Gatsby Core and React: Interoperability during Major Version Upgrades

Dependency Alignment and Cache Strategy

To avoid runtime conflicts during a major Gatsby upgrade, the recommended strategy is to strictly align the React version with the peer dependencies specified by the Gatsby core package. Bypassing these constraints using flags like --legacy-peer-deps or --force often leads to hydration mismatches, where the server-rendered HTML differs from the client-side initial render, causing unstable UI behavior.

Managing the React Boundary

Because Gatsby's internal rendering engine and the gatsby-plugin-image ecosystem are tightly coupled to specific React versions, any mismatch can cause silent failures in image processing or runtime crashes. To ensure interoperability:

• Verify the required React version by checking the peerDependencies section of the gatsby package in your node_modules.
• Update React and React-DOM simultaneously with the Gatsby core upgrade to ensure the rendering logic remains consistent across the boundary.
• Perform a production build and inspect the browser console for "Hydration failed" warnings, which are the primary indicator of version interoperability issues.

Build Cache Policy in Headless Environments

In headless CI/CD environments, the build cache (.cache and public directories) should be purged automatically when a version upgrade is detected. Preserving these artifacts across major versions is risky because they contain GraphQL schemas and build logic from the previous version that may be incompatible with the new core.

The only scenario for preserving the cache is during local development for the purpose of debugging a failed upgrade (e.g., comparing the previous schema state). For automated pipelines, a clean state is mandatory to prevent stale artifacts from causing non-deterministic build failures.

Verification Steps

To resolve a suspected version mismatch or cache corruption, execute the following scoped commands:

# Manually purge the cache and public folders
gatsby clean

# Reinstall dependencies to ensure peer alignment
rm -rf node_modules package-lock.json
npm install

Diagnostic Detail Needed: Are you utilizing a custom Gatsby SSR (Server-Side Rendering) configuration or a specific version of gatsby-plugin-image that deviates from the core version? This may require a more granular dependency override.