fix(flights): describe --stops as the set it is, and teach the at-most form

[sunny-wego]

Closes wego/foundations#105 (filed against wego 0.9.0; reproduced unchanged on 1.3.1 and on main).

Reproduced

One search, DXB→CAI 2026-10-15/22, 1 adult, site AE, currency AED, read after --wait settled it at converged (5374 candidates):

flag	totalCandidates	stop counts on the page
--stops 0	81	[0]
--stops 1	5121	[1]
--stops 2	172	[2]
--stops 0,1	5202	[0,1]
--stops 3	0	[]

81 + 5121 = 5202, so 0,1 is the union of the two sets and --stops 1 excludes nonstops rather than bounding them. Exactly the reporter's numbers on a fresh snapshot.

Root cause

Set semantics are correct and intended. src/api.ts CSVs --stops straight onto ?stops=, and the generated contract in src/api-types.d.ts states it plainly: "Stop counts… OR'd together; matched against the trip-level stop count." There is no maximum form of the param and the CLI performs no transformation.

The defect is entirely in the two surfaces that describe it, and it took both of them to land the caller in the wrong place:

1. src/commands.ts described the flag as "Max stops on the trip. Comma-list." — a bound, which is the opposite of what it does and which nothing in the codebase implements. As the issue notes, the two halves of that string contradict each other: if it were a maximum, a comma-list would be meaningless.
2. skills/wego/SKILL.md showed only --stops 0 and said "Use --stops 0 for nonstop". That is the single value where "exact set" and "maximum" coincide, so the skill was correct-but-silent and never contradicted the help text. Every other non-obvious filter in that list — --alliances, --aircraft, --airlines-match, --same-airline, --booking-sites, the stopover-duration pair — has a bullet spelling out its exact matching semantics. --stops had none.

Why it stays silent. The response is a valid page, totalCandidates is large, and no counter or stderr line reports that a category was removed. And unlike --alliances and --aircraft, whose docs tell an agent to recover by reading metadata.filterOptions, there is no filterOptions.stops vocabulary in the envelope. So these two strings are the only sources of truth for this flag — which is what turns a wording slip into a durable correctness defect.

The fix

Set semantics are unchanged; no behaviour moves.

• Help text → "Exact stop counts. At most 1 is 0,1." Kills the bound word and carries the recipe, in one line.
• Skill → a --stops bullet at the depth of its neighbours: the values are OR'd; --stops 1 silently drops every nonstop; "at most N" is enumerated from 0; the count is trip-level (max across legs), so a nonstop-out / one-stop-back round trip is kept by --stops 1; there is no filterOptions.stops to discover, so enumerate; and a count no trip has returns totalCandidates: 0, which means inapplicable, not "no flights". The lead paragraph now names --stops 0,1 alongside --stops 0.
• Two guards so neither half drifts back. help-shape.test.ts asserts the --stops row carries no bound word and still contains the 0,1 recipe; skill-embed.test.ts asserts the embedded skill teaches the enumerated form. Verified failing against the old string before landing — a description that merely stopped lying would leave the flag correct and still unusable for the constraint callers actually state, which is why both halves are pinned.

Note for reviewers

RESULTS_USAGE was 2489 bytes against the 2500-byte leaf cap in help-shape.test.ts — 11 bytes of headroom. The new wording fits (2491), but the page is at its ceiling, so the next correctness fix to this help text has to trade prose against prose. Worth raising the cap deliberately rather than discovering it under pressure; left alone here to keep this change to the defect.

Verification

bun test 1563 pass / 0 fail · typecheck clean · biome check clean on all four changed files (the 7 repo-wide warnings are pre-existing, in hotels.test.ts).

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https://claude.ai/code/session_0167qmEbF8xVHvvTizperFq7

Summary by CodeRabbit

• Documentation

  • Clarified that flight stop filters select an exact, OR’d set of trip-level stop counts.
  • Added guidance to use --stops 0,1 when allowing nonstop or one-stop flights.
  • Clarified that --stops 1 excludes nonstop flights and is not a maximum.
  • Explained that zero matches mean no trip matched the requested counts.

• Tests

  • Added coverage ensuring command help and embedded documentation accurately describe stop filtering.

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📝 Walkthrough

Walkthrough

The --stops documentation now defines exact stop-count filtering. It uses --stops 0,1 for trips with at most one stop. Regression tests verify the CLI help and embedded skill text.

Changes

Stop filter guidance

Layer / File(s)	Summary
Stop-count contract skills/wego/SKILL.md, src/commands.ts	The documentation and CLI help describe exact stop counts, OR semantics, and 0,1 enumeration for at most one stop.
Stop-count regression coverage src/help-shape.test.ts, src/skill-embed.test.ts	Tests verify the exact-count wording, the 0,1 example, and the absence of maximum-bound wording.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 2e6d1

The change documents exact stop-count behavior and adds regression coverage without establishing a new implementation risk.

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✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: it updates --stops documentation and explains the enumerated form for “at most” filtering.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 3…
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Actionable comments posted: 1

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Inline comments:
In `@skills/wego/SKILL.md`:
- Line 241: The --stops documentation incorrectly describes zero matches as an
inapplicable filter. Update the guidance around --stops and totalCandidates to
state that zero means no trip matched the requested valid trip-level stop count,
while reserving “inapplicable” for structural cases such as return filters on
one-way searches.

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