1 hour
How to Run Code Migrations with Eigent
Migrate legacy stacks in controlled checkpoints — map the old system to the new one, land the move in milestones, and validate parity before each transition.
What you need
- Eigent desktop app
- Codebase access (local or connected repo)
- Test suite, lint, and type-check tools
Best for
- Legacy-to-modern stack moves where frameworks, runtimes, or platform conventions need to change
- Teams that need compatibility layers, phased transitions, and explicit validation at each checkpoint
- Engineers managing an incremental strangler-fig or branch-by-abstraction migration
Starter Prompt
Migrate this codebase from [legacy stack or system] to [target stack or system]. Requirements: - Start by inventorying the legacy assumptions: routing, data models, auth, configuration, build tooling, tests, deployment, and external contracts. - Map the old stack to the new one and call out anything that has no direct equivalent. - Propose an incremental migration plan with compatibility layers or checkpoints instead of one big rewrite. - Keep behavior unchanged unless the migration explicitly requires a user-visible change. - Work in milestones and run lint, type-check, and focused tests after each milestone. - Keep rollback or fallback options visible until the transition is complete. - If validation fails, fix it before continuing. Start by mapping the migration surface and proposing the checkpoint plan.
How it works
- Inventory the legacy assumptions — routing, data models, auth, configuration, build tooling, tests, deployment, and external contracts.
- Map the old stack to the new one and call out anything with no direct equivalent.
- Propose an incremental migration plan with compatibility layers or checkpoints instead of one big rewrite.
- Keep behavior unchanged unless the migration explicitly requires a user-visible change.
- After each milestone, run lint, type-check, and focused tests to prove parity before continuing.
- Keep rollback or fallback options visible until the transition is complete.
More prompts to try
- What in this codebase has no direct equivalent in the target stack? How should we handle each gap?
- Propose a compatibility layer that lets old and new code coexist during the transition.
- After this milestone, what is the smallest test or check that proves parity with the legacy path?
- What are the rollback steps if the migration at this checkpoint fails in production?
How to use
Open Eigent with your codebase connected and describe your source and target stacks. Start with the migration surface inventory — this gives you a complete picture of what needs to move before any code changes. Work milestone by milestone and validate after each one. Ask Eigent to create an ExecPlan document to track decisions, deferred items, and validation results across sessions if the migration spans multiple days.
Expected output
A migration surface inventory, a checkpoint-based migration plan, implementation diffs for each milestone, and a validation summary confirming parity after each step. Rollback options are noted at each transition point.
Limitations
- Complex data model changes may require manual schema migration scripts that Eigent drafts but you must review.
- External contract changes need coordination outside of the migration itself.
- Large rewrites are best broken into many small milestones — avoid batching more than one layer of the stack per milestone.
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