> For the complete documentation index, see [llms.txt](https://docs.symm.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.symm.io/trader-documentation/building-a-trading-bot/part-1-one-time-on-chain-setup/bind-the-sub-account-to-a-partyb.md).

# Bind the sub-account to a PartyB

Symmio core's `sendQuote` usually runs a Muon signature check on a `SingleUpnlAndPriceSig` parameter, unless the trading account is bound to a specific PartyB, in which case the check is skipped. The solver's instant-trade flow ships an empty `upnlSig` placeholder in the calldata it sends on-chain (it has no way to inject a fresh Muon sig into the EIP-712 op you signed), so without a bind your `executeTemplate` call reverts on-chain with `"LibMuon: Expired signature"`. That surfaces on the notifications feed as `SendQuoteTransaction` / `action_status = failed` / `error_code = 2000`.

Binding fixes this permanently for the sub-account. It pins the sub-account to the deployment's hedger and tells the core "I'm not using Muon oracles for this account; trust the PartyB."

**Signed by.** Owner EOA. The call goes to the AccountLayer's `_call(account, callDatas[])`, because [`bindToPartyB` ](https://intent.symmscan.com/inspector/hyperevm/diamond?method=0xcf462cb2)lives on the Symmio core and the core needs to see the *sub-account* as `msg.sender`. `_call` is the AccountLayer's mechanism for forwarding calls with the right signer context.

**Calldata to encode for the inner call:**

```
selector  = 0xcf462cb2                        // bindToPartyB(address)
arguments = abi.encode(address: hedger)
```

So the actual outer call is:

```
AccountLayer._call(
    account   = subAccount,
    callDatas = [ 0xcf462cb2 || abi.encode(hedger) ]
)
```

After it lands, sanity-check by reading [`Symmio.getBindState(subAccount)`: `status == 1`](https://intent.symmscan.com/inspector/hyperevm/diamond?method=0xa8eda21b) means bound. Once done, leave it alone. There's a `requestToUnbindFromPartyB` flow with a cooldown if you ever need to switch solvers, but you almost never will.


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