# Vllm Async Loading Debug > Debug vLLM async KV loading and PegaFlow connector behavior. Use when investigating async KV loads, WAITING_FOR_REMOTE_KVS states, load/save intents, connector metadata flow, prefetch behavior, or preemption interactions in vLLM scheduler/worker code. Use when this capability is needed. - Skill: `tomevault-io/vllm-async-loading-debug-2` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/vllm-async-loading-debug-2` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/vllm-async-loading-debug-2/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/vllm-async-loading-debug-2 --- # Vllm Async Loading Debug ## Overview Trace the async KV loading path between vLLM scheduler and worker connectors, including prefetch and preemption edges. ## Workflow ### 1) Confirm async-load symptom - Record request IDs and statuses: `WAITING`, `RUNNING`, `WAITING_FOR_REMOTE_KVS`, `PREEMPTED`. - Check async-load logs and whether prefetch is in progress. ### 2) Follow scheduler-side decisions - `python/pegaflow/connector/scheduler.py`: prefetch query + `LoadIntent` creation. - `.project-plans/scheduler.py` (private): `load_kv_async` gating and `WAITING_FOR_REMOTE_KVS` transitions. ### 3) Follow worker-side lifecycle - `python/pegaflow/connector/worker.py`: `start_load_kv()` calls `engine_client.load()` and tracks `PyLoadState`. - `get_finished()` polls `is_ready()` and emits `finished_recving`. ### 4) Check preemption and retries - `.project-plans/scheduler.py` (private): `_preempt_request()` and `reset_prefix_cache()` behavior. - `invalid_block_ids` handling can trigger recompute or failure based on `kv_load_failure_policy`. ## Reference Files - Read `references/async-loading.md` for full call flow and log markers. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/novitalabs) — claim your Tome and manage your conversions.