Claude Code agents come in a few shapes, and it is worth being precise before we get to the part that breaks. There are sub-agents: specialized configurations you define in your .claude/ folder, each with its own instructions and tools, that the main session hands work to. There are agent teams: independent Claude Code sessions that coordinate through a shared task list and peer messaging, with one session acting as lead. And there is the plain case of running two terminals at once, each a full Claude Code session working the same repo.
All three are genuinely useful, and the setup guides for them are good. What none of the setup guides tell you is what happens on the second day, when the context window that held all the coordination fills up, compacts, and takes the plan with it. That is the problem this post is about, and it is not a prompting problem.
What actually breaks when you run more than one agent
A single Claude Code session holds its state in the context window. That works until it doesn't: the window fills, auto-compact runs, and the running summary of what got decided and why gets squeezed to make room. The next session starts cold. One of the highest-voted write-ups on this exact topic calls it "context amnesia," and the fix people reach for is almost always some external record the agents read from and write to, because in-context memory resets at the session boundary by design.
