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 skills add randommonicle/claude-skills --skill lock-at-the-chokepointgit clone --depth 1 https://github.com/randommonicle/claude-skillsWrote 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/randommonicle/claude-skills/lock-at-the-chokepoint)<a href="https://agentmods.dev/skills/randommonicle/claude-skills/lock-at-the-chokepoint"><img src="https://agentmods.dev/badge/skills/randommonicle/claude-skills/lock-at-the-chokepoint/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/randommonicle/claude-skills/lock-at-the-chokepoint"><img src="https://agentmods.dev/badge/skills/randommonicle/claude-skills/lock-at-the-chokepoint.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00128 | $0.00630 |
| Opus 5 | $0.00064 | $0.00315 |
| Sonnet 5 | $0.00026 | $0.00126 |
| Haiku 4.5 | $0.00013 | $0.00063 |
Grade A, and why
lock-at-the-chokepoint 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 12d 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 — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Lock at the chokepoint
Three incidents that cost real money: a per-hook syncing ref plus per-screen network
listeners produced overlapping sync passes and every photo was analysed twice at doubled AI
cost; ~30 concurrent vision calls fired unawaited and blew the provider's per-minute org
limit; the server-side "already analysed?" check lost the race against its twin.
The rules
- Serialise at the shared module-level function every caller passes through — a module-level in-flight promise, not per-instance state. Guards in hooks, screens, or components multiply with their instances and each copy believes it is alone.
- A check-then-act guard is not a lock. Read-then-write ("is it already done? no → do it") protects sequential retries only; two simultaneous callers both pass the check. Prevent the duplicate at the source, or use an atomic claim (see outbound-side-effect-idempotency for the external-send variant).
- Cap fan-out at the single upstream chokepoint rather than trusting callers not to burst. One concurrency gate in the shared client wrapper throttles the whole app under a provider limit; per-call politeness does not survive a loop.
- Retry and resume loops: skip items already completed; classify failures transient (retry N, then give up) versus permanent (give up now); and give an unrecoverable item an escape hatch so it cannot wedge the queue — surfacing it as given up per honest-failure-surfacing, never retrying silently forever. A photo whose local file was gone once blocked an entire inspection's sync indefinitely.
What this skill does not do
It does not govern external send-then-record paths (outbound-side-effect-idempotency) or per-IP abuse caps on public endpoints (guard-the-spend-paths). It governs internal concurrency and fan-out.
Why
Concurrency bugs of this class bill you twice and rate-limit you once, and they are invisible in sequential testing — the duplicate cost only appears when two instances run at once. Evidence: ASH LESSONS_LEARNED 2026-06-04 (evening and later entries), 2026-05-27, and the CLAUDE.md Opus rate-limit lesson.
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.
- 12d ago First seen · 43 lines · 128 tokens per session scan A b87d99149606
lock-at-the-chokepoint is a skill published in the GitHub repository randommonicle/claude-skills (23 stars, last pushed 5d ago), licensed Apache-2.0. It adds 128 tokens to every session and 630 once invoked, about $0.0006 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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