fix(epoxy): reuse cached optimistic value

[NathanFlurry]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[NathanFlurry]

• fix(pegboard): isolate runner config dc lookup failures #4625 : 2 dependent PRs (#4626 , #4630 )
• docs(pegboard): note runner config upsert split write risk #4624
• fix(pegboard): unpack global runner config keys correctly #4623
• fix(pegboard-gateway): enforce tunnel message state #4622
• fix(pegboard-runner): clear terminal tunnel routes #4621
• fix(pegboard): skip protocol version keys in runner pool backfill #4620
• fix(pegboard): create missing normal runner configs #4619
• fix(epoxy): reuse cached optimistic value #4618 👈 (View in Graphite)
• main

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[railway-app]

🚅 Deployed to the rivet-pr-4618 environment in rivet-frontend

Service	Status	Web	Updated (UTC)
kitchen-sink	❌ Build Failed (View Logs)	Web	Apr 13, 2026 at 7:36 pm
frontend-cloud	❌ Build Failed (View Logs)	Web	Apr 13, 2026 at 2:16 am
website	❌ Build Failed (View Logs)	Web	Apr 13, 2026 at 2:16 am
mcp-hub	✅ Success (View Logs)	Web	Apr 13, 2026 at 2:15 am
ladle	❌ Build Failed (View Logs)	Web	Apr 13, 2026 at 2:15 am
frontend-inspector	❌ Build Failed (View Logs)	Web	Apr 13, 2026 at 2:15 am

[claude]

PR Review: fix(epoxy): reuse cached optimistic value

Overall: Correct bug fix, clean implementation.

What This Fixes

The original code had a subtle but serious bug in the optimistic cache path of read_local_value. After deserializing the raw DB bytes into a CachedValue, it extracted the inner value: Vec<u8> field and then called cache_key.deserialize(&value)? on it again, treating the inner payload bytes as if they were a second serialized CachedValue blob.

This would fail at runtime for any non-empty cache entry, making the optimistic read path effectively broken.

The fix correctly reconstructs CachedValue by reusing the already-extracted bytes and reading cache_value.version directly.

Rust validity: the if let Some(value) = cache_value.value pattern partially moves cache_value.value out of the struct. Accessing cache_value.version afterward is valid because version is a separate field. The fields are spelled out explicitly with no struct update syntax (..cache_value).

Confirmed correct by tracing the consumer in get_optimistic.rs, which does local_read.cache_value.and_then(|v| v.value). The fix ensures v.value is Some(bytes) as expected.

Cargo.lock

The lock file reflects a version bump from 2.2.1 to 2.3.0-rc.4 across packages (epoxy, pegboard, gasoline, etc.) and new transitive deps: napi/napi-derive/napi-sys (Node.js native addon support) and libsqlite3-sys (native SQLite). These are unrelated to the bug fix and appear to come from base branch changes merged in.

Suggestions

Test coverage: No test exercises the include_cache=true path where the cache contains a non-empty value. Given this was a silent failure before, a regression test would be valuable: write a value via the fanout path (so it lands in cache but not committed storage), call read_local_value(..., include_cache=true), and assert cache_value.value is Some with the expected bytes.

Tombstone path: When cache_value deserializes with value: None, the code falls through and returns LocalValueRead { value: None, cache_value: None }. This is unchanged from before, but worth confirming the cache tombstone case is handled correctly upstream.

PR description: The draft template is unfilled. Worth adding a short motivation note before merging.

No other issues. The fix is minimal, correct, and easy to reason about.

[MasterPtato]

Merge activity

• Apr 13, 8:40 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 13, 8:40 PM UTC: @MasterPtato merged this pull request with Graphite.