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Blast radius

What it is

Blast radius is the structural risk boundary around a set of files you're about to change. It shows which functions and modules directly depend on the files in scope, where coverage gaps make impact harder to verify, and which paths are off-limits without explicit approval (do-not-touch boundaries).

Blast radius is deterministic and read-only: it is computed from the canonical analysis report, not inferred or guessed, and computing it never mutates the repository or grants permission to edit.

Why it exists

Before editing a file, "what else depends on this?" is normally answered by grepping for imports and hoping nothing was missed — a process that scales badly and misses indirect dependents, clone cohorts, and low-coverage areas that make a regression hard to catch with tests. Blast radius exists to answer that question exhaustively and consistently, every time, instead of relying on a reviewer's memory of the codebase.

It is deliberately separate from permission: knowing the blast radius of a change tells you the risk, not whether you are allowed to proceed. That authorization question belongs to edit_allowed.

How it fits together

Blast radius is computed as part of declaring a controlled change: calling start_controlled_change returns it alongside the intent id and patch budget. It is not a standalone permission check and it is not the same thing as test coverage — a coverage gap in the blast radius means the risk is harder to verify, not that no risk exists.

Element What it tells you
Direct + transitive dependents Code that calls into your declared scope, directly or indirectly
Clone cohort members Other locations structurally similar to the files you're changing
Coverage gaps Parts of the risk boundary that tests do not currently exercise
Do-not-touch boundaries Hard boundary — requires separate explicit approval to touch
Review-only context Informational only — not a ban 
graph LR
    A["start_controlled_change"] --> B["Blast radius computed"]
    B --> C["Direct + transitive dependents"]
    B --> D["Clone cohort members"]
    B --> E["Do-not-touch boundaries"]
    B --> F["Review-only context"]

do_not_touch paths are a hard boundary, not a suggestion — touching one requires explicit, separate approval, never just editing around it. review_context paths are the opposite: informational only, not a ban.