Scan: Will the next Claude Opus model debut at a score of at least 1500 by December 31, 2026?

1. Planner Fable 5.1 · Fermi decomposition + tool plan

Tools chosen: polymarket_direct polymarket_related kalshi_related claude_news claude_news article_search gdelt_news wikipedia code_execution

Sub-questions (Fermi decomposition)

What is the current Polymarket price for this market and for sibling threshold markets (e.g., >=1450, >=1475, >=1525) for the next Claude Opus debut?
What are the current top scores on the Arena.AI Text Arena overall leaderboard with style control OFF, and does any model currently exceed 1500 in that view?
What were the debut no-style-control scores of the most recent Claude Opus models (Opus 4, 4.1, 4.5, and any later Opus) and how did they rank vs. the frontier at debut?
How fast have top-of-leaderboard scores risen over the past 12-18 months (Elo inflation rate), and what does that imply for scores by late 2026?
What is Anthropic's expected release timing for the next Opus model (rumors, cadence, official statements), and is a release before Dec 31, 2026 near-certain?
Does the no-style-control view systematically score models lower/higher than the style-control default view, and how does Claude's verbose style affect its no-style-control score?
Is there any risk the next Opus is labeled something else (e.g., 'Mythos') or added as 'AutoEval' only, or that Arena renames/restructures the leaderboard?

Planner reasoning

Resolution depends on (a) whether Anthropic ships a new Opus model that gets added to the Arena text leaderboard before end of 2026 (very likely given cadence), and (b) whether its debut score in the no-style-control view is >=1500. The key empirical anchors are the current no-style-control top scores, how prior Opus models (4, 4.1, 4.5, and any later) debuted relative to the frontier, and the rate of Elo inflation on the leaderboard. Market price and sibling threshold markets (e.g., 1450/1475/1525) give a crowd-implied distribution to sanity-check against.

2. Research Parallel tool calls

tool	status	time	items	summary
polymarket_direct	OK	0.3s	1	## This Market's Polymarket Data Will the next Claude Opus model debut at a score of at least 1500 by December 31, 2026? - Current price (probability): 78.00% - 7-day price change: +14.50% - 30-day price change: -0.50% - Total volume: $16,768 (USD notional) - Price range: 47.50% - 88.00% - Data
polymarket_related	OK	2.2s	0	Scanned 100 active Polymarket markets, kept 0 matches. keyword 'Claude Opus': 0 markets \| keyword 'Arena': 0 markets \| keyword 'Anthropic': 0 markets \| keyword 'LMArena': 0 markets \| keyword 'text arena': 0 markets
kalshi_related	OK	2.1s	1	1 related markets / summaries. keyword 'Claude': no matches \| keyword 'Anthropic': ok \| keyword 'Arena leaderboard': no matches
claude_news	OK	40.1s	17	Here are the key findings from current searches (note: this data reflects a fast-moving, simulated 2026 landscape with many new "Opus" versions—4.5 through 5—having already launched): - Current arena.ai Text Arena "Overall / no style control" snapshot (Sep 13, 2026): the leaderboard page shows
claude_news	OK	28.7s	12	Based on research into Anthropic's 2026 Claude Opus release cadence and LMArena/Arena.ai text leaderboard data: - Claude Opus 4.5 (Nov 24, 2025) was the baseline reference point, debuting at 1493 Elo on WebDev LMarena as of Nov 26, 2025 . This was just below the 1500 threshold. (medium.com/@le
article_search	OK	0.8s	31	Fetched 31 unique articles across 4 queries (lookback=90d). 'Claude Opus Arena leaderboard score': 10 articles \| 'Anthropic next Claude Opus release 2026': 10 articles \| 'LMArena text leaderboard top score no style control': 10 articles \| 'Anthropic Mythos Claude model': 10 articles
gdelt_news	OK	135.0s	20	GDELT: 20 articles across 3 queries (lookback=60d). 'Claude Opus Arena leaderboard': 10 hits \| 'Anthropic Claude Opus release': error GDELT rate-limited after retries (429) \| 'LMArena leaderboard Gemini GPT top score': 10 hits
wikipedia	OK	0.2s	3	Fetched 3 Wikipedia entries (0 missing pages).
code_execution	OK	51.6s	0	## Key Findings - Historical trend segments show deceleration: growth rate fell from ~153 pts/yr (mid-2024→early-2025) → ~195 pts/yr (early→mid-2025) → ~104 pts/yr (mid→late-2025), reflecting Elo-scale compression as the leaderboard approaches a relative-skill ceiling. - **Naive full-history l

3. Evidence Brief Sonnet 5 · 7013 chars

# Current state The Kalshi/Polymarket contract asks whether the *next* Claude Opus model (first-ever appearance on Arena.ai's Text Arena "no style control" leaderboard) will debut at ≥1500 Elo. Every Opus release since Opus 4.5 (Nov 2025) has landed in a tight ~1486–1510 band around the "1500 line," and the current leaderboard ceiling (Sep 2026) is ~1508, with the top Opus-labeled entry at ~1505. Whichever Opus ships next will debut into a frontier that already sits at/above 1500. # Timeline of key events - 2025-11-24 — Claude Opus 4.5 released; debut Elo ~1493 (WebDev leaderboard, not exact Text-Arena-NSC), ranked #7 in Text Arena at launch. (reported, x.com/medium) - 2026-02-26 — Claude Opus 4.6 debuts; Text Arena NSC scores ~1502–1503 (one high-end report claims ~1567, likely unreliable). (reported, buildmvpfast/apiyi) - 2026-04-16 — Claude Opus 4.7 launches; later settles ~1500–1502 in "Frontier" tier by Sep 2026. (reported) - 2026-05-28 — Claude Opus 4.8 launches; conflicting debut scores ~1486 (June tracker) vs ~1510+ tier (Sep tracker). (reported, ofox.ai/swfte.com) - 2026-06-09 — Claude Fable 5 (Mythos-class, positioned above Opus, does NOT count for this market) reaches ~1510–1525 Elo. (reported) - 2026-06-30 — Export-control dispute briefly disables Fable 5/Mythos 5 access; resolved same week. (confirmed, CNBC) - 2026-07-24 — Claude Opus 5 launches; Anthropic claims major step-change; "claude-opus-5-max" later leads Sep 2026 snapshot at ~1505, though one pull shows "claude-opus-5-high" at 1493. (confirmed release / reported scores) - 2026-09-13 — Current leaderboard snapshot: max score 1508 across 402 models; highest Opus-labeled entry "claude-opus-4-6-high" at 1505. (reported) # Event Will the next Claude Opus model to appear on Arena.ai's Text Arena (overall, no style control) leaderboard debut with a score ≥1500, by Dec 31, 2026? # Outcomes to forecast - Yes (debut score ≥1500) - No (debut score <1500, no qualifying Opus release, or leaderboard/label issues prevent qualification) # Kalshi market anchor No kalshi_direct price was returned in research (only a kalshi_related search, which found unrelated Anthropic markets, not this ticker). **Best available cross-market anchor is Polymarket direct: 78% YES**, up sharply from a 7-day low (+14.5% move, range 47.5%–88% over 30 days), current volume modest ($16.8k total). This should be treated as the effective consensus proxy in the absence of a direct Kalshi quote. # Sub-question answers 1. **Polymarket price / siblings** — Direct market: 78% YES (30-day range 47.5–88%). No sibling threshold markets (≥1450/1475/1525) were found via polymarket_related scan (0 matches). One prior Polymarket analysis cited 1500+ at 65%, 1520+ at 31% for an earlier "next Opus" framing (predictfact.net). 2. **Current top scores / >1500 today** — Yes: Sep 13, 2026 snapshot shows leaderboard max 1508 (402 models); top Opus-labeled model ~1505. Multiple non-Opus models (Fable 5, muse-spark variants) also sit ≥1500. 3. **Recent Opus debut scores** — Opus 4.5: ~1493 (below 1500, WebDev proxy). Opus 4.6: ~1502–1503 (some claims up to 1567, unreliable). Opus 4.7: ~1500–1502. Opus 4.8: ~1486 (June) to "1510+ Frontier" tier (Sep, ambiguous). Opus 5: "opus-5-max" ~1505; "opus-5-high" pull shows 1493. Pattern: post-4.5 Opus debuts cluster right around 1500, sometimes just under, sometimes over. 4. **Elo inflation rate** — code_execution analysis: growth decelerating from ~195 pts/yr to ~104 pts/yr; even conservative deceleration-adjusted model projects frontier ~1521 (Q1'26) to ~1591 (Q4'26) — comfortably above 1500 throughout 2026. 5. **Release timing** — Anthropic's 2026 cadence has been ~2 months apart (4.5→4.6→4.7→4.8→Opus 5 spanning Nov'25–Jul'26); a further Opus release before Dec 31, 2026 is highly likely given this cadence, though not explicitly confirmed/rumored for Q4 2026 in the research. 6. **No-style-control vs. style-control scoring** — No explicit quantified comparison found in research; Claude's outputs are often noted as verbose, which style-control normally discounts, implying NSC scores could be modestly favorable to Claude, but this isn't directly evidenced here. 7. **Mislabeling / AutoEval / restructuring risk** — Real risk exists: Anthropic has introduced a separate "Mythos/Fable" class explicitly positioned *above* Opus (Wikipedia; Fable 5 reached 1510–1525), meaning a top-tier future release could be branded non-Opus and not qualify. No evidence of leaderboard restructuring risk. # Key facts (high-confidence, factual) 1. [polymarket_direct] Current YES price 78%, 7d +14.5%, 30d range 47.5–88%. 2. [claude_news] Sep 13, 2026 leaderboard: max score 1508, top Opus-labeled model ~1505. 3. [claude_news] Opus 4.5 (Nov 2025) debuted below 1500 (~1493); all subsequent Opus releases (4.6–5) have debuted at or near 1500–1505. 4. [Wikipedia] Anthropic now maintains a "Mythos/Fable" tier explicitly above Opus in capability — a non-Opus-labeled model may out-score Opus and not qualify. 5. [code_execution] Trend models project frontier scores staying comfortably >1500 throughout 2026 even under deceleration assumptions. # Cross-market signals - Kalshi related: A separate Kalshi market ("Claude Opus 4.8 debut arena score," threshold >1490) previously existed, suggesting Kalshi runs a family of similar threshold contracts — precedent for this ticker's structure. - Polymarket: 78% YES on this exact market, trending up recently (was as low as 47.5% a month ago). - No sportsbook signal exists for this niche market. # Analyst opinions and speculation - predictfact.net (Polymarket-focused blog) previously modeled 1500+ at 65%, 1520+ at 31% for an earlier iteration of "next Opus." - code_execution synthesis: point estimate ~90% (range 85–95%), driven mainly by release-timing risk rather than score-threshold risk, since frontier trend already clears 1500. # Directional lean per outcome - **Yes**: Supported by consistent recent Opus debuts at/above ~1500, rising frontier trend, strong Anthropic release cadence, and 78% Polymarket price. - **No**: Supported by Opus 4.5's sub-1500 debut, Opus 4.8's ambiguous/lower (~1486) reported score, risk of next flagship being branded Mythos/Fable instead of Opus, and inherent Elo volatility (±4–11 pts) near the threshold. # Gaps / unknowns - No direct Kalshi YES price was retrieved for this exact ticker. - Ambiguous/conflicting reports on Opus 4.8's true debut score (1486 vs 1510+ tier). - No confirmed info on what "next Opus" model (post-Opus 5) is planned or scheduled for late 2026. - No explicit NSC vs. style-control scoring differential data for Claude specifically. # Calibration anchors - Polymarket direct YES price: 78% (best available cross-market anchor; no Kalshi-direct price found). - Precedent: 4 of last 4 Opus releases (4.6, 4.7, 4.8-Sep-tier, Opus 5-max) reportedly reached ≥1500 at some point; only Opus 4.5 debuted clearly below 1500. - Model-based estimate (code_execution): ~90% (range 85–95%).

4. Forecasters Fable 5.1 + GPT-5.6 Sol · in parallel

claude-fable-5-1

45% conf

Yes	72%
No	28%

The Polymarket direct price of 78% YES is the best available anchor (no Kalshi-direct quote), and the frontier already sits at ~1508 with the top Opus-labeled entry near 1505, so any competitive Opus release should land near or above 1500. However, recent Opus debuts cluster tightly around the threshold (4.5 at ~1493, 4.8 possibly ~1486 at debut, Opus 5-high pull at 1493), so Elo noise of ±5–10 points at launch creates real downside risk since the market resolves on the debut score, not the settled score. Additional 'No' pathways include no qualifying Opus release before Dec 31 (cadence suggests one is likely but none is confirmed) and Anthropic branding its next flagship as Mythos/Fable rather than Opus. Netting these, I shade slightly below the market to ~72%.

gpt-5.6-sol

66% conf

Yes	76%
No	24%

The best consensus anchor is Polymarket at 78% YES, since no direct Kalshi price was retrieved. Recent Opus models cluster around the threshold, with several reported near 1502–1505, while the September 2026 leaderboard already has an Opus entry around 1505 and a 1508 overall ceiling. Anthropic's roughly two-month release cadence and continued frontier-score growth favor a qualifying release before year-end, and no-style-control scoring may modestly favor Claude. I shade below the market because debut measurements are noisy, Opus 4.8 may have debuted near 1486, and branding the next flagship as Fable/Mythos—or releasing no new Opus—would resolve No.

5. Devil's Advocate Sonnet 5 · red-team critique

Both forecasters anchor almost entirely on the 78% Polymarket price and shade only slightly down, but neither engages with the code_execution model's independent ~90% estimate or explains why they discount it so heavily despite trend data showing frontier scores "comfortably above 1500 throughout 2026" — this divergence (90% model vs ~72-76% final) is unresolved and under-justified.

Neither forecaster meaningfully weights the "no qualifying release by Dec 31" pathway as a distinct probability — the brief flags "no confirmed info on what 'next Opus' model (post-Opus 5) is planned" as a genuine gap, yet given the observed ~2-month cadence already produced 5 Opus releases in under a year, a 6th release failing to appear at all seems like a minor risk that's being conflated with (and possibly double-counted against) the branding/Mythos risk.

Both treat the Mythos/Fable branding risk as a modest haircut, but the brief's evidence is fairly stark: Fable 5 already reached 1510-1525 and is "explicitly positioned above Opus" — if Anthropic's flagship-tier releases are migrating to this brand, the *next* Opus specifically could be a lower-tier/legacy model deliberately kept below 1500, which is a structurally different (and possibly larger) risk than transient Elo noise, yet both rationales lump it in as a minor bullet point.

Neither forecaster addresses the significant ambiguity in Opus 4.8's debut score (1486 vs "1510+ tier") as a base-rate data point — if 4.8 truly debuted at 1486, that's 2 of the last 5 Opus debuts (4.5 and 4.8) below 1500, which is a meaningfully worse hit rate than the "4 of last 4" framing in the calibration anchors section, and this discrepancy should have been explicitly reconciled rather than glossed over.

Both forecasts ignore the steep 30-day price swing (47.5% to 88%, currently 78%) as a signal of thin, volatile market pricing on low volume ($16.8k) — this warrants more caution/wider uncertainty bands than the tight 0.72-0.76 clustering both forecasters present, especially given confidence levels (0.45, 0.66) that don't reflect this instability.

Neither forecaster explores the tail scenario where the "next Opus" resolves ambiguously due to leaderboard mislabeling or dual-naming (e.g., "opus-5-max" vs "opus-5-high" giving conflicting scores 1505 vs 1493 for the *same* release), which could itself trigger resolution disputes independent of the true score — this measurement/resolution risk is distinct from Elo noise and deserves separate treatment.

6. Aggregator Fable 5.1 · final calibrated forecast

74% (56% confidence)

Yes: 74% No: 26%

The Polymarket anchor (78%) is the best available consensus proxy, and the frontier already sits at ~1508 with an Opus-labeled entry at ~1505, so a post-Opus-5 release competitive with its predecessor should clear 1500; Anthropic's ~2-month cadence makes a qualifying release before Dec 31 likely. I discount the code_execution ~90% because its trend model is contradicted by the observed leaderboard: the ceiling moved only ~1493→1508 over ten months, meaning the next Opus will debut in the same noisy 1490–1510 band rather than comfortably above it. Genuine No pathways remain: Opus 4.5 (~1493) and possibly Opus 4.8 (~1486) debuted below 1500, variant labeling (opus-5-high at 1493 vs opus-5-max at 1505) shows the 'debut' entry can land under the line, and Anthropic's Mythos/Fable tier could absorb the flagship-quality release. Netting these against the thin, volatile market, I land at 74%, slightly under the market and between the two forecasts.

Pipeline Timing

Total pipeline time: 250.2s

Per-tool research timings shown in the Research section above.