diff --git a/src/main.ts b/src/main.ts
index 0be8abb..5bea59e 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -169,8 +169,13 @@ async function run(): Promise<void> {
     summary.addScannedDependencies(changes)
     printScannedDependencies(changes)
 
-    // include full summary in output; Actions will truncate if oversized
+    // core.summary output must also be kept below 1024k
     let rendered = core.summary.stringify()
+    if (rendered.length >= summary.MAX_SUMMARY_LENGTH) {
+      rendered = rendered.substring(0, summary.MAX_SUMMARY_LENGTH)
+      core.summary.clear()
+      core.summary.addRaw(rendered)
+    }
     core.setOutput('comment-content', rendered)
 
     // if the summary is oversized, replace with minimal version
diff --git a/src/summary.ts b/src/summary.ts
index dc22ee2..d558dde 100644
--- a/src/summary.ts
+++ b/src/summary.ts
@@ -10,6 +10,8 @@ const icons = {
   warning: '⚠️'
 }
 
+export const MAX_SUMMARY_LENGTH = 1048576
+
 // generates the DR report summmary and caches it to the Action's core.summary.
 // returns the DR summary string, ready to be posted as a PR comment if the
 // final DR report is too large