diff --git a/package.json b/package.json
index a91044e1b..0afa64f32 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
     "url": "https://github.com/atom/atom/issues"
   },
   "license": "MIT",
-  "electronVersion": "2.0.2",
+  "electronVersion": "2.0.4",
   "dependencies": {
     "@atom/nsfw": "^1.0.18",
     "@atom/watcher": "1.0.3",
@@ -92,7 +92,7 @@
     "solarized-dark-syntax": "1.1.5",
     "solarized-light-syntax": "1.1.5",
     "about": "1.9.1",
-    "archive-view": "0.65.0",
+    "archive-view": "0.65.1",
     "autocomplete-atom-api": "0.10.7",
     "autocomplete-css": "0.17.5",
     "autocomplete-html": "0.8.4",
@@ -121,7 +121,7 @@
     "line-ending-selector": "0.7.7",
     "link": "0.31.4",
     "markdown-preview": "0.159.20",
-    "metrics": "1.3.0",
+    "metrics": "1.4.3",
     "notifications": "0.70.5",
     "open-on-github": "1.3.1",
     "package-generator": "1.3.0",
diff --git a/script/lib/clean-caches.js b/script/lib/clean-caches.js
index 1df3aa9c2..3861908bb 100644
--- a/script/lib/clean-caches.js
+++ b/script/lib/clean-caches.js
@@ -14,6 +14,7 @@ module.exports = function () {
     path.join(CONFIG.atomHomeDirPath, '.apm'),
     path.join(CONFIG.atomHomeDirPath, '.npm'),
     path.join(CONFIG.atomHomeDirPath, 'compile-cache'),
+    path.join(CONFIG.atomHomeDirPath, 'snapshot-cache'),
     path.join(CONFIG.atomHomeDirPath, 'atom-shell'),
     path.join(CONFIG.atomHomeDirPath, 'electron'),
     path.join(os.tmpdir(), 'atom-build'),
diff --git a/spec/atom-reporter.coffee b/spec/atom-reporter.coffee
index a522d9298..9af21a7dd 100644
--- a/spec/atom-reporter.coffee
+++ b/spec/atom-reporter.coffee
@@ -33,6 +33,8 @@ formatStackTrace = (spec, message='', stackTrace) ->
       line = line.trim()
         # at jasmine.Spec.<anonymous> (path:1:2) -> at path:1:2
         .replace(/^at jasmine\.Spec\.<anonymous> \(([^)]+)\)/, 'at $1')
+        # at jasmine.Spec.it (path:1:2) -> at path:1:2
+        .replace(/^at jasmine\.Spec\.f*it \(([^)]+)\)/, 'at $1')
         # at it (path:1:2) -> at path:1:2
         .replace(/^at f*it \(([^)]+)\)/, 'at $1')
         # at spec/file-test.js -> at file-test.js
diff --git a/spec/workspace-spec.js b/spec/workspace-spec.js
index 5d920363a..091588a70 100644
--- a/spec/workspace-spec.js
+++ b/spec/workspace-spec.js
@@ -1299,6 +1299,34 @@ describe('Workspace', () => {
     })
   })
 
+  describe('the root-scope-used hook', () => {
+    it('fires when opening a file or changing the grammar of an open file', async () => {
+      await atom.packages.activatePackage('language-javascript')
+      await atom.packages.activatePackage('language-coffee-script')
+
+      const observeTextEditorsSpy = jasmine.createSpy('observeTextEditors')
+      const javascriptGrammarUsed = jasmine.createSpy('javascript')
+      const coffeeScriptGrammarUsed = jasmine.createSpy('coffeescript')
+
+      atom.packages.triggerDeferredActivationHooks()
+      atom.packages.onDidTriggerActivationHook('source.js:root-scope-used', () => {
+        atom.workspace.observeTextEditors(observeTextEditorsSpy)
+        javascriptGrammarUsed()
+      })
+      atom.packages.onDidTriggerActivationHook('source.coffee:root-scope-used', coffeeScriptGrammarUsed)
+
+      expect(javascriptGrammarUsed).not.toHaveBeenCalled()
+      expect(observeTextEditorsSpy).not.toHaveBeenCalled()
+      const editor = await atom.workspace.open('sample.js', {autoIndent: false})
+      expect(javascriptGrammarUsed).toHaveBeenCalled()
+      expect(observeTextEditorsSpy.callCount).toBe(1)
+
+      expect(coffeeScriptGrammarUsed).not.toHaveBeenCalled()
+      atom.grammars.assignLanguageMode(editor, 'source.coffee')
+      expect(coffeeScriptGrammarUsed).toHaveBeenCalled()
+    })
+  })
+
   describe('::reopenItem()', () => {
     it("opens the uri associated with the last closed pane that isn't currently open", () => {
       const pane = workspace.getActivePane()
diff --git a/src/tree-sitter-language-mode.js b/src/tree-sitter-language-mode.js
index 8344c89a5..981b35af1 100644
--- a/src/tree-sitter-language-mode.js
+++ b/src/tree-sitter-language-mode.js
@@ -5,6 +5,7 @@ const {Emitter, Disposable} = require('event-kit')
 const ScopeDescriptor = require('./scope-descriptor')
 const TokenizedLine = require('./tokenized-line')
 const TextMateLanguageMode = require('./text-mate-language-mode')
+const async = require('async')
 
 let nextId = 0
 const MAX_RANGE = new Range(Point.ZERO, Point.INFINITY).freeze()
@@ -30,6 +31,19 @@ class TreeSitterLanguageMode {
     this.parser = new Parser()
     this.rootLanguageLayer = new LanguageLayer(this, grammar)
     this.injectionsMarkerLayer = buffer.addMarkerLayer()
+    this.updatedGrammars = []
+
+    this.parsers = []
+    this.parseQueue = async.queue(async ({language, oldTree, ranges}, done) => {
+      const parser = this.parsers.pop() || new Parser()
+      parser.setLanguage(language)
+      const newTree = await parser.parseTextBuffer(this.buffer.buffer, oldTree, {
+        syncOperationLimit: 1000,
+        includedRanges: ranges
+      })
+      this.parsers.push(parser)
+      done(null, newTree)
+    }, 2)
 
     this.rootScopeDescriptor = new ScopeDescriptor({scopes: [this.grammar.id]})
     this.emitter = new Emitter()
@@ -80,6 +94,14 @@ class TreeSitterLanguageMode {
     }
   }
 
+  parse (language, oldTree, ranges) {
+    return new Promise(resolve =>
+      this.parseQueue.push({language, oldTree, ranges}, (error, tree) =>
+        resolve(tree)
+      )
+    )
+  }
+
   get tree () {
     return this.rootLanguageLayer.tree
   }
@@ -476,11 +498,10 @@ class LanguageLayer {
       if (includedRanges.length === 0) return
     }
 
-    this.languageMode.parser.setLanguage(this.grammar.languageModule)
-    const tree = await this.languageMode.parser.parseTextBuffer(
-      this.languageMode.buffer.buffer,
+    const tree = await this.languageMode.parse(
+      this.grammar.languageModule,
       this.tree,
-      {syncOperationLimit: 1000, includedRanges}
+      includedRanges
     )
     tree.buffer = this.languageMode.buffer
 
@@ -566,9 +587,11 @@ class LanguageLayer {
       }
     }
 
+    const promises = []
     for (const [marker, injectionNode] of markersToUpdate) {
-      await marker.languageLayer.update(injectionNode)
+      promises.push(marker.languageLayer.update(injectionNode))
     }
+    return Promise.all(promises)
   }
 
   /**
diff --git a/src/workspace.js b/src/workspace.js
index 00976759f..a3f85ddeb 100644
--- a/src/workspace.js
+++ b/src/workspace.js
@@ -1268,7 +1268,8 @@ module.exports = class Workspace extends Model {
 
   handleGrammarUsed (grammar) {
     if (grammar == null) { return }
-    return this.packageManager.triggerActivationHook(`${grammar.packageName}:grammar-used`)
+    this.packageManager.triggerActivationHook(`${grammar.scopeName}:root-scope-used`)
+    this.packageManager.triggerActivationHook(`${grammar.packageName}:grammar-used`)
   }
 
   // Public: Returns a {Boolean} that is `true` if `object` is a `TextEditor`.