Your agent reads whole files because that is all anyone gave it
rust
dev.to
Every coding agent I know pays the same tax: to change one function it reads the whole file. On a large repository that tax is the budget — context spent on code the agent will not touch, and a diff it cannot review because it never saw the file's shape. I built the structural half of the answer and made it boringly safe: opencrayast — an MCP server (plus a CLI on the same core) that lets an agent work on source code as a syntax tree: outline a file, fetch exactly one function, search by syntac