sibling-sync

sibling-sync is a skill for Claude Code from voxpelli/claude-beads. It costs 349 tokens per session (13,468 once invoked), scanned A, original, MIT.

A read-only checker for keeping related projects' SYNERGY and UPSTREAM files in agreement. It compares registered sibling projects and reports differences, missing reciprocal entries, outdated matches, and status differences.

In plain words
What is it for?
Use it to compare sibling projects, find entries missing on one side, identify stale shared records, and optionally confirm reciprocal updates.
Why use it?
It makes cross-project drift visible without changing files or requiring direct tracker-to-tracker coordination.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions subagents; names the AskUserQuestion tool; mentions Claude Code.

Not installable: its command points at a path on the author’s own machine, so it runs nowhere else. The line is /Users/.../vp-claude.

Part of the vp-beads plugin — 8 skills, 1 agent, 3 hooks shipped together

Good fit Use it to compare sibling projects, find entries missing on one side, identify stale shared records, and optionally confirm reciprocal updates.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add voxpelli/claude-beads
Claude Code
/plugin install vp-beads

Made for: Claude Code.

Or install vp-beads, the plugin that ships this one along with the rest of its 8 skills, 1 agent, 3 hooks.

Wrote 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.

agentmods badge for sibling-sync

README.md
[![agentmods](https://agentmods.dev/badge/skills/voxpelli/claude-beads/sibling-sync.svg)](https://agentmods.dev/skills/voxpelli/claude-beads/sibling-sync)
Your own site
<a href="https://agentmods.dev/skills/voxpelli/claude-beads/sibling-sync"><img src="https://agentmods.dev/badge/skills/voxpelli/claude-beads/sibling-sync.svg" alt="Measured on agentmods" height="20"></a>
Per session 349 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 13,468 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00349 $0.13468
Opus 5 $0.00175 $0.06734
Sonnet 5 $0.00070 $0.02694
Haiku 4.5 $0.00035 $0.01347

Measured 8d ago against content hash e4f2bb8f943b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

sibling-sync 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 8d 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.

skills/sibling-sync/SKILL.md · 916 lines

How it starts

The opening of the file, as written. The whole thing — 916 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Sibling Sync

Bilateral reconciliation of SYNERGY-*.md and UPSTREAM-*.md files between this project and its sibling vp-* projects. Read-only by default — surfaces drift, reciprocal gaps, stale-aligned rows, and status drift across sides without mutating anything. The opt-in --auto-reciprocate flag writes reciprocal entries to the sibling's SYNERGY file via per-entry confirmation.

Companion to /vendor-sync (which handles upstream → project drift); this skill handles peer-to-peer drift between siblings registered in .claude/synergy-registry.json.

Design Rationale

The bd v1.0.0 Integration Charter (gastownhall/beads@5d524cf7:docs/INTEGRATION_CHARTER.md) explicitly punts cross-tracker orchestration out of bd's scope: bd will never grow a feature that routes a cross-project item from project A's tracker to project B's tracker. /sibling-sync is exactly the workflow-automation layer the Charter defers to external tools — file-based reconciliation between sibling vp-* projects, mediated by registries and confirmation prompts rather than synchronous tracker calls.

This mirrors the rationale already cited by /synergy-tracker for keeping cross-project state in SYNERGY-*.md plus Basic Memory rather than in bd.

Cross-skill boundaries

/sibling-sync is a comparison and reconciliation layer that sits alongside the per-side logging skills. It owns nothing in Basic Memory and nothing on this project's side of the SYNERGY/UPSTREAM files.

  • Does NOT write SYNERGY entries on this project's side. /synergy-tracker workflow 1 (Log a synergy entry) owns logging on this side.
  • Does NOT pull upstream subtrees. /vendor-sync owns subtree pulls and the upstream → project drift workflow.
  • Does NOT write Basic Memory notes. /synergy-tracker workflow 5 (Promote to Basic Memory) owns ## Cross-Project Synergy writes to sibling entity notes; /upstream-tracker workflow 6 (Promote to Basic Memory) owns ## Upstream Friction writes. Basic Memory write tools are intentionally absent from this skill's allowed-tools.
  • Does NOT write ## Trend Reviews entries to SYNERGY files. Those belong to /synergy-tracker workflow 4 (Trend review (quarterly)). Even under --auto-reciprocate, /sibling-sync only mirrors content entries into reciprocal sections — never trend-review summaries.
  • Stale-row detection is INLINE here for the threshold values used during comparison runs. The canonical staleness-threshold definition lives in /synergy-tracker workflow 4 (Trend review (quarterly)) — workflow 2 (Sync sibling SYNERGY) below cites it. Per RETRO-10 YAGNI guard: extract this to a shared helper only when a third skill needs the same logic.
  • Surfacing reciprocal-friction findings is in scope; acting on them is not. Workflow 3 (Sync sibling UPSTREAM) Mode B (see below) reads the sibling's UPSTREAM-<this-project>.md to surface friction the sibling tracks about this project. Filing the resulting work as bugs/features/opportunities on this side is /upstream-tracker workflow 1 (Log a new entry)'s job. Annotating the sibling's entry as resolved is /upstream-tracker workflow 3 (Resolve an entry)'s job, performed on the sibling's side. /sibling-sync reports only.
  • Orchestrator role for follow-up actions (v0.14.0). Workflows 2 (Sync sibling SYNERGY) and 3 (Sync sibling UPSTREAM) end with a per-sibling action menu (see "Action-menu protocol" below) that delegates writes to the owning skill (/vp-beads:synergy-tracker, /vp-beads:upstream-tracker) via the Skill tool, or runs bd create directly for beads issues. /sibling-sync still owns nothing in Basic Memory and nothing in this project's SYNERGY/UPSTREAM files — ownership boundaries are unchanged.

Read the full file on GitHub · 916 lines

Changes

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.

  1. 8d ago First seen · 916 lines · 349 tokens per session scan A e4f2bb8f943b

Subscribe to this mod's changes

sibling-sync is a skill published in the GitHub repository voxpelli/claude-beads (2 stars, last pushed 24d ago), licensed MIT. It adds 349 tokens to every session and 13,468 once invoked, about $0.0017 per session on Opus 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 2026-08-31.

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