vllm - 💡(How to fix) Fix [Bug]: AssertFail

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Error Message

(APIServer pid=10264) INFO: Started server process [10264] (APIServer pid=10264) INFO: Waiting for application startup. (APIServer pid=10264) INFO: Application startup complete. (APIServer pid=10264) INFO: 192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 200 OK (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] EngineCore encountered a fatal error. (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] Traceback (most recent call last): (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] engine_core.run_busy_loop() (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] self._process_engine_step() (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] outputs, model_executed = self.step_fn() (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] ^^^^^^^^^^^^^^ (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] scheduler_output = self.scheduler.schedule() (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] ^^^^^^^^^^^^^^^^^^^^^^^^^ (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] self.connector.get_num_new_matched_tokens( (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] return self.connector_scheduler.get_num_new_matched_tokens( (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] num_hit_tokens = self._lookup(req_status) (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] ^^^^^^^^^^^^^^^^^^^^^^^^ (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] len(offload_keys) (EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] AssertionError (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] AsyncLLM output_handler failed. (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] Traceback (most recent call last): (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] outputs = await engine_core.get_output_async() (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] raise self._format_exception(outputs) from None (APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause. (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Error in chat completion stream generator. (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Traceback (most recent call last): (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/entrypoints/openai/chat_completion/serving.py", line 496, in chat_completion_stream_generator (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] async for res in result_generator: (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 579, in generate (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] out = q.get_nowait() or await q.get() (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] ^^^^^^^^^^^^^ (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/output_processor.py", line 88, in get (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] raise output (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] outputs = await engine_core.get_output_async() (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] raise self._format_exception(outputs) from None (APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause. (EngineCore pid=10413) Process EngineCore: (EngineCore pid=10413) Traceback (most recent call last): (EngineCore pid=10413) File "/usr/lib/python3.12/multiprocessing/process.py", line 314, in _bootstrap (EngineCore pid=10413) self.run() (EngineCore pid=10413) File "/usr/lib/python3.12/multiprocessing/process.py", line 108, in run (EngineCore pid=10413) self._target(*self._args, **self._kwargs) (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1144, in run_engine_core (EngineCore pid=10413) raise e (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core (EngineCore pid=10413) engine_core.run_busy_loop() (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop (EngineCore pid=10413) self._process_engine_step() (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step (EngineCore pid=10413) outputs, model_executed = self.step_fn() (EngineCore pid=10413) ^^^^^^^^^^^^^^ (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue (EngineCore pid=10413) scheduler_output = self.scheduler.schedule() (EngineCore pid=10413) ^^^^^^^^^^^^^^^^^^^^^^^^^ (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule (EngineCore pid=10413) self.connector.get_num_new_matched_tokens( (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens (EngineCore pid=10413) return self.connector_scheduler.get_num_new_matched_tokens( (EngineCore pid=10413) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens (EngineCore pid=10413) num_hit_tokens = self._lookup(req_status) (EngineCore pid=10413) ^^^^^^^^^^^^^^^^^^^^^^^^ (EngineCore pid=10413) File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup (EngineCore pid=10413) len(offload_keys) (EngineCore pid=10413) AssertionError (APIServer pid=10264) INFO: 192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 500 Internal Server Error (APIServer pid=10264) INFO: Shutting down

Root Cause

Crash Log;

(APIServer pid=10264) INFO:     Started server process [10264]
(APIServer pid=10264) INFO:     Waiting for application startup.
(APIServer pid=10264) INFO:     Application startup complete.
(APIServer pid=10264) INFO:     192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 200 OK
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] EngineCore encountered a fatal error.
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] Traceback (most recent call last):
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     engine_core.run_busy_loop()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     self._process_engine_step()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     outputs, model_executed = self.step_fn()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                               ^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     scheduler_output = self.scheduler.schedule()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                        ^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     self.connector.get_num_new_matched_tokens(
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     return self.connector_scheduler.get_num_new_matched_tokens(
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     num_hit_tokens = self._lookup(req_status)
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                      ^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     len(offload_keys)
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] AssertionError
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] AsyncLLM output_handler failed.
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] Traceback (most recent call last):
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]     outputs = await engine_core.get_output_async()
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]     raise self._format_exception(outputs) from None
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause.
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Error in chat completion stream generator.
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Traceback (most recent call last):
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/entrypoints/openai/chat_completion/serving.py", line 496, in chat_completion_stream_generator
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     async for res in result_generator:
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 579, in generate
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     out = q.get_nowait() or await q.get()
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]                             ^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/output_processor.py", line 88, in get
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     raise output
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     outputs = await engine_core.get_output_async()
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     raise self._format_exception(outputs) from None
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause.
(EngineCore pid=10413) Process EngineCore:
(EngineCore pid=10413) Traceback (most recent call last):
(EngineCore pid=10413)   File "/usr/lib/python3.12/multiprocessing/process.py", line 314, in _bootstrap
(EngineCore pid=10413)     self.run()
(EngineCore pid=10413)   File "/usr/lib/python3.12/multiprocessing/process.py", line 108, in run
(EngineCore pid=10413)     self._target(*self._args, **self._kwargs)
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1144, in run_engine_core
(EngineCore pid=10413)     raise e
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core
(EngineCore pid=10413)     engine_core.run_busy_loop()
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop
(EngineCore pid=10413)     self._process_engine_step()
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step
(EngineCore pid=10413)     outputs, model_executed = self.step_fn()
(EngineCore pid=10413)                               ^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue
(EngineCore pid=10413)     scheduler_output = self.scheduler.schedule()
(EngineCore pid=10413)                        ^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule
(EngineCore pid=10413)     self.connector.get_num_new_matched_tokens(
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens
(EngineCore pid=10413)     return self.connector_scheduler.get_num_new_matched_tokens(
(EngineCore pid=10413)            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens
(EngineCore pid=10413)     num_hit_tokens = self._lookup(req_status)
(EngineCore pid=10413)                      ^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup
(EngineCore pid=10413)     len(offload_keys)
(EngineCore pid=10413) AssertionError
(APIServer pid=10264) INFO:     192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 500 Internal Server Error
(APIServer pid=10264) INFO:     Shutting down

Fix Action

Fix / Workaround

============================== CPU Info

Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Address sizes: 46 bits physical, 48 bits virtual Byte Order: Little Endian CPU(s): 44 On-line CPU(s) list: 0-43 Vendor ID: GenuineIntel Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz CPU family: 6 Model: 79 Thread(s) per core: 2 Core(s) per socket: 22 Socket(s): 1 Stepping: 1 CPU(s) scaling MHz: 41% CPU max MHz: 3600.0000 CPU min MHz: 1200.0000 BogoMIPS: 4389.89 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 pti intel_ppin ssbd ibrs ibpb stibp tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm rdt_a rdseed adx smap intel_pt xsaveopt cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts vnmi md_clear flush_l1d ibpb_exit_to_user Virtualization: VT-x L1d cache: 704 KiB (22 instances) L1i cache: 704 KiB (22 instances) L2 cache: 5.5 MiB (22 instances) L3 cache: 55 MiB (1 instance) NUMA node(s): 1 NUMA node0 CPU(s): 0-43 Vulnerability Gather data sampling: Not affected Vulnerability Indirect target selection: Not affected Vulnerability Itlb multihit: KVM: Mitigation: VMX disabled Vulnerability L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable Vulnerability Mds: Mitigation; Clear CPU buffers; SMT vulnerable Vulnerability Meltdown: Mitigation; PTI Vulnerability Mmio stale data: Mitigation; Clear CPU buffers; SMT vulnerable Vulnerability Reg file data sampling: Not affected Vulnerability Retbleed: Not affected Vulnerability Spec rstack overflow: Not affected Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization Vulnerability Spectre v2: Mitigation; Retpolines; IBPB conditional; IBRS_FW; STIBP conditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected Vulnerability Srbds: Not affected Vulnerability Tsa: Not affected Vulnerability Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable Vulnerability Vmscape: Mitigation; IBPB before exit to userspace

Code Example

==============================
        System Info
==============================
OS                           : Ubuntu 24.04.4 LTS (x86_64)
GCC version                  : (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0
Clang version                : 18.1.3 (1ubuntu1)
CMake version                : Could not collect
Libc version                 : glibc-2.39

==============================
       PyTorch Info
==============================
PyTorch version              : 2.11.0+cu130
Is debug build               : False
CUDA used to build PyTorch   : 13.0
ROCM used to build PyTorch   : N/A
XPU used to build PyTorch    : N/A

==============================
      Python Environment
==============================
Python version               : 3.12.3 (main, Mar 23 2026, 19:04:32) [GCC 13.3.0] (64-bit runtime)
Python platform              : Linux-6.8.0-117-generic-x86_64-with-glibc2.39

==============================
       CUDA / GPU Info
==============================
Is CUDA available            : True
CUDA runtime version         : 12.0.140
CUDA_MODULE_LOADING set to   :
GPU models and configuration : GPU 0: NVIDIA RTX 4000 Ada Generation
Nvidia driver version        : 595.71.05
cuDNN version                : Could not collect
HIP runtime version          : N/A
MIOpen runtime version       : N/A
Is XNNPACK available         : True

==============================
          CPU Info
==============================
Architecture:                            x86_64
CPU op-mode(s):                          32-bit, 64-bit
Address sizes:                           46 bits physical, 48 bits virtual
Byte Order:                              Little Endian
CPU(s):                                  44
On-line CPU(s) list:                     0-43
Vendor ID:                               GenuineIntel
Model name:                              Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz
CPU family:                              6
Model:                                   79
Thread(s) per core:                      2
Core(s) per socket:                      22
Socket(s):                               1
Stepping:                                1
CPU(s) scaling MHz:                      41%
CPU max MHz:                             3600.0000
CPU min MHz:                             1200.0000
BogoMIPS:                                4389.89
Flags:                                   fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 pti intel_ppin ssbd ibrs ibpb stibp tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm rdt_a rdseed adx smap intel_pt xsaveopt cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts vnmi md_clear flush_l1d ibpb_exit_to_user
Virtualization:                          VT-x
L1d cache:                               704 KiB (22 instances)
L1i cache:                               704 KiB (22 instances)
L2 cache:                                5.5 MiB (22 instances)
L3 cache:                                55 MiB (1 instance)
NUMA node(s):                            1
NUMA node0 CPU(s):                       0-43
Vulnerability Gather data sampling:      Not affected
Vulnerability Indirect target selection: Not affected
Vulnerability Itlb multihit:             KVM: Mitigation: VMX disabled
Vulnerability L1tf:                      Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable
Vulnerability Mds:                       Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown:                  Mitigation; PTI
Vulnerability Mmio stale data:           Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Reg file data sampling:    Not affected
Vulnerability Retbleed:                  Not affected
Vulnerability Spec rstack overflow:      Not affected
Vulnerability Spec store bypass:         Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:                Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:                Mitigation; Retpolines; IBPB conditional; IBRS_FW; STIBP conditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds:                     Not affected
Vulnerability Tsa:                       Not affected
Vulnerability Tsx async abort:           Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Vmscape:                   Mitigation; IBPB before exit to userspace

==============================
Versions of relevant libraries
==============================
[pip3] flashinfer-python==0.6.8.post1
[pip3] numpy==2.3.5
[pip3] nvidia-cublas==13.1.0.3
[pip3] nvidia-cuda-cupti==13.0.85
[pip3] nvidia-cuda-nvrtc==13.0.88
[pip3] nvidia-cuda-runtime==13.0.96
[pip3] nvidia-cudnn-cu13==9.19.0.56
[pip3] nvidia-cudnn-frontend==1.18.0
[pip3] nvidia-cufft==12.0.0.61
[pip3] nvidia-cufile==1.15.1.6
[pip3] nvidia-curand==10.4.0.35
[pip3] nvidia-cusolver==12.0.4.66
[pip3] nvidia-cusparse==12.6.3.3
[pip3] nvidia-cusparselt-cu13==0.8.0
[pip3] nvidia-cutlass-dsl==4.4.2
[pip3] nvidia-cutlass-dsl-libs-base==4.4.2
[pip3] nvidia-ml-py==13.595.45
[pip3] nvidia-nccl-cu13==2.28.9
[pip3] nvidia-nvjitlink==13.0.88
[pip3] nvidia-nvshmem-cu13==3.4.5
[pip3] nvidia-nvtx==13.0.85
[pip3] pyzmq==27.1.0
[pip3] tokenspeed-triton==3.7.10.post20260505
[pip3] torch==2.11.0+cu130
[pip3] torch_c_dlpack_ext==0.1.5
[pip3] torchaudio==2.11.0+cu130
[pip3] torchvision==0.26.0+cu130
[pip3] transformers==5.9.0
[pip3] triton==3.6.0
[conda] Could not collect

==============================
         vLLM Info
==============================
ROCM Version                 : Could not collect
vLLM Version                 : 0.21.0
vLLM Build Flags:
  CUDA Archs: Not Set; ROCm: Disabled; XPU: Disabled
GPU Topology:
        GPU0    CPU Affinity    NUMA Affinity   GPU NUMA ID
GPU0     X      0-43    0               N/A

Legend:

  X    = Self
  SYS  = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI)
  NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node
  PHB  = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU)
  PXB  = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge)
  PIX  = Connection traversing at most a single PCIe bridge
  NV#  = Connection traversing a bonded set of # NVLinks

==============================
     Environment Variables
==============================
PYTORCH_NVML_BASED_CUDA_CHECK=1
TORCHINDUCTOR_COMPILE_THREADS=1
TORCHINDUCTOR_CACHE_DIR=/tmp/torchinductor_alsutton

---

uv run vllm serve Qwen/Qwen3.5-4B --host 0.0.0.0 --port 8000  --max-model-len 196416 --reasoning-parser qwen3 --enable-auto-tool-choice --tool-call-parser qwen3_coder --kv_offloading_backend native --kv_offloading_size 32

---

(APIServer pid=10264) INFO:     Started server process [10264]
(APIServer pid=10264) INFO:     Waiting for application startup.
(APIServer pid=10264) INFO:     Application startup complete.
(APIServer pid=10264) INFO:     192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 200 OK
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] EngineCore encountered a fatal error.
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] Traceback (most recent call last):
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     engine_core.run_busy_loop()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     self._process_engine_step()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     outputs, model_executed = self.step_fn()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                               ^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     scheduler_output = self.scheduler.schedule()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                        ^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     self.connector.get_num_new_matched_tokens(
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     return self.connector_scheduler.get_num_new_matched_tokens(
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     num_hit_tokens = self._lookup(req_status)
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                      ^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     len(offload_keys)
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] AssertionError
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] AsyncLLM output_handler failed.
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] Traceback (most recent call last):
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]     outputs = await engine_core.get_output_async()
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]     raise self._format_exception(outputs) from None
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause.
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Error in chat completion stream generator.
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Traceback (most recent call last):
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/entrypoints/openai/chat_completion/serving.py", line 496, in chat_completion_stream_generator
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     async for res in result_generator:
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 579, in generate
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     out = q.get_nowait() or await q.get()
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]                             ^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/output_processor.py", line 88, in get
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     raise output
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     outputs = await engine_core.get_output_async()
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     raise self._format_exception(outputs) from None
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause.
(EngineCore pid=10413) Process EngineCore:
(EngineCore pid=10413) Traceback (most recent call last):
(EngineCore pid=10413)   File "/usr/lib/python3.12/multiprocessing/process.py", line 314, in _bootstrap
(EngineCore pid=10413)     self.run()
(EngineCore pid=10413)   File "/usr/lib/python3.12/multiprocessing/process.py", line 108, in run
(EngineCore pid=10413)     self._target(*self._args, **self._kwargs)
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1144, in run_engine_core
(EngineCore pid=10413)     raise e
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core
(EngineCore pid=10413)     engine_core.run_busy_loop()
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop
(EngineCore pid=10413)     self._process_engine_step()
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step
(EngineCore pid=10413)     outputs, model_executed = self.step_fn()
(EngineCore pid=10413)                               ^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue
(EngineCore pid=10413)     scheduler_output = self.scheduler.schedule()
(EngineCore pid=10413)                        ^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule
(EngineCore pid=10413)     self.connector.get_num_new_matched_tokens(
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens
(EngineCore pid=10413)     return self.connector_scheduler.get_num_new_matched_tokens(
(EngineCore pid=10413)            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens
(EngineCore pid=10413)     num_hit_tokens = self._lookup(req_status)
(EngineCore pid=10413)                      ^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup
(EngineCore pid=10413)     len(offload_keys)
(EngineCore pid=10413) AssertionError
(APIServer pid=10264) INFO:     192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 500 Internal Server Error
(APIServer pid=10264) INFO:     Shutting down
RAW_BUFFERClick to expand / collapse

Your current environment

==============================
        System Info
==============================
OS                           : Ubuntu 24.04.4 LTS (x86_64)
GCC version                  : (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0
Clang version                : 18.1.3 (1ubuntu1)
CMake version                : Could not collect
Libc version                 : glibc-2.39

==============================
       PyTorch Info
==============================
PyTorch version              : 2.11.0+cu130
Is debug build               : False
CUDA used to build PyTorch   : 13.0
ROCM used to build PyTorch   : N/A
XPU used to build PyTorch    : N/A

==============================
      Python Environment
==============================
Python version               : 3.12.3 (main, Mar 23 2026, 19:04:32) [GCC 13.3.0] (64-bit runtime)
Python platform              : Linux-6.8.0-117-generic-x86_64-with-glibc2.39

==============================
       CUDA / GPU Info
==============================
Is CUDA available            : True
CUDA runtime version         : 12.0.140
CUDA_MODULE_LOADING set to   :
GPU models and configuration : GPU 0: NVIDIA RTX 4000 Ada Generation
Nvidia driver version        : 595.71.05
cuDNN version                : Could not collect
HIP runtime version          : N/A
MIOpen runtime version       : N/A
Is XNNPACK available         : True

==============================
          CPU Info
==============================
Architecture:                            x86_64
CPU op-mode(s):                          32-bit, 64-bit
Address sizes:                           46 bits physical, 48 bits virtual
Byte Order:                              Little Endian
CPU(s):                                  44
On-line CPU(s) list:                     0-43
Vendor ID:                               GenuineIntel
Model name:                              Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz
CPU family:                              6
Model:                                   79
Thread(s) per core:                      2
Core(s) per socket:                      22
Socket(s):                               1
Stepping:                                1
CPU(s) scaling MHz:                      41%
CPU max MHz:                             3600.0000
CPU min MHz:                             1200.0000
BogoMIPS:                                4389.89
Flags:                                   fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 pti intel_ppin ssbd ibrs ibpb stibp tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm rdt_a rdseed adx smap intel_pt xsaveopt cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts vnmi md_clear flush_l1d ibpb_exit_to_user
Virtualization:                          VT-x
L1d cache:                               704 KiB (22 instances)
L1i cache:                               704 KiB (22 instances)
L2 cache:                                5.5 MiB (22 instances)
L3 cache:                                55 MiB (1 instance)
NUMA node(s):                            1
NUMA node0 CPU(s):                       0-43
Vulnerability Gather data sampling:      Not affected
Vulnerability Indirect target selection: Not affected
Vulnerability Itlb multihit:             KVM: Mitigation: VMX disabled
Vulnerability L1tf:                      Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable
Vulnerability Mds:                       Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown:                  Mitigation; PTI
Vulnerability Mmio stale data:           Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Reg file data sampling:    Not affected
Vulnerability Retbleed:                  Not affected
Vulnerability Spec rstack overflow:      Not affected
Vulnerability Spec store bypass:         Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:                Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:                Mitigation; Retpolines; IBPB conditional; IBRS_FW; STIBP conditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds:                     Not affected
Vulnerability Tsa:                       Not affected
Vulnerability Tsx async abort:           Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Vmscape:                   Mitigation; IBPB before exit to userspace

==============================
Versions of relevant libraries
==============================
[pip3] flashinfer-python==0.6.8.post1
[pip3] numpy==2.3.5
[pip3] nvidia-cublas==13.1.0.3
[pip3] nvidia-cuda-cupti==13.0.85
[pip3] nvidia-cuda-nvrtc==13.0.88
[pip3] nvidia-cuda-runtime==13.0.96
[pip3] nvidia-cudnn-cu13==9.19.0.56
[pip3] nvidia-cudnn-frontend==1.18.0
[pip3] nvidia-cufft==12.0.0.61
[pip3] nvidia-cufile==1.15.1.6
[pip3] nvidia-curand==10.4.0.35
[pip3] nvidia-cusolver==12.0.4.66
[pip3] nvidia-cusparse==12.6.3.3
[pip3] nvidia-cusparselt-cu13==0.8.0
[pip3] nvidia-cutlass-dsl==4.4.2
[pip3] nvidia-cutlass-dsl-libs-base==4.4.2
[pip3] nvidia-ml-py==13.595.45
[pip3] nvidia-nccl-cu13==2.28.9
[pip3] nvidia-nvjitlink==13.0.88
[pip3] nvidia-nvshmem-cu13==3.4.5
[pip3] nvidia-nvtx==13.0.85
[pip3] pyzmq==27.1.0
[pip3] tokenspeed-triton==3.7.10.post20260505
[pip3] torch==2.11.0+cu130
[pip3] torch_c_dlpack_ext==0.1.5
[pip3] torchaudio==2.11.0+cu130
[pip3] torchvision==0.26.0+cu130
[pip3] transformers==5.9.0
[pip3] triton==3.6.0
[conda] Could not collect

==============================
         vLLM Info
==============================
ROCM Version                 : Could not collect
vLLM Version                 : 0.21.0
vLLM Build Flags:
  CUDA Archs: Not Set; ROCm: Disabled; XPU: Disabled
GPU Topology:
        GPU0    CPU Affinity    NUMA Affinity   GPU NUMA ID
GPU0     X      0-43    0               N/A

Legend:

  X    = Self
  SYS  = Connection traversing PCIe as well as the SMP interconnect between NUMA nodes (e.g., QPI/UPI)
  NODE = Connection traversing PCIe as well as the interconnect between PCIe Host Bridges within a NUMA node
  PHB  = Connection traversing PCIe as well as a PCIe Host Bridge (typically the CPU)
  PXB  = Connection traversing multiple PCIe bridges (without traversing the PCIe Host Bridge)
  PIX  = Connection traversing at most a single PCIe bridge
  NV#  = Connection traversing a bonded set of # NVLinks

==============================
     Environment Variables
==============================
PYTORCH_NVML_BASED_CUDA_CHECK=1
TORCHINDUCTOR_COMPILE_THREADS=1
TORCHINDUCTOR_CACHE_DIR=/tmp/torchinductor_alsutton

🐛 Describe the bug

AssertFail when making a request to the API Server

Initialisation command;

uv run vllm serve Qwen/Qwen3.5-4B --host 0.0.0.0 --port 8000  --max-model-len 196416 --reasoning-parser qwen3 --enable-auto-tool-choice --tool-call-parser qwen3_coder --kv_offloading_backend native --kv_offloading_size 32

Crash Log;

(APIServer pid=10264) INFO:     Started server process [10264]
(APIServer pid=10264) INFO:     Waiting for application startup.
(APIServer pid=10264) INFO:     Application startup complete.
(APIServer pid=10264) INFO:     192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 200 OK
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] EngineCore encountered a fatal error.
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] Traceback (most recent call last):
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     engine_core.run_busy_loop()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     self._process_engine_step()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     outputs, model_executed = self.step_fn()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                               ^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     scheduler_output = self.scheduler.schedule()
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                        ^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     self.connector.get_num_new_matched_tokens(
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     return self.connector_scheduler.get_num_new_matched_tokens(
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     num_hit_tokens = self._lookup(req_status)
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]                      ^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142]     len(offload_keys)
(EngineCore pid=10413) ERROR 05-25 10:43:35 [core.py:1142] AssertionError
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] AsyncLLM output_handler failed.
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] Traceback (most recent call last):
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]     outputs = await engine_core.get_output_async()
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704]     raise self._format_exception(outputs) from None
(APIServer pid=10264) ERROR 05-25 10:43:35 [async_llm.py:704] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause.
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Error in chat completion stream generator.
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] Traceback (most recent call last):
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/entrypoints/openai/chat_completion/serving.py", line 496, in chat_completion_stream_generator
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     async for res in result_generator:
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 579, in generate
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     out = q.get_nowait() or await q.get()
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]                             ^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/output_processor.py", line 88, in get
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     raise output
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/async_llm.py", line 660, in output_handler
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     outputs = await engine_core.get_output_async()
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core_client.py", line 998, in get_output_async
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997]     raise self._format_exception(outputs) from None
(APIServer pid=10264) ERROR 05-25 10:43:35 [serving.py:997] vllm.v1.engine.exceptions.EngineDeadError: EngineCore encountered an issue. See stack trace (above) for the root cause.
(EngineCore pid=10413) Process EngineCore:
(EngineCore pid=10413) Traceback (most recent call last):
(EngineCore pid=10413)   File "/usr/lib/python3.12/multiprocessing/process.py", line 314, in _bootstrap
(EngineCore pid=10413)     self.run()
(EngineCore pid=10413)   File "/usr/lib/python3.12/multiprocessing/process.py", line 108, in run
(EngineCore pid=10413)     self._target(*self._args, **self._kwargs)
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1144, in run_engine_core
(EngineCore pid=10413)     raise e
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1133, in run_engine_core
(EngineCore pid=10413)     engine_core.run_busy_loop()
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1174, in run_busy_loop
(EngineCore pid=10413)     self._process_engine_step()
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 1213, in _process_engine_step
(EngineCore pid=10413)     outputs, model_executed = self.step_fn()
(EngineCore pid=10413)                               ^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/engine/core.py", line 475, in step_with_batch_queue
(EngineCore pid=10413)     scheduler_output = self.scheduler.schedule()
(EngineCore pid=10413)                        ^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/v1/core/sched/scheduler.py", line 581, in schedule
(EngineCore pid=10413)     self.connector.get_num_new_matched_tokens(
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading_connector.py", line 124, in get_num_new_matched_tokens
(EngineCore pid=10413)     return self.connector_scheduler.get_num_new_matched_tokens(
(EngineCore pid=10413)            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 481, in get_num_new_matched_tokens
(EngineCore pid=10413)     num_hit_tokens = self._lookup(req_status)
(EngineCore pid=10413)                      ^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore pid=10413)   File "/home/alsutton/.venv/lib/python3.12/site-packages/vllm/distributed/kv_transfer/kv_connector/v1/offloading/scheduler.py", line 340, in _lookup
(EngineCore pid=10413)     len(offload_keys)
(EngineCore pid=10413) AssertionError
(APIServer pid=10264) INFO:     192.168.0.210:0 - "POST /v1/chat/completions HTTP/1.1" 500 Internal Server Error
(APIServer pid=10264) INFO:     Shutting down

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