Running Qwen 27B on 2x P40s: parallel agents wreck KV cache, seeking a serial agent harness

Jumpy-Operation-4615 · reddit · 2026-09-14

The author runs Qwen 27B locally on 2x NVIDIA P40s, hitting 45 tg/s and 450 prefill (dropping to 120 prefill at 150K+ ctx). Problem: running multiple opencode agents (orchestrator, fixer, oracle) concurrently destroys each other's KV cache and prefix caching collapses. They ask whether a serial harness exists — supervisor delegates, sleeps, and wakes only after a subagent finishes and writes a full handoff — keeping one process active at all times to preserve prefix caching.

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