feat(ci): daily LLM-backed upstream awareness digest

[randomm]

Concept

A GitHub Action runs daily, compares anomalyco/dev to our last synced state, and uses an LLM to summarize what's new upstream — giving us awareness without automating the sync itself.

The sync process requires careful human + agent judgment and should remain manual. But knowing what upstream is doing is pure information that can be automated.

Why Not Full Automation

The /sync-upstream command handles the actual merge process well. Full automation of sync is risky because:

• Conflict resolution requires judgment about our fork-specific features
• Absorption decisions (should we adopt upstream's version?) need human input
• The process is too consequential to run unattended

What This Would Do

Daily GitHub Action:

1. Fetch anomalyco/dev
2. Get commits we haven't absorbed: git log anomalyco/dev ^origin/dev --oneline
3. Get changed file summary: git diff anomalyco/dev...origin/dev --stat
4. Feed to LLM (Anthropic API) with a prompt asking it to:
   • Categorize changes (bug fixes, new features, breaking changes, docs)
   • Flag anything touching files we've modified in our fork (cross-reference .fork-features/manifest.json)
   • Highlight anything that looks like it could conflict with our fork features
   • Identify anything worth absorbing proactively
5. Post digest as a comment on a pinned tracking issue (so it's searchable and notifies)

Open Questions

• Output destination: Comment on a pinned 'upstream watch' issue vs. new issue per digest vs. something else?
• LLM: Anthropic API directly in a Bun script (simplest, auditable) vs. opencode headless (dogfooding but complex in CI)
• Prompt quality: How to get genuinely useful signal vs. noise — needs careful prompt engineering
• Frequency: Daily may be too noisy if upstream is very active. Weekly?
• ANTHROPIC_API_KEY secret: Needs to be added to repo secrets

Implementation Sketch

.github/workflows/upstream-watch.yml   # Daily cron workflow
script/upstream-digest.ts              # Bun script: git diff + LLM call + post to GitHub

The script would be a simple Bun script calling Anthropic API directly — no framework, fully auditable.

References

• Our fork manifest: .fork-features/manifest.json (cross-reference for conflict flagging)
• Our sync command: .opencode/command/sync-upstream.md
• Related: [WS2] Implement shuvcode-style upstream sync automation #160 (upstream sync automation — decided NOT to automate the sync itself, only awareness)

Status

Draft — concept agreed, implementation not yet designed. Resolve open questions before starting.