We fine-tuned a claims determination model over 8 weeks.
Training data preparation (weeks 1-3): we compiled a training corpus from four sources: historical claims decisions (15,000 claims with documented coverage determinations — claim description, relevant policy section, assessor determination, and reasoning notes; de-identified to remove customer personal information while preserving claim characteristics and policy provisions), policy wording corpus (all 28 product variants — comprehensive, standard, and basic home and contents policies across different underwriting years — parsed into structured sections for coverage, exclusions, conditions, and definitions), Australian insurance law reference (Insurance Contracts Act 1984 provisions, relevant ASIC regulatory guidance, key Australian case law on home insurance coverage disputes — particularly landmark decisions on flood/storm distinction, gradual deterioration, maintenance exclusions, and wear-and-tear versus sudden damage), and internal guidelines (the insurer's claims handling manual, coverage determination guidelines, and assessor training materials — the institutional knowledge that experienced assessors used but that was not available to the generic model).
Data formatting: each training example was structured as — instruction (determine coverage for this claim), input (claim description and relevant policy extracts), output (coverage determination with step-by-step reasoning citing specific policy clauses). We created 12,000 training examples and 3,000 validation examples, covering: covered claims (45% — with reasoning explaining which policy provision responds), denied claims (35% — with reasoning identifying the specific exclusion or condition not met), and partially covered claims (20% — with reasoning identifying covered and uncovered components, applicable sub-limits, and excess calculations). Fine-tuning execution (weeks 3-5): base model: Llama 3.1 70B — selected for its strong reasoning capability and open-source licence permitting commercial use. Fine-tuning method: QLoRA with 4-bit quantisation — enabling training on 2x A100 GPUs (80GB each). Training configuration: learning rate 2e-4, batch size 4, gradient accumulation 8, 3 epochs over the 12,000 training examples, with validation loss monitoring every 100 steps.
Training time: 14 hours. Total compute cost: approximately A$450. The resulting adapter was 156MB — loaded on top of the 35GB quantised base model. Evaluation and iteration (weeks 4-7): we evaluated the fine-tuned model against three benchmarks. Accuracy benchmark: 3,000 held-out claims (not used in training) — the model's coverage determination compared against the consensus determination of three senior assessors. Results: first iteration: 86.3% accuracy (up from 71% for the generic model). Error analysis revealed: the model struggled with claims involving multiple concurrent causes (storm damage to a roof that also had pre-existing maintenance issues), claims where coverage depended on the temporal sequence of events (water damage: was the pipe burst sudden or gradual?), and claims involving policy definitions of specific terms (what constitutes "storm" under the policy — wind speed thresholds, Bureau of Meteorology definitions). We added 2,000 additional training examples focused on these challenging categories. Second iteration: 91.
7% accuracy — meeting the 90% target. The remaining 8.3% errors were predominantly in genuinely ambiguous cases where the senior assessor panel themselves had split decisions. Reasoning quality: domain experts reviewed 500 model-generated reasoning explanations. Assessment: 94% of reasoning explanations correctly cited relevant policy clauses, 91% applied Australian insurance principles correctly (no US law references, no incorrect terminology), 88% identified the correct exclusion or condition when denying a claim, and 96% used appropriate professional language suitable for customer communication. Adversarial benchmark: 200 deliberately challenging examples — edge cases, unusual claim scenarios, policy provision conflicts. The model correctly identified these as requiring senior review in 83% of cases (flagging uncertainty rather than making a confident incorrect determination — the desired behaviour for edge cases). Deployment architecture (weeks 6-8): the fine-tuned model was deployed on-premise within the insurer's private cloud (AWS ap-southeast-2 — Sydney region, within Australian data sovereignty requirements).
Inference infrastructure: 2x NVIDIA A10G GPUs for model serving, using vLLM for efficient inference with continuous batching. Average inference time: 4.2 seconds per claim determination (compared to 35 minutes for human assessment of straightforward cases). Integration: the model was integrated into the Guidewire ClaimCenter workflow as a decision-support tool — when a claim reaches the coverage determination stage, the model automatically generates a recommended determination with reasoning. The assessor reviews the AI recommendation, approves or modifies it, and records their decision. The assessor's decision (whether they agreed or disagreed with the AI) feeds back into a continuous evaluation dataset for ongoing model monitoring.