What is Blast Radius?
Blast Radius is Refactron’s core safety mechanism. Every CodeIssue carries a mandatory BlastRadius object — it is never optional, never null. Before any fix is applied, Refactron knows exactly how many files, functions, and test files could be affected by that change.
interface BlastRadius {
affectedFiles: string[]; // files that transitively import the changed file
affectedFunctions: string[]; // functions in the call graph that reference the changed code
affectedTestFiles: string[]; // test files that cover the changed code
score: number; // 0–100 weighted impact score
level: BlastLevel; // trivial | low | medium | high | critical
}
The Score (0–100)
The score is a weighted sum of three factors:
| Factor | Weight | What it measures |
|---|
| Affected files | 40% | How many files transitively import the changed file |
| Affected functions | 40% | How many functions in the call graph reference the changed code |
| Test coverage gap | 20% | Penalty when affected code has no test coverage |
score = (normalised_files × 0.4) + (normalised_functions × 0.4) + (coverage_gap × 0.2)
Blast Levels
| Level | Score | Verification |
|---|
trivial | 0–10 | Syntax check only |
low | 11–25 | Syntax check only |
medium | 26–50 | Syntax + import resolution |
high | 51–75 | Syntax + imports + test gate |
critical | 76–100 | Full: syntax + imports + test suite (120s timeout) |
A critical blast radius fix will run your entire test suite before writing anything to disk. If any test fails, the fix is blocked.
How It Is Computed
1. Import Graph Traversal
Refactron builds a full transitive import graph of your project. For each file, it walks all direct and indirect importers:
changed: src/auth/token.ts
imported by: src/auth/index.ts
imported by: src/api/middleware.ts
imported by: src/api/routes.ts
imported by: src/server.ts
affectedFiles = [index.ts, middleware.ts, routes.ts, server.ts] → high score
2. Call Graph Analysis
Beyond file-level imports, Refactron traces function-level call relationships. If you change parseToken(), every function that directly or indirectly calls it is counted as affected.
3. Test Coverage Gap
If the changed code has no test files covering it, a 20% penalty is applied. If tests exist, the penalty is zero.
Reading Blast Radius in the Browser
In the interactive issue browser, blast radius is shown in the detail panel:
File: src/auth/token.ts:47 blast:high [fixable]
| Mark | Meaning |
|---|
· | Fixable, not yet fixed |
✔ | Fixed |
✓ | Fixed and verified safe |
✘ | Verified but blocked |
Why This Matters
Traditional approach (no blast radius)
eslint --fix src/ # fixes everything, no idea what broke
Refactron approach
Issue: Remove unused import 'os'
Blast: trivial (score: 2) — 0 files affected
→ Syntax check only, instant fix ✔
Issue: Refactor authenticate()
Blast: critical (score: 89) — 34 files affected, 0 test coverage
→ Full test suite runs before any write. Tests fail → fix blocked ✘
