Cursor rule

1---
2description: "Analyze the blast radius of a proposed change before any code is written. Maps dependents, affected stories, and test coverage. Produces specs/IMPACT_LATEST.md. Use before plan-work on any non-trivial change, when touching a shared module, or when the user asks \"what does this break?\"."
3alwaysApply: false
4---
5 
6# Assess Impact
7 
8> **HARD GATE** — Run this skill before `plan-work` whenever a change touches an existing module, symbol, or file used by more than one caller. Skip only for net-new code with no existing dependents.
9 
10Find the blast radius of the proposed change before a single line is written.
11 
12## Modes
13 
14- Default: full impact analysis (dependents + affected stories + test coverage mapping)
15- --lightweight: Fast fan-in/fan-out only (<10s). Maps callers and imports without test coverage mapping. Used by build-epic step 2 as a pre-plan gate. Risk score > 7 triggers a mandatory grill-me session before proceeding.
16 
17## Process
18 
19### 1. Identify the target
20 
21Name the symbol, module, or file being changed. If the user hasn't specified, ask one question: "What exactly are you changing?"
22 
23### 2. Find dependents
24 
25```
26grep -rn "[symbol-name]" . --include="*.ts" | grep -v node_modules
27git log --oneline -10 -- [file-path]
28```
29 
30→ verify: `test -f specs/IMPACT_LATEST.md || test -d specs/bugs`
31 
32### 3. Map to release plan stories
33 
34Read `specs/release-plan.yaml + epic capsule directories` (if it exists). For each dependent found in Step 2, identify which story owns that module. List stories that will be affected by the change.
35 
36→ verify: `test -f specs/release-plan.yaml && grep -ci "stor" specs/release-plan.yaml`
37 
38### 4. List test coverage
39 
40Find tests that exercise the target:
41 
42```
43grep -rn "[symbol-name]" . --include="*.test.*" --include="*.spec.*"
44```
45 
46→ verify: `test -d specs/epics || test -d skills`
47 
48### 5. Classify risk
49 
50| Level | Condition |
51|-------|-----------|
52| Low   | ≤ 2 callers, all covered by tests |
53| Medium | 3–10 callers, partial test coverage |
54| High  | > 10 callers, or shared API/interface, or no tests |
55 
56### 6. Write specs/IMPACT_LATEST.md
57 
58```
59## Target
60[symbol or file being changed]
61 
62## Dependents ([count])
63- [file]: [caller or usage]
64 
65## Affected Stories
66- Story [X.Y]: [title]
67 
68## Test Coverage
69- [test file]: covers [scenario]
70- Gap: [untested behavior]
71 
72## Risk: Low / Medium / High
73[One-sentence rationale]
74 
75## Recommended action
76[Proceed / Add tests first / Discuss design]
77```
78 
79→ verify: `grep "Risk:" specs/IMPACT_LATEST.md`
80 
81Suggest `plan-work` once risk is understood and any test gaps are noted.
82 
83## Risk score gating
84 
85In `--lightweight` mode (used by build-epic step 2), assign a numeric risk score (1–10):
86- Fan-in (how many callers): 0–4 points
87- Fan-out (how many dependencies the module itself uses): 0–3 points  
88- Recent churn (git log --oneline -5 count): 0–3 points
89 
90**Risk score > 7**: Gate — require a `grill-me` session before proceeding to implementation. Document the grill-me result in the impact report at `specs/IMPACT-<epic>-<story>.md`.
91