Migrate to TypeScript Without Stalling
Almost every team that runs JavaScript wants to be on TypeScript, and almost none of them finish the migration. The reason is consistent: it's a large, low-glamour, all-or-nothing-feeling project that never wins a sprint against shipping features. So it starts, a few files get converted, and then it sits half-done for a year — which is arguably worse than not starting, because now the codebase is two languages at once.
Codowave is built for exactly this kind of grinding, file-by-file work. It converts modules to TypeScript, adds real types, fixes the errors that surface, runs your tests, and opens the work as reviewable PRs in stages — so the migration actually progresses while your team builds features.
Start your 5-day trialWhy Migrations Stall
A TypeScript migration isn't one task; it's hundreds of small ones that nobody wants to own:
- Renaming a file and adding types to its exports.
- Fixing the type errors that ripple into every file that imports it.
- Replacing
anyplaceholders someone added to make the build pass. - Updating tests and mocks to the new types.
- Doing all of that without changing runtime behavior.
Each file is an hour or two of unrewarding work. The project needs a steady drip of that work over weeks, which is precisely the kind of sustained, boring effort a human team deprioritizes and an autonomous agent does not.
How Codowave Runs the Migration
Codowave decomposes the migration into bounded units and works through them, so you get a stream of reviewable PRs rather than one impossible mega-diff.
- Scope the migration. Point Codowave at a directory or package, or file issues per module — "convert
src/services/*to TypeScript." - Auto-decompose. The Planner breaks the scope into a sequence of file- or module-level changes ordered so dependencies convert before their consumers.
- Convert and type. The Coder renames files, adds genuine types (not blanket
any), and updates imports against your existing conventions. - Fix the fallout. It resolves the type errors the conversion surfaces in dependent files, in the same isolated container.
- Verify and open a PR. The Tester runs your suite to confirm behavior is unchanged; each stage opens as its own reviewable PR with test output attached.
Because each PR is one bounded slice, your team can review and merge migration work in the gaps between feature work instead of blocking a sprint for it.
What to Expect Per File Type
| Source | Migration quality |
|---|---|
| Utility / pure functions | Strong — clean, fully typed conversions |
| Service / data modules | Strong — types inferred from usage and shape |
| Express/Nest route handlers | Strong — request/response types added |
| React components | Strong — prop and state types added |
| Loosely typed config objects | Moderate — may need a human to confirm intent |
| Dynamic, reflection-heavy code | Use with supervision — types reviewed by a human |
| Untested modules | Moderate — pair with coverage work to verify behavior |
For dynamic code and anywhere real types are genuinely ambiguous, Codowave is conservative and surfaces the decision rather than guessing a type that compiles but lies.
Honest Types, Not any
The failure mode of a lazy migration is any everywhere — the build goes green, the project reports done, and you've gained nothing. Codowave's Reviewer agent checks for exactly that: it flags blanket any, missing return types, and types that don't match observed usage. The goal is a migration that gives you the type safety you wanted, not one that renames files and calls it finished.
Pattern memory helps here too. After roughly ten merged PRs, Codowave has learned how your team writes types — interface versus type, how you model errors, your shared generics — so later conversions match the style of the TypeScript you already have.
Safe to Run Over Weeks
A migration runs for a long time, so the controls that keep it bounded matter.
- Watch-only mode. Every conversion PR comes to you for review until you decide to trust auto-merge for the simplest file types.
- Cost ceiling per run. A hard dollar cap per agent run on your own Anthropic Claude key keeps a long migration's spend predictable.
- Tests are the gate. A conversion isn't done until your suite passes, which is what catches a type change that accidentally altered behavior.
Get Started
- Sign up at codowave.com/signup — 3 issues free, no card required.
- Connect your repo and scope Codowave to one directory or package to start.
- Let it convert a few modules and review the typed PRs.
- Enable auto-merge for the simplest file types once the types look right.
Plans start at $20/mo — see pricing. Pair this with raising test coverage to verify behavior as you go.
Start your 5-day trial