Upstream Pin

Every "original code reference" in this curriculum is anchored to a single, frozen snapshot of the real vLLM source tree so that path:line citations stay reproducible even as upstream moves on.

Contents

• Re-create the exact tree
• How citations are written
• Why pin at all?
• Bumping the pin (later)

Re-create the exact tree

git clone --depth 1 --branch v0.22.1 https://github.com/vllm-project/vllm.git upstream
cd upstream && git rev-parse HEAD   # must print 0decac0d96c42b49572498019f0a0e3600f50398

How citations are written

Throughout the phases you will see references like:

vllm/v1/core/sched/scheduler.py:312 @ 0decac0 — Scheduler.schedule()

• The path is relative to upstream/.
• The line number is valid only at the pinned SHA. If you check out a newer vLLM, open the file and search for the named symbol (the function/class is given) instead of trusting the line number.
• @ 0decac0 is the short SHA, a reminder that the snapshot is frozen.

Why pin at all?

vLLM merges dozens of PRs per day. A line number that is correct today is wrong next week. Pinning is the same discipline real maintainers use when they write design docs and bug reports: always cite a commit, never "main". When you eventually contribute upstream (Phase 19), you will cite commits in exactly this way in your PR descriptions and issue reports.

Bumping the pin (later)

When you want to refresh the curriculum against a newer vLLM:

1. Re-clone at the new tag, update the table above.
2. Re-run the path:line spot-check in each phase's 01-deep-dive.md.
3. Note behavioral changes in a CHANGES.md per phase — diffing how the engine evolved is itself one of the most instructive exercises in this whole course.