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311 posts tagged with "ai-agents"

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The Agent Optimized Exactly What You Measured: Goodhart's Law in Agentic Loops

· 11 min read
Tian Pan
Software Engineer

Give an agent a measurable objective and the freedom to act on it, and it will pursue that objective with a literalness no human colleague would tolerate in themselves. It closes the support ticket without solving the customer's problem, because the metric was "ticket closed." It makes the failing test pass by deleting the assertion, because the metric was "test suite green." It raises the eval score by writing answers shaped to flatter the judge model, because the metric was "judge approves." Each of these is a win by the number you wrote down and a loss by the goal you actually had.

This is Goodhart's law, and it has a sharper edge in agentic systems than anywhere it has appeared before. The classic phrasing — "when a measure becomes a target, it ceases to be a good measure" — was an observation about institutions and incentives, things that drift over years. An agentic loop compresses that drift into a single run. The optimizer is tireless, fast, and creative in a way that human employees, bounded by effort and social norms, simply are not. It will find the gap between your proxy and your intent on the first afternoon, not after a quarter of slow erosion.

The Agent Trace That's Too Big to Debug: When You Logged Everything and Can Read None of It

· 11 min read
Tian Pan
Software Engineer

The standard advice for agent observability is three words long: log the full trace. Capture every tool call, every prompt, every model response, every memory read and write. Teams comply. Then the first real incident arrives, an engineer opens the trace, and discovers it is forty tool calls deep and two hundred thousand tokens wide. The trace is technically complete. It is also practically unreadable.

What follows is a familiar ritual. The engineer scrolls. They expand a span, see fifty thousand characters of JSON, collapse it, scroll again. Ten minutes in, they find the one model turn where the agent picked the wrong tool — buried between thirty-seven turns that did exactly what they were supposed to. The trace that was supposed to make the failure legible instead made it expensive to investigate.

The Approval Queue Nobody Drains

· 10 min read
Tian Pan
Software Engineer

You did the responsible thing. You looked at your agent, identified the actions that could cause real damage — issuing a refund, deleting a record, sending an external email, deploying a config change — and you routed them to a human for approval. Risk-tiered gating. Textbook. The review board signed off.

Then a customer escalation came in three weeks later: an agent task had been "in progress" since the previous Tuesday. Not failed. Not errored. Just sitting in a human approval queue that, it turned out, nobody was actually watching. The agent had done its job, parked the dangerous action behind a gate, and waited. The gate had no owner. The task aged silently in a place where no dashboard pointed and no alarm fired.

The Coding Interview That Agents Quietly Invalidated

· 10 min read
Tian Pan
Software Engineer

A two-hour take-home and a 45-minute algorithm round were never the point. They were proxies. The take-home stood in for "can this person ship a feature," and the whiteboard round stood in for "can this person decompose a problem under pressure." For two decades those proxies held up well enough that most teams stopped questioning them. They were cheap to administer, easy to grade, and roughly correlated with the thing you actually cared about.

Coding agents broke the correlation without breaking the format. The interview still runs. It still produces a score. The score still feels like signal. But the gap between what the interview measures and what the job requires has widened to the point where a green result certifies almost nothing — and most hiring pipelines have not noticed, because nothing visibly failed.

This is the quiet kind of invalidation. Not a process that collapsed, but a process that kept running after its assumptions stopped being true.

The Context Window Is a Commons, and Every Team Is Grazing It

· 10 min read
Tian Pan
Software Engineer

Open a production agent and count what is in the context window before the user has typed a single character. There is a system prompt the platform team owns. There are tool definitions — forty of them, maybe more — each carrying a name, a description, a JSON schema, field-level docs, and a handful of enums. There is a block of retrieved examples that the search team added because few-shot helped one eval. There are six lines of safety instructions from trust and safety, four lines of formatting rules from the design team, and a paragraph of domain glossary that someone added during an incident and nobody removed.

Add it up and the agent boots with 30,000 tokens of overhead. On a connected setup with three MCP servers, that number is routinely far worse — one widely cited measurement put three servers at 143,000 of a 200,000-token budget, 72% of the window consumed before the conversation starts. None of it is wrong. Every line was added by someone solving a real problem. And that is exactly why the context window is being destroyed.

The Demo That Set a Baseline You Cannot Afford to Run

· 9 min read
Tian Pan
Software Engineer

The demo went well. The agent answered the hard question, chained four tool calls without a stumble, and produced a paragraph that made the room go quiet for a second before someone said "ship it." Nobody asked what it cost. Nobody asked what model it ran on, how many inputs you tried before that one, or what happens when a thousand people hit it at once instead of you, alone, at your desk, on a Tuesday.

That demo just became a contract. Not a written one — worse. It became the unstated baseline that leadership, sales, and customers will hold the shipped product against. And the terms of that contract were set by a system you cannot afford to run.

The gap between demo economics and production economics is real, large, and almost never priced before the commitment is made. Gartner expects more than 40% of agentic AI projects to be canceled by 2027, largely on cost overruns. A March 2026 survey found 78% of enterprises had agent pilots running and only 14% had scaled one to organization-wide use. The pilots are not failing because the technology does not work. They are failing because the version that worked was never the version anyone could deploy.

The Demo-to-Production Cliff: Why a 90%-Accurate Agent Ships at 0%

· 9 min read
Tian Pan
Software Engineer

There is a specific kind of meeting that happens about six weeks after an impressive agent demo. The prototype booked the trip, refactored the module, reconciled the invoices — live, on the first try, in front of stakeholders. Everyone agreed it was ready. Then someone pulled the production numbers, and the agent that "worked" was generating a support ticket every forty completed tasks, a refund every few hundred, and a quiet trail of half-finished states nobody could explain. The project did not get killed. It got stuck. It is still stuck.

This is the demo-to-production cliff, and it is the single most reliable way for an agent project to fail. The cliff is not caused by a bad model or a sloppy team. It is caused by a measurement mistake: treating a 90% success rate as 90% of the way to shipping. It is not. A 90%-accurate agent is a triumphant demo and, for most real workflows, an unshippable product. The MIT NANDA report that made headlines in 2025 — 95% of enterprise GenAI pilots delivering no measurable P&L impact — is this cliff, counted at scale.

The Happy Path Is the Only Path Your Agent Eval Ever Tested

· 10 min read
Tian Pan
Software Engineer

Look at where most agent eval sets come from. Someone builds the agent, demos it to the team, the demo works, and the demo script becomes the eval suite. The cases that pass review are the cases someone already watched pass. The eval set is, almost by construction, a recording of the happy path — the one tool sequence that worked the day the screenshot was taken.

So when the dashboard says the agent scores 94%, what it actually says is: it passes the cases we imagined. It says nothing about the case where the search API returns a 429 in the middle of a multi-step plan, where the user contradicts a constraint they stated two turns ago, or where retrieval comes back empty and the agent has to decide between guessing and admitting it doesn't know. Those cases aren't failing your eval. They were never in it.

This is golden-path bias, and it is the default shape of an agent eval suite unless you fight it deliberately. The fix is not more cases. It is different cases — chosen by failure mode, harvested from production, and stress-tested with deliberate faults.

The Idempotency Key Your Agent Never Sent

· 11 min read
Tian Pan
Software Engineer

A customer once got refunded three times for a single return. Not because the model hallucinated a policy, not because a human fat-fingered a form — because the refund tool timed out twice, the agent retried both times, and every retry carried a fresh request with no way for the payment processor to know it had seen this work before. Three clean HTTP 200s. Three real movements of money. The agent did exactly what it was told: when a call fails, try again.

The bug was not in the model. The bug was in a header that was never sent.

Retrying is the single most natural thing an agent does. A tool call returns an error, or worse, returns nothing at all, and the loop's instinct — encoded in the framework, the prompt, or the model's own training — is to try the action again. That instinct is correct for reads and catastrophic for writes. The difference between a resilient agent and one that double-charges customers is not intelligence. It is whether every state-changing tool call carries an idempotency key, and whether the system on the other end actually honors it.

The Incident Ticket With No Repro Steps: Reproducibility as Something You Engineer

· 10 min read
Tian Pan
Software Engineer

The incident ticket is specific in the way only real incidents are. At 02:14 the support agent closed a customer account that should have been put on a 30-day grace period. The customer noticed. The ticket lands on your desk with a single line under "Steps to reproduce": unknown.

You open the trace. You can see the agent called close_account instead of set_grace_period. You can see the tool succeeded. What you cannot see is why the model chose that branch — and when you replay the same customer message through the same agent, it does the right thing. Twice. The postmortem now has a paragraph-shaped hole where the root cause should be, and the only honest thing you can write is "could not reproduce."

Your Internal API Became a Public API the Day an Agent Called It

· 10 min read
Tian Pan
Software Engineer

Internal APIs survive on a quiet arrangement: nobody writes the contract down because everybody already knows it. The fields that happen to be there, the error you throw that a caller secretly parses, the endpoint that returns 200 with an empty list instead of 404 — these are load-bearing behaviors held together by the fact that you can name every caller and Slack them before you change anything. That arrangement works right up until it doesn't.

It stops working the day you wire an agent to that API. Not because the agent is malicious or careless, but because the agent is a caller you cannot reach. It has no Slack handle. It did not read your migration note. It depends on response shapes it absorbed from an example payload or a schema snapshot, and it will keep depending on them long after you've moved on.

The uncomfortable truth is that "internal" was never a property of the API. It was a property of the caller list. Shorten that list to people you know and the API is internal; add one participant you can't coordinate with and the API is public — with all the discipline that word implies, and none of the infrastructure you'd have built if you'd known.

When LLMs Review LLMs, Errors Get Laundered Not Caught

· 10 min read
Tian Pan
Software Engineer

Trace the path of a single quality signal through a modern AI pipeline. An agent drafts a response. A second model reviews it and scores it 9 out of 10. That score gets logged. At the end of the quarter, the logged scores become the new eval set, and the next model is tuned to do well against it. Now ask the obvious question: where in that loop did a human ever look at the actual output?

In a lot of pipelines, the honest answer is nowhere. The agent that does the work is reviewed by another agent, and that reviewer's verdict feeds the next round of evaluation. The loop is closed. It runs continuously, it produces a dashboard, and the dashboard is green. What it does not contain, at any point, is a measurement against reality.