Rendered from docs/obligations/0148-the-help-assertion-never-asks-a-subcommand-and-no-rust-version-declares-the-floor-clap-now-sits-on.md in the Headwater corpus. Every document on this half of the site is typed by the taxonomy the descriptor names: corpus.json.

The help assertion never asks a subcommand, and no rust-version declares the floor clap now sits on

Context

Verification of PR #332 surfaced two gaps in the engine. PR #332 adopted clap for the command-line parser, and neither gap traces to that change or blocks it. The first sits in engine/crates/cli/tests/wiring.rs, in the case that asserts --help output. The second sits in engine/Cargo.toml, where no crate declares the Rust version the engine now needs.

Obligation

The case the_help_flag_answers_on_standard_output_outside_a_corpus loops over --help and -h against the bare binary alone. It asserts exit code, empty standard error, the --root <path> marker, and every verb name from headwater_verbs::VERBS. It never asks a subcommand. headwater check --help follows a different code path, introduced by the clap migration, and nothing in the suite pins it. Measured on the migration head, headwater --help prints 406 bytes and headwater check --help prints 537, both on standard output with exit 0. A regression that broke only the per-verb help path would leave the whole suite green.

The second gap is closed, and the margin this document called zero was already spent on the day it was written. ordered-float 5.5.0 entered engine/Cargo.lock transitively under saphyr on 2026-08-26. It declares a floor of 1.90. The two container commands in engine/README.md pinned an image at 1.85, so both exited 101 before they compiled a line. They stayed dead for 12 days and 111 commits. This repository went public on 2026-09-06 with both of them dead, and a change on that day edited both without running either.

[workspace.package] in engine/Cargo.toml now declares rust-version = "1.90", and each of the 23 crates under engine/crates/ declares rust-version.workspace = true. engine/clippy.toml states the same number as its msrv. tools/engine/engine-readme-fixtures.sh compares the highest rust-version across cargo metadata --locked against the image tag those two commands pin. CI runs that suite, and it needs no container and no build.

The last_verified field of this document was not evidence about the margin the paragraph above called zero. That field moves when the register is regenerated, not when a person or a check confirms the claim. It read 2026-08-26 on the day the margin was spent, which is the same date as the commit that spent it. So this entry looked freshly verified on the day it became wrong.

No check reads this document for the floor it states. tools/engine/engine-readme-fixtures.sh enumerates floor statements by four shapes. It reads an image tag, a sentence that names a Rust version, an msrv key, and a rust-version key. The prose here matches none of the four, so the entry that predicted this failure sits outside that population. Widening the shapes to reach it would catch every correct historical mention of a version. That is why the population stops where it does.

Discharge

Closing the first gap means deriving the help test's cases from headwater_verbs::VERBS, not writing them by hand. A hand-written list beside VERBS is the same defect issues #257 and #309 both named. The new case must ask every verb for --help and -h, not the bare binary alone. It must assert exit 0 and empty standard error for each verb. The case should be watched failing first, so a broken per-verb help path names the verb that broke it.

The second gap needs nothing further. cargo build and cargo test succeed on current stable and inside the pinned image, and cargo clippy --all-targets --locked -- -D warnings reports nothing at the raised msrv.

This document closes issue #334, recorded rather than planned. The first fix is not written, and this document stands as the debt until the corpus carries it.