llama.cpp constantly reprocessing huge prompts with opencode/pi.dev

I’m using llama-swap with llama.cpp. I mainly use opencode + pi.dev and I’m seeing frequent massive prompt reprocessing / prefills even tho the prompts are very similar between requests.

Example behavior:

• context grows to +50k tokens
• LCP similarity often shows 0.99+
• but sometimes n_past suddenly falls back to ~4-5k
• then llama.cpp reprocesses 40k+ tokens again
• TTFT jumps to multiple minutes

Example logs:

sim_best = 0.996 restored context checkpoint ... n_tokens = 4750 prompt eval time = 222411 ms / 44016 tokens 

Normal reuse looks fine:

prompt eval time = 473 ms / 19 tokens 

Current config:

llama-server --ctx-size 150000 --parallel 1 --ctx-checkpoints 32 --cache-ram 2500 --cache-reuse 256 -no-kvu --no-context-shift 

Also seeing:

cache state: 1 prompts, 4676 MiB (limits: 2500 MiB) 

I suspect either:

• cache invalidation
• bad KV reuse
• or opencode changing early prompt tokens too often.

Would love to hear from others running long-context coding agents with llama.cpp and what settings helped reduce huge prompt reprocessing.