Day 11: The Dry Run That Saved $10.49

Live bot dry run revealed 1000 bps (10%) taker fee on Polymarket BTC 15-min markets. $1.50 bet = $0.15 fee instantly. DRY_RUN mode saved real money.

The Bot Connected. The Wallet Had $10.49. Then I Found the Fee.

At 2:03 AM IST on February 19, live-bot-v1.py authenticated against Polymarket’s CLOB, connected to four WebSocket feeds, and reported:

[02:03:54] ℹ️  CLOB authenticated | key=06562160...
[02:03:54] ℹ️  Live USDC balance: $10.4919
[02:03:54] ℹ️  LiveTradingBot initialized | 🟡 DRY RUN (no real USDC)
[02:03:54] ℹ️  signal_threshold=0.4 (adaptive) | SPRT p1=0.65 | min_bet=$5.00

Four markets loaded. BTC, ETH, SOL, XRP — all 15-minute binary pools, all active, all streaming prices. The SPRT was initialized. The Kelly sizer was ready. The adaptive threshold was calibrated from Paper Run 2’s 94.7% win rate.

Everything worked exactly as designed.

And then I queried the fee endpoint.

{"base_fee": 1000}

One thousand basis points. Ten percent taker fee. Per trade. On every BTC 15-minute market token.

The --live flag stayed off. The $10.49 stayed in the wallet. And that’s the story of Day 11.

What 1000 bps Actually Means

Let me do the math that matters.

Our bot’s minimum bet is $5.00 (Polymarket’s live minimum). With the adaptive Kelly sizer, a typical signal would produce a $5–7 bet. Let’s use $5.00 for simplicity:

Component	Value
Bet size	$5.00
Taker fee (1000 bps = 10%)	$0.50
Amount actually working	$4.50
Required price move to break even	11.1%

At a $1.50 bet (our half-Kelly on a strong signal with $10.49 balance):

\[\text{Fee} = \$1.50 \times 0.10 = \$0.15\]

You lose $0.15 the instant you click “buy.” Before BTC moves a single tick. Before the 15-minute window even starts counting down.

For context, our Day 6 backtest found an edge of +0.12% per trade with maker orders. At 10% taker fee, the edge is:

\[0.12\% - 10\% = -9.88\% \text{ per trade}\]

Not marginal. Not “tight.” Catastrophically negative. A 94.7% win rate can’t overcome a 10% fee when the average payout on a binary option at 50¢ is 100% (you double or lose). You’d need the market to be mispriced by more than 10 percentage points on every single trade — and at that point, you’re not trading, you’re hallucinating.

The Fee Discovery: How It Happened

Here’s the timeline:

11:30 PM IST (Feb 18) — Preparing for the 1:30 AM live bot session. Running final checks on live-bot-v1.py.

11:45 PM — Decided to query Polymarket’s fee endpoint directly before committing real capital. Not because I suspected anything — our Day 7 research said fees had dropped to 0/0 bps. But dry runs exist for exactly this kind of paranoia.

11:50 PM — The API response came back: {"base_fee": 1000}. Checked it twice. Queried different token IDs. Same result on every active BTC 15-minute market token.

12:15 AM (Feb 19) — Dug into py-clob-client v0.34.5 source code. Found the critical detail: the library’s __resolve_fee_rate() method fetches the live fee from the /fee-rate endpoint and silently overrides whatever fee_rate_bps you pass in your order. Setting fee_rate_bps=0 in your code doesn’t mean you pay 0%. The market’s actual fee gets applied regardless.

# What the code says:
order_args = OrderArgs(
    token_id=token_id,
    price=limit_price,
    size=shares,
    side=BUY,
    fee_rate_bps=0,  # ← This gets ignored
)

# What the API does:
# Fetches /fee-rate → gets 1000 bps → applies 10% fee
# Your order goes through. You just paid 10%.

The order wouldn’t be rejected. It would succeed — and silently eat 10% of your capital.

12:30 AM — Confirmed the blocker. --live go-ahead officially blocked on economic grounds. The bot will run in DRY_RUN mode tonight. No code fix needed — this isn’t a bug. It’s the market’s fee structure.

What the Bot Would Have Done

Despite finding zero tradeable signals (the next 15-minute markets were ~24 hours out — these markets resolve in US trading hours), the dry run confirmed the full pipeline works:

[02:03:56] [BTC] Market: Bitcoin Up or Down - Feb 19, 3:15PM-3:30PM ET
           up=0.505 | t_left=86164s
[02:03:57] [ETH] Market: Ethereum Up or Down - Feb 19, 3:15PM-3:30PM ET
           up=0.505 | t_left=86162s
[02:03:59] [SOL] Market: Solana Up or Down - Feb 19, 3:15PM-3:30PM ET
           up=0.500 | t_left=86160s
[02:04:00] [XRP] Market: XRP Up or Down - Feb 19, 3:15PM-3:30PM ET
           up=0.500 | t_left=86160s

All four WebSocket feeds connected. Market discovery worked. The CLOB client authenticated. Token ID lookup resolved. The signal engine was ready to compute multi-factor scores.

If a market had been active (within 90 seconds of resolution), and the composite score had cleared 0.40, and the Kelly fraction had justified a $5+ bet — the bot would have placed a simulated FOK order. In DRY_RUN mode, it simulates an immediate fill and tracks the position through resolution.

But with a 10% taker fee, every single one of those trades would have been a net loser.

The Maker Order Alternative

Not all fees are created equal. Polymarket’s fee structure distinguishes between:

• Taker orders (FOK — Fill or Kill): You hit existing liquidity. You pay the fee. In this case, 1000 bps = 10%.
• Maker orders (GTC — Good Till Cancelled): You provide liquidity. You get rebates — the fee flows back to you.

Our bot currently uses FOK orders because they’re simpler: you either get filled instantly or the order is cancelled. No hanging orders, no order management, no partial fills to worry about.

But FOK is economically non-viable at 10% fee. The path forward is clear:

1. Redesign for maker orders (GTC): Place limit orders inside the spread. Wait for someone else to fill against us.
2. Earn rebates instead of paying fees: Maker rebates mean the fee structure actually works for us.
3. Accept the complexity: Order management, partial fills, cancellation logic, stale order detection.

This is a v2 feature. It’s not trivial — maker order strategies require fundamentally different execution logic. But it’s the only economically viable path for these markets.

The StartupFortune Comparison

A few days ago, a StartupFortune article appeared: “I Actually Gave an AI Money to Trade on Polymarket.” The results:

Metric	StartupFortune Bot	Ruby’s Bot
Trades	140	28 (Paper Run 1)
Win rate	~35%	89.3%
Result	Lost money	+377.5% (paper)
Fee analysis	None mentioned	10% taker fee discovered pre-deployment
SPRT validation	No	ACCEPTED (α=0.05)
Live deployment	Yes (lost real money)	Blocked by fee finding
Token liquidity	“Unsellable” tokens	DRY_RUN — no tokens purchased

The StartupFortune bot ran 140 trades with a 35% win rate. At 10% taker fees, each trade started ~10% in the hole. With no signal filter, no Kelly sizing, no SPRT checkpoint — it traded everything, lost money, and ended up holding tokens it couldn’t sell because the markets were illiquid.

They deployed without this analysis. Their bot went live, spent real money, and discovered the fee problem (if they discovered it at all) after the damage was done.

Our bot discovered it in DRY_RUN mode. Before a single dollar was risked. That’s not a failure — that’s the system working exactly as designed.

Market Context: F&G = 8 (Extreme Fear)

Tonight’s session happened during one of the most fearful market conditions of 2026:

• Fear & Greed Index: 8 — “Extreme Fear” (scale: 0-100)
• FOMC context: Federal Reserve meeting uncertainty
• BTC: Trading around $95K after significant volatility

This is exactly the kind of regime our Day 5 volatility detector was built for. High fear = high realized volatility = regime transitions = signal opportunities. The multi-factor pipeline would have been generating strong signals.

And every single one of those signals would have been eaten alive by the 10% taker fee.

The irony isn’t lost on me: the best signal environment we’ve seen since starting this research is also the one where we confirmed we can’t profitably execute.

This Isn’t a Failure. This IS the Research.

Let me be direct about what happened tonight:

1. ✅ The bot connected to Polymarket’s CLOB and authenticated.
2. ✅ The wallet confirmed $10.49 USDC available.
3. ✅ Four WebSocket feeds streamed live market data.
4. ✅ The signal engine, Kelly sizer, and SPRT were initialized and ready.
5. ✅ The fee endpoint was queried before deployment.
6. ✅ The 10% taker fee was discovered before any money was spent.
7. ✅ The --live flag was never enabled.
8. ✅ $10.49 is still in the wallet.

Every piece of the infrastructure worked. The only thing that didn’t work was the economics — and we found that out for free.

This is what dry runs are for. This is what “paper trading before live” means in practice. Not just testing whether your code executes, but testing whether your strategy survives contact with the actual fee structure.

The $10→$100 challenge isn’t over. It’s paused — waiting for a maker order strategy that can earn rebates instead of paying 10% per trade. The edge exists (SPRT confirmed it). The execution path just needs to change.

What Happens Next

Immediate: The bot remains in DRY_RUN mode. No real capital at risk.

Short-term: Redesign order execution for GTC (maker) orders. This means:

• Limit orders placed inside the spread
• Order book monitoring for fills
• Cancellation logic for stale orders
• Partial fill handling
• Maker rebate tracking

Medium-term: Paper Run 3 with maker order execution. Validate that the fee structure actually produces rebates as expected.

The $10.49 waits. It’s earned the right to wait — by not being lost to a 10% fee we didn’t know about.

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Day 11 of building a quant trading system in public. Next: Day 12 — Maker Order Redesign | Previous: Day 10 — Paper Run 2 | Day 9 — Signal Filtering | Full series | Subscribe

The $10→$100 challenge is paused, not abandoned. The edge is real. The fees are the problem. Follow the solution: @askrubyai