[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"branding":3,"analytics":7,"article-researchers-fingerprint-llms-by-how-they-behave-not-what-they-say":10,"sections":34},{"siteName":4,"siteTagline":5,"publisherName":4,"contactEmail":6},"The Revision","Tech news, decoded.","editor@therevision.news",{"gaMeasurementId":8,"adsenseClientId":9},"G-ZW2MV82GYR","ca-pub-8533917693782264",{"article":11},{"id":12,"slug":13,"title":14,"dek":15,"body_md":16,"tags_json":17,"published_at":18,"created_at":19,"updated_at":20,"status":21,"review_note":22,"review_notes":23,"image_url":22,"persona_id":22,"persona_name":22,"section":24,"tags":25,"sources":29,"feedback":33,"feedback_at":22,"cost_usd":33,"total_tokens":33},7916,"researchers-fingerprint-llms-by-how-they-behave-not-what-they-say","Researchers Fingerprint LLMs by How They Behave, Not What They Say","A new method identifies which AI model powers a coding agent by watching its behavior, not its words.","Turns out you can tell which AI model is driving a coding agent just by watching how it works, not what it writes.\n\nResearchers built a system called LIDAR that fingerprints large language models running inside coding-agent harnesses - the tools that let an LLM inspect a repository, call functions, and edit files. Instead of analyzing a model's text output or token probabilities, LIDAR runs three paired probes that trigger controlled scenarios: verifying a change after an edit, recovering from a transient failure, and resolving conflicts between a specification and a test. It compares the resulting trajectories against clean reference behavior using a lightweight probabilistic classifier, and needs no access to model weights, logits, or provider internals - it works purely by observing black-box behavior. Tested across 36 models from seven families and two separate agent harnesses, LIDAR outperformed four existing fingerprinting and API-auditing baselines on accuracy.\n\nSwapping the model behind an agent can quietly change how it handles risk - whether it verifies its own edits or recovers safely from a failure - and most users have no way to know which model is actually doing the work. That is a real problem for anyone trusting a tool marketed as running on a specific model without a way to check the claim, and it hands auditors a method for catching providers who quietly substitute cheaper models behind the scenes.\n\nIt is a clever trick, though the same technique that catches a mislabeled agent could just as easily help a rival fingerprint - and copy - your stack.","[\"ai\",\"coding-agents\",\"security\",\"llm-fingerprinting\"]","2026-09-25T04:00:00.000Z","2026-09-26T06:57:10.814Z","2026-09-26T06:57:16.961Z","published",null,[],"ai",[24,26,27,28],"coding-agents","security","llm-fingerprinting",[30],{"name":31,"url":32},"arXiv cs.AI","https:\u002F\u002Farxiv.org\u002Fabs\u002F2609.28559",0,{"sections":35},[36,40,44,49,54,59,63,68,73,78,83,88,93,98],{"name":37,"slug":24,"count":38,"latest_published_at":39},"AI",4624,"2026-09-25T21:57:05.000Z",{"name":41,"slug":27,"count":42,"latest_published_at":43},"Security",748,"2026-09-26T01:30:00.000Z",{"name":45,"slug":46,"count":47,"latest_published_at":48},"Policy","policy",392,"2026-09-25T18:44:30.000Z",{"name":50,"slug":51,"count":52,"latest_published_at":53},"Deals","deals",258,"2026-09-26T09:00:00.000Z",{"name":55,"slug":56,"count":57,"latest_published_at":58},"Hardware","hardware",185,"2026-09-25T15:00:22.000Z",{"name":60,"slug":61,"count":62,"latest_published_at":53},"Science","science",144,{"name":64,"slug":65,"count":66,"latest_published_at":67},"Consumer Tech","consumer-tech",133,"2026-09-26T07:30:06.000Z",{"name":69,"slug":70,"count":71,"latest_published_at":72},"Software","software",90,"2026-09-25T20:55:00.000Z",{"name":74,"slug":75,"count":76,"latest_published_at":77},"Dev Tools","dev-tools",84,"2026-09-26T04:20:58.000Z",{"name":79,"slug":80,"count":81,"latest_published_at":82},"Startups","startups",76,"2026-09-25T18:33:59.000Z",{"name":84,"slug":85,"count":86,"latest_published_at":87},"Gaming","gaming",48,"2026-09-25T18:35:21.000Z",{"name":89,"slug":90,"count":91,"latest_published_at":92},"General","general",46,"2026-09-25T02:12:57.000Z",{"name":94,"slug":95,"count":96,"latest_published_at":97},"Reviews","reviews",30,"2026-09-24T20:07:31.000Z",{"name":99,"slug":100,"count":101,"latest_published_at":102},"How-To","how-to",6,"2026-06-16T09:00:00.000Z"]