diff --git a/tests/test_suites/disabled.txt b/tests/test_suites/disabled.txt
index d5ee913e6d9..64e331cac70 100644
--- a/tests/test_suites/disabled.txt
+++ b/tests/test_suites/disabled.txt
@@ -2,6 +2,8 @@
 # Disable this due to known vLLM crash issue with Qwen3.5: https://github.com/vllm-project/vllm/issues/36237
 tests/test_suites/vlm/vlm_grpo-qwen3.5-35ba3b-geo3k-2n8g-automodel-ep16.sh
 tests/test_suites/vlm/vlm_grpo-qwen3.5-35ba3b-geo3k-2n8g-megatron-ep16.sh
+# Flaky hang (passes on rerun); same vLLM issue, unresolved as of vLLM 0.20. Re-enable after next vLLM bump.
+tests/test_suites/llm/grpo-qwen3.5-35ba3b-2n8g-automodel-ep16.sh
 
 # Disable this due to know vLLM bug with Qwen3.5: https://github.com/vllm-project/vllm/issues/37856
 tests/test_suites/llm/grpo-qwen3.5-397ba17b-32n8g-megatron.v2.sh
diff --git a/tests/test_suites/nightly.txt b/tests/test_suites/nightly.txt
index 3ae22fb085a..94647393d2a 100644
--- a/tests/test_suites/nightly.txt
+++ b/tests/test_suites/nightly.txt
@@ -32,7 +32,8 @@ tests/test_suites/llm/grpo-moonlight-16ba3b-4n8g-megatron.sh
 tests/test_suites/llm/grpo-qwen3.5-9b-1n8g-megatron.sh
 
 # Functional Qwen3.5-35B run (text-only task)
-tests/test_suites/llm/grpo-qwen3.5-35ba3b-2n8g-automodel-ep16.sh
+# Disabled due to known flaky vLLM hang with Qwen3.5 (see disabled.txt): https://github.com/vllm-project/vllm/issues/36237
+# tests/test_suites/llm/grpo-qwen3.5-35ba3b-2n8g-automodel-ep16.sh
 tests/test_suites/llm/grpo-qwen3.5-35ba3b-2n8g-megatron-ep16tp2cp2.sh
 
 # Functional VLM run