Overplane

The prop

Move fast without breaking your things.

Coding agents earned their reputation for speed, and for the occasional catastrophe. Overplane keeps the speed and fixes the rest in three moves: contain the agent, wrap it in a real build system, and verify the plan before the code exists.

1. Your laptop is not a sandbox

   One agent deleted a production database during a code freeze. Another destroyed a user’s files while “reorganizing” them. Even the agent vendors now say unattended runs belong in a container behind an egress firewall.

   The fix

   In Overplane the container is not a best practice you set up later. It is the only way agents run: every agent, every build, the same locked-down container with a restricted view of your system. A bad day means deleting a sandbox, not restoring a backup.

2. A real build system for specs

   Most spec-driven tools are Markdown prompts riding inside your coding agent. Run one twice and you get two different codebases, with no record of which run produced what. There is a growing case that code generation now sits in the trusted computing base , where determinism and auditability stop being optional.

   The fix

   Overplane treats codegen like compilation: content-hashed sandbox images, content-addressable outputs, cached incremental builds you can replay down to a single spec, and a normalized dollar cost for every agent run. A real build system, where the compiler happens to be an agent.

3. Review the plan, not the 4,000-line diff

   96% of developers don’t fully trust AI-generated code, and over a third say reviewing it takes more effort than reviewing a colleague’s. Generated diffs are the new toil.

   The fix

   Review moves upstream, where it is cheap. You sign off on short numbered specs, Z3 checks them for contradictions before any code is written, and the checked IR can keep going: in the rustdis example it becomes 48 passing property tests and Kani proof harnesses guarding a wire-compatible Redis clone.