From 3be6c59074600ed979fe30593a287caead4db243 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ralph=20K=C3=BCpper?= <ralph.kuepper@skelpo.com>
Date: Sun, 17 May 2026 10:32:04 +0200
Subject: [PATCH] =?UTF-8?q?fix(codegen):=20#894=20=E2=80=94=20class-expres?=
 =?UTF-8?q?sion=20static=20[Symbol]=20sees=20populated=20module=20lets?=
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Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Effect's `Schema.ts` crashed during module init with `TypeError: Cannot
read properties of undefined (reading '_tag')` because
`init_static_fields` ran the `js_class_register_static_symbol(class_id,
key, value)` emission BEFORE `stmt::lower_stmts` initialised the
module-level lets that the key/value referenced. The registration
recorded zeros — `isSchema(C)` returned false on every class returned
from effect's `make()` factory, `dual`'s predicate failed, and the
curried path eventually fed `undefined` back into a `make()` call.

Two-part fix:

1. Split `init_static_fields` into `_early` (Error-registry +
   well-known symbol hooks — no user-value reads) and `_late`
   (per-class static-field stores + computed-Symbol-key registration +
   static blocks). The new `_late` runs after `stmt::lower_stmts`, so
   module globals are populated when the registration emits.

2. For class expressions returned from factory functions (the effect
   pattern), HIR lowering now sequences a new
   `Expr::RegisterClassStaticSymbol` in front of the `Expr::ClassRef`
   for each computed-Symbol-key static field. Each factory invocation
   re-emits the registration with current free-variable values — `class
   { static [k] = v }` evaluates k/v at definition time per spec.

Followup gap: static methods with a synthesized `…arguments` rest param
emitted unbundled call-site args, so `arguments.length` inside `static
pipe()` read garbage. Track static methods in `method_has_rest` /
`method_param_counts` and bundle trailing args at the
`Expr::StaticMethodCall` codegen.

Regression test: `test_issue_effect_tag_undefined.ts` covers the
standalone shape; byte-for-byte parity with `node
--experimental-strip-types`.

Known follow-ups for the full effect smoke (not addressed here):
- `arguments.length` reads 0 in FnExpr-returned-from-function whenever
  fixed params consume the user-passed args before the synthetic rest
  captures them. Blocks effect's `dual` predicate.
- Dynamic property access on a factory-returned class can't reach
  static methods. Blocks `Literal(tag).pipe(...)`.
---
 CHANGELOG.md                                  |  37 +++
 CLAUDE.md                                     |   6 +-
 Cargo.lock                                    | 230 +++++++++---------
 Cargo.toml                                    |   2 +-
 crates/perry-codegen/src/codegen.rs           |  74 +++++-
 crates/perry-codegen/src/collectors.rs        |  17 ++
 crates/perry-codegen/src/expr.rs              |  73 ++++++
 crates/perry-hir/src/ir.rs                    |  16 ++
 crates/perry-hir/src/lower.rs                 |  49 +++-
 crates/perry-hir/src/stable_hash.rs           |  10 +
 crates/perry-hir/src/walker.rs                |  16 ++
 crates/perry-transform/src/inline.rs          |  23 ++
 test-files/test_issue_effect_tag_undefined.ts |  85 +++++++
 13 files changed, 505 insertions(+), 133 deletions(-)
 create mode 100644 test-files/test_issue_effect_tag_undefined.ts

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6257fdf902..3c847a1b36 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,43 @@
 
 Detailed changelog for Perry. See CLAUDE.md for concise summaries.
 
+## v0.5.940 — fix(codegen): #894 — class-expression `static [Symbol]` registration sees populated module lets
+
+**Symptom.** `import { Effect } from "effect"; console.log(typeof Effect.succeed)` aborted during Effect's Schema.ts module init with `TypeError: Cannot read properties of undefined (reading '_tag')`, before any user code ran. The crash chained back to a `make()` factory invocation receiving `undefined` as `ast`, which itself stemmed from `isSchema(C) = hasProperty(C, TypeId) && isObject(C[TypeId])` returning false on a class returned from the factory — so `dual()`'s predicate failed, the curried path returned a function instead of the schema, and downstream `.annotations({…})` / `class extends transform(…)` chains corrupted the AST eventually fed back into `make`.
+
+**Root cause.** Two timing/scope bugs combined for the failure on the symbol side:
+
+1. **Static-field init ran before user init.** `init_static_fields` emitted the per-class `js_class_register_static_symbol(class_id, key, value)` call at the top of each module's `__init`, BEFORE `stmt::lower_stmts(&hir.init)` populated the module-level lets the key/value referenced. The key expression (`Symbol.for("…")`) and value expression (`variance = {…}`) both lowered to `LocalGet(N)` of top-level `Stmt::Let` ids whose global slots were still zero. Registration recorded `(class_id, 0, 0)` — never matched against the live `TypeId` at lookup time. Effect's `function make(ast) { return class { static [TypeId] = variance } }` hit this on every `make()` invocation: the inner anonymous class is HIR-hoisted to module-level, so its symbol-keyed field init shared the same single-shot module-init emission as a regular top-level class.
+
+2. **No per-invocation re-emission for class expressions.** Even after the module's let initializers ran, every subsequent `make(other_ast)` call still saw the stale, pre-init registration — there was no codegen-side hook to re-register on each factory entry. JS spec semantics: `class C { static [k] = v }` evaluates `k` and `v` at CLASS-DEFINITION time, which for a class expression is every time the surrounding scope runs. Perry needed to mirror that.
+
+**Fix.**
+
+* Split `init_static_fields` into `init_static_fields_early` (Error-extending class registry + well-known Symbol method hooks — neither depends on user-let values) and `init_static_fields_late` (per-class static-field stores + computed-Symbol-key registration + static blocks). The two call sites in `compile_module_entry` / non-entry-module compile path now sandwich `stmt::lower_stmts` between them, so the late phase reads populated module globals.
+
+* Added a new `Expr::RegisterClassStaticSymbol { class_name, key_expr, value_expr }` HIR variant and sequenced one in front of every `Expr::ClassRef` returned from `ast::Expr::Class` lowering (one per computed-Symbol-key static field on the class expression). Each factory invocation now re-emits `js_class_register_static_symbol` against the same `class_id` with current free-variable values — the registry's `insert` overwrites the prior entry, so subsequent `C[TypeId]` reads see the fresh registration.
+
+* Followup gap fix: static methods with the synthetic `…arguments` rest param (`static pipe() { return pipeArguments(this, arguments) }` — Effect's `make()`'s returned class) emitted unbundled call-site args. Added `static_methods` to the `method_has_rest` / `method_param_counts` collection and taught `Expr::StaticMethodCall` codegen to bundle trailing args into a `js_array_alloc` + `js_array_push_f64` chain when the called static method ends in a rest param.
+
+**Files.**
+
+* `crates/perry-codegen/src/codegen.rs` — split `init_static_fields` → `_early` + `_late`, updated both call sites; track static-method rest info in `method_has_rest` / `method_param_counts`.
+* `crates/perry-codegen/src/expr.rs` — handle new `Expr::RegisterClassStaticSymbol` (emits `js_class_register_static_symbol`); bundle trailing args in `Expr::StaticMethodCall` when the target has a rest param.
+* `crates/perry-codegen/src/collectors.rs` — `collect_ref_ids_in_expr` recurses into `RegisterClassStaticSymbol` (and `RegisterClassParentDynamic`) children so the surrounding function's `referenced_from_fn` pre-scan includes the lets they reference, which `compile_module_entry`'s `module_globals` build then promotes to module-global storage.
+* `crates/perry-hir/src/ir.rs` — new `Expr::RegisterClassStaticSymbol` variant.
+* `crates/perry-hir/src/lower.rs` — `ast::Expr::Class` lowering collects each computed-Symbol-key static field's `(key_expr, value_expr)` and prepends `Expr::RegisterClassStaticSymbol` to the `Sequence` before the `ClassRef`.
+* `crates/perry-hir/src/walker.rs`, `crates/perry-hir/src/stable_hash.rs` — new variant in both walkers + hasher.
+* `crates/perry-transform/src/inline.rs` — `rewrite_call_init` recurses into the new variant; `body_references_class_in_set` includes it in the class-name match arm.
+* `test-files/test_issue_effect_tag_undefined.ts` — standalone repro mirroring Effect's `make()` factory shape, validated byte-for-byte against `node --experimental-strip-types`.
+
+**Validation.** `test_issue_effect_tag_undefined.ts` prints the expected `isSchemaLike(A): true / isSchemaLike(B): true` after the fix (returned `undefined` / `false` pre-fix). Standalone repros covering the direct-vs-returned-class and `function returns class with static [Sym] = variance` shapes also pass.
+
+**Known follow-ups (not addressed here).** The full Effect smoke (`typeof Effect.succeed`) is still blocked downstream on two separate perry gaps surfaced during this investigation:
+
+* `arguments.length` reads 0 inside a function expression returned from another function whenever the FnExpr has FIXED parameters before the synthesized `…arguments` rest param — perry's call-site bundling only captures TRAILING args after the fixed params, so `function(a, b) { arguments.length }` called with `f(1, 2)` sees `arguments.length === 0`. Effect's `dual(arity, body)` uses `arguments.length` to discriminate data-first vs data-last, so the dispatch always falls to the curried path. Proper fix is to make the synthesized rest param capture ALL passed args (not just trailing) when the body reads `arguments`.
+
+* Dynamic property access on a class returned from a factory (`make().pipe`) reads undefined for static methods — `class_has_own_method` consults the instance vtable, not the static-method registry. Effect's `Literal(tag).pipe(propertySignature, …)` hits exactly this when `tag` lifts a literal schema and then chains. Proper fix is to add a static-method side table keyed by class_id and consult it from the class-ref property-get path in the runtime.
+
 ## v0.5.938 — fix(codegen+runtime): #894 — `const { EventEmitter } = require('node:events')` no longer throws `Cannot read properties of undefined (reading 'prototype')` (pino smoke test). **Symptom.** The pino smoke test under `perry.compilePackages: ["pino"]` (`mkdir /tmp/perry-pino-x && cd /tmp/perry-pino-x && echo '{"perry":{"compilePackages":["pino"]}}' > package.json; npm install pino; echo 'import pino from "pino";' > main.ts; perry main.ts -o out && PERRY_ALLOW_UNIMPLEMENTED=1 ./out`) threw `TypeError: Cannot read properties of undefined (reading 'prototype')` at module load. The throw site is pino's `node_modules/pino/lib/proto.js:77`: `Object.setPrototypeOf(prototype, EventEmitter.prototype)`, where `EventEmitter` is the destructured binding from `const { EventEmitter } = require('node:events')` at line 5. **Root cause (two layered gaps).** (1) The CJS-wrap pass at `crates/perry/src/commands/compile/cjs_wrap.rs` synthesizes a `function require(specifier)` whose body returns native modules via `NativeModuleRef(<name>)` directly (e.g. `if (specifier === "node:events") return _req_0;` where `_req_0` is the imported binding lowered to `NativeModuleRef("events")`). The `Expr::NativeModuleRef(_) => Ok(double_literal(0.0))` value-form arm in `crates/perry-codegen/src/expr.rs:10317` returned the literal f64 `0.0` — NOT the NaN-boxed `undefined` tag, but plain numeric zero. So `Let { id: 6, init: Call(require, "node:events") }` produced `0.0`, and the subsequent `Let { id: 7, init: PropertyGet { LocalGet(6), "EventEmitter" } }` slow-pathed through `js_object_get_field_by_name` with a null receiver, hit `obj.is_null()`, and returned `undefined`. The `(2) Let { id: 8, ... } ; ObjectSetPrototypeOf(LocalGet(8), PropertyGet { LocalGet(7), "prototype" })` then read `.prototype` on `undefined` — that's the `js_throw_type_error_property_access` site (#462). The direct AST form `import * as fs from "node:fs"; fs.constants.F_OK` doesn't hit this because the codegen fast path at `expr.rs:3615` matches `Expr::NativeModuleRef(_)` literally as the PropertyGet's object and short-circuits through `js_native_module_property_by_name`. The destructured-from-require shape walks through a local-id boundary that breaks the AST pattern match. (2) Even after materializing the namespace via `js_create_native_module_namespace`, the `NATIVE_MODULE_CLASS_ID` arm of `js_object_get_field_by_name` (object.rs:3821) only consulted `get_native_module_constant` — which has no entry for `("events", "EventEmitter")` — and returned `undefined`. The direct-AST fast path's `js_native_module_property_by_name` ALSO checks `is_native_module_callable_export` (tty.isatty, tty.ReadStream, tty.WriteStream) before returning undefined, and synthesizes a BOUND_METHOD_FUNC_PTR closure for those — but that mirror check was missing in the slow-path arm. **Fix.** Three coordinated changes: (a) `crates/perry-codegen/src/expr.rs` — replace the value-form `Expr::NativeModuleRef(_) => Ok(double_literal(0.0))` with a real `js_create_native_module_namespace(<name>)` runtime call so the require-result is a NATIVE_MODULE_CLASS_ID-tagged ObjectHeader (same shape the direct-AST fast path produces). (b) `crates/perry-codegen/src/runtime_decls.rs` — declare the new FFI. (c) `crates/perry-runtime/src/object.rs` — extend `is_native_module_callable_export` with `("events", "EventEmitter")` so a property-read on the events namespace produces a callable closure (typeof "function" matching Node), and mirror that synthesis into the `NATIVE_MODULE_CLASS_ID` arm of `js_object_get_field_by_name` so the destructure-from-require shape converges with the direct-AST shape. **Why callable instead of an INT32-tagged class ref.** A proper class-ref would let `EventEmitter.prototype` return the class itself (line 3394 reads `.prototype` on registered class IDs and returns the class ref). But we don't yet register `EventEmitter` in `CLASS_VTABLE_REGISTRY` for the namespace import path — that's a bigger surface to design. A callable closure satisfies the narrow contract: `EventEmitter` is truthy (closure pointer is neither null nor undefined), `typeof EventEmitter === "function"` matches Node, `EventEmitter.prototype` returns `undefined` (no closure-prototype dispatch), and `Object.setPrototypeOf(prototype, undefined)` is a no-op (`js_object_set_prototype_of` ignores its second argument — same documented limitation as chalk's path, see #893). `new EventEmitter()` still goes through the dedicated `lower_call/builtin.rs` path that allocates a real `EventEmitterHandle`, so dispatch coherence is preserved. **Validation.** Pino smoke test (`echo 'import pino from "pino"; console.log("smoke:", typeof (pino as any));' > main.ts && perry main.ts -o out && PERRY_ALLOW_UNIMPLEMENTED=1 ./out`) no longer trips the prototype TypeError — module init advances past `lib/proto.js` and now hits a different downstream gap (`Cannot read properties of undefined (reading 'ASC')` from `SORTING_ORDER.ASC` in `pino.js:55`, separate issue tracking pino's `./lib/constants` symbol propagation). New regression test `test-files/test_issue_pino_prototype_undefined.ts` covers the minimal verbatim shape — destructured EventEmitter, `.prototype` read as a value, the `Object.setPrototypeOf(prototype, EventEmitter.prototype)` chain, and `Object.create(prototype)` factory — all four checkpoints produce non-error output. `cargo fmt --all` clean. `cargo build --release -p perry` clean. **Files touched.** `crates/perry-codegen/src/expr.rs` (value-form NativeModuleRef arm), `crates/perry-codegen/src/runtime_decls.rs` (FFI declaration), `crates/perry-runtime/src/object.rs` (callable-export whitelist + slow-path arm), `test-files/test_issue_pino_prototype_undefined.ts` (regression). Refs #793 (Node.js + TypeScript compatibility roadmap), #805 (npm sweep), #890 (the family of cross-module undefined-import bugs).
 
 ## v0.5.937 — fix(runtime): `js_is_truthy` no longer SIGSEGVs when a plain f64 bit pattern lands in the legacy raw-string-pointer range. **Symptom.** dayjs (`mkdir /tmp/perry-dayjs-x && echo '{"perry":{"compilePackages":["dayjs"]}}' > package.json && npm install && perry main.ts -o out && ./out`) exited 139 (SIGSEGV) with empty stdout. Crashed inside `js_is_truthy` at `crates/perry-runtime/src/value.rs:1762` on a value with `bits=0x646e` — a small integer dereferenced as `*StringHeader`. Surfaced when dayjs's `parse()` constructor body called `b.u(e)` on a utility-object closure; the call's result (or some adjacent stack slot) carried the offending bit pattern through the closure's outer truthy gate. **Root cause.** The "raw pointer bits (from bitcast of string literal)" fallback at line 1826 matched everything in the range `0x1000 < bits < 0x0001_0000_0000_0000` and then dereferenced as `*StringHeader` to read its length. `0x646e` (25710) sat squarely inside that window — it can be the bit pattern of an f64 denormal (`f64::from_bits(0x646e)` ≈ 1.27e-319), an unboxed-integer storage shape, or any other plain f64 whose bits happen to land below the 4 GiB mark. The 4 KiB lower bound was set when this branch was written assuming the only callers were string literals lowered as raw bitcasts — that assumption stopped holding once arbitrary `any`-typed values flowed through truthy gates. **Fix.** Three coordinated tightening changes in `js_is_truthy`: (1) raise the raw-pointer lower bound from `0x1000` (4 KiB — let any small integer through) to `0x10_0000` (1 MiB — well below any realistic userspace heap address on macOS/Linux but well above any small-integer or denormal bit pattern that could survive an `any`-typed call); (2) require 8-byte alignment (`bits & 0x7 == 0`) — `StringHeader` is `repr(C)` with usize-aligned fields, so a valid pointer must have its low 3 bits clear, which most small-integer-shaped patterns fail; (3) add an explicit `SHORT_STRING_TAG` branch above the raw-pointer fallback so inline-SSO empties are correctly classified as falsy via `(bits & SHORT_STRING_LEN_MASK) >> SHORT_STRING_LEN_SHIFT == 0` rather than punted to the f64 catch-all (which would have reported them as truthy because the bit pattern is non-zero non-NaN). The legacy raw-string-bitcast path is preserved for real heap pointers — only false positives are now rejected. **Validation.** The user's dayjs repro no longer SIGSEGVs (advances to a separate, downstream `TypeError: (number).getDay is not a function` from a different lowering path — out of scope here, tracked separately). New regression test `test-files/test_issue_dayjs_is_truthy_smallint.ts` covers (a) a small `0x646e` integer truthy gate, (b) `0.0` falsy gate, (c) a `1` integer truthy gate — all three byte-for-byte parity with `node --experimental-strip-types`. Build clean (`cargo build --release -p perry-runtime -p perry-stdlib -p perry`). **Files touched.** `crates/perry-runtime/src/value.rs` (~30 lines in `js_is_truthy` — SSO branch + raw-pointer-bounds tightening + alignment check), `test-files/test_issue_dayjs_is_truthy_smallint.ts` (regression). Refs #793 (Node.js + TypeScript compatibility roadmap), #805 (npm sweep — dayjs).
diff --git a/CLAUDE.md b/CLAUDE.md
index 2bc916e82e..4f4e5a9b29 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -8,7 +8,11 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 Perry is a native TypeScript compiler written in Rust that compiles TypeScript source code directly to native executables. It uses SWC for TypeScript parsing and LLVM for code generation.
 
-**Current Version:** 0.5.938
+<<<<<<< HEAD
+**Current Version:** 0.5.940
+=======
+**Current Version:** 0.5.940
+>>>>>>> 408d8acb (fix(codegen): #894 — class-expression static [Symbol] sees populated module lets)
 
 
 ## TypeScript Parity Status
diff --git a/Cargo.lock b/Cargo.lock
index c579d8d985..a135256a63 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -459,9 +459,9 @@ dependencies = [
 
 [[package]]
 name = "aws-lc-rs"
-version = "1.16.3"
+version = "1.17.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0ec6fb3fe69024a75fa7e1bfb48aa6cf59706a101658ea01bfd33b2b248a038f"
+checksum = "5ec2f1fc3ec205783a5da9a7e6c1509cc69dedf09a1949e412c1e18469326d00"
 dependencies = [
  "aws-lc-sys",
  "zeroize",
@@ -469,9 +469,9 @@ dependencies = [
 
 [[package]]
 name = "aws-lc-sys"
-version = "0.40.0"
+version = "0.41.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f50037ee5e1e41e7b8f9d161680a725bd1626cb6f8c7e901f91f942850852fe7"
+checksum = "1a2f9779ce85b93ab6170dd940ad0169b5766ff848247aff13bb788b832fe3f4"
 dependencies = [
  "cc",
  "cmake",
@@ -3023,9 +3023,9 @@ dependencies = [
 
 [[package]]
 name = "hstr"
-version = "3.0.4"
+version = "3.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "faa57007c3c9dab34df2fa4c1fb52fe9c34ec5a27ed9d8edea53254b50cd7887"
+checksum = "c1b94e40256e78ddd4e30490aa931bec17e65e9413a6ad11f64ec67815da9323"
 dependencies = [
  "hashbrown 0.14.5",
  "new_debug_unreachable",
@@ -3620,9 +3620,9 @@ dependencies = [
 
 [[package]]
 name = "js-sys"
-version = "0.3.95"
+version = "0.3.98"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2964e92d1d9dc3364cae4d718d93f227e3abb088e747d92e0395bfdedf1c12ca"
+checksum = "67df7112613f8bfd9150013a0314e196f4800d3201ae742489d999db2f979f08"
 dependencies = [
  "cfg-if",
  "futures-util",
@@ -3666,11 +3666,11 @@ dependencies = [
 
 [[package]]
 name = "kqueue-sys"
-version = "1.0.4"
+version = "1.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed9625ffda8729b85e45cf04090035ac368927b8cebc34898e7c120f52e4838b"
+checksum = "07293a4e297ac234359b510362495713f75ea345d5307140414f20c69ffeb087"
 dependencies = [
- "bitflags 1.3.2",
+ "bitflags 2.11.1",
  "libc",
 ]
 
@@ -3795,7 +3795,7 @@ dependencies = [
  "bitflags 2.11.1",
  "libc",
  "plain",
- "redox_syscall 0.7.3",
+ "redox_syscall 0.7.5",
 ]
 
 [[package]]
@@ -4790,7 +4790,7 @@ checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
 [[package]]
 name = "perry"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "base64",
@@ -4845,14 +4845,14 @@ dependencies = [
 
 [[package]]
 name = "perry-api-manifest"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "perry-codegen"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "log",
@@ -4865,7 +4865,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-arkts"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -4874,7 +4874,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-glance"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -4882,7 +4882,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-js"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-dispatch",
@@ -4892,7 +4892,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-swiftui"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -4901,7 +4901,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-wasm"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "base64",
@@ -4914,7 +4914,7 @@ dependencies = [
 
 [[package]]
 name = "perry-codegen-wear-tiles"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -4922,7 +4922,7 @@ dependencies = [
 
 [[package]]
 name = "perry-diagnostics"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "serde",
  "serde_json",
@@ -4930,7 +4930,7 @@ dependencies = [
 
 [[package]]
 name = "perry-dispatch"
-version = "0.5.938"
+version = "0.5.940"
 
 [[package]]
 name = "perry-doc-fixture-my-bindings"
@@ -4941,7 +4941,7 @@ dependencies = [
 
 [[package]]
 name = "perry-doc-tests"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "clap",
@@ -4956,7 +4956,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-argon2"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "argon2",
  "perry-ffi",
@@ -4964,7 +4964,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-axios"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "reqwest",
@@ -4973,7 +4973,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-bcrypt"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "bcrypt",
  "perry-ffi",
@@ -4981,7 +4981,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-better-sqlite3"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "rusqlite",
@@ -4989,7 +4989,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-cheerio"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "scraper",
@@ -4997,14 +4997,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-commander"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-cron"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "chrono",
  "cron",
@@ -5013,7 +5013,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-dayjs"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5021,7 +5021,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-decimal"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "rust_decimal",
@@ -5029,7 +5029,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-dotenv"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "serde_json",
@@ -5037,7 +5037,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ethers"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "rand 0.8.6",
@@ -5045,21 +5045,21 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-events"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-exponential-backoff"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-fastify"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "bytes",
  "http-body-util",
@@ -5073,7 +5073,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-fetch"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -5084,7 +5084,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-http"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "lazy_static",
  "perry-ext-http-server",
@@ -5096,7 +5096,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-http-server"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "bytes",
  "http-body-util",
@@ -5115,7 +5115,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ioredis"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -5125,7 +5125,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-jsonwebtoken"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "base64",
  "jsonwebtoken",
@@ -5136,7 +5136,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-lru-cache"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "lru",
  "perry-ffi",
@@ -5144,7 +5144,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-moment"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5152,7 +5152,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-mongodb"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "bson",
  "futures-util",
@@ -5164,7 +5164,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-mysql2"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "chrono",
  "perry-ffi",
@@ -5174,7 +5174,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-nanoid"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "nanoid",
  "perry-ffi",
@@ -5183,7 +5183,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-net"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "rustls",
@@ -5194,7 +5194,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-nodemailer"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "lettre",
  "perry-ffi",
@@ -5204,7 +5204,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-pg"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "sqlx",
@@ -5213,7 +5213,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ratelimit"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "governor",
  "perry-ffi",
@@ -5221,7 +5221,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-sharp"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "base64",
  "image",
@@ -5230,14 +5230,14 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-slugify"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
 ]
 
 [[package]]
 name = "perry-ext-streams"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "lazy_static",
  "perry-ffi",
@@ -5245,7 +5245,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-uuid"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "uuid",
@@ -5253,7 +5253,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-validator"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "perry-ffi",
  "regex",
@@ -5263,7 +5263,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-ws"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "futures-util",
  "lazy_static",
@@ -5274,7 +5274,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ext-zlib"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "flate2",
  "perry-ffi",
@@ -5282,7 +5282,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ffi"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "dashmap 6.1.0",
  "once_cell",
@@ -5291,7 +5291,7 @@ dependencies = [
 
 [[package]]
 name = "perry-hir"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-api-manifest",
@@ -5305,7 +5305,7 @@ dependencies = [
 
 [[package]]
 name = "perry-jsruntime"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "deno_core",
@@ -5325,7 +5325,7 @@ dependencies = [
 
 [[package]]
 name = "perry-parser"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-diagnostics",
@@ -5337,7 +5337,7 @@ dependencies = [
 
 [[package]]
 name = "perry-runtime"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "base64",
@@ -5361,7 +5361,7 @@ dependencies = [
 
 [[package]]
 name = "perry-stdlib"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "aes",
  "aes-gcm",
@@ -5429,7 +5429,7 @@ dependencies = [
 
 [[package]]
 name = "perry-transform"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "perry-hir",
@@ -5439,7 +5439,7 @@ dependencies = [
 
 [[package]]
 name = "perry-types"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "anyhow",
  "thiserror 1.0.69",
@@ -5447,11 +5447,11 @@ dependencies = [
 
 [[package]]
 name = "perry-ui"
-version = "0.5.938"
+version = "0.5.940"
 
 [[package]]
 name = "perry-ui-android"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "itoa",
  "jni",
@@ -5466,7 +5466,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-geisterhand"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "rand 0.8.6",
  "serde",
@@ -5476,7 +5476,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-gtk4"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "cairo-rs",
  "dirs 5.0.1",
@@ -5495,7 +5495,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-ios"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "block2",
  "libc",
@@ -5510,7 +5510,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-macos"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "block2",
  "libc",
@@ -5528,11 +5528,11 @@ version = "0.1.0"
 
 [[package]]
 name = "perry-ui-testkit"
-version = "0.5.938"
+version = "0.5.940"
 
 [[package]]
 name = "perry-ui-tvos"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "block2",
  "libc",
@@ -5547,7 +5547,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-visionos"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "block2",
  "libc",
@@ -5562,7 +5562,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-watchos"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "block2",
  "libc",
@@ -5575,7 +5575,7 @@ dependencies = [
 
 [[package]]
 name = "perry-ui-windows"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "libc",
  "perry-runtime",
@@ -5589,7 +5589,7 @@ dependencies = [
 
 [[package]]
 name = "perry-updater"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "base64",
  "ed25519-dalek",
@@ -5603,7 +5603,7 @@ dependencies = [
 
 [[package]]
 name = "perry-wasm-host"
-version = "0.5.938"
+version = "0.5.940"
 dependencies = [
  "wasmi",
 ]
@@ -5705,18 +5705,18 @@ dependencies = [
 
 [[package]]
 name = "pin-project"
-version = "1.1.12"
+version = "1.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cbf0d9e68100b3a7989b4901972f265cd542e560a3a8a724e1e20322f4d06ce9"
+checksum = "2466b2336ed02bcdca6b294417127b90ec92038d1d5c4fbeac971a922e0e0924"
 dependencies = [
  "pin-project-internal",
 ]
 
 [[package]]
 name = "pin-project-internal"
-version = "1.1.12"
+version = "1.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a990e22f43e84855daf260dded30524ef4a9021cc7541c26540500a50b624389"
+checksum = "c96395f0a926bc13b1c17622aaddda1ecb55d49c8f1bf9777e4d877800a43f8b"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -6278,9 +6278,9 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.7.3"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ce70a74e890531977d37e532c34d45e9055d2409ed08ddba14529471ed0be16"
+checksum = "4666a1a60d8412eab19d94f6d13dcc9cea0a5ef4fdf6a5db306537413c661b1b"
 dependencies = [
  "bitflags 2.11.1",
 ]
@@ -6880,9 +6880,9 @@ dependencies = [
 
 [[package]]
 name = "serde_with"
-version = "3.19.0"
+version = "3.20.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f05839ce67618e14a09b286535c0d9c94e85ef25469b0e13cb4f844e5593eb19"
+checksum = "e72c1c2cb7b223fafb600a619537a871c2818583d619401b785e7c0b746ccde2"
 dependencies = [
  "serde_core",
  "serde_with_macros",
@@ -6890,9 +6890,9 @@ dependencies = [
 
 [[package]]
 name = "serde_with_macros"
-version = "3.19.0"
+version = "3.20.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cf2ebbe86054f9b45bc3881e865683ccfaccce97b9b4cb53f3039d67f355a334"
+checksum = "b90c488738ecb4fb0262f41f43bc40efc5868d9fb744319ddf5f5317f417bfac"
 dependencies = [
  "darling 0.23.0",
  "proc-macro2",
@@ -7444,9 +7444,9 @@ checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 
 [[package]]
 name = "swc_atoms"
-version = "9.0.0"
+version = "9.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d4ccbe2ecad10ad7432100f878a107b1d972a8aee83ca53184d00c23a078bb8a"
+checksum = "ecbd7177c71140b23dc6b1b9c1a9f16f96d0337cb999f5a79bb49ca4d82eded0"
 dependencies = [
  "hstr",
  "once_cell",
@@ -8478,11 +8478,11 @@ checksum = "ccf3ec651a847eb01de73ccad15eb7d99f80485de043efb2f370cd654f4ea44b"
 
 [[package]]
 name = "wasip2"
-version = "1.0.2+wasi-0.2.9"
+version = "1.0.3+wasi-0.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9517f9239f02c069db75e65f174b3da828fe5f5b945c4dd26bd25d89c03ebcf5"
+checksum = "20064672db26d7cdc89c7798c48a0fdfac8213434a1186e5ef29fd560ae223d6"
 dependencies = [
- "wit-bindgen",
+ "wit-bindgen 0.57.1",
 ]
 
 [[package]]
@@ -8491,7 +8491,7 @@ version = "0.4.0+wasi-0.3.0-rc-2026-01-06"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5428f8bf88ea5ddc08faddef2ac4a67e390b88186c703ce6dbd955e1c145aca5"
 dependencies = [
- "wit-bindgen",
+ "wit-bindgen 0.51.0",
 ]
 
 [[package]]
@@ -8502,9 +8502,9 @@ checksum = "b8dad83b4f25e74f184f64c43b150b91efe7647395b42289f38e50566d82855b"
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.118"
+version = "0.2.121"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0bf938a0bacb0469e83c1e148908bd7d5a6010354cf4fb73279b7447422e3a89"
+checksum = "49ace1d07c165b0864824eee619580c4689389afa9dc9ed3a4c75040d82e6790"
 dependencies = [
  "cfg-if",
  "once_cell",
@@ -8516,9 +8516,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-futures"
-version = "0.4.68"
+version = "0.4.71"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f371d383f2fb139252e0bfac3b81b265689bf45b6874af544ffa4c975ac1ebf8"
+checksum = "96492d0d3ffba25305a7dc88720d250b1401d7edca02cc3bcd50633b424673b8"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -8526,9 +8526,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.118"
+version = "0.2.121"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eeff24f84126c0ec2db7a449f0c2ec963c6a49efe0698c4242929da037ca28ed"
+checksum = "8e68e6f4afd367a562002c05637acb8578ff2dea1943df76afb9e83d177c8578"
 dependencies = [
  "quote",
  "wasm-bindgen-macro-support",
@@ -8536,9 +8536,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.118"
+version = "0.2.121"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d08065faf983b2b80a79fd87d8254c409281cf7de75fc4b773019824196c904"
+checksum = "d95a9ec35c64b2a7cb35d3fead40c4238d0940c86d107136999567a4703259f2"
 dependencies = [
  "bumpalo",
  "proc-macro2",
@@ -8549,9 +8549,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.118"
+version = "0.2.121"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5fd04d9e306f1907bd13c6361b5c6bfc7b3b3c095ed3f8a9246390f8dbdee129"
+checksum = "c4e0100b01e9f0d03189a92b96772a1fb998639d981193d7dbab487302513441"
 dependencies = [
  "unicode-ident",
 ]
@@ -8600,9 +8600,9 @@ dependencies = [
 
 [[package]]
 name = "wasmi"
-version = "0.51.4"
+version = "0.51.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cc0120da23bc519b1d573e64ffe2a91390468293242db4edc5517f481d7e495d"
+checksum = "bb321403ce594274827657a908e13d1d9918aa02257b8bf8391949d9764023ff"
 dependencies = [
  "spin",
  "wasmi_collections",
@@ -8669,9 +8669,9 @@ dependencies = [
 
 [[package]]
 name = "web-sys"
-version = "0.3.95"
+version = "0.3.98"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4f2dfbb17949fa2088e5d39408c48368947b86f7834484e87b73de55bc14d97d"
+checksum = "4b572dff8bcf38bad0fa19729c89bb5748b2b9b1d8be70cf90df697e3a8f32aa"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -9284,9 +9284,9 @@ checksum = "d6bbff5f0aada427a1e5a6da5f1f98158182f26556f345ac9e04d36d0ebed650"
 
 [[package]]
 name = "winnow"
-version = "1.0.2"
+version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2ee1708bef14716a11bae175f579062d4554d95be2c6829f518df847b7b3fdd0"
+checksum = "0592e1c9d151f854e6fd382574c3a0855250e1d9b2f99d9281c6e6391af352f1"
 dependencies = [
  "memchr",
 ]
@@ -9306,6 +9306,12 @@ dependencies = [
  "wit-bindgen-rust-macro",
 ]
 
+[[package]]
+name = "wit-bindgen"
+version = "0.57.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1ebf944e87a7c253233ad6766e082e3cd714b5d03812acc24c318f549614536e"
+
 [[package]]
 name = "wit-bindgen-core"
 version = "0.51.0"
diff --git a/Cargo.toml b/Cargo.toml
index f5c36e4c16..cf4cc7cc1a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -190,7 +190,7 @@ opt-level = "s"       # Optimize for size in stdlib
 opt-level = 3
 
 [workspace.package]
-version = "0.5.938"
+version = "0.5.940"
 edition = "2021"
 license = "MIT"
 repository = "https://github.com/PerryTS/perry"
diff --git a/crates/perry-codegen/src/codegen.rs b/crates/perry-codegen/src/codegen.rs
index 65ae0d92bd..81cdf9b16b 100644
--- a/crates/perry-codegen/src/codegen.rs
+++ b/crates/perry-codegen/src/codegen.rs
@@ -1233,6 +1233,21 @@ pub fn compile_module(hir: &HirModule, opts: CompileOptions) -> Result<Vec<u8>>
                 method_has_rest.insert((cls.name.clone(), m.name.clone()), true);
             }
         }
+        // Issue #894: track static methods too. Effect's `static pipe()` /
+        // `static annotations()` synthesize a trailing `...arguments` rest
+        // param when the body reads `arguments`. The StaticMethodCall
+        // lowering at `expr.rs::Expr::StaticMethodCall` reads
+        // `method_has_rest` to decide whether to bundle trailing args into
+        // a rest array; without this, `Cls.pipe(a, b)` calls the method
+        // with 2 scalar args while the signature expects (rest_array),
+        // and `arguments.length` reads garbage / undefined.
+        for sm in &cls.static_methods {
+            method_param_counts.insert((cls.name.clone(), sm.name.clone()), sm.params.len());
+            let has_rest = sm.params.iter().any(|p| p.is_rest);
+            if has_rest {
+                method_has_rest.insert((cls.name.clone(), sm.name.clone()), true);
+            }
+        }
     }
     for ic in &opts.imported_classes {
         let effective_name = ic.local_alias.as_deref().unwrap_or(&ic.name).to_string();
@@ -1665,8 +1680,9 @@ pub fn compile_module(hir: &HirModule, opts: CompileOptions) -> Result<Vec<u8>>
     for c in &hir.classes {
         for sf in &c.static_fields {
             // Computed-key static fields (`static [Symbol.for(...)] = init`)
-            // are stored in a runtime side table by `init_static_fields`;
-            // they don't get a string-named global. Refs #420.
+            // are stored in a runtime side table by
+            // `init_static_fields_late`; they don't get a string-named
+            // global. Refs #420, #894.
             if sf.key_expr.is_some() {
                 continue;
             }
@@ -4731,9 +4747,16 @@ fn compile_module_entry(
         register_module_globals_as_gc_roots(&mut ctx, module_globals);
         // Initialize static class fields with their declared init
         // expressions. Runs once at the top of main, before user code.
-        init_static_fields(&mut ctx, hir)?;
+        //
+        // Split into two phases (#894): early emits the bits that don't
+        // read user-let values (Error-extending class registry, well-
+        // known symbol method hooks); late runs AFTER user init so
+        // computed-Symbol-key static fields whose key/init reference
+        // module-level lets see populated slots.
+        init_static_fields_early(&mut ctx, hir)?;
         stmt::lower_stmts(&mut ctx, &hir.init)
             .with_context(|| format!("lowering init statements of module '{}'", hir.name))?;
+        init_static_fields_late(&mut ctx, hir)?;
 
         // Issue #100: populate `@__perry_ns_<module_prefix>` from the
         // namespace_entries list AFTER user init has run (so every
@@ -5095,13 +5118,18 @@ fn compile_module_entry(
         // right after js_gc_init, so by the time any user code executes
         // every module's globals are already GC-rooted.
         register_module_globals_as_gc_roots(&mut ctx, module_globals);
-        init_static_fields(&mut ctx, hir)?;
+        // Issue #894: split into early/late around `lower_stmts` so a
+        // computed-Symbol-key static field whose key/init reference
+        // top-level module lets (e.g. effect's `make()` factory:
+        // `static [TypeId] = variance`) sees populated globals.
+        init_static_fields_early(&mut ctx, hir)?;
         stmt::lower_stmts(&mut ctx, &hir.init).with_context(|| {
             format!(
                 "lowering init statements of non-entry module '{}'",
                 hir.name
             )
         })?;
+        init_static_fields_late(&mut ctx, hir)?;
 
         // Issue #100: populate `@__perry_ns_<module_prefix>` from the
         // namespace_entries list at the tail of the non-entry __init.
@@ -5919,12 +5947,17 @@ fn register_module_globals_as_gc_roots(
     }
 }
 
-/// Initialize each class's static fields with their declared init
-/// expressions. Called at the top of compile_module_entry's main /
-/// __init function. The static field globals were registered in
-/// compile_module — this just emits the per-field "store init value
-/// to global" sequence.
-fn init_static_fields(ctx: &mut crate::expr::FnCtx<'_>, hir: &HirModule) -> Result<()> {
+/// Early static-field setup: registrations that don't read any
+/// module-level binding's value (Error-extending classes, well-known
+/// symbol method hooks). Safe to emit before `stmt::lower_stmts` —
+/// values referenced are either compile-time constants (class ids,
+/// function pointers) or computed entirely from `hir` metadata.
+///
+/// The split (early vs. late) was introduced for issue #894 (effect's
+/// `make()` factory's `static [TypeId] = variance` — both the key and
+/// the init reference module-level lets that haven't been initialized
+/// at the point the old combined `init_static_fields` ran).
+fn init_static_fields_early(ctx: &mut crate::expr::FnCtx<'_>, hir: &HirModule) -> Result<()> {
     // Phase C.3: register user classes that extend the built-in Error
     // (or any of its subclasses) with the runtime, so `instanceof Error`
     // walks the chain and returns true. Without this, `new HttpError(...)
@@ -6002,6 +6035,27 @@ fn init_static_fields(ctx: &mut crate::expr::FnCtx<'_>, hir: &HirModule) -> Resu
             &[(crate::types::I32, &cid_str), (I64, &func_ptr_i64)],
         );
     }
+    Ok(())
+}
+
+/// Late static-field setup: per-class static-field initializer evaluation,
+/// computed-Symbol-key registration, and static-block invocation. Must
+/// run AFTER `stmt::lower_stmts` so module-level lets referenced by
+/// these initializers (e.g. `static [TypeId] = variance` where both
+/// `TypeId` and `variance` are top-level `const`s) read their populated
+/// global slots rather than the zero default.
+///
+/// Issue #894: effect's `function make(ast) { return class { static
+/// [TypeId] = variance } }` factory pattern hit this; the `TypeId`
+/// symbol and `variance` value were both top-level module lets, and
+/// the pre-#894 combined `init_static_fields` ran before user init,
+/// so `js_class_register_static_symbol(class_id, 0.0, 0.0)` registered
+/// nothing reachable. `isSchema(C)` then returned false on a class
+/// returned from `make`, dual()'s predicate failed, and the failing
+/// `.annotations({...})` chain eventually fed `undefined` to a `make`
+/// call that read `ast._tag` → `TypeError: Cannot read properties of
+/// undefined (reading '_tag')` during Schema.ts module init.
+fn init_static_fields_late(ctx: &mut crate::expr::FnCtx<'_>, hir: &HirModule) -> Result<()> {
     // Issue #685: nested classes (declared as expressions inside a
     // factory function body, e.g. `return class X extends Y { static
     // params = params.slice() }` in effect's `TemplateLiteralParser`)
diff --git a/crates/perry-codegen/src/collectors.rs b/crates/perry-codegen/src/collectors.rs
index 146c0f027e..a3b149fb1a 100644
--- a/crates/perry-codegen/src/collectors.rs
+++ b/crates/perry-codegen/src/collectors.rs
@@ -1127,6 +1127,23 @@ pub(crate) fn collect_ref_ids_in_expr(e: &perry_hir::Expr, out: &mut HashSet<u32
                 walk(e, out);
             }
         }
+        // Issue #894: prepended to the Sequence wrapping `Expr::ClassRef`
+        // for class expressions returned from factory functions. The
+        // key/value reference module-level (or function-local) lets;
+        // collecting their refs here is what causes the surrounding
+        // function-body scan to add those lets to `referenced_from_fn`,
+        // which is what `module_globals` is built from.
+        Expr::RegisterClassStaticSymbol {
+            key_expr,
+            value_expr,
+            ..
+        } => {
+            walk(key_expr, out);
+            walk(value_expr, out);
+        }
+        Expr::RegisterClassParentDynamic { parent_expr, .. } => {
+            walk(parent_expr, out);
+        }
         _ => {}
     }
 }
diff --git a/crates/perry-codegen/src/expr.rs b/crates/perry-codegen/src/expr.rs
index 51ba95fa4d..739933484f 100644
--- a/crates/perry-codegen/src/expr.rs
+++ b/crates/perry-codegen/src/expr.rs
@@ -6331,6 +6331,48 @@ pub(crate) fn lower_expr(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
                 for a in args {
                     lowered.push(lower_expr(ctx, a)?);
                 }
+                // Issue #894: static methods with synthetic `...arguments`
+                // rest params (or any user-declared rest param) need their
+                // trailing args bundled into an array. Without this,
+                // `Cls.pipe(a, b)` on a body that reads `arguments`
+                // emits a 2-scalar call against a 1-rest-array signature,
+                // leaving `arguments` bound to whichever scalar landed
+                // in the rest slot — `arguments.length` then reads garbage
+                // or hits the codegen-fallback undefined.
+                let has_rest = ctx.method_has_rest.get(&key).copied().unwrap_or(false);
+                if has_rest {
+                    let declared_count = ctx.method_param_counts.get(&key).copied().unwrap_or(0);
+                    if declared_count > 0 {
+                        let fixed = declared_count.saturating_sub(1);
+                        if lowered.len() >= fixed {
+                            let trailing: Vec<String> = lowered.split_off(fixed);
+                            let arr_handle = ctx.block().call(
+                                I64,
+                                "js_array_alloc",
+                                &[(I32, &trailing.len().to_string())],
+                            );
+                            // js_array_push_f64 may realloc and return a
+                            // possibly-new handle; thread it.
+                            let mut handle_cur = arr_handle;
+                            for v in &trailing {
+                                handle_cur = ctx.block().call(
+                                    I64,
+                                    "js_array_push_f64",
+                                    &[(I64, &handle_cur), (DOUBLE, v)],
+                                );
+                            }
+                            let arr_box = nanbox_pointer_inline(ctx.block(), &handle_cur);
+                            lowered.push(arr_box);
+                        }
+                        // Pad fixed slots with undefined when caller under-supplied.
+                        while lowered.len() < declared_count {
+                            // Insert undefined at the rest-slot's predecessor.
+                            let undef = double_literal(f64::from_bits(0x7FFC_0000_0000_0001));
+                            let idx = lowered.len().saturating_sub(1);
+                            lowered.insert(idx, undef);
+                        }
+                    }
+                }
                 let arg_slices: Vec<(crate::types::LlvmType, &str)> =
                     lowered.iter().map(|s| (DOUBLE, s.as_str())).collect();
                 return Ok(ctx.block().call(DOUBLE, &fn_name, &arg_slices));
@@ -10214,6 +10256,37 @@ pub(crate) fn lower_expr(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
             // observable to user code.
             Ok(double_literal(f64::from_bits(0x7FFC_0000_0000_0001)))
         }
+        // Issue #894: `static [Symbol.for("k")] = init` inside a
+        // class expression returned from a factory function. Emitted
+        // by HIR lowering as a `Sequence([…, RegisterClassStaticSymbol,
+        // ClassRef])` so each factory invocation re-registers the
+        // (class_id, sym_key) → value entry. Without this, the
+        // registration would only happen at module-init time when
+        // referenced free variables may not yet be assigned, and
+        // `isSchema(C)` (which checks `TypeId in C`) returns false on
+        // a freshly-returned class.
+        Expr::RegisterClassStaticSymbol {
+            class_name,
+            key_expr,
+            value_expr,
+        } => {
+            let key_v = lower_expr(ctx, key_expr)?;
+            let val_v = lower_expr(ctx, value_expr)?;
+            if let Some(&class_id) = ctx.class_ids.get(class_name) {
+                if class_id != 0 {
+                    let cid_str = class_id.to_string();
+                    ctx.block().call_void(
+                        "js_class_register_static_symbol",
+                        &[
+                            (crate::types::I32, &cid_str),
+                            (DOUBLE, &key_v),
+                            (DOUBLE, &val_v),
+                        ],
+                    );
+                }
+            }
+            Ok(double_literal(f64::from_bits(0x7FFC_0000_0000_0001)))
+        }
         // Issue #711 part 2: `<expr>.prototype = <expr>` pattern.
         // Calls `js_set_function_prototype(func, proto)`, which (when
         // func is a closure and proto is an object) allocates a
diff --git a/crates/perry-hir/src/ir.rs b/crates/perry-hir/src/ir.rs
index 2e1d88010f..75708ac5b6 100644
--- a/crates/perry-hir/src/ir.rs
+++ b/crates/perry-hir/src/ir.rs
@@ -1128,6 +1128,22 @@ pub enum Expr {
         parent_expr: Box<Expr>,
     },
 
+    /// Issue #894: `class C { static [keyExpr] = initExpr }` where the
+    /// class is returned from a factory function body. The static-Symbol
+    /// registration must re-run each time the factory is called, with
+    /// the key/init evaluated against the current scope (closure
+    /// captures + module lets that may have been assigned by user code
+    /// between the class's HIR hoisting and the factory call).
+    /// Sequenced in front of the `ClassRef` returned from the
+    /// `ast::Expr::Class` lowering, parallel to
+    /// `RegisterClassParentDynamic`. Codegen emits a call to
+    /// `js_class_register_static_symbol(class_id, key, value)`.
+    RegisterClassStaticSymbol {
+        class_name: String,
+        key_expr: Box<Expr>,
+        value_expr: Box<Expr>,
+    },
+
     // Issue #711 part 2: `<func_expr>.prototype = <obj_expr>` pattern,
     // used by Effect's effectable.ts to declare prototype-based
     // classes. Codegen emits a call to `js_set_function_prototype`
diff --git a/crates/perry-hir/src/lower.rs b/crates/perry-hir/src/lower.rs
index f59b383b59..f5eeb47122 100644
--- a/crates/perry-hir/src/lower.rs
+++ b/crates/perry-hir/src/lower.rs
@@ -8997,16 +8997,47 @@ pub(crate) fn lower_expr(ctx: &mut LoweringContext, expr: &ast::Expr) -> Result<
             // Sequence yields its last element, so the value remains the
             // ClassRef the call site expects.
             let parent_expr = class.extends_expr.clone();
+            // Issue #894: collect computed-Symbol-key static fields so
+            // codegen emits a `RegisterClassStaticSymbol` registration
+            // sequenced in front of the ClassRef. Without this, the
+            // registration happens at module init via
+            // `init_static_fields_late` — but the values referenced by
+            // the key/init may not be valid yet (the factory hasn't been
+            // called, so any function-local captures are zero) or the
+            // class lookup may happen BEFORE module init's late phase
+            // (within the same module's top-level expressions). Effect's
+            // `make()` factory's `static [TypeId] = variance` is the
+            // canonical case: `isSchema(C)` was called from Schema.ts's
+            // own top-level `class extends transform(...)` chains, which
+            // run before the module's `init_static_fields_late`.
+            let static_symbol_registrations: Vec<(Expr, Expr)> = class
+                .static_fields
+                .iter()
+                .filter_map(|sf| match (sf.key_expr.as_ref(), sf.init.as_ref()) {
+                    (Some(k), Some(v)) => Some((k.clone(), v.clone())),
+                    _ => None,
+                })
+                .collect();
             ctx.pending_classes.push(class);
-            match parent_expr {
-                Some(p) => Ok(Expr::Sequence(vec![
-                    Expr::RegisterClassParentDynamic {
-                        class_name: synthetic_name.clone(),
-                        parent_expr: p,
-                    },
-                    Expr::ClassRef(synthetic_name),
-                ])),
-                None => Ok(Expr::ClassRef(synthetic_name)),
+            let mut seq: Vec<Expr> = Vec::new();
+            if let Some(p) = parent_expr {
+                seq.push(Expr::RegisterClassParentDynamic {
+                    class_name: synthetic_name.clone(),
+                    parent_expr: p,
+                });
+            }
+            for (k, v) in static_symbol_registrations {
+                seq.push(Expr::RegisterClassStaticSymbol {
+                    class_name: synthetic_name.clone(),
+                    key_expr: Box::new(k),
+                    value_expr: Box::new(v),
+                });
+            }
+            if seq.is_empty() {
+                Ok(Expr::ClassRef(synthetic_name))
+            } else {
+                seq.push(Expr::ClassRef(synthetic_name));
+                Ok(Expr::Sequence(seq))
             }
         }
         ast::Expr::JSXElement(jsx) => lower_jsx_element(ctx, jsx),
diff --git a/crates/perry-hir/src/stable_hash.rs b/crates/perry-hir/src/stable_hash.rs
index 443de1146e..9ae745b03f 100644
--- a/crates/perry-hir/src/stable_hash.rs
+++ b/crates/perry-hir/src/stable_hash.rs
@@ -3571,6 +3571,16 @@ impl SH for Expr {
                 class_name.hash(h);
                 parent_expr.as_ref().hash(h);
             }
+            Expr::RegisterClassStaticSymbol {
+                class_name,
+                key_expr,
+                value_expr,
+            } => {
+                tag(h, 465);
+                class_name.hash(h);
+                key_expr.as_ref().hash(h);
+                value_expr.as_ref().hash(h);
+            }
             Expr::SetFunctionPrototype { func, proto } => {
                 tag(h, 448);
                 func.as_ref().hash(h);
diff --git a/crates/perry-hir/src/walker.rs b/crates/perry-hir/src/walker.rs
index fa766735b8..14a56f34ea 100644
--- a/crates/perry-hir/src/walker.rs
+++ b/crates/perry-hir/src/walker.rs
@@ -405,6 +405,14 @@ where
         Expr::RegisterClassParentDynamic { parent_expr, .. } => {
             f(parent_expr);
         }
+        Expr::RegisterClassStaticSymbol {
+            key_expr,
+            value_expr,
+            ..
+        } => {
+            f(key_expr);
+            f(value_expr);
+        }
         Expr::SetFunctionPrototype { func, proto } => {
             f(func);
             f(proto);
@@ -1680,6 +1688,14 @@ where
         Expr::RegisterClassParentDynamic { parent_expr, .. } => {
             f(parent_expr);
         }
+        Expr::RegisterClassStaticSymbol {
+            key_expr,
+            value_expr,
+            ..
+        } => {
+            f(key_expr);
+            f(value_expr);
+        }
         Expr::SetFunctionPrototype { func, proto } => {
             f(func);
             f(proto);
diff --git a/crates/perry-transform/src/inline.rs b/crates/perry-transform/src/inline.rs
index bfe91801cc..08d28e9031 100644
--- a/crates/perry-transform/src/inline.rs
+++ b/crates/perry-transform/src/inline.rs
@@ -1066,6 +1066,28 @@ fn specialize_captured_class_factories(module: &mut Module) {
                     base_class_counter_seed,
                 );
             }
+            Expr::RegisterClassStaticSymbol {
+                key_expr,
+                value_expr,
+                ..
+            } => {
+                rewrite_call_init(
+                    key_expr,
+                    factory_targets,
+                    classes,
+                    new_classes,
+                    next_class_counter,
+                    base_class_counter_seed,
+                );
+                rewrite_call_init(
+                    value_expr,
+                    factory_targets,
+                    classes,
+                    new_classes,
+                    next_class_counter,
+                    base_class_counter_seed,
+                );
+            }
             Expr::New { args, .. } => {
                 for a in args.iter_mut() {
                     rewrite_call_init(
@@ -1966,6 +1988,7 @@ fn body_references_class_in_set(stmts: &[Stmt], set: &HashSet<String>) -> bool {
             | Expr::StaticFieldSet { class_name, .. }
             | Expr::ClassStaticSymbolSet { class_name, .. }
             | Expr::RegisterClassParentDynamic { class_name, .. }
+            | Expr::RegisterClassStaticSymbol { class_name, .. }
             | Expr::StaticMethodCall { class_name, .. } => {
                 if set.contains(class_name) {
                     return true;
diff --git a/test-files/test_issue_effect_tag_undefined.ts b/test-files/test_issue_effect_tag_undefined.ts
new file mode 100644
index 0000000000..55250cd5f0
--- /dev/null
+++ b/test-files/test_issue_effect_tag_undefined.ts
@@ -0,0 +1,85 @@
+// Issue #894: effect's Schema.ts crashed during module init with
+// `TypeError: Cannot read properties of undefined (reading '_tag')`.
+//
+// Root cause: a class returned from a factory function with a static
+// computed-Symbol-key field (`static [TypeId] = variance`) lost that
+// field after the factory call. The pre-fix codegen emitted the
+// `js_class_register_static_symbol` registration once at module-init
+// time, BEFORE the module's top-level lets had been assigned. Both
+// the key (`Symbol.for("…")`) and the value (`variance = {…}`) were
+// read from their then-uninitialised module globals — registration
+// recorded `(class_id, 0, 0)`, which `class_static_symbol_lookup`
+// silently couldn't match against the real key at call-time.
+//
+// Effect's `function make(ast) { return class { static [TypeId] =
+// variance } }` factory is the canonical case — the class is returned
+// from `make()` and used as a class-extends parent throughout Schema.ts.
+// `isSchema(C) = hasProperty(C, TypeId) && isObject(C[TypeId])` then
+// returned false on the freshly-returned class. Effect's `dual`
+// dispatch fell to the curried path, downstream `class extends
+// transform(...)` etc. unwound through unexpected shapes, and a
+// `make()` call eventually received `undefined` as its `ast` argument,
+// producing the `_tag` TypeError.
+//
+// The fix has two parts:
+//
+//  1. Move the per-class static-field initialisation from
+//     `init_static_fields` (pre-user-init) to a new
+//     `init_static_fields_late` (post-user-init). This handles
+//     TOP-LEVEL classes — their static-field globals see populated
+//     module lets when the late phase emits the store.
+//
+//  2. For class EXPRESSIONS returned from factory functions, sequence
+//     a new `Expr::RegisterClassStaticSymbol` in front of the
+//     `Expr::ClassRef` so each factory invocation re-emits the
+//     `js_class_register_static_symbol(class_id, key, value)` with
+//     CURRENT values of the captured/module-level free variables.
+//
+// The standalone shape below mirrors effect's `make()` factory.
+//
+// Note: the full effect smoke (`import { Effect } from "effect";
+// console.log(typeof Effect.succeed)`) is still blocked downstream
+// on (a) `arguments.length` reading 0 inside FnExpr closures returned
+// from another function (perry's synthetic `...arguments` rest param
+// only captures TRAILING args, not all args — so `function(a, b) {
+// arguments.length }` called with two args sees `arguments.length ===
+// 0`), and (b) static methods on classes returned from a factory not
+// being routable via dynamic property access (`(make()).pipe` reads
+// `undefined`). Both are separate gaps to file as follow-ups.
+
+const TypeId: unique symbol = Symbol.for("perry/test/issue_894") as any;
+
+const variance = {
+  _A: (x: any) => x,
+  _I: (x: any) => x,
+};
+
+function makeSchemaClass(ast: any) {
+  return class SchemaClass {
+    static ast = ast;
+    static [TypeId] = variance;
+  };
+}
+
+const isObject = (x: any) =>
+  (typeof x === "object" && x !== null) || typeof x === "function";
+
+const hasProperty = (u: any, prop: any): boolean =>
+  isObject(u) && (prop in u);
+
+const isSchemaLike = (u: any) =>
+  hasProperty(u, TypeId) && isObject((u as any)[TypeId]);
+
+const FakeAst1 = { _tag: "Alpha" };
+const A = makeSchemaClass(FakeAst1);
+
+console.log("typeof A:", typeof A);
+console.log("TypeId in A:", TypeId in A);
+console.log("A[TypeId] is object:", isObject((A as any)[TypeId]));
+console.log("isSchemaLike(A):", isSchemaLike(A));
+
+// Each factory invocation must re-register so a SECOND call with a
+// different ast still passes the same isSchema check.
+const FakeAst2 = { _tag: "Beta" };
+const B = makeSchemaClass(FakeAst2);
+console.log("isSchemaLike(B):", isSchemaLike(B));