diff --git a/src/app/services/Spyglass.ts b/src/app/services/Spyglass.ts
index f36a3cc2..028ef21d 100644
--- a/src/app/services/Spyglass.ts
+++ b/src/app/services/Spyglass.ts
@@ -1,5 +1,4 @@
 import * as core from '@spyglassmc/core'
-import { ErrorReporter } from '@spyglassmc/core'
 import { BrowserExternals } from '@spyglassmc/core/lib/browser.js'
 import type { McmetaSummary } from '@spyglassmc/java-edition/lib/dependency/index.js'
 import { Fluids, ReleaseVersion, symbolRegistrar } from '@spyglassmc/java-edition/lib/dependency/index.js'
@@ -11,7 +10,6 @@ import { localize } from '@spyglassmc/locales'
 import * as mcdoc from '@spyglassmc/mcdoc'
 import * as nbt from '@spyglassmc/nbt'
 import * as zip from '@zip.js/zip.js'
-import type { Position, Range } from 'vscode-languageserver-textdocument'
 import { TextDocument } from 'vscode-languageserver-textdocument'
 import type { ConfigGenerator } from '../Config.js'
 import siteConfig from '../Config.js'
@@ -52,6 +50,7 @@ export class SpyglassClient {
 			...BrowserExternals.archive,
 			decompressBall,
 		},
+		fs: new SpyglassFileSystem(),
 	}
 
 	public readonly documents = new Map<string, ClientDocument>()
@@ -78,7 +77,7 @@ export class SpyglassService {
 	}
 
 	public getCheckerContext(doc: TextDocument, errors: core.LanguageError[]) {
-		const err = new ErrorReporter()
+		const err = new core.ErrorReporter()
 		err.errors = errors
 		return core.CheckerContext.create(this.service.project, { doc, err })
 	}
@@ -421,10 +420,258 @@ function registerAttributes(meta: core.MetaRegistry, release: ReleaseVersion, ve
 	})
 }
 
-function getLsPosition(offset: number, doc: TextDocument): Position {
-	return doc.positionAt(offset)
+class SpyglassFileSystem implements core.ExternalFileSystem {
+	public static readonly dbName = 'misode-spyglass-fs'
+	public static readonly dbVersion = 1
+	public static readonly storeName = 'files'
+
+	private readonly db: Promise<IDBDatabase>
+
+	constructor() {
+		this.db = new Promise((res, rej) => {
+			const request = indexedDB.open(SpyglassFileSystem.dbName, SpyglassFileSystem.dbVersion)
+			request.onerror = (e) => {
+				console.warn('Database error', message((e.target as any)?.error))
+				rej()
+			}
+			request.onsuccess = () => {
+				res(request.result)
+			}
+			request.onupgradeneeded = (event) => {
+				const db = (event.target as any).result as IDBDatabase
+				db.createObjectStore(SpyglassFileSystem.storeName, { keyPath: 'uri' })
+			}
+		})
+	}
+
+	async chmod(_location: core.FsLocation, _mode: number): Promise<void> {
+		return
+	}
+
+	async mkdir(
+		location: core.FsLocation,
+		_options?: { mode?: number | undefined, recursive?: boolean | undefined } | undefined,
+	): Promise<void> {
+		location = core.fileUtil.ensureEndingSlash(location.toString())
+		const db = await this.db
+		return new Promise((res, rej) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readwrite')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			const getRequest = store.get(location)
+			getRequest.onsuccess = () => {
+				const entry = getRequest.result
+				if (entry !== undefined) {
+					rej(new Error(`EEXIST: ${location}`))
+				} else {
+					const putRequest = store.put({ uri: location, type: 'directory' })
+					putRequest.onsuccess = () => {
+						res()
+					}
+					putRequest.onerror = () => {
+						rej()
+					}
+				}
+			}
+			getRequest.onerror	= () => {
+				rej()
+			}
+		})
+	}
+	async readdir(location: core.FsLocation): Promise<{ name: string, isDirectory(): boolean, isFile(): boolean, isSymbolicLink(): boolean }[]> {
+		location = core.fileUtil.ensureEndingSlash(location.toString())
+		const db = await this.db
+		return new Promise((res, rej) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readonly')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			// TODO: specify range
+			const request = store.openCursor()
+			const result: { name: string, isDirectory(): boolean, isFile(): boolean, isSymbolicLink(): boolean }[] = []
+			request.onsuccess = () => {
+				if (request.result) {
+					const entry = request.result.value
+					result.push({
+						name: request.result.key.toString(),
+						isDirectory: () => entry.type === 'directory',
+						isFile: () => entry.type === 'file',
+						isSymbolicLink: () => false,
+					})
+					request.result.continue()
+				} else {
+					res(result)
+				}
+			}
+			request.onerror = () => {
+				rej()
+			}
+		})
+	}
+	async readFile(location: core.FsLocation): Promise<Uint8Array> {
+		location = location.toString()
+		const db = await this.db
+		return new Promise((res, rej) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readonly')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			const request = store.get(location)
+			request.onsuccess = () => {
+				const entry = request.result
+				if (!entry) {
+					rej(new Error(`ENOENT: ${location}`))
+				} else if (entry.type === 'directory') {
+					rej(new Error(`EISDIR: ${location}`))
+				} else {
+					res(entry.content)
+				}
+			}
+			request.onerror = () => {
+				rej()
+			}
+		})
+	}
+	async showFile(_location: core.FsLocation): Promise<void> {
+		throw new Error('showFile not supported on browser')
+	}
+	async stat(location: core.FsLocation): Promise<{ isDirectory(): boolean, isFile(): boolean }> {
+		location = location.toString()
+		const db = await this.db
+		return new Promise((res, rej) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readonly')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			const request = store.get(location)
+			request.onsuccess = () => {
+				const entry = request.result
+				if (!entry) {
+					rej(new Error(`ENOENT: ${location}`))
+				} else {
+					res({
+						isDirectory: () => entry.type === 'directory',
+						isFile: () => entry.type === 'file',
+					})
+				}
+			}
+			request.onerror = () => {
+				rej()
+			}
+		})
+	}
+	async unlink(location: core.FsLocation): Promise<void> {
+		location = location.toString()
+		const db = await this.db
+		return new Promise((res, rej) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readwrite')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			const getRequest = store.get(location)
+			getRequest.onsuccess = () => {
+				const entry = getRequest.result
+				if (!entry) {
+					rej(new Error(`ENOENT: ${location}`))
+				} else {
+					const deleteRequest = store.delete(location)
+					deleteRequest.onsuccess = () => {
+						res()
+					}
+					deleteRequest.onerror = () => {
+						rej()
+					}
+				}
+			}
+			getRequest.onerror = () => {
+				rej()
+			}
+		})
+	}
+	watch(locations: core.FsLocation[], _options: { usePolling?: boolean | undefined }): core.FsWatcher {
+		return new SpyglassWatcher(this.db, locations)
+	}
+	async writeFile(
+		location: core.FsLocation,
+		data: string | Uint8Array,
+		_options?: { mode: number } | undefined,
+	): Promise<void> {
+		location = location.toString()
+		if (typeof data === 'string') {
+			data = new TextEncoder().encode(data)
+		}
+		const db = await this.db
+		return new Promise((res, rej) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readwrite')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			const request = store.put({ uri: location, type: 'file', content: data })
+			request.onsuccess = () => {
+				res()
+			}
+			request.onerror = () => {
+				rej()
+			}
+		})
+	}
 }
 
-export function getLsRange(range: core.Range, doc: TextDocument): Range {
-	return { start: getLsPosition(range.start, doc), end: getLsPosition(range.end, doc) }
+// Copied from spyglass because it isn't exported
+type Listener = (...args: any[]) => any
+class BrowserEventEmitter implements core.ExternalEventEmitter {
+	readonly #listeners = new Map<string, { all: Set<Listener>, once: Set<Listener> }>()
+
+	emit(eventName: string, ...args: any[]): boolean {
+		const listeners = this.#listeners.get(eventName)
+		if (!listeners?.all?.size) {
+			return false
+		}
+		for (const listener of listeners.all) {
+			listener(...args)
+			if (listeners.once.has(listener)) {
+				listeners.all.delete(listener)
+				listeners.once.delete(listener)
+			}
+		}
+		return false
+	}
+
+	on(eventName: string, listener: Listener): this {
+		if (!this.#listeners.has(eventName)) {
+			this.#listeners.set(eventName, { all: new Set(), once: new Set() })
+		}
+		const listeners = this.#listeners.get(eventName)!
+		listeners.all.add(listener)
+		return this
+	}
+
+	once(eventName: string, listener: Listener): this {
+		if (!this.#listeners.has(eventName)) {
+			this.#listeners.set(eventName, { all: new Set(), once: new Set() })
+		}
+		const listeners = this.#listeners.get(eventName)!
+		listeners.all.add(listener)
+		listeners.once.add(listener)
+		return this
+	}
+}
+
+class SpyglassWatcher extends BrowserEventEmitter implements core.FsWatcher {
+	constructor(dbPromise: Promise<IDBDatabase>, locations: core.FsLocation[]) {
+		super()
+		dbPromise.then((db) => {
+			const transaction = db.transaction(SpyglassFileSystem.storeName, 'readonly')
+			const store = transaction.objectStore(SpyglassFileSystem.storeName)
+			const request = store.openKeyCursor()
+			request.onsuccess = () => {
+				if (request.result) {
+					const uri = request.result.key.toString()
+					for (const location of locations) {
+						if (uri.startsWith(location)) {
+							this.emit('add', uri)
+							break
+						}
+					}
+					request.result.continue()
+				} else {
+					this.emit('ready')
+				}
+			}
+			request.onerror = () => {
+				this.emit('error', new Error('Watcher error'))
+			}
+		})
+	}
+
+	async close(): Promise<void> {}
 }