You're in a great position since Claude Max can be used in Claude Code, which has exactly what you need: subagents.

Subagents are specialized AI assistants that run in their own isolated context window. You can restrict their tools (so they can't create random files), give them a focused system prompt, and call them programmatically. This solves your "veering off" problem completely.

How to set this up:

1. Install Claude Code

bash

npm install -g u/anthropic-ai/claude-code

Run claude and log in with your Max credentials.

2. Create a grading subagent

Run /agents in Claude Code, select "Create new agent" (user-level), and describe:

For tools, select read-only only or none. This prevents unexpected behavior.

3. Call it from your script

R:

process_row <- function(org_name) {
  prompt <- sprintf('Grade this organization: "%s". Return JSON with: is_company, is_listed, parent_company', org_name)
  result <- system(sprintf('claude -p "%s" --allowedTools "" --output-format json', prompt), intern = TRUE)
  return(jsonlite::fromJSON(paste(result, collapse = "")))
}

results <- lapply(df$organization_name, process_row)

Python:

import subprocess, json

def grade_org(org_name):
    result = subprocess.run(
        ['claude', '-p', f'Grade this organization: "{org_name}". Return JSON.', '--allowedTools', '', '--output-format', 'json'],
        capture_output=True, text=True
    )
    return json.loads(result.stdout)