API integrations + automation (Technical). Connect Shopify with Klaviyo, warehouse/ERP, and shipping systems. Requirements: API reading + code generation. Best pick: GPT-5.3 Codex - Best at reading API docs and generating integration code. Alternative: Grok Code Fast 1 - Fast coding model for integration work. Budget pick: GPT-5.3 Codex-Spark - Quick prototyping for simple integrations. Recommended models: GPT-5.2 Thinking, GPT-5.3 Codex, GPT-5.3 Codex-Spark, Gemini 3 Pro, Claude Opus 4.6, Claude Sonnet 4.5, Grok Code Fast 1. Use with caution: GPT-5.2 Instant, Gemini 3 Flash, Claude Haiku 4.5, Grok 4.1 Fast (Non-reasoning), Llama 4 Maverick (Instruct), Llama 4 Scout (Instruct). Roles: Engineering. Stacks: Shopify, Klaviyo.