---
title: account_create_ephemeral
description: Creates a temporary ephemeral account that exists only for the
  transaction duration
source_url:
  html: https://thru.org/docs/spec/vm/syscalls/account_create_ephemeral/
  md: https://thru.org/docs/spec/vm/syscalls/account_create_ephemeral.md
---

# account_create_ephemeral

## Overview

The `account_create_ephemeral` syscall creates a temporary account that exists only for the duration of the current transaction. Ephemeral accounts do not require state proofs and are automatically cleaned up at transaction end.

## Syscall Code

**Code:** `0x05` (`TN_SYSCALL_CODE_ACCOUNT_CREATE_EPHEMERAL`)

## C SDK Function

```c
ulong tsys_account_create_ephemeral( ulong account_idx,
                                     uchar const seed[TN_SEED_SIZE] );
```

## Arguments

**`account_idx` · *ulong* · **required****

Index of the account slot to create. Must be writable in the transaction and currently non-existent.

**`seed` · *uchar const\[TN\_SEED\_SIZE]* · **required****

Fixed 32-byte seed used for address derivation.

## Return Value

Returns a syscall result code:

**`Success` · *ulong***

- `TN_VM_SYSCALL_SUCCESS` (0) - Ephemeral account created successfully

**`Error Codes` · *ulong***

- `TN_VM_ERR_SYSCALL_INVALID_ACCOUNT_INDEX` (-8) - Account index out of bounds
- `TN_VM_ERR_SYSCALL_ACCOUNT_NOT_WRITABLE` (-10) - Account not writable in transaction
- `TN_VM_ERR_SYSCALL_ACCOUNT_ALREADY_EXISTS` (-15) - Account already exists
- `TN_VM_ERR_SYSCALL_INVALID_ADDRESS` (-22) - Invalid virtual address for seed
- `TN_VM_ERR_SYSCALL_BAD_ACCOUNT_ADDRESS` (-16) - Computed address doesn’t match expected
- `TN_VM_ERR_SYSCALL_STATE_BYTES_ADDED_OVERFLOW` (-47) - State bytes counter overflow during activation

## Resource Consumption

### Compute Units

- **Base cost**: `TN_VM_SYSCALL_BASE_COST` (512 units)
- **Seed cost**: Additional units equal to `TN_SEED_SIZE` bytes
- **Metadata cost**: Additional units equal to `sizeof(tsdk_account_meta_t)`
- **Total formula**: `base_cost + TN_SEED_SIZE + sizeof(tsdk_account_meta_t)`
- **Note**: No proof cost since ephemeral accounts don’t require state proofs

### Memory Pages

- **Page usage**: No direct page allocation (account data starts at size 0)
- **Metadata pages**: Allocates pages for account metadata structure
- **Cleanup**: All allocated pages are automatically freed at transaction end

### State Counter Impact

- **GASC (Global Activated State Counter)**: Incremented by `TSDK_ACCOUNT_META_FOOTPRINT` bytes
- **Purpose**: Tracks activated state for the ephemeral account creation in the global state counter
- **Overflow protection**: Returns `TN_VM_ERR_SYSCALL_STATE_BYTES_ADDED_OVERFLOW` if counter would overflow

## Side Effects

- **Account creation**: Creates a new account with EPHEMERAL flag set
- **Ownership**: Sets the current program as the account owner
- **Automatic cleanup**: Account will be deleted at transaction end

## Address Derivation

The ephemeral account address is computed as:

```plaintext
SHA256(current_program_pubkey || is_ephemeral(1) || seed)
```

## Usage Notes

- No state proof required (faster creation)
- Account exists only during transaction execution
- Cannot be used in balance transfers (ephemeral accounts rejected)
- Automatically deleted when transaction completes
- Perfect for temporary storage and intermediate computations
- The computed address must match the transaction’s expected address
- Seed must be exactly `TN_SEED_SIZE` (32 bytes)

## Differences from Permanent Accounts

| Feature | Permanent Account | Ephemeral Account |
| - | - | - |
| State proof | Required | Not required |
| Lifetime | Persists after transaction | Transaction only |
| Balance transfers | Allowed | Forbidden |
| Creation cost | Higher (includes proof) | Lower (no proof) |
| Address derivation | `is_ephemeral = 0` | `is_ephemeral = 1` |

## Example

```c
#include <thru-sdk/c/tn_sdk_syscall.h>
#include <string.h>

// Create ephemeral account for temporary storage
ulong account_idx = 3;
uchar seed[TN_SEED_SIZE] = { 0 };
memcpy( seed, "temp_storage", 12 );

ulong result = tsys_account_create_ephemeral( account_idx, seed );

if (result == TN_VM_SYSCALL_SUCCESS) {
    // Ephemeral account created successfully
    // Account will be automatically deleted at transaction end
    // Can be used for temporary data storage
    // Cannot participate in balance transfers
}
```