From 7dd234de37da68f6edbcd1857af225ce2f685fd5 Mon Sep 17 00:00:00 2001
From: xhon-pelushi <xhon@pelushi.com>
Date: Thu, 13 Aug 2026 00:43:52 -0400
Subject: [PATCH] Avoid crash opening large text files in built-in editor

BrowseFilesPresenter.viewFile() routed .txt/.md/.todo files to the
built-in text editor with no size check. TextEditorPresenter reads
the whole file into a String for the EditText, so memory use scales
with file size; a ~15 MB file kills the process and locks all vaults.

Skip the internal editor for files above 2 MiB and fall back to
opening them with an external app instead, matching the existing
behavior for other unsupported file types.

Fixes #654
---
 .../presentation/presenter/BrowseFilesPresenter.kt       | 9 +++++++++
 presentation/src/main/res/values/strings.xml             | 1 +
 2 files changed, 10 insertions(+)

diff --git a/presentation/src/main/java/org/cryptomator/presentation/presenter/BrowseFilesPresenter.kt b/presentation/src/main/java/org/cryptomator/presentation/presenter/BrowseFilesPresenter.kt
index 913a931672..3d1f1b38ef 100644
--- a/presentation/src/main/java/org/cryptomator/presentation/presenter/BrowseFilesPresenter.kt
+++ b/presentation/src/main/java/org/cryptomator/presentation/presenter/BrowseFilesPresenter.kt
@@ -509,6 +509,11 @@ class BrowseFilesPresenter @Inject constructor( //
 	private fun viewFile(cloudFile: CloudFileModel) {
 		val lowerFileName = cloudFile.name.lowercase()
 		if (lowerFileName.endsWith(".txt") || lowerFileName.endsWith(".md") || lowerFileName.endsWith(".todo")) {
+			if ((cloudFile.size ?: 0) > MAX_TEXT_EDITOR_FILE_SIZE) {
+				view?.showMessage(R.string.screen_file_browser_msg_text_file_too_large_for_editor)
+				viewExternalFile(cloudFile)
+				return
+			}
 			val intent = Intents.textEditorIntent()
 				.withTextFile(cloudFile)
 				.withHubWriteAllowed(licenseEnforcer.hasWriteAccessForVault(view?.folder?.vault()))
@@ -1273,6 +1278,10 @@ class BrowseFilesPresenter @Inject constructor( //
 
 		const val OPEN_FILE_FINISHED = 12
 
+		// The built-in text editor reads the whole file into a String and hands it to an EditText,
+		// so memory use scales with file size. Files above this size are opened with an external app instead.
+		private const val MAX_TEXT_EDITOR_FILE_SIZE = 2L shl 20 // 2 MiB
+
 		val EXPORT_AFTER_APP_CHOOSER: ExportOperation = object : ExportOperation {
 			override fun export(presenter: BrowseFilesPresenter, downloadFiles: List<DownloadFile>) {
 				presenter.copyFile(downloadFiles)
diff --git a/presentation/src/main/res/values/strings.xml b/presentation/src/main/res/values/strings.xml
index b5c41279c3..3bd2bcb079 100644
--- a/presentation/src/main/res/values/strings.xml
+++ b/presentation/src/main/res/values/strings.xml
@@ -174,6 +174,7 @@
 	<string name="screen_file_browser_move_button_text">Move</string>
 
 	<string name="screen_file_browser_msg_empty_folder">Empty folder</string>
+	<string name="screen_file_browser_msg_text_file_too_large_for_editor">File is too large for the built-in editor, opening with another app</string>
 	<string name="screen_file_browser_file_info_label_size" translatable="false">%1$s</string>
 	<string name="screen_file_browser_file_info_label_date">modified %1$s ago</string>