Repository context (codebase awareness)
Everything an assistant knows about the project beyond the open file: structure, dependencies, conventions, related code — gathered by indexing or on-demand search.
Assistants without repository context produce plausible code that does not fit the codebase; with it, suggestions use existing helpers and follow local conventions. Products differ mainly in how they build this context (embeddings index, symbol graph, agentic grep). METR's trial of experienced developers on repositories of 1M+ lines is the hardest case: the developers' own context exceeded what the tools could supply, which is one explanation for the slowdown.