Borrowing it
Nothing to install: this file belongs to nklisch/claude-code-modes. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/nklisch/claude-code-modes/main/.claude/skills/sync-upstream/SKILL.mdgit clone --depth 1 https://github.com/nklisch/claude-code-modesWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/nklisch/claude-code-modes/sync-upstream)<a href="https://agentmods.dev/skills/nklisch/claude-code-modes/sync-upstream"><img src="https://agentmods.dev/badge/skills/nklisch/claude-code-modes/sync-upstream/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/nklisch/claude-code-modes/sync-upstream"><img src="https://agentmods.dev/badge/skills/nklisch/claude-code-modes/sync-upstream.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00083 | $0.01669 |
| Opus 5.5 | $0.00033 | $0.00668 |
| Sonnet 5.5 | $0.00017 | $0.00334 |
| Haiku 4.5 | $0.00008 | $0.00167 |
Grade A, and why
sync-upstream scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 146 lines — stays where its author put it; the contents beside it link to each section on GitHub.
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"))
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2mo ago First seen · 146 lines · 83 tokens per session scan A 31419909999b
sync-upstream is a skill published in the GitHub repository nklisch/claude-code-modes (117 stars, last pushed 29d ago), licensed MIT. It adds 83 tokens to every session and 1,669 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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