Create op-supervisor.mdx

pages/stack/interop/op-supervisor.mdx

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+---
+title: OP-Supervisor
+lang: en-US
+description: Learn the basics of OP-Supervisor.
+---
+
+import { Callout, Tabs, Steps } from 'nextra/components'
+
+# OP-Supervisor
+
+<Callout>
+  Interop is currently in active development and not yet ready for production use. The information provided here may change. Check back regularly for the most up-to-date information.
+</Callout>
+
+`op-supervisor` is a critical service designed to verify cross-chain messages and manage the safety of interoperability between different chains in the OP Stack. It acts as a hub for indexing data that every `op-node` needs to cross-verify with other chains.
+
+## Features and benefits
+
+*   Enables secure cross-chain message passing on the Superchain
+*   Provides a centralized point for managing interoperability data
+*   Reduces the complexity and cost of operating individual nodes
+*   Supports multiple networks simultaneously
+*   Offers potential for public endpoints to aid in node synchronization
+
+## Major components
+
+### Cross-chain message verification
+
+Verifies messages between different chains in the OP Stack, reducing the risk of invalid or malicious cross-chain interactions.⁠ It centralizes the verification process, which reduces the complexity and cost of operating individual nodes⁠.⁠
+
+*   `op-geth`: queries `op-supervisor` during block-building to verify if a message is sufficiently safe to include. This process involves checking each executing message and potentially undoing transactions if conflicts or unknown states are encountered.
+*   `op-node`: queries cross-chain safety information and coordinates safety updates between OP stack nodes and `op-supervisor`. It uses the API provided by `op-supervisor` to perform actions like:
+    *   Updating and retrieving various safety levels
+    *   Checking and returning the `cross-unsafe` head for a given chain
+    *   Attempting to promote a block to `cross-safe` status
+    *   Attempting to finalize an L2 block based on L1 finality
+
+### Safe data indexing and management
+
+Acts as a hub for indexing data that every `op-node` needs to cross-verify with other chains, centralizing the process of managing interoperability data. Maintains the integrity of cross-chain interactions by tracking safety changes⁠ across the Superchain, ensuring consistent application of invalid dependency resolutions. ⁠
+
+`op-supervisor` indexes two types of cross-chain dependencies:
+
+*   Interop messages (events): `op-supervisor`maintains an events-index per L2 chain, which determines message-dependencies to check if blocks are safe
+*   L1 DA (data availability) batches: `op-supervisor`maintains a DA safety-index per L2 chain, which helps determine how to rewind L2 chains to resolve invalid dependencies
+
+### API for cross-chain safety
+
+Provides an interface for `op-node` to query cross-chain safety information and coordinate safety updates between OP stack nodes and `op-supervisor⁠⁠`. OP-Supervisor uses a global read API to determine **message safety** and **block safety,** utilizing both the events index and the safety index (See op-supervisor's [safe data indexing](#safe-data-indexing-and-management)). The API is designed to handle potential L1 reorgs that can affect the validity of cross-chain messages⁠.
+
+Key API methods include:
+
+| Method               | Description                                                                              |
+| -------------------- | ---------------------------------------------------------------------------------------- |
+| `ExchangeSyncStatus` | Updates and retrieves various safety levels (LocalUnsafe, CrossUnsafe, LocalSafe, etc.)⁠ |
+| `TryCrossUnsafe`     | Checks and returns the cross-unsafe head for a given chain⁠⁠​                            |
+| `TryCrossSafe`       | Attempts to promote a block to cross-safe status⁠⁠​                                      |
+| `TryFinalize`        | Attempts to finalize an L2 block based on L1 finality⁠                                   |
+
+### RPC access to all chains
+
+The `op-supervisor` requires RPC access to all chains in the dependency set. This allows `op-supervisor` to verify cross-chain messages and sync data across multiple networks simultaneously, such as OP Mainnet and Base nodes using the same instance.
+
+Benefits of this approach:
+
+*   Cost-effective: Running `op-supervisor` is cheaper than running a full node for each chain in the dependency set.
+*   Scalability: As the number of chains in the Superchain grows, `op-supervisor` can handle the increasing complexity of cross-chain interactions.
+*   Improved reliability: It enables a more redundant setup, which is good for stability in the growing ecosystem.
+
+## Next steps
+
+*   Want to learn more? Read our guide on the anatomy of a [cross-chain message](/stack/interop/cross-chain-message) or check out this [interop design video walk-thru](https://www.youtube.com/watch?v=FKc5RgjtGes).
+*   For more info about how OP Stack interoperability works under the hood, [check out the specs](https://specs.optimism.io/interop/overview.html).