# Skewcheck: ✅ SAFE — no supported incompatibility detected

> **Question:** does the previous application version still work against the proposed database schema?

No supported incompatibility was detected under the conditions tested. This is not a universal safety guarantee.

| | |
|---|---|
| Project | fixture/A-safe-additive |
| Execution | `example-A-safe-additive` |
| Baseline (old app) | `shop-v1` |
| Candidate | `A-safe-additive` |
| PostgreSQL | 16.15 (Debian 16.15-1.pgdg12+2) |
| Proposed migration(s) | `002_loyalty.sql` |
| Gate | non-blocking (exit 0) |
| Experiment complete | yes |

## Recommended next action
Proceed with normal review. Keep the old application's tests meaningful; SAFE only covers what they exercise.

## Schema changes (catalog diff)
| Change | Risk | Exercised by old app | Tests |
|---|---|---|---|
| Relation audit_log added | inert | not required | — |
| Column customers.loyalty_tier added (text) | inert | not required | `test/customers.test.js`, `test/orders.test.js` |
| Index orders_created_at_idx added on orders | inert | not required | `test/orders.test.js` |

**Coverage:** All 3 schema change(s) are additive and cannot affect statements the old application issues; no coverage is required.

## Runs
| Run | Migrations | Tests (pass/fail/other) | DB errors | Statements |
|---|---|---|---|---|
| control (old app × baseline schema) | 1/1 applied | 2/0/0 | 0 | 7 |
| candidate #1 (old app × proposed schema) | 2/2 applied | 2/0/0 | 0 | 7 |
| candidate #2 (old app × proposed schema) | 2/2 applied | 2/0/0 | 0 | 7 |

## Skipped checks
- Current application × proposed schema (no current app configured).
- Performance / lock-time analysis (out of scope).

## Limitations
- Skewcheck only observes code paths that the old application's tests execute; untested paths are reported as coverage gaps, not as safe.
- Coverage is identifier-level: a statement "touches" a changed object when it names the table (and column, or uses *). It is not a SQL parser.
- Correlation between an error and a schema change uses a fixed set of deterministic rules (R1–R6). Anything else is reported as ADVISORY, never UNSAFE.
- Performance, locking and migration runtime on production-sized data are not evaluated.
- Test files of one run share a database and run sequentially; ordering effects are identical across runs but are not isolated.
- Data-only migration effects are detected only when a test asserts on the affected data.

<sub>skewcheck 0.1.0 · report schema v1 · 2026-10-24T18:29:54.438Z</sub>