Thanks for putting this together — the implementation is cleaner than I'd expect for a feature this size (additive IR variants, gated runtime cost, no panics in the Reflect surface, real DI simulation in the integration canary). Before merging I want to nail down two questions about what this actually unlocks for users.

1. Does a real NestJS app boot on this?

The canaries pass, but they're hand-rolled — resolveProvider in test_decorators_nest_integration_canary.ts is bespoke test code, not @nestjs/core itself. To prove this PR delivers the win it's pitched on, can you add one end-to-end smoke test that:

• Starts from npx @nestjs/cli new (or the minimal equivalent — a package.json with @nestjs/common @nestjs/core reflect-metadata and a hand-written AppModule/AppController/AppService)
• Compiles with perry (using compilePackages if needed)
• Listens on a port and serves GET / returning a string

If you can get that working, the DX value is concrete. If you hit walls, the walls are what we need to see — they'll tell us how much further work is needed before this is usable end-to-end. Either way the smoke test belongs in tests/release/packages/ so it doesn't regress.

2. Two silent-failure cases I'd like to convert to compile errors before merge:

(a) import "reflect-metadata" is currently lowered to Ok(()) in crates/perry-hir/src/lower.rs:1213 — the import is silently dropped and Perry's built-in shim runs instead. The shim covers the methods this PR implements, but it's a subset of the npm package's surface (class-validator and TypeORM call into corners of reflect-metadata that aren't shimmed). Users importing the npm package will think they have the full thing. Suggested fix: keep the suppression but emit a one-time [perry] note: reflect-metadata import shimmed by built-in subset diagnostic at compile time, listing the methods Perry actually implements. That way the user knows what they're getting.

(b) Class decorators that return a replacement class currently run the decorator for side-effects and discard the return value — test_decorators_replacement_unsupported.ts documents this but doesn't enforce it. Real-world decorators like @Memoize, @Throttle, GraphQL resolver wrappers all return wrapped classes; they'd compile and run incorrectly. Suggested fix: detect at lowering time that a class decorator's resolved type is a ClassDecorator returning non-void/undefined and emit a compile error. If type-level detection is too fiddly, a runtime check at decorator-application time that throws on non-undefined return is acceptable as a fallback — anything beats silent failure.

Once those two are in and the NestJS smoke test compiles + serves a route, I'm comfortable merging. Appreciate the work — the metadata pipeline itself is well-scoped.

Thanks for the structured review. Pushed the work as four commits + a follow-up docs regen on top of the original PR.

2a (reflect-metadata shim diagnostic) — done. c04df7ad. import "reflect-metadata" now emits a one-shot [perry] note: … to stderr at compile time listing the implemented surface (defineMetadata, getMetadata, getOwnMetadata, hasMetadata, hasOwnMetadata, getMetadataKeys, getOwnMetadataKeys, deleteMetadata, @Reflect.metadata(...)) and pointing at docs/src/language/decorators.md. Guarded by an AtomicBool so repeated imports across the dep graph don't spam.

2b (class decorator replacement returns) — done as runtime throw, your suggested fallback. Same commit. append_class_decorator_invocations in crates/perry-hir/src/lower.rs captures the decorator return into a temp and, when typeof ret === "function", throws TypeError: Class decorator @<name> on <Class> returned a replacement class …. I used typeof === "function" rather than !== undefined to work around an unrelated Perry quirk (function-expression implicit returns leave a numeric sentinel in the return slot, which made !== undefined false-positive on bare side-effect decorators like @Injectable). Class refs are typeof "function" in JS, so this catches the @memoize / @Throttle / GraphQL-wrapper pattern precisely. The test_decorators_replacement_unsupported canary flipped from "replacement ignored" (silent) to the TypeError header.

1 (NestJS smoke test) — fixture wired, three walls broken, fourth documented. fc020ebb.

tests/release/packages/nestjs-hello/ follows the hono-basic layout: package.json with @nestjs/common @nestjs/core @nestjs/platform-express reflect-metadata rxjs + compilePackages, entry.ts with @Module / @Controller / @Injectable / @Get + NestFactory.create(AppModule) + app.listen(port), fixture.sh that does npm install → perry compile → run in background → curl / → diff. Listens for real on a port, no bespoke resolveProvider.

Walls fixed in this PR:

• util.types not in the API manifest — added property("util", "types") plus a real types surface in node:util (isPromise/isAsyncFunction/isMap/isUint8Array/isProxy/etc., unknown shapes default to false).
• super.<prop> value-form lowering hit a hard lower_bail! — lowered to this.<prop> / this[expr]. Correct when the subclass doesn't override the property (covers rxjs's OperatorSubscriber this._next = onNext ? wrapper : super._next pattern). Strict parent-vtable lookup is the proper fix; left as a TODO with an inline comment.
• async_hooks.AsyncResource missing — added AsyncResource + AsyncLocalStorage (+ executionAsyncId, createHook) to a real node:async_hooks stub. No real async-context tracking, but the runInAsyncScope shape is enough for the NestJS code path.

4ce4e693 regenerates docs/api/perry.d.ts + docs/src/api/reference.md for the new manifest entries (caught by the api-docs-drift gate).

Wall 4 — open: cross-module method symbol mangling for re-exported classes. Compile + codegen succeed; link fails on _perry_method_node_modules_rxjs_src_index_ts__Subscription__unsubscribe etc. The class is defined in rxjs/src/internal/Subscription.ts but callers reference it via the rxjs/src/index.ts barrel and Perry uses the barrel's prefix instead of the defining module's. The fixture file WALLS.md describes it and the probable next walls (the same bug from @nestjs/platform-express's ExpressAdapter, then likely Logger / setImmediate edges).

Structurally I think Wall 4 wants its own focused PR — it's surgery on crates/perry/src/commands/compile.rs and possibly crates/perry-codegen/src/codegen.rs, unrelated to decorator metadata. Same for whichever walls show up after that. The fixture is wired to SKIP-with-reason while WALLS.md is present and flips to hard FAIL the moment WALLS.md is removed, so each follow-up PR can chip away with a clear regression net.

Decorator parity still 12/12. CI is re-running on 4ce4e693.