{"id":502,"date":"2026-08-25T06:28:10","date_gmt":"2026-08-25T06:28:10","guid":{"rendered":"https:\/\/i10x.ai\/blog\/?p=502"},"modified":"2026-08-25T06:29:19","modified_gmt":"2026-08-25T06:29:19","slug":"claude-fable-5-vs-claude-opus-5","status":"publish","type":"post","link":"https:\/\/i10x.ai\/blog\/claude-fable-5-vs-claude-opus-5","title":{"rendered":"Claude Fable 5 vs Claude Opus 5: Same Family, Different Price (2026)"},"content":{"rendered":"\n
\n\n

Comparison \u00b7 August 2026<\/p>\n\n

\nClaude Fable 5 and Claude Opus 5 are two Anthropic models on the same card shape: 1M context, text\/image\/file in, text out. Fable is billed as Mythos-class autonomous knowledge work. Opus 5 is billed as the flagship for demanding reasoning, coding, and long-horizon agents. The list-price gap is the story: Fable is $10 \/ $50, Opus is $5 \/ $25. This guide uses those specs, three workload costs, and live snippets. Keep both in a\nmulti-model AI workspace<\/a>\nor start on\ni10X<\/a>.\n<\/p>\n\n

\nQuick verdict<\/strong>\n

Pick Claude Fable 5 if:<\/strong> you specifically want Mythos-class autonomous knowledge work, a subject-line email shell, and a coding note that debates return 0 vs ValueError as a contract choice.<\/p>\n

Pick Claude Opus 5 if:<\/strong> you want the same 1M context and the same modalities at half the sticker, warmer complete emails in our capture, a more pedagogical bug writeup, and a geology-first refusal of a false premise.<\/p>\n

Best default for many teams:<\/strong> start Opus 5. Pay Fable rates only when a Fable-only session is the product, not when you need \u201ca Claude.\u201d Route by task inside Anthropic, and still keep a second provider for critique.<\/p>\n

Data checked: 2026-08-24 via live side-by-side API tests. Prices change. Verify live vendor pages.<\/em><\/p>\n<\/div>\n\n

\n\n\n\n\n\n\n

1M \/ 1M<\/strong><\/p><\/td>\n

Claude Fable 5 and Claude Opus 5 context (API)<\/p><\/td>\n<\/tr>\n

$10 \/ $50<\/strong><\/p><\/td>\n

Claude Fable 5 input\/output per 1M tokens (API pricing, 2026-08-24)<\/p><\/td>\n<\/tr>\n

$5 \/ $25<\/strong><\/p><\/td>\n

Claude Opus 5 input\/output per 1M tokens (API pricing, 2026-08-24)<\/p><\/td>\n<\/tr>\n

2x<\/strong><\/p><\/td>\n

Fable list rates vs Opus on input, output, and cache<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n\n

\n\"Bar\n
Figure 1.<\/strong> Where each model wins on relative axes (context, modalities, output cost efficiency). Context and modalities match. Opus leads output cost efficiency because it is half the Fable sticker. Chart: i10X.<\/figcaption>\n<\/figure>\n\n
\n\n

Persona picker<\/h2>\n\n\n\n\n\n\n\n\n

You are\u2026<\/p><\/th>\n

Start with<\/p><\/th>\n

Why<\/p><\/th>\n<\/tr>\n

Writer \/ CS \/ marketer<\/p><\/td>\n

Claude Opus 5 (often)<\/p><\/td>\n

Opus\u2019s captured rewrite was warmer and more complete (greeting, Finance delay, Wednesday option, competitive slide). Fable had a subject line, then truncated.<\/p><\/td>\n<\/tr>\n

Developer \/ agent builder<\/p><\/td>\n

Claude Opus 5 default<\/p><\/td>\n

Vendor copy puts Opus on end-to-end software, code review, and bug finding. Our micro-fix: both correct; Opus explained the 0\/0 path more clearly.<\/p><\/td>\n<\/tr>\n

Researcher \/ analyst<\/p><\/td>\n

Either (same 1M + files)<\/p><\/td>\n

Identical listed context and text\/image\/file inputs. Pick on writeup quality and price, not window size.<\/p><\/td>\n<\/tr>\n

Budget \/ high volume API<\/p><\/td>\n

Claude Opus 5<\/p><\/td>\n

Half the input, output, and cache list rates. Every stylized workload in this article is ~2x on Fable.<\/p><\/td>\n<\/tr>\n

Mythos-class autonomous sessions<\/p><\/td>\n

Claude Fable 5<\/p><\/td>\n

That is the vendor lane. Do not pay it as a synonym for \u201cbest Claude.\u201d<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n

\n\n

What we are comparing (exact versions)<\/h2>\n

Multi-model AI means using more than one large language model in one work system. This page compares two specific Anthropic API models, not a vague \u201cClaude vs Claude\u201d brand fight and not older Opus 4.x writeups.<\/p>\n\n\n\n\n\n\n\n\n

Field<\/p><\/th>\n

Claude Fable 5<\/p><\/th>\n

Claude Opus 5<\/p><\/th>\n<\/tr>\n

Provider<\/p><\/td>\n

Anthropic<\/p><\/td>\n

Anthropic<\/p><\/td>\n<\/tr>\n

API model<\/p><\/td>\n

Claude Fable 5<\/code><\/p><\/td>\n

Claude Opus 5<\/code><\/p><\/td>\n<\/tr>\n

Listed API name<\/p><\/td>\n

Anthropic: Claude Fable 5<\/p><\/td>\n

Claude Opus 5<\/p><\/td>\n<\/tr>\n

Family \/ tier<\/p><\/td>\n

Mythos-class; autonomous knowledge work and coding<\/p><\/td>\n

Opus flagship; demanding reasoning, coding, long-horizon agents<\/p><\/td>\n<\/tr>\n

App vs API note<\/p><\/td>\n

Also in Claude products; this article uses the API model above<\/p><\/td>\n

Also in Claude products; this article uses the API model above<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

If you still see posts comparing Opus 4.x to unnamed \u201cClaude\u201d siblings, treat them as older. Sibling routing inside one vendor is still routing. See\nAI model routing<\/a>.<\/p>\n\n

\n\n

Spec sheet (API, 2026-08-24)<\/h2>\n\n\n\n\n\n\n\n\n\n\n

Spec<\/p><\/th>\n

Claude Fable 5<\/p><\/th>\n

Claude Opus 5<\/p><\/th>\n<\/tr>\n

Context window<\/p><\/td>\n

1,000,000 tokens<\/p><\/td>\n

1,000,000 tokens<\/p><\/td>\n<\/tr>\n

Max output (if published)<\/p><\/td>\n

Not published on the card we pulled<\/p><\/td>\n

Not published on the card we pulled<\/p><\/td>\n<\/tr>\n

Input modalities (card)<\/p><\/td>\n

text, image, file<\/p><\/td>\n

text, image, file<\/p><\/td>\n<\/tr>\n

Output<\/p><\/td>\n

text<\/p><\/td>\n

text<\/p><\/td>\n<\/tr>\n

Reasoning<\/p><\/td>\n

Vendor copy mentions reasoning support<\/p><\/td>\n

Vendor copy: demanding reasoning, long-horizon agentic work<\/p><\/td>\n<\/tr>\n

Open weights<\/p><\/td>\n

Not listed as open weights on the card we pulled<\/p><\/td>\n

Not listed as open weights on the card we pulled<\/p><\/td>\n<\/tr>\n

Vendor positioning (short)<\/p><\/td>\n

Mythos-class autonomous knowledge work and coding<\/p><\/td>\n

Flagship for reasoning, coding, code review, bug finding, visual analysis<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Structurally these two are twins on the card we pulled: same window, same modalities, same output type. We are not citing third-party leaderboard numbers. The live pack and the 2x price gap are the evidence on this page.<\/p>\n\n

\n\n

Pricing and real workload cost<\/h2>\n

List prices are easy to misread. Workload cost is what you feel. Rates below are from published API pricing on 2026-08-24<\/strong>.<\/p>\n\n\n\n\n\n\n

Price<\/p><\/th>\n

Claude Fable 5<\/p><\/th>\n

Claude Opus 5<\/p><\/th>\n<\/tr>\n

Input \/ 1M tokens<\/p><\/td>\n

$10.00<\/p><\/td>\n

$5.00<\/p><\/td>\n<\/tr>\n

Output \/ 1M tokens<\/p><\/td>\n

$50.00<\/p><\/td>\n

$25.00<\/p><\/td>\n<\/tr>\n

Cache read \/ 1M<\/p><\/td>\n

$1.00<\/p><\/td>\n

$0.50<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Opus is half the Fable sticker<\/strong> on input, output, and cache. That is a clean 2x, not a rounding quirk.<\/p>\n\n\n\n\n\n\n

Scenario<\/p><\/th>\n

Assumed tokens<\/p><\/th>\n

Est. Claude Fable 5<\/p><\/th>\n

Est. Claude Opus 5<\/p><\/th>\n<\/tr>\n

Chat turn<\/p><\/td>\n

1k in + 0.5k out<\/p><\/td>\n

$0.035<\/p><\/td>\n

$0.0175<\/p><\/td>\n<\/tr>\n

Repo \/ doc review<\/p><\/td>\n

80k in + 4k out<\/p><\/td>\n

$1.00<\/p><\/td>\n

$0.50<\/p><\/td>\n<\/tr>\n

Agent loop<\/p><\/td>\n

200k in (50% cached) + 20k out<\/p><\/td>\n

$2.10<\/p><\/td>\n

$1.05<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\n\"Bar\n
Figure 2.<\/strong> Estimated USD per run using published API list rates (2026-08-24). Fable is 2x Opus on each stylized workload. Chart: i10X.<\/figcaption>\n<\/figure>\n

Cached agent loops stay a clean 2x. For subscription stacks, see\nAI subscription stack cost<\/a>. Always verify live vendor pages before budgeting.<\/p>\n\n

\n\n

Performance by job (specs + live pack)<\/h2>\n

Same vendor, same window, same modalities. Public benches would still be a poor way to split these two without a harness you own. We use the live pack. Method:\nside-by-side AI comparison<\/a>.<\/p>\n\n

Coding and agents<\/h3>\n

Opus 5\u2019s vendor card stresses end-to-end software tasks, code review, bug finding, and long-horizon agentic work. Fable 5\u2019s card stresses autonomous knowledge work and coding with reasoning support. Our empty-list test: both named ZeroDivisionError and guarded with if not nums<\/code>. Fable offered return 0 or ValueError as a contract choice. Opus walked the failure: the loop never runs, total stays 0, the return still evaluates 0\/0, and any caller that passed an empty filter will crash. That is the better teaching note. It is still one snippet.<\/p>\n\n

Writing and tone<\/h3>\n

Fable produced a subject line (\u201cQ3 Deck Update & Proposed Meeting Change\u201d) and a flexible reschedule. The capture truncated at the competitive-slide note. Opus opened with \u201cI hope you\u2019re doing well!\u201d, hit the Q3 deck, missing finance numbers, Friday promise, Wednesday option with an offer to adjust, then started the competitive-slide thought. Opus was the warmer complete letter in the window we have. Fable was the more \u201cinbox-native\u201d shell.<\/p>\n\n

Research, math, reasoning<\/h3>\n

Both refused the green-cheese Moon. Fable: silicates (feldspar, pyroxene) plus iron and titanium, Apollo-style confirmation, no protein to mine, optional real topics (water ice, oxygen, helium-3). Opus: called it an old folk joke, then named basalt in the maria, anorthosite in the highlands, dusty regolith, Apollo and Luna samples, and no biological organic matter. Opus is the better geology lesson in this pack. Fable is the better \u201chere are adjacent real topics\u201d index.<\/p>\n\n

Multimodal and long context<\/h3>\n

No structural edge. 1,000,000 tokens each. Text, image, file in. Text out. Visual analysis is in the Opus vendor line; Fable\u2019s card does not call it out the same way. We did not run a screenshot pack in this batch, so that remains a positioning note, not a live score.<\/p>\n\n

Speed<\/h3>\n

Not measured in this pack. Do not ship a latency claim from someone else\u2019s screenshot. Measure p50 from your region.<\/p>\n\n\n\n\n\n\n\n\n\n

Job<\/p><\/th>\n

Edge<\/p><\/th>\n

Why<\/p><\/th>\n<\/tr>\n

Hard coding \/ agents<\/p><\/td>\n

Claude Opus 5 (this pack + vendor line)<\/p><\/td>\n

Clearer 0\/0 walkthrough; vendor copy on code review and bug finding<\/p><\/td>\n<\/tr>\n

Everyday writing<\/p><\/td>\n

Claude Opus 5 (often)<\/p><\/td>\n

Warmer complete letter in our capture; Fable had the subject line<\/p><\/td>\n<\/tr>\n

Long docs \/ files \/ images<\/p><\/td>\n

Tie on the card<\/p><\/td>\n

Same 1M and same modalities<\/p><\/td>\n<\/tr>\n

False-premise handling<\/p><\/td>\n

Claude Opus 5 (this pack)<\/p><\/td>\n

Stronger geology; both refuse first<\/p><\/td>\n<\/tr>\n

Cost at volume<\/p><\/td>\n

Claude Opus 5<\/p><\/td>\n

Half the Fable list rates on every stylized workload<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n

\nHow to read this<\/strong>\n

Paying 2x inside one vendor needs a job this pack did not win for Fable. If you cannot name that job, default Opus 5. Re-test on your prompts.<\/p>\n<\/div>\n\n

\n\n

Side-by-side test (live API test, 2026-08-24)<\/h2>\n

We ran the same prompts on Claude Fable 5<\/code> and Claude Opus 5<\/code> in a multi-model workspace. This batch captured three live prompts. Scores are editorial 1-5 on instruction following, depth, factual caution, style, and usefulness (max 25 per prompt).<\/p>\n\n

Test 1: Client email rewrite<\/h3>\n

Task:<\/strong> Keep every fact. Warmer. Under 120 words.<\/p>\n

Claude Fable 5 (excerpt):<\/strong> Subject line, \u201cHi [Name],\u201d Q3 deck from last Tuesday, Finance still missing after Friday, move stakeholders to next week (Wednesday, happy to adjust). Capture ends at \u201cwe\u2019ll be updating the com.\u201d<\/p>\n

Claude Opus 5 (excerpt):<\/strong> \u201cHi [Name], I hope you\u2019re doing well!\u201d Then the Q3 follow-up, finance numbers promised Friday and still missing, Wednesday next week with an offer to adjust, then \u201cOne more thing: the competitive slide.\u201d<\/p>\n

Edge:<\/strong> Opus for warmth and a complete captured arc. Fable for the subject line. If managers want human scaffolding, Opus. If you paste into a mail client that needs a subject, Fable.<\/p>\n\n

Test 2: Empty-list average bug<\/h3>\n

Both correct. Fable: short bug label, minimal fix, contract fork (0 vs ValueError). Opus: headed \u201cThe bug,\u201d explained that the loop never runs and the return still does 0\/0, then the same guard (0.0) with a ValueError option. Tie on the patch. Opus on the explanation.<\/strong><\/p>\n\n

Test 3: False premise (Moon cheese)<\/h3>\n

Both refused first. Fable listed minerals and offered real extraction topics. Opus named the folk joke, maria basalt, highland anorthosite, regolith, Apollo and Luna, and no biological protein. Both pass.<\/strong> Opus is the better \u201cdo not humor the premise\u201d geology note. For publishable claims, still use\nmulti-model hallucination checks<\/a>.<\/p>\n\n\n\n\n\n\n\n\n

Prompt<\/p><\/th>\n

Claude Fable 5<\/p><\/th>\n

Claude Opus 5<\/p><\/th>\n

Note<\/p><\/th>\n<\/tr>\n

Email rewrite<\/p><\/td>\n

22\/25<\/p><\/td>\n

23\/25<\/p><\/td>\n

Fable: subject, truncated. Opus: warmer, more complete capture<\/p><\/td>\n<\/tr>\n

Bug fix<\/p><\/td>\n

24\/25<\/p><\/td>\n

24\/25<\/p><\/td>\n

Tie on the patch; Opus more pedagogical<\/p><\/td>\n<\/tr>\n

False premise<\/p><\/td>\n

23\/25<\/p><\/td>\n

24\/25<\/p><\/td>\n

Both refuse; Opus stronger lunar geology<\/p><\/td>\n<\/tr>\n

Total (this pack)<\/strong><\/p><\/td>\n

69\/75<\/strong><\/p><\/td>\n

71\/75<\/strong><\/p><\/td>\n

Close on quality. Not close on price.<\/p><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Inside one vendor, a two-point editorial gap plus a 2x bill is an Opus default until Fable wins a job you can name (Mythos-class autonomy, subject-line drafts, a repo this pack did not touch).<\/p>\n\n

\n\n

Ecosystem and where you run them<\/h2>\n