{"type":"post","id":"castle-training-natural-language-search-before-the-first-6a8432","slug":"castle-training-natural-language-search-before-the-first-6a8432","title":"CASTLE: training natural language search before the first real query","description":"Why CASTLE changes the cold-start data problem Thesis The useful unit in this search cold start is a query paired with a behavior-grounded relevance distinction not a plausible query alone. Airbnb reports CASTLE generates queries from contrastive listing pairs based","retrieval_nugget":"Why CASTLE changes the cold-start data problem Thesis The useful unit in this search cold start is a query paired with a behavior-grounded relevance distinction not a plausible query alone. Airbnb reports CASTLE generates queries from contrastive listing pairs based","published_at":"2026-10-13","updated_at":"2026-10-13","record_date":"2026-10-13","date_kind":"published_at","topics":[],"source_urls":["https://airbnb.tech/ai-ml/castle-training-natural-language-search-before-the-first-real-query"],"schema_version":"newruntime-agent-readable-v0.2","stable_id":"post:castle-training-natural-language-search-before-the-first-6a8432","status":"published","visuals":[],"editorial_provenance":{"schema_version":"newruntime-editorial-copy-v1","content_status":"source_grounded_final","final_copy_sha256":"sha256:b9288fd187382114ff9a4a121d0ea0bcea7d2bae697078f0629ae149ca635cc8","reviewed_at":"2026-10-13T20:07:20.881Z","source_evidence_count":1,"verified_claim_count":3,"site_analysis_schema_version":"newruntime-site-analysis-v1","site_object_kind":"field_note","observed_fact_count":3,"implication_count":2,"watch_condition_count":1,"related_record_count":0},"analysis":{"schema_version":"newruntime-site-analysis-v1","object_kind":"field_note","thesis":"The useful unit in this search cold start is a query paired with a behavior-grounded relevance distinction, not a plausible query alone.","observed_facts":[{"text":"Airbnb says CASTLE generates queries from contrastive listing pairs derived from de-identified booking sessions, selected according to privacy permissions.","source_urls":["https://airbnb.tech/ai-ml/castle-training-natural-language-search-before-the-first-real-query"]},{"text":"Airbnb reports KL divergence of 1.01 against real query distributions versus 9.33 for its best baseline.","source_urls":["https://airbnb.tech/ai-ml/castle-training-natural-language-search-before-the-first-real-query"]},{"text":"Airbnb reports 91–93% expert agreement across three raters reviewing 200 triplets.","source_urls":["https://airbnb.tech/ai-ml/castle-training-natural-language-search-before-the-first-real-query"]}],"mechanism":"The system conditions a language model on both listings and asks for a query satisfied by the positive but not the negative, so the relevance label follows the observed choice rather than a separate model judgment. For pairs without booking history, Airbnb adds an LLM Virtual Judge.","why_now":"Airbnb says natural-language search had to be trained before real user queries existed, while synthetic-query methods risk mismatching actual guest phrasing and require labels.","implications":["Search teams facing a traffic cold start can treat existing choice behavior as structured supervision for both query generation and relevance, rather than relying only on generated text plus post-hoc judgments.","This may reduce circularity in synthetic labeling, while leaving gaps where behavior signals are unavailable."],"evidence_boundary":"These metrics and implementation details are Airbnb's own published account; the supplied source does not provide independent replication or enough detail to assess all deployment effects.","watch_conditions":["Whether later evaluations show the same alignment and label quality on new markets, listing types, or independently reproduced datasets."],"related_records":[],"new_branch_reason":"No prior New Runtime record is supplied for this specific joint query-and-label construction."},"editor":{"role":"editor","name":"Andrey Reshetnikov","profile":"https://newruntime.com/owner-profile.md","profile_json":"https://newruntime.com/owner-profile.json","same_as":["https://www.linkedin.com/in/reshetnikov1/","https://t.me/lapetuse"]},"routes":{"html":"https://newruntime.com/posts/castle-training-natural-language-search-before-the-first-6a8432/","markdown":"https://newruntime.com/posts/castle-training-natural-language-search-before-the-first-6a8432.md","json":"https://newruntime.com/posts/castle-training-natural-language-search-before-the-first-6a8432.json"},"next_reads":[{"type":"collection","path":"/posts/","url":"https://newruntime.com/posts/","title":"Field Notes","reason":"Open the latest editorial analysis.","media_type":"text/html","json_url":"https://newruntime.com/posts.json"},{"type":"collection","path":"/source-ledger.json","url":"https://newruntime.com/source-ledger.json","title":"Source Ledger","reason":"Inspect the public source evidence graph.","media_type":"application/json"}]}