Drex — The High-Context Decision Engine
Drex (by Nace AI) is the alternative decision engine for browser automation — the same role as Jev (fast micro-decisions per browser action, one Choice call per step), from a different provider, with one big advantage: roughly ~4× the context window per decision.
Why Drex exists
Jev's speed comes from a compact element table — only so many characters of the page's accessibility tree are sent per step. On simple pages that's plenty. On dense pages (dashboards, data tables, intricate multi-section forms), the compact view can crop out the very element the task needs, and the engine starts guessing or stalling.
Drex is wire-compatible with Jev (same API shape — it's a drop-in replacement in AgentX's settings), but it accepts a much larger element table per step. Same fast loop, far fewer "I can't see it" moments.
Jev vs Drex — detailed
| Jev | Drex | |
|---|---|---|
| Role | Fast browser micro-decisions | Fast browser micro-decisions |
| API | Jev Choice API | Wire-compatible with Jev |
| Context per step | Compact element table | ~4× larger element table |
| Access | Bring your own key/endpoint | Invite-based |
| Key rotation | Multiple keys, one per line | Multiple keys, one per line |
| Fallback | Main model on failure | Main model on failure |
| Best for | Everyday speed | Complex, dense pages |
Rule of thumb: start with Jev. Switch to Drex when you notice the engine missing elements on complicated pages, or when tasks on dashboards and web apps keep stalling.
Get access
Drex is invite-based. Use this invite link:
https://drex.nace.ai/invite/kc6cz8pu
Sign up through the invite, then create an API key in the Drex dashboard. Check Drex's own site for current pricing and tiers.
Setup in AgentX
- In AgentX, open Settings → Jev (the decision-engine settings page — Drex is selected there, not in the providers list).
- Select Drex as the engine.
- Paste your Drex base URL and model name.
- Paste your API key — multiple keys, one per line, are supported and the agent rotates them automatically.
- Run a browser task and watch the decision speed in the watch panel.
Fallback behavior
Identical to Jev: the main model steps in only when Drex is unavailable or a decision call errors. The switch is automatic and the task continues.
What's next
- Jev — the default fast engine
- Browser Automation Options — backends vs engines, what to pick
- Browser Setup — the browser the engine drives