diff --git a/package.json b/package.json
index 2f37c5955..960cb615c 100644
--- a/package.json
+++ b/package.json
@@ -47,12 +47,12 @@
     "onCommand:metals.new-scala-project",
     "onDebugResolve:scala",
     "onLanguage:scala",
-    "workspaceContains:build.sbt",
-    "workspaceContains:build.sc",
-    "workspaceContains:project/build.properties",
-    "workspaceContains:src/main/scala",
-    "workspaceContains:*/src/main/scala",
-    "workspaceContains:*/*/src/main/scala"
+    "!onFileSystem:jar && workspaceContains:build.sbt",
+    "!onFileSystem:jar && workspaceContains:build.sc",
+    "!onFileSystem:jar && workspaceContains:project/build.properties",
+    "!onFileSystem:jar && workspaceContains:src/main/scala",
+    "!onFileSystem:jar && workspaceContains:*/src/main/scala",
+    "!onFileSystem:jar && workspaceContains:*/*/src/main/scala"
   ],
   "contributes": {
     "languages": [
diff --git a/src/extension.ts b/src/extension.ts
index 5dba179f6..1bc149a25 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -28,6 +28,7 @@ import {
   ProviderResult,
   Hover,
   TextDocument,
+  FileSystemProvider,
 } from "vscode";
 import {
   LanguageClient,
@@ -90,7 +91,7 @@ import { BuildTargetUpdate } from "./testExplorer/types";
 import * as workbenchCommands from "./workbenchCommands";
 import { getServerVersion } from "./getServerVersion";
 import { getCoursierMirrorPath } from "./mirrors";
-
+import MetalsFileSystemProvider from "./metalsFileSystemProvider";
 const outputChannel = window.createOutputChannel("Metals");
 const openSettingsAction = "Open settings";
 const downloadJava = "Download Java";
@@ -228,7 +229,7 @@ function fetchAndLaunchMetals(
   if (dottyIde.enabled) {
     outputChannel.appendLine(
       `Metals will not start since Dotty is enabled for this workspace. ` +
-        `To enable Metals, remove the file ${dottyIde.path} and run 'Reload window'`
+      `To enable Metals, remove the file ${dottyIde.path} and run 'Reload window'`
     );
     return;
   }
@@ -441,6 +442,15 @@ function launchMetals(
     );
   }
 
+  function registerFileSystemProvider(
+    scheme: string,
+    provider: FileSystemProvider
+  ) {
+    context.subscriptions.push(
+      workspace.registerFileSystemProvider(scheme, provider, { isCaseSensitive: true, isReadonly: true })
+    );
+  }
+
   function registerTextDocumentContentProvider(
     scheme: string,
     provider: TextDocumentContentProvider
@@ -453,7 +463,6 @@ function launchMetals(
   const metalsFileProvider = new MetalsFileProvider(client);
 
   registerTextDocumentContentProvider("metalsDecode", metalsFileProvider);
-  registerTextDocumentContentProvider("jar", metalsFileProvider);
 
   registerCommand("metals.show-cfr", async (uri: Uri) => {
     await decodeAndShowFile(client, metalsFileProvider, uri, "cfr");
@@ -730,6 +739,19 @@ function launchMetals(
               }
               break;
             }
+            case "metals-create-library-filesystem": {
+              const uri = params.arguments && params.arguments[0];
+              if (typeof uri === "string") {
+                const librariesURI = Uri.parse(uri)
+                // filesystem is persistent across VSCode sessions so may already exist
+                if (!workspace.getWorkspaceFolder(librariesURI))
+                  workspace.updateWorkspaceFolders(1, 0, { uri: librariesURI, name: "Metals - Libraries" });
+
+                const metalsFileSystemProvider = new MetalsFileSystemProvider(client, outputChannel);
+                registerFileSystemProvider(librariesURI.scheme, metalsFileSystemProvider);
+              }
+              break;
+            }
             case ClientCommands.FocusDiagnostics:
               commands.executeCommand(ClientCommands.FocusDiagnostics);
               break;
diff --git a/src/metalsFileSystemProvider.ts b/src/metalsFileSystemProvider.ts
new file mode 100644
index 000000000..8334b1d5e
--- /dev/null
+++ b/src/metalsFileSystemProvider.ts
@@ -0,0 +1,131 @@
+//import { ServerCommands } from "metals-languageclient";
+import {
+  EventEmitter,
+  //ProviderResult,
+  FileSystemProvider,
+  Uri,
+  Disposable,
+  Event,
+  FileChangeEvent,
+  FileStat,
+  FileType,
+  OutputChannel,
+} from "vscode";
+import { ExecuteCommandRequest } from "vscode-languageclient";
+import { LanguageClient } from "vscode-languageclient/node";
+
+
+export interface FSReadDirectoryResponse {
+  name: string,
+  isFile: boolean,
+  error?: string
+}
+
+export interface FSReadFileResponse {
+  value: string,
+  error?: string
+}
+
+export interface FSStatResponse {
+  isFile: boolean,
+  error?: string
+}
+
+export class GenericFileStat implements FileStat {
+  type: FileType;
+  ctime: number;
+  mtime: number;
+  size: number;
+
+  constructor(isFile: boolean) {
+    this.type = (isFile) ? FileType.File : FileType.Directory;
+    this.ctime = Date.now();
+    this.mtime = Date.now();
+    this.size = 0;
+  }
+}
+
+export default class MetalsFileSystemProvider implements FileSystemProvider {
+  readonly onDidChangeEmitter = new EventEmitter<Uri>();
+  readonly onDidChange = this.onDidChangeEmitter.event;
+  readonly client: LanguageClient;
+  readonly outputChannel: OutputChannel;
+
+  constructor(client: LanguageClient,
+    outputChannel: OutputChannel) {
+    this.outputChannel = outputChannel;
+    this.client = client;
+  }
+
+  private _emitter = new EventEmitter<FileChangeEvent[]>();
+  readonly onDidChangeFile: Event<FileChangeEvent[]> = this._emitter.event;
+
+  stat(uri: Uri): FileStat | Thenable<FileStat> {
+    return this.client.sendRequest(ExecuteCommandRequest.type, {
+      // TODO move to ServerCommands
+      command: "filesystem-stat",
+      arguments: [uri.toString(true)],
+    }).then((result) => {
+      // TODO how much info is required here?
+      const value = result as FSStatResponse;
+      return new GenericFileStat(value.isFile);
+    });
+  }
+
+  toReadDirResult(response: FSReadDirectoryResponse): [string, FileType] {
+    return [response.name, response.isFile ? FileType.File : FileType.Directory]
+  }
+
+  readDirectory(uri: Uri): [string, FileType][] | Thenable<[string, FileType][]> {
+    return this.client.sendRequest(ExecuteCommandRequest.type, {
+      // TODO move to ServerCommands
+      command: "filesystem-read-directory",
+      arguments: [uri.toString(true)],
+    }).then((result) => {
+      const value = result as FSReadDirectoryResponse[];
+      return value.map(this.toReadDirResult);
+    });
+  }
+
+  readFile(uri: Uri): Uint8Array | Thenable<Uint8Array> {
+    return this.client.sendRequest(ExecuteCommandRequest.type, {
+      // TODO move to ServerCommands
+      command: "filesystem-read-file",
+      arguments: [uri.toString(true)],
+    }).then((result) => {
+      const { value, error } = result as FSReadFileResponse;
+      let contents: string;
+      if (value != null) {
+        contents = value;
+      } else {
+        if (error)
+          contents = error;
+        else
+          contents = "Unknown error";
+      }
+      return Buffer.from(contents);
+    });
+  }
+
+
+  watch(uri: Uri, options: { recursive: boolean; excludes: string[]; }): Disposable {
+    this.outputChannel.appendLine(`ignoring watch ${uri} ${options}`);
+    throw new Error(`watch ${uri} ${options} not implemented.`);
+  }
+  createDirectory(uri: Uri): void | Thenable<void> {
+    this.outputChannel.appendLine(`ignoring createDirectory ${uri}`);
+    throw new Error(`createDirectory ${uri} not implemented.`);
+  }
+  delete(uri: Uri, options: { recursive: boolean; }): void | Thenable<void> {
+    this.outputChannel.appendLine(`ignoring delete ${uri} ${options}`);
+    throw new Error(`delete ${uri} ${options} not implemented.`);
+  }
+  rename(oldUri: Uri, newUri: Uri, options: { overwrite: boolean; }): void | Thenable<void> {
+    this.outputChannel.appendLine(`ignoring rename ${oldUri} ${newUri} ${options}`);
+    throw new Error(`rename ${oldUri} ${newUri} ${options} not implemented.`);
+  }
+  writeFile(uri: Uri, content: Uint8Array, options: { create: boolean; overwrite: boolean; }): void | Thenable<void> {
+    this.outputChannel.appendLine(`ignoring writeFile ${uri} ${content} ${options}`);
+    throw new Error(`writeFile ${uri} ${content} ${options} not implemented.`);
+  }
+}