# AGENTS.md

## Overview

`pick` is a tiny compiled Zig CLI for selecting TSV fields from stdin. It exists
as an agent-safe replacement for the safe subset of `awk '{print $N}'` and
`cut -f` when allowlist policy needs argv-obvious behavior.

## How to build

```sh
zig build
```

## How to test

```sh
zig build test
```

## Constraints

- One source file: `pick.zig`.
- No runtime dependencies, no shell execution, no filesystem reads/writes in the
  tool.
- stdout is TSV/plain records only; diagnostics go to stderr.
- No regex, expressions, arithmetic, sorting, paging, JSON, color, or hidden
  state.
- This is an inspection primitive. Do not add mutation or policy workflow.

## Requirement Governance

`REQUIREMENTS.md` is the requirement authority for this repository and is checked
with `redgate`. Before implementation work, read the applicable requirement row;
if none covers the durable behavior, update `REQUIREMENTS.md` first or stop and
ask for authority. When adding or changing rows, choose the ring by product
foundation, not implementation size: lower rings capture stable kernel
obligations and core contracts; higher rings compose on lower-ring obligations
and must not weaken, redefine, or bypass them. If one row mixes foundational and
optional behavior, split it before implementation.

If a change alters durable product obligations, acceptance behavior,
safety/recovery behavior, public interfaces, or verification duties, update
`REQUIREMENTS.md` in the same slice and run the relevant `redgate` checks. For
behavior intended to stick, write or update a failing BDD/TDD test, contract
test, or executable proof before implementation code; run it and record the RED
result. Implement only after the requirement row and RED proof exist. If RED
proof would be fake, unsafe, or disproportionate, state that exception before
implementation and use the strongest cheaper check.

Before final handoff, compare the user request and actual diff against
`REQUIREMENTS.md`. If there is no requirement impact, the handoff must include
exactly `REQUIREMENT IMPACT: none - <specific reason>`. If code, tests, or docs
changed but `REQUIREMENTS.md` did not, explicitly justify why no requirement row
changed.