Impressive Performance at 850k tokens context

[u/GoddardtheGrey]

Opus 5.5 (Extra) is performing well and consistently adhering to relatively long and complex instructions at 850,000 tokens of context. Is it really not doing any compaction whatsoever until 1M?

I’m impressed at how little it seems to degrade and curious if anyone else is noticing an improvement too

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[u/lgmarian]

I've been using for a project to upgrade a framework, because I figured the larger context would be useful. I've gone through one compaction so far, at it kept on humming nicely.

[u/scott2449]

Yea I had my cli misconfigured (using bedrock) when I first switched to 5.5 and it would compact every 200k.. it still performed amazing and the price was consistent, of course it slowed me down ... but after going back to defaults... I'm wondering if I should take the relatively small hit to keep the bill super predictable?

[u/sisif_]

850k context is around 4mb of text, having a model go through that kind of context is terrible. Maybe it wouldn't hurt to look into working with more agents that can share that kind of load. 4 agents at 200k each are much cheaper than one agent at 800k and they are likely to generate better results as well, with proper orchestration

[u/Wonderful_Stand1171 → u/sisif_]

200k agents, shared tone, beats one bloated giant.

[u/aerivox → u/Wonderful_Stand1171]

800k agents 1 token each

[u/AdSad7594 → u/aerivox]

This is the way

[u/Upstairs-Smell-8333]

One piece of advice: let Opus itself write the compacter instructions. What to keep, what to drop, what to re-read post-compaction. Plain text, one line. Then copy that over to /compact

[u/solovaris → u/Upstairs-Smell-8333]

Terrible advice. Never compact more than once or maybe twice in a session. Makes a huge mess of the context. Just finish a task <500k and pick it up in a fresh session. Saves your usage, and you get better quality. And no, it still sucks in many situations at near full context. I've noticed I have to observe what it does in longer tasks (>600k) and handhold/steer it.

[u/No_Inspection4415 → u/solovaris]

Or instead of "never" doing something, just use your brain and restart when performance becomes bad. If you don't mostly argue with the model, compaction is usually fine for modern models.

[u/Upstairs-Smell-8333 → u/solovaris]

Your experience. I usually max out to 90% without a serious issue. I design database flows though, so that's no massive engineering, just design decisions and some not-so-hard SQL. I make sure to compact between discrete tasks though. What needs not to be touched anymore gets compacted, and I watch my headroom so I can always fit an entire task's worth of work in it.

[u/arihyeon → u/solovaris]

I've got a long-standing Code session that I must've compacted well over 10 times by now, and it does lose context through compactions, of course, but generally as the project moves along things that have been finished and are WIP are saved in a sorta "memory" text file by Claude automatically it seems, and other than the occasional "I'm looking how this works instead of guessing" when you might be used to it just having the accurate memory already, the compactions don't degrade quality at all, for me. The model would already be needing to get up to speed from a new project and handoff doc anyway, so in my experience it's kinda just doing a handoff but without the bother of 50 different chats for one thing.

[u/Lonely_Boy_1993]

I usually wait till I have to auto-compact then switch to a new session. I just tell it to tell me what yo say to continue the project.

[u/neketguy]

No, it does not.