.concept
+    const templateString = new Particle(this.subparticlesToString())
+    const newCode = templateString.templateToString(concept)
+    this.replaceWith(newCode)
+  }
+
+dumpConceptParser
+ popularity 0.000169
+ cueFromId
+ atoms cueAtom
+ extends codeWithHeaderParser
+ example
+  dumpConcept
+ javascript
+  get code() {
+    return new Particle(this.root.concept).toString()
+  }
+  get header() {
+    return this.root.filename
   }
 
 buildConceptsParser
@@ -46,7 +81,7 @@ buildConceptsParser
     return this.get("sortBy")
   }
   get outputFiles() {
-    const {permalink} = this
+    const {permalink} = this.root
     const files = this.getAtomsFrom(1)
     if (!files.length) files.push(permalink.replace(".html", ".csv"))
     return files
diff --git a/parsers/debug.parsers b/parsers/debug.parsers
index a2feebb98..740441064 100644
--- a/parsers/debug.parsers
+++ b/parsers/debug.parsers
@@ -28,18 +28,13 @@ debugSourceStackParser
   }
 
 debugParsersParser
- description Print the parsers used.
+ description Print source code of all parsers used.
  extends codeParser
  cueFromId
  javascript
   buildParsers() { return this.code}
   get code() {
-    let code = new Particle(this.root.definition.toString())
-      // Remove comments
-    code.filter((line) => line.getLine().startsWith("//")).forEach((particle) => particle.destroy())
-    // Remove blank lines
-    code = code.toString().replace(/^\n/gm, "")
-    return code
+    return this.root.definition.toString()
   }
 
 debugBelowParser
diff --git a/parsers/dinkus.parsers b/parsers/dinkus.parsers
index dffaf1ee5..680db25e8 100644
--- a/parsers/dinkus.parsers
+++ b/parsers/dinkus.parsers
@@ -38,6 +38,7 @@ scrollDinkusParser
 customDinkusParser
  cue dinkus
  description A custom dinkus.
+ atoms cueAtom stringAtom
  extends abstractDinkusParser
 
 endOfPostDinkusParser
diff --git a/parsers/fetch.parsers b/parsers/fetch.parsers
index 7b98655ea..2d07d092a 100644
--- a/parsers/fetch.parsers
+++ b/parsers/fetch.parsers
@@ -2,7 +2,7 @@ fetchParser
  description Download URL to disk.
  extends abstractBuildCommandParser
  cueFromId
- atoms preBuildCommandAtom urlAtom
+ atoms parseTimeCommandAtom urlAtom
  example
   fetch https://breckyunits.com/posts.csv
   fetch https://breckyunits.com/posts.csv renamed.csv
diff --git a/parsers/format.parsers b/parsers/format.parsers
new file mode 100644
index 000000000..f78aad2b3
--- /dev/null
+++ b/parsers/format.parsers
@@ -0,0 +1,5 @@
+scrollNoFormatParser
+ description Don't format below this line.
+ cue noFormat
+ atoms parseTimeCommandAtom
+ extends abstractTopLevelSingleMetaParser
\ No newline at end of file
diff --git a/parsers/import.parsers b/parsers/import.parsers
index 373ed1729..741011fbc 100644
--- a/parsers/import.parsers
+++ b/parsers/import.parsers
@@ -2,21 +2,112 @@ importParser
  description Import a file.
  popularity 0.007524
  cueFromId
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  extends abstractScrollParser
  catchAllAtomType filePathAtom
+ int filenameAt 1
  example
   import header.scroll
+ javascript
+  get filename() {
+    return this.getAtom(this.filenameAt)
+  }
+  get fullpath() {
+    const {fileSystem, filePath} = this.root
+    return fileSystem.makeRelativePath(filePath, this.filename)
+  }
+  async wake() {
+    const {fullpath} = this
+    const {file} = this.root
+    if (!file.importsFiles)
+     file.importsFiles = new Set()
+    file.importsFiles.add(fullpath)
+    return await this._handleImport()
+  }
+  async _handleImport() {
+    const hasCircular = await this._hasCircularImports(this.root.filePath, this.fullpath)
+    if (hasCircular)
+      return await this._handleCircularImport(hasCircular)
+    const file = await this._getFile()
+    const particleCount = file.scrollProgram.length
+    if (!file.exists)
+      return await this._handleFileDoesNotExist()
+    const newParticle = new Particle(`imported ${this.fullpath}\n exists true\n original ${this.getLine()}\n particles ${particleCount}`)
+    if (this.has("moveToFooter"))
+      newParticle.particleAt(0).set("moveToFooter", "true")
+    await this.root.appendFromStream(newParticle.toString())
+    // Don't import importOnly lines
+    // todo: look at perf
+    const block = new Particle(file.scrollProgram.toString())
+    block.delete("importOnly")
+    await this.root.appendFromStream(block.toString())
+    this.destroy()
+  }
+  async _handleFileDoesNotExist() {
+    const newParticle = new Particle(`imported ${this.fullpath}\n exists false\n original ${this.getLine()}\n particles 0`)
+    await this.root.appendFromStream(newParticle.toString())
+    this.destroy()
+  }
+  async _handleCircularImport(hasCircular) {
+    const newParticle = new Particle(`imported ${this.fullpath}\n exists true\n original ${this.getLine()}\n particles 0\n circularImportError Circular import error: ${hasCircular}`)
+    await this.root.appendFromStream(newParticle.toString())
+    this.destroy()
+  }
+  async _hasCircularImports(importer, importee) {
+    // if a.scroll requires a.scroll
+    if (importer === importee)
+      return `${importee} imports itself`
+    const {fileSystem} = this.root
+    // Now check the files that the importee is importing
+    const importeeFile = await fileSystem.getFile(importee)
+    if (!importeeFile.importsFiles)
+      return false
+    if (importeeFile.importsFiles.has(importer))
+      return `${importee} imports ${importer}`
+    for (let importPath of importeeFile.importsFiles) {
+      // console.log(`Checking if ${importPath} imports ${importer}`)
+      if (await this._hasCircularImports(importPath, importer))
+        return `${importPath} and ${importer}`
+    }
+    return false
+  }
+  async _getFile() {
+    const {fileSystem, file} = this.root
+    const fileToImport = await fileSystem.getFile(this.fullpath)
+    await fileToImport.singlePassFuse()
+    return fileToImport
+  }
 
 scrollImportedParser
  description Inserted at import pass.
  boolean suggestInAutocomplete false
  cue imported
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  extends abstractScrollParser
  baseParser blobParser
  catchAllAtomType filePathAtom
  javascript
+  async wake() {
+    this.checkForFooterMoves()
+  }
+  get dependencies() { return [this.atoms[1]]}
+  checkForFooterMoves() {
+    // If a particle was imported with the "moveToFooter" subparticle set, then that means we want
+    // to move those imported particles to the end of the document.
+    if (!this.has("moveToFooter"))
+      return
+    this.root.notifyOnReady(this)
+  }
+  onReady() {
+    // We move the imported particle along with the number of lines originally imported
+    // to the bottom of the document. Note: I have not looked into perf yet.
+    const particleCount = parseInt(this.get("particles"))
+    const index = this.index
+    const particles = this.root.slice(index, index + particleCount + 1)
+    const str = particles.map(part => part.toString()).join("\n")
+    this.root.appendBlocks(str)
+    particles.forEach(particle => particle.destroy())
+  }
   getErrors() {
     if (this.has("circularImportError"))
       return [this.makeError(this.get("circularImportError"))]
@@ -27,26 +118,56 @@ scrollImportedParser
 
 importToFooterParser
  description Import to bottom of file.
- atoms preBuildCommandAtom
- cue footer
+ atoms parseTimeCommandAtom
+ cue moveToFooter
 
 quickImportParser
  popularity 0.007524
- description Import a Scroll or Parsers file.
- extends abstractScrollParser
+ description Import a Scroll file.
+ extends importParser
  boolean isPopular true
+ int filenameAt 0
  inScope importToFooterParser abstractCommentParser
  atoms urlAtom
- pattern ^[^\s]+\.(scroll|parsers)$
+ pattern ^[^\s]+\.scroll$
  example
   header.scroll
 
+useParserPoolParser
+ cueFromId
+ description Load a cached parser pool.
+ extends abstractScrollParser
+ atoms cueAtom urlAtom
+ javascript
+  async wake() {
+    this.switchParserPool(this.filename)
+  }
+  get filename() { return this.atoms[1]}
+  get dependencies() { return [this.filename]}
+
+parsersImportParser
+ description Import a Parsers file.
+ extends quickImportParser
+ inScope abstractCommentParser
+ pattern ^[^\s]+\.parsers$
+ example
+  measures.parsers
+ javascript
+  async _handleImport() {
+    const file = await this._getFile()
+    if (!file.exists)
+      return await this._handleFileDoesNotExist()
+    // todo: cleanup
+    const newp = this.replaceWith(`useParserPool ${this.fullpath}`)
+    await newp[0].wake()
+  }
+
 importOnlyParser
  popularity 0.033569
  // This line will be not be imported into the importing file.
  description Don't build this file.
  cueFromId
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  extends abstractTopLevelSingleMetaParser
 
 abstractQuickIncludeParser
diff --git a/parsers/javascript.parsers b/parsers/javascript.parsers
index 1ccbb7f84..d5cfa5413 100644
--- a/parsers/javascript.parsers
+++ b/parsers/javascript.parsers
@@ -60,17 +60,17 @@ evalJsParser
  extends abstractScrollParser
  baseParser blobParser
  cueFromId
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  catchAllAtomType javascriptAnyAtom
  example
   evalJs "# The sum of 1 + 1 is " + 1 + 1
  javascript
-  wake() {
+  async wake() {
     try {
+      const particle = this
       const script = (this.content === undefined ? "" : this.content) + "\n" + this.subparticlesToString()
       const evaled = eval(script)
-      if (evaled)
-        this.replaceParticle(() => evaled.toString())
+      await this.root.appendFromStream(evaled)
     } catch (err) {
       console.error(err)
     }
diff --git a/parsers/macros.parsers b/parsers/macros.parsers
index cda2edb49..500c25828 100644
--- a/parsers/macros.parsers
+++ b/parsers/macros.parsers
@@ -1,7 +1,7 @@
 abstractMacroParser
  extends abstractScrollParser
  catchAllAtomType stringAtom
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  cueFromId
  javascript
   get search() {
@@ -27,7 +27,7 @@ abstractMacroParser
 replaceParser
  description Replace this with that.
  extends abstractMacroParser
- atoms preBuildCommandAtom codeAtom
+ atoms parseTimeCommandAtom codeAtom
  baseParser blobParser
  example
   replace YEAR 2022
@@ -42,6 +42,7 @@ replaceJsParser
  javascript
   get replacement() {
     const particle = this
+    const codeAtStart = this.root.codeAtStart || ""
     try {
       return eval(super.replacement)
     } catch (err) {
@@ -49,20 +50,3 @@ replaceJsParser
     }
     return this.search
   }
-
-toFooterParser
- extends abstractScrollParser
- description Experimental way to move a section to the footer.
- atoms preBuildCommandAtom
- cueFromId
- javascript
-  buildHtml() {
-    // todo: very hacky! fix.
-    this.section.forEach(particle => {
-        const clone = particle.clone()
-        this.root.appendParticle(clone)
-        particle.destroy()
-    })
-    this.destroy()
-    return ""
-  }
diff --git a/parsers/moves.parsers b/parsers/moves.parsers
new file mode 100644
index 000000000..1d6966ad4
--- /dev/null
+++ b/parsers/moves.parsers
@@ -0,0 +1,18 @@
+moveToFooterParser
+ extends abstractScrollParser
+ description Move a section to the footer.
+ atoms parseTimeCommandAtom
+ cueFromId
+ javascript
+  async wake() {
+    this.root.notifyOnReady(this)
+  }
+  onReady() {
+    this.section.forEach(particle => {
+        const clone = particle.clone()
+        this.root.appendParticle(clone)
+        particle.destroy()
+    })
+    this.destroy()
+    return ""
+  }
diff --git a/parsers/nodejs.parsers b/parsers/nodejs.parsers
index 93957f521..2e14e062b 100644
--- a/parsers/nodejs.parsers
+++ b/parsers/nodejs.parsers
@@ -21,7 +21,7 @@ evalNodejsParser
  extends abstractScrollParser
  catchAllAtomType javascriptAnyAtom
  baseParser blobParser
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  cueFromId
  example
   evalNodejs
@@ -30,5 +30,5 @@ evalNodejsParser
   wake() {
     const evaled = this.root.evalNodeJs(this)
     if (evaled !== false)
-    this.replaceParticle(() => evaled)
+    this.replaceWith(evaled)
   }
\ No newline at end of file
diff --git a/parsers/parsers.parsers b/parsers/parsers.parsers
index c003cd793..b36be6065 100644
--- a/parsers/parsers.parsers
+++ b/parsers/parsers.parsers
@@ -122,7 +122,7 @@ stringAtom
  paint string
 
 atomAtom
- paint constant
+ paint string
  description A non-empty single atom string.
  regex .+
 
@@ -452,6 +452,11 @@ atomTypeDefinitionParser
  inScope parsersPaintParser parsersRegexParser reservedAtomsParser enumFromAtomTypesParser atomTypeDescriptionParser parsersEnumParser slashCommentParser extendsAtomTypeParser parsersExamplesParser atomMinParser atomMaxParser
  atoms atomTypeIdAtom
  tags assemblePhase
+ javascript
+  buildHtml() {return ""}
+  async wake() {
+    this.root.stackParserCode(this)
+  }
 
 // Enums
 enumFromAtomTypesParser
@@ -504,6 +509,11 @@ parserDefinitionParser
  inScope abstractParserRuleParser abstractConstantParser slashCommentParser parserDefinitionParser
  atoms parserIdAtom
  tags assemblePhase
+ javascript
+  buildHtml() { return ""}
+  async wake() {
+    this.root.stackParserCode(this)
+  }
 
 parsersRegexParser
  catchAllAtomType regexAtom
diff --git a/parsers/posts.parsers b/parsers/posts.parsers
index 3af190c33..829bbbe55 100644
--- a/parsers/posts.parsers
+++ b/parsers/posts.parsers
@@ -10,7 +10,7 @@ abstractPostsParser
     const {fileSystem} = this.root
     for (let folderPath of dependsOn) {
       // console.log(`${this.root.filePath} is loading: ${folderPath} in id '${fileSystem.scrollFileSystemIdNumber}'`)
-      await fileSystem.getLoadedFilesInFolder(folderPath,  ".scroll")
+      await fileSystem.getFusedFilesInFolder(folderPath,  ".scroll")
     }
   }
   get tags() {
diff --git a/parsers/root.parsers b/parsers/root.parsers
index 09bc1ee6d..954789b7e 100644
--- a/parsers/root.parsers
+++ b/parsers/root.parsers
@@ -54,8 +54,6 @@ scrollParser
  javascript
   setFile(file) {
    this.file = file
-   const date = this.get("date")
-   if (date) this.file.timestamp = this.dayjs(this.get("date")).unix()
    return this
   }
   buildHtml(buildSettings) {
@@ -107,8 +105,14 @@ scrollParser
     const { scrollProgram } = file
     return scrollProgram.buildsHtml && scrollProgram.hasKeyboardNav && scrollProgram.tags.includes(this.primaryTag)
   }
-  get timeIndex() {
-    return this.file.timeIndex || 0
+  _timestamp
+  get timestamp() {
+   if (!this._timestamp) {
+    this._timestamp = this.file.timestamp
+    const date = this.get("date")
+    if (date) this._timestamp = this.dayjs(date).unix()
+   }
+   return this._timestamp
   }
   get linkToPrevious() {
     if (!this.hasKeyboardNav)
@@ -118,7 +122,7 @@ scrollParser
     let file = this._nextAndPrevious(allScrollFiles, this.timeIndex).previous
     if (!file) return undefined
     while (!this._includeFileInKeyboardNav(file)) {
-      file = this._nextAndPrevious(allScrollFiles, file.timeIndex).previous
+      file = this._nextAndPrevious(allScrollFiles, file.scrollProgram.timeIndex).previous
     }
     return file.scrollProgram.permalink
   }
@@ -130,7 +134,7 @@ scrollParser
     let file = this._nextAndPrevious(allScrollFiles, this.timeIndex).next
     if (!file) return undefined
     while (!this._includeFileInKeyboardNav(file)) {
-      file = this._nextAndPrevious(allScrollFiles, file.timeIndex).next
+      file = this._nextAndPrevious(allScrollFiles, file.scrollProgram.timeIndex).next
     }
     return file.scrollProgram.permalink
   }
@@ -174,7 +178,7 @@ scrollParser
       const {folderPath, group, relativePath} = this.parseNestedTag(tag)
       let files = []
       try {
-      files = this.fileSystem.getCachedLoadedFilesInFolder(folderPath, this)
+      files = this.fileSystem.getFusedFilesInFolderIfCached(folderPath, this)
       } catch (err) {
         console.error(err)
       }
@@ -183,7 +187,7 @@ scrollParser
       })
       arr = arr.concat(filtered.slice(0, limit))
     })
-    return this.lodash.sortBy(arr, file => file.file.timestamp).reverse()
+    return this.lodash.sortBy(arr, file => file.file.scrollProgram.timestamp).reverse()
   }
   async fetchNode(url, filename) {
     filename = filename || new URL(url).pathname.split('/').pop()
@@ -266,9 +270,19 @@ scrollParser
   get authors() {
     return this.get("authors")
   }
+  _addTimeIndexes(files) {
+    // A little hacky but ah well.
+    // For blogs, we want to sort posts in a folder in order of the date property.
+    // If the date property is not set, we use the file timestamp from disk.
+    const sorted = files.sort((a, b) => b.scrollProgram.timestamp - a.scrollProgram.timestamp)
+    sorted.forEach((file, index) => (file.scrollProgram.timeIndex = index))
+  }
   get allScrollFiles() {
     try {
-    return this.fileSystem.getCachedLoadedFilesInFolder(this.folderPath, this)
+    const files = this.fileSystem.getFusedFilesInFolderIfCached(this.folderPath, this)
+    if (this.timeIndex === undefined)
+      this._addTimeIndexes(files)
+    return files
     } catch (err) {
       console.error(err)
       return []
@@ -287,6 +301,17 @@ scrollParser
   getFromParserId(parserId) {
     return this.parserIdIndex[parserId]?.[0].content
   }
+  notifyOnReady(particle) {
+    if (!this._toNotify)
+     this._toNotify = []
+    this._toNotify.push(particle)
+  }
+  wake() {
+    // In case the file ended on a parser definition, refresh parser pool
+    this._refreshParserPool()
+    if (this._toNotify)
+      this._toNotify.forEach(particle => particle.onReady())
+  }
   get fileSystem() {
     return this.file.fileSystem
   }
@@ -367,7 +392,7 @@ scrollParser
   }
   get scrollVersion() {
     // currently manually updated
-    return "176.0.1"
+    return "177.0.0"
   }
   // Use the first paragraph for the description
   // todo: add a particle method version of get that gets you the first particle. (actulaly make get return array?)
@@ -432,9 +457,12 @@ scrollParser
       const files = this.topDownArray.filter(particle => particle.dependencies).map(particle => particle.dependencies).flat()
       return dependencies.concat(files)
   }
+  get importOnly() {
+    return this.has("importOnly")
+  }
   get buildsHtml() {
     const { permalink } = this
-    return !this.file.importOnly && (permalink.endsWith(".html") || permalink.endsWith(".htm"))
+    return !this.importOnly && (permalink.endsWith(".html") || permalink.endsWith(".htm"))
   }
   // Without specifying the language hyphenation will not work.
   get lang() {
@@ -463,7 +491,7 @@ scrollParser
     return this.dateObject.format(`MM/DD/YYYY`)
   }
   get dateObject() {
-    const date = this.get("date") || (this.file.timestamp ? this.file.timestamp : 0)
+    const date = this.get("date") || (this.timestamp || 0)
     return this.dayjs(date)
   }
   get year() {
@@ -515,11 +543,11 @@ scrollParser
         })
         .join("\n")
       concept.forEach((particle, index) => (index ? particle.destroy() : ""))
-      concept[0].replaceParticle(() => newCode)
+      concept[0].replaceWith(newCode)
     })
   }
   get formatted() {
-    return this.getFormatted(this.file.codeAtStart)
+    return this.getFormatted(this.codeAtStart)
   }
   get lastCommitTime() {
     // todo: speed this up and do a proper release. also could add more metrics like this.
@@ -532,9 +560,17 @@ scrollParser
     }
     return this._lastCommitTime
   }
+  get codeAtStart() {
+    return this.file.codeAtStart
+  }
+  async ensureFileLoaded() {
+    // todo: cleanup
+    if (!this.codeAtStart)
+      await this.file._readCodeFromStorage()
+  }
   getFormatted(codeAtStart = this.toString()) {
     let formatted = codeAtStart.replace(/\r/g, "") // remove all carriage returns if there are any
-    const parsed = new this.constructor(formatted)
+    const parsed = new this.latestConstructor(formatted)
     parsed.topDownArray.forEach(subparticle => {
       subparticle.format()
       const original = subparticle.getLine()
@@ -548,10 +584,16 @@ scrollParser
     let allElse = []
     // Create any bindings
     parsed.forEach(particle => {
-      if (particle.bindTo === "next") particle.binding = particle.next
-      if (particle.bindTo === "previous") particle.binding = particle.previous
+      if (particle.bindTo === "next" && !particle.isLast) particle.binding = particle.next
+      if (particle.bindTo === "previous" && !particle.isFirst) particle.binding = particle.previous
     })
+    let noFormat = false
     parsed.forEach(particle => {
+      if (noFormat) return allElse.push(particle)
+      if (particle.getLine() === "noFormat") {
+         noFormat = true
+         return allElse.push(particle)
+      }
       if (particle.getLine() === "importOnly") importOnlys.push(particle)
       else if (particle.isTopMatter) topMatter.push(particle)
       else allElse.push(particle)
@@ -559,7 +601,7 @@ scrollParser
     const combined = importOnlys.concat(topMatter, allElse)
     // Move any bound particles
     combined
-      .filter(particle => particle.bindTo)
+      .filter(particle => particle.binding)
       .forEach(particle => {
         // First remove the particle from its current position
         const originalIndex = combined.indexOf(particle)
@@ -606,6 +648,30 @@ scrollParser
       await particle.buildTwo(options)
     }
   }
+  stackParserCode(parser) {
+    // Add top level parsers only which will add their nested parsers.
+    if (parser.parent !== this) return
+    // Perf hack until we can refactor ParserPool and add incremental addition of parsers.
+    // What we see in the wild is that frequently you'll have parser definitions one after
+    // the other, separated by blank lines or comments. So we stack up those parsers and
+    // dont add them until we are done with that section.
+    if (this._parsersToRegister === undefined)
+        this._parsersToRegister = []
+    this._parsersToRegister.push(parser)
+    if (!this._beforeAppend)
+        this._beforeAppend = (block) => {
+          const line1 = block.split(/\n/)[0]
+          if (line1 === "" || line1.endsWith("Parser") || line1.startsWith("//"))
+            return
+          this._refreshParserPool()
+        }
+  }
+  _refreshParserPool() {
+    if (!this._parsersToRegister) return
+    this.registerParsers(this._parsersToRegister.map(p => p.toString()).join("\n"), this.filePath)
+    delete this._beforeAppend
+    delete this._parsersToRegister
+  }
   get outputFileNames() {
     return this.filter(p => p.outputFileNames).map(p => p.outputFileNames).flat()
   }
@@ -690,26 +756,20 @@ scrollParser
     return measure
   })
   }
-  parseMeasures(parser) {
-  if (!Particle.measureCache)
-    Particle.measureCache = new Map()
-  const measureCache = Particle.measureCache
-  if (measureCache.get(parser)) return measureCache.get(parser)
-  const {lodash} = this
+  get latestConstructor() {
+    // todo: cleanup
+    return this._modifiedConstructor || this.constructor
+  }
+  _parseMeasures() {
+  const {lodash, definition} = this
+  // cache measures on the _Parser_, since they are unique to a parser.
+  if (definition._measures)
+    return definition._measures
   // todo: clean this up
-  const getCueAtoms = rootParserProgram =>
-    rootParserProgram
-      .filter(particle => particle.getLine().endsWith("Parser") && !particle.getLine().startsWith("abstract"))
-      .map(particle => particle.get("cue") || particle.getLine())
-      .map(line => line.replace(/Parser$/, ""))
   // Generate a fake program with one of every of the available parsers. Then parse it. Then we can easily access the meta data on the parsers
-  const dummyProgram = new parser(
-    Array.from(
-      new Set(
-        getCueAtoms(parser.cachedHandParsersProgramRoot) // is there a better method name than this?
-      )
-    ).join("\n"), this.getLine()
-  )
+  const dummyCode = Array.from(new Set(definition.map(particle => particle.get("cue") || particle.getLine().replace(/Parser$/, "")))).join("\n")
+  const parser = this.latestConstructor
+  const dummyProgram = new parser(dummyCode, this.getLine())
   // Delete any particles that are not measures
   dummyProgram.filter(particle => !particle.isMeasure).forEach(particle => particle.destroy())
   dummyProgram.forEach(particle => {
@@ -735,22 +795,25 @@ scrollParser
       Cue: particle.definition.get("cue")
     }
   })
-  measureCache.set(parser, lodash.sortBy(measures, "SortIndex"))
-  return measureCache.get(parser)
+  definition._measures = lodash.sortBy(measures, "SortIndex")
+  return definition._measures
   }
   _concepts
   get concepts() {
-    if (this._concepts) return this._concepts
-    this._concepts = this.parseConcepts(this, this.measures)
+    if (!this._concepts) this._concepts = this._parseConcepts()
     return this._concepts
   }
+  get concept() {
+    return this.concepts[0]
+  }
   _measures
   get measures() {
-    if (this._measures) return this._measures
-    this._measures = this.parseMeasures(this.parser)
+    if (!this._measures) return this._measures = this._parseMeasures()
     return this._measures
   }
-  parseConcepts(parsedProgram, measures){
+  _parseConcepts(){
+  const parsedProgram = this
+  const measures = this.measures
   // Todo: might be a perf/memory/simplicity win to have a "segment" method in ScrollSDK, where you could
   // virtually split a Particle into multiple segments, and then query on those segments.
   // So we would "segment" on "id ", and then not need to create a bunch of new objects, and the original
diff --git a/parsers/source.parsers b/parsers/source.parsers
index 2cea8e45b..d5d76ef6b 100644
--- a/parsers/source.parsers
+++ b/parsers/source.parsers
@@ -8,5 +8,5 @@ printSourceParser
  javascript
   buildHtml() {
    const files = this.root.getFilesByTags(this.content).map(file => file.file)
-   return `${files.map(file => file.scrollProgram.filePath + "\n " + file.codeAtStart.replace(/\n/g, "\n ") ).join("\n")}`
+   return `${files.map(file => file.scrollProgram).map(scrollProgram => scrollProgram.filePath + "\n " + scrollProgram.codeAtStart.replace(/\n/g, "\n ") ).join("\n")}`
   }
diff --git a/parsers/sourcemap.parsers b/parsers/sourcemap.parsers
index 322aed046..dac2828a2 100644
--- a/parsers/sourcemap.parsers
+++ b/parsers/sourcemap.parsers
@@ -17,7 +17,7 @@ debugSourceMapParser
         currentFile.lineNumber++
         currentFile.linesLeft--
         if (particle.cue === "imported") {
-          const linesLeft = parseInt(particle.get("lines"))
+          const linesLeft = parseInt(particle.get("particles"))
           const original = particle.get("original")
           fileStack.push({ fileName: particle.atoms[1], lineNumber: 0, linesLeft })
           return `${currentFile.fileName}:${currentFile.lineNumber} ${original}\n` + particle.map(line => `${currentFile.fileName}:${currentFile.lineNumber}  ${line}`).join("\n")
diff --git a/parsers/stamp.parsers b/parsers/stamp.parsers
index 228eaedec..edfd230bf 100644
--- a/parsers/stamp.parsers
+++ b/parsers/stamp.parsers
@@ -143,7 +143,7 @@ stampParser
      hello.js
       console.log("Hello world")
  cueFromId
- atoms preBuildCommandAtom
+ atoms parseTimeCommandAtom
  javascript
   execute() {
     const dir = this.root.folderPath
diff --git a/releaseNotes.scroll b/releaseNotes.scroll
index 5b4eb8731..b12c2c541 100644
--- a/releaseNotes.scroll
+++ b/releaseNotes.scroll
@@ -22,6 +22,18 @@ ciBadges.scroll
 br
 thinColumns
 
+📦 177.0.0 4/06/2025
+🎉 Scroll is now a single-pass language!
+🎉 added assertBuildEndsWithParser
+🎉 added conceptTemplateParser
+🎉 added dumpConceptParser
+🎉 added noFormatParser
+🏥 update ScrollSDK to 107
+🏥 fixed regression in concept building
+🏥 fixed bug in custom dinkus
+⚠️ BREAKING: `toFooter` is now `moveToFooter`
+⚠️ BREAKING: `footer` in an import block is now `moveToFooter`
+
 📦 176.0.1 3/29/2025
 🏥 update ScrollSDK
 
@@ -91,6 +103,7 @@ This text should be aligned right.
 🎉 Added `noSnippet` parser that can be used in all aftertext parsers to prevent HTML generation of that particle when generating a snippet.
 🏥 fix bug with date printing in short snippets.
 ⚠️ BREAKING: removed stump parsers. if you were using `stump` parsers, just unnest subparticles under stump and delete stump atom.
+⚠️ BREAKING: remove `stumpNoSnippet`
 
 codeWithHeader Before:
  stump
diff --git a/scroll.js b/scroll.js
index 89c173369..aa1412123 100755
--- a/scroll.js
+++ b/scroll.js
@@ -60,10 +60,9 @@ footer.scroll`
   }
 
   async scrollToHtml(scrollCode) {
-    const ScrollFile = this.sfs.defaultFileClass
-    const page = new ScrollFile(scrollCode)
-    await page.fuse()
-    return page.scrollProgram.asHtml
+    const file = this.sfs.newFile(scrollCode)
+    await file.singlePassFuse()
+    return file.scrollProgram.asHtml
   }
 
   sfs = new ScrollFileSystem(undefined, path.join(__dirname, "parsers"))
@@ -80,18 +79,12 @@ footer.scroll`
   async getErrorsInFolder(folder) {
     const fileSystem = this.sfs
     const folderPath = ensureFolderEndsInSlash(folder)
-    const files = await fileSystem.getLoadedFilesInFolder(folderPath, ".scroll") // Init/cache all parsers
-
-    // todo: cleanup
-    const parsers = await Promise.all(Object.values(fileSystem._parserCache))
-    const parserErrors = parsers.map(parser => parser.parsersParser.getAllErrors().map(err => err.toObject())).flat()
-
-    const scrollErrors = await this.getErrorsInFiles(files)
-    return { parserErrors, scrollErrors }
+    const files = await fileSystem.getFusedFilesInFolder(folderPath, ".scroll") // Init/cache all parsers
+    return await this.getErrorsInFiles(files)
   }
 
   async getErrorsInFiles(files) {
-    // todo: what about parser errors?
+    // todo: re-add parser errors
     for (let file of files) await file.scrollProgram.load()
     return files
       .map(file => {
@@ -107,49 +100,42 @@ footer.scroll`
     const start = Date.now()
     const folder = this.resolvePath(cwd)
     let target = cwd
-    let parserErrors = []
     let scrollErrors = []
     if (filenames && filenames.length) {
       const files = await this.getFiles(cwd, filenames)
       scrollErrors = await this.getErrorsInFiles(files)
       target = filenames.join(" ")
     } else {
-      const results = await this.getErrorsInFolder(folder)
-      parserErrors = results.parserErrors
-      scrollErrors = results.scrollErrors
+      scrollErrors = await this.getErrorsInFolder(folder)
     }
 
     const seconds = (Date.now() - start) / 1000
 
-    if (parserErrors.length) {
-      this.log(``)
-      this.log(`❌ ${parserErrors.length} parser errors in "${cwd}"`)
-      this.log(new Particle(parserErrors).toFormattedTable(200))
-      this.log(``)
-    }
     if (scrollErrors.length) {
       this.log(``)
       this.log(`❌ ${scrollErrors.length} errors in "${cwd}"`)
       this.log(new Particle(scrollErrors).toFormattedTable(100))
       this.log(``)
     }
-    if (!parserErrors.length && !scrollErrors.length) return this.log(`✅ 0 errors in "${target}". Tests took ${seconds} seconds.`)
-    return `${parserErrors.length + scrollErrors.length} Errors`
+    if (!scrollErrors.length) return this.log(`✅ 0 errors in "${target}". Tests took ${seconds} seconds.`)
+    return `${scrollErrors.length} Errors`
   }
 
   async formatCommand(cwd, filenames) {
     let files = []
     if (filenames && filenames.length) files = await this.getFiles(cwd, filenames)
-    else files = await this.sfs.getLoadedFilesInFolder(this.resolvePath(cwd), ".scroll")
-    // .concat(fileSystem.getLoadedFilesInFolder(folder, ".parsers")) // todo: should format parser files too.
+    else files = await this.sfs.getFusedFilesInFolder(this.resolvePath(cwd), ".scroll")
+    // .concat(fileSystem.getFusedFilesInFolder(folder, ".parsers")) // todo: should format parser files too.
     for (let file of files) {
-      this.formatFile(file)
+      this.formatFile(file.scrollProgram)
     }
   }
 
-  async formatFile(file) {
-    const { formatted, filePath, filename } = file.scrollProgram
-    const { codeAtStart } = file
+  // Formatting is currently defined as formatting the entire original source file
+  // using the last parser present.
+  async formatFile(scrollProgram) {
+    await scrollProgram.ensureFileLoaded()
+    const { formatted, filePath, filename, codeAtStart } = scrollProgram
     if (codeAtStart === formatted) return
     await this.sfs.write(filePath, formatted)
     this.log(`💾 formatted ${filename}`)
@@ -165,7 +151,7 @@ footer.scroll`
 
   async getFiles(cwd, filenames) {
     const fullPaths = this.resolveFilenames(cwd, filenames)
-    const files = await Promise.all(fullPaths.map(fp => this.sfs.getLoadedFile(fp)))
+    const files = await Promise.all(fullPaths.map(fp => this.sfs.getFusedFile(fp)))
     return files
   }
 
@@ -183,7 +169,7 @@ footer.scroll`
     const start = Date.now()
     // Run the build loop twice. The first time we build ScrollSets, in case some of the HTML files
     // will depend on csv/tsv/json/etc
-    const toBuild = files.filter(file => !file.importOnly)
+    const toBuild = files.filter(file => !file.scrollProgram.importOnly)
     options.externalFilesCopied = {}
     for (const file of toBuild) {
       file.scrollProgram.logger = this
@@ -210,7 +196,7 @@ footer.scroll`
 
   async buildFilesInFolder(folder = "/", fileSystem = this.sfs) {
     folder = ensureFolderEndsInSlash(folder)
-    const files = await fileSystem.getLoadedFilesInFolder(folder, ".scroll")
+    const files = await fileSystem.getFusedFilesInFolder(folder, ".scroll")
     this.log(`Found ${files.length} scroll files in '${folder}'\n`)
     return await this.buildFiles(fileSystem, files, folder)
   }
diff --git a/tests/a-review-of-my-sink.scroll b/tests/a-review-of-my-sink.scroll
index 032a63a50..30ddb1d76 100644
--- a/tests/a-review-of-my-sink.scroll
+++ b/tests/a-review-of-my-sink.scroll
@@ -1,10 +1,10 @@
+tags index all
+title A review of my sink
 replace SOME_DATA
  - foo
   link bar.html
  - bar
   link bam.html
-tags index all
-title A review of my sink
 
 header.scroll
 
diff --git a/tests/aParser.scroll b/tests/aParser.scroll
index 11dfd27ea..ec5e40bee 100644
--- a/tests/aParser.scroll
+++ b/tests/aParser.scroll
@@ -1,3 +1,10 @@
+buildHtml
+
+The below should just be parsed as text:
+hiddenMessage Click me.
+ message Hello world
+assertHtmlExcludes onclick="ale
+
 hiddenMessageParser
  extends scrollParagraphParser
  inScope messageParser
@@ -6,5 +13,8 @@ hiddenMessageParser
   buildHtml() {
    return `<span onclick="alert('${this.get("message")}')">${super.buildHtml()}</span>`
   }
+
+The below should be parsed by the parser above
 hiddenMessage Click me.
  message Hello world
+assertHtmlIncludes onclick="ale
diff --git a/tests/about.scroll b/tests/about.scroll
index 2de2bed2c..9dd1816dc 100644
--- a/tests/about.scroll
+++ b/tests/about.scroll
@@ -1,6 +1,6 @@
-replace KEY_MESSAGE Public domain products are strictly superior to equivalent non-public domain alternatives by a significant margin on three dimensions: trust, speed, and cost to build.
 tags all
 title About the Kitchen Sink Blog
+replace KEY_MESSAGE Public domain products are strictly superior to equivalent non-public domain alternatives by a significant margin on three dimensions: trust, speed, and cost to build.
 
 header.scroll
 
diff --git a/tests/atomTypes.scroll b/tests/atomTypes.scroll
new file mode 100644
index 000000000..0b388ad27
--- /dev/null
+++ b/tests/atomTypes.scroll
@@ -0,0 +1,23 @@
+buildHtml
+
+streetLightAtom
+ extends stringAtom
+ enum red green yellow
+ paint constant
+
+lightParser
+ cueFromId
+ extends abstractScrollParser
+ atoms cueAtom streetLightAtom
+ javascript
+  buildHtml() {
+   return `<span style="color:${this.atoms[1]}">[0]</span>`
+  }
+
+light red
+assertHtmlIncludes color:red
+
+// Test overwriting an atom. The original atomType should still be used above.
+streetLightAtom
+ extends stringAtom
+ enum orange purple
diff --git a/tests/authors.scroll b/tests/authors.scroll
index 46a1e0e9f..5c88ec25b 100644
--- a/tests/authors.scroll
+++ b/tests/authors.scroll
@@ -1,4 +1,4 @@
-Authors should not print anything:
 authors Breck Yunits
  https://breckyunits.com
 assertHtmlExcludes Breck
+Authors should not print anything.
diff --git a/tests/concepts.scroll b/tests/concepts.scroll
index 69453e10b..bd5712bfc 100644
--- a/tests/concepts.scroll
+++ b/tests/concepts.scroll
@@ -18,3 +18,7 @@ notes Daughter - Samantha.
 phone +1 (555) 123-4562
 email jill@gmail.com
 birthday 1/23/80
+
+conceptTemplate
+ # This is a page for {name}
+ His phone is {phone}
diff --git a/tests/contacts.scroll b/tests/contacts.scroll
index f97be0bc0..367a0c725 100644
--- a/tests/contacts.scroll
+++ b/tests/contacts.scroll
@@ -1,11 +1,13 @@
 buildConcepts contacts.csv contacts.json contacts.tsv
 buildHtml
 title My Contacts
-
-../microlangs/contacts.parsers
+container
 theme gazette
+../microlangs/contacts.parsers
+
 mediumColumns 1
 printTitle
+// This is a little confusing. This datatable is fed by the csv's generated above (I think.). Datatable looks at permalink name for a matching csv.
 datatable
  printTable
  assertRowCount 2
diff --git a/tests/debugging.scroll b/tests/debugging.scroll
index 04a8f5cc0..6902dfd2b 100644
--- a/tests/debugging.scroll
+++ b/tests/debugging.scroll
@@ -1,6 +1,7 @@
 buildHtml
 replace TITLE Debug tools tests
 replaceJs SUM 1+1
+noFormat
 title TITLE
 
 theme gazette
diff --git a/tests/dumpParsers.scroll b/tests/dumpParsers.scroll
new file mode 100644
index 000000000..e7f33a3a0
--- /dev/null
+++ b/tests/dumpParsers.scroll
@@ -0,0 +1,7 @@
+buildParsers dumpParsers.txt
+assertBuildIncludes Carpe diem!
+// Just test to ensure some source code from a parser is included
+
+// This prints all parsers.
+// We use it to dump all parsers to a single file to power try.scroll.pub
+debugParsers
diff --git a/tests/html.scroll b/tests/html.scroll
index 0b0f6797c..31d46c8b6 100644
--- a/tests/html.scroll
+++ b/tests/html.scroll
@@ -14,7 +14,6 @@ meta
  content tag
 assertHtmlIncludes />
 
-
 ol
  li A list item
 assertHtmlIncludes </ol>
diff --git a/tests/json.scroll b/tests/json.scroll
index dc15f01cf..4ef6bb98f 100644
--- a/tests/json.scroll
+++ b/tests/json.scroll
@@ -11,4 +11,4 @@ script
 
 ../package.json
  path prettier
- printTable
\ No newline at end of file
+ printTable
diff --git a/tests/modal.scroll b/tests/modal.scroll
index 1adb2ce16..6e8cba34a 100644
--- a/tests/modal.scroll
+++ b/tests/modal.scroll
@@ -9,7 +9,6 @@ modal
  id m1
 # This should be in a modal
 
-
 Open modal 2.
  link #m2 modal
 
@@ -19,4 +18,3 @@ modal
  id m2
 # This is modal 2.
 loremIpsum 2
-
diff --git a/tests/push.scroll b/tests/moveToFooter.scroll
similarity index 66%
rename from tests/push.scroll
rename to tests/moveToFooter.scroll
index 72967eb72..e4c0a98ef 100644
--- a/tests/push.scroll
+++ b/tests/moveToFooter.scroll
@@ -1,5 +1,8 @@
 buildHtml
-toFooter
-This is my footer. It is moved to end of file before compilation.
+buildTxt
+assertBuildEndsWith The End.
+
+moveToFooter
+This is my footer. It is moved to end of file before compilation. The End.
 
 This is my body. This should be above the footer.
diff --git a/tests/parsersImports.scroll b/tests/parsersImports.scroll
new file mode 100644
index 000000000..457816670
--- /dev/null
+++ b/tests/parsersImports.scroll
@@ -0,0 +1,11 @@
+buildHtml
+
+extension.parsers
+
+// This should not trigger an uncaught error
+assertSilenceBelowErrors
+fileDoesNotExist.parsers
+
+goodMorning
+assertHtmlIncludes Good morning
+
diff --git a/tests/postTemplate.scroll b/tests/postTemplate.scroll
index 4bc30ca09..053469c68 100644
--- a/tests/postTemplate.scroll
+++ b/tests/postTemplate.scroll
@@ -2,7 +2,7 @@ importOnly
 buildHtml
 header.scroll
 footer.scroll
- footer
+ moveToFooter
 
 printTitle
 
diff --git a/tests/scroll.test.js b/tests/scroll.test.js
index 321eddf65..65be3a422 100755
--- a/tests/scroll.test.js
+++ b/tests/scroll.test.js
@@ -3,6 +3,7 @@
 const tap = require("tap")
 const fs = require("fs")
 const path = require("path")
+const { Particle } = require("scrollsdk/products/Particle.js")
 const { ScrollCli } = require("../scroll.js")
 const { ScrollSetCLI } = require("../ScrollSetCLI.js")
 const { Disk } = require("scrollsdk/products/Disk.node.js")
@@ -15,7 +16,6 @@ const testParticles = {}
 const testsFolder = path.join(__dirname)
 const stampFolder = path.join(testsFolder, "testOutput")
 const cli = new ScrollCli()
-const ScrollFile = cli.sfs.defaultFileClass
 
 // cleanup in case it was built earlier:
 if (Disk.exists(stampFolder)) fs.rmSync(stampFolder, { recursive: true })
@@ -124,7 +124,7 @@ buildHtml`
 testParticles.file = async areEqual => {
   const rootFolder = path.join(__dirname, "..")
   const cli = new ScrollCli().silence()
-  const files = await cli.sfs.getLoadedFilesInFolder(rootFolder, ".scroll")
+  const files = await cli.sfs.getFusedFilesInFolder(rootFolder, ".scroll")
   const releaseNotesFile = files.find(file => file.scrollProgram.permalink === "releaseNotes.html").scrollProgram
 
   areEqual(releaseNotesFile.permalink, "releaseNotes.html")
@@ -134,7 +134,7 @@ testParticles.file = async areEqual => {
 }
 
 testParticles.ensureNoErrorsInParser = async areEqual => {
-  const DefaultScrollParser = cli.sfs.defaultParser.parser
+  const DefaultScrollParser = cli.sfs.defaultParser
   const parserErrors = new parsersParser(new DefaultScrollParser().definition.asString).getAllErrors().map(err => err.toObject())
   if (parserErrors.length) console.log(parserErrors)
   areEqual(parserErrors.length, 0, "no errors in scroll standard library parsers")
@@ -165,12 +165,12 @@ testParticles.cli = async areEqual => {
 
 testParticles.standalonePage = async areEqual => {
   // Arrange
-  const page = new ScrollFile(`title A standalone page
+  const file = cli.sfs.newFile(`title A standalone page
 printTitle
 * Blue sky`)
   // Act/Assert
-  await page.fuse()
-  const { asHtml, asTxt } = page.scrollProgram
+  await file.singlePassFuse()
+  const { asHtml, asTxt } = file.scrollProgram
   areEqual(asHtml.includes("Blue sky"), true)
   areEqual(asTxt.includes("A standalone page"), true)
 }
@@ -213,33 +213,33 @@ testParticles.scrollsetCli = areEqual => {
 
 testParticles.format = async areEqual => {
   // Arrange
-  const page = new ScrollFile(``)
+  const file = cli.sfs.newFile("")
   // Act/Assert
-  await page.fuse()
-  areEqual(page.scrollProgram.formatted, "", "format works")
+  await file.singlePassFuse()
+  areEqual(file.scrollProgram.formatted, "", "format works")
 
-  const page2 = new ScrollFile(`# hi`)
+  const file2 = cli.sfs.newFile(`# hi`)
   // Act/Assert
-  await page2.fuse()
-  areEqual(page2.scrollProgram.formatted, "# hi\n", "format works")
+  await file2.singlePassFuse()
+  areEqual(file2.scrollProgram.formatted, "# hi\n", "format works")
 }
 
 testParticles.outputFileNames = async areEqual => {
   // Arrange
-  const page = new ScrollFile(``)
+  const file = cli.sfs.newFile("")
   // Act
-  await page.fuse()
+  await file.singlePassFuse()
   // Assert
-  areEqual(page.scrollProgram.outputFileNames.length, 0, "no outputFileNames in a blank file")
+  areEqual(file.scrollProgram.outputFileNames.length, 0, "no outputFileNames in a blank file")
 
   // Arrange
-  const page2 = new ScrollFile(`buildHtml foo.html
+  const file2 = cli.sfs.newFile(`buildHtml foo.html
 buildTxt foo.txt
 `)
   // Act
-  await page2.fuse()
+  await file2.singlePassFuse()
   // Assert
-  areEqual(page2.scrollProgram.outputFileNames[1], "foo.txt")
+  areEqual(file2.scrollProgram.outputFileNames[1], "foo.txt")
 }
 
 testParticles.initCommand = async areEqual => {
@@ -257,13 +257,13 @@ testParticles.initCommand = async areEqual => {
     const products = await cli.buildFilesInFolder(tempFolder)
 
     // Assert
-    areEqual(Disk.read(products[3]).includes("Built with Scroll"), true, "has message")
+    const helloWorldPath = path.join(tempFolder, "helloWorld.html")
+    areEqual(Disk.read(helloWorldPath).includes("Built with Scroll"), true, "has message")
     areEqual(products.filter(name => name.endsWith(".html")).length, 2, "should have 2 html pages")
     areEqual(products.length, 7, "should have 7 total generated files")
 
-    const { scrollErrors, parserErrors } = await cli.getErrorsInFolder(tempFolder)
+    const scrollErrors = await cli.getErrorsInFolder(tempFolder)
     areEqual(scrollErrors.length, 0)
-    areEqual(parserErrors.length, 0)
   } catch (err) {
     console.log(err)
   }
@@ -299,6 +299,133 @@ testParticles.hodgePodge = async areEqual => {
   fs.rmSync(stampFolder, { recursive: true })
 }
 
+const stripImported = str => {
+  const particle = new Particle(str)
+  particle.getParticles("imported").forEach(particle => particle.destroy())
+  return particle.toString()
+}
+
+testParticles.inMemory = async equal => {
+  // Arrange/Act/Assert
+  const cli = new ScrollCli().silence()
+  const files = {
+    "/hello.scroll": "world",
+    "/main.scroll": "import hello.scroll\nimport nested/test.scroll",
+    "/nested/test.scroll": "ciao",
+    "/nested/deep/relative.scroll": "import ../../hello.scroll\nimport ../test.scroll"
+  }
+  cli.initFs(files)
+  const fused = await cli.sfs.getFusedFilesInFolder("/", "scroll")
+  const mainResult = fused.find(file => file.filePath === "/main.scroll")
+  equal(stripImported(mainResult.scrollProgram), "world\nciao")
+  equal(mainResult.scrollProgram.toString().includes("exists true"), true)
+
+  const relativeResult = await cli.sfs.getFusedFile("/nested/deep/relative.scroll")
+  equal(stripImported(relativeResult.scrollProgram), "world\nciao")
+}
+
+testParticles.empty = async equal => {
+  // Arrange
+  const cli = new ScrollCli().silence()
+  const files = {
+    "/hello.scroll": "",
+    "/main.scroll": "import hello.scroll\nhi"
+  }
+  cli.initFs(files)
+
+  // Act
+  const fused = await cli.sfs.getFusedFilesInFolder("/", "scroll")
+  const mainResult = await cli.sfs.getFusedFile("/main.scroll")
+  // Assert
+  equal(stripImported(mainResult.scrollProgram), `\nhi`)
+}
+
+testParticles.nonExistant = async equal => {
+  // Arrange/Act/Assert
+  const cli = new ScrollCli().silence()
+  const files = {
+    "/main.scroll": "import env.scroll"
+  }
+  cli.initFs(files)
+  const fused = await cli.sfs.getFusedFilesInFolder("/", "scroll")
+  const result = await cli.sfs.getFusedFile("/main.scroll")
+  equal(stripImported(result.scrollProgram.toString()), "")
+  equal(result.scrollProgram.toString().includes("exists false"), true)
+}
+
+testParticles.footers = async equal => {
+  // Arrange/Act/Assert
+  const cli = new ScrollCli().silence()
+  const files = {
+    "/hello.scroll": `headerAndFooter.scroll
+title Hello world
+This is my content
+`,
+    "/headerAndFooter.scroll": `header.scroll
+footer.scroll
+ moveToFooter`,
+    "/header.scroll": "printTitle",
+    "/footer.scroll": "The end."
+  }
+  cli.initFs(files)
+  await cli.sfs.getFusedFilesInFolder("/", "scroll")
+  const result = await cli.sfs.getFusedFile("/hello.scroll")
+  equal(result.scrollProgram.toString().includes("This is my content"), true)
+  equal(result.scrollProgram.toString().endsWith("The end."), true, "ends with footer")
+}
+
+testParticles.circularImports = async equal => {
+  const cli = new ScrollCli().silence()
+  const files = {
+    "/a.scroll": "b.scroll",
+    "/b.scroll": "a.scroll",
+    "/c.scroll": "c.scroll",
+    "/d.scroll": "e.scroll\nf.scroll",
+    "/e.scroll": "f.scroll",
+    "/f.scroll": "g.scroll",
+    "/g.scroll": ""
+  }
+  cli.initFs(files)
+  const sfs = cli.sfs
+  await sfs.getFusedFilesInFolder("/", "scroll")
+  const result2 = await sfs.getFusedFile("/c.scroll")
+  equal(result2.scrollProgram.toString().includes("circularImportError"), true, "Should have detected circularImports")
+  const result = await sfs.getFusedFile("/a.scroll")
+  equal(result.scrollProgram.toString().includes("circularImportError"), true, "Should have detected circularImports")
+  const result3 = await sfs.getFusedFile("/d.scroll")
+  equal(result3.scrollProgram.toString().includes("circularImportError"), false, "No circularImports detected")
+}
+
+testParticles.quickImports = async equal => {
+  // Arrange/Act/Assert
+  const cli = new ScrollCli().silence()
+  const files = {
+    "/hello.scroll": "world",
+    "/main": "hello.scroll\nnested/test.scroll",
+    "/nested/test.scroll": "ciao",
+    "/nested/a": "test.scroll",
+    "/nested/deep/relative": "../../hello.scroll\n../test.scroll"
+  }
+  cli.initFs(files)
+  const sfs = cli.sfs
+  equal(sfs.dirname("/"), "/")
+
+  const [aResult, mainResult, relativeResult] = await Promise.all([sfs.getFusedFile("/nested/a"), sfs.getFusedFile("/main"), sfs.getFusedFile("/nested/deep/relative")])
+  equal(stripImported(aResult.scrollProgram.toString()), "ciao")
+  equal(stripImported(mainResult.scrollProgram.toString()), "world\nciao")
+  equal(stripImported(relativeResult.scrollProgram.toString()), "world\nciao")
+
+  // FileAPI
+  // Arrange
+  const file = sfs.newFile(files["/main"], "/main")
+  equal(file.scrollProgram.toString(), "")
+  // Act
+  // TODO: make this singlePassFuse
+  await file.singlePassFuse()
+  // Assert
+  equal(stripImported(file.scrollProgram.toString()), "world\nciao")
+}
+
 if (module && !module.parent) TestRacer.testSingleFile(__filename, testParticles)
 
 module.exports = { testParticles }
diff --git a/tests/sourcemaps.scroll b/tests/sourcemaps.scroll
index 39a7c4e58..ff2dd78c0 100644
--- a/tests/sourcemaps.scroll
+++ b/tests/sourcemaps.scroll
@@ -8,6 +8,6 @@ header.scroll
 footer.scroll
 
 ## Now print source map:
+// Test this using assertHtmlMatches rather than assertHtmlIncludes because a simple string search of the source would just match the string in the source.
 debugSourceMap
 assertHtmlMatches settings.scroll:\d extension.parsers
-// Test this using assertHtmlMatches rather than assertHtmlIncludes because a simple string search of the source would just match the string in the source.
\ No newline at end of file
diff --git a/tests/textAlign.scroll b/tests/textAlign.scroll
index aca16d6ba..1cbe5ee9e 100644
--- a/tests/textAlign.scroll
+++ b/tests/textAlign.scroll
@@ -23,4 +23,4 @@ assertHtmlIncludes center
 > Veni. Vidi. Vici.
  Julius caesar
   right
-assertHtmlIncludes text-align: right;
\ No newline at end of file
+assertHtmlIncludes text-align: right;
diff --git a/tests/top-sinks.scroll b/tests/top-sinks.scroll
index b8dcb6e7c..8640d4837 100644
--- a/tests/top-sinks.scroll
+++ b/tests/top-sinks.scroll
@@ -2,6 +2,8 @@ authors Breck Yunits
  https://breckyunits.com Breck Yunits
 buildTxt
 date 1/11/2019
+tags index all
+title Top Sinks
 replace NUM_SINKS 283
 replace TABLE
  datatable
@@ -16,8 +18,6 @@ replaceJs THE_DAY require("dayjs")(particle.parent.get("date")).format(`MMMM D,
 replaceJs TODAYS_DATE Date()
 replaceNodejs
  module.exports = {DIRNAME: __dirname}
-tags index all
-title Top Sinks
 
 header.scroll
 
diff --git a/tests/txt.scroll b/tests/txt.scroll
index 0067db9ac..04045ca9f 100644
--- a/tests/txt.scroll
+++ b/tests/txt.scroll
@@ -3,4 +3,4 @@ assert txt includes Hello
 assert txt excludes hola
 assert txt equals Hello world
 assert txt excludes <
-assert html includes <
\ No newline at end of file
+assert html includes <