1.13.0

TypeSpec 1.13.0 introduces project-level configuration capabilities, expands compiler and OpenAPI authoring features, and includes a broad set of compiler, OpenAPI, and IDE fixes.

Deprecations

@typespec/compiler

Deprecated deepClone utility in favor of structuredClone. All internal usages have been replaced with the native structuredClone API.

Features

@typespec/compiler

ApplyCodeFixExpect.toEqual now accepts Record<string, string> to assert on multiple files after a code fix is applied. This enables testing code fixes that write to a different file (e.g., adding augment decorators to a client.tsp).

await ruleTester
  .expect({
    "main.tsp": `import "./client.tsp";\nmodel Foo { name: string; }`,
    "client.tsp": ``,
  })
  .applyCodeFix("add-client-override")
  .toEqual({
    "client.tsp": `@@override(Foo.name, "clientName");\n`,
  });

Add kind: project and entrypoint support to tspconfig.yaml for defining project boundaries and entrypoint resolution. See Project Configuration for more details.
tspconfig.yaml
```
kind: project
entrypoint: src/service.tsp
emit:
  - "@typespec/openapi3"
```
Added support for accessing late-bound members on models that use template spreads or is bases.

Previously, accessing a member that was introduced via a template instantiation would fail with an invalid-ref error:
```
model Template<T> {
  ...T;
}
model User
  is Template<{
    name: string;
  }>;

alias UserName = User.name; // ❌ previously: "Model doesn't have member name"
```
Now, the compiler will force-evaluate the container type when a member lookup fails on a model with unknown members (from template spreads or is), making late-bound members accessible:
```
model Template<T> {
  ...T;
}
model User
  is Template<{
    name: string;
  }>;

alias UserName = User.name; // ✅ now resolves correctly
```
This also works with:
- Forward references to the template definition
- Spread-based patterns (model A { ...Template<{x: int32}> })
- Members added by augment decorators
- Circular references between models with late-bound members
The internal modifier is no longer experimental. Using internal will no longer emit an experimental-feature warning, and #suppress "experimental-feature" directives are no longer needed.
Add project-scoped compiler feature flags to tspconfig.yaml. Compiler feature definitions are tracked internally with descriptions and can be listed with tsp info features.
tspconfig.yaml
```
kind: project
features:
  - function-declarations
```
Enabled resolution of member properties and metaproperties through template parameters based on constraints.
```
model Resource {
  id: string;
}

model Read<R extends Resource> {
  id: R.id;
}
```

@typespec/openapi

Add summary and kind fields to @tagMetadata decorator.

For OpenAPI 3.2, these fields are emitted as native tag object fields. For OpenAPI 3.0/3.1, they are emitted as x-oai-summary and x-oai-kind extensions. The OpenAPI converter also supports importing x-oai-summary, x-oai-kind (from 3.0/3.1) and native summary, kind (from 3.2) back to TypeSpec.
```
@tagMetadata("foo", #{ summary: "all operations that allow doing Foo", kind: "FooGroup" })
```

Add array form for @tagMetadata decorator to allow explicit control of tag declaration order.

@service
@tagMetadata(#[
  #{ name: "First Tag", description: "First tag description" },
  #{ name: "Second Tag", description: "Second tag description" }
])
namespace PetStore {

}

Using @tagMetadata(#[...]) and @tagMetadata("name", #{...}) on the same namespace is a diagnostic error.

Added a warning diagnostic when @defaultResponse is used on a model that already has a @statusCode property or is marked with @error.

@typespec/openapi3

@typespec/openapi3 includes the same @tagMetadata enhancements listed above for @typespec/openapi: support for summary/kind metadata and array-form tag declarations with validation for mixed usage.

Bug Fixes

@typespec/compiler

Fix spurious circular-base-type diagnostics after invalid ‘model is’ declarations.
Fixed the compiler to correctly detect circular model spread chains while preserving support for recursive model-expression aliases.
Fix wrongly detected circular reference with alias and model properties
Completion in the middle of an identifier now replaces the full token instead of inserting and leaving trailing characters
Language server fatal errors now write pending logs and the fatal stack trace directly to stderr so crash details remain visible.
Report an error when a function is declared in the $functions map in a JS file but has no corresponding extern fn declaration in TypeSpec. Previously this would silently have no effect.
[Language Server] Wrapped LSP server handlers with wrapUnhandledError to preserve server-side stack traces in error messages forwarded to the client. Previously, the JSON-RPC layer discarded the original stack trace, making unhandled errors in telemetry opaque.
Validate function rest arguments and report function call argument count diagnostics at call sites.

@typespec/openapi

Reject duplicate tag names in @tagMetadata array form.
Fix tagMetadata extension diagnostic targets

@typespec/openapi3

Mark models as @error when imported from 4xx/5xx response body schema references.
Fix import of deprecated: true on OpenAPI3 operations to generate #deprecated "deprecated" directive in converted TypeSpec output.
Fix custom auth scheme models leaking into components.schemas when declared inside the service namespace. They are now emitted only under components.securitySchemes as expected.
Propagate @JsonSchema.uniqueItems to query, path and header parameter schemas. The decorator was only applied to body model property schemas; for HTTP parameter schemas (which go through applyIntrinsicDecorators) it was silently dropped, so arrays declared on operation parameters never emitted uniqueItems: true even when the decorator was present.
```
op listUsers(
  @query
  @JsonSchema.uniqueItems
  $select?: ("id" | "displayName")[],
): User[];
```

typespec-vscode

Improved telemetry instrumentation for install-global-compiler-cli, preview-openapi3, start-server, and server-path-changed events by adding missing lastStep tracking and error detail logging. Added actionable error message when compiler is found but neither node nor tsp is available on PATH, guiding users to fix common nvm/fnm/volta configuration issues.