diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 7bbcfba40b..aa7f6ef371 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1036,8 +1036,25 @@ jobs:
             # (e.g. functional_batch2_regressions) link the prebuilt archive
             # directly and fail with "Could not find libperry_runtime.a" if the
             # cached staticlib was invalidated. Build them explicitly.
+            # #8479: build these with `--release`. The `panic` strategy is a
+            # PROFILE-level setting, and only `release`/`dist`/`perry-dev` set
+            # `panic = "abort"` — a bare `cargo build` produces a DEBUG,
+            # `panic = "unwind"` runtime. Under `panic = "unwind"` rustc plants
+            # an RFC-2945 abort guard in every `extern "C"` helper, which a JS
+            # throw crossing that helper trips ("panic in a function that
+            # cannot unwind"). So the child binaries were linking a runtime
+            # whose unwind semantics are the OPPOSITE of what Perry ships, and
+            # the two throw-transport canaries could not both pass: #8416
+            # papered over it with `extern "C-unwind"` (correct for the debug
+            # runtime, WRONG for the shipped one), #8464 generalised that and
+            # cost +20 gap crashes, and #8480 added more. Verified: against a
+            # `panic = "abort"` runtime, with those conversions removed, BOTH
+            # `tier1_every_ffi_type_against_test_dylib` and
+            # `function_apply_with_runtime_args_defers_to_a_located_aot_error`
+            # pass.
             if printf '%s\n' "$scope" | grep -qE '^(perry|perry-stdlib)$'; then
-              cargo build -p perry-runtime -p perry-stdlib -p perry-runtime-static -p perry-stdlib-static
+              cargo build --release -p perry-runtime -p perry-stdlib -p perry-runtime-static -p perry-stdlib-static
+              export PERRY_RUNTIME_DIR="$PWD/target/release"
             fi
             find target/debug/deps -maxdepth 1 -type f -perm -111 ! -name '*.so' -delete
             # Large perry / perry-stdlib integration-test binaries: serialize
@@ -1274,9 +1291,15 @@ jobs:
           # libperry_{runtime,stdlib}.a don't exist unless built explicitly —
           # and the suites that compile with PERRY_NO_AUTO_OPTIMIZE=1 link them
           # directly ("Could not find libperry_runtime.a" otherwise).
+          # #8479: `--release` so the child links a `panic = "abort"` runtime,
+          # matching what Perry ships. A bare `cargo build` yields a DEBUG,
+          # `panic = "unwind"` runtime whose `extern "C"` helpers carry
+          # RFC-2945 abort guards that a JS throw trips — the opposite of the
+          # shipped semantics. See the longer note in `cargo-test`.
           if printf '%s\n' "$SUITES" | grep -qE '^(perry|perry-stdlib) '; then
-            cargo build -p perry-runtime -p perry-stdlib \
+            cargo build --release -p perry-runtime -p perry-stdlib \
               -p perry-runtime-static -p perry-stdlib-static
+            export PERRY_RUNTIME_DIR="$PWD/target/release"
           fi
 
           status=0
diff --git a/changelog.d/8480-ffi-thunk-unwind.md b/changelog.d/8480-ffi-thunk-unwind.md
deleted file mode 100644
index 3317657ad9..0000000000
--- a/changelog.d/8480-ffi-thunk-unwind.md
+++ /dev/null
@@ -1 +0,0 @@
-fix(ffi): `bun:ffi`'s per-arity symbol thunks and `close_thunk` are `extern "C-unwind"` (#8479). They call `invoke_from_closure`, which throws the documented "symbol … was called after close()" error; under plain `extern "C"` that unwind hit Rust's abort-on-unwind shim inside the thunk, so a use-after-close aborted the process on Linux instead of throwing — `tier1_every_ffi_type_against_test_dylib` stayed red after #8464, which had converted only the closure-dispatch callers. A call through an `extern "C-unwind"` pointer does not remove the callee's own nounwind guard.
diff --git a/changelog.d/8485-remove-c-unwind-guards.md b/changelog.d/8485-remove-c-unwind-guards.md
new file mode 100644
index 0000000000..538bda16a3
--- /dev/null
+++ b/changelog.d/8485-remove-c-unwind-guards.md
@@ -0,0 +1 @@
+fix(runtime): remove the `extern "C-unwind"` guards from the JS throw path (#8479). The runtime is built `panic=abort` and a JS throw travels as a raw Itanium `_Unwind_Exception` that must step *through* runtime frames untouched — the workspace `Cargo.toml` states the requirement outright ("no RFC-2945 abort-on-unwind guards … which a JS throw crossing a helper frame would trip"). Marking a pass-through frame `extern "C-unwind"` in a `panic=abort` crate does not enable unwinding; it makes rustc wrap the call in an abort-on-unwind landing pad, which is that exact guard. #8416 planted the first two (`js_closure_call1`, `js_native_call_value`) and broke `tier1_every_ffi_type_against_test_dylib`; #8480 planted another on the same FFI path; #8464 planted ~40 more and cost +20 gap crashes plus a red `gc-stress` before being reverted in #8484. All four pass-through conversions are back to `extern "C"`; throw *originators* (`js_throw` and friends, which diverge) are untouched.
diff --git a/changelog.d/8491-test-runtime-panic-strategy.md b/changelog.d/8491-test-runtime-panic-strategy.md
new file mode 100644
index 0000000000..4f51b11c9c
--- /dev/null
+++ b/changelog.d/8491-test-runtime-panic-strategy.md
@@ -0,0 +1 @@
+fix(ci): `cargo-test` and `e2e-scoped` now build the runtime archives with `--release`, so compiled test binaries link a `panic = "abort"` runtime like the one Perry ships (#8479). `panic` is a profile-level setting and only `release`/`dist`/`perry-dev` set `abort`; a bare `cargo build` produced a debug, `panic = "unwind"` runtime whose `extern "C"` helpers carry RFC-2945 abort guards that a JS throw trips. The test environment therefore had the *opposite* unwind semantics from production, which is why the two throw-transport canaries could never both pass and why #8416, #8464 and #8480 each fixed one by breaking the other. Paired with removing those `extern "C-unwind"` conversions (#8488): against a `panic = "abort"` runtime, both `tier1_every_ffi_type_against_test_dylib` and `function_apply_with_runtime_args_defers_to_a_located_aot_error` pass.
diff --git a/changelog.d/8492-function-apply-release-runtime.md b/changelog.d/8492-function-apply-release-runtime.md
new file mode 100644
index 0000000000..1d93f59750
--- /dev/null
+++ b/changelog.d/8492-function-apply-release-runtime.md
@@ -0,0 +1 @@
+fix(test): `function_apply_dynamic_args_eval_surface` builds and links a `--release` runtime archive (#8479). It hardcoded `target/debug` and passed it via `PERRY_RUNTIME_DIR`, so it always linked a `panic = "unwind"` runtime — a configuration Perry never ships — where rustc plants an RFC-2945 abort guard in every `extern "C"` helper and a JS throw crossing one aborts. That made this test and `bun_ffi_stage1`'s use-after-close case mutually unsatisfiable and drove three successive "fixes" (#8416, #8464, #8480) that each repaired one by breaking the other.
diff --git a/crates/perry-runtime/src/bun_ffi/dlopen.rs b/crates/perry-runtime/src/bun_ffi/dlopen.rs
index c6eec971e6..4eaa9b87c7 100644
--- a/crates/perry-runtime/src/bun_ffi/dlopen.rs
+++ b/crates/perry-runtime/src/bun_ffi/dlopen.rs
@@ -4,7 +4,7 @@
 //! (`LIBS` / `SYMS`); a symbol's JS call stub is a runtime closure whose
 //! single capture is its `SYMS` index, so the shared per-arity thunks
 //! (`sym_thunk_0..=16`) stay signature-compatible with the closure call
-//! ABI (`extern "C-unwind" fn(*const ClosureHeader, f64 × arity) -> f64`,
+//! ABI (`extern "C" fn(*const ClosureHeader, f64 × arity) -> f64`,
 //! arity-padded by `closure/dispatch` via `js_register_closure_arity`).
 //!
 //! `close()` calls `dlclose` and poisons the library's symbols: later
@@ -173,15 +173,7 @@ unsafe fn invoke_from_closure(closure: *const ClosureHeader, js_args: &[f64]) ->
 
 macro_rules! sym_thunk {
     ($name:ident $(, $a:ident)*) => {
-        // #8478: `C-unwind`, NOT `C`. `invoke_from_closure` throws a JS
-        // error for a symbol called after `close()` (and for an unknown
-        // stub). Under plain `extern "C"` that unwind hits Rust's
-        // abort-on-unwind shim inside the thunk itself — "panic in a
-        // function that cannot unwind" — so the documented use-after-close
-        // behaviour aborted the process on Linux instead of throwing.
-        // #8464 made the closure-dispatch CALLERS unwind-capable; these
-        // thunks are the CALLEES it could not see.
-        extern "C-unwind" fn $name(closure: *const ClosureHeader $(, $a: f64)*) -> f64 {
+        extern "C" fn $name(closure: *const ClosureHeader $(, $a: f64)*) -> f64 {
             let args = [$($a),*];
             unsafe { invoke_from_closure(closure, &args) }
         }
@@ -308,10 +300,7 @@ fn sym_thunk_for(arity: usize) -> *const u8 {
     }
 }
 
-// #8478: `C-unwind` for the same reason as the symbol thunks — this body
-// takes a `Mutex` whose `unwrap()` panics on poison, and a panic crossing a
-// plain `extern "C"` frame aborts rather than propagating.
-extern "C-unwind" fn close_thunk(closure: *const ClosureHeader) -> f64 {
+extern "C" fn close_thunk(closure: *const ClosureHeader) -> f64 {
     let lib_index = crate::closure::js_closure_get_capture_bits(closure, 0) as usize;
     let mut libs = LIBS.lock().unwrap();
     if let Some(rec) = libs.get_mut(lib_index) {
diff --git a/crates/perry-runtime/src/closure/dispatch/calln.rs b/crates/perry-runtime/src/closure/dispatch/calln.rs
index 22a50b8f6d..6defa4b45f 100644
--- a/crates/perry-runtime/src/closure/dispatch/calln.rs
+++ b/crates/perry-runtime/src/closure/dispatch/calln.rs
@@ -37,7 +37,16 @@ pub extern "C" fn js_closure_call0(closure: *const ClosureHeader) -> f64 {
 #[no_mangle]
 // The one-argument value-call path can run arbitrary generated code and must
 // let a JS exception unwind to the generated caller's catch landing pad.
-pub extern "C-unwind" fn js_closure_call1(closure: *const ClosureHeader, arg0: f64) -> f64 {
+// #8479: NOT `C-unwind`. The runtime is built `panic=abort` and JS throws
+// travel as a raw Itanium `_Unwind_Exception` that must step THROUGH these
+// frames untouched (see `crate::eh` and the panic=abort rationale in the
+// workspace Cargo.toml). Marking a frame `extern "C-unwind"` in a
+// panic=abort crate does not enable that — it makes rustc wrap the call in
+// an abort-on-unwind landing pad, which is exactly the RFC-2945 guard a JS
+// throw trips ("panic in a function that cannot unwind"). #8416 introduced
+// the first two such guards here; #8464 added ~40 more and measurably
+// regressed main (+20 gap crashes, gc-stress) before being reverted.
+pub extern "C" fn js_closure_call1(closure: *const ClosureHeader, arg0: f64) -> f64 {
     let func_ptr = get_valid_func_ptr(closure);
     if func_ptr.is_null() {
         return dispatch_proxy_callee_or_throw(closure, &[arg0]);
@@ -52,7 +61,7 @@ pub extern "C-unwind" fn js_closure_call1(closure: *const ClosureHeader, arg0: f
             dispatch_with_arity(closure, func_ptr, &[arg0], declared)
         },
         _ => {
-            let func: extern "C-unwind" fn(*const ClosureHeader, f64) -> f64 =
+            let func: extern "C" fn(*const ClosureHeader, f64) -> f64 =
                 unsafe { std::mem::transmute(func_ptr) };
             func(closure, arg0)
         }
@@ -63,11 +72,7 @@ pub extern "C-unwind" fn js_closure_call1(closure: *const ClosureHeader, arg0: f
 #[no_mangle]
 // A dynamically-dispatched closure can throw into a generated caller's catch
 // landing pad; this bridge is on Next's loadManifest/readFileSync path.
-pub extern "C-unwind" fn js_closure_call2(
-    closure: *const ClosureHeader,
-    arg0: f64,
-    arg1: f64,
-) -> f64 {
+pub extern "C" fn js_closure_call2(closure: *const ClosureHeader, arg0: f64, arg1: f64) -> f64 {
     let func_ptr = get_valid_func_ptr(closure);
     if func_ptr.is_null() {
         return dispatch_proxy_callee_or_throw(closure, &[arg0, arg1]);
diff --git a/crates/perry-runtime/src/closure/dispatch/value_call.rs b/crates/perry-runtime/src/closure/dispatch/value_call.rs
index 111450546b..30f6cc17ee 100644
--- a/crates/perry-runtime/src/closure/dispatch/value_call.rs
+++ b/crates/perry-runtime/src/closure/dispatch/value_call.rs
@@ -18,7 +18,16 @@ use super::*;
 // landing pad. Keep this value-call bridge unwind-capable just like
 // `js_native_call_method`; otherwise debug/static runtime builds install an
 // abort-on-unwind guard here and Linux aborts before the landing pad is reached.
-pub unsafe extern "C-unwind" fn js_native_call_value(
+// #8479: NOT `C-unwind`. The runtime is built `panic=abort` and JS throws
+// travel as a raw Itanium `_Unwind_Exception` that must step THROUGH these
+// frames untouched (see `crate::eh` and the panic=abort rationale in the
+// workspace Cargo.toml). Marking a frame `extern "C-unwind"` in a
+// panic=abort crate does not enable that — it makes rustc wrap the call in
+// an abort-on-unwind landing pad, which is exactly the RFC-2945 guard a JS
+// throw trips ("panic in a function that cannot unwind"). #8416 introduced
+// the first two such guards here; #8464 added ~40 more and measurably
+// regressed main (+20 gap crashes, gc-stress) before being reverted.
+pub unsafe extern "C" fn js_native_call_value(
     func_value: f64,
     args_ptr: *const f64,
     args_len: usize,
diff --git a/crates/perry/tests/bun_ffi_stage1.rs b/crates/perry/tests/bun_ffi_stage1.rs
index 489145985b..f1d047f769 100644
--- a/crates/perry/tests/bun_ffi_stage1.rs
+++ b/crates/perry/tests/bun_ffi_stage1.rs
@@ -332,6 +332,15 @@ console.log("closed-throws:", closedError.includes("close()"));
 console.log("TIER1-DONE");
 "#;
 
+/// #8479: this test is the canary for the JS-throw transport. Its
+/// use-after-close case throws from inside an FFI symbol stub, so the throw
+/// must cross the runtime's dispatch frames. The runtime is `panic=abort`
+/// and that throw is a raw Itanium unwind that has to pass THROUGH those
+/// frames — so any `extern "C-unwind"` on a pass-through frame installs an
+/// RFC-2945 abort guard and turns this into "panic in a function that cannot
+/// unwind" (Linux only; macOS never reproduces it). Keep this file in the
+/// diff of any change to that path so `e2e-scoped` actually runs the suite:
+/// the job SKIPS silently and reports green when nothing in scope changed.
 #[test]
 fn tier1_every_ffi_type_against_test_dylib() {
     let dir = tempfile::tempdir().expect("tempdir");
diff --git a/crates/perry/tests/function_apply_dynamic_args_eval_surface.rs b/crates/perry/tests/function_apply_dynamic_args_eval_surface.rs
index a92c0ef927..f08ca5589c 100644
--- a/crates/perry/tests/function_apply_dynamic_args_eval_surface.rs
+++ b/crates/perry/tests/function_apply_dynamic_args_eval_surface.rs
@@ -14,6 +14,14 @@
 //!
 //! Literal-source forms must keep working: those are const-folded and compiled AOT.
 
+//! #8479: this suite is the counterpart canary to `bun_ffi_stage1`. #8416 made
+//! the deferred error here survive on Linux by marking `js_closure_call1` /
+//! `js_native_call_value` `extern "C-unwind"` — which, in a `panic=abort`
+//! runtime whose JS throws are raw Itanium unwinds, installs an RFC-2945
+//! abort guard on a frame the throw must pass THROUGH, and that is what broke
+//! `tier1_every_ffi_type_against_test_dylib`. Those conversions were undone;
+//! keep this file in the diff of any change to that path so `e2e-scoped`
+//! actually runs the suite (it skips silently, and reports green, otherwise).
 use std::path::PathBuf;
 use std::process::Command;
 use std::sync::Once;
@@ -29,11 +37,19 @@ fn workspace_root() -> PathBuf {
         .expect("canonicalize workspace root")
 }
 
-fn target_debug_dir() -> PathBuf {
+/// #8479: `release`, not `debug`. `panic` is a PROFILE-level setting and only
+/// `release`/`dist`/`perry-dev` set `panic = "abort"`. A debug archive is
+/// `panic = "unwind"`, and under that strategy rustc plants an RFC-2945
+/// abort-on-unwind guard in every `extern "C"` helper — which a JS throw
+/// crossing that helper trips ("panic in a function that cannot unwind").
+/// Perry never ships such a runtime, so linking one here tested unwind
+/// semantics that do not exist in production and made this test and
+/// `bun_ffi_stage1`'s use-after-close case mutually unsatisfiable.
+fn target_runtime_dir() -> PathBuf {
     std::env::var_os("CARGO_TARGET_DIR")
         .map(PathBuf::from)
         .unwrap_or_else(|| workspace_root().join("target"))
-        .join("debug")
+        .join("release")
 }
 
 /// Build `libperry_{runtime,stdlib}.a` once so the compiled binaries can link.
@@ -47,6 +63,9 @@ fn ensure_runtime_archive() {
         let build = Command::new(cargo)
             .current_dir(workspace_root())
             .arg("build")
+            // #8479: must match `target_runtime_dir()` — a debug archive has
+            // the wrong panic strategy (see that function's comment).
+            .arg("--release")
             .arg("-p")
             .arg("perry-runtime-static")
             .arg("-p")
@@ -64,7 +83,7 @@ fn ensure_runtime_archive() {
 
 fn runtime_dir() -> PathBuf {
     ensure_runtime_archive();
-    target_debug_dir()
+    target_runtime_dir()
 }
 
 /// Literal-source `Function` / `Function.apply` / `Function.call` are const-folded and