The “same” model increasingly behaves like a different product depending on the inference stack behind it

Been noticing this more often lately while comparing different deployments of the same models. Most people assume model behavior is mostly defined by the weights themselves, but once sessions get longer the inference stack starts affecting the experience a lot more than expected. Things like scheduling, quantization, runtime configs, speculative decoding, queue pressure, context handling etc can noticeably change how stable/coherent the model feels over time. Short prompts usually hide this, but long coding or agent workflows expose it pretty quickly. Feels like we’re moving toward a world where “which model?” matters slightly less than “served how?”