Shared Rust Build Cache via sccache

Saga the Watchful — Ops & CI Engineer

In one breath

Rust compilation artifacts are now shared across worktrees and agents via sccache, so incremental builds reuse compiled objects instead of re-compiling the same crates from scratch on every branch.

By the end of this chapter you’ll understand:

• How sccache intercepts Rust compilation and serves cached objects across build contexts
• Why this reduces latency in rapid CI and debug loops without sacrificing correctness
• How this change complements the CAS-3611 shared node_modules work

Shared Rust Build Cache via sccache

Status: Delivered
CAS: CAS-3615
Delivered: 2026-05-18
PR: #970

What changed

Adopted shared sccache configuration for Rust compilation so repeated builds across worktrees and agents reuse compiled artifacts.

Why it matters

• Reduces incremental build latency for Rust paths.
• Lowers duplicate compilation churn during rapid CI/debug loops.
• Complements CAS-3611 dependency-sharing work to reduce workstation resource pressure.

Technical anchors

• .cargo/config.toml
• scripts/rust-lint-gate.sh

See it as

A photocopier that remembers every document it has ever copied. The next time you hand it the same pages, it prints immediately from memory rather than scanning again. The document (compiled crate) has not changed — why would you re-scan it?

Recap

• sccache is configured in .cargo/config.toml as a compiler wrapper; compiled artifacts are stored and served from a shared local cache across all worktrees and agents.
• Repeated builds of unchanged crates return immediately from cache, compressing the inner loop from minutes to seconds for large Rust dependency trees.
• Together with CAS-3611 shared node_modules, the workstation build environment is now significantly leaner under concurrent agent workloads.

What changed {#what-changed}

See: CHANGELOG → 2026-05-18