AI BriefingBeyond API Compatibility: Building a Tool to Measure the Blast Radius of Library Changes
·2026.10.24 03:32
Key point
The tool uses SCIP to connect API definitions with consumer references, providing evidence on dependency versions and call sites before release.
Details
- Netflix developed Quasar to index symbol definitions and references across its repositories, allowing library producers to see the "blast radius" of API changes before merging.
- The system uses the SCIP format to store API definitions and consumer references in Amazon S3, enabling queries via Amazon Athena to identify specific repositories and dependency versions affected by a change.
- An illustrative report for a removed method identified 137 affected repositories, distributed across library versions 4.2.1 (86 repos), 4.1.7 (38 repos), and 3.9.4 (13 repos).
- Quasar currently supports usage queries for JVM, Go, Python, JavaScript/TypeScript, and Rust, but only assesses breaking API changes for JVM and Protobuf (traced through generated Java).
- The tool integrates with Model Context Protocol (MCP) to provide impact context to coding agents, aiming to move risk assessment earlier in the development lifecycle while keeping release decisions with human producers.
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