diff --git a/src/lens_map.c b/src/lens_map.c
index f4a007c..92aedf6 100644
--- a/src/lens_map.c
+++ b/src/lens_map.c
@@ -297,6 +297,7 @@ int lens_map_read(const char *path, LensMapProvenance *provenance,
           read_u32(file, &end_id, &crc) || read_u32(file, &outcome, &crc) ||
           read_u32(file, &reason, &crc) || outcome > RAY_OUTCOME_INCOMPLETE ||
           !ray_reason_valid((RayReason)reason);
+      if (failed) break;
       v->end_id = (SpacetimeEndId)end_id;
       v->outcome = (RayOutcome)outcome;
       v->reason = (RayReason)reason;
diff --git a/tests/test_frame.c b/tests/test_frame.c
index e1f080b..589b114 100644
--- a/tests/test_frame.c
+++ b/tests/test_frame.c
@@ -1469,6 +1469,31 @@ int main(void) {
       lens_map_destroy(&dloaded); unlink(dp_path); goto done;
     }
     lens_map_destroy(&dloaded);
+    /* Truncate within the first v3 vertex, including each terminal field.
+     * Failed reads must reject the map and release its partially read mesh. */
+    {
+      unsigned char prefix[316];
+      FILE *fixture = fopen(dp_path, "rb");
+      int fixture_failed = fixture == NULL ||
+          fread(prefix, 1, sizeof prefix, fixture) != sizeof prefix;
+      if (fixture != NULL && fclose(fixture)) fixture_failed = 1;
+      if (fixture_failed) {
+        fputs("lens-map truncation fixture read failed\n", stderr);
+        unlink(dp_path); goto done;
+      }
+      const size_t cuts[] = {232, 303, 304, 307, 308, 311, 312, 315};
+      for (size_t c = 0; c < sizeof cuts / sizeof cuts[0]; ++c) {
+        FILE *short_file = fopen(dp_path, "wb");
+        int short_failed = short_file == NULL ||
+            fwrite(prefix, 1, cuts[c], short_file) != cuts[c];
+        if (short_file != NULL && fclose(short_file)) short_failed = 1;
+        if (short_failed || !lens_map_read(dp_path, NULL, &dloaded) ||
+            dloaded.frames != NULL || dloaded.frame_count != 0) {
+          fputs("lens-map truncated vertex rejection regression failed\n", stderr);
+          lens_map_destroy(&dloaded); unlink(dp_path); goto done;
+        }
+      }
+    }
     /* Unknown wire code and non-finite/out-of-bounds DP fields must be rejected
      * by the shared schema validator, not accepted as a usable map. */
     {