And agents that fail to comprehend the context correctly get stopped quickly.
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But let me spell out my original comment, to clarify:
Agents are like interns: they come to do the job, having none of the knowledge specific to your codebase and company. They have no time, to properly study the whole thing. They get a task, and are expected to figure it out (with help of documentation and people). Then they do the thing, and regardless of the outcome, are gone few months later, and you never hear from them again.
(In many companies, for various reasons, juniors are effectively interns with larger context window.)
In large companies with large projects, everything is moving so fast that no one - no one - can possibly understand the whole thing, and the work paradigm is purposefully structured so they don't need to. In some sense, they're like perpetual interns - each time they start working on different area of the project, they know next to nothing about it, and do not have a chance to fully comprehend it. They just need to figure out enough to deliver on their tasks.
(I know, because I like understanding things, and in one place I was told explicitly it's a common trap for people like me, and I need to learn to suppress it if I am to be effective at my job.)
Unsurprisingly, this works. Both examples are proof positive that this way of working is sustainable and scales well. It may not be optimal, but it works, which means agentic version of it has every right to work and scale as well.