From add569d94ccab636d32c85662b5b1010a7b0e331 Mon Sep 17 00:00:00 2001
From: chenyu <chenyu@fastmail.com>
Date: Tue, 6 Jan 2026 14:17:43 -0500
Subject: [PATCH] test_unrealized_const_input_frozen (#14044)

unrealized const is not replaced in jit
---
 test/test_jit_footguns.py | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/test/test_jit_footguns.py b/test/test_jit_footguns.py
index 9b50b03a11..24c6b3a643 100644
--- a/test/test_jit_footguns.py
+++ b/test/test_jit_footguns.py
@@ -11,6 +11,7 @@ SILENT MISMATCHES (highest priority - wrong results, no error):
   output_buffer_reuse                MED    performance tradeoff, could add option or better docs
   python_constants_frozen            HARD   inherent to tracing JITs
   conditional_branches_frozen        HARD   inherent to tracing JITs
+  unrealized_const_input_frozen      HARD   unrealized const has no buffer to replace, values baked in
 
 ERRORS RAISED (lower priority - at least users know):
   non_tensor_outputs_error           EASY   raises JitError if return contains non-Tensor values
@@ -139,6 +140,17 @@ class TestJitFootguns(unittest.TestCase):
     self.assertEqual(results[2], 20)   # should be 30!
     self.assertEqual(results[3], 20)   # should be 40!
 
+  def test_unrealized_const_input_frozen(self):
+    """Unrealized const tensors have no buffer to replace, so values are baked in at capture time."""
+    @TinyJit
+    def f(a, b): return (a * b).realize()
+
+    for i in range(1, 5):
+      result = f(Tensor([1, 2, 3]).realize(), Tensor(i))  # Tensor(i) is unrealized const
+      # value is frozen at capture (i=2), so i=3,4 give wrong results
+      expected = [2, 4, 6] if i >= 2 else [i, 2*i, 3*i]
+      np.testing.assert_equal(result.numpy(), expected)  # i=3,4 should be [3,6,9], [4,8,12]!
+
   def test_conditional_branches_frozen(self):
     """Only the branch taken during capture runs thereafter."""
     @TinyJit