Batch and deduplicate action resolution across composite depths

[stefanpenner]

Summary

• Cache resolved actions across recursion depths — same action resolved once
• Batch-resolve sibling composites' sub-actions in one API call instead of N
• Defer pre/post step registration until after recursion (fixes HasPre/HasPost correctness)

Internal workflow with ~30 composites: ~20 resolve API calls → 3-4. Also reduces 429s (#4232).

Fixes #3731

Other possibilities

• Note a more aggressive approach exists here, which performs even better (~2x faster in my tests) when there are more nested downloads, but it's a larger refactor. Which may or may not be appealing to the maintainers.

Smoke test results

Tested with a self-hosted runner built from this branch vs stock (main), using a 50-action composite tree across 6 repos with 5 depth levels.

Action graph:

workflow → 10× L1 composites + 5 leaves (15 top-level steps)
  L1 (×10) → 1 leaf + 3 L2 composites (heavy cross-referencing)
  L2 (×10) → 1 leaf + 3 L3 composites
  L3 (×10) → 2 leaves + 2 L4 composites (cross-repo refs to 5 shard repos)
  L4 (×10) → 3 leaves (cross-repo refs)

Results (run)

	Stock runner (main)	This PR
Resolve API calls	311	4
Resolution time	70.6s	8.2s

• 78× fewer API calls, 8.6× faster action resolution
• Output parity confirmed (3845 leaf-action log lines in both runners)
• All composites resolved and executed at all 5 depth levels
• Cross-repo references resolved correctly
• Dedup verified: same owner/repo@ref never re-resolved across depths
• Batching verified: distinct repos at the same depth batched into 1 call

Earlier run (single-repo, same-ref tree)

Run: 311 → 1 resolve calls (all 50 actions shared the same owner/repo@ref lookup key, so the cache eliminated every call after the first).

Test plan

• 4 new L0 tests covering batching, cross-depth dedup, multi-top-level, and nested containers
• Smoke test with self-hosted runners: 50-action/5-depth/6-repo composite tree (see above)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR optimizes action resolution in composite action trees by batching and deduplicating API calls across recursion depths. Instead of resolving sub-actions one composite at a time (N API calls), it collects all sub-actions at each depth level and resolves them in a single batch call, with a cross-depth cache to avoid re-resolving the same action. It also defers pre/post step registration until after recursion completes.

Changes:

• Introduce a stack-local resolvedDownloadInfos cache to deduplicate action resolution across composite depths, and a new ResolveNewActionsAsync helper that skips already-cached actions
• Collect composite sub-actions into a nextLevel list and batch-resolve them before recursing per parent group
• Defer pre/post step registration to after recursion so that HasPre/HasPost reflect the full subtree

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/Runner.Worker/ActionManager.cs	Core optimization: adds resolution cache, batch pre-resolution of next-level actions, deferred pre/post registration, and new ResolveNewActionsAsync helper
src/Test/L0/Worker/ActionManagerL0.cs	5 new L0 tests covering batching, cross-depth dedup, multi-top-level, nested containers, and parallel downloads

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[Copilot]

Pull request overview

This PR optimizes action resolution in the GitHub Actions runner by introducing batching and cross-depth deduplication for composite action resolution. Instead of making individual API calls per composite action at each recursion depth, sub-actions from all composites at the same depth are collected and resolved in a single batch API call. A stack-local cache ensures the same owner/repo@ref is only resolved once even if it appears at multiple depths in the composite tree. Pre/post step registration is deferred until after recursion to ensure HasPre/HasPost reflect the full subtree.

Changes:

• Added a case-insensitive resolvedDownloadInfos dictionary that caches resolved action download info across recursion depths, with a ResolveNewActionsAsync helper that skips already-cached actions
• Refactored PrepareActionsRecursiveAsync to collect composite sub-actions into a nextLevel list, batch-resolve them in one API call, then recurse per-parent group — moving pre/post step registration after recursion
• Added 5 new L0 tests covering batching, cross-depth dedup, multiple top-level actions, nested containers, and parallel downloads

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Runner.Worker/ActionManager.cs	Core optimization: batch resolution cache, ResolveNewActionsAsync helper, deferred pre/post registration
src/Test/L0/Worker/ActionManagerL0.cs	5 new tests validating batching, deduplication, multi-action, nested container, and parallel download scenarios

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