fix(ci): prevent sccache from evicting Rust target cache

[proerror77]

Summary

• disable GitHub sccache object-cache writes in CI, Ploy, and ACR Rust jobs
• keep the per-job sccache wrapper and rust-cache target archive
• pin the cache policy in the existing CI and ACR contract tests

Root cause

The repository was writing thousands of sccache objects into the same GitHub Actions cache quota as the large Rust target archive. The research target key (1.39 GiB) was evicted, so the main build restored no target cache and fell back to a cold compile.

Validation

• bash .github/scripts/test-select-rust-ci-scope.sh
• bash .github/scripts/test-acr-publish-workflow.sh
• bash -n .github/scripts/test-select-rust-ci-scope.sh .github/scripts/test-acr-publish-workflow.sh
• git diff --check

Out of scope

The tag-only release workflow remains unchanged because it has a pre-existing macos-15-intel actionlint runner-label failure; no production services, collectors, uploaders, OSS objects, or runtime state changed.

Issue relationship

None

[coderabbitai]

📝 Walkthrough

Walkthrough

The PR disables the GitHub Actions sccache backend across Rust, ACR, and Ploy workflows. Contract tests now require disabled backend settings and reject write-mode configuration.

Changes

sccache policy

Layer / File(s)	Summary
Core Rust workflow configuration .github/workflows/ci.yml, .github/workflows/release-rust.yml	Rust CI and release jobs disable GitHub Actions-backed sccache. Concurrency comments now reference the shared Rust target cache.
ACR and Ploy workflow configuration .github/workflows/acr-publish.yml, .github/workflows/ploy-ci.yml	ACR and Ploy jobs disable GitHub Actions-backed sccache. The research image job no longer sets SCCACHE_GHA_RW_MODE.
sccache contract validation .github/scripts/test-acr-publish-workflow.sh, .github/scripts/test-select-rust-ci-scope.sh	Contract tests require disabled GitHub Actions sccache settings and reject release or research image write-mode configuration.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• proerror77/monday#14: Introduced the ACR workflow whose sccache contract changes here.
• proerror77/monday#56: Added the Rust CI scoping workflow checks extended by this PR.
• proerror77/monday#711: Updated ACR workflow sccache configuration and contract tests.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description explains the change and validation, but it omits the required Change contract, Dependencies and merge order, Rollout and rollback, and Scope exception sections.	Add all missing template sections and include the required focused-validation counterexample, even if the values are None.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly states that the CI change prevents sccache from evicting the Rust target cache.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/rust-cache-quota

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: b5741b49c4

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[coderabbitai]

🧹 Nitpick comments (1)

.github/scripts/test-acr-publish-workflow.sh (1)

198-201: 🗄️ Data Integrity & Integration | 🔵 Trivial | ⚡ Quick win

Scope the cache-policy assertions to research-runner-binaries.

The grep -Fqx checks search the entire ACR workflow. They do not prove that RUSTC_WRAPPER, SCCACHE_GHA_ENABLED, mozilla-actions/sccache-action, and continue-on-error belong to the same job. A future job could satisfy these checks while research-runner-binaries loses the disabled backend.

Extract the research-runner-binaries block and run these assertions against that block.

Proposed test fix

+research_runner_block=$(awk '
+  /^  research-runner-binaries:/ { found=1; next }
+  found && /^  [a-z0-9-]+:/ { exit }
+  found { print }
+' "$workflow")
-grep -Fqx '      RUSTC_WRAPPER: sccache' "$workflow"
-grep -Fqx '      SCCACHE_GHA_ENABLED: "false"' "$workflow"
+grep -Fqx '      RUSTC_WRAPPER: sccache' <<<"$research_runner_block"
+grep -Fqx '      SCCACHE_GHA_ENABLED: "false"' <<<"$research_runner_block"
-grep -Fqx '        uses: mozilla-actions/sccache-action@v0.0.10' "$workflow"
-grep -Fqx '        continue-on-error: true' "$workflow"
+grep -Fqx '        uses: mozilla-actions/sccache-action@v0.0.10' <<<"$research_runner_block"
+grep -Fqx '        continue-on-error: true' <<<"$research_runner_block"

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.github/scripts/test-acr-publish-workflow.sh around lines 198 - 201, Update
the assertions in test-acr-publish-workflow.sh to first extract the
research-runner-binaries job block from the workflow, then run all four grep
-Fqx cache-policy checks against that extracted block rather than the entire
workflow. Preserve the existing assertions for RUSTC_WRAPPER,
SCCACHE_GHA_ENABLED, mozilla-actions/sccache-action, and continue-on-error.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In @.github/scripts/test-acr-publish-workflow.sh:
- Around line 198-201: Update the assertions in test-acr-publish-workflow.sh to
first extract the research-runner-binaries job block from the workflow, then run
all four grep -Fqx cache-policy checks against that extracted block rather than
the entire workflow. Preserve the existing assertions for RUSTC_WRAPPER,
SCCACHE_GHA_ENABLED, mozilla-actions/sccache-action, and continue-on-error.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 6f264aaa-c734-4351-90c4-29f3a15dc9ab

📥 Commits

Reviewing files that changed from the base of the PR and between 2a979c4 and b5741b4.

📒 Files selected for processing (6)

• .github/scripts/test-acr-publish-workflow.sh
• .github/scripts/test-select-rust-ci-scope.sh
• .github/workflows/acr-publish.yml
• .github/workflows/ci.yml
• .github/workflows/ploy-ci.yml
• .github/workflows/release-rust.yml