Code knowledge graph

A code knowledge graph is an index of a repository as symbols and relationships — call edges, imports, inheritance, tests — so an agent traverses dependencies rather than matching strings. This half has the actual evidence: RepoGraph, CodexGraph and LocAgent all report retrieval or localisation gains, and CodeCompass ran a controlled three-arm comparison against a plain agent and against BM25 retrieval. The finding that matters most for anyone building one is behavioural, not technical: across CodeCompass's 258 trials, 58% of the runs that had graph access made zero tool calls, and agents needed explicit prompting before they would use it at all. Building the index is the easy half.