sync-upstream

Sync Upstream

Keep prompts/base/, prompts/lean/, the prompt-bundle modifiers, and the model table in src/env.ts aligned with what Claude Code actually sends.

This is an investigation, not a checklist. The sections below describe what has to be true when you're done and the tools available to get there — how you sequence them is yours to judge. Two things are not yours to judge: confirm the target version before doing the work, and get changes approved before applying them.

What "aligned" means

Three prompt shapes exist upstream, assembled by one function that forks on a model-capability predicate. All three matter here:

Shape	Who gets it	Tracked in
standard head	models without lean_prompt	prompts/base/
lean head	models with lean_prompt	prompts/lean/
shared tail	everyone, both heads	duplicated in both bases
bundle sections	models with opus_5_prompt_bundle	prompts/modifiers/

Capabilities also drive --base auto, so the model table in src/env.ts is part of the sync, not a side note: a new flagship changes which base users get by default.

references/fragment-map.md holds the current local↔upstream mapping and the marker strings to find each piece. references/intentional-omissions.md holds every difference that is deliberate.

Ground truth and how to reach it

bun run scripts/extract-upstream-prompt.ts [version] pulls named prompt functions into upstream-prompts/. It is the fastest path for what it covers, which is the standard head and not much else. It does not extract the shared tail, the lean head, the bundle sections, or model capabilities.

For anything it misses, grep the release binary directly:

npm pack @anthropic-ai/claude-code-linux-x64@<version> && tar xzf *.tgz   # → package/claude

It's ~275 MB, so slice by byte offset in Python rather than running wide regexes:

data = open("package/claude","rb").read()
i = data.find(b"<marker text>")
print(data[i-4000:i+4000].decode("utf8","replace"))