Inspiration
I spent two years building SigMap — "given a query, find the relevant code." MutationGuard is the inverse: "given code I'm about to change, what's relevant to worry about — and what should happen automatically?" Every developer changes existing code; almost none have a tool that shows the blast radius before the pipeline fails at 2am. GitLab Orbit finally makes it queryable.
What it does
Point it at a file or function. It reverse-traverses Orbit's CALLS/IMPORTS graph (depth 1–3) to find everything that could break, ranks each impacted file HIGH/MEDIUM/LOW (distance × coupling × git recency), lists the tests that touch the impacted code, and then TAKES AN ACTION: posts a pre-flight checklist and annotates the merge request. It ships as a published GitLab Duo agent on the AI Catalog, plus a CLI and a CI job.
How we built it
Orbit Local (DuckDB) and the Orbit Query DSL for the graph; verified the real ontology from source (nodes File/Definition/ImportedSymbol/Directory; edges CALLS/IMPORTS/DEFINES/CONTAINS/EXTENDS). Blast radius = reverse traversal of incoming CALLS/IMPORTS edges; coupling = an honest fan-in edge count; recency/ownership from git + CODEOWNERS. Impact score = (1/distance) × min(fan_in/20, 1) × (1.5 if modified ≤30d else 1.0). Packaged as a Duo AI Catalog agent (Orbit: Query Graph / Get Graph Schema / Invoke Command + Create Work Item Note / Update Work Item). Python, stdlib only, unit-tested, MIT.
Challenges we ran into
Grounding everything in Orbit's real interface instead of assumed APIs. A multi-repo graph leaked a foreign blast radius until I scoped every query by project_id. Identifying tests without an is_test flag (path conventions + edge references).
Accomplishments that we're proud of
Proven end-to-end on the real GitLab Orbit codebase (16,496 definitions): changing compile() surfaces 29 impacted files — 22 critical — 193 callers across 12 modules, with the exact calling functions and the tests that touch them. Honest by design: if Orbit is unavailable, it stops rather than guess.
What we learned
Orbit's graph is rich enough to turn "guess what might break" into a queryable, scored, actionable answer — and the win is the synthesis + action on top of the graph, not the query itself.
What's next for MutationGuard
Cross-repo blast radius for monorepos (Orbit Remote); an architecture-health view of high-fan-in hotspots; native MR-description decoration when an MR-write tool lands.
Log in or sign up for Devpost to join the conversation.