What causes "usage: latest [--json] " in pbakaus/impeccable?

Pass exactly one argument: the slug or a resolvable target path (use an explicit `./path` for local targets).

usage: latest <slug-or-target> [--json]

Error message

usage: latest <slug-or-target> [--json]

What it means

The `latest` subcommand validates its arguments before doing work: it requires a resolvable slug-or-target and, if a second argument is given, it must be exactly `--json`. Anything else prints this usage line to stderr and exits 1.

Source

Thrown at crates/context/src/critique_storage.rs:545

            match written {
                Some(fp) => {
                    io.out(&format!("{}\n", fp));
                    0
                }
                None => {
                    io.err(&format!("{}\n", uncaught(&format!("Too many critique snapshots for {} at {}", slug, timestamp))));
                    1
                }
            }
        }
        "latest" => {
            let target = rest.first().map(String::as_str).unwrap_or("");
            let format = rest.get(1).map(String::as_str);
            let slugs = slug_candidates(rest.first().map(String::as_str), &cwd);
            // JS: format && format !== '--json'  (format truthy = non-empty)
            let bad_format = format.map(|f| !f.is_empty() && f != "--json").unwrap_or(false);
            if slugs.is_empty() || bad_format {
                io.err("usage: latest <slug-or-target> [--json]\n");
                return 1;
            }
            let format_is_json = format == Some("--json");
            let target_fingerprint = fingerprint_target(target, &cwd);
            let target_path = resolve_local_target_path(target, &cwd);
            let target_identity = resolve_target_identity(target, &cwd);
            let ready_slug = is_ready_slug(target);
            let Some(newest_for_slug) =
                read_newest_safe_snapshot_for_slugs(&slugs, target_identity.as_deref(), &cwd, &env)
            else {
                return 2;
            };
            let mut latest =
                read_newest_snapshot_for_identity_slugs(&slugs, target_identity.as_deref(), &cwd, &env);
            if latest.is_none() && !ready_slug {
                // Identity-less snapshots are safe only under the new/current
                // collision-resistant slug. A pre-hash slug suffix alone cannot
                // prove which long target owned the historical snapshot.

View on GitHub (pinned to 2bc2879276)

Solutions

Pass exactly one argument: the slug or a resolvable target path (use an explicit `./path` for local targets).
If you want JSON, pass the literal flag `--json` as the second argument with nothing after it.
Verify the slug resolves: `impeccable critique-storage slug <target>` should print a non-empty slug.
Quote shell variables so an empty arg is not silently dropped or split.

Example fix

// before
latest mytarget --JSON
// after
latest mytarget --json

Defensive patterns

Strategy: validation

Validate before calling

const args = ['latest', target];
if (wantJson) args.push('--json');
const slug = runCapture('impeccable', ['critique-storage', 'slug', target]).stdout.trim();
if (!slug) throw new Error('target does not resolve to a slug');

Prevention

Always pass the slug/target as the first and only positional argument.
Use the exact literal `--json` flag when JSON output is needed.
Resolve the target with the `slug` subcommand before calling latest.
Quote shell variables to avoid empty or split arguments.

When it happens

Trigger: Running `critique-storage latest` with no argument; with a first argument that yields no slug candidates (empty or unresolvable target); or with a second argument that is not `--json` (e.g. `--JSON`, `-json`, `json`, or an extra stray flag).

Common situations: Typos like `--json=v1` or `latest mytarget --json extra`; running from a directory where the target slug cannot be resolved; scripting the command with a variable that expands to an empty string.

Understand the failure class

Background: "Unknown argument", "Invalid value", and "must be one of": invalid CLI argument errors explained — this error's family across 35 libraries.

Related errors

AI-assisted analysis of pbakaus/impeccable@2bc2879276 (2026-09-08). Data as JSON: /api/errors/75f2d376d5a24933. Report an issue: GitHub.