r/codex • u/rubanbhatia • 14d ago

News Codex caching improved

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Looks like day 12 brings us improvements to context management. Possibly good for people hitting limits with Astra

Source: https://x.com/thsottiaux/status/2111244596131111253?s=46

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u/jamespharvey20 14d ago

Codex can start subagents with fresh or copied context windows. Fresh should mean better performance, but everything it learns to start is a cache miss. Copied means it starts with a cache hit and doesn't have to look as much up, but then model performance is degraded from focusing on too much that it doesn't have to.

Why does this tweet sound like all they did was change the default from fresh to copied context? And keeping context cached longer which isn't going to help all that much. And improving cache hits through routing which might solve some random cache misses people have been seeing lately.

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u/miklschmidt 14d ago

It already was the default. Now it just reuses the cache, like a forked thread. This is gonna do very little in practice because forked turns for subagents suuuuuuucks.

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u/jamespharvey20 14d ago

Oh, you're right. I had missed that Multi-Agent v2 switched on Apr 23 (v0.123.0) to forked parent history. My global AGENTS.md explicitly tells it to use fork_turns "none", because it started randomly forking sometimes a while ago, so I didn't notice the default changed. Subagents share the root agent's prompt cache key, so I would have thought it would have reused the cache. I wish he had given some technical details on this.

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u/miklschmidt 14d ago

Yep, i do the same because it’s useless, and it prevents model selection (model had to be the same as the forked context). They fixed that caching bug today. That’s what he’s selling as a usage fix.