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Reposted by Andrew Branch

Remco Haszing @remcohaszing.nl · 06/09/2026

I published a TypeScript content mapper for CSS modules. This gives you type-safety and definitions when importing CSS in TypeScript. github.com/remcohaszing...

On the right is a pane of CSS code. On the left is a pane of TypeScript code that imports the CSS as a module. The hover info of the imported CSS class shows the CSS block. There’s also an unknown class name, which has a red squiggly underline.

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Andrew Branch @andrewbran.ch · 04/09/2026

Is this a custom app to track the build?

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Reposted by Andrew Branch

Jiahan Chen @chenjiahan.bsky.social · 01/09/2026

Excited that TypeScript will finally support module types based on import attributes! Bundlers and frameworks can now provide accurate types for custom imports:

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Andrew Branch @andrewbran.ch · 31/08/2026

It was my bad for forgetting to relabel while thinking about what to do. But rest assured the bots don’t control us 🙃

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Reposted by Andrew Branch

NullVoxPopuli @nullvoxpopuli.com · 26/08/2026

Ember now has preliminary TS7 support ~ via the content-mappers feature that merged in TS last week Testers wanted! (requires TS Nightly)

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Reposted by Andrew Branch

Remco Haszing @remcohaszing.nl · 17/08/2026

My editor using mdx-content-mapper is now showing TypeScript info for frontmatter and code blocks.

An MDX file with two JavaScript code blocks. One is hovered and shows information about the code. The other highlights a type error.

An MDX file with YAML frontmatter data and a variable named frontmatter. Hover information for the frontmatter variable shows the TypeScript type of the frontmatter data.

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Andrew Branch @andrewbran.ch · 17/08/2026

APIs are available in nightlies and some tools have started building with them to get ready for 7.1. But there will be breaking changes, so if a particular tool is no longer in development, it will never work with the 7.x line.

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Andrew Branch @andrewbran.ch · 17/08/2026

FWIW, every announcement since at least April has said that 7.0 will not include the programmatic API that tools need. The blog posts have instructions for installing 6 and 7 side by side so you don’t have to temporarily downgrade. It’s not broken, it’s not included yet (which was the plan).

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Andrew Branch @andrewbran.ch · 16/08/2026

Yeah, that doesn’t seem like a great trade off to me… there’s also the reality that any big shift from TS 6 that doesn’t strictly need to happen just makes it harder for people to move, on top of the changes that do really need to happen.

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Andrew Branch @andrewbran.ch · 15/08/2026

That said, I don’t think I can accurately explain exactly how to attribute the 3x to 4x so I won’t try to hand wave too much. Anders did some videos and interviews after we announced that might get into the weeds better than I can.

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Andrew Branch @andrewbran.ch · 15/08/2026

Some of both—JS of course doesn’t give you direct control over the layout. We had some big efforts to monomorphize access in JS but doing it across every object was impossible. We were definitely careful with layout/design in Go (e.g. avoiding access through interfaces in hot paths).

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Andrew Branch @andrewbran.ch · 15/08/2026

This is what I love about open source! We all get better and smarter and faster together.

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Andrew Branch @andrewbran.ch · 15/08/2026

It varies, but at least in the early measurements it was typically 2.5x from parallelism and 4x from everything else.

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Andrew Branch @andrewbran.ch · 15/08/2026

Not yet. As for perf, it depends. The more separate requests, the more IPC overhead adds up. Wasm builds bring their own perf penalty to Go. I’ve seen tools get faster, stay the same, and get slower after moving to TS 7.

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Andrew Branch @andrewbran.ch · 15/08/2026

How would you envision that working?

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Andrew Branch @andrewbran.ch · 15/08/2026

I think 100% of what I showed actually shipped in 7.0. We haven’t talked about it a ton because we’re kind of at full capacity implementing things we know still need to get done, so I wanted to be a little strategic about the volume of feedback we get. Bit it’s time to start expanding a bit more.

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Andrew Branch @andrewbran.ch · 15/08/2026

Now is a good time to start building with the API and sending feedback my way on GitHub. What are you still missing to be able to move your API-using projects to TS 7?

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Andrew Branch @andrewbran.ch · 15/08/2026

What’s next? Content mappers, I hope! github.com/microsoft/ty...

A Vue file with TS intellisense working, and the same errors showing in the CLI with `tsgo --runExternalCode`

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Andrew Branch @andrewbran.ch · 15/08/2026

This LSP-connected API method is why everything goes through immutable snapshots. You can continue to work with immutable state for as long as you want, even if the user has moved files or continued typing.

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Andrew Branch @andrewbran.ch · 15/08/2026

This simple example is running in the extension host, but you can imagine passing this connection to your own LSP server, serving additional completions or hovers in TS files by combining its own logic with type checker queries.

The demo extension working, logging "add, subtract" in a math.ts file

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Andrew Branch @andrewbran.ch · 15/08/2026

Let's do something totally different. Here's a VS Code extension, which gets a sidecar API connection to the TypeScript LSP that was already running. All the same APIs are available, and now you can inspect the projects the user has open in their editor. Here we're logging the exports of .ts files.

A VS Code extension calling a cross-extension API to get a pipe to connect to the TS 7 LSP and construct an async API instance from it. A change handler gets the default TS project for the file and uses its program and checker to log the file's exports.

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Andrew Branch @andrewbran.ch · 15/08/2026

So far, almost all of this code could be mistaken for the old TS 6 API. But under the hood, a lot of care has to go into pretty silly things like making sure when you get the same Type or Symbol twice, they have reference equality. That doesn't come for free anymore.

two results of getSymbolAtLocation are strict equal to each other

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Andrew Branch @andrewbran.ch · 15/08/2026

Now for some transformation. The new AST is a hybrid of these "remote nodes" backed by binary data and normal JavaScript objects. The client can encode the result into the same binary format so the server can run it through the emitter, in this case. Here's a (dumb) codemod to fix our error.

A transforming visitor replacing a string literal "2" with a numeric literal 2 on the same file, then printing the transformed file to a string.

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Andrew Branch @andrewbran.ch · 15/08/2026

To demonstrate the laziness of file decoding, we can see that after recursively visiting one of the two statements in the file, 10 of the 20 nodes were actually materialized. (The timings here look slower than they should because the VFS is not yet production quality.)

Metrics showing 20 nodes were fetched and 10 were materialized, with 5ms of IPC transport overhead

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Andrew Branch @andrewbran.ch · 15/08/2026

Every node materializes into an instance of the same class, all reading the same underlying buffer. The TS types lie and give each node a specialized type. Here, we see `kind` reading its value from an offset computed by the node's index in the flattened AST and the kind field's offset.

Another debug view showing the getter for `kind`, reading a uint32 from the underlying buffer

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Andrew Branch @andrewbran.ch · 15/08/2026

But how exactly does that work? The tsgo process encodes the AST in a compact binary format and sends it all over. The client's SourceFile type wraps the Uint8Array and exposes getters for every property you could want to access. Children and other properties are lazily decoded on first access.

A debug view inspecting the RemoteSourceFile type at runtime, showing a DataView with an underlying ArrayBuffer.

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Andrew Branch @andrewbran.ch · 15/08/2026

Slightly more interesting: let's navigate a source file and use the type checker on some stuff. This found the return type 'void' from `console.log` and the return type 'number' from `add`.

Recursively visiting each child of the second statement of main.ts, getting the signature of call expressions, and logging the return type of those signatures. Output shows void (belonging to console.log) and number (belonging to add)

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Andrew Branch @andrewbran.ch · 15/08/2026

Let’s start with something basic like getting diagnostics. Not too much to say about this. Each API call like this is communicating over STDIO with the tsgo process. We'll see some details in a minute.

console.logging program.getSemanticDiagnostics, showing an assignability error as a JS object

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Andrew Branch @andrewbran.ch · 15/08/2026

The API comes in sync and async flavors. You import from "unstable" for now, but it's not going to change architecturally before 7.1. Breaks will be mostly targeted renames/moves. You access programs through obtaining immutable snapshots. There will be more ways coming soon. More on this later.

A TS file creating a sync API instance from "typescript/unstable/sync" with a virtual file system, and obtaining a program, checker, and emitter.

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Andrew Branch @andrewbran.ch · 15/08/2026

If you’re not stalking TypeScript PRs, you might be surprised how much you can do with the API in nightlies (and even in 7.0 stable), so here’s a tiny demo that I think hits some of the highlights. 🧵

A package.json in VS Code after npm installing typescript@next

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Andrew Branch @andrewbran.ch · 07/08/2026

A friend of mine was injured just last week at his workplace when an e-bike crashed through the building. Ah no wait it was a car

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Andrew Branch @andrewbran.ch · 07/08/2026

I think so but I’m not sure of the timeline, @jakebailey.dev might be able to confirm

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Andrew Branch @andrewbran.ch · 07/08/2026

They are not quite complete but they’re getting pretty close! Several projects (like ts-loader) have already started building against them. The feedback from those early adopters has been super valuable but I’m getting the sense a lot of folks don’t know it exists already!

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Andrew Branch @andrewbran.ch · 07/08/2026

Thanks for mentioning the APIs and arethetypeswrong! ❤️ I feel like I need to get the word out that the compiler APIs are available today in nightlies, and even in 7.0, they’re just under “typescript/unstable” to make it clear that we reserve the right to make breaking changes before 7.1.

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Reposted by Andrew Branch

John Reilly @johnnyreilly.com · 31/07/2026

I've been busy experimenting with the new emit APIs that TypeScript 7.1 will bring. ts-loader now has basic support in place - here's how we got there! johnnyreilly.com/migrating-ts...

johnnyreilly.com

Migrating ts-loader to TypeScript 7.1 with AI

How I used AI to migrate ts-loader to TypeScript 7.1.

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Reposted by Andrew Branch

David Sherret @dsherret.dev · 30/07/2026

ts-ast-viewer.com now supports TypeScript 7 along with nightly builds of the typescript-go repository. It's not selected by default, but available in the dropdown.

Dropdown menu showing a TypeScript 7.0.2 selection on ts-ast-viewer.com

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Reposted by Andrew Branch

John Reilly @johnnyreilly.com · 28/07/2026

If you discount project references (and there's no API support as yet I believe), then all bar around 6 tests of ts-loader are now passing using the 7.1 tsgo TypeScript API! Not quite there yet but significant progress github.com/TypeStrong/t...

github.com

Support TypeScript 7.1 API by Copilot · Pull Request #1704 · TypeStrong/ts-loader

This PR is an attempt at using the TypeScript 7.1+ API. This pares back the earlier tsgo integration attempt to the new API alone. Instead of carrying both implementations, experimentalNativeApi no...

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Andrew Branch @andrewbran.ch · 27/07/2026

Awesome! FYI, transpileModule is coming soon too

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Andrew Branch @andrewbran.ch · 25/07/2026

Probably not going to change that much, except for adding more stuff! There’s just no promise or stability until 7.1, but I don’t anticipate major changes.

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mary🐇 @mary.my.id · 25/07/2026

they coulda trained opus 5 to learn that typescript 7 is stable now because it simply refuses to believe oxlint with type checking enabled only takes 28ms to run

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Reposted by Andrew Branch

Pier Fumagalli @pier.fumagalli.org · 25/07/2026

Today’s Typescript 7 daily release finally includes my contribution to support “emit” via API! Right before the weekend, so I can waste it playing around with it 😛 Thanks @andrewbran.ch tor including it! npmx.dev/package-code...

npmx.dev

Code - typescript@7.1.0-dev.20260725.1 - npmx

Browse source code for typescript@7.1.0-dev.20260725.1

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Andrew Branch @andrewbran.ch · 25/07/2026

Thanks for working on it!

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Andrew Branch @andrewbran.ch · 15/07/2026

Yes! 🙌 This made my day!

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Andrew Branch @andrewbran.ch · 09/07/2026

The water is extra glassy today

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Andrew Branch @andrewbran.ch · 08/07/2026

I'm sure this was not meant to be personal, but it's hard not to feel a jolt of panic and defensiveness when the og-image of your sadness has my face in it 😅

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