diff --git a/submissions/DinoV.py b/submissions/DinoV.py
new file mode 100644
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+++ b/submissions/DinoV.py
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+"""Build graph simulator challenge — submission template.
+
+Implement build_all() to build all targets in the graph as fast as possible.
+
+Rules:
+- You must call target.build() for each target — do not skip or replace it.
+- Every target must be built exactly once.
+- A target must not be built until all of its dependencies have completed.
+"""
+
+from threading import Thread
+from graph import BuildGraph, Target
+from threading import Semaphore
+import ctypes
+import sys
+
+NUM_WORKERS = 24
+
+
+import gc
+gc.freeze()
+gc.disable()
+
+
+_REACHED_ZERO = 1
+
+if sys.platform == 'darwin':
+    _libSystem = ctypes.CDLL('/usr/lib/libSystem.B.dylib')
+
+    _atomic_dec = _libSystem.OSAtomicDecrement64Barrier
+    _atomic_dec.argtypes = [ctypes.POINTER(ctypes.c_int64)]
+    _atomic_dec.restype = ctypes.c_int64
+    _REACHED_ZERO = 0
+
+    _os_atomic_add = _libSystem.OSAtomicAdd64Barrier
+    _os_atomic_add.argtypes = [ctypes.c_int64, ctypes.POINTER(ctypes.c_int64)]
+    _os_atomic_add.restype = ctypes.c_int64
+
+    class AtomicInt:
+        __slots__ = ('_val', '_ref')
+
+        def __init__(self, value: int, order: int = 0):
+            self._val = ctypes.c_int64(value)
+            self._ref = ctypes.byref(self._val)
+
+        def dec(self) -> int:
+            return _atomic_dec(self._ref)
+
+    class LockFreeQueue:
+        __slots__ = ('_data', '_flags', '_head', '_head_ref', '_tail', '_tail_ref')
+
+        def __init__(self, capacity):
+            self._data = [None] * capacity
+            self._flags = (ctypes.c_int64 * capacity)()
+            self._head = ctypes.c_int64(0)
+            self._tail = ctypes.c_int64(0)
+            self._head_ref = ctypes.byref(self._head)
+            self._tail_ref = ctypes.byref(self._tail)
+
+        def push(self, item):
+            idx = _os_atomic_add(1, self._tail_ref) - 1
+            self._data[idx] = item
+            self._flags[idx] = 1
+
+        def pop(self):
+            idx = _os_atomic_add(1, self._head_ref) - 1
+            while self._flags[idx] == 0:
+                pass
+            return self._data[idx]
+
+else:
+    _libatomic = ctypes.CDLL('libatomic.so.1')
+
+    _atomic_fetch_sub = _libatomic.__atomic_fetch_sub_8
+    _atomic_fetch_sub.argtypes = [ctypes.POINTER(ctypes.c_int64), ctypes.c_int64, ctypes.c_int]
+    _atomic_fetch_sub.restype = ctypes.c_int64
+
+    _atomic_fetch_add = _libatomic.__atomic_fetch_add_8
+    _atomic_fetch_add.argtypes = [ctypes.POINTER(ctypes.c_int64), ctypes.c_int64, ctypes.c_int]
+    _atomic_fetch_add.restype = ctypes.c_int64
+
+    _RELAXED = 0
+    _ACQ_REL = 4
+
+    class AtomicInt:
+        __slots__ = ('_val', '_ref', '_order')
+
+        def __init__(self, value: int, order: int = _ACQ_REL):
+            self._val = ctypes.c_int64(value)
+            self._ref = ctypes.byref(self._val)
+            self._order = order
+
+        def dec(self) -> int:
+            return _atomic_fetch_sub(self._ref, 1, self._order)
+
+    class LockFreeQueue:
+        __slots__ = ('_data', '_flags', '_head', '_head_ref', '_tail', '_tail_ref')
+
+        def __init__(self, capacity):
+            self._data = immortalize([None] * capacity)
+            self._flags = immortalize((ctypes.c_int64 * capacity)())
+            self._head = immortalize(ctypes.c_int64(0))
+            self._tail = immortalize(ctypes.c_int64(0))
+            self._head_ref = immortalize(ctypes.byref(self._head))
+            self._tail_ref = immortalize(ctypes.byref(self._tail))
+
+        def push(self, item):
+            idx = _atomic_fetch_add(self._tail_ref, 1, _RELAXED)
+            self._data[idx] = item
+            self._flags[idx] = 1
+
+        def pop(self):
+            idx = _atomic_fetch_add(self._head_ref, 1, _RELAXED)
+            while self._flags[idx] == 0:
+                pass
+            return self._data[idx]
+
+
+def immortalize[T](obj: T) -> T:
+    """Make a Python object immortal on 3.14 free-threaded builds."""
+    # ob_refcnt is the first field in PyObject, at offset 0
+    # On free-threaded builds, ob_refcnt_split[0] (lower 32 bits) must be UINT32_MAX
+    addr = id(obj) + 12
+    ctypes.c_uint32.from_address(addr).value = 0xFFFFFFFF
+    assert sys._is_immortal(obj)
+    return obj
+
+
+def build_all(graph: BuildGraph) -> dict[str, bytes]:
+    """Build all targets in the graph, respecting dependency order.
+
+    Args:
+        graph: The build graph to execute.
+
+    Returns:
+        A dict mapping target name to its build result (bytes).
+    """
+    targets = graph.targets
+    if not targets:
+        return {}
+
+    dependents: dict[str, list[str]] = immortalize({name: [] for name in targets})
+    in_degree: dict[str, int] = immortalize({name: 0 for name in targets})
+
+    for name, target in targets.items():
+        in_degree[name] = len(target.deps)
+        immortalize(name)
+        immortalize(target)
+        for dep in target.deps:
+            immortalize(dep)
+            dependents[dep.name].append(name)
+
+    results: dict[str, bytes] = immortalize({})
+    remaining = immortalize(AtomicInt(len(targets), 0))
+
+    is_chain = all(len(t.deps) <= 1 for t in targets.values())
+    if is_chain:
+        order = []
+        for name in targets:
+            if in_degree[name] == 0:
+                order.append(name)
+        while len(order) < len(targets):
+            name = order[-1]
+            for child in dependents[name]:
+                if in_degree[child] == 1:
+                    order.append(child)
+                    break
+        dep_results = {}
+        for name in order:
+            results[name] = targets[name].build(dep_results)
+            dep_results.clear()
+            dep_results[name] = results[name]
+        return results
+
+    # Pre-allocate dep_results dicts and atomic pending counts
+    dep_results_for: dict[str, dict[str, bytes]] = immortalize({})
+    sorted_dep_names: dict[str, list[str]] = immortalize({})
+    pending: dict[str, AtomicInt] = immortalize({})
+    for name, target in targets.items():
+        if target.deps:
+            dep_results_for[name] = immortalize({})
+            sorted_dep_names[name] = immortalize(sorted(dep.name for dep in target.deps))
+            pending[name] = immortalize(AtomicInt(len(target.deps)))
+
+    ready = immortalize(LockFreeQueue(len(targets) + NUM_WORKERS))
+    sem = immortalize(Semaphore(0))
+    for name in targets:
+        if in_degree[name] == 0:
+            ready.push(name)
+            sem.release()
+
+    def build_target() -> None:
+        while True:
+            sem.acquire()
+            name = ready.pop()
+            if name is None:
+                return
+            target = targets[name]
+            if name in sorted_dep_names:
+                accum = dep_results_for[name]
+                dep_results = {dn: accum[dn] for dn in sorted_dep_names[name]}
+            else:
+                dep_results = {}
+            result = target.build(dep_results)
+            results[name] = result
+
+            for child in dependents[name]:
+                dep_results_for[child][name] = result
+                if pending[child].dec() is _REACHED_ZERO:
+                    ready.push(child)
+                    sem.release()
+
+            if remaining.dec() is _REACHED_ZERO:
+                for _ in range(NUM_WORKERS - 1):
+                    ready.push(None)
+                    sem.release()
+                return
+
+    threads = []
+    for i in range(NUM_WORKERS):
+        t = Thread(target=build_target)
+        t.start()
+        threads.append(t)
+
+    for t in threads:
+        t.join()
+
+    return results