Module config 

EngineCfg + LongHoldConfig.

Structs

EngineCfg

Lock acquisition + max-hold guard configuration.

LongHoldConfig

Tuning for long-running (suspend/resume-capable) sessions and tasks — how long a poll/suspend may hold, how often heartbeats are expected, and whether idle tasks are kept alive across a detach.

SystemRefConfig

GH #31: server-side config for how a baked system_prompt too large to inline is delivered instead — see Engine::fetch_worker_payload’s threshold branch (crate::core::engine) for where this is consumed. Single server-side setting, not per-request: every fetch of a given (task_id, attempt) sees the same mode and threshold_bytes.