# Dependency Upgrade & Migration Planner

> Upgrade frameworks and dependencies across major versions safely by reading the migration guide, running official codemods, fixing breakages in small batches, and verifying with the full test suite. Use when asked to upgrade, bump, or migrate a library, framework, runtime, or API version.

## Quick Reference
- **Framework**: Framework Agnostic
- **Language**: TypeScript / Polyglot
- **Styling & UI**: None / Irrelevant
- **Database / Persistence**: None / Irrelevant
- **Architectural Philosophy**: architect

## Core Architectural Invariants
- **Guard Clauses & Early Returns**: Exit early from functions to eliminate deeply nested if-else pyramids.
- **Schema-Driven Boundaries**: Validate all external data (API, forms, env) with Zod or Pydantic schemas; on failure, reject with a typed error and never pass unvalidated data onward.
- **Self-Documenting Naming**: Expressive function and variable names over verbose redundant comments.

## Operational Guardrails & Prohibited Patterns
- **Inspect Before Acting**: Always read and understand existing code and imports before suggesting changes.
- **Minimal Surgical Diffs**: Touch only lines relevant to prompt. Preserve existing comments and formatting.
- **Propose Verification Steps**: With every modification, specify concrete commands or tests to verify correctness.
- **Dependency Caution**: Never introduce new third-party libraries or packages without explicit approval.

## Mandatory Project Directives
- Follow the documented upgrade path; never skip intermediate major versions the migration guide says to pass through.
- Do not add or replace dependencies as part of an upgrade without approval.
- Never silence new type errors or deprecation warnings with casts, ignores, or suppressions; fix them or list them as follow-ups.
- One commit per package group, kept separate from feature work, so each can be reverted alone.
- Pin upgraded versions the way the project already does and commit the regenerated lockfile.

## Implementation Reference

### Preferred Patterns
```typescript
// Good: one coupled group per commit, verified before the next
// 1. npm install react@19 react-dom@19 @types/react@19 @types/react-dom@19
// 2. npx codemod@latest react/19/migration-recipe   (review the diff)
// 3. npm run typecheck && npm test && npm run build
// 4. git commit -m "build(deps): upgrade react 18.3 -> 19.0"
```

### Discouraged Anti-Patterns
```typescript
// Discouraged: every package at once, errors suppressed to get a green build
// npm install react@19 next@16 typescript@6 eslint@10
// added @ts-expect-error to 40 files
```

## Verification Commands & Workflows
1. Inventory: record current and target versions, read the official changelog and migration guide for every major version in between, and list each breaking change that applies here (search the codebase for every affected API).
2. Get a green baseline on the current versions (install, build, type-check, lint, test) and note pre-existing failures so they are not blamed on the upgrade.
3. Upgrade one package or one tightly coupled group at a time (for example a framework with its types and CLI), regenerating the lockfile with the project's package manager.
4. Run the official codemod when one exists, review its diff, then fix the remaining breakages guided by compiler errors and failing tests.
5. Verify with build, type-check, the full test suite, and a smoke run of the app, and list behaviour changes from the release notes that tests do not cover.

## Context Documents & Specs
- [System Architecture](ARCHITECTURE.md): Authoritative system design, data flows, and state machine invariants.
- [AI Multi-Agent Spec](AGENTS.md): Universal specification for autonomous coding agent operations.