predict

# Predict Command $ARGUMENTS Triggers the Predictive Analyst to assess the impact and regression risk of proposed changes. ## Usage ```bash /predict [path_or_diff] # /predict src/auth : analyze all files under src/auth # /predict --diff : analyze uncommitted changes (git diff) # /predict src/api/routes.ts : analyze a single file ``` ## Protocol ### 1. Scope: Identify Target Files - If path provided: collect all files under that path - If `--diff`: run `git diff --name-only` to get changed files - List each file with its last-modified date and line count ### 2. Trace: Build Dependency Graph For each target file, find dependents: ```bash # Find files that import/require the target grep -rl "import.*from.*[target]" --include="*.ts" --include="*.py" --include="*.js" . grep -rl "require.*[target]" --include="*.js" --include="*.ts" . ``` Build a graph: `changed file, direct dependents, transitive dependents (1 level)` ### 3. Assess: Calculate Risk Score Score each changed file on a 1 to 5 scale: | Factor | Weight | Scoring | |--------|--------|---------| | Dependent count | 30% | 0 deps = 1, 1 to 3 = 2, 4 to 10 = 3, 11 to 20 = 4, 21+ = 5 | | Test coverage | 30% | Has dedicated test = 1, partial = 3, none = 5 | | Change surface | 20% | < 10 lines = 1, 10 to 50 = 2, 50 to 200 = 3, 200+ = 5 | | Shared/core file | 20% | Leaf = 1, mid-layer = 3, core/shared = 5 | **Overall risk** = weighted average rounded to nearest integer. ### 4. Report: Generate Impact Prediction Output a markdown report: ```markdown ## Impact Prediction: [scope] | File | Risk | Dependents | Test Coverage | Notes | |------|------|------------|---------------|-------| | src/auth/login.ts | 4/5 | 12 files | partial | Core auth flow | ### High-Risk Changes (score >= 4) - [file]: [why it's high risk and what to watch] ### Recommended Actions - [ ] Add tests for [untested file] - [ ] Review [high-dependent file] with extra scrutiny - [ ] Run integration tests covering [affected area] ``` ## Rules - **MUST** base risk scores on measurable signals (dependent count, coverage, diff size) — not vibes or adjective scales - **MUST** name at least one specific action per high-risk file — "review carefully" is not an action - **NEVER** predict regressions beyond what the signals justify. A single file with 20 dependents is a signal; a generic "this might break things" is noise. - **NEVER** skip the test-coverage factor — a high-dependent file with 100% coverage is lower risk than a low-dependent file with none - **CRITICAL**: the report ranks files by weighted risk score, not alphabetically. Readers will stop after the first 5 entries. - **MANDATORY**: state the confidence level explicitly. Predictions from a 5-line diff are HIGH confidence; predictions from 500-line refactors are LOW. ## Gotchas - `grep -rl "import.*from.*[target]"` is easily fooled by comments and string literals. Use the language's real AST tools (`ts-morph`, `ast-grep`, `pyflakes`) for accurate dependency graphs on anything beyond trivial diffs. - Dynamic imports (`importlib.import_module`, `require(variable)`, JavaScript `await import()`) are invisible to grep. Flag explicitly when the target uses them. - Test coverage reported by CI may exclude generated code, migrations, and `__init__.py`. "Has dedicated test = score 1" assumes a real assertion exists — check the test file rather than just the path match. - A 5-line diff in a "core" file is often more dangerous than a 500-line diff in a leaf file. The `change_surface` weight alone is misleading; combine with `shared/core` weight for meaningful signals. - Predictions about regressions are calibrated against the current test suite, not unknown production behaviors. A "low-risk" verdict means "tests likely pass", not "users will not notice". ## When NOT to Use - For **executing** a change after prediction — use `/fix`, `/refactor`, or the relevant skill - For PR review of logic quality — use `/review` - For CI pipeline risk analysis — use `/ci-cd-patterns` - For code quality metrics (complexity, duplication) — use `/analyze` - For a brand-new codebase with no change history — this skill needs dependents to measure; use `/explore` first