---
# @generated by sylphx-gen. Do not edit.
title: "Begin a transfer"
description: "`agents.transfers.begin` (POST /v1/{parent}/transfers:begin): Stages a uniquely identified source epoch on an empty idle Session."
type: reference
product: agents
summary: "Stages a uniquely identified source epoch on an empty idle Session."
updated: 2026-09-28
nav: false
---

Stages a uniquely identified source epoch on an empty idle Session. The source adapter must already hold its durable one-writer fence.

- **Path** `POST https://api.sylphx.com/v1/orgs/acme/projects/shop/envs/production/agent_sessions/agent-session/transfers:begin`
- **Scope** `agents:sessions`
- **Effect** `write` — a successful call changes state.
- **Collection** [transfers](/docs/api/transfers)

## Request

| Field | Type | What it is |
| --- | --- | --- |
| `parent` | `string` | Empty idle destination Session, already created through the ordinary API. Required. |
| `operation_id` | `string` | Permanent caller identity; exact retries return the original transfer. Required. |
| `manifest` | `struct` | sylphx.agents.session-continuity.v1 manifest. At most 256 parts of 256 KiB, and 64 MiB overall. Source epoch must be a positive signed int64. Required. |
| `source_fence_sha256` | `string` | SHA-256 attestation of the original storage's durable writer marker. Required. |

## Response

| Field | Type | What it is |
| --- | --- | --- |
| `name` | `string` | Destination Session and immutable transfer identity. |
| `uid` | `string` | Immutable Resource UID. Output only. |
| `meta` | `ResourceMeta` | Standard metadata. Output only. |
| `state` | `string` | staging, verified, adopted or aborted. Verified does not admit execution. Output only. |
| `manifest` | `struct` | Versioned source identity, transfer epoch and ordered byte/part digests. Output only. |
| `manifest_sha256` | `string` | Digest of the checked manifest, including original Session and epoch. Output only. |
| `source_fence_sha256` | `string` | Caller attestation bound to its original durable writer fence. A digest does not prove that an external writer has stopped. Output only. |
| `received_parts` | `SessionTransferPart[]` | Exact stored-part metadata. Private payload bytes are never returned. Output only. |
| `receipt` | `struct` | Original identities, destination mappings and unresolved effect holds. Output only. |
| `receipt_sha256` | `string` | Digest the source adapter reads back before acknowledging its handoff. Output only. |
| `create_time` | `timestamp` | Creation time. Output only. |
| `update_time` | `timestamp` | Last lifecycle change time. Output only. |

### ResourceMeta

| Field | Type | What it is |
| --- | --- | --- |
| `generation` | `int64` | Increases by one on every change to `spec`. Output only. |
| `etag` | `string` | Strong ETag (AIP-154): changes on any change to spec, status, or metadata. Send it back as `If-Match` or `etag` to make Update and Delete conditional; a mismatch fails with ABORTED / 409 `ETAG_MISMATCH`. Output only. |
| `create_time` | `timestamp` | When the Resource was created. Output only. |
| `update_time` | `timestamp` | When the Resource last changed. Output only. |
| `delete_time` | `timestamp` | Set while the Resource is being deleted. Output only. |
| `labels` | `map<string, string>` | Caller-writable, indexed labels (AIP-122 label rules). |
| `annotations` | `map<string, string>` | Caller-writable, unindexed annotations. |
| `display_name` | `string` | Caller-writable human-readable name. |
| `creator` | `string` | The principal that created the Resource. Output only. |

### SessionTransferPart

| Field | Type | What it is |
| --- | --- | --- |
| `index` | `int64` | Zero-based index in the immutable manifest. |
| `bytes` | `int64` | Exact stored byte count. |
| `sha256` | `string` | SHA-256 of the exact binary body. |

## Errors

- [`UNAUTHENTICATED`](/docs/api/errors/UNAUTHENTICATED) — No valid key or token was presented.
- [`PERMISSION_DENIED`](/docs/api/errors/PERMISSION_DENIED) — The key lacks the method's permission.
- [`RESOURCE_NOT_FOUND`](/docs/api/errors/RESOURCE_NOT_FOUND) — The named Resource does not exist or is not visible.
- [`INVALID_FIELD`](/docs/api/errors/INVALID_FIELD) — A field failed validation.
- [`INVALID_STATE`](/docs/api/errors/INVALID_STATE) — The Resource is in a state that forbids the call.
- [`RESOURCE_ALREADY_EXISTS`](/docs/api/errors/RESOURCE_ALREADY_EXISTS) — A Resource with this name exists.
- [`IDEMPOTENCY_KEY_REUSED`](/docs/api/errors/IDEMPOTENCY_KEY_REUSED) — An Idempotency-Key was reused with another body.

Every error arrives in the body [Errors](/docs/platform/errors) describes.

## Examples

**cURL**

```curl
curl -X POST "https://api.sylphx.com/v1/orgs/acme/projects/shop/envs/production/agent_sessions/agent-session/transfers:begin" \
  -H "Authorization: Bearer $SYLPHX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"manifest":{},"operation_id":"…","source_fence_sha256":"…"}'
```

**TypeScript**

```ts
const response = await sylphx.agents.transfers.begin({ manifest: {}, operationId: '…', parent: 'orgs/acme/projects/shop/envs/production/agent_sessions/agent-session', sourceFenceSha256: '…' })
```

**Rust**

```rust
let mut req = sylphx::agents::BeginAgentSessionTransferRequest::default();
req.manifest = Some(Default::default());
req.operation_id = "…".to_string();
req.parent = "orgs/acme/projects/shop/envs/production/agent_sessions/agent-session".to_string();
req.source_fence_sha256 = "…".to_string();
let response = sx.agents().transfers().begin(req).await?;
```

**CLI**

```bash
sylphx agents transfers begin orgs/acme/projects/shop/envs/production/agent_sessions/agent-session
```

**MCP**

```json
{ "method_id": "agents.transfers.begin", "args": {"manifest":{},"operation_id":"…","parent":"orgs/acme/projects/shop/envs/production/agent_sessions/agent-session","source_fence_sha256":"…"} }
```