[refactor] Move model-capability adjustments into the resolution pipeline (#30299)

python/sglang/test/kits/attention_unittest/runner_modes/speculative_draft_runner.py

@@ -390,7 +390,9 @@ def _build_frozen_kv_mtp_fixture(
         runner_batch_size=settings.capture_batch_size,
     )
     _configure_runner_for_eagle_draft(fixture.runner, case, settings)
-    fixture.runner.server_args.speculative_algorithm = "FROZEN_KV_MTP"
+    fixture.runner.server_args.override(
+        "attention_unittest.frozen_kv_draft", speculative_algorithm="FROZEN_KV_MTP"
+    )
     fixture.runner.spec_algorithm = SpeculativeAlgorithm.FROZEN_KV_MTP
     fixture.runner.draft_attn_backend = fixture.backend
     fixture.runner.attn_backend = fixture.backend

python/sglang/test/test_utils.py

@@ -8,6 +8,10 @@ import inspect
 import json
 import logging
 import os
+
+# Registered tests run with the strict config-mutation guard: bare
+# server_args assignments after resolution raise (use ServerArgs.override).
+os.environ.setdefault("SGLANG_STRICT_CONFIG_MUTATION", "1")
 import random
 import re
 import shlex