A thread on r/TechSEO is titled “Fable 5 is better than any SEO tool in the world.” It is one of the first results Google shows when you search for Claude Fable and SEO.
It is half right. Fable is a better SEO analyst than any tool. It still cannot tell you how many people search for anything.
The other half arrived on September 22, 2026. Three weeks after shipping Fable 5.1, Anthropic released Claude Opus 5.5 and said it “performs at the level of Claude Fable 5.1 on most work.” Anthropic’s own model guide now tells developers to start with Opus 5.5 for most workloads. So if you searched for Fable, the honest answer for SEO is that you probably want Opus 5.5, and Fable for the rare job that runs for hours.
Neither model can see a search volume, though. ContextBolt SEO is the SEO tool we build to live inside Claude. It connects in claude.ai, Claude Desktop or Claude Code, and brings keyword volumes, the live top ten, backlinks, audits and your own Search Console numbers into the conversation.
- Opus 5.5 is the SEO default now. Anthropic says it performs at Fable 5.1’s level on most work. It costs $4 per million input tokens and $20 per million output.
- Fable 5.1 is for the long jobs. At $10 and $50 per million tokens, it is built for demanding reasoning and long-horizon agentic work.
- Opus 5.5 invented fewer figures. In an Anthropic test where one invented figure failed the report, 16 of 18 Opus 5.5 reports passed. No Fable 5.1 report did.
- Your plan changes the math. Fable 5.1 needs a paid plan, and on Pro it runs on usage credits. Claude Code now defaults to Opus 5.5 on Pro, Max, Team and Enterprise.
- Neither has live SEO data. Both know the web up to June 2026. ContextBolt SEO adds live keyword, SERP and Search Console data inside Claude, free for 7 days and then $35 a month.
What are Claude Fable 5.1 and Opus 5.5?
Claude Fable 5.1 is Anthropic’s flagship. It launched on September 1, 2026, alongside Claude Mythos 5.1, which is the same model with different safeguards and limited access. Anthropic’s announcement calls them “the world’s most advanced models for coding and knowledge work.”
Claude Opus 5.5 is the first model in the new 5.5 family. Anthropic says it “performs at the level of Claude Fable 5.1 on most work” and costs 40% less to run than Opus 5. It also writes output more than 30% faster than Opus 5. Sonnet 5.5 and Haiku 5.5 are due in the coming weeks.
Both have a 1-million-token context window and return up to 128,000 tokens. Both have a reliable knowledge cutoff of June 2026, per Anthropic’s model overview. Both run with thinking always on, and effort runs from low to max.
| Model | Input | Output |
|---|---|---|
| Claude Fable 5.1 | $10 | $50 |
| Claude Opus 5.5 | $4 | $20 |
| Claude Haiku 4.5 | $1 | $5 |
API prices are per million tokens, as of September 23, 2026. Cache reads, where the model reuses context it has already processed, cost $0.25 per million on Fable 5.1 and $0.20 on Opus 5.5. That matters more than it looks. Anthropic says cache reads make up the majority of the cost of agentic and coding work, and an SEO session that keeps calling tools is exactly that kind of work.
Which plans get them
This is where the choice gets made for most people. Anthropic’s help center says Fable 5.1 is on paid plans only.
- Max and Premium seats: Fable is included, and you can spend up to 50% of your weekly usage limits on it.
- Pro and Standard Team seats: Fable is not in the plan’s usage limits. It runs on usage credits.
- Free: no Fable.
Opus 5.5 is the easier one. Claude Code’s model settings make it the default model on Pro, Max, Team and Enterprise, at medium effort. Fable defaults to high effort in Claude Code and to medium on claude.ai, per Anthropic’s announcement.
What do Anthropic’s benchmarks say?
Anthropic published its Opus 5.5 results next to Fable 5.1’s, which makes the comparison unusually direct. Every result below is Anthropic’s own reporting.
| Test | Opus 5.5 | Fable 5.1 |
|---|---|---|
| Knowledge work, GDPval-AA v2.1 | 1846 | 1735 |
| Business workflows, AutomationBench | 40.0% | 31.4% |
| Computer use, OSWorld 2.0 partial | 81.8% | 80.7% |
| Reasoning with tools, HLE | 67.7% | 65.6% |
Opus 5.5 leads on every row. Anthropic ran Opus 5.5 at max effort for these. Zapier ran the Opus 5.5 AutomationBench numbers with no fallback models, so a safeguard stepping in counted as a failure. Anthropic also adds its own caveat. “In our own use, the gap between Opus 5.5 and Claude Fable 5.1 is narrower than these scores suggest.”
The result that matters most for SEO is not in the table. Anthropic asked Opus 5.5, Fable 5.1 and Opus 5 to write a report on a company’s quarterly results, using only what they could find on a copy of the web where the key document was hard to locate. A grader checked every figure and quote, and one invented figure failed the report. 16 of 18 Opus 5.5 reports passed. Neither Fable 5.1 nor Opus 5 passed once.
That is the failure SEO work fears most, a confident number that came from nowhere. On this test, the cheaper model was the one that did not make things up.
None of this is an SEO benchmark, and it is one vendor grading its own models. Treat it as a strong hint, then test the two on your own site.
Which SEO jobs go to which model
Here is how I would split the work in Claude today.
| SEO job | Model |
|---|---|
| Keyword research and picking targets | Opus 5.5 |
| SERP and competitor analysis | Opus 5.5 |
| Briefs, rewrites and on-page fixes | Opus 5.5 |
| A site audit and its fixes in Claude Code | Opus 5.5 |
| A traffic drop across data, rivals and code | Fable 5.1 |
| A large migration or redirect plan | Fable 5.1 |
| Bulk tagging, clustering and meta variants | Haiku 4.5 |
Opus 5.5 does the daily research: Keyword research, SERP reads and briefs all repeat. Opus 5.5 does them at 40% of Fable’s token price and, on Anthropic’s figures, at least as well. Start at its default medium effort and raise it when a job needs more planning.
Fable 5.1 earns its price on the long, tangled job: A traffic drop that runs through Search Console, a competitor’s new pages and last week’s deploy is where holding everything together for hours pays off. Anthropic’s own guidance says to reach for Fable when Opus 5.5 at higher effort still falls short. For SEO, that is a handful of jobs a quarter, not a daily habit.
Haiku 4.5 handles the volume: Grouping 3,000 keywords or writing 400 meta descriptions is long, not hard. Haiku 4.5 is Anthropic’s fastest model and costs a tenth of Fable’s input price. Sonnet 5.5 and Haiku 5.5 are due soon, so check this row again next month.
The cross-vendor version of this split is in GPT-6 Sol and Luna for SEO, where OpenAI’s cheaper models also beat its flagship on cost per task.
The model still cannot see search data
The invented-figure test above says something useful about Opus 5.5. It says nothing about search volume, because search volume is not on the web to find.
Google does not publish how many people search for a phrase. Keyword volumes, difficulty scores and backlink counts come from specialist indexes. Your clicks and impressions sit in your own Search Console. A model that reads the web with perfect honesty still has nothing to read here. It either says it does not know, or it guesses.
It is why Claude SEO always comes back to one setup step. Give Claude a data source.
ContextBolt SEO is ours, and it is built for this. It is a hosted MCP server that Claude calls mid-conversation for keyword research, difficulty, the live top ten, competitor rankings, backlinks, site audits, AI visibility checks and your own Search Console data. The volumes are estimates from a large keyword index, close enough to decide on. The Search Console numbers are your own.
Every lookup saves automatically to your SEO Dashboard, so the research is still there after the chat is closed. The trial gives you 100 credits for 7 days. After that it is $35 a month for 1,000 credits. Research calls cost one credit, and backlink and AI visibility checks cost more.
How to do SEO research with Opus 5.5 and Fable
Start the 7-day free trial first, because sign-in only works for an email with an active trial or subscription. Then, in claude.ai or Claude Desktop, open Settings, then Connectors, then Add custom connector. Paste https://seo.contextbolt.app/mcp and sign in with the email you used for the trial. SEO inside Claude Desktop walks through each screen. Then pick Opus 5.5 from the model menu.
In Claude Code, it is one command.
claude mcp add --transport http contextbolt-seo \
https://seo.contextbolt.app/mcpOpen /mcp in a session, select the server and sign in with the same email. Claude Code runs Opus 5.5 by default on Pro, Max, Team and Enterprise. Type /model fable when a job needs Fable, and /effort to change how hard either model thinks.
Copy this prompt
Use ContextBolt SEO to find where my site is losing ground.
Market: United States
Pull my Search Console data for the last 28 days and the 28 days
before that. List the 10 pages with the biggest drop in clicks.
For the top 3, pull the live top 10 for each page's main query
and tell me what the pages now outranking me do differently.
Give me one fix per page. Do not edit anything yet.Run that on Opus 5.5 first. If the answer for a page is still “it depends”, that page is the job for Fable.
The prompt spends about three credits. The Search Console lookups are free, and each live top ten costs one. So the expensive part of the job is the model’s time, which is why the next setting matters.
Effort settings for SEO work
Claude Code runs Opus 5.5 at medium effort unless you change it, and Fable 5.1 at high. Type /effort to open the slider, or /effort high to set a level directly.
- Keyword research and SERP reads: Opus 5.5 at medium. These jobs are mostly reading tool results, and medium reads them well.
- An audit with fixes: Opus 5.5 at high. One wrong change to a live page costs more than the extra thinking.
- Fable for everyday work: Drop it to medium. Anthropic says Fable 5.1 at low or medium effort already matches or beats Fable 5, at a much lower cost.
- Max: Keep it for the one investigation that has already beaten high. Most SEO work never gets there.
Claude Code’s defaults suit coding. Reading a search results page is lighter work, so it pays to check them once.
Where Fable 5.1 and Opus 5.5 fall short for SEO
Fable is easy to overspend on: On Pro, every Fable session draws on usage credits, and Fable defaults to high effort in Claude Code. A long investigation left running can cost more than the traffic it recovers. Check your plan before you type /model fable.
The benchmarks are not SEO tests: Opus 5.5 leading Fable 5.1 on business workflows does not mean it picks better keywords for your site. Give both the same Search Console export and the same question, and compare the answers you would actually act on.
Honest is not the same as informed: Opus 5.5 was better at not inventing figures in Anthropic’s test. That makes it more likely to say it does not know a search volume. It does not make it know one.
Long, unattended runs cut both ways: One of Anthropic’s early-access partners describes a 38-hour unattended Fable 5.1 run. In SEO, an agent that works through the night can also publish through the night, and search results take months to tell you whether it was right. Let it research and draft. Keep the publish button yours.
So start with Opus 5.5, keep Fable for the jobs that deserve it, and give both the one thing neither has. ContextBolt SEO connects to Claude in a minute, starts with a 7-day free trial, and saves every lookup to your SEO Dashboard. Whether Fable 5.1 is still worth its price after Sonnet 5.5 lands is a question for next month.
