youknowone · Oct 10, 2026 · Oct 10, 2026 · chatgpt-codex-connector · Oct 10, 2026
diff --git a/crates/vm/src/builtins/dict.rs b/crates/vm/src/builtins/dict.rs
@@ -136,6 +136,10 @@ impl PyDict {
         self.entries.items()
     }
 
+    pub(crate) fn items_with_hashes_vec(&self) -> Vec<(PyObjectRef, PyObjectRef, PyHash)> {
+        self.entries.items_with_hashes()
+    }
+
     fn merge_object_with_override(
         &self,
         other: PyObjectRef,

diff --git a/crates/vm/src/dict_inner.rs b/crates/vm/src/dict_inner.rs
@@ -581,7 +581,8 @@ impl<T: Clone> Dict<T> {
     /// Store a key.
     ///
     /// `hash` must be computed for `key` or read from [`Self::keys_with_hashes`]
-    /// or [`Self::next_entry_with_hash`] on a container holding this same key.
+    /// or [`Self::items_with_hashes`] or [`Self::next_entry_with_hash`] on a
+    /// container holding this same key.
     /// A wrong hash lands the entry in a bucket no lookup probes, silently
     /// losing the key.
     pub(crate) fn insert<K>(
@@ -1182,6 +1183,14 @@ impl<T: Clone> Dict<T> {
             .collect()
     }
 
+    pub(crate) fn items_with_hashes(&self) -> Vec<(PyObjectRef, T, HashValue)> {
+        self.read()
+            .entries
+            .iter()
+            .filter_map(|v| v.as_ref().map(|v| (v.key.clone(), v.value.clone(), v.hash)))
+            .collect()
+    }
+
     /// Fold stored hashes under the read lock; the callback must not run Python.
     pub(crate) fn fold_hashes<Acc, Fold>(&self, init: Acc, f: Fold) -> Acc
     where

diff --git a/crates/vm/src/frame.rs b/crates/vm/src/frame.rs
@@ -4623,19 +4623,19 @@ impl ExecutingFrame<'_> {
                     let src_dict = source
                         .downcast_ref::<PyDict>()
                         .expect("exact dict must have a PyDict payload");
-                    // Snapshot under a single read lock so a mutation of `source`
-                    // triggered by `dict.set_item` (e.g. via a target subclass, or
-                    // aliasing) can't be observed mid-iteration.
-                    for (key, value) in src_dict.items_vec() {
-                        if dict.contains_key(&*key, vm) {
+                    // Preserve stored hashes: copying an exact dict must not call
+                    // a key's __hash__ before the callable receives its arguments.
+                    // Snapshot under one lock before any equality callbacks run.
+                    for (key, value, hash) in src_dict.items_with_hashes_vec() {
+                        if dict.contains_known_hash(&key, hash, vm)? {
                             let key_str = key.str(vm)?;
                             return Err(vm.new_type_error(format!(
                                 "{} got multiple values for keyword argument '{}'",
                                 func_str,
                                 key_str.as_wtf8()
                             )));
                         }
-                        dict.set_item(&*key, value, vm)?;
+                        dict.set_item_known_hash(&key, hash, value, vm)?;
                     }
                     return Ok(None);
                 } else {

diff --git a/extra_tests/snippets/syntax_function_args.py b/extra_tests/snippets/syntax_function_args.py
@@ -213,3 +213,50 @@ def f(a, b, /, c, d, *, e, f):
     f(1,2,3,4,5,f=6)
 with assert_raises(TypeError):
     f(1,2,3,4,5,6)
+
+
+def test_keyword_dict_stored_hashes():
+    class Keyword(str):
+        def __hash__(self):
+            assert not getattr(self, "hashed", False), "keyword was rehashed"
+            self.hashed = True
+            return str.__hash__(self)
+
+    def accept(*, value):
+        return value
+
+    source = {Keyword("value"): 42}
+    assert accept(**source) == 42
+    with assert_raises(TypeError) as raised:
+        accept(value=1, **source)
+    assert str(raised.exception).endswith(
+        "got multiple values for keyword argument 'value'"
+    )
+
+    class NonString:
+        def __hash__(self):
+            assert not getattr(self, "hashed", False), "non-string key was rehashed"
+            self.hashed = True
+            return 0
+
+    source = {NonString(): 42}
+    with assert_raises(TypeError) as raised:
+        accept(**source)
+    assert str(raised.exception) == "keywords must be strings"
+
+    failure = RuntimeError("keyword comparison failed")
+
+    class BadEquality(str):
+        __hash__ = str.__hash__
+
+        def __eq__(self, other):
+            raise failure
+
+    left = {BadEquality("value"): 1}
+    right = {BadEquality("value"): 2}
+    with assert_raises(RuntimeError) as raised:
+        accept(**left, **right)
+    assert raised.exception is failure
+
+
+test_keyword_dict_stored_hashes()