diff --git a/services/web/frontend/js/features/pdf-preview/util/compiler.ts b/services/web/frontend/js/features/pdf-preview/util/compiler.ts
index d4695558e9..bd9eef3a40 100644
--- a/services/web/frontend/js/features/pdf-preview/util/compiler.ts
+++ b/services/web/frontend/js/features/pdf-preview/util/compiler.ts
@@ -260,4 +260,15 @@ export default class DocumentCompiler {
   ) {
     this.defaultOptions[option] = value
   }
+
+  updateAutoCompileDebounce(debounceMs: number, maxWaitMs: number) {
+    this.debouncedAutoCompile.cancel()
+    this.debouncedAutoCompile = debounce(
+      () => {
+        this.compile({ isAutoCompileOnChange: true })
+      },
+      debounceMs,
+      { maxWait: maxWaitMs }
+    )
+  }
 }
diff --git a/services/web/frontend/js/shared/context/local-compile-context.tsx b/services/web/frontend/js/shared/context/local-compile-context.tsx
index 8e2ed0242e..2ef1f08153 100644
--- a/services/web/frontend/js/shared/context/local-compile-context.tsx
+++ b/services/web/frontend/js/shared/context/local-compile-context.tsx
@@ -155,11 +155,6 @@ export const LocalCompileProvider: FC<React.PropsWithChildren> = ({
   const { findEntityByPath } = useFileTreePathContext()
   const getRootDocInfo = useRootDoc()
 
-  // Captured once at mount; drives auto-compile defaults and debounce timing.
-  const [isTypstProject] = useState(() =>
-    getRootDocInfo().rootResourcePath.endsWith('.typ')
-  )
-
   // whether a compile is in progress
   const [compiling, setCompiling] = useState(false)
 
@@ -264,10 +259,10 @@ export const LocalCompileProvider: FC<React.PropsWithChildren> = ({
 
   const [position, setPosition] = usePdfScrollPosition(lastCompileRootDocId)
 
-  // whether autocompile is switched on (Typst projects default to enabled)
+  // whether autocompile is switched on
   const [autoCompile, setAutoCompile] = usePersistedState(
     `autocompile_enabled:${projectId}`,
-    isTypstProject,
+    false,
     { listen: true }
   )
 
@@ -340,10 +335,6 @@ export const LocalCompileProvider: FC<React.PropsWithChildren> = ({
       signal,
       openDocs,
       getRootDocInfo,
-      // Typst compiles are near-instant via `typst watch`; use a much tighter
-      // debounce so the PDF refreshes as the user types.
-      autoCompileDebounce: isTypstProject ? 300 : undefined,
-      autoCompileMaxWait: isTypstProject ? 1000 : undefined,
     })
   })
 
@@ -352,6 +343,22 @@ export const LocalCompileProvider: FC<React.PropsWithChildren> = ({
     compiler.getRootDocInfo = getRootDocInfo
   }, [compiler, getRootDocInfo])
 
+  // Typst projects compile near-instantly via `typst watch`.
+  // getRootDocInfo() returns accurate paths only after the file tree loads
+  // (project joins via WebSocket), so we do detection in an effect that re-runs
+  // when its reference changes.  window.localStorage is checked directly to
+  // distinguish "no stored preference" from an explicit user choice.
+  useEffect(() => {
+    const { rootResourcePath } = getRootDocInfo()
+    if (!rootResourcePath.endsWith('.typ')) return
+    // Default auto-compile ON for Typst — only if user has never set a pref.
+    if (window.localStorage.getItem(`autocompile_enabled:${projectId}`) === null) {
+      setAutoCompile(true)
+    }
+    // Tighten the debounce so the PDF updates as the user types.
+    compiler.updateAutoCompileDebounce(300, 1000)
+  }, [compiler, getRootDocInfo, projectId, setAutoCompile])
+
   // keep draft setting in sync with the compiler
   useEffect(() => {
     compiler.setOption('draft', draft)