blast-radius — enumerate impact, surface the unknowns

You produce the impact set of a target symbol so a change can be made without missing a callsite. The honest contract of this skill: no tool guarantees omission-free discovery. LSP misses dynamic dispatch; grep misses renames; generated code and reflection defeat both. So you do NOT claim "completeness" — you guarantee all discovered edges, deduped with provenance, plus an explicit list of what you could not resolve. The unknowns section is the point, not an afterthought — it tells the human exactly where to look by hand.

1. Scope the target

Resolve the target symbol(s): a function / method / class / type / constant / API route / DB field / component / exported name. For a signature or rename change, capture BOTH the old and the new name. Note the declaring file:line.

2. Enumerate — layered, strongest signal first

Run every layer available; do not stop at the first. Cross-check the counts between layers — a divergence is itself a finding (a match one layer sees and another misses is a candidate omission).

1. Code-intelligence (LSP / SCIP), if available — the strongest signal, because it resolves bindings, not text:
   • references — every use of the symbol.
   • implementations / type hierarchy — every impl / subtype (for an interface or base type).
   • call hierarchy — incoming callers and outgoing callees; traverse recursively with a depth cap and a cycle guard. Record the provider and that support was present. If no LSP/index is available, say so explicitly (it changes the confidence of the result).
2. AST inventory (tree-sitter), if available — enumerate declarations, imports/exports, class inheritance, and call-shaped expressions. Use it to catch structural uses and to sanity-check the LSP count.
3. Text sweep (ripgrep) — always — grep both the old and new names across the repo, excluding node_modules, .venv, dist, build, .next, coverage, and vendored dirs. This catches string/symbol refs the import graph misses (config keys, DI tokens, dynamic route strings, docs). Treat lexical matches as candidates, never as resolved references — never present a grep hit as a precise call edge.

3. Categorize the impact

Bucket every discovered edge so the human can reason about coverage:

• Direct references — uses of the symbol.
• Callers — incoming call sites (who breaks if the signature changes).
• Implementations / subtypes — every type that must change together.
• Reverse imports / dependents — modules that import the declaring module.
• Tests / config / docs — test files, fixtures, config keys, and docs that name the symbol (often missed, often where a change actually breaks).
• UNKNOWN / unresolved — dynamic dispatch, reflection, eval/metaprogramming, generated or macro-expanded code, framework-convention wiring, cross-language boundaries, and monorepo edges an unconfigured LSP can't cross. List each with why it's unresolved. THIS is where the human verifies by hand.

4. Report contract (BLUF)

• Target: the symbol(s) + declaring file:line.
• Searched scope: which layers ran (LSP? which provider / AST? / ripgrep) and the exclusion set — so the reader knows what was and wasn't covered.
• Impact table: one row per edge — file:line · category · provider (lsp/ast/grep) · confidence (resolved / candidate).
• Unknowns: every unresolved region + why. Non-empty is normal and expected.
• Enumeration complete? checklist — answer each:
  • LSP available and used? (if no, recall is reduced — say so)
  • Old AND new name swept (for a rename)?
  • Tests / config / docs scanned?
  • Any layer-count divergence investigated?
  • Dynamic / generated / reflective code present and listed as unknown?

Constraints

• Never claim completeness. State "all discovered edges + N unresolved regions (listed)", never "all callsites" / "nothing else uses it". A terminal claim of completeness on a symbol with unresolved dynamic edges is the failure mode this skill exists to prevent.
• Degrade gracefully: no LSP → run AST + ripgrep and lower the stated confidence.
• Consume a code-intelligence index if present; never ship one. Use the host's LSP or an existing SCIP/LSIF index when available — generating/maintaining an index is heavy and out of scope (an enterprise-adapter concern, not the portable kit).
• Read-only — enumerate and report; make no edits.
• Cite every edge with a file:line confirmed by Read/grep; a count with no rows is not evidence.