Setting the file. One moment.
Subchapter 4.43
shared/managed-agents-environments.mdMarkdown12 KBView on GitHub
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.
| 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.
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" },
},
});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.
| 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. |
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.
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.
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:
write tool (or bash) must be enabled for the agent to create output files.files.list / files.download captures outputs written to /mnt/session/outputs/.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.sessions.create() verbatim (e.g. sesn_011CZx...) — the API validates the prefix.session.status_idle and output files appearing in files.list. Retry once or twice if empty.Fallback when
scope_idfiltering is unavailable (older SDK, or endpoint returns an error): send a follow-upuser.messageasking the agent toreadeach file under/mnt/session/outputs/and return the contents. The agent streams the file bodies back asagent.messagetext. 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.
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 | ✅ | "github_repository" |
url | ✅ | The GitHub repository URL |
authorization_token | ✅ | GitHub Personal Access Token with repository access. Never echoed in API responses. |
mount_path | ❌ | Path where the repository will be cloned. Defaults to /workspace/<repo-name>. |
checkout | ❌ | {type: "branch", name: "..."} or {type: "commit", sha: "..."}. Defaults to the repo’s default branch. |
Token permission levels (fine-grained PATs):
Contents: Read — clone onlyContents: Read and write — push changes and create pull requestsHow 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.
‼️ To generate pull requests you also need GitHub MCP server access — the
github_repositoryresource gives filesystem + git access only. Seeshared/managed-agents-tools.md→ MCP Servers. The PR workflow is: edit files in the mounted repo → push branch viabash(authenticated via the git proxy usingauthorization_token) → create PR via the MCPcreate_pull_requesttool (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"},
}],
)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.