diff --git a/core/python/long-horizon-harness/pyproject.toml b/core/python/long-horizon-harness/pyproject.toml
index 82a2e98751..1957590562 100644
--- a/core/python/long-horizon-harness/pyproject.toml
+++ b/core/python/long-horizon-harness/pyproject.toml
@@ -17,7 +17,7 @@ dependencies = [
     "fastapi>=0.136.1",
     "uvicorn>=0.47.0",
     "pyjwt>=2.12.1",
-    "python-multipart>=0.0.29",
+    "python-multipart>=0.0.31",
     "email-validator>=2.3.0",
     # pyopenssl 26 added strict Context immutability after first use, which
     # breaks urllib3.contrib.pyopenssl (still mutates verify_mode post-use)
diff --git a/core/python/long-horizon-harness/uv.lock b/core/python/long-horizon-harness/uv.lock
index d75fa19030..4d0d4633f7 100644
--- a/core/python/long-horizon-harness/uv.lock
+++ b/core/python/long-horizon-harness/uv.lock
@@ -129,9 +129,9 @@ name = "aiologic"
 version = "0.17.1"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
-    { name = "sniffio" },
-    { name = "typing-extensions" },
-    { name = "wrapt" },
+    { name = "sniffio", marker = "python_full_version < '3.13'" },
+    { name = "typing-extensions", marker = "python_full_version < '3.13'" },
+    { name = "wrapt", marker = "python_full_version < '3.13'" },
 ]
 sdist = { url = "https://files.pythonhosted.org/packages/f1/7a/d51f2fde1e8ae8a83431f8e97b7a71e9358cdb1d4d2ce6be387fa44d68de/aiologic-0.17.1.tar.gz", hash = "sha256:2e1b93b9e88ced318c2a63ad7b382688f40cbfe40e3d42258d49dc9c5aea179d", size = 252354, upload-time = "2026-06-27T20:41:33.25Z" }
 wheels = [
@@ -572,8 +572,8 @@ name = "culsans"
 version = "0.11.0"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
-    { name = "aiologic" },
-    { name = "typing-extensions" },
+    { name = "aiologic", marker = "python_full_version < '3.13'" },
+    { name = "typing-extensions", marker = "python_full_version < '3.13'" },
 ]
 sdist = { url = "https://files.pythonhosted.org/packages/d9/e3/49afa1bc180e0d28008ec6bcdf82a4072d1c7a41032b5b759b60814ca4b0/culsans-0.11.0.tar.gz", hash = "sha256:0b43d0d05dce6106293d114c86e3fb4bfc63088cfe8ff08ed3fe36891447fe33", size = 107546, upload-time = "2025-12-31T23:15:38.196Z" }
 wheels = [
@@ -1857,7 +1857,7 @@ requires-dist = [
     { name = "pandas", marker = "extra == 'data'", specifier = ">=3.0.3" },
     { name = "pyjwt", specifier = ">=2.12.1" },
     { name = "pyopenssl", specifier = "<25.0" },
-    { name = "python-multipart", specifier = ">=0.0.29" },
+    { name = "python-multipart", specifier = ">=0.0.31" },
     { name = "ruff", marker = "extra == 'lint'", specifier = ">=0.4.6,<1.0.0" },
     { name = "seaborn", marker = "extra == 'data'", specifier = ">=0.13.2" },
     { name = "ty", marker = "extra == 'lint'", specifier = ">=0.0.1a0" },
@@ -2891,11 +2891,11 @@ wheels = [
 
 [[package]]
 name = "python-multipart"
-version = "0.0.29"
+version = "0.0.31"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/4e/fe/70bd71a6738b09a0bdf6480ca6436b167469ca4578b2a0efbe390b4b0e70/python_multipart-0.0.29.tar.gz", hash = "sha256:643e93849196645e2dbdd81a0f8829a23123ad7f797a84a364c6fb3563f18904", size = 45678, upload-time = "2026-05-17T17:29:47.654Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/64/7e/9b35ad8f3d9ca680f7c87a88f19612fdd8da9796c4d3b46e560ac79dcc4a/python_multipart-0.0.31.tar.gz", hash = "sha256:fc631183bb13e56db3158a4909908dfb2e23565286744e798241e63750e5d680", size = 46689, upload-time = "2026-06-04T08:27:49.014Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/8f/cb/769cfc37177252872a45a71f3fbdde9d51b471a3f3c14bfe95dde3407386/python_multipart-0.0.29-py3-none-any.whl", hash = "sha256:2ddcc971cef266225f54f552d8fa10bcfbb1f14446caec199060daac59ff2d69", size = 29640, upload-time = "2026-05-17T17:29:45.69Z" },
+    { url = "https://files.pythonhosted.org/packages/5e/1e/7f7f299527a5a8ad90acd5f2f78dfa6c8495c6301a3205106ea68a84de96/python_multipart-0.0.31-py3-none-any.whl", hash = "sha256:8408153d68a9773291fc1da39a8b85a50044bddbabd2dd72e9229776b7b15e28", size = 29996, upload-time = "2026-06-04T08:27:47.804Z" },
 ]
 
 [[package]]