explainx / blog
@AstraiaAI claimed Sonnet 1T, Opus 5T, Fable/Mythos 10T from Anthropic's compute partner. Musk's Grok 0.5T math matches — but throughput analysis and Anthropic silence say treat all figures as Tier-3 inference, not fact.
Jul 14, 2026
Claude Pro at ₹2,000/mo annual (₹2,399 monthly), Max from ₹11,999, Team from ₹2,399/seat — India's #2 Claude market finally bills in rupees. explainx.ai breaks down GST, payment gaps, and Fable 5 access.
Jul 12, 2026
Anthropic's Fable promo ends Sunday July 12 at 11:59pm PT. From July 13 every Fable token runs on usage credits at API rates. explainx.ai explains what changes today and how to cut costs with Sonnet + advisor patterns.
Jul 8, 2026
The July 7 Fable credit cliff moved to July 12. Anthropic's email confirms 50% weekly Fable through Sunday night PT; all Fable usage bills as credits from July 13. explainx.ai explains the extension and updates billing timelines.
July 19–20, 2026: @AstraiaAI posted a thread that hit ~197K views in hours:
"I'm surprised this wasn't common knowledge — Sonnet is 1T parameters. Opus is 5T parameters. Fable/Mythos is 10T parameters."
Replies split between "finally someone said it" and "src?" — @Odd_Xignal asked for better sources; @mark_k and @alessandro_a0 called the figures unfounded X/Reddit estimates. Astraia doubled down: "By Anthropic's primary compute partner. Cut the cope."
The numbers are not Anthropic official. They do rhyme with an earlier public anchor almost everyone missed when it first dropped: Elon Musk's Grok sizing comment — the same ratios Astraia now calls "common knowledge."
| Claim | Who said it | Evidence tier | explainx.ai read |
|---|---|---|---|
| Sonnet ≈ 1T total | Astraia (Jul 19); implied by Musk (Apr 2026) | Tier 2–3 — hearsay + algebra | Plausible order-of-magnitude; unconfirmed |
| Opus ≈ 5T total | Same | Tier 2–3 | May describe Opus 4/4.1 era or marketing round-number; current 4.5/4.6 serving tier may be smaller |
| Fable/Mythos ≈ 10T total | Astraia; some researcher forums | Tier 3 only | Highest controversy — throughput math argues against 10T for what Vertex/Bedrock serve today |
| Grok ≈ 0.5T total | Musk (direct) | Tier 1 for Grok only | Confirmed by Musk; used as ratio anchor for Claude |
| Anthropic official counts | — | None published | Procurement should not cite X threads |
In April 2026, @MetaMaster asked whether Grok 4.20 is 500B total or 500B active in a larger MoE. Musk replied (paraphrased from multiple mirrors including Adam Holter's breakdown and 36Kr's coverage):
"0.5T total. Current Grok is half the size of Sonnet and 1/10th the size of Opus. Very strong model for its size."
Back-of-napkin math:
| If Grok = | And Grok is… | Implied size |
|---|---|---|
| 0.5T | ½ × Sonnet | Sonnet ≈ 1T |
| 0.5T | ¹⁄₁₀ × Opus | Opus ≈ 5T |
Musk was defending Colossus 2 training seven models, including a 10T flagship — so the ratios served xAI's "efficient at scale" narrative. Netizens immediately posted "Sonnet 1T, Opus 5T"; Anthropic never commented.
Astraia's July thread adds Fable/Mythos at 10T — aligning Mythos with xAI's largest training target, not Musk's 0.5T shipping Grok. That leap is Astraia's extension, not Musk's quote.
For Grok-vs-Claude product context, see explainx.ai's Grok 4.5 vs Claude Opus comparison and Grok 4.5 private beta at SpaceX/Tesla (V9 1.5T foundation — a different numbering scheme entirely).
Across Fable 5 / Mythos 5 launch, export-control restores, and July Fable limit extensions, Anthropic discloses:
Not disclosed: total parameters, active parameters per token, expert counts, training token volume, or MoE routing ratios.
That silence is strategic — parameter counts are easy to misread (total vs active), fuel competitive intelligence, and age poorly when Anthropic ships distilled tiers under familiar names.
Independent analyst unexcitedneurons (March 2026) estimated Claude Opus 4.5/4.6 using OpenRouter token/sec on Google Vertex, calibrated against open MoE models with known active params (DeepSeek V3.1, GLM-4.7, Kimi K2).
Core method: decode throughput ≈ f(active parameters loaded per token). Compare Opus vs Chinese MoE baselines on the same cloud stack — providers are not incentivized to artificially slow one model.
Findings relevant to the July debate:
| Model (served) | Throughput signal | Estimated total params (MoE-dependent) |
|---|---|---|
| Opus 4.5/4.6 | ~40–43 tps on Vertex | ~1T–3T depending on 8:160 vs 8:256 vs 8:384 routing |
| Sonnet 4.5/4.6 | Faster than Opus (~41–51 tps) | Smaller; author guesses ~1.5× ratio, not 5× |
| Casual "10T+" Opus | Would imply ~10× slower serving vs DeepSeek/Kimi | "Inconsistent with observed throughput" |
The author argues Anthropic likely pretrains multi-trillion checkpoints (Opus 4/4.1 era ~5T–6T in their reconstruction) then distills into cheaper "Opus 4.5" tiers that are closer to a heavily post-trained Sonnet — explaining why API pricing dropped 3× from Opus 4.1 ($15/$75) to Opus 4.5/4.6 ($5/$25) while the brand name stayed "Opus."
Implication for Astraia's chart:
@Build4mBottom replied "no even mythos is 4t" — Astraia: "You are wrong." No primary document settles it.
What is official: Fable 5 and Mythos 5 share one model — Mythos lifts safeguards for Annex A cyber-defender cohorts. Parameter count, if any, would be identical; only policy differs.
Third-party synthesis (e.g. AIThinkerLab's evidence review) stacks Musk ratios, Mythos ~10T forum lore, and cost reverse-engineering into a Tier-3 bucket — explicitly not Anthropic confirmed.
@crystlizedd captured the benchmark paradox:
"oh, so fable 5 is getting beat by Kimi K3... A 3T param model?"
Moonshot's Kimi K3 platform docs cite 2.8T total, 16/896 experts active — a different point on the total vs active curve than a hypothetical 10T / ~1T-active Mythos MoE. GPT-5.6 vs Fable 5 shows frontier rankings moving on benchmarks and price, not parameter leaderboard bragging.
Critics in Astraia's replies (@DBrodniak, @altanaldeniz, @virtualcity69) converge on fair points:
What skeptics underweight: Musk's ratios have stayed stable for months, repeated by multiple outlets, and match pricing/distillation narratives if "Opus 5T" means legacy pretrain not July 2026 endpoint.
| If you need… | Do this | Don't do this |
|---|---|---|
| Procurement slides | Cite benchmarks + $/task from Fable vs GPT-5.6 | Paste 10T from X without "unverified" label |
| Capacity planning | Measure your tokens/sec and queue depth on Anthropic API | Assume 10T dense memory footprints |
| Competitive intel | Track distillation + rename patterns (Opus 4.1 → 4.5 pricing cliff) | Treat parameter rumors as Moat fact |
| Research citations | Write: "Anthropic undisclosed; third-party estimates range ~1T–5T served, ~10T attributed to Mythos-class MoE in unverified reports" | Attribute 10T to Anthropic officially |
July 19, 2026 revived a months-old Musk algebra problem: Grok 0.5T ⇒ Sonnet ~1T, Opus ~5T. @AstraiaAI added Fable/Mythos 10T and claimed compute-partner sourcing — without verifiable primary documents.
Anthropic still publishes zero parameter counts. The strongest public counter to 10T shipping today is inference throughput (unexcitedneurons): Opus 4.5/4.6 behaves like low-trillions MoE, not an order-of-magnitude larger monster. Kimi K3 at 2.8T beating Fable on some tasks is a feature-quality story, not a disproof that Anthropic ever trained larger sparse checkpoints.
explainx.ai's position: repeat Musk's ratios with attribution; label Astraia's 10T and partner claim Tier-3; demand Anthropic disclosure or your own benchmarks before betting architecture.
Primary / secondary sources: @AstraiaAI Jul 19 thread · Adam Holter — Musk ratios · unexcitedneurons throughput estimate · PsyArXiv — cognitive surrender study (epistemic humility companion)
Parameter claims, Musk quotes, and throughput estimates reflect public posts through July 20, 2026. Anthropic may ship new tiers without updating any public cardinality. Not investment or procurement advice.
