[Skill] upstream-sync: Sync ATOM with vLLM upstream changes

[sunway513]

Skill

upstream-sync

Priority: P2 — Important for staying current with vLLM

Motivation

ATOM is a fork of vLLM with AMD-specific optimizations. Upstream vLLM moves fast (multiple merges per day), and falling behind makes rebasing increasingly painful. Key challenges: ATOM patches touch the same files as upstream (attention, model runners, quantization), ROCm-specific code paths diverge from CUDA paths, and some upstream changes break ATOM's custom operators. A systematic sync skill would reduce the manual effort and risk of merge conflicts.

What This Skill Should Do

1. Fetch upstream changes — Pull latest commits from vLLM upstream since last sync point. Categorize commits by area: attention, model runner, quantization, scheduler, API, other.
2. Identify relevant commits — Flag commits that touch files ATOM has patched. Rank by conflict risk (high: same function modified, medium: same file, low: different file).
3. Detect breaking changes — Check for API changes in classes ATOM extends (e.g., ModelRunner, Attention backend interfaces). Flag renamed/removed functions, changed signatures, new required parameters.
4. Generate merge plan — Produce a prioritized list of commits to cherry-pick or rebase, grouped by risk level. For high-risk commits, show the specific conflict regions.
5. Validate after sync — Run ATOM's test suite and a basic serving smoke test to verify the sync didn't break anything. Compare output quality (cosine similarity) before and after.
6. Document sync — Generate a changelog of what was synced, what was skipped (and why), and any manual resolution needed.

Acceptance Criteria

• Can identify all upstream commits since a given sync point
• Correctly flags commits that conflict with ATOM patches
• Merge plan distinguishes high/medium/low risk commits
• Post-sync validation catches regressions (output quality, serving errors)
• Handles the ROCm Dockerfile divergence (ATOM builds from source, upstream uses wheels)
• Produces a human-readable sync report