Orbit Blast Radius Reviewer

A GitLab Duo flow that uses GitLab Orbit's knowledge graph to automatically identify impacted services, dependencies, owners, and risk before a merge request is reviewed.

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Inspiration

Code review only ever shows you the diff in front of you. It never shows you what depends on the thing you just changed — until it breaks in a repo you've never opened, three teams away. GitLab Orbit exists specifically to answer "what's the blast radius of this change?" in one graph query instead of hours of manual cross-repo digging. We wanted to put that capability directly in the one place developers already look: the merge request itself.

What it does

Orbit Blast Radius Reviewer is a custom flow on the GitLab Duo Agent Platform. It triggers when a merge request is opened or updated, reads the diff to find which functions changed, queries Orbit's knowledge graph (query_graph) for every caller, downstream dependent, and owning team/project across the whole indexed group, and posts a short, graph-grounded "Blast Radius Report" as a comment — risk level, affected repos, and suggested reviewers, all before a human reviewer opens the diff tab.

How we built it

The flow is defined with the GitLab Duo Agent Platform's v1 custom flow schema: a single AgentComponent whose system prompt instructs it to identify changed symbols from the MR diff, call Orbit's query_graph tool with a multi-hop traversal that returns callers, owning projects, and owners in one call, and synthesize a strict, no-fabrication report format. We paired the flow with an Orbit skill (SKILL.md) containing ready-to-use query DSL recipes.

Challenges we ran into

Making sure the agent never "fills in" a plausible-sounding answer when the graph returns nothing. We made "no callers found" an explicit, positively-framed output, not a failure case.

What we learned

Orbit's value isn't making the LLM smarter about a codebase — it's replacing the LLM's job of inferring structure with the job of explaining structure already verified by indexed graph edges.

What's next

Pulling in recent pipeline failures along the same code path, and a /blast-radius slash command.

Built With

  • anthropic
  • claude
  • gitlab-duo-agent-platform
  • gitlab-orbit
  • knowledge-graph
  • markdown
  • mcp
  • yaml
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