Parity Arb

Same-exchange YES + NO arbitrage when combined asks cost less than $1.00.

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Parity Arbitrage

When the YES ask + NO ask on the same exchange sums to less than $1.00, buying both sides locks in guaranteed profit. This is the simplest and lowest-risk arbitrage method.

How It Works

In a binary prediction market, one outcome must resolve to $1.00. If you can buy YES at $0.45 and NO at $0.48, your total cost is $0.93, guaranteeing $0.07 profit (minus fees).

YES ask = $0.45
NO ask  = $0.48 (derived from 1.0 - YES bid)
Total   = $0.93
Edge    = $1.00 - $0.93 = $0.07
Net     = $0.07 - fees

Engine Methods

scan_parity_arb

opp = engine.scan_parity_arb(
    market_id="election-winner",
    feed_name="polymarket",
    fee_rate=0.002,    # 20bps per trade
    max_size=50.0,
)

Returns a ParityArbitrageOpportunity or None.

execute_parity_arb

yes_id, no_id = engine.execute_parity_arb(
    market_id="election-winner",
    exchange="polymarket",
    yes_price=0.45,
    no_price=0.48,
    size=10.0,
)

Submits two FOK buy orders (YES + NO). If the second leg fails, the first is auto-canceled.

Pipeline: parity_arb_scanner

scanner = hz.parity_arb_scanner(
    market_id="election-winner",
    exchange="polymarket",
    feed_name="polymarket",
    min_edge=0.005,
    max_size=50.0,
    fee_rate=0.002,
    auto_execute=True,
    cooldown=5.0,
)

hz.run(pipeline=[scanner], ...)

Parameter	Type	Default	Description
market_id	str	required	Market to scan
exchange	str	"paper"	Exchange name
feed_name	str or None	None	Feed to read (defaults to exchange name)
min_edge	float	0.005	Minimum net edge
max_size	float	50.0	Maximum trade size
fee_rate	float	0.002	Fee rate per trade
auto_execute	bool	False	Auto-execute opportunities
cooldown	float	5.0	Seconds between executions

Stores ParityArbitrageOpportunity in ctx.params["last_parity_arb"].

One-Shot: parity_arb_sweep

result = hz.parity_arb_sweep(
    engine=engine,
    market_id="election-winner",
    feed_name="polymarket",
    exchange="polymarket",
    min_edge=0.005,
)

if result:
    print(f"Parity arb: cost={result.buy_price + result.sell_price:.4f} edge={result.net_edge:.4f}")

Returns ArbResult or None.

Rust Type: ParityArbitrageOpportunity

Field	Type	Description
market_id	str	Market identifier
exchange	str	Exchange name
yes_ask	float	YES ask price
no_ask	float	NO ask price
total_cost	float	YES + NO cost
raw_edge	float	1.0 - total_cost
net_edge	float	Edge after fees
max_size	float	Maximum executable size
is_executable	bool	Whether edge > 0 and size > 0