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DUET: Joint Exploration of User–Item Profiles in Recommendation System YueChen1,,YifeiSun1,,LuWang2,†,FangkaiYang2,PuZhao2,MinjieHong3,YifeiDong4,MinghuaHe2, NanHu2,JianjinZhang2,ZhiweiDai2,YuefengZhan2,WeihaoHan2,HaoSun2, QingweiLin2,WeiweiDeng2,FengSun2,QiZhang2,SaravanRajmohan2,DongmeiZhang2 1PekingUniversity2Microsoft3ZhejiangUniversity4KTHRoyalInstituteofTechnology *Equalcontribution†Correspondingauthor Abstract

User History: Item History: User History: Item History:
• Misfits (Punk) • Review: • Misfits (Punk) • Review:
• I r o n M a iden " P o l i s he d P o p " • I r o n M a iden " P o l i s he d P o p "
Traditionalrecommendationsystemsrepresent ( M e t al ) • R e v i e w : " G r e a t ( M e t al ) • R e v i e w : " G r e a t
6202 rpA 51 ]RI.sc[ 1v10831.4062:viXra • • Parliament Funk Bass"
usersanditemsasdensevectorsandlearnto Parliament Funk Bass"
------------------------------------- --- --- ----------- ------------------ ------ ------------------
(Funk) • Meta: "80s Rock" (Funk) • Meta: "80s Rock"
aligntheminasharedlatentspaceforrelevance
Duet Independent
--- --- --- --- ----- ------------ ---
estimation. RecentLLM-basedrecommenders (Joint Alignment) Generation
instead leverage natural-language representa-
---------------- ---------------- ----------- ------------- ------------- ------------- -------------
User Profile: Item History: User Profile: Item History:
tionsthatareeasiertointerpretandintegrate Enthusiast of A peak-era FUNK- Fan of HEAVY A highly rated POP-
FUNK and SOUL. ROCK album with METAL and ROCK album with
--- --- --- --------------- ---------------- ---------- ----------------
withdownstreamreasoningmodules. Thispa- Values technical genre-blurring PUNK. Prefers polished
mastery creativity. dark themes. production.
--- --- --- ------- ----------- ------------ -----------
textual
per studies how to construct effective Semantic Alignment ✘ Semantic Mismatch
profilesforusersanditems,andhowtoalign
themforrecommendation. Acentraldifficulty Figure1: DUETalignsrawuseranditemdatabytrans-
forming them into textual profiles within a shared se-
--- --- --- ------------ ------------ --------------- ------------
isthatthebestprofileformatisnotknownapri-
manticspace.
ori: manuallydesignedtemplatescanbebrittle
andmisalignedwithtaskobjectives. Moreover,
-------------------------------- --- --------- ------------ ------------ -------------------- ---
to introduce semantically rich, human-readable
generatinguseranditemprofilesindependently
mayproducedescriptionsthatareindividually representationsforrecommendation(Wangetal.,
plausible yet semantically inconsistent for a 2025;Zhang,2024;Baoetal.,2023;Hongetal.,
specificuser–itempair. WeproposeDUET,an
---------------------- ---------------- --- -------------------------- --- ------------------- ---
2025a,b,c;Wangetal.,2024). Anaturaldirectionis
interaction-awareprofilegeneratorthatjointly
toreplacelatentvectorswithtextualuseranditem
producesuseranditemprofilesconditionedon
profilesthatcanbeinspected,edited,andreusedby
both user history and item evidence. DUET
----------------- ------------------ ---- --- --- --- ---
downstreamcomponentsincorporatedwithLLMs.
follows a three-stage procedure: it first turns
--------------------- ---------- -------------- --- --- --- ---
However,existingLLM-basedapproachesremain
rawhistoriesandmetadataintocompactcues,
then expands these cues into paired profile limited in two important ways. First, directly
promptsandthengenerateprofiles,andfinally promptinganLLMwithrawuseranditemhisto-
optimizesthegenerationpolicywithreinforce-
riestoobtainrecommendationsoftenyieldsnoisy
mentlearningusingdownstreamrecommenda- andincompletesignals,especiallywhenhistories
tionperformanceasfeedback. Experimentson
-------------------------- --- ------------- --------- ------------------------ --- -------------
are long, sparse, or heterogeneous (Wang et al.,
threereal-worlddatasetsshowthatDUETcon-
2025). Second, profile-based methods typically
--- --- --- -------------- ------------- ------- ---------
sistentlyoutperformsstrongbaselines,demon-
relyonmanuallydesignedtemplatesorhandcrafted
stratingthebenefitsoftemplate-freeprofileex-
attributes,whichrequiressubstantialhumanengi-
plorationandjointuser–itemtextualalignment.
Project code page: https://github.com/duet- neering and constrains the representation space.
review/duet_code. More fundamentally, many approaches generate
userprofilesanditemprofilesindependently,with-
1 Introduction
out modeling how user preferences and item se-
--- --- --- ------------ -------- ----------- ------------
Traditional recommendation systems represent manticsinteractatdecisiontime(Yangetal.,2023;
Xietal.,2024).
usersanditemsasdensevectorsandlearntoalign
theminasharedlatentspaceforrelevanceestima- Toaddressthesechallenges,wepropose DUET,
tion (Covington et al., 2016; Wu, 2023). While ajointuser–itemprofilegeneratorthattakesboth
effective,suchembeddingsareopaque: theyoffer userhistoryanditemhistoryasinputandproduces
limitedinterpretabilityandmakeitdifficulttoan- a paired set of profiles for the interaction. Cru-
alyzewhyanitemisrecommended. Recentwork cially, DUET doesnotrequireprofiletemplates: it
thereforeleverageslargelanguagemodels(LLMs) istrainedwithreinforcementlearningusingfeed-

back from downstream recommendation perfor- asseeninworkslikeCRESDUP(Chenetal.,2007) mance,enablingittoexploreanddiscovereffective andUPCSim(Widiyaningtyasetal.,2021). While profileformatsautomatically. Figure1illustrates foundational,thesemethodswerelimitedbytheir whyjointprofilingmatters. Theuserhaslistened rigid,hand-engineeredfeatures. Morerecently,the toMisfits(punk),IronMaiden(metal),andParlia- adventofLargeLanguageModels(LLMs)hasen- ment(funk),whilethecandidatealbumisdescribed abledashifttowardsgeneratingprofilesinnatural byreviewssuchas“polishedpop”and“greatfunk language. Studies such as KAR (Xi et al., 2024), bass”andametatag“’80srock.” Consideringboth GPG(Zhang,2024),PALR(Yangetal.,2023),and sides together, DUET can reconcile these signals LettinGo (Wang et al., 2025) leverage LLMs to intoacompatibleinterpretation(e.g.,highlighting createtextualuserprofilesfrombehavioraldata. A the user’s funk/soul affinity and the item’s funk- keylimitationoftheseapproachesistwofold: they rockcharacter). Incontrast,independentlygener- relyonstaticorpre-definedtemplatesforprofile atedprofilesmayamplifydifferentfacets,summa- generation,andtheyoftenfocusexclusivelyonuser rizingtheuseras“heavymetal/punk”whilesum- profiles,neglectingtherich,expressiveinformation marizingtheitemas“pop-rock”,whichresultingin inherentinitemsandthecomplexdynamicsofuser- asemanticallymismatchedpairthatobscuresthe iteminteractions. Incontrast,ourworkintroduces truerelevancesignal. anewparadigmwherebothuseranditemprofiles DUETproceedsinthreestages. First,rawhisto- arenotfixedbutaredynamicallyexploredandop- ries and metadata are distilled into minimal cues timizedinasharedsemanticspacetodirectlyalign thatcapturecompactbutinformativesignals. Sec- withrecommendationperformance. ond, the model expands cues into richer profile prompts to generate textual profiles, allowing ex- 2.2 ReinforcementLearningforLLM-Based plorationoveralternativeprofilestructuresandem- RecommendationSystems phases. Third,theresultingprofilesareconsumed ReinforcementLearning(RL),particularlythrough bydownstreamrecommenders,andtheirtaskfeed- techniqueslikeRLHF,hasbecomeacoremethod backisusedtooptimizetheprofilegenerationpol- for aligning LLMs with specific objectives. This icy. By coupling both sides in a shared semantic approach has been adapted for recommendation space,DUETlearnsuserprofilesthatreflectwhat tasks (Wang et al., 2025; Lin et al., 2025; Deng kindsofitemsauserprefersanditemprofilesthat etal.,2025),butexistingeffortsoftenfacekeylimi- reflectwhatkindsofusersanitemappealsto. tations. Theyfrequentlyrelyonofflinerewardmod- Ourcontributionsareasfollows: els(Jeongetal.,2023;Chenetal.,2025;Heetal., • Werepresentusersanditemsasnatural-language 2025; Liu et al., 2025) that do not adapt in real- profiles and align them in a shared semantic timetosystemfeedback,asetupthatrisksissues space,extendingtheclassicvector-basedalign- like reward hacking (Skalse et al., 2025). Other mentprincipletointerpretabletextualrepresenta- methods(Sunetal.,2024;Luetal.,2024)restrict tions. themselvestoofflinepreferencetuning(e.g.,DPO), • We introduce an exploration-based framework which can easily overfit on static datasets. Our thatstartsfromcue-basedinitialization,expands framework, DUET,overcomesthesechallengesby cuesintocandidateprofiles,andjointlyoptimizes integrating RL into a closed-loop system where user and item profiles with downstream recom- downstreamrecommendationperformanceserves mendationfeedbackviareinforcementlearning, asthereal-timerewardsignal,allowingforthedy- avoidingrigidtemplates. namicandinteractiverefinementoftextualprofiles. • Extensiveexperimentsacrossmultiplereal-world datasets show that DUET consistently outper- 3 Method formsstrongbaselines,validatingbothjointpro- filingandfeedback-drivenprofileoptimization. DUET is a closed-loop framework that trans- forms raw user–item interaction histories into 2 RelatedWork performance-aligned textual profiles through learnedrepresentationstrategies. AsshowninFig- 2.1 ProfilesinRecommendation ure 2, DUET consists of three stages. (1) Cue- Earlyrecommendationsystemsprimarilyreliedon Based Initialization distills interaction histories pre-definedprofilesbasedonstructuredattributes, intoconciseevidence-basedcues. (2)JointExplo-

CUE-BASED INITIALIZATION JOINT EXPLORATION ON-POLICY OPTIMIZATION

Item DU Duet
ItemHistory ET
Initial CUE
Rated: Baba Is You (5★)
User: “Prefers retro puzzle games”
Reviewed: “I love logic-
Item: “Retro-style indie puzzle game”
based puzzle games.” Profile Prompt
--- --- --- -------------------- --- --- -------------- --- --- --- --- ---
Rated: The Witness (5★)
User: “Describe the user's typical
Rated: Fez (4★) puzzle-game preferences … 𝑃𝑟𝑜𝑓𝑖𝑙𝑒1 𝑃𝑟𝑜𝑓𝑖𝑙𝑒2 𝑃𝑟𝑜𝑓𝑖𝑙𝑒𝑛
--- --- --- --------------- --- ------------------------- --- --- ----------------- --- -------- ---
Item: “… item's core mechanics…
Profile Downstream Task Env
----------- --- --- ----------------------- ---- --------------------------------- --- ------- --------------------- --- --- ---
User User: “A player who enjoys logic-
UserHistory intensive indie puzzle games,
Category: Indie Puzzle Ranking correctness
prefers retro visual aesthetics…”
Game &format Reward
--- --- --- ---- --- --- --- --- -------------- --- --- ---
Reviews:
Item: “A retro-style indie puzzle
“Challenging logic game featuring challenging Group Computation
--- --- --- -------------------- ------------------------ ------------------------------- --- --- ------------------- --- ---- ---
mechanics.” logic mechanics that appeal to
“ R e t r o p ix e l- a rt st y l e . ” hardcore puzzle players.” 𝐴𝑑𝑣1 𝐴𝑑𝑣2
“ H a r d b u t re w a r d i n g . ” 𝐴𝑑𝑣𝑛
Figure2: OverviewoftheDUETframework.
ration via Adaptive Profile Prompt Discovery 3.2 Cue-BasedInitialization
jointly explores user-item’s profile prompts that
---------- -------- ----------- -------- --------------- -------- -------- --------- -------- -------- --- ---------
Raw user histories and item metadata are often
define how user and item profiles should be writ-
noisy,redundant,andnotdirectlysuitableforpro-
ten. (3)OptimizationviaOn-policyExploration
fileconstruction. Toaddressthis,DUETintroduces
--- --- --- --- --- --- ----------------- --- ---------------------------- --- --- ---
jointlyoptimizesuseranditemprofilesunderdown-
theconceptofcues:
concisehypothesesthatsum-
streamrecommendationfeedback.
marize minimal but informative aspects of users
------------------- ------ --- ------------------------- ------- -------- -------------- ------------ --------------- -------------- ------- --------
All three stages are realized through a single
and items. These cues act as lightweight seeds,
passinputandoutput: cueextraction,self-prompt
which are deliberately underspecified so that the
construction,andprofilegenerationareproduced
systemcansubsequentlyexplorericherprofilefor-
inasinglesequence-to-sequencegenerationpass
mats.
atinferencetime,enablingefficientdeployment.
Definition1(Cue). Acueisaminimaltextualhy-
--- --- --- --- --- --- ----------------- --- ------------------------ --- --- ---
3.1 ProblemFormulation
pothesisderivedfromhistoricaldatathathighlights
WeformulateprofilegenerationinDUETasanon- one potential aspect of a user’s preference or an
policyreinforcementlearningproblem,motivated item’scharacteristic. Ratherthanaimingforcom-
bytheabsenceofanytextualgroundtruthdefining pleteness, cues capture partial but salient signals
an optimal user or item profile. Profile quality is thatserveasstartingpointsforprofileexploration.
evaluatedsolelybyitsfunctionalutilityinafixed
To extract cues automatically, the LLM is
--- --- --- --- --- --- ---------- ---- -------------- --- --- ------
recommendationenvironment.
prompted to summarize minimal but informative
---- ---------- --- ------------ ------ ------- ------------------------ ------------ ------- ----------------- --------------- ---
DUET is modeled as a generative policy π θ in-
aspectsofuseroritemdata. Forexample,givena
teractingwithafrozendownstreamrecommender.
user’sinteractionhistory,themodelisguidedwith
For each user–item pair, the state is defined as
-------- --------- ----- --- -------- ---------- --- --- --- --- --- ---
instructionssuchas:
s = {H ,H },whereH andH denotetheuser
------ ----------- --- ---- ------------- --- --- --- --- --- --- ---
u i u i
and item interaction histories. An action corre- CueExtractionPrompt
spondstoasingle-passjointgeneration
“Fromthehistorybelow,analyzetheuser’s
a = {C u ,S u ,P u ,C i ,S i ,P i }, historicalinteractionstounderstandprefer-
ences,ratingbehavior,reviewsentimentor
where (C ,C ) are cues distilled from his-
----- ----- ----- ---- --------- --------- --- --- --- --- --- ---
u i
anyotherdimension. Keepthedescription
-------- ------------ ----------- --- ----------- ------- ------------------ --- ------------------ --- --- ---
tory, (S u ,S i ) are constructed user-item’s profile
prompts,and(P ,P )arethefinaltextualprofiles. conciseandavoidfullsentences.”
u i
Thepolicyπ (a s)definesajointdistribution
---------- --- -------------------------------- --- --- --- --- --- --- --- --- ---
θ
over the entire generation sequence. As an on- This lightweight guidance allows the LLM to
policy agent, DUET is optimized using rewards maprawhistoriesandmetadataintocompacttex-
from its own sampled generations rather than by tualcues. Thedetaildexampleofcuecanbefound
imitatingfixedsummaries. inAppendixA.3.
------------------------ --- --- --- --- --- -------------- --- --- --- --- ---
3.3 JointExplorationviaAdaptiveProfile Single-PassInput
PromptDiscovery Task:Generatestructuredprofilesfortheuseranditemfrom
historicaldata.
Aftercueextraction,DUETdoesnotdirectlysum- Combined Context: [User History H u ] + [Item
History H i ]+[Avg Ratings]
------------------------------------ --- --- --- --- --- ---------- ------- ---------- -------- --- --- ---
marizeuserinterestsoritemattributes. Instead,it
“First,extractaconciseCueforbothuseranditem.Second,
explores the space of profile construction strate-
-------- --- --------- ---------- ------------ --- ------- --- --- --- --- --- ---
basedonthecues,constructaProfilePromptthatdefines
gies—natural-languagepromptsthatdefinethefor- thedescriptionlogic.Finally,generatetheProfileguidedby
theconstructedProfilePrompt.”
mat,abstractionlevel,andattributeselectionlogic
↓DUETForwardPass↓
usedtogenerateprofiles. Explorationistherefore
-------------------------------------------- --- --- --- ---------------------- --- --- ----------------- --- --- --- --- ---
performedoverhowprofilesshouldbeconstructed, Single-PassOutput
User
ratherthanoversuperficialtextualparaphrases.
Cue:“prefersnostalgiclogic-basedchallenges”
For each user–item pair, DUET intro- Profileprompt: “Focuson1990svisualaestheticsand
duces an explicit intermediate variable, the strategicdepth.”
----- --- -------- ------------ --- --------- --- ---------------- --------- --- ----- ----------- ------------
Profile: “A player who seeks retro-style visual charm
constructed_prompt,whichservesasadiscrete
pairedwithdeepstrategicreasoning.”
and interpretable profile prompt S. This profile
--- ------------- --- ------- ------ --- ------------ --- --- --- --- --- ---
Item
promptisashortnatural-languageinstruction(e.g.,
Cue:“retro-styleindiepuzzlewithhighdifficulty”
“Describetheuser’stypicalgamingpreferencesand
Profile prompt: “Describe pixel-art graphics and
--- --- --- --- --- --- --- ------- ------- --------- --- --------- ------------
engagementpatterns”)thatspecifieswhataspects intellectualdifficultytomatchlogicpreference.”
Profile:“A2Dexperiencefeaturingpixelatednostalgia
to describe and how to organize them, without
--- -------- --- ------ -------- ----- ------- --- --- --- --- --- ---
andchallengingmechanicsthatdemandlogicaldeduction.”
containingtheprofilecontentitself. Conditioned
---------------------------------- --- --- --- --- --- ----------- --- --- --- --- --- ---
onS,themodelgeneratesthefinaluseranditem Figure3: Single-passgenerationinDUET: cueextrac-
profiles. tion,profileprompt(constructedprompt),andprofile
--------- --- --- --- --- --- --- ------------------------------------------------ --- --- --- --- ---
generationareproducedinonepassforbothuserand
Exploration is driven by treating the profile
----------- --- --- --------- ----------- --- ----------- --- --- --- --- --- ---
item.
promptS asastochasticactionsampledfromthe
------- --- --------------------------------- --------------------------- --- --- --- --- --- --- --- --- ---
policyπ (S Cue). Duringtraining,theagentsam-
θ
plesdifferentprofilepromptinstructions,executes
andintellectualdifficulty”tomatch. RLreinforces
---------------------------- --- --- --- --- ---------------- --- ---------------------------------- --- --- --- --- ------------
themtogenerateprofilepairs(P ,P ),andreceives
u i
thissharedsemanticdirection,suppressingirrele-
a reward based on downstream recommendation
--------- --- ----------------------------------- ------------- --- -------------- --- ------------ ------------- -------- --- ----- ----------------
vant signals and forcing the final profiles to con-
accuracy. Thepolicyisoptimizedtoreinforcepro-
verge into a shared semantic space of nostalgia
filepromptsthatconsistentlyyieldhigherrewards,
andlogic,significantlyimprovingrecommendation
enablingthemodeltoactivelysearchforeffective
accuracy.
profileconstructionformats.
Thisprocessisrealizedasaunifiedgeneration
3.4 OptimizationviaOn-policyExploration
pass,
On-policy optimization. We train the profile
--- --- --- --- --- --- --- --------- ------------- --- --- -------- -----------
O = [ Cue → profilepromptS → Profile], generator π in an on-policy manner against a
(cid:124)(cid:123)(cid:122)(cid:125) (cid:124) (cid:123)(cid:122) (cid:125) θ
--- ------------------------------------ --- --------- ------------------ --------- -------------------------------------- --- --- --- --- --- ---
(cid:124) (cid:123)(cid:122) (cid:125)
Context ProfileConstructionPrompt Execution frozendownstreammodelf, whichservesasthe
(1) environment critic. For each sampled user–item
--- --- --- --- --- --- --- ----------- ------- --- ---- ------- ---------
wheretheprofilepromptS parameterizesthepro- pair (u,i), the policy generates (P ,P ) and re-
u i
filegenerator. Atinferencetime,DUETcollapses ceivesascalarrewardbasedonthepredictionac-
thelearnedprofilepromptdistributionandgreed- curacy of f(P ,P ). The policy parameters are
u i
ilyexecutestheoptimalprofilepromptinasingle updatedtoreinforcegenerationsthatleadtolower
forwardpass,introducingnoadditionallatency. predictionerror.
------------------------------------------- --- ---------- ------ ------------ -------- ------- --------------------------- --- --- --- --- -------------
Example of profile prompt Exploration. As
Continuousfractionalreward. Usingdiscrete
illustrated in Figure 3, DUET resolves this by
integerratingsasrewardsleadstosparseandunsta-
identifying a shared context in a single forward
----------- --- -------- ------- --- -------- ------- --- --- --- --- --- ---
blefeedback,asnear-misspredictions(e.g.,predict-
pass. ThepolicyextractsacoordinatedCue(e.g.,
ing4foragroundtruth5)receivethesamepenalty
“prefersretropuzzlegames”)andconstructsapro-
assevereerrors. Toprovidedenseandinformative
---- ------ ---- ------------------- --- --- -------- --------------- --- ---------------------------- --- --- ---
file prompt (the constructed_prompt) that in-
feedback,wedefineacontinuousfractionalreward:
structsthemodeltohighlight“nostalgicaesthetics
and strategic logic” for the user, while simulta-
------- ---------- ------ ---------- ---------- ----- -------- --- ------- --- ---- ------ --------
y −yˆ
R (u,i) = 1− ui ui , (2)
neously describing the item’s “pixel-art graphics perf
M

where yˆ ui = f(P u ,P i ) is the predicted relevance ingsettingbasedondownstreampredictedrating score and M is the maximum rating gap (e.g., scores. For each observed user–item interaction, M = 4 for a 1–5 scale). This reward provides we randomly sample nine items that the user has fine-grainedgradientsthatencourageincremental not interacted with to form a candidate set of ten improvementsinrecommendationaccuracy. items, which are ranked in descending order ac- We adopt Group Relative Policy Optimization cordingtotheirpredictedratings. Theground-truth (GRPO) (DeepSeek-AI et al., 2025) to optimize interacted item is treated as the only positive in- theprofilegeneratorundertheabovereward. The stance,andweadoptNDCG@Kastheevaluation downstreamrecommenderf isfrozenthroughout metric, with K set to 1, 5, and 10, to assess how training, which yields a stable policy optimiza- effectivelythelearnedprofilessupportcorrectitem

tionsettingandpreventsrewarddriftorfeedback- ranking.
Baselines We compare our method with several
inducedrepresentationcollapse.
representative baselines. 10H directly uses the
--- --- --- --- -------------- ---------- --- -------- --------
4 Experiment mostrecentinteractionhistoriesforpredictionwith-
outconstructingexplicitprofiles. KAR(Xietal.,
--- --- --- --- -------------------------------- --- --- ------------ ---
4.1 ExperimentalSettings
2024)augmentsrecommendationmodelswithex-
Datasets. Experiments were conducted on three ternalreasoningknowledgeaboutuserpreferences
widelyusedreal-worlddatasets. AmazonMusic andfactualknowledgeaboutitemsextractedfrom
(Music) and Amazon Book (Book) are derived LLMs,whicharetransformedintotask-compatible
fromtheAmazonProductdataset1,whileYelpis representations. RLMRec(Renetal.,2024)lever-
fromtheYelpOpendataset2. Alldatasetsinclude agesLLMstolearnsemanticuseranditemrepre-
userreviews,ratings,andrichtextualinformation. sentationsfromtextualsignalsandalignsthemwith
WeusedthefullAmazonMusicdataset,butonly collaborativerelationalinformationthroughcross-
subsets (latest two months for Book and six for viewrepresentationlearning. PALR(Yangetal.,
Yelp). Data was split by timestamp into training, 2023)fine-tunesalargelanguagemodelasarank-
validation,andtestsetstopreventinformationleak- ing component that selects preferred items from
age(Jietal.,2023). retrievedcandidatesexpressedinnaturallanguage.
EvaluationMetrics LG (LettinGo) (Wang et al., 2025) explores di-
For each observed user–item interaction (i.e., verseuserprofilecandidateswithLLMsandaligns
a review record), we construct the evaluation profilegenerationwithdownstreamrecommenda-
instance based on the user’s interaction history tionperformanceviapreferenceoptimization. Rea-
strictly prior to the corresponding timestamp. son4Rec(Fangetal.,2025)introducesadelibera-
tiverecommendationframeworkthatincorporates
Specifically,theuser’srecenthistoricalinteractions
beforethecurrentinteractionareusedtogenerate explicitstep-wisereasoningoveruserpreferences
auserprofile,whilehistoricalreviewsfromother toguideratingprediction.
users are used to generate an item profile. The
-------------- ----------- ---------------- --- --- --- --- --- ---
4.2 MainResults
downstreamrecommendationsystemthenpredicts
theratingofthetargetitemconditionedontwoin- Table 1 presents a comparison of our proposed
puts: thegenerateduserprofile,andthegenerated method against five baselines on three datasets:
Amazon Music, Amazon Books, and Yelp. We
------------ ------------------------------- --- --- ------ ------------- ------ --- --------
itemprofile. Anexceptionisthe10Hbaseline,for
which the downstream model directly consumes use Qwen3-8B (Team, 2025) and LLaMA3-8B
therawrecentinteractionhistories. (Dubey et al., 2024) as both the profile generator
andthedownstreamrecommendationmodel,with
We evaluate performance using four widely
--------------- ----------- ------------------ ------- ------------ ----------- ----- ----------- -------
a prediction temperature of 0. In addition to rat-
adopted metrics (Wang et al., 2025; Fang et al.,
2025): MeanAbsoluteError(MAE),RootMean ingpredictionresults,wealsoreportranking-based
SquareError(RMSE),Accuracy,andF1score. evaluation results in Table ??, which assess the
effectivenessofthelearnedprofilesfromadown-
Inadditiontoratingprediction,wefurtherevaluate
thegenerateduseranditemprofilesunderarank- streamrankingperspective.
Overallsuperiorityoverstrongbaselines. As
--- --- --- --- -------------------------------------- --- --- --- ---
1https://cseweb.ucsd.edu/~jmcauley/datasets/ shown in Table 1, our method consistently out-
amazon/links.html
performs the strongest baselines across all three
--- --- --- --- -------- ------------- --------- ------ ---------
2https://business.yelp.com/data/resources/
open-dataset/ datasetsunderbothQwen3-8BandLLaMA3-8B.
------------- --- --- --- -------------------------------------- --- --- --- ---

Method Yelp AmazonMusic AmazonBooks MAE RMSE Acc F1(%) MAE RMSE Acc F1(%) MAE RMSE Acc F1(%) (%) (%) (%) Qwen3(8B) 10H 1.1235 1.9478 23.17 27.54 0.9102 1.4021 39.26 46.58 0.9314 1.4527 37.63 45.19 KAR(Xietal.,2024) 0.7396 1.2184 55.34 48.67 0.7483 1.1380 58.65 60.29 0.7098 1.0923 56.17 58.78 RLMRec(Renetal.,2024) 0.8197 1.3312 47.15 42.46 0.7438 1.1069 54.89 57.65 0.7812 1.1584 52.86 55.93 PALR(Yangetal.,2023) 0.7994 1.2876 48.53 43.19 0.6075 0.9531 57.35 56.77 0.7485 1.1187 54.24 56.38 LG(Wangetal.,2025) 0.6632 1.1047 56.18 48.95 0.4737 0.8834 62.37 57.09 0.5821 0.9416 59.35 60.57 R4Rec(Fangetal.,2025) 0.7028 1.1523 55.69 47.73 0.5654 0.9635 58.69 54.67 0.6397 1.0098 58.47 56.84 Ours 0.5126 0.9485 61.23 55.18 0.3937 0.7564 67.96 63.89 0.4612 0.9089 64.38 59.27 LLaMA3(8B) 10H 1.0864 1.9532 22.09 27.30 0.7917 1.3346 38.13 46.87 0.8064 1.3866 37.15 45.27 KAR(Xietal.,2024) 0.6427 1.1668 54.51 47.98 0.5726 0.9033 57.53 59.92 0.5892 0.9614 55.87 58.21 RLMRec(Renetal.,2024) 0.7428 1.3572 46.74 42.11 0.6076 0.9886 53.78 57.42 0.6226 0.9477 52.12 55.79 PALR(Yangetal.,2023) 0.7238 1.3265 47.72 43.29 0.5823 0.9222 56.73 59.31 0.5977 0.8855 55.06 57.62 LG(Wangetal.,2025) 0.6196 1.1289 56.03 51.24 0.5204 0.9369 61.92 59.50 0.5543 0.7967 58.95 60.39 R4Rec(Fangetal.,2025) 0.7586 1.0418 55.80 53.00 0.5442 0.7722 60.86 54.88 0.6029 0.8345 59.70 56.35 Ours 0.5367 0.9687 60.87 54.74 0.4680 0.8277 63.30 60.60 0.5092 0.9500 63.42 58.12 Table1: PerformanceonthreedatasetsusingQwen3(8B)andLLaMA3(8B). Method Yelp AmazonMusic AmazonBooks NDCG@1 NDCG@5 NDCG@10 NDCG@1 NDCG@5 NDCG@10 NDCG@1 NDCG@5 NDCG@10 10H 0.1823 0.2815 0.4928 0.1875 0.3796 0.5153 0.1841 0.3146 0.4263 KAR(Xietal.,2024) 0.2156 0.3298 0.5412 0.3018 0.4896 0.6015 0.2965 0.4715 0.5834 RLMRec(Renetal.,2024) 0.2419 0.3472 0.5587 0.3371 0.5434 0.6162 0.2748 0.4526 0.5719 PALR(Yangetal.,2023) 0.2494 0.3563 0.5691 0.3395 0.5247 0.6115 0.2627 0.4634 0.5538 LG(Wangetal.,2025) 0.3187 0.4685 0.5814 0.4012 0.5674 0.6489 0.3795 0.5189 0.6284 R4Rec(Fangetal.,2025) 0.2575 0.3792 0.5526 0.2928 0.5912 0.6343 0.3013 0.4928 0.5959 Ours 0.3390 0.4873 0.6008 0.5123 0.6165 0.7025 0.4288 0.5638 0.6599 Table2: RankingperformanceunderEASE-based(Steck,2019)hardnegatives. Under Qwen3-8B, our method achieves an accu- our approach reaches an NDCG@1 of 0.5619 racyof61.23%onYelp,67.96%onAmazonMu- and an NDCG@10 of 0.7443, clearly outper- sicand64.38%onAmazonBooks,surpassingLG forming the strongest baseline methods. Similar (LettinGo)(Wangetal.,2025)by5.05%,5.59% trendsareobservedonAmazonMusic,whereour and5.03%,respectively. Similarimprovementsare methodattains0.5347atNDCG@1and0.7331at observed under LLaMA3-8B, indicating that the NDCG@10, as well as on Amazon Books with gainsarestableacrossbackbonemodels. NDCG@1 of 0.4866 and NDCG@10 of 0.7107. Theseresultsindicatethatthelearnedprofilesen- Advantages over fixed-structure and delib- able more accurate identification and ordering of erative baselines. Compared with strong fixed- relevantitemswithincandidatesets,leadingtosu- structureordeliberativemethodssuchasKAR(Xi perior ranking quality in downstream recommen- etal.,2024)andReason4Rec(Fangetal.,2025), dation. Wefurtherevaluaterankingperformance our approach consistently achieves lower predic- under a more challenging setting using EASE- tion error and higher accuracy. For example, on based (Steck, 2019) hard negatives, and observe Amazon Books with Qwen3-8B, our method re- consistentimprovements;detailedresultsarepro- duces MAE to 0.4612, compared to 0.7098 for videdinAppendixB.2. KARand0.6397forReason4Rec,demonstrating moreeffectiveabstractionofuserpreferenceswith- 4.3 AblationStudy outrelyingonpredefinedreasoningtemplates. Consistent improvements in downstream Effectivenessofprofilegeneration,cue&strategy, ranking. Table??reportstherankingresultsun- anduser–itemjointoptimization. Table3reports der the Qwen3-8B backbone. Our method con- the ablation results under different design con- sistentlyachievesthebestperformanceacrossall figurations. Starting from the history-only base- three datasets and evaluation cutoffs. On Yelp, line (10H), introducing explicit profile genera-

Method Yelp AmazonMusic AmazonBooks
MAE RMSE Acc F1 MAE RMSE Acc F1 MAE RMSE Acc F1
10H(HistoryOnly) 1.1235 1.9478 23.17 27.54 0.9102 1.4021 39.26 46.58 0.9314 1.4527 37.63 45.19
Profile 0.7218 1.1863 55.48 48.09 0.6597 1.0218 58.67 57.48 0.6764 1.0469 57.14 57.68
Profile+Cue&Strategy 0.7085 1.1654 55.83 48.54 0.5708 0.9897 58.91 55.53 0.6389 1.0108 58.43 56.88
Profile+JointOpt.(LG(Wang 0.6632 1.1047 56.18 48.95 0.4737 0.8834 62.37 57.09 0.5821 0.9416 59.35 60.57
etal.,2025))
Profile+Cue&Strategy+ 0.5126 0.9485 61.23 55.18 0.3937 0.7564 67.96 63.89 0.4612 0.9089 64.38 59.27
JointOpt.(Ours)
Table3: AblationstudyondifferentdesignconfigurationsinDUETusingQwen3(8B).
Method Yelp AmazonMusic AmazonBooks
------ -------- ---- --- ----- --- ----------- --- ----- --- ----------- ---------
MAE RMSE Acc F1(%) MAE RMSE Acc F1(%) MAE RMSE Acc F1(%)
(%) (%) (%)
10H+30P 0.5126 0.9485 61.23 55.18 0.3883 0.7494 67.96 63.89 0.4612 0.9089 65.13 59.97
10H+50P 0.4909 0.9207 62.43 56.24 0.3924 0.7543 67.88 63.87 0.4553 0.9023 64.62 59.52
10H+70P 0.4987 0.9326 61.98 55.81 0.3937 0.7564 68.22 64.12 0.4608 0.9068 64.38 59.27
Table4: Impactofhistoricalinteractionlengthonprofilequality(usingQwen3(8B)).
tionyieldssubstantialperformanceimprovements jointoptimizationarecombined. Underthisfull
across all datasets. For example, on Yelp, MAE configuration, accuracy reaches 61.23% on Yelp,
isreducedfrom1.1235to0.7218andaccuracyin- 67.96%onAmazonMusic,and64.38%onAma-
creases from 23.17% to 55.48%, confirming that zon Books, with corresponding MAE values of
textualprofilesprovidesignificantlymoreinforma- 0.5126, 0.3937, and 0.4612, respectively. Com-
tiverepresentationsthanrawinteractionhistories. pared with the LettinGo-style configuration, this
setting yields consistent improvements across all
------ ---------------- --- ----- --- ------ --------- ------ -------------------------------------- --- ------------ ----------
Adding the cue&strategy layer on top of pro-
datasets. Overall,theablationresultsindicatethat
filegenerationleadstomodestbutconsistentgains.
whileprofilegenerationandjointoptimization
OnAmazonMusic,MAEfurtherdecreasesfrom
0.6597to0.5708,whileaccuracyslightlyimproves contributesubstantiallytoperformancegains,inte-
gratingcue&strategydiscoveryfurtherenhances
from58.67%to58.91%. Althoughthenumerical
------------------- --- --- -------------------- --- --- --- ------------- --- -------- --------- ------------
the effectiveness of joint user–item optimization
improvementsintroducedbystrategyalonearelim-
ited, these results suggest that strategy discovery byprovidingastructuredspaceforexplorationand
refinement.
primarilyreshapeshowpreferenceinformationis
abstractedandexpressed,ratherthandirectlyopti- Impactofhistoricalinteractionlengthonprofile
mizingpredictionaccuracyinisolation.
quality. Table 4 analyzes the impact of histori-
--- --- --- --- --- --- -------- --- ----- ---------- --- ------------------
Whenenablingjointoptimizationwithoutstrat- cal interaction length on profile quality. Across
thethreedatasets,varyingthenumberofhistorical
egy (i.e., the LettinGo (Wang et al., 2025)-style
---------- ------------ ----- --- ---------------- --- --- --- --- --- --- ---
configuration),performanceimprovesmorenotice- interactions leads to only moderate performance
ablyacrossdatasets. OnAmazonMusic,accuracy differences, indicating that our method does not
strongly depend on long histories. In particular,
--- --- --- --- --- --- -------- --- ------ ------- ---------- --------------
increasesto62.37%,comparedto58.67%withpro-
filegenerationalone. Inourimplementation,this usingamoderatehistorylength(e.g.,30–50inter-
settingcorrespondstoareproductionofLettinGo, actions)alreadyachievescompetitiveorbestper-
whereprofilegenerationandjointoptimizationare formanceonmostmetrics,whilefurtherincreasing
thehistorylengthprovideslimitedadditionalgains.
appliedwithoutthestrategylayer. Whiletheorig-
------------------------------- ------- --------- --- ------------- ---------- --- --- --- --- --- ---
inal method focuses primarily on user profiling,
OnYelpandAmazonBooks,extendingthehis-
weextendtheoptimizationtobothuseranditem
torylengthbeyondthisrangedoesnotconsistently
profilestoensureafaircomparison. improveaccuracyorF1scoreandmayslightlyde-
Thestrongestandmostconsistentperformance gradeperformance,suggestingthatexcessivehis-
is achieved when cue&strategy discovery and toricalinteractionscanintroducenoisyorlessrele-

vantsignals. Incontrast,AmazonMusicexhibits maintaining comparable coverage. Compared to relativelystableperformanceacrossdifferenthis- existing methods, which either rely on extractive torylengths,indicatingthatuserpreferencesinthis compression(e.g.,KAR(Xietal.,2024))orgener- domainarelesssensitivetohistorytruncation. atefree-formdescriptionswithweakergrounding Necessity of RL-based Optimization. We com- (e.g.,RLMRec(Renetal.,2024)andPALR(Yang pare the full model with a variant without RL etal.,2023)), DUET consistentlyattainsstronger (DUET W/O RL) to isolate the effect of RL. As alignment without sacrificing coverage. For in- showninTable5,removingRLleadstosubstantial stance,LG(Wangetal.,2025)achievesrelatively performancedegradationacrossalldatasets(e.g., highalignmentbutexhibitslessstablegrounding YelpAccuracydropsfrom61.23%to48.53%),indi- acrossdatasets,whileRLMRecattainshighercov- catingthatthegainscannotbeattributedtoprompt erageatthecostofweakersemanticalignment. In

designalone. contrast,DUETmaintainsbothhighalignmentand
Without RL, the generator reduces to a static mid-to-highcoverage,suggestingamoreeffective
mapping from interaction history to textual pro- balancebetweensemanticabstractionandevidence
files,lackingadaptiveselectionofrelevantsignals. preservation.
------------------------------------------------ --- --- --- --- ------------- --- --- --- --- ---
Incontrast,RLenablesoptimizingprofileconstruc-
4.5 CaseStudy
tionunderrewardfeedback,resultinginmoredis-
Figure4presentsarepresentativecasestudythat
criminative representations.These results demon-
----------- --------------------- --- ------- ------ --- --- --- --- --- ---
strate that RL-based optimization is essential for demonstrates how semantically aligned user and
DUET . itemprofiles enableaccurate prediction thattran-
---- --- --- --- --- ------------ -------------- --- ---------- --- ---------
scendsthelimitationsofsparserawinteractionhis-
4.4 SemanticAnalysisofGeneratedProfiles tories. In the user profile, initially scattered and
To better understand the source of performance fragmentedpreferencecuesaresystematicallydis-
gains, we analyze whether the generated profiles tilled into a stable and coherent preference struc-
exhibitmeaningfulsemanticpropertiesratherthan turefavoringfunk,soul,andprogressiverock(or-
servingasintermediatetextualartifacts. Weintro- ange), coupled with a pronounced emphasis on
duce two complementary metrics to characterize musicalcomplexityandhistoricalsignificance(pur-
semanticcompatibilityandgrounding. ple). Thecorrespondingitemprofileexhibitsstrik-
Semantic Alignment. We measure the ingsymmetry,characterizingthealbumasanexem-
embedding-levelsimilaritybetweengenerateduser plaryfunk-rockcomposition(orange)andposition-
anditemprofilesusingall-mpnet-base-v2from ingitasadefiningandculturallyinfluentialrelease
Sentence-Transformers (Reimers and Gurevych, of the 1970s (purple). This example shows 519
2019). Foreachuser–itempair,wecomputecosine that the learned profiles capture meaningful pref-
similarity: erence–attributecorrespondencethatisdifficultto
-------------------------------- -------------------------------- --- ------------ --- ----------------------------------------------- --------- ------- ---------- ---- -----------
e ·e recoverfromindividualreviewsalone.
u i
Align(u,i) = (3)
∥e ∥∥e ∥
u i 5 Conclusion
wheree ande denotetheembeddingvectorsof
u i In this paper, we propose DUET , a closed-loop
thegenerateduseranditemprofiles. Highervalues
framework for jointly generating user and item
indicatestrongersemanticcompatibilitybetween
textualprofilesforrecommendation. Unlikeprior
--- --- --- --- --- --------------------------------- --- --- --- --- -----------
modeleduserpreferencesanditemcharacteristics.
methods that rely on fixed templates or indepen-
-------- --------------- --- ---------- ------ ------- ----------- --------- --------------- --- --------------
Coverage (Faithfulness). We measure token-
dently constructed profiles, DUET treats profile
levelgroundingas:
generation as an exploration problem and aligns
--- --- --- --- --- ---------- ----- ----------- ------- --- ----------
Tokens(profile)∩Tokens(history) representations directly with downstream recom-
Cov =
Tokens(profile) mendationperformance.
--- --- ----------------- --- --- --------------------- --- ---- ---------- --------- ----
(4) Specifically, DUET integrates cue-based ini-
Thismetricquantifieshowmuchofthegenerated tialization, adaptive strategy construction, and
profileissupportedbyhistoricaltextualevidence. feedback-drivenjointoptimizationtoproduceflex-
We report coverage separately for user and item ible yet task-aligned user–item profiles. By opti-
profiles. mizing both profiles in a shared semantic space,
--------- --- --- --- --- ------ ------------- --- -------- -------- ------
AsshowninTable6,DUETachievesthehigh- theframeworkreducessemanticmismatchandcap-
est semantic alignment across all datasets while turesinteraction-relevantsignalsthataredifficultto

Setting Yelp AmazonMusic AmazonBooks MAE RMSE Acc F1 MAE RMSE Acc F1 MAE RMSE Acc F1 (%) (%) (%) (%) (%) (%) DUETw/oRL 0.8283 1.3893 48.53 41.15 0.7322 1.1430 57.18 52.48 0.8741 1.4760 51.83 50.35 DUET(full) 0.5126 0.9485 61.23 55.18 0.3937 0.7564 67.96 63.89 0.4612 0.9089 64.38 59.27 Table5: EffectofRL-basedoptimization(usingQwen3(8B)). User History: Andre' S Grindle "Tour of U.S.A.", Rating: 5.0. If your looking for heavy metals dim orgins look no further. Andre' S Grindle "Misfits", Rating:4.0. Actually the opening title track is more of a direct pop/rock type song. But the rock n roll returns in a big way on "Hay Fever". ............ Item History: Worlds Away, Rating: 4.0, Review: The CD is wonderful, and is a seminal piece of music for both the group and for those of us who were 'of age' in the '70s and '80s. Pablo Cruise was - and is - a group that makes beautiful music like few others, and this shipper/seller made it all the more special with a fast ship! THANKS!!! Worlds Away, Rating: 5.0, I love this CD! I'd recommend the Pablo Cruise Millenium Collection to get to know this band. Worlds Away to me represents the best of breezy '70s pop. Five stars! ............ USER PROFILE: Andre Grindle is a dedicated music enthusiast with a deep appreciation for funk, soul, and progressive rock, particularly drawn to artists who blend technical mastery with genre-defining innovation. His reviews consistently highlight albums that showcase musical complexity, lyrical depth, and historical significance, often referencing artists like Stevie Wonder, Prince, and Rush. He values authenticity and artistic vision, frequently praising albums that resist trend-chasing and prioritize creative integrity. His detailed, introspective reviews suggest a preference for nuanced analysis over superficial praise, with a focus on emotional resonance, production quality, and the artist's evolution. While he is generous with high ratings (often 5.0), he is also willing to critique perceived shortcomings, as seen in his 4.0 for "Test for Echo" and 3.0 for "The Color of Success." His engagement is characterized by a blend of personal anecdotes, technical appreciation, and historical context, indicating a preference for music that transcends mere entertainment. Item PROFILE: "Worlds Away" by Pablo Cruise is celebrated as a peak-era funk-rock album that exemplifies the band's ability to merge polished production with genre-blurring creativity. Users consistently praise its tight musicianship, genre-defying sound, and the band's ability to craft catchy, emotionally resonant tracks. The album's appeal lies in its seamless fusion of rock, funk, and pop, with standout tracks like "Love Will Find a Way" and "Worlds Away" receiving particular acclaim for their infectious melodies and lyrical depth. While some users note its dated production compared to modern standards, the majority highlight its historical significance as a defining work of the 1970s rock-funk movement. The album resonates most with fans of 1970s progressive rock, genre-defying artists, and listeners seeking well-crafted, emotionally engaging music. Its high average rating reflects widespread admiration for its artistic ambition and enduring appeal, though a minority acknowledges its limitations in terms of modern production quality. Figure4: Illustrationofthemutualcorrespondencebetweenuseranditem. Thehighlightedregionsdemonstrate thatuserpreferencessummarizedintheuserprofilealignwiththekeyattributesextractedintheitemprofile,which providescomplementaryinformationbeyondrawhistoriesandthusimprovespredictionaccuracy. Method Yelp AmazonMusic AmazonBooks Align UserCov. ItemCov. Align UserCov. ItemCov. Align UserCov. ItemCov. 10H 0.3902 /(1.00) /(1.00) 0.3577 /(1.00) /(1.00) 0.2604 /(1.00) /(1.00) KAR(Xietal.,2024) 0.4932 0.1745 0.1823 0.4807 0.2170 0.2391 0.5702 0.1877 0.1544 RLMRec(Renetal.,2024) 0.4010 0.2646 0.3773 0.3931 0.3526 0.4889 0.4436 0.2994 0.3506 PALR(Yangetal.,2023) 0.4715 0.3675 0.1917 0.4938 0.2197 0.2390 0.5216 0.2050 0.2267 LG(Wangetal.,2025) 0.5709 0.2378 0.2682 0.5109 0.2546 0.3749 0.5506 0.3883 0.3364 R4Rec(Fangetal.,2025) 0.4882 0.2348 0.2330 0.4208 0.3328 0.3595 0.4946 0.2831 0.2949 Ours 0.6382 0.2880 0.3429 0.5947 0.4002 0.4482 0.7287 0.3457 0.3127 Table6: Semanticalignmentandcoverageofgeneratedprofiles. Cov. denotesthefractionoftokensgroundedin historicaltext. recoverfromrawhistoriesorstaticpromptsalone. reinforcementlearning–basedoptimization. These resultssuggestthatadaptive,interaction-awaretex- Experiments on multiple real-world datasets tualprofilesprovideapromisingdirectionformore demonstratethatDUETconsistentlyoutperforms effective interpretable and performance-oriented strongbaselinesunderdifferentbackbonemodels, recommendationsystems. validating the effectiveness of joint profiling and

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-------------------------------------- --- --- --- --- --- ----------- --- --- --- --- ---

A ExperimentSetup FanYang,ZhengChen,ZiyanJiang,EunahCho,Xiao-

jiangHuang,andYanbinLu.2023. Palr:Personaliza-
tionawarellmsforrecommendation. arXivpreprint A.1 DataCuration
arXiv:2305.07622.
Jiarui Zhang. 2024. Guided profile generation im- Table7: Statisticaldetailsoftheevaluationdatasets.
proves personalization with llms. arXiv preprint
---------------------- ---------- -------------- ---------- ------ ----------- --- ------------ ------ ------
arXiv:2409.13093. Dataset #Train #Valid #Test #User #Item
Music 43,071 3,271 1,296 4,183 2,660
Book 71,972 6,144 5,541 13,863 13,515
Yelp 51,497 4,757 4,328 8,453 13,426
We conduct experiments on three widely used
real-worlddatasets:
• AmazonMusic(Music): Thisreferstothe“Dig-
--- --- --- --------------------- --- ------ ------ -------------------- --- ------
ital Music” subset of the well-known Amazon
Productdataset3,whichrecordsrichuserreviews,
ratings,andtextualinformationaboutitems,such
as titles, across a broad range of product cate-
--- --- --- ---------- ------ --- ----- ----- ---------- -----
gories,ontheAmazonplatform.2
• AmazonBook(Book): Thisreferstothe“Book”
--- --- --- ------------------- --- --- --------------------- --- --- ---
subsetoftheAmazonProductdataset.
dataset4,
• Yelp: This refers to the Yelp Open
--- --- --- ------- -------- -------------- -------- ------- ------------- ---------
which includes user reviews, ratings for busi-
nesses such as restaurants and retail shops, as
wellastextualinformationaboutthebusinesses.
Itiswidelyusedinrecommendationtasks(Qiu
etal.,2021).
WeusetheentireMusicdatasetforexperiments,
while for the Book and Yelp datasets, we utilize
--- --- --- ------------------------------- -------- --- -------- --------- ---------- -------
onlyasubsetduetotheirlargesize. FortheBook
dataset,weusedatafromthelasttwomonths,and
fortheYelpdataset,weusedatafromthelastsix
months. Foreachdataset,wesplititintotraining,
validation, and test sets based on the timestamps
--- --- --- ---------------- --- -------- ---------- ---- -------------- ---
of interactions, ensuring that test interactions oc-
curafteralltrainingandvalidationinteractionsto
preventinformationleakage(Jietal.,2023).
Regarding data filtering, following prior
--- --- --- --------- --- ----------- ---------- --------- -------- -----
work (Liu et al., 2019), we adopt a 5-core set-
tingtofilterthedataandexcludecold-startusers
and items—those not appearing in the training
--- --- --- --------------- --- ---------- --------- ---- ------ --------
set—from the validation and test sets. The sta-
tisticaldetailsoftheprocesseddatasetareprovided
inTable7.
3https://cseweb.ucsd.edu/~jmcauley/datasets/
amazon/links.html.
4https://business.yelp.com/data/resources/
open-dataset/.
A.1.1 ImplementationDetails RLMRecPrompt
Inourexperiments,weprimarilyemployQwen3- Role: Businessrecommendationassistant
Task: Determinebusinesstypesauserislikely
8B(Team,2025)andLLaMA38BInstruct (Dubey
------------------------------------------ --- ----- --- --- ------- ---------- ------------ --- --- ---
etal.,2024;Touvronetal.,2023)asboththerec- toenjoy
ommendation model and the profile generation InputFormat:
•Title: Businessname
model. Thetrainingprocessisimplementedusing
theTRL(vonWerraetal.). Keyhyperparameters, •Categories: Businesscategories
suchasbatchsizeandlearningrate,aredetermined •Sentiment: Usersentimenttowardbusiness
throughgridsearchtoachieveoptimalperformance.
OutputRequirements:
Moredetailscanbefoundinourcode.
  1. JSONformatonly
  2. Structure: A.2 BaselinePrompts {
    "summarization": "Types of businesses user
    KARPrompt
    likelyenjoys"(≤100words),
    Task: Analyzeuserpreferencesbasedonbusi-
    "reasoning": "Brief explanation for summa-
    --- --- --- --- --- --- --- ------------ ------------------ --- ----------
    nessreviewinghistory
    rization"(nowordlimit)
    Input: {user_history}-User’sbusinessreview-
    }
    inghistorywithsentimentsovertime
  3. NoadditionaltextoutsideJSON Instructions:
    1. Analyze the user’s preferences considering
    Input: INTERACTION ITEMS:
    businessnamesandcategories
    {user_history}
    2. Take into account sentiment patterns over
    --- ---- ------------ --- --------- -------- ---- --- --- --- ---
    time
    3. Provideclearexplanationsbasedonreview- LGPrompt
    --- -------------------------------------- --- --- --- --- --- -------- --- --- ---
    inghistorydetails
    Youwillserveasanassistanttohelpmegener-
    4. Consider other pertinent factors that may
    --- -------- ----- --------- --- ------- -------- --- --- --- ---
    ateauserprofilebasedonthisuser’ssentiments
    influencepreferences
    historytobetterunderstandthisusers’interest
    andthuspredicthis/hersentimentaboutatarget
    PALRPrompt item. Iwillprovideyouwithsomebehaviorhis-
    ---------- --- --- --- --- --- --- ----------------------------------------- --- --------------- ---
    toryoftheuserinthisformat: [itemattributes

Task: Summarizeuserpreferencesusingkey-

andsentiment]. Theuserprofileyougenerate
words.
shouldcontainasmuchusefulcontentaspossi-
Input: {user_history} - historical businesses
------ --- -------------- --- ------------ ---------- --- --- --- --- ---
bletohelppredicttheuser’ssentimenttowards
withusersentiments.
anewbusiness.
Output Format: An itemized list ranked by
------ --- ------- --- -------- ----------- --- --- --- --- ---
USERHISTORY:{user_history}.
importance.
PROFILEYOUGENERATE:
Template:
• KEY_WORD_1: "HIS-
--- ------------- --- --- --- --- ----- --- --- --- ---
R4RecPrompt(Reasoner)
TORY_BUSINESS_1", "HIS-
--- ----------------- --- --- --- --- ----- --- --- --- ---
UserReviewHistory
TORY_BUSINESS_2"
⟨H u organizedasbelow⟩
• KEY_WORD_2: "HIS- 1. TitleofItem1
------------- ---------------- --- --- --- --- ----- ---------------- ----------------------- ----------- ---
TORY_BUSINESS_3" PositiveAspects: [Aspect1],[Aspect2],...
NegativeAspects: [Aspect1],[Aspect2],...
Instructions: User Preference Elements: [Preference 1],
[Preference2],...
1. Extract key preference indicators from
--- ---------- --- ---------- --- ---------- ---- --- --- --- ---
2. TitleofItem2
userinteractionhistory.
PositiveAspects: [Aspect1],[Aspect2],...
--- --- --- --- --- --- --- ---------------- ----------------------- --- ---
2. Rankkeywordsbyimportance. NegativeAspects: [Aspect1],[Aspect2],...
User Preference Elements: [Preference 1],
--- --- --- --- --- --- --- --------------- --------- ----------- ---
[Preference2],... cantlyworsethanDUETacrossalldatasets. This
indicatesthatcoherentsummariesaloneareinsuf-
...
ficient, and that the gains of DUET arise from
--- --- --- --- --- --- --- -------- -------- --------- ------- --- ----------
ItemReviewHistorybyOtherUsers
⟨H organizedinthesameformatasabove⟩ learnedsemanticabstractionratherthanextractive
i
compression.
Task: Analyze whether the user will like the
--------- ------- ------- --- ---------- ----------- -------- --- --- --- --- --- ---
new Music i based on the user’s preferences
B.2 RankingunderHardNegativeSampling
andtheitem’sfeatures. Provideyourrationale
--------------------- --- --- --- -------------------- --- --- --- --- --- --- --- ---
Toconstructamorechallengingrankingscenario,
inoneconciseparagraph.
wereplacerandomnegativeswithhardnegatives
generatedbyacollaborativefilteringmodel. Specif-
--- --- --- --- --- --- --- ---------------------------------------- --- --- --- --- -------
A.3 ExampleofCue
ically,foreachuser,weretrievehigh-scoringitems
Thefollowingexamplesillustratehowrawsignals
from an EASE(Steck, 2019) model that the user
--------------------- --- --- ---------------- --- --- ---- ------- ----------- ----- ----- ---- --------
aredistilledintocues. Asshownonthetop, user
hasnotinteractedwith,andcombinethemwiththe
cuesemphasizehistoricalpreferences,whileitem
ground-truthitemtoformthecandidateset.
cues highlight metadata and user-group patterns. Table 9 reports the results. Compared to ran-
Together, they provide minimal but informative
--------- ---- ------- ------- --- --------------- --- --- --- --- --- --- ---
domsampling,performancedecreasesforallmeth-
hypothesesforprofileexploration.
ods due to increased difficulty, while DUET con-
--- --- --- --- --- --- --- --------- ------------ ----------- ---------------- ---- ------
sistently maintains the best performance across
ExamplesofUserCues
datasets. Thisindicatesthattheimprovementsare
------- ----- ------ ------ --- ------- -------- --------- ----------------------------------- --- --- --- ---
“enjoys retro puzzle games” derived from re-
robustandnotlimitedtotrivialrankingscenarios.
peatedengagementwithclassictitles.
“prefersconciseproductreviews”—inferredfrom B.3 RobustnessunderPreferenceDiversity
apatternofshort,directcomments.
WefurtheranalyzetherobustnessofDUETunder
“tendstogivehighratingsbutrarelycomments”—
varyinglevelsofuserpreferencediversity. Weuse
--- --- --- --- --- --- --- --------------------------------------- --- --- --- --- -----
highlightingconsistencybutlimitedfeedback.
thevarianceofhistoricalratingsasaproxyforpref-
erencestability: lowvarianceindicatesconsistent
--- --- --- --- --- --- --- ---------------- --- ------------------------------ --- --- ---
ExamplesofItemCues
preferences, while high variance corresponds to
--- --- --- --- --- --- --- ------------ ----- ---- -------- ----------- ---
“lightweighttrail-runningshoes”—derivedfrom
diverseorpotentiallyconflictingsignals.
productmetadata.
Wepartitionusersintothreegroupsbasedonper-
“popular among budget-conscious users” — in-
-------- ----- ---------------- --- --- ------ ----- --- --- --- --- --- ---
centilethresholds(bottom33%,middle33%,top
ferredfrompurchasepatterns.
33%ofratingvariance)andevaluateperformance
“stylized with retro aesthetics” — extracted from
--------- ---- ----- ----------- --- ----------- ---- --- --- --- --- --- ---
withineachgroup.
itemdescriptions.
As shown in Table 10, performance degrades
--- --- --- --- --- --- --- -------- --- --------- ----------- --- --------
smoothlyaspreferencediversityincreasesacross
all datasets. Importantly, the degradation is grad-
--- --- --- --- --- --- --- ------------- ------------ --- --------------- --- --------
B AdditionalExperiments
ualratherthancatastrophic,indicatingthatDUET
B.1 Non-LLMBaselineviaExtractive
remainsstableunderheterogeneousornoisyinter-
Summarization
actionhistories.
To examine whether the gains of DUET stem
---------- --- ------- --- ----- ------- ---- --- --- --- --- --- ---
C TheUseofLargeLanguageModels
from improved semantic representations rather
------------- --- ---------------- --- --------------- --------- ------ --- --- --- --- --- ---
than generic text generation, we introduce a non-
WeusedaLargeLanguageModel(LLM)onlyas
LLMbaselinebasedonextractivesummarization. a writing assistant to polish the language of the
Specifically, we apply TextRank (Mihalcea and
------------- --- -------- -------- --- --------- --- ---------- ------ ------- ----------- --- ---------
manuscript (e.g., grammar refinement, style ad-
Tarau,2004)toselectsalientsentencesfromuser
justment,andclarityimprovement). Theresearch
--- --- --- --- --- --- --- -------------------------------- --- --- --- ----------- ---
historiesandconstructuserprofileswithoutusing ideas,methodologydesign,experiments,andanal-
anygenerativemodel. ysiswereentirelyconceived,implemented,andval-
The extracted summaries are then fed into the
--- --------- --------- --- --- -------- -------- --- --- --- --- --- ---
idatedbytheauthorswithoutrelianceontheLLM.
samedownstreampredictorforratingestimation.
The LLM did not contribute to research ideation,
--- --- --- --- --- --- --- ------- ------- ---------- ----------- --- ---------
Thisbaselineisolatestheeffectofreadablesumma- experimentaldesign,orresultinterpretation.
rizationfromrepresentationlearning.
Table8showsthatTextRankimprovesoversim-
ple history truncation (10H), but remains signifi-
----------- ---------- --- ------ --- ------- -------- --- --- --- --- --- ---
Method Yelp AmazonMusic AmazonBooks
MAE RMSE Acc F1(%) MAE RMSE Acc F1(%) MAE RMSE Acc F1(%)
(%) (%) (%)
10H 0.8283 1.3893 48.53 41.15 0.7322 1.1430 57.18 52.48 0.8741 1.4760 51.83 50.35
TextRank 0.8104 1.1323 50.51 30.23 0.5914 0.8223 61.19 29.68 0.6328 0.8854 59.59 29.48
Ours 0.5126 0.9485 61.23 55.18 0.3937 0.7564 67.96 63.89 0.4612 0.9089 64.38 59.27
Table8: Comparisonwithanon-LLMextractivesummarizationbaseline(TextRank).
Method Yelp AmazonMusic AmazonBooks
------ --- --- ---- --- ----------- --- --- ----------- ---
NDCG@1 NDCG@5 NDCG@10 NDCG@1 NDCG@5 NDCG@10 NDCG@1 NDCG@5 NDCG@10
10H 0.1823 0.2815 0.4928 0.1875 0.3796 0.5153 0.1841 0.3146 0.4263
KAR(Xietal.,2024) 0.2156 0.3298 0.5412 0.3018 0.4896 0.6015 0.2965 0.4715 0.5834
RLMRec(Renetal.,2024) 0.2419 0.3472 0.5587 0.3371 0.5434 0.6162 0.2748 0.4526 0.5719
PALR(Yangetal.,2023) 0.2494 0.3563 0.5691 0.3395 0.5247 0.6115 0.2627 0.4634 0.5538
LG(Wangetal.,2025) 0.3187 0.4685 0.5814 0.4012 0.5674 0.6489 0.3795 0.5189 0.6284
R4Rec(Fangetal.,2025) 0.2575 0.3792 0.5526 0.2928 0.5912 0.6343 0.3013 0.4928 0.5959
Ours 0.3390 0.4873 0.6008 0.5123 0.6165 0.7025 0.4288 0.5638 0.6599
Table9: RankingperformanceunderEASE-based(Steck,2019)hardnegatives.
------------- ------- ----------------------------------------------------------- --- --- ----------- --- --- ----------- ---
VarianceGroup Yelp AmazonMusic AmazonBooks
#Samp. MAE RMSE Acc F1 #Samp. MAE RMSE Acc F1 #Samp. MAE RMSE Acc F1
(%) (%) (%) (%) (%) (%)
--- --- --- --- --- --- ------- --- --- -------
Stable 1530 0.4017 0.8664 71.76 68.96 432 0.2368 0.5990 82.56 86.89 1876 0.3171 0.8403 76.64 72.56
Moderate 1354 0.4773 0.8309 60.09 46.26 436 0.3921 0.6628 64.16 47.02 1827 0.4495 0.8059 66.73 55.45
Diverse 1444 0.6632 1.1198 51.13 45.95 428 0.5536 0.9607 57.10 59.27 1838 0.6199 1.0603 49.52 46.35
Table10: PerformanceofDUETunderdifferentlevelsofuserpreferencediversity(measuredbyratingvariance).
#Samp. denotesthenumberofsamplesineachgroup.