A Harvard study using Jellyfish’s analytics platform examined 718 companies and about 300 million work events from January 2021 to March 2026. AI coding assistants raised lines of code by 12% and commits by 9%, while AI agents lifted lines of code by 30% and commits by 20%. However, the number of Jira issues resolved per worker rose only 12% with agents and not at all with assistants. The extra code created longer pull‑request reviews – review time grew 49%, comments per PR rose 53%, and the share of PRs needing changes doubled.
Why it matters
Engineering managers see that adding AI code generators may require more review capacity, so they must plan for extra QA resources.
