diff --git a/changelog.d/headers-proxy-record-init.md b/changelog.d/headers-proxy-record-init.md
new file mode 100644
index 0000000000..5922660182
--- /dev/null
+++ b/changelog.d/headers-proxy-record-init.md
@@ -0,0 +1 @@
+Accept a Proxy as a `Headers` record init. `new Headers(new Proxy({ "x-a": "1" }, {}))` raised "Headers constructor: init is not iterable": the record path required a plain heap object, and a proxy value is a proxy id rather than one, so neither the iterable nor the record branch applied. The constructor now reads a proxied init's own string keys and their values through the proxy's `ownKeys` and `get` traps, matching how the spec reads a record init through the object's internal methods. Plain objects, arrays, maps, sets and string inits are unchanged. This unblocks OpenCode's request path, where the AI SDK hands the fetch layer a proxied header record (#10107).
diff --git a/crates/perry-stdlib/src/fetch/headers.rs b/crates/perry-stdlib/src/fetch/headers.rs
index 792ed67c43..a9b6fad78d 100644
--- a/crates/perry-stdlib/src/fetch/headers.rs
+++ b/crates/perry-stdlib/src/fetch/headers.rs
@@ -82,6 +82,38 @@ fn has_sync_iterator(value: f64) -> bool {
     raw != 0 && perry_runtime::closure::is_closure_ptr(raw as usize)
 }
 
+/// A short description of a rejected `Headers` init, so the thrown message
+/// names what was passed instead of only saying it is not iterable. Kept cheap:
+/// it runs only on the error path.
+fn describe_headers_init(value: f64) -> String {
+    let jsval = JSValue::from_bits(value.to_bits());
+    if jsval.is_any_string() {
+        return "string".to_string();
+    }
+    if perry_runtime::proxy::js_proxy_is_proxy(value) != 0 {
+        return "Proxy".to_string();
+    }
+    if perry_runtime::js_array_is_array(value).to_bits() == TAG_TRUE {
+        return "array".to_string();
+    }
+    let raw = perry_runtime::js_nanbox_get_pointer(value);
+    if raw == 0 {
+        return format!("{:#018x}", value.to_bits());
+    }
+    let addr = raw as usize;
+    if perry_runtime::map::is_registered_map(addr) {
+        return "Map".to_string();
+    }
+    if perry_runtime::set::is_registered_set(addr) {
+        return "Set".to_string();
+    }
+    match gc_type_for_raw_ptr(raw) {
+        Some(t) if t == perry_runtime::gc::GC_TYPE_OBJECT => "object".to_string(),
+        Some(t) => format!("gc type {t}"),
+        None => format!("non-heap {:#018x}", value.to_bits()),
+    }
+}
+
 fn is_headers_init_iterable(value: f64) -> bool {
     let jsval = JSValue::from_bits(value.to_bits());
     if jsval.is_any_string() {
@@ -121,6 +153,16 @@ fn read_headers_record_entries(
     if has_sync_iterator(value) {
         return None;
     }
+    // A Proxy wrapping a record (`new Headers(new Proxy(headers, {}))`) is a
+    // valid record init: the spec reads the init's own keys and values through
+    // the object's internal methods, which for a Proxy means its `ownKeys` and
+    // `get` traps. The pointer below is a proxy id, not a `GC_TYPE_OBJECT`
+    // heap object, so without this branch the record path bailed and the
+    // constructor reported "init is not iterable" for an ordinary header
+    // object (OpenCode's request path, tracker #10107).
+    if perry_runtime::proxy::js_proxy_is_proxy(value) != 0 {
+        return unsafe { read_proxy_record_entries(value, scope) };
+    }
     let raw = perry_runtime::js_nanbox_get_pointer(value);
     if gc_type_for_raw_ptr(raw) != Some(perry_runtime::gc::GC_TYPE_OBJECT) {
         return None;
@@ -155,18 +197,62 @@ fn read_headers_record_entries(
     }
 }
 
+/// Own string-keyed properties of a Proxy init, read through its traps.
+/// Symbol keys are skipped (a header name is always a string). Enumerability
+/// is not re-queried per key: `ownKeys` on a plain wrapping Proxy already
+/// reports the target's own keys, and a trap that hides a key omits it there.
+unsafe fn read_proxy_record_entries(
+    value: f64,
+    scope: &perry_runtime::gc::RuntimeHandleScope,
+) -> Option<Vec<(String, String)>> {
+    let keys_value = perry_runtime::proxy::js_proxy_own_keys(value);
+    let keys_handle = scope.root_nanbox_f64(keys_value);
+    let proxy_handle = scope.root_nanbox_f64(value);
+    let keys_raw = perry_runtime::js_nanbox_get_pointer(keys_handle.get_nanbox_f64());
+    if keys_raw == 0 {
+        return Some(Vec::new());
+    }
+    let len = perry_runtime::js_array_length(keys_raw as *const perry_runtime::ArrayHeader);
+    let mut entries = Vec::with_capacity(len as usize);
+    for i in 0..len {
+        let keys_now = perry_runtime::js_nanbox_get_pointer(keys_handle.get_nanbox_f64());
+        let key_value = perry_runtime::array::js_array_get_f64(
+            keys_now as *const perry_runtime::ArrayHeader,
+            i,
+        );
+        if !JSValue::from_bits(key_value.to_bits()).is_any_string() {
+            continue;
+        }
+        let key_ptr = perry_runtime::builtins::js_string_coerce(key_value);
+        if key_ptr.is_null() {
+            continue;
+        }
+        let key = string_from_header(key_ptr as *const StringHeader).unwrap_or_default();
+        let val_value =
+            perry_runtime::proxy::js_proxy_get(proxy_handle.get_nanbox_f64(), key_value);
+        entries.push((key, header_init_string(val_value)));
+    }
+    Some(entries)
+}
+
 unsafe fn materialize_headers_init_iterable(
     value: f64,
     scope: &perry_runtime::gc::RuntimeHandleScope,
 ) -> *const perry_runtime::ArrayHeader {
     if !is_headers_init_iterable(value) {
-        headers_init_type_error("Headers constructor: init is not iterable");
+        headers_init_type_error(&format!(
+            "Headers constructor: init is not iterable (received {})",
+            describe_headers_init(value)
+        ));
     }
     let arr_value = perry_runtime::array::js_for_of_to_array(value);
     let arr_handle = scope.root_nanbox_f64(arr_value);
     let raw = perry_runtime::js_nanbox_get_pointer(arr_handle.get_nanbox_f64());
     if raw == 0 {
-        headers_init_type_error("Headers constructor: init is not iterable");
+        headers_init_type_error(&format!(
+            "Headers constructor: init is not iterable (received {})",
+            describe_headers_init(value)
+        ));
     }
     raw as *const perry_runtime::ArrayHeader
 }
@@ -245,12 +331,20 @@ pub unsafe extern "C" fn js_headers_init_from_value(handle: f64, init: f64) -> f
         return f64::from_bits(TAG_UNDEFINED);
     }
 
+    // A Proxy value is not a Headers handle: its NaN-box would otherwise be
+    // masked into a registry id and could alias a live Headers entry, silently
+    // copying the wrong (or no) headers. Route it to the record path below.
+    let is_proxy_init = perry_runtime::proxy::js_proxy_is_proxy(init) != 0;
     let source_id = handle_id(init);
-    let cloned = HEADERS_REGISTRY
-        .lock()
-        .unwrap()
-        .get(&source_id)
-        .map(|store| store.entries.clone());
+    let cloned = if is_proxy_init {
+        None
+    } else {
+        HEADERS_REGISTRY
+            .lock()
+            .unwrap()
+            .get(&source_id)
+            .map(|store| store.entries.clone())
+    };
     if let Some(entries) = cloned {
         append_header_entries(target_id, entries);
         return f64::from_bits(TAG_UNDEFINED);
diff --git a/crates/perry/tests/headers_proxy_record_init.rs b/crates/perry/tests/headers_proxy_record_init.rs
new file mode 100644
index 0000000000..4706deb0a7
--- /dev/null
+++ b/crates/perry/tests/headers_proxy_record_init.rs
@@ -0,0 +1,100 @@
+//! `new Headers(init)` must accept a Proxy wrapping a record, reading the init's
+//! own keys and values through the proxy's traps. perry took the record path only
+//! for plain heap objects, so a proxied header record raised
+//! "Headers constructor: init is not iterable" — OpenCode's request path hit this
+//! on every `run` (tracker #10107).
+//! Two neighbours are deliberately out of scope here: a proxy wrapping an *array*
+//! (`Array.from` over such a value segfaults, #10270) and a proxied init passed
+//! through `new Request(url, { headers })`, which takes a different path (#10274).
+
+use std::path::PathBuf;
+use std::process::Command;
+use std::sync::Once;
+
+fn perry_bin() -> PathBuf {
+    PathBuf::from(env!("CARGO_BIN_EXE_perry"))
+}
+
+fn workspace_root() -> PathBuf {
+    PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("../..")
+        .canonicalize()
+        .expect("canonicalize workspace root")
+}
+
+fn runtime_dir() -> PathBuf {
+    static BUILD_RUNTIME: Once = Once::new();
+    BUILD_RUNTIME.call_once(|| {
+        let cargo = std::env::var_os("CARGO").unwrap_or_else(|| "cargo".into());
+        let build = Command::new(cargo)
+            .current_dir(workspace_root())
+            .arg("build")
+            .arg("-p")
+            .arg("perry-runtime-static")
+            .arg("-p")
+            .arg("perry-stdlib-static")
+            .output()
+            .expect("build static runtime archives");
+        assert!(
+            build.status.success(),
+            "static runtime build failed\nstdout:\n{}\nstderr:\n{}",
+            String::from_utf8_lossy(&build.stdout),
+            String::from_utf8_lossy(&build.stderr)
+        );
+    });
+    let target = std::env::var_os("CARGO_TARGET_DIR")
+        .map(PathBuf::from)
+        .unwrap_or_else(|| workspace_root().join("target"));
+    target.join("debug")
+}
+
+const SOURCE: &str = r#"
+const t = (name: string, f: () => any) => { try { console.log(name, JSON.stringify(f())) } catch (e: any) { console.log(name, "THROW", e.message) } }
+const dump = (h: any) => { const out: string[] = []; h.forEach((v: string, k: string) => out.push(k + "=" + v)); return out.sort() }
+t("P1 plain proxy", () => dump(new Headers(new Proxy({ "x-a": "1", "x-b": "2" }, {}) as any)))
+t("P2 proxy with get trap", () => dump(new Headers(new Proxy({ "x-a": "1" }, { get: (t: any, k: any) => (typeof k === "string" && k in t ? "trapped" : (t as any)[k]) }) as any)))
+t("P3 proxy with ownKeys trap hiding a key", () => dump(new Headers(new Proxy({ "x-a": "1", "x-b": "2" }, { ownKeys: () => ["x-a"], getOwnPropertyDescriptor: () => ({ configurable: true, enumerable: true, value: "1" }) }) as any)))
+t("P4 proxy over empty object", () => dump(new Headers(new Proxy({}, {}) as any)))
+t("P6 nested proxy", () => dump(new Headers(new Proxy(new Proxy({ "x-a": "1" }, {}), {}) as any)))
+t("P8 plain object still works", () => dump(new Headers({ "x-a": "1" })))
+t("P9 array still works", () => dump(new Headers([["x-a", "1"]])))
+t("P10 map still works", () => dump(new Headers(new Map([["x-a", "1"]]) as any)))
+"#;
+
+const EXPECTED: &str = "P1 plain proxy [\"x-a=1\",\"x-b=2\"]\nP2 proxy with get trap [\"x-a=trapped\"]\nP3 proxy with ownKeys trap hiding a key [\"x-a=1\"]\nP4 proxy over empty object []\nP6 nested proxy [\"x-a=1\"]\nP8 plain object still works [\"x-a=1\"]\nP9 array still works [\"x-a=1\"]\nP10 map still works [\"x-a=1\"]\n";
+
+#[test]
+fn headers_accepts_a_proxied_record_init() {
+    let dir = tempfile::tempdir().expect("tempdir");
+    let entry = dir.path().join("main.ts");
+    let output = dir.path().join("main_bin");
+    std::fs::write(&entry, SOURCE).expect("write entry");
+    let compile = Command::new(perry_bin())
+        .current_dir(dir.path())
+        .arg("compile")
+        .arg(&entry)
+        .arg("-o")
+        .arg(&output)
+        .arg("--no-cache")
+        .env("PERRY_NO_AUTO_OPTIMIZE", "1")
+        .env("PERRY_RUNTIME_DIR", runtime_dir())
+        .output()
+        .expect("run perry compile");
+    assert!(
+        compile.status.success(),
+        "perry compile failed\nstdout:\n{}\nstderr:\n{}",
+        String::from_utf8_lossy(&compile.stdout),
+        String::from_utf8_lossy(&compile.stderr)
+    );
+    let run = Command::new(&output)
+        .current_dir(dir.path())
+        .output()
+        .expect("run compiled binary");
+    assert!(
+        run.status.success(),
+        "compiled binary failed\nstdout:\n{}\nstderr:\n{}",
+        String::from_utf8_lossy(&run.stdout),
+        String::from_utf8_lossy(&run.stderr)
+    );
+    assert_eq!(String::from_utf8_lossy(&run.stdout), EXPECTED);
+}