alt Hacker NewsI think you're right about the cost/benefit trade-off in general, but I do wonder how much "compaction" Codex and Claude do is to keep context fresh and how much is to save (them) runtime costs.
If you've got a 1M token context, but they constantly summarize it down to something much smaller, is it really 1M tokens of benefit? With a local model, you can use all 256k tokens on your own terms. However, I don't have any benchmarks to know.
I think you might be confused a bit about compaction? The LLM API endpoint does not do compaction, it's an external agent harness that does it. And the Codex/Claude agents aren't constantly summarizing it down, they generally wait until you get within 3/4 of the max of the context size.
Compaction doesn't save them money, it just makes it possible for you to continue a session. If you compact a session too many times, besides the fact that the model basically stops being useful, you eventually just cannot do anything else in the session because all the context is taken up by compaction notes. But if you don't compact it, pretty soon the session is completely unusable because it can't output any more tokens. You can disable compaction in those agents if you want to see the difference.
Also, using a lot of context can make the model perform poorly, so compaction can improve results. If you have a much larger context size, it means you have more headroom before the model starts to perform poorly (as it grows closer to max context size). A larger context also lets you do things like handle larger documents or reason over a larger amount of data without having to break it up into subtasks. Eventually we want models' context to get much bigger so we can do more things in a session. (Some research is being done to see if we can get rid of the limit entirely)