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.
git clone --depth 1 https://github.com/GoranErhartic/cursor-development-rulesWrote 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/rules/goranerhartic/cursor-development-rules/idempotency)<a href="https://agentmods.dev/rules/goranerhartic/cursor-development-rules/idempotency"><img src="https://agentmods.dev/badge/rules/goranerhartic/cursor-development-rules/idempotency/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/rules/goranerhartic/cursor-development-rules/idempotency"><img src="https://agentmods.dev/badge/rules/goranerhartic/cursor-development-rules/idempotency.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 | $0.00035 | $0.00427 |
| Opus 5.5 | $0.00014 | $0.00171 |
| Sonnet 5.5 | $0.00007 | $0.00085 |
| Haiku 4.5 | $0.00003 | $0.00043 |
Grade A, and why
idempotency 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 1mo 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.
What it actually says
Idempotency Patterns
Why
SQS/SNS and Lambda retries deliver at least once. Idempotency ensures processing the same message/request multiple times has the same effect as once (e.g. no duplicate payments, emails, or records).
Powertools Idempotency
- Persistence: DynamoDB table with
id,expiration,status,data(or equivalent); TTL on expiration - Config:
eventKeyJmesPathto extract key from event (e.g.body.idempotencyKey, or for SQSRecords[0].bodythen parse and use eventId/aggregateId);expiresAfterSeconds;throwOnNoIdempotencyKeyas needed - Wrapper:
makeIdempotent(handler, { persistenceStore, config })around handler; handler receives same event; first call runs and stores result; duplicate key returns stored result - Method-level:
idempotent({ persistenceStore, config })decorator on async method; key from first argument (e.g. payload.idempotencyKey)
Key Choice
- API: Client sends
Idempotency-Keyheader or body field; use for POST/PUT - SQS: Use
eventIdfrom envelope, ormessageId+ aggregateId; ensure key is stable per logical request - SNS: Use
eventIdor (aggregateId + eventType)
Conventions
- Required for all state-changing SQS consumers and mutation APIs; store in DynamoDB with TTL; use stable, unique key per logical operation
Anti-Patterns
- No idempotency for SQS consumers that write; key derived from unstable data; TTL too long (resource exhaustion)
See also: sqs-processing.mdc, dynamodb.mdc, error-handling.mdc
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.
- 1mo ago First seen · 33 lines · 35 tokens per session scan A 552aca1fc693
idempotency is a cursor rule published in the GitHub repository GoranErhartic/cursor-development-rules (19 stars, last pushed 7mo ago), licensed MIT. It adds 35 tokens to every session and 427 once invoked, about $0.0001 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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