# REQUIREMENTS

## pick
0	001	`pick` must be a compiled single-file Zig CLI with no runtime dependencies beyond the OS. [core]
0	002	`pick` must read TSV records from stdin and write selected TSV fields to stdout only. [stream]
0	003	`pick` must have no filesystem mutation, network access, shell execution, expression language, regex evaluation, hidden config, prompts, color, pager, JSON default, or daemon behavior. [agent-safe]
1	004	`pick FIELD...` must select 1-based numeric fields from headerless TSV input and preserve input record order.
1	005	`pick --header FIELD...` must resolve field names from the first TSV record, emit the selected header, and then emit selected fields from subsequent records.
1	006	Missing fields must emit empty TSV fields rather than failing a pipeline.
1	007	Usage errors must exit nonzero and write diagnostics to stderr, never stdout.
1	008	`zig build test` must prove numeric selection, header selection, missing fields, help/error stdout-stderr separation, CRLF input tolerance, invalid field rejection, and one forbidden near miss. [verification]
1	009	Project smoke tests must run under POSIX `sh` and exercise `pick` through pipe-oriented stdin/stdout/stderr behavior without leaving required generated artifacts. [posix]
1	010	`pick` must process stdin incrementally for pipeline-sized streams and must not print noisy diagnostics when downstream consumers close stdout early. [pipeline]