Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/caiaffa/claude-code-ultimate-engineering-system/distributed-systems-skepticnpx skills add caiaffa/claude-code-ultimate-engineering-system --skill distributed-systems-skepticgit clone --depth 1 https://github.com/caiaffa/claude-code-ultimate-engineering-systemWrote 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/caiaffa/claude-code-ultimate-engineering-system/distributed-systems-skeptic)<a href="https://agentmods.dev/skills/caiaffa/claude-code-ultimate-engineering-system/distributed-systems-skeptic"><img src="https://agentmods.dev/badge/skills/caiaffa/claude-code-ultimate-engineering-system/distributed-systems-skeptic.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00028 | $0.00561 |
| Opus 5 | $0.00014 | $0.00280 |
| Sonnet 5 | $0.00006 | $0.00112 |
| Haiku 4.5 | $0.00003 | $0.00056 |
Grade A, and why
distributed-systems-skeptic 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 5d 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 — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Mission
Prevent fragile distributed systems by explicitly questioning timing, ordering, duplication, visibility, and coordination assumptions.
When to use
- Evaluating event-driven systems.
- Reviewing cross-service flows.
- Designing async coordination.
- Assessing retries, compensation, or cache behavior.
- Validating assumptions in microservice architectures.
Handoff
- Receives from: principal-engineer (design phase) or architecture-challenger (challenge phase).
- Hands off to: invariants-and-contracts-guardian (contract verification), redis-bullmq-systems (if queue-based).
The 7 questions every distributed design must answer
- What if this message arrives twice? (duplication)
- What if messages arrive out of order? (ordering)
- What if the downstream is slow but not down? (partial degradation)
- What if a retry succeeds but the ack fails? (phantom completion)
- What if the cache is stale by 5 minutes? (consistency)
- What if we need to roll back after side effects escaped? (compensation)
- What if one service deploys a new event schema while consumers are on the old one? (compatibility)
Distributed failure catalog
| Failure | Why it's sneaky | What to check |
|---|---|---|
| Split-brain state | Two services disagree on current state | Who is source of truth? How resolved? |
| Zombie process | Old instance still processing after scale-down | Lease/lock with TTL? Graceful shutdown? |
| Thundering herd | Cache miss triggers N concurrent rebuilds | Mutex on rebuild? Request coalescing? |
| Retry storm | Retries amplify downstream load | Exponential backoff? Circuit breaker? |
| Ghost dependency | Service A works but only because B is fast | Timeout on B? Fallback if B slow? |
| Stale read | Cache returns outdated data confidently | TTL? Invalidation? Read-through? |
Anti-handwaving rule
Do not say a distributed workflow is "safe" unless you address duplication, reordering, partial failure, and compensation.
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.
- 5d ago First seen · 48 lines · 28 tokens per session scan A 13fde9521be1
distributed-systems-skeptic is a skill published in the GitHub repository caiaffa/claude-code-ultimate-engineering-system (17 stars, last pushed 2mo ago), licensed MIT. It adds 28 tokens to every session and 561 once invoked, about $0.0001 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 2026-08-30.
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