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abstract indexed · arXiv 2609.29095 · updated 2026-10-18

Where Does Exactly-Once Live? Model, Harness, and Tool-Contract Effects on Duplicate Side Effects in LLM Agents

First page of Where Does Exactly-Once Live? Model, Harness, and Tool-Contract Effects on Duplicate Side Effects in LLM Agents
From the original paper · arXiv 2609.29095Page 1. Select the image to read the PDF.

The technique replaces blind retry or model-level caution when a tool write times out or errors: a small harness guard that attaches an idempotency key to every write, letting the service deduplicate redeliveries. Cost is modest engineering (a key-generation and propagation guard, plus tool contracts that accept keys) with no model, GPU, or serving overhead; where contracts cannot accept keys, only waiting with a known in-flight bound partially substitutes. It fails when tool APIs do not support idempotency keys, when faults occur outside the service boundary the guard covers, and agents still misreport success (90% of duplicated episodes were reported as successful), so ledger-level auditing remains necessary.

For solo builders

A possible application for this research area. Paper-specific feasibility still needs a full-paper review.

Tool errors or unavailable services cause your agent to abandon recoverable tasks.

What you would change

Inject repeatable tool failures and change only the recovery policy.

Try the idea on your product

A proposed first test. Set your budget and success criteria before running it.

Inject repeatable tool failures and change only the recovery policy.

Compare against

Your current retry and fallback behavior under the same injected failures.

  1. Locate the paper's implementation and check its license, model support, data needs, and hardware requirements. Stop here if you cannot obtain the required artifacts.
  2. Save a small set of representative product tasks and expected outcomes. Keep evaluation tasks out of any training or tuning, and choose quality and cost limits before running.
  3. Run the baseline and the proposed change on identical inputs. Keep other settings fixed and repeat paired runs to expose variation.
  4. Save per-task outputs, failures, timings, and all usage costs. Review regressions before expanding the test.

What to measure

Recovered tasks, duplicate side effects, retries, time to recovery, and total cost.

When to keep it

Keep the change only if it meets your preselected quality and latency limits and improves the metric you care about after setup and operating costs. Otherwise retain the baseline. This is an exploration plan, not a validated recommendation.

Download test plan ↓

abstract indexedPaperraft next step

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This page uses the abstract and public adoption signal only. Request the deep report before relying on its recommendation.

Abstract-level screening only. Risks and infrastructure may not have been evaluated. This recommendation is not a reproduced result.
minimum test setup
not reported
published evidence setup
not reported
source-linked claims
0 of 2
exposure checks
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Why it was shortlisted

The technical change, research area, and reason it entered the archive.

recommendation
adopt
research area
failure recovery
technical change
Idempotency-key guard on agent tool writes
published
2026-09-24

It is a cheap harness-level guard requiring no scale or training that the paper shows cuts duplicate side effects roughly sevenfold and transfers unchanged across production harnesses, making it immediately adoptable on constrained infrastructure.

About the technical core

Equations have not been fetched yet.

When reading the methods, identify the rule, algorithm, or evaluation protocol that produces the claimed change. An equation is useful here only if it explains that mechanism.

Inspect the original paper

Claims and evidence

A claim is source-linked only when the PDF page and matching excerpt are available.

  1. claim 01Paperraft inference
    Read the brief interpretation

    The technique replaces blind retry or model-level caution when a tool write times out or errors: a small harness guard that attaches an idempotency key to every write, letting the service deduplicate redeliveries. Cost is modest engineering (a key-generation and propagation guard, plus tool contracts that accept keys) with no model, GPU, or serving overhead; where contracts cannot accept keys, only waiting with a known in-flight bound partially substitutes. It fails when tool APIs do not support idempotency keys, when faults occur outside the service boundary the guard covers, and agents still misreport success (90% of duplicated episodes were reported as successful), so ledger-level auditing remains necessary.

    This is a Paperraft inference. It is not pinned to a verified PDF passage.

    Inspect the source
  2. claim 02Paperraft inference

    Offering an idempotency key on every write lowers the duplicate-effect rate from 28% to 4%; it transfers across harnesses unchanged, while waiting up to an hour per episode under heavy-tailed in-flight delays falls short of it.

    This is a Paperraft inference. It is not pinned to a verified PDF passage.

    Inspect the source

Exposure map

Author findings, Paperraft interpretations, and the next check. Missing analysis never counts as evidence of safety.

quality

Still unknown

Which tasks improve, and which regress against the baseline?

compute and memory

Still unknown

What memory, hardware, and total compute does the complete method require?

latency

Still unknown

Are startup time, typical response time, and slow requests measured separately?

operations

Still unknown

What must be monitored, maintained, and rolled back?

software compatibility

Still unknown

Does the implementation support your model, runtime, and hardware?

security

Still unknown

What new data access, permissions, or trust boundaries does it introduce?

data and training

Still unknown

What data preparation or training is required, and is it included in the cost?

reproducibility

Still unknown

Are code, versions, inputs, and evaluation scripts available?

Continue the investigation

A reading guide for failure recovery.

Editorial prompts, not findings from this paper or a validated test plan. Detailed analysis is still pending for the topics below.

What to inspect

Which assumptions does the proposed method need, and where might your workload violate them?

Plan a fair comparison

Identify the baseline, metric, dataset, and experimental settings in the paper. Which can you match?

Questions for adoption

What implementation and evaluation artifacts are available, and what would you need to supply?

Read the paper with these questions

Inside the paper

Preview the first 3 pages of the original PDF. Click the stack to turn the page.

The downloadable skill includes SKILL.md and evidence.json, with recorded findings and unanswered checks. TRY-IT.md adds a product test plan and a blank results sheet.

A reading aid for your agent. Findings still need validation.

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Provisional research brief updated 2026-10-18. Paperraft has not reproduced this experiment.

Discuss this paper

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arXiv 2609.29095

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