# @usebutr/polkadot (/api/polkadot)



## Discovery [#discovery]

`discoverInjectedPolkadotAdapters(onAdapter, options?)` reads `window.injectedWeb3`
without prompting. It returns an unsubscribe function that cancels pending polls.
`InjectedPolkadotDiscoveryOptions` accepts `pollMs` (offsets in milliseconds;
default `[250, 750]`) and `target` (a host override for tests or iframes).

```tsx
import { createWalletSource } from "@usebutr/core";
import { discoverInjectedPolkadotAdapters } from "@usebutr/polkadot";

export const discovery = createWalletSource(discoverInjectedPolkadotAdapters);
```

`discoverPolkadotWalletStandardAdapters(onAdapter)` discovers wallets advertising
`polkadot:*` features. This path requires `@wallet-standard/app`.
`polkadotDiscoverer` is the `PlatformDiscoverer` used by `autoDiscovery()`:
injectedWeb3 is primary, and Wallet Standard is a deferred fallback when no
primary adapter has been found.

## Adapter builders [#adapter-builders]

* `buildInjectedPolkadotAdapter(extensionName, displayName, provider)` creates a
  Polkadot adapter. `connect()` enables the extension; construction does not.
* `buildPolkadotWalletStandardAdapter(wallet, registerDisconnector)` creates an
  adapter for a compatible Wallet Standard wallet, or returns `null`.

## Signer [#signer]

Injected adapters return `PolkadotSignerHandle` from `getSigner()`:

```tsx
import { isPolkadotSignerHandle } from "@usebutr/polkadot";
import type { ConnectedWallet } from "@usebutr/core";

export const getInjectedSigner = async (wallet: ConnectedWallet) => {
  const signer = await wallet.connector.getSigner();
  if (!isPolkadotSignerHandle(signer)) {
    throw new Error("This wallet does not expose an injectedWeb3 signer");
  }
  return signer.extension.signer;
};
```

The handle carries `address` (SS58), `extensionName` (the injected registry key),
and `extension` (the enabled provider). Wallet Standard adapters return the
Wallet Standard wallet instead. See the [PAPI integration](/integrations/polkadot)
for transaction construction and submission.

## Capabilities [#capabilities]

`resolveInjectedPolkadotCapabilities()` enables message signing, subscriptions,
and local chain switching. `resolveWalletStandardPolkadotCapabilities(input)`
uses advertised message-signing and event features plus the chain count.
Neither path advertises standalone transaction signing or sending.

Injected message signing wraps bytes in `<Bytes>…</Bytes>` before `signRaw`.
Verify the returned `signedMessage`, which contains that wrapper.

## Chains [#chains]

`POLKADOT_CHAINS` has `polkadot`, `kusama`, `paseo`, and `westend` entries;
`POLKADOT_CHAINS_LIST` is their array form. CAIP-2 identifiers use the
`polkadot:` namespace and the first 32 hexadecimal characters of the genesis
hash. Accounts retain their SS58 address.

`switchChain()` changes butr's local chain context; it does not switch an RPC
connection. Injected wallets default to Polkadot. Use Paseo for the demo.

## No RPC [#no-rpc]

Balance reads, receipts, extrinsic construction, and submission belong to your
chain client. Use `getSigner()` with PAPI; the adapter does not fetch chain metadata.

## Types [#types]

`InjectedPolkadotDiscoveryOptions`, `PolkadotSignerHandle`,
`WalletStandardPolkadotCapabilityInput`, `PolkadotSignMessageFeature`,
`PolkadotSignMessageInput`, and `PolkadotSignMessageOutput`.

**Source:** `packages/polkadot/src/index.ts`.