SideSwap atomic swap fails when swapping USDt to L-BTC

[jan3-agent]

Description

When attempting to swap USDt to L-BTC using SideSwap's atomic swap feature, the transaction fails with an internal verification error. The agent successfully retrieves a price quote, but when it attempts to execute the swap, SideSwap returns a transaction that doesn't include the expected L-BTC amount, causing the agent to correctly refuse to sign the transaction to protect the user's funds.

Steps to reproduce

1. Ask the agent to swap USDt into L-BTC using SideSwap's atomic swap
2. Agent fetches a price quote successfully
3. Agent attempts to execute the swap
4. SideSwap returns a transaction without the expected L-BTC amount
5. Agent refuses to sign the transaction

Expected vs actual

• Expected: Agent executes the swap and receives the quoted L-BTC amount
• Actual: SideSwap returns a transaction with a mismatched amount; agent verification fails and refuses to sign

Notes

• No funds are at risk — the verification happens before any transaction is signed
• Reverse direction (L-BTC → USDt) has not been tested yet
• Related: [QA] Manual Testing — New Integrations in Agentic-AQUA #41 (QA testing)

[andycreed0x]

Manual QA findings — 2026-05-25

Reproduced consistently during the real-wallet smoke test run (prompt_test_send_real_sideswap.md).

Environment

• Wallet: prompt_wallet_20260525_2 (mainnet)
• USDt balance: ~59.30 USDt (5,929,940,800 sats)
• L-BTC balance: 642 sats

Reproduction (two consecutive attempts)

Attempt 1

sideswap_quote(asset_id=USDt, send_amount=1_000_000_000, send_bitcoins=False)
→ recv_amount: 12,777 sats L-BTC @ $77,924/BTC

sideswap_execute_swap(send_amount=1_000_000_000, send_bitcoins=False, min_recv_amount=12777)
→ PsetVerificationError: PSET delivers 0 sats of recv_asset 6f0279e9…, expected exactly 12885 sats

Attempt 2 (fresh quote, ~30s later)

sideswap_quote → recv_amount: 12,794 sats @ $77,822/BTC

sideswap_execute_swap(min_recv_amount=12794)
→ PsetVerificationError: PSET delivers 0 sats of recv_asset 6f0279e9…, expected exactly 12897 sats

Observations

• The error is 100% reproducible — not a transient network issue.
• The dealer responds with a slightly higher recv_amount than the quote (e.g. 12,885 vs 12,777) — this is normal price movement and should pass min_recv_amount. The problem is that the verifier finds 0 sats of L-BTC in the PSET, not a slippage rejection.
• The reverse direction (L-BTC → USDt, send_bitcoins=True) is unaffected — the quote and PSET structure both work correctly; that path only failed here due to insufficient L-BTC balance (642 sats vs 5,000 needed).
• No funds were at risk — the verification fires before signing.

Hypothesis

The PSET verification logic likely uses different output-scanning logic depending on the swap direction. When send_bitcoins=False (asset → L-BTC), the verifier may be looking for the L-BTC output using the wrong index, blinding key, or asset-id comparison, causing it to find 0 sats even though the dealer included the correct output.

Suggested investigation: sideswap_execute_swap verification path in src/aqua/sideswap.py for the send_bitcoins=False branch.