Scope: "Bicycle Accessories" (supplies > active > bicycle_accessories), sibling to "Bicycles & Parts" (frames/drivetrain, published) — excludes the bike itself and its mechanical parts. Covers 8 bundled product types experts judge independently: helmet, lock, light, pump/repair kit, rack/pannier, bike computer/GPS, bottle cage, child seat. Car-mounted bike-transport racks are out of scope (different buyer, different category).

Seed:
1. Equivalent of the weave-vs-thread-count example: for locks it's Sold Secure tier (Diamond/Gold/Silver/Bronze), not price or weight; for helmets it's certification + MIPS, not styling.
2. A security consultant/mechanic persona would notice first that "rated" and "certified" mean nothing without naming which standard (Sold Secure vs ART; CPSC vs EN 1078) — generic "security rated" or "safety certified" copy on a listing is close to meaningless without the body's name.

Sources:
[wiki_helmet] https://en.wikipedia.org/wiki/Bicycle_helmet — CPSC (1999, US mandatory), EN 1078 (EU), AS/NZS 2063, MIPS reduces rotational force, CPSC/EN1078 test only linear accel, 96% of child helmets misfitted — fetched excerpt, read directly
[wiki_lock] https://en.wikipedia.org/wiki/Bicycle_lock — lock forms (U/folding/chain/cable/frame/disc), case-hardened steel vs hardware chain, Cycle mag breached Gold locks <42s — fetched excerpt
[soldsecure_ratings] https://soldsecure.com/ratings/pedal-cycle — Diamond/Gold/Silver/Bronze tiers, matched to bike value + area risk — fetched excerpt (found real URL via nav links on soldsecure.com homepage, which 404'd at the guessed slug)
[wiki_light] https://en.wikipedia.org/wiki/Bicycle_lighting — lumens range "a few" to automotive-headlamp-equivalent, front white/rear red convention — fetched excerpt
[niterider] https://www.niterider.com/products/lumina-1200-boost — 1200 lm max, runtime 0:55h@1200lm to 18:00h@75lm — fetched excerpt (meta description + body text)
[wiki_presta] https://en.wikipedia.org/wiki/Presta_valve — Presta 6mm vs Schrader/Dunlop 8mm, used for high-pressure tubes/tubeless — fetched excerpt
[wiki_schrader] https://en.wikipedia.org/wiki/Schrader_valve — wider automotive-style valve also used on bicycles — fetched excerpt
[wiki_computer] https://en.wikipedia.org/wiki/Bicycle_computer — wired vs wireless sensors, ANT+ reliability vs phone Bluetooth, cadence sensor — fetched excerpt
[wiki_pannier] https://en.wikipedia.org/wiki/Pannier — hook/latch/elastic rack attachment, front low-rider pair smaller than rear touring pair — fetched excerpt
[wiki_childseat] https://en.wikipedia.org/wiki/Bicycle_seat — front-mounted (youngest/lightest) vs rear-mounted (older child) seats are distinct lines — fetched excerpt
[thule_childseat] https://www.thule.com/en-us/us/learn/child-bike-seats — front and rear child seats listed as separate category lines — fetched (nav/category JSON only, page body was JS-rendered)

Branches:
- accessory_type -> helmet/lock/light/pump_or_repair_kit/rack_or_pannier/bike_computer_or_gps/bottle_cage/child_seat: each leg supported by its own group's sources above; each makes the other 7 groups' facets irrelevant since none of their specs transfer (e.g. a lumen rating has no meaning on a lock).
- riding_discipline -> touring_bikepacking then_ask rack/pannier facets: supported by wiki_pannier's front/rear touring-pair sizing split.
- riding_discipline -> mountain_trail then_ask helmet_type: supported by wiki_helmet's description of distinct road/mountain/full-face forms.
- riding_discipline -> ebike then_ask computer_sensor_compatibility: supported by wiki_computer noting dedicated sensor/connectivity needs.

Noise (spec-sheet rows seen but not made a facet):
- Helmet weight (grams): varies continuously by model/size, not a buyer decision axis distinct from type/ventilation already captured.
- Helmet color/graphic: cosmetic, not expertise.
- Lock key vs combination: real distinction but didn't clear the research budget to source properly; left as an open gap rather than guessing.
- StVZO (German road-legal light standard) and ANSI/NEMA FL1 runtime/impact test: could not confirm with a page I actually fetched (cateye.com was down for maintenance; the FL1 Wikipedia page has no content; CPSC.gov and REI blocked the fetch) — left out rather than cited unseen.
- Rack/pannier numeric weight capacity (kg): Thule and Topeak product pages were JS-rendered with no server-side numbers in the fetched HTML; left pannier_size_class and rack_mount_type categorical instead of inventing a kg range.
- Child seat weight limit / minimum age in pounds and months: only one source (wiki_childseat) saw the actual numbers; per the two-source rule for numbers, kept the facet qualitative (mount position only) instead of stating the figure.
- Bell: no governing standard or expert-contested spec found; genuinely low-expertise accessory, left out of accessory_type to keep the register's depth meaningful rather than padding to a 9th type with one facet.
- Fender/mudguard, kickstand, mirror: same reasoning as bell — no sourced expert axis found this run: noted as an open gap, not modeled.

Corrections: none (first run for this slug; bicycle-accessories/ was empty before this session).

Corrections (2026-10-26):
- light_output_lumens: dropped the invented 50–1500 range (niterider, the only numeric source, runs 75–1,200; wiki_light has no numbers) — facet is now unit-only, qualitative.
- lock_form_factor: added a `smart_lock` value, sourced to wiki_lock's own external-links list of app/keyless lock testing (ART Foundation); did not add a separate keyless-unlock facet — check.md only said "consider" one, and no second source for its specs was fetched this run.
- vocabulary: added AS/NZS 2063 (wiki_helmet), ART (wiki_lock external links — Dutch ART Foundation), Dunlop valve (wiki_presta), and Smart lock (new value above) — each had a sibling value already defined but was itself missing.
- references[wiki_lock].supports and judgements[1].claim: corrected the Sold Secure Gold citation — the sourced number is two Gold-rated locks broken in 10 seconds, not the all-locks-tested 42-second figure.
- riding_discipline: added a skip_if_known entry scoping the question away from lock/light/pump_or_repair_kit/bottle_cage/child_seat, since its branches only ever changed something for touring, mountain_trail and ebike.
- riding_discipline.rationale: hedged "wants"→"often wants" and "needs"→"sometimes needs" for the mountain-helmet and e-bike-sensor claims, since neither source states that causal link directly (low-severity, so softened wording rather than fetching a second source).