diff --git a/crates/prometeu-bytecode/src/abi.rs b/crates/prometeu-bytecode/src/abi.rs
index b34fecb6..2cc87242 100644
--- a/crates/prometeu-bytecode/src/abi.rs
+++ b/crates/prometeu-bytecode/src/abi.rs
@@ -130,4 +130,21 @@ Operand Sizes:
         
         assert_eq!(current_info.trim(), abi_info.trim());
     }
+
+    #[test]
+    fn operand_size_matches_spec_for_all_opcodes() {
+        // Scan a generous numeric range and validate every decodable opcode.
+        // This ensures that abi::operand_size (if kept) never diverges from the
+        // canonical spec (OpcodeSpec::imm_bytes).
+        for raw in 0u16..=1023u16 {
+            if let Ok(op) = OpCode::try_from(raw) {
+                assert_eq!(
+                    operand_size(op),
+                    op.spec().imm_bytes as usize,
+                    "operand_size must match spec for {:?}",
+                    op
+                );
+            }
+        }
+    }
 }