Claude Fable 5 vs Grok 4
Grok 4 is cheaper for every workload modelled here.
List prices checked
Specifications and rates
| Property | Claude Fable 5 | Grok 4 |
|---|---|---|
| Input per 1M | $10.00 | $3.00 |
| Output per 1M | $50.00 | $15.00 |
| Cached input per 1M | $1.00 | $0.750 |
| Blended (3:1) | $20.00 | $6.00 |
| Context window | 200K | 256K |
| Max output | 64K | 64K |
| Inputs accepted | text, image | text, image |
Source: Anthropic pricing (August 2026) · xAI pricing (May 2026). Published list prices only — committed-use discounts, regional variation, and per-request charges are not included. Not yet independently re-checked against the vendor’s page.
Monthly cost by workload
Identical token volumes through both rate cards. Output-heavy profiles are where the ranking flips.
| Workload | Claude Fable 5 | Grok 4 | Cheaper |
|---|---|---|---|
| In-app chat assistantA support or help assistant handling a few thousand conversations a month, with short prompts and short answers. | $450 | $135 | Grok 4saves $315/mo (70%) |
| RAG over documentsRetrieval-augmented answering where each request stuffs several retrieved passages into the prompt, so input dominates. | $3,750 | $1,125 | Grok 4saves $2,625/mo (70%) |
| Coding agentAn agentic loop that reads files and writes patches, generating heavy output and re-sending large context on every turn. | $9,000 | $2,700 | Grok 4saves $6,300/mo (70%) |
What each one is for
Claude Fable 5
by Anthropic
Anthropic's top model for long-running agentic work, priced at twice Opus 5. Worth it only where a longer autonomous run genuinely replaces human supervision, since the token cost compounds across a multi-hour session.
Grok 4
by xAI
xAI's flagship, priced to match Claude Sonnet exactly, with a large context window and live access to posts on X as a differentiator.
Common questions
- Is Claude Fable 5 or Grok 4 cheaper in 2026?
- Grok 4, for every workload modelled here. On a blended 3:1 basis it costs $6.00 per million tokens against Claude Fable 5's $20.00.
- Which has the larger context window?
- Grok 4, at 256K tokens against 200K. A larger window only helps if you can afford to fill it — the cost of one full-context request is in the table above.
- Which is cheaper for output-heavy work like agents?
- Grok 4, at $15.00 per million output tokens against $50.00. Reasoning tokens bill as output, so for agentic loops this axis usually decides the invoice regardless of what the input rates look like.
- What is not included in these figures?
- Batch-processing discounts, fine-tuning, long-context surcharges above a provider's standard tier, and any enterprise agreement. These are published pay-as-you-go list prices, checked against each provider's own pricing page on the date shown.
- Is switching from Claude Fable 5 to Grok 4 worth it?
- On price alone it is about 70% cheaper on a blended basis. Whether that survives contact with your workload depends on output quality and on retry rate — a cheaper model that needs two attempts is not cheaper. Model the specific volumes in the calculator before you migrate.