Two-Stage Recruitment Text Labeling via Lexicon-Guided Routing and Retrieval-Augmented Large Language Models

Recruitment texts are heterogeneous, and domain terminology evolves over time, making large-scale labeling difficult with limited manual annotation capacity. This protocol provides a reproducible two-stage workflow for classifying Chinese recruitment texts into Artificial Intelligence, Environmental Protection, or Other. Stage one performs lexicon-guided triage using two curated domain keyword lists. Postings that match only one domain lexicon are directly labeled. Postings that match neither lexicon are labeled as Other, while dual-match postings are routed to stage two. Stage two applies retrieval-augmented large language model inference. A knowledge base compiled from 12 authoritative domain documents is converted to text, split into about 1,000-character chunks with 20-character overlap, embedded using all-MiniLM-L6-v2, and indexed in LanceDB. For each uncertain posting, cosine-similarity k-nearest-neighbor retrieval returns candidate chunks filtered by a minimum similarity threshold (τ), and up to four chunks are injected into a fixed prompt template that defines label boundaries and constrains the output to a single label. A benchmark set of 3,000 postings is manually verified, with 1,000 postings per class, and achieves an inter-annotator agreement of 95.0 % and a Cohen's kappa (κ) of about 0.93. Evaluation compares multiple open-source large language models across a prompt-only setting and a retrieval-augmented setting using Qwen2.5-7B-Instruct. The retrieval-augmented configuration achieves 98.47 %accuracy and supports corpus-scale labeling of about 6.93 million postings for downstream descriptive aggregation.