Context Variables

The ctx object is available in every exported function. It tells you who called the function, who signed the transaction, and which contract is executing.

Properties

Property	Type	Description
ctx.caller	str	The immediate caller — either a user address or a contract name
ctx.signer	str	The original transaction signer (never changes in a call chain)
ctx.this	str	The name of the currently executing contract
ctx.owner	str or None	The owner set when the contract was deployed
ctx.entry	tuple	(contract_name, function_name) of the transaction entry point
ctx.submission_name	str or None	The name of the contract being submitted (only during submission)

How Context Changes in Call Chains

When contract A calls contract B, the context updates:

User "alice" calls contract_a.do_something()
  → ctx.signer = "alice"
  → ctx.caller = "alice"
  → ctx.this   = "contract_a"

  contract_a calls contract_b.helper()
    → ctx.signer = "alice"      (unchanged — always the original signer)
    → ctx.caller = "contract_a" (the immediate caller changed)
    → ctx.this   = "contract_b" (now executing in B)

This distinction is critical for security. A token contract should check ctx.caller for allowance-based transfers, but ctx.signer for direct transfers.

Common Patterns

Owner-only functions

owner = Variable()

@construct
def seed():
    owner.set(ctx.caller)

@export
def admin_action():
    assert ctx.caller == owner.get(), "Only the owner can do this"
    # ... privileged logic

Preventing cross-contract calls

@export
def sensitive_action():
    assert ctx.caller == ctx.signer, "Must be called directly, not from another contract"

Identifying the entry point

@export
def process():
    entry_contract, entry_function = ctx.entry
    # Useful for logging or conditional logic based on how we were reached

Environment Variables

In addition to ctx, exported functions have access to block-level environment variables injected by the runtime:

Variable	Type	Description
now	Datetime	Block timestamp (deterministic, agreed by validators)
block_num	int	Current block height
block_hash	str	Current block hash
chain_id	str	Network chain identifier

@export
def time_locked_withdraw(amount: float):
    assert now > unlock_time.get(), "Too early"
    balances[ctx.caller] -= amount

These values are the same for every transaction in the same block, ensuring deterministic execution.