diff --git a/tools/server/webui/src/lib/constants/settings-config.ts b/tools/server/webui/src/lib/constants/settings-config.ts
index 350186ebeb..d06b3eaaa5 100644
--- a/tools/server/webui/src/lib/constants/settings-config.ts
+++ b/tools/server/webui/src/lib/constants/settings-config.ts
@@ -10,6 +10,7 @@ export const SETTING_CONFIG_DEFAULT: Record<string, string | number | boolean> =
 	disableReasoningFormat: false,
 	keepStatsVisible: false,
 	responsiveChatWidth: false,
+	chatScreenWidth: '',
 	showMessageStats: true,
 	askForTitleConfirmation: false,
 	pasteLongTextToFileLen: 2500,
@@ -88,7 +89,9 @@ export const SETTING_CONFIG_INFO: Record<string, string> = {
 		'Show raw LLM output without backend parsing and frontend Markdown rendering to inspect streaming across different models.',
 	keepStatsVisible: 'Keep processing statistics visible after generation finishes.',
 	responsiveChatWidth:
-		'Enable responsive chat width that adapts to your screen size. When disabled, uses a fixed width optimized for readability.',
+		'Enable responsive chat width that automatically adapts to your screen size using breakpoints. When enabled, overrides the custom width setting below.',
+	chatScreenWidth:
+		'Set a fixed chat screen width. Choose from predefined sizes (xs to 7xl) or enter a custom pixel value. Only applies when responsive width is disabled.',
 	showMessageStats:
 		'Display generation statistics (tokens/second, token count, duration) below each assistant message.',
 	askForTitleConfirmation: