Model evaluation reveals where models fail, but rarely why or whether a proposed fix genuinely works. We introduce EvalRx, an open-source agentic framework for statistically grounded model diagnosis and repair. EvalRx discovers systematic failure modes, explores candidate mechanisms, formulates falsifiable hypotheses, and verifies them by executing frozen, pre-specified tests before using supported diagnoses to guide tiered repair. Candidate repairs are validated against the unchanged model and promoted only when they improve the target behavior without unacceptable regression. Across language, vision-language, and audio-language settings spanning Gemini, Qwen, Gemma, and Nemotron, EvalRx improves performance in all 12 evaluated model family-modality combinations, with gains ranging from +1.4 to +10.9 percentage points (+5.8 points on average). These results show that model evaluation can serve not only to measure failures, but to support an auditable process for diagnosing and repairing them.
Figures & tables
Figure 1: Verification-gated model evolution. A candidate repair is promoted to the next model version only after its improvement is confirmed on held-out data. Otherwise, the current model remains unchanged and the diagnosis-repair cycle continues.
System family & examples
Starts with
What it delivers
What remains external
Auditing & slice discovery EvalTree, ErrorMap
Evaluation failures
Failure patterns or error slices
Held-out validation, repair, and post-repair audit
Propose-and-verify D3, VibeCheck, HypoGeniC
Candidate hypotheses
Tested hypotheses
Repair and version-level audit
Prompting, editing & retraining ProTeGi, TextGrad, GEPA; Claude Code ∗
A supplied target, reward, or task
Candidate repair
Failure diagnosis and a common verification rule
EvalRx
Labeled evaluation set
Verified repair, or an explicit inconclusive result
Nothing: re-audits the promoted version and recurses
Table 1: Where existing approaches stop, and where EvalRx continues. EvalRx connects failure discovery, statistical hypothesis testing, repair selection, and version re-audit in one evidence-gated loop. Examples are representative, not exhaustive.
Figure 2: Overview of EvalRx . EvalRx organizes model diagnosis and repair into five stages: M1 (Probe) discovers failures and gathers diagnostic evidence. M2 (Explore) analyzes failure structure and identifies candidate explanatory signals. M3 (Diagnose) formulates and freezes falsifiable hypotheses. M4 (Verify) tests these hypotheses with statistical evidence, and M5 (Repair) uses supported mechanisms to guide targeted repairs and verifies their improvement against the unchanged model.
Figure 3: M1 turns raw model outcomes into an auditable diagnostic signal table. A normalized case packet is routed to compatible analyzer families, assembled into a typed per-case signal matrix, and audited for coverage and missingness before M2.
Access and modality
Per-case diagnostic signals
Black-box, all modalities
Calibration, consistency under prompt or input contrasts, uncertainty, termination, response-format violations, and counterfactual outcome changes.
White-box language models
Token entropy, logits, attention, representation similarity, and logit-lens-style readouts.
Vision-language and audio-language models
Grounding, hallucination, attention or attribution over non-text tokens, modality ablations, local masking, and temporal or spatial perturbations.
Table 2: M1 selects analyzers that match the target model and task protocol. These representative analyzer families differ in availability across modalities and model interfaces.
Figure 4: M2-M3 turns observed failure structure into a falsifiable, frozen test contract. M2 records descriptive candidates; M3 challenges competing explanations and freezes the prediction, control, threshold, falsifier, and test design before M4 using them.
Figure 5: M4 admits a mechanism claim through statistical adjudication. Frozen test specifications and case identifiers enter a locked runner; statistical and protocol-consistency gates jointly route each hypothesis to supported, refuted, or inconclusive.
Tier
Evolution path
Space
Candidate treatment
L1
Non-parametric
Input
Prompt rewrites, explicit constraints, output formats, and evidence-use instructions.
L2
Non-parametric
Scaffold
Deterministic multi-call workflows, preprocessing, external tools, conditional execution, and output aggregation around the unchanged model.
L3
Non-parametric
Internals
Read-only logits or attention, or audited inference-time interventions such as attention reweighting or activation steering, without persistent weight updates.
L4
Parametric
Parameters
Dataset construction and fine-tuning or adapter updates. These create a new checkpoint and require explicit human execution or approval.
Table 3: The repair ladder makes intervention cost and parameter change explicit. L1-L3 are non-parametric evolution because the checkpoint weights remain frozen; L4 is parametric evolution. The tier constrains the intervention space, not repair quality.
Figure 6: M5 promotes only repairs that beat the unchanged baseline under a paired test. A supported hypothesis first receives a causal probe; repair search then starts at the least invasive permitted tier, freezes a candidate and its success rule, and compares it with the unchanged baseline on matched cases. The decision is to ship, stop, try the next tier, or return filtered data to M1.
Algorithm 1: A guarded iterative version loop. A version can seed the next cycle only after frozen-contract diagnosis, held-out paired repair evaluation, and the approved intervention ceiling all pass.
Table 4: A three-modality evaluation roster. The table lists the models in benchmark and the role of each LLM, VLM, and ALM track in evaluating EvalRx .
Figure 7: Verified repairs across the LLM benchmark track. Each panel compares baseline and post-repair performance; labels report the panel-specific change in percentage points.
Figure 8: Verified repairs across the VLM benchmark track. The figure compares baseline and post-repair performance using Claude Opus-5 as the base agent.
Figure 9: Verified repairs across the ALM benchmark track. The figure compares baseline and post-repair performance using Claude Opus-5 as the base agent.
Figure 10: LLM repair outcomes with a second agent backbone. The figure compares baseline and post-repair performance using Antigravity Gemini-3.1-Pro as the base agent.
Model
BBH (word sorting)
gsm8k
MMAU
AudioCaps-Hallucination
ChartQA
Spatial457
Gemma-4-E2B
56.5%Δ+3.2%
87.6%Δ+2.0%
36.3%Δ+20.3%
56.6%Δ+0.0%
48.4%Δ+21.9%
18.4%Δ+0.0%
Gemma-4-E4B
62.0%Δ+21.6%
91.4%Δ+0.0%
65.3%Δ+12.0%
61.7%Δ+16.7%
58.3%Δ+26.0%
16.7%Δ+22.7%
Gemma-4-12B
82.4%Δ+11.2%
93.4%Δ+1.2%
63.0%Δ+16.7%
54.0%Δ+18.7%
73.7%Δ+17.3%
16.3%Δ+19.3%
Table 5: Repair gains across the Gemma-4 scale range. The table reports baseline accuracy and post-repair improvement for each Gemma-4 model-task setting.
Figure 11: A complete, mechanism-verified repair loop on ChartQA. For Gemma-4-E2B, the L2 scaffold is promoted only after its hypotheses are supported under frozen tests and its paired outcome improves from 49.2% to 79.7% .
Figure 12: A mechanism-verified L1 repair on BBH (word sorting). For Nemotron-3-Nano-4B-FP8, the supported strict-copy intervention improves held-out accuracy from 12.0% to 25.6% .
Figure 13: An empirical repair that remains mechanistically unresolved on MMAU. For Gemma-4-E2B, the L2 scaffold improves held-out accuracy from 43.0% to 60.2% , but no mechanism reaches the supported verdict; the result is therefore not presented as a confirmed mechanism repair.
Multilingual and multicultural benchmarks now cover dozens of languages and model families, but the resulting score landscapes remain metric-rich and insight-poor, necessitating fine-grained multilingual post-evaluation diagnosis. However, single LLMs and open-ended agents are easily swamped by the long, noisy diagnostic input, and no reusable taxonomy exists for it. To address this, we propose MADE, a Multilingual Agentic Diagnosing Engine that decomposes post-evaluation analysis into planning, aggregate analysis, instance-level case inspection, multilingual and cultural reflection, and grounded report synthesis. MADE is paired with an expert-led 54-query and 15-language diagnostic set, evaluated on top of a large-scale multilingual evaluation substrate (33 model families, 11 benchmarks, 26 languages, 34 cultures, 8.66M evaluation records). Experiments show that MADE outperforms the strongest shared baseline by 47% in diagnosis report quality and is preferred by human multilingual experts in 87.9% of pairwise comparisons. Applied with multilingual experts, MADE further surfaces four actionable findings on deployment, iteration, and cross-cultural pitfalls, turning benchmark score tables into model-selection and remediation guidance.
Building an omni-modal foundation model means evaluating it across text, image, video, and audio. Excellent evaluation toolkits exist for each modality, but their inference engines, prompt conventions, and metric implementations are mutually incompatible, so practitioners end up maintaining separate environments for every toolchain and still struggle to compare results across them. OmniEvaluator grew out of this need in our own model development: rather than reimplementing benchmarks, it connects existing inference engines and curated evaluation libraries at a higher level, exposing four inference backends, four evaluation frameworks, and over a thousand benchmarks through a single interface. Every run is recorded as an artifact capturing the full configuration for exact reproduction, and results flow into a shared dashboard for cross-model comparison. A federated mode shares GPU inference servers across concurrent evaluations, and a built-in verifier, small enough to run on CPU, keeps its score stable across engines and prompts where rule-based scoring fluctuates under configuration mismatch, matching cost-efficient commercial LLM judges without their recurring API cost. The system, demo video, and dashboard are publicly available. (https://github.com/naver-ai/omni-evaluator)
An unsuccessful LLM agent rollout contains more information than its final reward: the observations available to the agent, the actions it chose, and the environment's responses. Reusing this experience for learning requires identifying a decision to revise and testing a concrete alternative. We introduce the Agent Error Dataset (AED), comprising 50,228 error-diagnosis pairs from 9,961 source tasks across 33 environments, 19 harness families, and 23 policy models in text-based agent systems. We retain source traces and execution metadata to support cross-setting failure analysis and re-diagnosis without repeating the original rollout. Our five-stage Agentic Error-to-Training (AET) pipeline collects natural failures, generates diagnoses and proposed corrections, and checks them against recorded evidence. Where replay is supported, we compare corrections with original-action retries from the same checkpoint under matched execution settings. We then construct separate training views for diagnosis and actor recovery. Across 3,062 matched replay pairs, first-proposal corrections raise verifier pass rates from 18.4% to 51.1%, a gain of 32.7 percentage points. Using a separately frozen diagnosis release, full-diagnosis fine-tuning on 1,656 source tasks raises Qwen3-8B's exact-step agreement with internal teacher labels from 47.2% to 63.6%, averaged over three seeds on a 943-case holdout. The strongest prompted reference in this comparison scores 54.7%, and mean agreement improves at each of four increasing training-set sizes. In a single-seed comparison of actor-training recipes, action-only repair training scores 6.67 percentage points higher on WebShop-lite than success-only training.