HOW WE CUT GITLAB DUO CODE REVIEW'S COST BY 98%

Summary from the TLDR Dev newsletter

AI21 combined a switch to DeepSeek V4 Flash with context compaction to cut GitLab Duo Code Review's estimated token cost from $0.589 to $0.0135 per pull request on a public benchmark, with F1 rising from 46.4% to 47.2%. Compaction made oversized reviews fit the deployment's context window, removing expensive fallbacks to Sonnet.