Incremental JSON parser for streaming LLM tool calls in Ruby
Built this for streaming AI tool calls. LLMs stream function arguments as JSON character-by-character. Most parsers reparse from scratch each time - O(n²) behavior that causes UI lag. This maintains parsing state, processing only new characters. True O(n) performance that stays imperceptible throughout the entire response. Ruby gem, MIT licensed. Would love feedback.
Incremental JSON parser for streaming LLM tool calls in Ruby launched on October 22, 2025 with 13 votes, #768 of 8,178 launches that month and more than 75% of that year's launches.
In plain words
This Ruby gem parses JSON incrementally as it arrives character-by-character from streaming language models, avoiding the performance bottleneck of reparsing entire documents. Instead of O(n²) complexity that causes UI lag, it maintains parsing state and processes only new characters for true O(n) performance. Built specifically for AI tool calls, it keeps interfaces responsive throughout long responses. The library is open-source under the MIT license.
written from the facts on this page · September 2026
From the sources
Modern LLM providers can stream their responses. This is great for user experience — instead of a loading spinner, users see the response being generated in real time. They can also call external functions (also called "tools"): search your database
Aha! Develop is the agile tool that links strategy to delivery . Modern LLM providers can stream their responses. This is great for user experience — instead of a loading spinner, users see the response being generated in real time. They can also call external functions (also called "tools"): search your database, run calculations, send emails, whatever you give them. When the AI decides to use a tool, it returns the function arguments as JSON. For example, {"query": "sales reports Q4"} . Except there's a catch. The tool arguments come through as JSON. And when you're streaming JSON character by character, most of those characters form ... incomplete JSON: {"user {"user": {"user":"ali…from aha.io
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