fix: avoid ARG_MAX on sandbox writes by using SDK write()

apps/agent/agent/integrations/langsmith.py

@@ -16,11 +16,12 @@ from deepagents.backends.protocol import (
     FileDownloadResponse,
     FileUploadResponse,
     SandboxBackendProtocol,
+    WriteResult,
 )
 from deepagents.backends.sandbox import BaseSandbox
 
-from langsmith.sandbox import Sandbox, SandboxClient, SandboxTemplate
-
+if TYPE_CHECKING:
+    from langsmith.sandbox import Sandbox, SandboxClient, SandboxTemplate
 
 
 class SandboxProvider(ABC):
@@ -82,14 +83,25 @@ class LangSmithBackend(BaseSandbox):
             truncated=False,
         )
 
+    def write(self, file_path: str, content: str) -> WriteResult:
+        """Write content using the LangSmith SDK to avoid ARG_MAX.
+
+        BaseSandbox.write() sends the full content in a shell command, which
+        can exceed ARG_MAX for large content. This override uses the SDK's
+        native write(), which sends content in the HTTP body.
+        """
+        try:
+            self._sandbox.write(file_path, content.encode("utf-8"))
+            return WriteResult(path=file_path, files_update=None)
+        except Exception as e:
+            return WriteResult(error=f"Failed to write file '{file_path}': {e}")
+
     def download_files(self, paths: list[str]) -> list[FileDownloadResponse]:
         """Download multiple files from the LangSmith sandbox."""
         responses: list[FileDownloadResponse] = []
         for path in paths:
             content = self._sandbox.read(path)
-            responses.append(
-                FileDownloadResponse(path=path, content=content, error=None)
-            )
+            responses.append(FileDownloadResponse(path=path, content=content, error=None))
         return responses
 
     def upload_files(self, files: list[tuple[str, bytes]]) -> list[FileUploadResponse]:
@@ -148,10 +160,7 @@ class LangSmithProvider(SandboxProvider):
                 template_name=resolved_template_name, timeout=timeout
             )
         except Exception as e:
-            msg = (
-                f"Failed to create sandbox from template "
-                f"'{resolved_template_name}': {e}"
-            )
+            msg = f"Failed to create sandbox from template '{resolved_template_name}': {e}"
             raise RuntimeError(msg) from e
 
         # Verify sandbox is ready by polling
@@ -160,7 +169,7 @@ class LangSmithProvider(SandboxProvider):
                 result = sandbox.run("echo ready", timeout=5)
                 if result.exit_code == 0:
                     break
-            except Exception:  
+            except Exception:
                 pass
             time.sleep(2)
         else:
@@ -171,7 +180,7 @@ class LangSmithProvider(SandboxProvider):
 
         return LangSmithBackend(sandbox)
 
-    def delete(self, *, sandbox_id: str, **kwargs: Any) -> None: 
+    def delete(self, *, sandbox_id: str, **kwargs: Any) -> None:
         """Delete a LangSmith sandbox."""
         self._client.delete_sandbox(sandbox_id)
 

apps/agent/uv.lock

@@ -976,7 +976,7 @@ wheels = [
 
 [[package]]
 name = "langsmith"
-version = "0.6.9"
+version = "0.7.1"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "httpx" },
@@ -989,9 +989,9 @@ dependencies = [
     { name = "xxhash" },
     { name = "zstandard" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/9a/e0/463a70b43d6755b01598bb59932eec8e2029afcab455b5312c318ac457b5/langsmith-0.6.9.tar.gz", hash = "sha256:aae04cec6e6d8e133f63ba71c332ce0fbd2cda95260db7746ff4c3b6a3c41db1", size = 973557, upload-time = "2026-02-05T20:10:55.629Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/67/48/3151de6df96e0977b8d319b03905e29db0df6929a85df1d922a030b7e68d/langsmith-0.7.1.tar.gz", hash = "sha256:e3fec2f97f7c5192f192f4873d6a076b8c6469768022323dded07087d8cb70a4", size = 984367, upload-time = "2026-02-10T01:55:24.696Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/e6/8e/063e09c5e8a3dcd77e2a8f0bff3f71c1c52a9d238da1bcafd2df3281da17/langsmith-0.6.9-py3-none-any.whl", hash = "sha256:86ba521e042397f6fbb79d63991df9d5f7b6a6dd6a6323d4f92131291478dcff", size = 319228, upload-time = "2026-02-05T20:10:54.248Z" },
+    { url = "https://files.pythonhosted.org/packages/ce/87/6f2b008a456b4f5fd0fb1509bb7e1e9368c1a0c9641a535f224a9ddc10f3/langsmith-0.7.1-py3-none-any.whl", hash = "sha256:92cfa54253d35417184c297ad25bfd921d95f15d60a1ca75f14d4e7acd152a29", size = 322515, upload-time = "2026-02-10T01:55:22.531Z" },
 ]
 
 [package.optional-dependencies]
@@ -1028,6 +1028,7 @@ dependencies = [
     { name = "langgraph" },
     { name = "langgraph-cli", extra = ["inmem"] },
     { name = "langgraph-sdk" },
+    { name = "langsmith" },
     { name = "markdownify" },
     { name = "pyjwt" },
     { name = "uvicorn" },
@@ -1051,6 +1052,7 @@ requires-dist = [
     { name = "langgraph", specifier = ">=1.0.8" },
     { name = "langgraph-cli", extras = ["inmem"], specifier = ">=0.4.12" },
     { name = "langgraph-sdk", specifier = ">=0.1.0" },
+    { name = "langsmith", specifier = ">=0.7.1" },
     { name = "markdownify", specifier = ">=1.2.2" },
     { name = "pyjwt", specifier = ">=2.8.0" },
     { name = "pytest", marker = "extra == 'dev'", specifier = ">=7.0.0" },