Add automatic .serena/cache caching for workflows with Serena tool

[Copilot]

Workflows using the Serena tool now automatically cache .serena/cache to preserve language server state between runs.

Implementation

• Cache step generation (pkg/workflow/serena_cache.go)

  • isSerenaEnabled(): Detects Serena in ParsedTools or legacy Tools map
  • generateSerenaCacheStep(): Injects cache step after checkout

• Cache configuration

  • Path: .serena/cache
  • Key: serena-${{ runner.os }}-${{ github.run_id }}-${{ github.run_attempt }}
  • Restore keys: serena-${{ runner.os }}- (prefix match for last-wins behavior)
  • save-always: true ensures cache persists on workflow failure
  • continue-on-error: true handles missing directory gracefully

• Integration (pkg/workflow/compiler_yaml_main_job.go)

  • Called immediately after checkout step generation

Example output

- name: Checkout repository
  uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8
  with:
    persist-credentials: false
- name: Cache Serena
  uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830
  continue-on-error: true
  with:
    path: .serena/cache
    key: serena-${{ runner.os }}-${{ github.run_id }}-${{ github.run_attempt }}
    restore-keys: |
      serena-${{ runner.os }}-
    save-always: true

20 existing workflows with Serena automatically updated.

Original prompt

Update the compiler:

When the Serena took is enabled, the agent job should have a cache mounted at .serena/cache (after checkout). Ignore if folder does not exist.

The cache should be setup such that the last cache wins. Expires in 7d

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[pelikhan]

@copilot use resolution name cascade to simulate last-cache-wins