--- title: "Practitioner's Corner" canonical: "https://current.tinyfish.ai/issue/36/practitioners-corner" publication: "TinyFish" publisher: "TinyFish" language: "en-US" guide: "https://current.tinyfish.ai/llms.txt" permalink: "https://current.tinyfish.ai/issue/36/practitioners-corner" issue: 36 section: "practitioners-corner" description: "Lessons from the field—what we see building at scale" authors: ["Rina Takahashi","Nora Kaplan"] published: 2026-07-06 updated: 2026-07-02 articles: 14 --- # TinyFish > CURRENT is a journal about AI agents in production, for the engineering and product leaders who have to make them work. Drawing on experience building enterprise web agents, it explains why the demo succeeded and the deployment didn't, and what that means for choosing vendors, briefing the board, and avoiding mistakes others have already made. [Read on the website]() ## Issue 36 — Practitioner's Corner Lessons from the field—what we see building at scale ### Builder Profile - [Shunyu Yao Taught Agents to Reason, Then Learned to Stop Trusting the Transcript]() — By [Rina Takahashi]() · Published 2026-07-02 · Format: Builder Profile In 2022, Shunyu Yao gave agents a grammar for reasoning. ReAct became the template: think, act, observe, repeat. The reasoning trace was the proof. Three years later, Yao built tau-bench, which ignores the trace entirely and checks the database. GPT-4o completes retail tasks about 61% of the time on a single attempt. Require it to succeed consistently across eight runs, and the number drops below 25%. The person who taught agents to show their work now measures how much distance sits between a convincing transcript and a correct outcome. ### Core Idea Piece - [The Dispute File Is the Spec]() — By [Rina Takahashi]() · Published 2026-07-02 · Format: Core Idea Piece When a cardholder calls their bank, it doesn't matter that the agent completed the purchase correctly. The file decides everything: the evidence a merchant must produce to defend the transaction. Visa and Mastercard have spent decades codifying what a defensible action looks like. Now that machinery applies to agent-mediated payments. And the questions it asks about authorization, scope, and remedy are indifferent to reasoning quality or benchmark scores. They ask whether what happened can survive challenge. Most agent systems aren't producing the artifacts that would let them answer. ### Dispute Analyst - [Filing a Plumbing Complaint Under "Electrical"]() — Published 2026-07-02 *Payment networks have spent decades refining the taxonomy of things that go wrong between a consumer and a merchant. Eight reason code categories. Hundreds of sub-codes. Evidence requirements calibrated to specific failure modes: fraud, duplicate charges, products never received. The system assumes two parties and a human decision.* ### Recognition Problem - [The Fingerprint Knows You're an Agent. Now What?]() — By [Rina Takahashi]() · Published 2026-07-02 Researchers can now [identify web agents](https://arxiv.org/abs/2605.01247) by how they type, scroll, and move a cursor. Paste-based form fills, direct jumps to click targets, repeated delete-and-retype loops. One study detected all seven agents tested; Cloudflare caught one. A [June preprint](https://arxiv.org/abs/2606.20910) went further, fingerprinting agents at the network layer too. Within weeks, developers were publishing techniques to mimic human mouse trajectories. ### Further Reading - **Visa Embeds Payments Inside ChatGPT** — [Source]() — Published 2026-07-02 When consumer intent and merchant processing both check out but the agent layer got it wrong, whose dispute is it? - **Mastercard Unveils Agent Pay** — [Source]() — Published 2026-07-02 The full delegation stack on paper: register, tokenize, verify, control. Production evidence still forthcoming. - **OWASP Top 10 for Agentic Applications (2026)** — [Source]() — Published 2026-07-02 Goal hijacking, tool misuse, identity abuse. Authorization alone never constituted accountability, and agents prove it. - **τ-bench: A Benchmark for Tool-Agent-User Interaction** — [Source]() — Published 2026-07-02 Evaluates database state, not conversational polish. The pass^k metric quantifies exactly the repeatability that accountability demands. - **The State of AI in 2025 (McKinsey)** — [Source]() — Published 2026-07-02 Broad adoption, rare scaling. Under 10% deploy agents in any single function. Workflow redesign correlates with actual results. - **FP-Agent: Fingerprinting AI Browsing Agents** — [Source]() — Published 2026-07-02 Research classifiers caught all seven agents tested. Commercial bot defenses caught one. The recognition gap is wide open. ### Past Articles - [What WorkArena's Task Design Makes Visible]() — By [Nora Kaplan]() · Published 2026-06-24 · Format: Builder Profile One benchmark task asks an agent to create a hardware asset in ServiceNow. The agent fills in fields, clicks submit, reaches a confirmation screen. WorkArena ignores the confirmation screen entirely. Its validator queries the database directly, checking whether saved values match the spec. An agent that navigated perfectly but corrupted data underneath would look like a success to anyone watching. That design choice, buried in validation code, surfaces a problem anyone deploying agents inside enterprise systems will eventually have to solve. - [What a Click Carries]() — By [Rina Takahashi]() · Published 2026-06-24 · Format: Central Idea Piece When a person clicks a button on a webpage, the infrastructure only sees the click. It never sees the reading, the context, the judgment, the acceptance of responsibility that preceded it. It never had to. The entire web assumed a human was present, so thoroughly that nobody wrote it down. Now agents produce identical HTTP requests without any of that invisible context. The sessions still fire. But the click has stopped carrying what every downstream system quietly depended on it to carry. - [Retry Logic Assumes a Contract That LLM Agents Can't Keep]() — By [Rina Takahashi]() · Published 2026-06-19 · Format: Retry Collision Retry logic in distributed systems works because of a quiet contract: same input, same execution path. An idempotency key ties attempts together, and the server returns a cached result instead of executing again. Agent systems inherit this discipline. But when an LLM decides which tools to call, token sampling variance means the same prompt can produce different tool selections, different parameters, different ordering on retry. Each individual tool call can be perfectly idempotent, and the composed sequence still produces different side effects on each attempt. One developer documented an agent double-charging a customer $847 when a timed-out payment triggered a retry that took a different path through the same workflow. - [The Web Wasn't Built for This]() — By [Nora Kaplan]() · Published 2026-06-19 · Format: Builder Profile To a person with a browser, a form field is a text box. To a machine trying to operate that same page, it's a hundred lines of nested HTML with the semantically important element buried under presentational scaffolding a visual cortex would simply ignore. Magnus Müller's Browser Use project started from a hobbyist's question about connecting LLMs to the web. His design choices since — rejecting vision-based navigation, treating site instability as a condition to absorb — trace the real complexity: the web was built for human interpreters, and operating it as a machine surfaces a mismatch that no selector strategy can bridge. ## Other sections in Issue 36 - [Daily Brief]() - [Market Pulse]() - [Foundations]() - [Echoes]() - [Vision]() ## More - [Publication guide]() - [Issue archive]()