From 75e6c56f9b95a3464440400f0830ff4bdb58dc23 Mon Sep 17 00:00:00 2001
From: Simon Hofmann <simon.t.hofmann@tum.de>
Date: Mon, 24 Aug 2026 13:27:27 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Initialize=20the=20Qiskit=20C=20?=
 =?UTF-8?q?API=20once?=
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Publish the vendored translation-unit-local function tables through thread-safe static initialization for nanobind 3 free-threaded bindings. Add concurrent import and export coverage.

Assisted-by: GPT-5.6 Sol via Codex
Signed-off-by: Simon Hofmann <simon.t.hofmann@tum.de>
---
 bindings/mlir/qiskit/Qiskit2_5.cpp          | 18 ++++++++++--------
 test/python/test_mlir_qiskit_translation.py | 13 +++++++++++++
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/bindings/mlir/qiskit/Qiskit2_5.cpp b/bindings/mlir/qiskit/Qiskit2_5.cpp
index c45255ee4c..c803ae7c97 100644
--- a/bindings/mlir/qiskit/Qiskit2_5.cpp
+++ b/bindings/mlir/qiskit/Qiskit2_5.cpp
@@ -1903,16 +1903,18 @@ class NativeTranslation final : public VersionedTranslation {
 std::unique_ptr<VersionedTranslation>
 MQT_QISKIT_VERSION_FACTORY() { // NOLINT(misc-use-internal-linkage): declared in
                                // the version registry.
-  if (qk_import() < 0) {
-    throwPythonError("failed to initialize the Qiskit " MQT_QISKIT_VERSION_LABEL
-                     " C API");
-  }
-  const auto version = qk_api_version();
-  const auto major = (version >> 24U) & 0xffU;
-  const auto minor = (version >> 16U) & 0xffU;
+  static const auto VERSION = []() {
+    if (qk_import() < 0) {
+      throwPythonError(
+          "failed to initialize the Qiskit " MQT_QISKIT_VERSION_LABEL " C API");
+    }
+    return qk_api_version();
+  }();
+  const auto major = (VERSION >> 24U) & 0xffU;
+  const auto minor = (VERSION >> 16U) & 0xffU;
   if (major != MQT_QISKIT_VERSION_EXPECTED_MAJOR ||
       minor != MQT_QISKIT_VERSION_EXPECTED_MINOR ||
-      (MQT_QISKIT_VERSION_EXACT_API != 0 && version != QISKIT_VERSION_HEX)) {
+      (MQT_QISKIT_VERSION_EXACT_API != 0 && VERSION != QISKIT_VERSION_HEX)) {
     throw std::runtime_error("Qiskit C API capsule version does not match the "
                              "selected " MQT_QISKIT_VERSION_LABEL
                              " translation");
diff --git a/test/python/test_mlir_qiskit_translation.py b/test/python/test_mlir_qiskit_translation.py
index d9ac7569f8..02cad0652d 100644
--- a/test/python/test_mlir_qiskit_translation.py
+++ b/test/python/test_mlir_qiskit_translation.py
@@ -14,6 +14,7 @@
 import re
 import subprocess
 import sys
+from concurrent.futures import ThreadPoolExecutor
 from typing import TYPE_CHECKING
 
 import numpy as np
@@ -105,6 +106,18 @@
 )
 
 
+def test_native_api_initialization_supports_concurrent_translation() -> None:
+    """Initialize and reuse the native Qiskit API from concurrent translations."""
+
+    def _round_trip(_: int) -> str:
+        circuit = QuantumCircuit(1)
+        circuit.x(0)
+        return QCProgram.from_qiskit(circuit).to_qiskit().data[0].operation.name
+
+    with ThreadPoolExecutor(max_workers=8) as executor:
+        assert list(executor.map(_round_trip, range(32))) == ["x"] * 32
+
+
 @pytest.mark.parametrize("gate", STANDARD_GATES, ids=lambda gate: gate.name)
 def test_standard_gates_round_trip(gate: Gate) -> None:
     """Translate each supported gate family in both directions."""