diff --git a/services/clsi/app/js/TypstRunner.js b/services/clsi/app/js/TypstRunner.js
index 242d81c1ce..12a3ff2d0b 100644
--- a/services/clsi/app/js/TypstRunner.js
+++ b/services/clsi/app/js/TypstRunner.js
@@ -17,6 +17,12 @@ const MAX_LOG_LINES = 500
 // How long to wait for the watcher process to emit its first output.
 const WATCH_START_TIMEOUT_MS = 15_000
 
+// Matches the start-of-compile marker typst watch emits before each cycle:
+//   "[HH:MM:SS] compiling ..."
+// Used to reset the line buffer so stale output from a failed compile that
+// didn't emit a "compiled with errors" footer cannot bleed into the next log.
+const COMPILE_START_RE = /^\[\d{2}:\d{2}:\d{2}\] compiling/
+
 // Matches the three terminal lines that typst watch emits at the end of each
 // compile cycle regardless of outcome:
 //   "[HH:MM:SS] compiled successfully in 42ms"
@@ -191,6 +197,12 @@ function _onWatcherData(compileName, chunk) {
   entry.accumulator = lines.pop() // keep the incomplete trailing fragment
 
   for (const line of lines) {
+    if (COMPILE_START_RE.test(line)) {
+      // New compile cycle — discard any output left over from a previous
+      // failed compile that didn't emit a "compiled with errors" footer.
+      entry.currentLines = []
+    }
+
     entry.currentLines.push(line)
     if (entry.currentLines.length > MAX_LOG_LINES) {
       entry.currentLines.shift()