@@ -22,6 +22,17 @@ def add_cpu_hashes(requirements: str, cpu_requirements: str) -> str:
 
     def add_hashes(match: re.Match[str]) -> str:
         name, version = match[1], match[2]
+        if version.endswith("+cpu"):
+            # A universal resolve splits torch by marker, so the lock already
+            # holds a `+cpu` pin of its own alongside the PyPI one:
+            #
+            #   torch==2.14.1 ; sys_platform == 'darwin'
+            #   torch==2.14.1+cpu ; sys_platform != 'darwin'
+            #
+            # That entry is the CPU wheel, so it needs nothing added. Appending
+            # `+cpu` to its version to look it up would ask for `2.14.1+cpu+cpu`
+            # and fail, which is why this returns the entry untouched.
+            return match[0]
         hashes = cpu_hashes.get((name, f"{version}+cpu"))
         if not hashes:
             raise ValueError(f"Missing CPU hashes for {name}=={version}")

@@ -34,3 +34,60 @@ def test_cpu_hashes_reject_different_package_version() -> None:
     cpu_requirements = f"torch==2.12.0+cpu \\\n    --hash=sha256:{'b' * 64}\n"
     with pytest.raises(ValueError, match="Missing CPU hashes for torch==2.13.0"):
         add_hashes(requirements, cpu_requirements)
+
+
+def test_cpu_hashes_leave_an_existing_cpu_pin_untouched() -> None:
+    """A universal resolve emits a `+cpu` pin of its own, which needs nothing.
+
+    `uv pip compile --universal --torch-backend cpu` splits torch by marker, so
+    the lock holds both a PyPI pin for darwin and a `+cpu` pin for everything
+    else. The `+cpu` entry is already the CPU wheel; looking it up by appending
+    `+cpu` to its version would ask for `2.13.0+cpu+cpu` and fail.
+    """
+    script = (
+        Path(__file__).resolve().parents[6] / "infra/scripts/add_cpu_torch_hashes.py"
+    )
+    add_hashes = runpy.run_path(str(script))["add_cpu_hashes"]
+    pypi_hash = "a" * 64
+    cpu_hash = "b" * 64
+    requirements = (
+        f"torch==2.13.0 ; sys_platform == 'darwin' \\\n"
+        f"    --hash=sha256:{pypi_hash}\n"
+        f"torch==2.13.0+cpu ; sys_platform != 'darwin' \\\n"
+        f"    --hash=sha256:{cpu_hash}\n"
+    )
+    cpu_requirements = f"torch==2.13.0+cpu \\\n    --hash=sha256:{cpu_hash}\n"
+    expected = (
+        f"torch==2.13.0 ; sys_platform == 'darwin' \\\n"
+        f"    --hash=sha256:{pypi_hash} \\\n"
+        f"    --hash=sha256:{cpu_hash}\n"
+        f"torch==2.13.0+cpu ; sys_platform != 'darwin' \\\n"
+        f"    --hash=sha256:{cpu_hash}\n"
+    )
+    assert add_hashes(requirements, cpu_requirements) == expected
+    assert add_hashes(expected, cpu_requirements) == expected
+
+
+def test_cpu_hashes_handle_a_marker_split_for_torch_and_torchvision() -> None:
+    """The real lock splits both packages, which is what broke the script."""
+    script = (
+        Path(__file__).resolve().parents[6] / "infra/scripts/add_cpu_torch_hashes.py"
+    )
+    add_hashes = runpy.run_path(str(script))["add_cpu_hashes"]
+    requirements = (
+        f"torch==2.14.1 ; sys_platform == 'darwin' \\\n    --hash=sha256:{'a' * 64}\n"
+        f"torch==2.14.1+cpu ; sys_platform != 'darwin' \\\n"
+        f"    --hash=sha256:{'b' * 64}\n"
+        f"torchvision==0.29.1 ; sys_platform == 'darwin' \\\n"
+        f"    --hash=sha256:{'c' * 64}\n"
+        f"torchvision==0.29.1+cpu ; sys_platform != 'darwin' \\\n"
+        f"    --hash=sha256:{'d' * 64}\n"
+    )
+    cpu_requirements = (
+        f"torch==2.14.1+cpu \\\n    --hash=sha256:{'b' * 64}\n"
+        f"torchvision==0.29.1+cpu \\\n    --hash=sha256:{'d' * 64}\n"
+    )
+    result = add_hashes(requirements, cpu_requirements)
+    assert f"    --hash=sha256:{'b' * 64}" in result.split("torch==2.14.1+cpu")[0]
+    assert f"    --hash=sha256:{'d' * 64}" in result.split("torchvision==0.29.1+cpu")[0]
+    assert result.count("torch==2.14.1+cpu ; sys_platform != 'darwin'") == 1