fix: refuse flags verify-packs cannot honour

scripts/generate_pack.py

@@ -2421,6 +2421,19 @@ def main():
     # Quick-exit modes: --verify-packs alone = verify existing packs only
     # Combined with --all-variants, generation runs first then verify
     if args.verify_packs and not args.all_variants:
+        # This mode checks packs already on disk against the platform's own
+        # list. It reads the region priority above and nothing else, so a
+        # narrowing flag it cannot honour is refused rather than dropped: a
+        # dropped flag answers about an artifact the caller did not name, and
+        # an unknown target name reads as accepted.
+        for flag, given in (
+            ("--target", args.target),
+            ("--one-per-slot", args.one_per_slot),
+            ("--required-only", args.required_only),
+            ("--source", args.source != "full"),
+        ):
+            if given:
+                parser.error(f"{flag} is incompatible with --verify-packs")
         with _pack_output_lock(args.output_dir, exclusive=False):
             _run_verify_packs(args)
         return

tests/test_e2e.py

@@ -5814,6 +5814,19 @@ struct BurnDriver BurnDrvneogeo = {
              "refuse"),
             (["--platform", "retroarch", "--from-md5", "d8f1"], ["--one-per-slot"],
              "refuse"),
+            # --verify-packs returns before the argument checks run, so it used
+            # to accept all four of these -- an unknown target name included --
+            # and answer about the pack sitting in the output directory.
+            (["--platform", "retroarch", "--verify-packs"], ["--target", "switch"],
+             "refuse"),
+            (["--platform", "retroarch", "--verify-packs"], ["--target", "no-such-xyz"],
+             "refuse"),
+            (["--platform", "retroarch", "--verify-packs"], ["--one-per-slot"],
+             "refuse"),
+            (["--platform", "retroarch", "--verify-packs"], ["--required-only"],
+             "refuse"),
+            (["--platform", "retroarch", "--verify-packs"], ["--source", "truth"],
+             "refuse"),
         ]
         for mode, flag, expected in matrix:
             with self.subTest(mode=mode, flag=flag):