Why is Fable 5 slow to start responding in Cursor?

Fable 5 is tuned for deep reasoning; first-token latency can reach about 80 seconds. That's normal. For quick Q&A, switch to Opus 4.8 or Sonnet 4.6 — same endpoint, different model name.

Is pointing an IDE at a third-party endpoint safe?

Your code and conversations transit the configured endpoint. Vet providers for real-model verification and transparent billing; evaluate carefully for sensitive repos and clear company projects with compliance.

IDE integration guide · updated 2026-06-10

Use Fable 5 in Cursor

Q: How do I debug a 401 or 404 after setup?

401: the key is incomplete or in the wrong field. 404: protocol/URL mismatch — OpenAI-compatible tools need the /v1 URL, Anthropic-protocol tools the bare host. Verify the key with cURL first.

Cursor, Cline, Continue — any tool with a custom model endpoint can run claude-fable-5. It's always the same three things: Base URL + API key + model name. Here's exactly what to enter in each tool.

One endpoint, every tool

OmniaKey exposes both protocols (docs):

Protocol	Base URL	Tools
Anthropic protocol	`https://api.omniakey.com`	Claude Code, Cline, official SDKs
OpenAI-compatible	`https://api.omniakey.com/v1`	Cursor and anything labeled "OpenAI Compatible"

Model name is always claude-fable-5; get a key at omniakey.com (no card required, USDT or card top-up, Fable 5 at $3/$15 limited-time). Going direct to Anthropic's official API instead? Swap in the official base URL — the steps below are identical.

Cursor: three steps

Open Cursor Settings → Models, click Add model, and name it claude-fable-5.
Paste your key into the OpenAI API Key field, enable Override OpenAI Base URL, and enter https://api.omniakey.com/v1.
Hit Verify, then pick claude-fable-5 in the Chat / Composer model selector.

⚠️ Two gotchas

① Tab autocomplete doesn't use your endpoint. Cursor's built-in features like Tab completion run on Cursor's own infrastructure — the custom model only powers Chat / Composer / Agent conversations.
② The UI moves between versions. Setting names and locations change (some versions want unused built-in models disabled before adding custom ones) — follow whatever your version shows.

Cline / Roo Code (VS Code extensions)

In the extension settings, set API Provider to Anthropic with custom Base URL https://api.omniakey.com and model claude-fable-5 — or choose OpenAI Compatible with https://api.omniakey.com/v1. Long agent runs are exactly where Fable 5 shines; verify on small steps before enabling auto-approve.

Continue.dev

# ~/.continue/config.yaml
models:
  - name: Fable 5
    provider: anthropic
    model: claude-fable-5
    apiBase: https://api.omniakey.com
    apiKey: YOUR_API_KEY

Claude Code

Officially supports the ANTHROPIC_BASE_URL environment variable — two lines and done. Full walkthrough (including what changes after June 23) on our sister site: fableclaude.com.

Windsurf & everything else

Same pattern everywhere: find the "custom model / OpenAI Compatible / BYOK" entry and fill in the three things (Base URL, API key, model claude-fable-5). Entry names shift between tools and versions — anchor on the trio and you won't get lost. If a tool doesn't support custom endpoints, fall back to Claude Code or the raw API.

One key for every IDE

OmniaKey · Fable 5 at $3/$15 limited-time (~70% off) · same key runs GPT-5.5 / Gemini 3.1 · USDT or card · no card to sign up

Get an API key →

FAQ

Can I pick Fable 5 directly in Cursor?

Cursor's built-in model list updates on its own schedule. If it's not there yet — or you want a cheaper endpoint (OmniaKey's limited-time $3/$15 is ~70% off official) — add claude-fable-5 as a custom model using the steps above.

Why does Fable 5 take forever to start responding in Cursor?

Fable 5 is tuned for deep reasoning; first-token latency can reach ~80 seconds. That's normal, not a config error. Use it for big think-first tasks; for quick Q&A, switch to Opus 4.8 / Sonnet 4.6 (same endpoint and key, different model name).

Is this safe?

Your code and conversations transit whatever endpoint you configure. Vet providers (verify the real model, transparent billing), think twice for sensitive repos, and clear company projects with compliance first.

How do I debug a 401 / 404?

401: check the key was pasted in full and into the right field. 404: usually a protocol/URL mismatch — OpenAI-compatible tools need the /v1 URL, Anthropic-protocol tools the bare host. Still stuck? Verify the key from the command line with the cURL example.