diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 57a4a002..91f3c2fc 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -33,6 +33,7 @@ sections to include in release notes:
 
 ### Fixed
 - Return a non-zero exit status from the unit test runner when a test fails or is missing. (#432)
+- Report restart checkpoint write or close failures and exit with file write error status 11, including in quiet mode. (#420)
 - Restore format specifiers for stock value in `ensureNonNegative()` error logging to align arguments and prevent undefined behavior. (#406)
 - Terminating harvest events will now remove all biomass at end of time step, instead of allowing small amounts to remain in the plant pools due to growth in that step. (#400)
 - Leaf-off mechanics refined to ensure that leaf-off events do not remove more leaf carbon than is available in the leaf pool. (#400)
diff --git a/src/common/exitCodes.h b/src/common/exitCodes.h
index 2c399490..26052738 100644
--- a/src/common/exitCodes.h
+++ b/src/common/exitCodes.h
@@ -21,6 +21,7 @@ typedef enum {
   EXIT_CODE_UNKNOWN_EVENT_TYPE_OR_PARAM = 4,
   EXIT_CODE_INPUT_FILE_ERROR = 5,
   EXIT_CODE_FILE_OPEN_OR_READ_ERROR = 6,
+  EXIT_CODE_FILE_CLOSE_OR_WRITE_ERROR = 11,
   EXIT_CODE_INTERNAL_ERROR = 7,
   EXIT_CODE_BAD_CLI_ARGUMENT = 8,
   EXIT_CODE_BAD_RESTART_PARAMETER = 9,
diff --git a/src/sipnet/restart.c b/src/sipnet/restart.c
index 7541a991..514473ab 100644
--- a/src/sipnet/restart.c
+++ b/src/sipnet/restart.c
@@ -829,7 +829,13 @@ static void writeRestartState(const char *restartOut, const RestartState *state,
 
   fprintf(out, "end_restart 1\n");
 
-  fclose(out);
+  int writeFailed = ferror(out);
+  // Always close the stream: buffered writes can fail during the final flush.
+  int closeFailed = fclose(out);
+  if (writeFailed || closeFailed != 0) {
+    logError("Failed to write restart checkpoint '%s'\n", restartOut);
+    exit(EXIT_CODE_FILE_CLOSE_OR_WRITE_ERROR);
+  }
 }
 
 static void checkRestartContextCompatibility(void) {
diff --git a/tests/sipnet/test_restart_infrastructure/testRestartMVP.c b/tests/sipnet/test_restart_infrastructure/testRestartMVP.c
index a40265e1..8f6db38a 100644
--- a/tests/sipnet/test_restart_infrastructure/testRestartMVP.c
+++ b/tests/sipnet/test_restart_infrastructure/testRestartMVP.c
@@ -716,6 +716,40 @@ static int testMalformedCheckpointFails(void) {
   return status;
 }
 
+static int testCheckpointWriteFailure(void) {
+  logTest("Starting testCheckpointWriteFailure\n");
+
+  if (access("/dev/full", W_OK) != 0) {
+    logTest("Skipping checkpoint write failure test: /dev/full unavailable\n");
+    return 0;
+  }
+
+  int status = prepRunFiles("restart_segment1.clim", "events_segment1.in");
+  if (status) {
+    logTest("Failed to prepare files for checkpoint write failure test\n");
+    return status;
+  }
+
+  const char *args[] = {
+      "--restart-out /dev/full --no-do-main-output --no-quiet",
+      "--restart-out /dev/full --no-do-main-output --quiet"};
+  const char *logs[] = {"checkpoint_write_failure.log",
+                        "checkpoint_write_failure_quiet.log"};
+  for (int i = 0; i < 2; ++i) {
+    int rc = runModelWithArgs("restart_seg1.in", logs[i], args[i]);
+    int failed = (rc != EXIT_CODE_FILE_CLOSE_OR_WRITE_ERROR);
+    failed |= !fileContains(logs[i], "[ERROR  ]");
+    failed |= !fileContains(logs[i],
+                            "Failed to write restart checkpoint '/dev/full'");
+    if (failed) {
+      logTest("Checkpoint write failure test failed (quiet=%d, rc=%d)\n", i,
+              rc);
+    }
+    status |= failed;
+  }
+  return status;
+}
+
 int run(void) {
   int status = 0;
 
@@ -734,6 +768,7 @@ int run(void) {
   status |= testBuildInfoMismatchWarnsAndSucceeds();
   status |= testTruncatedCheckpointFails();
   status |= testMalformedCheckpointFails();
+  status |= testCheckpointWriteFailure();
 
   return status;
 }