# Plan before edits: seeing the change before it lands > Atlas drafts a change in a read-only plan agent that cannot write files, then asks before switching to a build agent to implement it. Atlas plans before it edits by running 2 separate agents. The plan agent is read-only: it can read your repository and draft an approach, but it cannot write a file. When the plan is complete Atlas asks whether to switch to the build agent, and only then can anything be written. In 2026 that separation is what lets you argue with an approach before it costs you a diff. ## Key takeaways - The plan agent is read-only and cannot write files. - Atlas asks before switching from planning to building. - You refine the approach while nothing in the tree is at risk. - Approved plans still pass through the per-edit diff and permission step. ## Why planning is a separate agent, not a prompt Asking a model to describe its plan first is 1 instruction it can ignore. Atlas instead runs planning in a read-only agent that has no write tool at all, so a plan cannot quietly become an edit halfway through a response. The difference matters most on the changes you would most want to review. A large refactor described in prose can look reasonable and still touch the wrong files. When the planning agent is structurally unable to write, the review step is guaranteed rather than requested, and the model's compliance is not part of your safety story. ## The handoff you approve When a plan is finished Atlas asks 1 question: whether to switch to the build agent and start implementing. Answering no leaves your working tree exactly as it was, and the plan stays available to revise or discard. This is the point where most of the value lands. Rejecting a plan costs nothing, because no file has been touched, and revising a plan is far cheaper than reviewing and reverting a set of edits that already exist. Teams that plan first tend to spend their review attention on the approach rather than on the diff. ## Planning and permissions reinforce each other Approving a plan does not approve its edits. Each file change still computes a unified diff and passes through the allow, ask, or deny permission check, so there are 2 independent gates between an idea and a written file. Planning catches the wrong approach; diff review catches the wrong implementation of a right approach. They fail differently, which is why Atlas keeps both rather than treating an approved plan as blanket consent for whatever the build agent decides to do next. ## FAQ ### Does Atlas plan before editing files? Yes. Atlas drafts a plan in a read-only plan agent that cannot write files, then asks before switching to a build agent to implement it. ### Can the plan agent change my code by accident? No. The plan agent has no write capability, so planning cannot modify your working tree regardless of what the model decides to do. ### What happens if I reject a plan? Nothing is written. Your working tree is unchanged and the plan can be revised or discarded. ### Does approving a plan approve all its edits? No. Every file edit still computes a unified diff and passes the allow, ask, or deny permission check before it is written. --- Canonical HTML: https://runatlas.sh/resources/features/plan-before-edits Source of truth: aeo_pages row `/resources/features/plan-before-edits` (segment: Platform) (this file is generated from it, never hand-edited). Licence: Atlas is proprietary with a free core. It is not open source and there is no public source repository.