llmx

Utilities for working with LLM outputs.

Currently this crate focuses on turning "fuzzy" JSON-like text (common in LLM responses) into real serde_json::Value.

Features

• Fuzzy JSON parsing: Handle markdown code fences, single-quoted strings, unquoted keys, Python literals (True/False/None), trailing commas
• Partial JSON parsing: Auto-complete incomplete JSON structures (useful for streaming)
• Streaming parser: Accumulate chunks and parse at any point

Rust Usage

use llmx::json::parse_fuzzy_json;

let v = parse_fuzzy_json("```json\n{'a': True, b: None}\n```").unwrap();
assert_eq!(v["a"], true);
assert!(v["b"].is_null());

Streaming JSON Parsing

use llmx::json::StreamingJsonParser;

let mut parser = StreamingJsonParser::new();

// Simulate streaming input
parser.push(r#"{"name":"#);
let v = parser.parse_partial().unwrap();
assert!(v.is_object());

parser.push(r#""Alice","age":30}"#);
let v = parser.parse_partial().unwrap();
assert_eq!(v["name"], "Alice");
assert_eq!(v["age"], 30);

TypeScript/JavaScript Usage (WebAssembly)

Install via npm:

npm install llmx

API

parseFuzzyJson(input: string): any

Parse fuzzy JSON-like text into a JavaScript value. Handles:

• Markdown code fences (```json ... ```)
• Single-quoted strings
• Unquoted object keys
• Python literals (True/False/None)
• Trailing commas

import { parseFuzzyJson } from "llmx";

const value = parseFuzzyJson("```json\n{'a': True, b: None}\n```");
console.log(value); // { a: true, b: null }

parsePartialJson(input: string): any

Parse partial/incomplete JSON, automatically completing unclosed structures. Useful for streaming LLM outputs.

import { parsePartialJson } from "llmx";

const value = parsePartialJson('{"name": "Alice", "age":');
console.log(value); // { name: "Alice", age: null }

parsePartialJsonWithStatus(input: string): { value: any; isComplete: boolean }

Parse partial JSON and return both the value and completion status.

import { parsePartialJsonWithStatus } from "llmx";

const result = parsePartialJsonWithStatus('{"name": "Alice"}');
console.log(result.value);      // { name: "Alice" }
console.log(result.isComplete); // true

const partial = parsePartialJsonWithStatus('{"name": "Ali');
console.log(partial.value);      // { name: "Ali" }
console.log(partial.isComplete); // false

StreamingJsonParser class

Streaming JSON parser for incremental LLM output parsing.

import { StreamingJsonParser } from "llmx";

const parser = new StreamingJsonParser();

// Simulate streaming input
parser.push('{"name":');
console.log(parser.parsePartial()); // { name: null }

parser.push('"Alice","age":30}');
console.log(parser.parsePartial()); // { name: "Alice", age: 30 }

// Check completion status
const { value, isComplete } = parser.parsePartialWithStatus();
console.log(isComplete); // true

// Access buffer contents
console.log(parser.buffer()); // '{"name":"Alice","age":30}'

// Clear for reuse
parser.clear();

Methods

| Method | Description | |--------|-------------| | new StreamingJsonParser() | Create a new parser instance | | push(chunk: string) | Append a chunk of data to the buffer | | buffer(): string | Get the current buffer contents | | clear() | Clear the parser buffer | | parsePartial(): any | Parse buffer with auto-completion | | parsePartialWithStatus(): { value: any; isComplete: boolean } | Parse with completion status | | parseComplete(): any | Parse as complete JSON (no auto-completion, throws if incomplete) |