gate-check

# Find the gates Theory: [Cheap decisions](https://undefined-ui.github.io/second-brain-os/#course-3-gate/cheap-decisions) and [Gate practice](https://undefined-ui.github.io/second-brain-os/#course-3-gate/gate-practice). An agent does two kinds of work: it writes, which needs a big model, and it decides — is this spam, which queue, does this need a person — which is a bounded question the answer to which comes from a set you already know. A gate is a cheap decision layer that sorts the stream so the expensive model only sees the items that actually need judgement. ## Workflow 1. **Map the decisions.** Read the pipeline's entry points and prompts and list every decision made before or during a model call: classification, routing, filtering, yes/no triage, priority, language, "is this even for us". Ignore the writing — only bounded decisions with a known label set. 2. **Count what each costs today.** For each decision currently made by the big model: calls per day if known, tokens per call, and what a wrong answer costs. A decision worth one bit that burns a frontier call is the headline finding. 3. **Propose the cheapest gate that can hold it**, in rising order of cost: - a **rule** — regex, allowlist, header check: free, instant, blind to anything unanticipated; always the first layer, never the last - a **classic classifier** — logistic regression or similar over simple features, trained on a few hundred labelled examples: milliseconds, fractions of a cent, and the baseline every fancier option must beat - a **small / System One model** — when the input is too varied for features but the output is still a label with a confidence score 4. **Route fail-closed.** Every gate needs a confidence threshold, and doubt goes down the safe path: unsure means escalate to the big model (or a person), never means guess. Say explicitly what each gate's unsure route is. 5. **Offer the baseline scaffold.** If the user wants to proceed, generate the module's thirty-minute exercise for their data: a `label.py` that samples ~200 real examples for hand-labelling, and a `baseline.py` that trains the classic classifier and prints accuracy against a held-out split. Every vendor claim and small-model option must beat this number on their data before it earns a place in the pipeline. ## Output format ``` Gate check — <pipeline> decisions found: <n>, currently on the big model: <n> 1. <decision> — <where in the code> today: <who decides, est. cost> label set: <the labels> gate: <rule | classifier | small model> — <why this tier> unsure -> <escalation path> saves: <est. calls/tokens diverted> ... ``` Rank by savings. If a decision genuinely needs the big model — open-ended, no stable label set, wrong answers are cheap to fix — say so and leave it alone; a gate that guesses is worse than no gate.