Driftless field notes

Practical guides for LLM workflows that move.

Model deprecations, changing labels, cheaper inference, RAG, and agents. Each guide shows how to keep the model, prompt, and eval data in sync with a reproducible example.

Guide 017 min read
Your ticket classifier’s model got deprecated

You run a support product that routes every inbound ticket through an LLM classifier before a human ever sees it. The model returns a small JSON object like {"category": "billing"}. Downstream code parses that JSON…

Read guide →
Guide 026 min read
Support changed the labeling policy

Same support classifier as post 1: every ticket gets a gold category so you can measure quality offline. For a long time, tickets like "Please reverse the payment on my latest invoice" are labeled billing — the team…

Read guide →
Guide 035 min read
Prompt repair that doesn’t wait on memory

Your LLM app already looks "done" from a git perspective: prompts live in the repo, gold labels live in JSONL, and a harness command can score quality offline. You can migrate a model or refine after a label change…

Read guide →
Guide 044 min read
Finance wants cheaper inference, same bar

Your classifier (or similar LLM workflow) runs on a frontier model — say gpt-4o — because that is what cleared quality when you launched. Volume grew. Finance now wants 20%+ inference savings. A cheaper model like…

Read guide →
Guide 054 min read
Offline F1 is lying — labels conflict

You trust your offline eval. Macro-F1 on a few hundred labeled tickets is how you decide whether a model migration or prompt refine is safe. After a labeling policy change (or a messy annotation pass), you run…

Read guide →
Guide 065 min read
Free-form answers graded by an LLM judge

Not every LLM workflow is a classifier with gold categories. You might summarize support tickets, rewrite answers for tone, or grade free-form responses for faithfulness. There is no single label_field to compute…

Read guide →
Guide 074 min read
RAG QA: new answer model, same knowledge base

You ship a retrieval-augmented QA feature: user asks a question, the app retrieves chunks from a knowledge base, and an LLM writes an answer that should stay grounded in those chunks and cite them. Quality is…

Read guide →
Guide 084 min read
Tool-calling agent: new planner, same tools

You run a support-style agent that must use tools — look up an order, check a policy, create a ticket — before it answers the user. Success is not only a polite final message. The agent must call the right tools in a…

Read guide →