In `@crates/vm/src/stdlib/builtins.rs`:
- Around line 144-166: The AST-only branch currently returns early when
ast::PY_COMPILE_FLAG_AST_ONLY is set without validating the rest of the flags;
update the block around flags/args.flags and ast::PY_COMPILE_FLAG_AST_ONLY to
run the same unrecognized-flag validation used in the parser branch (i.e.,
detect and reject any unsupported flag bits and raise vm.new_value_error for
invalid flags) before checking mode_str/expected_type and returning
Ok(args.source); reference the existing symbols flags, args.flags,
ast::PY_COMPILE_FLAG_AST_ONLY, mode_str and the early return to locate and
insert this validation.

In `@crates/vm/src/stdlib/ast/python.rs`:
- Around line 99-137: The defaulting logic uses a global LIST_FIELDS to decide
list-vs-none which causes Lambda.args to be set to an empty list; change the
loop that assigns defaults (the block referencing LIST_FIELDS, fields, and
zelf.set_attr) to consult the node-specific _field_types metadata instead of the
global LIST_FIELDS: for each field in &fields, look up its declared type in
self._field_types (or equivalent per-node field-type map) and only create
vm.ctx.new_list(vec![]) when that field’s declared type is a sequence/list type;
otherwise use vm.ctx.none() so fields like Lambda.args (declared as an arguments
node) are not defaulted to an empty list. Ensure you still use
vm.ctx.intern_str(field.as_str()) and set the attribute via
zelf.set_attr(vm.ctx.intern_str(...), default, vm)?.

In `@crates/vm/src/stdlib/builtins.rs`:
- Around line 148-164: The code currently compares the source AST class name
string to expected_type (using cls_name != expected_type), which rejects
subclasses; change this to map mode_str to the actual AST type class object
(e.g., the Module/Expression/Interactive/FunctionType class from the VM/ctx
types) and use fast_issubclass(args.source.class(), expected_type_class) to
validate inheritance; if fast_issubclass returns false, return the same
vm.new_type_error with a message like "expected {expected_type} node, got
{cls_name}" so subclasses are accepted while still failing on unrelated types.

In `@crates/vm/src/stdlib/ast/python.rs`:
- Around line 90-149: The body-field list detection in
crates/vm/src/stdlib/ast/python.rs incorrectly treats IfExp.body as a list;
update the conditional that computes is_list_field (which uses class_name,
field_name, and LIST_FIELDS) so the "body" branch also excludes "IfExp" (i.e.,
ensure class_name != "Lambda" && class_name != "Expression" && class_name !=
"IfExp") before choosing the default and calling zelf.set_attr.

In `@crates/vm/src/stdlib/ast/python.rs`:
- Around line 129-154: The code incorrectly uses exact class name string
comparisons (class_name == "Call", "Lambda", "Expression", "IfExp") to decide
list defaults, which misclassifies subclasses; change those comparisons to
subclass checks using vm.ctx.fast_issubclass against the canonical AST base
classes so subclasses inherit the same defaults. Specifically, in the
is_list_field logic replace checks like class_name == "Call" or class_name ==
"arguments" and the matches!(...) for "Lambda"|"Expression"|"IfExp" with calls
to vm.ctx.fast_issubclass(zelf.class(), <Call_class_obj>) etc.; obtain the base
class objects once (e.g., look up the Call, Lambda, Expression, IfExp class
objects from the VM context) and use those in fast_issubclass checks, keeping
LIST_FIELDS and the rest of the default/list logic intact and falling back to
the string-based behavior only if the type lookup fails.

In `@DEVELOPMENT.md`:
- Around line 67-69: The fenced code block contains a shell prompt character ("$
") before the command string "cargo test --workspace --exclude rustpython_wasm
--exclude rustpython-venvlauncher" which triggers markdownlint MD014; edit the
fenced block to remove the leading "$ " so it contains just the plain command
line (i.e., "cargo test --workspace --exclude rustpython_wasm --exclude
rustpython-venvlauncher") to satisfy the lint rule.