Show HN: AI Subroutines – Run automation scripts inside your browser tab
Zero token cost. That's what rtrvr.ai just shipped — browser automation that records once, runs infinite times without hitting an LLM.
Why it matters
Browser automation agents have stalled because they waste tokens on repetitive tasks. This startup flips the model: record deterministic scripts once, let agents call them as zero-cost tools. It's a architectural insight that could reshape how enterprises think about AI agent workflows.
The key facts
7 to knowRecords browser tasks as callable subroutines with zero token cost and zero LLM inference delay
Script execution happens in-browser tab context (not proxy/headless worker), preserving auth/CSRF/TLS automatically
Network request trimming: ~300 requests down to ~5 based on method, timing, origin
Combines network calls with DOM actions (click, type, find) in single function
Use cases: bulk DM sending, product catalog scraping, EHR form filing, CRM syncing via MCP servers
Key insight: repetitive task automation shouldn't require inference loop — record once, execute deterministically
Published: April 17, 2026 (Show HN launch)
Go to the source
Hacker Newsrtrvr.ai
Publisher excerpt: We built AI Subroutines in rtrvr.ai. Record a browser task once, save it as a callable tool, replay it at: zero token cost, zero LLM inference delay, and zero mistakes. The subroutine itself is a deterministic script composed of discovered network calls hitting the site's backend as well as page…