Sandbox auth proxy

Inject credentials into outbound API requests from sandboxes without hardcoding secrets.

The auth proxy lets sandbox code call external APIs (OpenAI, Anthropic, GitHub, etc.) without hardcoding credentials. When configured on a sandbox, a proxy sidecar automatically injects authentication headers into matching outbound requests using your workspace secrets or write-only credentials you provide in the proxy config.

You must configure your secrets (e.g., OPENAI_API_KEY) in your LangSmith workspace settings before creating a sandbox that references them.

Configure auth proxy rules

Add a proxy_config when creating a sandbox, or update an existing sandbox by patching its proxy_config. Each rule specifies:

Field	Description
match_hosts	Hosts to intercept (supports globs like *.github.com)
match_paths	Paths to match (empty = all paths)
headers	Headers to inject, each with a name, type, and value
no_proxy	Hosts to bypass the proxy entirely (e.g. localhost)

Header types

Each header has a type that controls how its value is stored and displayed:

Type	Description
workspace_secret	References a workspace secret using {KEY} syntax. Resolved when the proxy configuration is applied.
plaintext	Value is stored and returned as-is. Use for non-sensitive headers.
opaque	Write-only. Value is encrypted at rest and never returned via the API.

Single API example

Create a sandbox that automatically injects an OpenAI API key into outbound requests:

curl -X POST "$LANGSMITH_ENDPOINT/v2/sandboxes/boxes" \
  -H "x-api-key: $LANGSMITH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "openai-sandbox",
    "wait_for_ready": true,
    "proxy_config": {
      "rules": [
        {
          "name": "openai-api",
          "match_hosts": ["api.openai.com"],
          "headers": [
            {
              "name": "Authorization",
              "type": "workspace_secret",
              "value": "Bearer {OPENAI_API_KEY}"
            }
          ]
        }
      ]
    }
  }'

The sandbox can now call OpenAI with no API key setup—the proxy injects it automatically.

Multiple API example

Add multiple rules to authenticate with several services at once:

curl -X POST "$LANGSMITH_ENDPOINT/v2/sandboxes/boxes" \
  -H "x-api-key: $LANGSMITH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "multi-api-sandbox",
    "wait_for_ready": true,
    "proxy_config": {
      "rules": [
        {
          "name": "openai-api",
          "match_hosts": ["api.openai.com"],
          "headers": [
            {
              "name": "Authorization",
              "type": "workspace_secret",
              "value": "Bearer {OPENAI_API_KEY}"
            }
          ]
        },
        {
          "name": "anthropic-api",
          "match_hosts": ["api.anthropic.com"],
          "headers": [
            {
              "name": "x-api-key",
              "type": "workspace_secret",
              "value": "{ANTHROPIC_API_KEY}"
            },
            {
              "name": "anthropic-version",
              "type": "plaintext",
              "value": "2023-06-01"
            }
          ]
        },
        {
          "name": "github-api",
          "match_hosts": ["api.github.com"],
          "match_paths": ["/repos/*", "/user"],
          "headers": [
            {
              "name": "Authorization",
              "type": "workspace_secret",
              "value": "Bearer {GITHUB_TOKEN}"
            }
          ]
        }
      ],
      "no_proxy": ["localhost", "127.0.0.1"]
    }
  }'

GitHub example

Open SWE authenticates GitHub access by minting a short-lived GitHub App installation token outside the sandbox, then patching the sandbox with write-only opaque proxy rules. This keeps the short-lived GitHub access token out of the sandbox filesystem and out of deployment environment variables.

Configure two rules:

Host	Header
api.github.com	Authorization: Bearer <github-token> for gh and REST API calls
github.com, *.github.com	Authorization: Basic <base64("x-access-token:<github-token>")> for Git over HTTPS operations like clone, fetch, and push

Python

import base64
import os
from typing import Any

import httpx


def github_proxy_rules(github_token: str) -> list[dict[str, Any]]:
    basic_auth = base64.b64encode(
        f"x-access-token:{github_token}".encode()
    ).decode()

    return [
        {
            "name": "github-api",
            "match_hosts": ["api.github.com"],
            "headers": [
                {
                    "name": "Authorization",
                    "type": "opaque",
                    "value": f"Bearer {github_token}",
                }
            ],
        },
        {
            "name": "github",
            "match_hosts": ["github.com", "*.github.com"],
            "headers": [
                {
                    "name": "Authorization",
                    "type": "opaque",
                    "value": f"Basic {basic_auth}",
                }
            ],
        },
    ]


def configure_github_proxy(sandbox_name: str, github_token: str) -> None:
    endpoint = os.environ.get(
        "LANGSMITH_ENDPOINT", "https://api.smith.langchain.com"
    )
    response = httpx.patch(
        f"{endpoint}/v2/sandboxes/boxes/{sandbox_name}",
        headers={"x-api-key": os.environ["LANGSMITH_API_KEY"]},
        json={"proxy_config": {"rules": github_proxy_rules(github_token)}},
        timeout=30.0,
    )
    response.raise_for_status()

Call configure_github_proxy after creating or reattaching to a sandbox. GitHub App installation tokens expire, so refresh the proxy config whenever you reuse a sandbox for a new run.

Inside the sandbox, set a non-secret placeholder token when a CLI requires a local credential before it sends a request:

GH_TOKEN=dummy gh repo view langchain-ai/langchain
GH_TOKEN=dummy gh pr list --repo langchain-ai/langchain
GH_TOKEN=dummy gh repo clone langchain-ai/langchain

The placeholder only satisfies the gh CLI’s local check. The proxy injects the real Authorization header into the outbound request.

Configure via SDK

Python

from langsmith.sandbox import SandboxClient

client = SandboxClient()

client.create_sandbox(
    name="openai-sandbox",
    proxy_config={
        "rules": [
            {
                "name": "openai-api",
                "match_hosts": ["api.openai.com"],
                "headers": [
                    {
                        "name": "Authorization",
                        "type": "workspace_secret",
                        "value": "Bearer {OPENAI_API_KEY}",
                    }
                ],
            }
        ]
    },
)

Callback credential example

Static workspace_secret rules pull credentials from your workspace when the proxy configuration is applied, and opaque rules let your application patch in short-lived credentials such as the GitHub token example. For credentials that must be resolved by your own service at proxy time, use a callback. The proxy POSTs to a URL you provide, your endpoint returns the headers to inject, and the proxy caches the result.

Callbacks are configured alongside rules under proxy_config:

Field	Description
match_hosts	Hosts to intercept (same syntax as rules; supports globs like *.github.com).
url	Your callback endpoint. Must be an http:// or https:// URL reachable from the proxy.
request_headers	Headers attached to the proxy → callback request, e.g., an HMAC or shared secret your endpoint uses to verify the request. Only plaintext and opaque types are permitted (no workspace_secret).
ttl_seconds	How long resolved headers are cached before re-invoking the callback. Must be between 60 and 3600.

Static rules win. If any rule in rules matches the host, the callback is skipped for that host. Within rules, first-match-wins; the same applies between callbacks if multiple match.

Callback contract

The proxy makes the following request whenever it needs to resolve credentials for a matched host on a cache miss:

POST <callback.url>
Content-Type: application/json
<request_headers from your config, attached verbatim>

{"host": "api.example.com", "port": 443}

Your endpoint must respond 2xx with a JSON body:

{
  "headers": {
    "Authorization": "Bearer <token>",
    "X-Org-Id": "..."
  }
}

The proxy injects every header in the response into the sandbox’s outbound request and caches the response for ttl_seconds. Any non-2xx response, transport error, or malformed JSON fails closed: the sandbox’s request is rejected with 502 callback resolution failed (no headers injected, response not cached).

Example

Use a callback when your OAuth tokens are minted on demand by your own service:

curl -X POST "$LANGSMITH_ENDPOINT/v2/sandboxes/boxes" \
  -H "x-api-key: $LANGSMITH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "snapshot_id": "<snapshot-uuid>",
    "name": "callback-sandbox",
    "wait_for_ready": true,
    "proxy_config": {
      "callbacks": [
        {
          "match_hosts": ["api.github.com", "*.githubusercontent.com"],
          "url": "https://auth.your-app.example.com/sandbox-credentials",
          "request_headers": [
            {
              "name": "X-Integrator-Secret",
              "type": "opaque",
              "value": "<shared-secret-your-endpoint-verifies>"
            }
          ],
          "ttl_seconds": 300
        }
      ]
    }
  }'

Configure via SDK

Python

from langsmith.sandbox import SandboxClient

client = SandboxClient()

client.create_sandbox(
    name="callback-sandbox",
    proxy_config={
        "callbacks": [
            {
                "match_hosts": ["api.github.com", "*.githubusercontent.com"],
                "url": "https://auth.your-app.example.com/sandbox-credentials",
                "request_headers": [
                    {
                        "name": "X-Integrator-Secret",
                        "type": "opaque",
                        "value": "<shared-secret-your-endpoint-verifies>",
                    }
                ],
                "ttl_seconds": 300,
            }
        ]
    },
)

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