diff --git a/crates/perry-codegen/src/codegen/entry.rs b/crates/perry-codegen/src/codegen/entry.rs
index 66c881ef4e..22c6164c10 100644
--- a/crates/perry-codegen/src/codegen/entry.rs
+++ b/crates/perry-codegen/src/codegen/entry.rs
@@ -1051,11 +1051,11 @@ pub(super) fn compile_module_entry(
                 // we ret. Mirrors Node's "event loop drained → one
                 // beforeExit pass" semantics.
                 //
-                // We pass `0` as the code today: Perry doesn't yet wire
-                // `process.exitCode` into this codegen path, and the test
-                // surface in #2135 only pins the firing + the default
-                // code. Explicit `process.exit(N)` bypasses this whole
-                // block via libc::_exit.
+                // We still pass `0` to the `beforeExit` emit (the #2135 test
+                // surface only pins the firing + default code); the *process*
+                // status, by contrast, now consults `process.exitCode` at the
+                // `ret` below (#6666). Explicit `process.exit(N)` bypasses this
+                // whole block via libc::_exit.
                 ctx.current_block = exit_idx;
                 let zero_code = "0x0".to_string();
                 ctx.block()
@@ -1080,7 +1080,15 @@ pub(super) fn compile_module_entry(
                     "js_gc_release_current_thread_collection_side_allocations",
                     &[],
                 );
-                ctx.block().ret(I32, "0");
+                // #6666: natural exit (event loop drained / main returned with
+                // no explicit `process.exit()`) returns the stored
+                // `process.exitCode` (default 0), matching Node. An uncaught
+                // throw (exits 1 via `js_throw`) or an unhandled rejection
+                // (exits 1 via `js_promise_report_unhandled_rejections` above)
+                // has already terminated the process before reaching here, so
+                // those keep their own status and never fall through to this.
+                let final_exit_code = ctx.block().call(I32, "js_process_pending_exit_code", &[]);
+                ctx.block().ret(I32, &final_exit_code);
             }
         }
         let ic_globals = std::mem::take(&mut ctx.ic_globals);
diff --git a/crates/perry-codegen/src/expr/string_regex_proc.rs b/crates/perry-codegen/src/expr/string_regex_proc.rs
index ff83d36e1e..f06634240b 100644
--- a/crates/perry-codegen/src/expr/string_regex_proc.rs
+++ b/crates/perry-codegen/src/expr/string_regex_proc.rs
@@ -140,7 +140,12 @@ pub(crate) fn lower(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
             let code_val = if let Some(e) = code {
                 lower_expr(ctx, e)?
             } else {
-                "0.0".to_string()
+                // #6666: bare `process.exit()` passes `undefined` (not `0`) so
+                // the runtime falls back to the stored `process.exitCode` —
+                // matching Node, where `process.exit()` honours a previously
+                // set `process.exitCode`. An explicit `process.exit(0)` still
+                // forces 0.
+                double_literal(f64::from_bits(crate::nanbox::TAG_UNDEFINED))
             };
             ctx.block()
                 .call_void("js_process_exit", &[(DOUBLE, &code_val)]);
diff --git a/crates/perry-codegen/src/runtime_decls/strings.rs b/crates/perry-codegen/src/runtime_decls/strings.rs
index 91e5711e39..4738862a07 100644
--- a/crates/perry-codegen/src/runtime_decls/strings.rs
+++ b/crates/perry-codegen/src/runtime_decls/strings.rs
@@ -881,6 +881,9 @@ pub fn declare_phase_b_strings(module: &mut LlModule) {
     module.declare_function("js_process_emit_before_exit", VOID, &[DOUBLE]);
     module.declare_function("js_process_run_finalization_exit", VOID, &[]);
     module.declare_function("js_promise_report_unhandled_rejections", VOID, &[]);
+    // #6666: the natural-exit epilogue returns the stored `process.exitCode`
+    // (default 0) as the process status instead of a hardcoded 0.
+    module.declare_function("js_process_pending_exit_code", I32, &[]);
     module.declare_function(
         "js_gc_release_current_thread_collection_side_allocations",
         VOID,
diff --git a/crates/perry-runtime/src/process/env_misc.rs b/crates/perry-runtime/src/process/env_misc.rs
index fbce745054..749cfab09a 100644
--- a/crates/perry-runtime/src/process/env_misc.rs
+++ b/crates/perry-runtime/src/process/env_misc.rs
@@ -84,8 +84,8 @@ pub extern "C" fn js_process_add_uncaught_exception_capture_callback(callback: f
 #[no_mangle]
 pub extern "C" fn js_process_exit(code: f64) {
     // #3041 — match Node's `parseAndValidateExitCode`:
-    //   * `undefined` / `null`  → exit with the prior `process.exitCode`
-    //     (0 by default here, since the validated path never stored one).
+    //   * `undefined` / `null`  → exit with the stored `process.exitCode`
+    //     (0 when it was never set / was reset to nullish — #6666).
     //   * number                → must be a finite integer, else
     //     RangeError [ERR_OUT_OF_RANGE] ("It must be an integer").
     //   * string                → coerced with `Number()`; empty string or
@@ -93,7 +93,14 @@ pub extern "C" fn js_process_exit(code: f64) {
     //     TypeError [ERR_INVALID_ARG_TYPE], otherwise it is validated as a
     //     number (so `"2.5"` → RangeError, `"2"` → exit 2).
     //   * anything else (boolean/object/array) → TypeError.
-    let exit_code = validate_exit_code(code).unwrap_or_default();
+    //
+    // `validate_exit_code` returns `None` *only* for nullish input, so a bare
+    // `process.exit()` falls back to `process.exitCode` while an explicit arg
+    // (`process.exit(0)`) overrides it — matching Node (#6666).
+    let exit_code = match validate_exit_code(code) {
+        Some(code) => code,
+        None => js_process_pending_exit_code(),
+    };
     js_process_run_finalization_exit();
     crate::gc::js_gc_release_current_thread_collection_side_allocations();
     terminate_without_atexit(exit_code)
@@ -819,21 +826,63 @@ pub extern "C" fn js_process_exit_code_get() -> f64 {
     f64::from_bits(bits)
 }
 
-/// `process.exitCode = v`. Stores the raw NaN-boxed bits verbatim so
-/// the read round-trips byte-for-byte — Node forwards e.g. the string
-/// `"0"` as a string and only coerces when `process.exit()` runs.
+/// `process.exitCode = v`. Node validates + coerces the value *at
+/// assignment time* (`process.set [as exitCode]` → `parseAndValidateExitCode`,
+/// verified against node v26): a nullish value clears the code, a string is
+/// `Number()`-coerced, and a non-integer / NaN-string / wrong-type value
+/// throws synchronously (RangeError [ERR_OUT_OF_RANGE] or
+/// TypeError [ERR_INVALID_ARG_TYPE]). The *stored* value is the coerced
+/// integer, so `process.exitCode = "2"` reads back as the number `2`. We
+/// reuse the same `validate_exit_code` the `process.exit(code)` path uses
+/// (#1350 / #6666).
 ///
-/// Returns `value` so the call site can use it as the result of the
-/// assignment expression (JS assignment evaluates to the RHS value).
-/// That keeps the codegen path uniform with other `js_*` runtime
-/// helpers that return f64 — see `lower_call/extern_func.rs:330` for
-/// the direct-call path.
+/// Returns `value` (the *original* RHS) so the call site uses it as the
+/// assignment-expression result: JS yields the assigned value *before* the
+/// setter's coercion, so `(process.exitCode = "2") === "2"`. That also keeps
+/// the codegen path uniform with other `js_*` runtime helpers that return
+/// f64 — see `lower_call/extern_func.rs:330` for the direct-call path.
 #[no_mangle]
 pub extern "C" fn js_process_exit_code_set(value: f64) -> f64 {
-    PROCESS_EXIT_CODE.with(|c| c.set(value.to_bits()));
+    match validate_exit_code(value) {
+        Some(code) => PROCESS_EXIT_CODE.with(|c| c.set(JSValue::number(code as f64).bits())),
+        // Nullish (`process.exitCode = null` / `undefined`) resets to the
+        // unset state, so natural exit falls back to 0.
+        None => PROCESS_EXIT_CODE.with(|c| c.set(JSValue::undefined().bits())),
+    }
     value
 }
 
+/// Resolve the process's final exit status from the stored `process.exitCode`.
+///
+/// Used on **natural** termination — the event loop drained and generated
+/// `main` returned with no explicit `process.exit()` call — and as the
+/// fallback for a bare `process.exit()` (#6666). The cell holds either
+/// `undefined` (never set / reset → 0) or an already-validated integer (the
+/// setter coerced it), so no re-validation is needed here. Truncating to
+/// `i32` mirrors what `_exit()` does with the value; the OS then reduces it
+/// to the 0-255 wait-status byte, matching Node's modulo-256 (e.g.
+/// `process.exitCode = 257` → status 1, `= -1` → 255).
+#[no_mangle]
+pub extern "C" fn js_process_pending_exit_code() -> i32 {
+    let jv = JSValue::from_bits(PROCESS_EXIT_CODE.with(|c| c.get()));
+    if jv.is_undefined() || jv.is_null() {
+        return 0;
+    }
+    if jv.is_int32() {
+        jv.as_int32()
+    } else {
+        jv.as_number() as i32
+    }
+}
+
+// The natural-exit epilogue emits a call to `js_process_pending_exit_code`
+// unconditionally into generated `_main`, but the only other caller inside the
+// runtime is `js_process_exit`'s nullish fallback. Anchor the symbol so the
+// auto-optimize whole-program dead-strip cannot drop it (same guard the
+// unhandled-rejection reporter uses, #4876).
+#[used]
+static KEEP_PROCESS_PENDING_EXIT_CODE: extern "C" fn() -> i32 = js_process_pending_exit_code;
+
 /// Set an environment variable. Backs `process.env.X = v` (#1344).
 ///
 /// Reads via `js_getenv_value` already hit `std::env::var`, so writing
diff --git a/test-parity/expected-exit/exitcode-async.txt b/test-parity/expected-exit/exitcode-async.txt
new file mode 100644
index 0000000000..7f8f011eb7
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-async.txt
@@ -0,0 +1 @@
+7
diff --git a/test-parity/expected-exit/exitcode-exit-noarg.txt b/test-parity/expected-exit/exitcode-exit-noarg.txt
new file mode 100644
index 0000000000..00750edc07
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-exit-noarg.txt
@@ -0,0 +1 @@
+3
diff --git a/test-parity/expected-exit/exitcode-exit-override.txt b/test-parity/expected-exit/exitcode-exit-override.txt
new file mode 100644
index 0000000000..573541ac97
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-exit-override.txt
@@ -0,0 +1 @@
+0
diff --git a/test-parity/expected-exit/exitcode-natural.txt b/test-parity/expected-exit/exitcode-natural.txt
new file mode 100644
index 0000000000..d00491fd7e
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-natural.txt
@@ -0,0 +1 @@
+1
diff --git a/test-parity/expected-exit/exitcode-out-of-range.txt b/test-parity/expected-exit/exitcode-out-of-range.txt
new file mode 100644
index 0000000000..d00491fd7e
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-out-of-range.txt
@@ -0,0 +1 @@
+1
diff --git a/test-parity/expected-exit/exitcode-string-coerced.txt b/test-parity/expected-exit/exitcode-string-coerced.txt
new file mode 100644
index 0000000000..0cfbf08886
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-string-coerced.txt
@@ -0,0 +1 @@
+2
diff --git a/test-parity/expected-exit/exitcode-throw-precedence.txt b/test-parity/expected-exit/exitcode-throw-precedence.txt
new file mode 100644
index 0000000000..d00491fd7e
--- /dev/null
+++ b/test-parity/expected-exit/exitcode-throw-precedence.txt
@@ -0,0 +1 @@
+1
diff --git a/test-parity/expected/exitcode-async.txt b/test-parity/expected/exitcode-async.txt
new file mode 100644
index 0000000000..35740cec1a
--- /dev/null
+++ b/test-parity/expected/exitcode-async.txt
@@ -0,0 +1 @@
+scheduled
diff --git a/test-parity/expected/exitcode-exit-noarg.txt b/test-parity/expected/exitcode-exit-noarg.txt
new file mode 100644
index 0000000000..587be6b4c3
--- /dev/null
+++ b/test-parity/expected/exitcode-exit-noarg.txt
@@ -0,0 +1 @@
+x
diff --git a/test-parity/expected/exitcode-exit-override.txt b/test-parity/expected/exitcode-exit-override.txt
new file mode 100644
index 0000000000..587be6b4c3
--- /dev/null
+++ b/test-parity/expected/exitcode-exit-override.txt
@@ -0,0 +1 @@
+x
diff --git a/test-parity/expected/exitcode-natural.txt b/test-parity/expected/exitcode-natural.txt
new file mode 100644
index 0000000000..19f86f493a
--- /dev/null
+++ b/test-parity/expected/exitcode-natural.txt
@@ -0,0 +1 @@
+done
diff --git a/test-parity/expected/exitcode-out-of-range.txt b/test-parity/expected/exitcode-out-of-range.txt
new file mode 100644
index 0000000000..77c68bf180
--- /dev/null
+++ b/test-parity/expected/exitcode-out-of-range.txt
@@ -0,0 +1 @@
+stored: 257
diff --git a/test-parity/expected/exitcode-string-coerced.txt b/test-parity/expected/exitcode-string-coerced.txt
new file mode 100644
index 0000000000..4b4c0eaccc
--- /dev/null
+++ b/test-parity/expected/exitcode-string-coerced.txt
@@ -0,0 +1 @@
+type: number value: 2
diff --git a/test-parity/expected/exitcode-throw-precedence.txt b/test-parity/expected/exitcode-throw-precedence.txt
new file mode 100644
index 0000000000..b56a305192
--- /dev/null
+++ b/test-parity/expected/exitcode-throw-precedence.txt
@@ -0,0 +1,2 @@
+before throw
+Error: boom
diff --git a/test-parity/node-suite/process/exit-code/exitcode-async.ts b/test-parity/node-suite/process/exit-code/exitcode-async.ts
new file mode 100644
index 0000000000..cdb060391e
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-async.ts
@@ -0,0 +1,8 @@
+// #6666: exitCode set inside an async task that completes before the event
+// loop drains. Natural exit still honours the stored code (node rc=7).
+async function work() {
+  await Promise.resolve();
+  process.exitCode = 7;
+}
+work();
+console.log("scheduled");
diff --git a/test-parity/node-suite/process/exit-code/exitcode-exit-noarg.ts b/test-parity/node-suite/process/exit-code/exitcode-exit-noarg.ts
new file mode 100644
index 0000000000..6482959c26
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-exit-noarg.ts
@@ -0,0 +1,5 @@
+// #6666: a bare process.exit() (no argument) exits with the stored
+// process.exitCode rather than forcing 0 (node rc=3).
+process.exitCode = 3;
+console.log("x");
+process.exit();
diff --git a/test-parity/node-suite/process/exit-code/exitcode-exit-override.ts b/test-parity/node-suite/process/exit-code/exitcode-exit-override.ts
new file mode 100644
index 0000000000..bea0652a3c
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-exit-override.ts
@@ -0,0 +1,5 @@
+// #6666: an explicit process.exit(0) overrides a previously set nonzero
+// process.exitCode (node rc=0).
+process.exitCode = 3;
+console.log("x");
+process.exit(0);
diff --git a/test-parity/node-suite/process/exit-code/exitcode-natural.ts b/test-parity/node-suite/process/exit-code/exitcode-natural.ts
new file mode 100644
index 0000000000..79b0e13356
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-natural.ts
@@ -0,0 +1,5 @@
+// #6666: process.exitCode set at top level with no explicit process.exit().
+// The natural-exit epilogue (event loop drained / main returned) must return
+// it as the process status. Node exits 1 here; pre-fix Perry exited 0.
+process.exitCode = 1;
+console.log("done");
diff --git a/test-parity/node-suite/process/exit-code/exitcode-out-of-range.ts b/test-parity/node-suite/process/exit-code/exitcode-out-of-range.ts
new file mode 100644
index 0000000000..1e68db06c7
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-out-of-range.ts
@@ -0,0 +1,4 @@
+// #6666: an out-of-range integer exitCode is stored verbatim (getter returns
+// 257) but reduced modulo 256 by the OS at exit, so the process status is 1.
+process.exitCode = 257;
+console.log("stored:", process.exitCode);
diff --git a/test-parity/node-suite/process/exit-code/exitcode-string-coerced.ts b/test-parity/node-suite/process/exit-code/exitcode-string-coerced.ts
new file mode 100644
index 0000000000..04dac6b443
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-string-coerced.ts
@@ -0,0 +1,5 @@
+// #6666: node v26 coerces a string exitCode to a number at assignment time
+// (`process.exitCode = "2"` reads back as the number 2), and natural exit
+// uses the coerced integer (node rc=2).
+process.exitCode = "2";
+console.log("type:", typeof process.exitCode, "value:", process.exitCode);
diff --git a/test-parity/node-suite/process/exit-code/exitcode-throw-precedence.ts b/test-parity/node-suite/process/exit-code/exitcode-throw-precedence.ts
new file mode 100644
index 0000000000..dac50d5da4
--- /dev/null
+++ b/test-parity/node-suite/process/exit-code/exitcode-throw-precedence.ts
@@ -0,0 +1,6 @@
+// #6666: an uncaught throw exits 1 regardless of a set process.exitCode —
+// the uncaught exception takes precedence over the natural-exit code (node
+// rc=1). This path terminates before the natural-exit epilogue runs.
+process.exitCode = 3;
+console.log("before throw");
+throw new Error("boom");