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+# Foundry Versioning Policy
+
+This document outlines the process for proposing and implementing Foundry version updates in the
+OP Stack codebase.
+
+## Unified Foundry Version
+
+The OP Stack codebase maintains a single, unified Foundry version across all components. This ensures
+consistency, simplifies maintenance, and reduces the risk of version-related issues. Foundry is a
+critical dependency in our supply chain, and if compromised can have severe consequences.
+
+**Important**: New Foundry versions must not be introduced to any part of the codebase without
+going through the formal version update proposal process outlined in this document.
+
+## Update Process
+
+1. **Minimum Delay Period**: A new Foundry version must be at least 3 month old before it can be
+   considered for adoption. 3 Months is a good minimum delay period to allow for the community to use the new version and for any security vulnerabilities to be discovered and addressed.
+2. Only stable releases are recommended to be proposed for adoption.
+3. Nightly builds must only be considered for adoption if it includes a bug fix that addresses a non-trivial security vulnerability. This path does not need to follow the 3 month delay period, but must fill out the `notable bug fixes` section with rationale for why a nightly release is required.
+4. **Proposal Submission**: Before any Foundry version upgrades are made, a detailed proposal must
+   be submitted as a pull request to the [`ethereum-optimism/design-docs`][1] repository in a
+   `foundry/` subfolder, following the standardized format outlined below. This applies to the monorepo, superchain-ops, and any other repositories that use Foundry.
+5. **Review and Approval**: A dedicated review panel that must consist of **at least 2 members of the security team** will assess the proposal based on the
+   following criteria:
+   - Is the Foundry version at least 3 month old?
+   - Does the proposed upgrade provide clear value to the codebase?
+   - Do any new features or bug fixes pose an unnecessary risk to the codebase?
+   - Are there any security vulnerabilities addressed by this version?
+6. **Implementation**: If the proposal receives unanimous approval from the review panel, the
+   Foundry version upgrade will be implemented across the entire OP Stack codebase, including:
+   - The monorepo (`mise.toml` and `op-deployer/pkg/deployer/forge/version.json`)
+   - The `superchain-ops` repository
+7. The PR that implements the bump MUST include a reference to the approved, merged design document that approves that foundry version for usage.
+
+## Proposal Submission Guidelines
+
+To submit a Foundry version upgrade proposal, create a new pull request to the
+[`ethereum-optimism/design-docs`][1] repository, adding a new file in the `foundry/` subfolder.
+Please use the [Foundry update proposal format][2].
+Ensure that all sections are filled out comprehensively. Incomplete proposals may be delayed or
+rejected.
+
+## Review Process
+
+The review panel will evaluate each proposal based on the criteria mentioned in the "Review and
+Approval" section above. They may request additional information or clarifications if needed.
+
+## Implementation
+
+If approved, the Foundry version upgrade will be implemented across the entire OP Stack codebase.
+This process will be managed by the person who submitted the proposal to ensure consistency and minimize potential
+issues. The upgrade will apply to all components simultaneously, including:
+
+- `mise.toml`: Update `forge`, `cast`, and `anvil` version entries
+- `op-deployer/pkg/deployer/forge/version.json`: Update the `forge` version and corresponding
+  checksums for all supported platforms
+- `superchain-ops` repository: Update Foundry version configuration
+
+All version updates must be synchronized across these locations to maintain consistency.
+
+<!-- References -->
+
+[1]: https://github.com/ethereum-optimism/design-docs
+[2]: https://github.com/ethereum-optimism/design-docs/tree/main/assets/foundry-update-template.md