**Intelligence Radar — Daily Brief**  
**Sunday, 27 September 2026 (Europe/Berlin)**  

Frontier weather: clustered mid-tier releases and aggressive price compression dominate; capability increments remain jagged and agentic-harness dependent rather than pure scale jumps.

### 1. Frontier & markets
Confirmed releases this week concentrate on accessible mid-to-high tiers rather than new absolute ceilings. Anthropic’s Claude Opus 5.5 (22 Sep) is positioned as delivering Fable 5.1-class agentic and knowledge-work performance at $4 / $20 per million tokens (20 % below prior Opus 5; cache reads cut further to ~$0.20). Independent reports place it near the top of Artificial Analysis Intelligence Index v4.3.x among generally available models (~57–58).

OpenAI followed within hours with GPT-6 Sol ($2 / $10) and GPT-6 Luna ($0.10 / $0.50), roughly halving the prior GPT-5.6 promotional rates while keeping scores roughly level with the previous generation on AAII and Coding Agent Index (progress on some evals, regressions on others). GPT-6 Astra (earlier September, $10 / $50) remains the higher-capability, higher-price reference for computer-use and cyber-threshold work.

xAI’s Grok 4.7 (21 Sep) scores 46 on AAII v4.3 and improves Coding Agent Index enough to overtake prior GPT-5.6 Sol entries in some reports; list price held near $2 / $6 range. Xiaomi’s MiMo-V2.6-Pro / Flash (open-weight leaning) and today’s MiniMax M3.1 Flash Preview add to the dense mid-tier supply. Meta’s Muse Spark 1.3 and Google’s Gemini 3.8 Flash (TTS variants this week) continue the low-latency / voice push.

Availability remains bifurcated: Mythos / Fable-class and certain cyber / life-science variants stay gated (trusted-access or export-controlled programs). Price moves are first-class: cache discounts, batch tiers, and temporary Flash introductory rates (Google’s 3.8 Flash holds $0.75 / $3.75 through year-end) expand the efficient frontier faster than raw scores. No major capacity pauses reported this cycle; Chinese open-weight releases (Z.ai GLM-5.3 lineage, Qwen3.8 variants) continue to undercut on blended cost.

Benchmarks: Terminal-Bench 4.0 (harder, rotated set) still shows GPT-6 Astra / Fable 5.1 near 58 % under strong harnesses; older 2.x versions are approaching saturation at the frontier (>90 % for top entries). SWE-bench Verified remains heavily saturated for closed models (>95 % self-reported for recent Claude Opus / Fable). AAII v4.3 (Terminal-Bench 4.0 + AutomationBench-AA + AA-Briefcase etc.) is the current reference; do not mix with prior versions.

### 2. Science of intelligence
Measurement continues to shift toward long-horizon, agentic, and private-test-set evaluations. Epoch’s Capabilities Index (ECI) shows the post-reasoning-model frontier advancing ~14 points/year; GPT-6 Astra currently leads overall ECI while lagging relative software-engineering standing in some splits. Open models trail closed by roughly four months / ~8 ECI points on average.

arXiv activity (cs.AI / LG) highlights recursive self-improvement loops (AIDE²-style agents that edit and re-benchmark their own code over multi-day runs, transferring gains to held-out R&D tasks) and curriculum methods that simplify reasoning traces for smaller models. “Endless Exam” style construction benchmarks attempt open-ended mathematical progress without hard caps. These remain early signals; no primary lab theory papers from Amodei / Hassabis / Tenenbaum / Ganguli / Chollet this exact window overturn prior scaling or measurement frameworks.

### 3. Engineering
Agent scaffolding and harness choice dominate residual variance once models clear ~50 on AAII. Terminal / computer-use boards (OSWorld, Terminal-Bench 4.0) reward persistent memory, tool-call efficiency, and self-verification more than parameter count. Inference economics: aggressive cache pricing and MoE / speculative decoding keep mid-tier token costs falling; energy and power density remain the longer-term constraint (Epoch data-center tracking now covers ~44 % of global AI compute stock). Chip / cluster news quiet this week; prior Stargate-scale runs for Astra-class models remain the reference.

### 4. Political / legal / social
Export controls and trusted-access programs continue to segment the absolute frontier (Mythos, certain cyber variants). No major new regulatory texts dropped this weekend. Usage data (Epoch/Ipsos) show near-daily AI adoption among U.S. adults rising sharply through August. Economic pressure is visible in enterprise evaluation fatigue: rapid release cadence strains internal testing capacity.

### 5. Watchlist hits (primary)
- Anthropic Claude Opus 5.5 model card / pricing (22 Sep) — confirmed capability + price cut.  
- OpenAI GPT-6 Sol / Luna API announcements (22 Sep) — confirmed price compression.  
- xAI Grok 4.7 release notes (21 Sep).  
- Artificial Analysis Intelligence Index v4.3 changelog and Opus 5.5 / Grok 4.7 entries.  
- Epoch AI ECI / data-center updates (mid-to-late Sep).  
- Terminal-Bench 4.0 official leaderboard (Stanford / Harbor / Laude).  
- arXiv:2609.26457 (recursive self-improvement of research agents), 2609.24555 (Endless Exam).

### 6. Ledger actions
- **Frontier label**: Claude Opus 5.5 and GPT-6 Astra remain the primary candidates on agentic / coding boards under strong harnesses; Fable / Mythos stay restricted. Re-evaluate once independent Terminal-Bench 4.0 and AA-Briefcase numbers stabilize for Opus 5.5.  
- **Efficient**: GPT-6 Sol / Luna and Gemini 3.8 Flash (intro pricing) move the cost-per-task Pareto; Muse Spark 1.3 and Chinese open-weight (MiMo, GLM-5.3 Flash) compete hard on blended rate.  
- **Budget**: Luna-class and Flash-Lite tiers.  
- Five-benchmark atlas (AAII v4.3, Terminal-Bench 4.0, SWE-bench Pro / Verified under fixed harness, OSWorld, HLE or SciCode): no full rebase required yet; note Terminal-Bench version and harness explicitly. Saturated Verified numbers should not drive ranking.

### 7. Sources
Primary and near-primary: Artificial Analysis (intelligence-index articles & changelog), Epoch AI data insights & ECI, Terminal-Bench maintainers, Anthropic / OpenAI / xAI / Google release notes and pricing pages (via contemporaneous trackers that cite them), arXiv cs.AI submissions 21–22 Sep 2026, BenchLM / model-release trackers cross-checked against provider announcements.

Ask Intelligence Radar a task for a Task Router ticket (5 benchmarks → Frontier / Efficient / Budget + optional decomposition).