skills/skills/claude-api/shared/managed-agents-environments.md

Managed Agents - Environments & Resources

Environments

Creating a session requires an environment_id. Environments are reusable configuration templates for spinning up containers in Anthropic's infrastructure - you might create different environments for different use cases (e.g. data visualization vs web development, with different package sets). Anthropic handles scaling, container lifecycle, and work orchestration.

Environment names must be unique. Creating an environment with an existing name returns 409.

Networking

Network Policy	Description
unrestricted	Full egress (except legal blocklist)
limited	Deny-by-default; opt in via allowed_hosts / allow_package_managers / allow_mcp_servers

{
  "networking": {
    "type": "limited",
    "allow_package_managers": true,
    "allow_mcp_servers": true,
    "allowed_hosts": ["api.example.com"]
  }
}

All three limited fields are optional. allow_package_managers (default false) permits PyPI/npm/etc.; allow_mcp_servers (default false) permits the agent's configured MCP server endpoints without listing them in allowed_hosts.

MCP caveat: Under limited networking, either set allow_mcp_servers: true or add each MCP server domain to allowed_hosts. Otherwise the container can't reach them and tools silently fail.

Packages caveat: Under limited networking, packages requires allow_package_managers: true; otherwise the request fails with a 400. Listing the registry in allowed_hosts is not enough.

networking does not govern web_search / web_fetch. Those tools run on Anthropic's servers (in cloud and self-hosted environments), so limited egress and allowed_hosts don't restrict them. To restrict the sites they can reach, set allowed_domains / blocked_domains on the tool's configs entry in the agent toolset - see shared/managed-agents-tools.md § Web search & web fetch settings.

Creating an environment

The SDK adds managed-agents-2026-04-01 automatically. TypeScript:

const env = await client.beta.environments.create({
  name: "my_env",
  config: {
    type: "cloud",
    networking: { type: "unrestricted" },
  },
});

Self-hosted sandboxes

To run tool execution in your own infrastructure instead of Anthropic's, set config: {type: "self_hosted"} - the agent loop stays on Anthropic's side, but bash / file ops / code execute in a container you control via an outbound-polling worker. The networking block does not apply (you control egress). Resource mounting (file, github_repository) and memory stores behave differently - see shared/managed-agents-self-hosted-sandboxes.md for the worker, credentials, and cloud-vs-self-hosted comparison.

Environment CRUD

Operation	Method	Path	Notes
Create	POST	/v1/environments
List	GET	/v1/environments	Paginated (limit, after_id, before_id)
Get	GET	/v1/environments/{id}
Update	POST	/v1/environments/{id}	Changes apply only to new containers; existing sessions keep their original config
Delete	DELETE	/v1/environments/{id}	Returns 204.
Archive	POST	/v1/environments/{id}/archive	Makes it read-only; existing sessions continue, new sessions cannot reference it. No unarchive - terminal state.

---

Resources

Attach files, GitHub repositories, and memory stores to a session. Resources are resolved during session creation, so a bad file_id or an unreachable repo surfaces on the create call rather than mid-run. Creating a session does not by itself start work or provision the sandbox - without initial_events the session is only registered, and the sandbox comes up when the session first needs it (see shared/managed-agents-core.md -> Seeding a session with initial_events). Max 999 file resources per session. Multiple GitHub repositories per session are supported. For type: "memory_store" resources (persistent cross-session memory - max 8 per session), see shared/managed-agents-memory.md.

File Uploads (input - host -> agent)

Upload a file first via the Files API, then reference by file_id + mount_path:

// 1. Upload
const file = await client.beta.files.upload({
  file: fs.createReadStream("data.csv"),
  purpose: "agent",
});

// 2. Attach as a session resource
const session = await client.beta.sessions.create({
  agent: agent.id,
  environment_id: envId,
  resources: [
    { type: "file", file_id: file.id, mount_path: "/workspace/data.csv" }
  ],
});

mount_path is required and must be absolute. Parent directories are created automatically. Agent working directory defaults to /workspace. Files are mounted read-only - the agent writes modified versions to new paths.

Session outputs (output - agent -> host)

The agent can write files to /mnt/session/outputs/ during a session. These are automatically captured by the Files API and can be listed and downloaded afterwards:

// After the turn completes, list output files scoped to this session:
for await (const f of client.beta.files.list({
  scope_id: session.id,
  betas: ["managed-agents-2026-04-01"],
})) {
  console.log(f.filename, f.size_bytes);
  const resp = await client.beta.files.download(f.id);
  const text = await resp.text();
}

Requirements:

• The write tool (or bash) must be enabled for the agent to create output files.
• Session-scoped files.list / files.download captures outputs written to /mnt/session/outputs/.
• The filter parameter is scope_id (REST query param ?scope_id=<session_id>). The SDK's files resource auto-adds only the files-api-2025-04-14 header, so pass betas: ["managed-agents-2026-04-01"] explicitly (or both headers on raw HTTP) - without it the API may reject scope_id as an unknown field. Requires @anthropic-ai/sdk >= 0.88.0 / anthropic (Python) >= 0.92.0 - older versions don't type scope_id. The ant CLI does not expose this flag yet; use the SDK or curl.
• Pass the session ID returned by sessions.create() verbatim (e.g. sesn_011CZx...) - the API validates the prefix.
• There's a brief indexing lag (~1-3s) between session.status_idle and output files appearing in files.list. Retry once or twice if empty.

Fallback when scope_id filtering is unavailable (older SDK, or endpoint returns an error): send a follow-up user.message asking the agent to read each file under /mnt/session/outputs/ and return the contents. The agent streams the file bodies back as agent.message text. This works for text files only and costs output tokens - use it to unblock, not as the primary path.

This gives you a bidirectional file bridge: upload reference data in, download agent artifacts out.

GitHub Repositories

Clones a GitHub repository into the session container during initialization, before the agent begins execution. The agent can read, edit, commit, and push via bash (git). Multiple repositories per session are supported - add one resources entry per repo. Repositories are cached, so future sessions that use the same repository start faster.

Mounting a repository also loads any skills stored in its root .claude/skills directory - discovered once per session, from the repository state checked out at session start (cloud sandboxes only). See shared/managed-agents-tools.md -> Skills from a GitHub repository.

Repositories are attached for the lifetime of the session - to change which repositories are mounted, create a new session. You can rotate a repository's authorization_token on a running session via client.beta.sessions.resources.update(resource_id, {session_id, authorization_token}); the resource id is returned at session creation and by resources.list().

Fields:

Field	Required	Notes
type	Yes	"github_repository"
url	Yes	The GitHub repository URL
authorization_token	Yes	GitHub Personal Access Token with repository access. Never echoed in API responses.
mount_path	No	Path where the repository will be cloned. Defaults to /workspace/<repo-name>.
checkout	No	{type: "branch", name: "..."} or {type: "commit", sha: "..."}. Defaults to the repo's default branch.

Token permission levels (fine-grained PATs):

• Contents: Read - clone only
• Contents: Read and write - push changes and create pull requests

How auth works: authorization_token is never placed inside the container. git pull / git push and GitHub REST calls against the attached repository are routed through an Anthropic-side git proxy that injects the token after the request leaves the sandbox. Code running in the container - including anything the agent writes - cannot read or exfiltrate it.

Important: To generate pull requests you also need GitHub MCP server access - the github_repository resource gives filesystem + git access only. See shared/managed-agents-tools.md -> MCP Servers. The PR workflow is: edit files in the mounted repo -> push branch via bash (authenticated via the git proxy using authorization_token) -> create PR via the MCP create_pull_request tool (authenticated via the vault).

TypeScript:

// 1. Create the agent - declare GitHub MCP (no auth here)
const agent = await client.beta.agents.create(
  {
    name: 'GitHub Agent',
    model: 'claude-opus-5',
    mcp_servers: [
      { type: 'url', name: 'github', url: 'https://api.githubcopilot.com/mcp/' },
    ],
    tools: [
      { type: 'agent_toolset_20260401', default_config: { enabled: true } },
      { type: 'mcp_toolset', mcp_server_name: 'github' },
    ],
  },
);

// 2. Start a session - attach vault for MCP auth + mount the repo
const session = await client.beta.sessions.create({
  agent: agent.id,
  environment_id: envId,
  vault_ids: [vaultId],  // vault contains the GitHub MCP OAuth credential
  resources: [
    {
      type: 'github_repository',
      url: 'https://github.com/owner/repo',
      authorization_token: process.env.GITHUB_TOKEN,  // repo clone token (!= MCP auth)
      checkout: { type: 'branch', name: 'main' },
    },
  ],
});

Python:

import os

agent = client.beta.agents.create(
    name="GitHub Agent",
    model="claude-opus-5",
    mcp_servers=[{
        "type": "url",
        "name": "github",
        "url": "https://api.githubcopilot.com/mcp/",
    }],
    tools=[
        {"type": "agent_toolset_20260401", "default_config": {"enabled": True}},
        {"type": "mcp_toolset", "mcp_server_name": "github"},
    ],
)

session = client.beta.sessions.create(
    agent=agent.id,
    environment_id=env_id,
    vault_ids=[vault_id],  # vault contains the GitHub MCP OAuth credential
    resources=[{
        "type": "github_repository",
        "url": "https://github.com/owner/repo",
        "authorization_token": os.environ["GITHUB_TOKEN"],  # repo clone token (!= MCP auth)
        "checkout": {"type": "branch", "name": "main"},
    }],
)

---

Files API

Upload and manage files for use as session resources, and download files the agent wrote to /mnt/session/outputs/.

Operation	Method	Path	SDK
Upload	POST	/v1/files	client.beta.files.upload({ file })
List	GET	/v1/files?scope_id=...	client.beta.files.list({ scope_id, betas: ["managed-agents-2026-04-01"] })
Get Metadata	GET	/v1/files/{id}	client.beta.files.retrieveMetadata(id)
Download	GET	/v1/files/{id}/content	client.beta.files.download(id) -> Response
Delete	DELETE	/v1/files/{id}	client.beta.files.delete(id)

The scope_id filter on List scopes the results to files written to /mnt/session/outputs/ by that session. Without the filter, you get all files uploaded to your account.