Code Review Breaking Changes

Search for breaking changes on every surface another party depends on:

• Request and response contracts (HTTP, RPC, functions, webhooks). Shapes, required fields, status codes, error shapes, pagination, auth requirements, CORS, and any health payload a deploy asserts on. A tightened validator, a new required field, or a change to what create-or-update treats as the same record breaks callers that were passing yesterday and can duplicate or overwrite rows. An API spec (OpenAPI, GraphQL, protobuf) and the handler that serves it that disagree after the change on a field, whether it is required, or a status code.
• Database schema and policies. A migration that drops or renames a column, tightens a constraint, changes a row-level security policy, or bumps a schema version breaks rows already stored, services on the previous build, ORM mappings, and generated types. Check that it is additive or ships a backfill, has a rollback, and that mappings and generated types were regenerated. A versioned, run-once migration file already applied by a journaling tool (Flyway V__, DbUp, Liquibase changesets, Prisma, Supabase) and edited in place: the edit never runs where the file was applied, or the checksum check fails the deploy. Repeatable migrations are meant to rerun. A function, view, or type dropped and re-created loses its grants; report the grant a caller needs that the change does not restore.
• Data transformations and field mappings (import, export, migration, sync). A changed mapping, default, or key match rewrites records already processed on the next run; a changed type or null rule breaks downstream consumers of the target table. Say what happens to data processed under the old mapping.
• Runtime and gateway configuration for deployed functions and services. Handler entry point, runtime version, memory and timeout, environment variables, permissions, routes and stages, and event source mappings.
• Environment and configuration. A new required variable, a renamed key, a changed default, or a config file whose old shape no longer loads. Every deploy target, pipeline variable group, and CI workflow that supplies it must be updated in the same change.
• Pipelines and deploys. Workflow and pipeline inputs, secrets, service connections, agent pools and runner names, stage order, ports, and the rollback path.
• Shared packages. The public API of a shared library or client package, and its version.
• CLI. A removed or renamed command, flag, or exit code, or a stdout format a script parses.
• Stored user data. Settings files, local databases, caches, and on-disk formats a previous version wrote. The new version must read the old form or migrate it.
• Extension manifest and messaging. Permissions, host patterns, and message names between content, background, and page scripts.
• Logs and metrics. A log line, metric name, or dimension that an alarm or dashboard matches on.

Do not stop after finding one issue; analyze all possible ways breaking changes can happen.

Report

One finding per break, at the path:line that introduces it. Severity high when data is lost or a caller fails outright, medium when behavior changes but degrades gracefully, low when only a version or doc needs to follow. Say what it breaks, who depends on it, and whether the change ships a migration path: a backfill, a fallback, a versioned contract, or a rollback. If it ships none, say what one would be.