[cramforce]

Stacked on #1537 (opt/require-decl-storage); review that first.

Summary

In JavaScript, require("events") is the EventEmitter class, and bundled npm code uses it as a value. A small semaphore does this in its bundled chunk:

var EventEmitter = require("events"), ReleaseEmitter;
ReleaseEmitter = EventEmitter;
// later, in the constructor:
this.releaseEmitter = new ReleaseEmitter();
this.releaseEmitter.on("release", (token) => { /* ... */ });

The assignment was refused with SC1090 ("a runtime-provided class value ('EventEmitter') as an untyped value"), and class Channel extends require("events") {} failed on the require call as a value.

#1512 gave JavaScript an untyped EventEmitter constructor (scr_dyn_builtin_class.c) for constructor functions, and already used it for a destructured EventEmitter binding or events.EventEmitter. This change uses the same constructor wherever the class turns untyped:

• Class values. The events module binding (const EventEmitter = require("events")) and a direct reference to EventEmitter or a stream class become that constructor when they flow into an untyped slot. new through it builds an emitter object with Node's listener API, as new on a constructor function inheriting from it does. Only the class itself converts: a slot of the class's type can hold a program subclass, so such slots keep the refusal.
• Identity and instanceof. untyped === EventEmitter compares identity with that constructor. untyped instanceof EventEmitter now also recognizes a boxed compiled emitter, an instance of a program class extending EventEmitter; the prototype test alone answered false for those. The same applies through an untyped binding the checker narrows to the class.
• extends require("events"). The base is the runtime emitter, as through a require binding.
• Typed arrays of the class. [EventEmitter] stored as a typed array of the class is refused with SC1090. Before, the destructured binding already produced the untyped constructor there, and the array then failed its class check at run time with a TypeError.

The stream classes follow the same path where they turn untyped; constructing over them keeps #1512's run-time SC2020 until #1533 lands. require("stream") itself is unchanged.

Evidence

• 6571-events-module-class-value.cjs: the events module binding stored, aliased, constructed through and compared; SC1090 on main.
• 6572-extends-require-events.cjs: class extends require("events") used as a value; failed on main.
• 6573-semaphore-release-emitter.cjs: a semaphore whose constructor builds its release emitter through an aliased require binding and listens and emits on it; SC1090 on main.
• npm-static case 2595-bundled-chunk-emitter: a minified esbuild __commonJS chunk with the mixed var statement, a sibling chunk require, a class extending the binding and an alias; fails on main.
• Node and native agree in both lanes (plain and sanitized, including the RC audit and LeakSanitizer). The broad emitter/class/inherit/cjs/stream/require lane shows only failures that also fail on unchanged main in the Sandbox. Diagnostics, npm and npm-static suites pass apart from a known environment case.
• Zero-cost gate (both commits against main): 3429 programs identical, 2 intended differences: 6453 and 6454 test untyped instanceof EventEmitter, which now also checks for a boxed compiled emitter. Bench geomean +0.13%, self-hosted compiler −0.26%, both within tolerance.
• Lint, format and test:ts7 --baselines-only are clean; the self-hosting IR build has no diagnostics.

Not covered

• A typed on followed by an untyped emit on the same native emitter aborts at run time (pre-existing, also in TypeScript); it is being fixed separately.
• Untyped listenerCount, eventNames and similar on a boxed compiled emitter are not routed yet.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated
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When an EventEmitter instanceof right-hand expression mutates the left-hand binding, the new helper reads the binding after that mutation and returns the wrong result.