set_code
Call v101 → current #2Set the new runtime code with safety checks (root only).
View calls on chainCall Workflow
This diagram shows the call execution flow: starting with set_code, passing through validation
(signature, nonce, mortality, fee payment), then pre-dispatch checks, followed by dispatch which emits events: CodeUpdated and modifies storage: LastRuntimeUpgrade, and finally post-dispatch where ExtrinsicSuccess is emitted and fees are settled.
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Used by: validatorsdevelopers
The Big Picture
This is how Substrate chains upgrade without forking. The runtime is stored on-chain as WASM.
Use Cases
- Deploy runtime upgrades
- Add new features
- Fix bugs
From Chain Metadata
Set the new runtime code. ## Complexity `O(C + S)` where `C` length of `code` and `S` complexity of `can_set_code`
Input Parameters
| # | Name | Type | Description |
|---|---|---|---|
| 0 | code | Vec<u8> Vec | code (Vec<u8>) |
Permissions
Origin
Unknown
Required Role
Requirements
- Caller is root/sudo
- Valid WASM code
- Spec name matches
- Spec version increases
Effects
Events Emitted
Storage Modified
Postconditions
- New runtime code deployed
- CodeUpdated event emitted
Side Effects
- All chain behavior may change
- Nodes need compatible software
Code Examples
import { createClient, Binary } from "polkadot-api";
import { getWsProvider } from "polkadot-api/ws";
import { sub } from "@polkadot-api/descriptors"; // generated by: npx papi add sub -w wss://entrypoint-finney.opentensor.ai:443
const client = createClient(getWsProvider("wss://entrypoint-finney.opentensor.ai:443"));
const api = client.getTypedApi(sub);
// Build set_code call (typed, named args)
const code = Binary.fromOpaque(new Uint8Array(0));
const tx = api.tx.System.set_code({
code,
});Runtime Info
- Pallet Index
- 0
- Call Index
- 2
- First Version
- v101
- Current Version
- v472