diff --git a/scripts/ci-run-timings.mjs b/scripts/ci-run-timings.mjs
index eb701665150..6cec3e244c1 100644
--- a/scripts/ci-run-timings.mjs
+++ b/scripts/ci-run-timings.mjs
@@ -386,7 +386,13 @@ export function parseRunTimingArgs(args) {
       index = recentOption.nextIndex;
       continue;
     }
-    explicitRunId ??= arg;
+    if (arg.startsWith("-")) {
+      throw new Error(`Unknown CI run timing option: ${arg}`);
+    }
+    if (explicitRunId) {
+      throw new Error(`Unexpected CI run id argument: ${arg}`);
+    }
+    explicitRunId = arg;
   }
 
   return {
@@ -409,9 +415,13 @@ function consumePositiveIntFlag(args, index, flag) {
   if (arg !== flag) {
     return null;
   }
+  const rawValue = args[index + 1];
+  if (!rawValue || rawValue.startsWith("--")) {
+    throw new Error(`${flag} requires a value`);
+  }
   return {
     nextIndex: index + 1,
-    value: parsePositiveInt(args[index + 1], flag),
+    value: parsePositiveInt(rawValue, flag),
   };
 }
 
diff --git a/test/scripts/ci-run-timings.test.ts b/test/scripts/ci-run-timings.test.ts
index 5d4942f801f..73c0c5ba0ea 100644
--- a/test/scripts/ci-run-timings.test.ts
+++ b/test/scripts/ci-run-timings.test.ts
@@ -257,9 +257,23 @@ describe("scripts/ci-run-timings.mjs", () => {
       ["--limit=1e3"],
       ["--recent", "recent"],
       ["--recent", "0"],
-      ["--recent"],
     ]) {
       expect(() => parseRunTimingArgs(args)).toThrow("must be a positive integer");
     }
   });
+
+  it("rejects missing monitor limits instead of treating flags as values", () => {
+    for (const args of [["--limit"], ["--limit", "--recent", "4"], ["--recent"]]) {
+      expect(() => parseRunTimingArgs(args)).toThrow("requires a value");
+    }
+  });
+
+  it("rejects unknown monitor flags and duplicate run ids", () => {
+    expect(() => parseRunTimingArgs(["--run-id", "123456"])).toThrow(
+      "Unknown CI run timing option: --run-id",
+    );
+    expect(() => parseRunTimingArgs(["123456", "789012"])).toThrow(
+      "Unexpected CI run id argument: 789012",
+    );
+  });
 });