---
title: Apex (Fable 5)
description: For the hardest research and the most complex planning — Apex mode runs Niyra on Claude Opus 4 / Fable 5. BYOK-only, alpha-gated, per-conversation. Reach for it when reasoning quality matters more than speed.
url: /features/apex
lastUpdated: 2026-06-10
---

# Apex (Fable 5)


Apex is what you reach for when the task is genuinely hard. The model underneath is Claude Opus 4 / Fable 5 — Anthropic's top tier, costlier and slower than Sonnet, but with reasoning quality nothing else matches. Most of what you ask me for, Sonnet handles cleanly. Apex is for the rest.

## When to actually use Apex

- **Deep research** — synthesizing fifteen sources into a clean argument with the trade-offs called out. Sonnet writes it; Apex *holds* it.
- **Complex planning** — long horizon, many constraints, real trade-offs you'd otherwise need a Saturday to think through.
- **Subtle reasoning** — legal-adjacent work, financial analysis, contract redlines, edge cases where Sonnet sometimes misses nuance.
- **High-stakes drafting** — investor letters, board memos, strategic docs, the email you only get one shot at.

For daily email triage, scheduling, summaries, status pulls — Sonnet handles cleanly at a fraction of the cost. Apex is the wrong tool for those; you'll wait longer and pay more for an answer that wouldn't have been better anyway.

## How it works

Apex is enabled per conversation. From the chat surface, toggle "Apex mode" before sending the first message. Niyra routes that thread through Claude Opus 4 via your BYOK Anthropic key. Cost runs on your vendor account, not your Niyra credits.

There's no failover. Apex doesn't downgrade to Sonnet mid-conversation — that would silently change the quality of work already in flight. If you run out of vendor quota, the conversation pauses until you top up. I tell you when that happens, in plain English, before anything important breaks.

## BYOK requirement

Apex is **BYOK-only**. I don't include Opus pricing in credits because the math doesn't work for most users — you'd be paying for headroom you rarely use. Bringing your own key means:

- You see exact vendor charges in your Anthropic console.
- You can set your own monthly cap.
- You can pause Apex by removing the key without affecting the rest of Niyra.

See **[BYOK setup](/docs/byok-setup)** to plug your Anthropic key. Two minutes, one form, encrypted at rest.

## A real run

```
You:  (Apex on) Read these three CVC term sheets and tell me what
      the founder gives up most in each, in plain English.

Me:   Working through them. Quick read first, deep pass next.

      First pass — the headline:
        • Sheet A: 2× participating preference, 4-year vesting.
        • Sheet B: 1× non-participating, but board control flip
          at >$10M ARR loss.
        • Sheet C: 1× non-participating, full ratchet anti-dilution.

      Deep pass on what you actually lose:
        Sheet A is the worst on exit math. Participating
        preference means they get their 2× back AND their pro-rata
        share — at $20M exit, that's $4M off the top before the
        common pool even sees money.
        Sheet B looks fine until the board flip kicks in. If you
        miss the $10M trigger, you lose veto on hiring/firing the
        CEO. That's the live bullet here.
        Sheet C is cleanest on paper. Full ratchet bites only if
        you raise a down round — which, given your traction, is
        the lowest-probability scenario of the three.

      My ranking by what-you-lose-most: A > B > C.
      Want me to draft the redline counters for any of them?
```

That kind of read — actually holding the docs in mind, weighing the trade-offs, reasoning *about* the reasoning — is where Apex earns its cost.

## Alpha access

Apex is gated to early Alpha users today. We're learning what tasks people actually run on it before opening it broadly. The one-line use case is the filter: if you have a specific high-stakes job you want Opus on, you're in.

Email **hi@niyra.ai** with that one line.

## Pairs well with

- **[BYOK](/features/byok)** — required, not optional.
- **[Memory](/features/memory)** — Apex reasons better when it has your context; memory provides it.
- **[Research briefs use case](/use-cases/research-briefs)** — the canonical Apex workflow.