The AI Workflow I’m Using This September, From Opus To Jev
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🔍 Read the full analysis: The AI Workflow I’m Using This September, From Opus To Jev on ThorstenMeyerAI.com

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TL;DR

In a Sept. 29 account, Thorsten Meyer describes using Opus 5.5 for building, GPT-6.1 Sol for detailed review, and Jev for high-volume yes-or-no and routing decisions. His model and cost comparisons draw on Artificial Analysis Intelligence Index v4.3.x, which he says should be treated as a general capability guide rather than a measure of performance on every workload.

Thorsten Meyer says he is using Claude Opus 5.5 to build, GPT-6.1 Sol to examine details and review changes, and Jev for high-volume yes-or-no and routing judgments. In a Sept. 29 account, he frames the workflow around differences in task cost among models whose Artificial Analysis Intelligence Index scores are relatively close, while cautioning that the index does not establish which model will perform best on a particular workload.

Meyer assigns Opus 5.5 at high effort to features, APIs, multi-file work and refactoring, citing an index score of 54 and a listed cost of $1.82 per task. For architecture, migrations and trust boundaries, he uses the xhigh setting, which scores 56 at $3.46 per task in the supplied table. He says he rarely uses max effort: Opus rises from 56 at xhigh to 58 at max, while the listed cost rises from $3.46 to $5.98.

GPT-6.1 Sol, released Sept. 29 according to the source, is his second model for file-level investigation and review. Its listed high and xhigh costs are $0.32 and $0.39 per task, with index scores of 50 and 51. Meyer says those settings can take 57 to 69 seconds to produce a first token, making them less suited to interactive use. The source also assigns scoped subtasks and documents to Sonnet 5.5, routine classification to Luna, and occasional second opinions to Astra or Fable.

The account identifies Jev as a decision model that cannot write sentences. Meyer uses it for high-volume binary decisions and routing. The source provides no benchmark score, price, release date or detailed evaluation method for Jev, so its role is described as part of his workflow rather than a quantified comparison with the other models.

At a glance
reportWhen: Published Sept. 29, 2026; GPT-6.1 Sol w…
The developmentThorsten Meyer published a Sept. 29 account of a multi-model AI workflow built around Opus 5.5, newly released GPT-6.1 Sol and Jev.

Opus builds. Sol reviews. Jev decides.

The September 2026 AI stack in one page: six frontier models on one price curve, and a decision model for the high-volume judgements that do not need a sentence.
Scores: Artificial Analysis Intelligence Index v4.3.x. Data as of 29 September 2026.
BuildsClaude Opus 5.5 at high or xhigh effort
Digs and reviewsGPT-6.1 Sol at high or xhigh effort
DecidesJev on high-volume yes/no and routing calls

One price tape, six models

Put every model on the same cost-per-task ruler and capability looks compressed. The bill does not.
Price tape: cost per task of six models on a log scale, from GPT-6 Luna at $0.07 to Fable 5.1 at $7.63$0.05$0.10$0.50$1$5$10cost per task, log scale: each tick is a different order of magnitudeGPT-6 Lunaindex 37 · $0.07GPT-6.1 Solindex 51 · $0.39 (xhigh)GPT-6 Astraindex 53 · $3.26Opus 5.5index 58 · $5.98Sonnet 5.5 · index 56 · $7.60Fable 5.1 · index 53 · $7.63about 100× from the cheapest to the priciest, but only 21 index points between them

Score against cost, at every effort setting

Each dot is an effort level. Opus 5.5 at high already matches Astra and Fable at max on this index, for less money.
Intelligence Index score against cost per task for each effort setting of six models$0.01$0.10$1$102030405060cost per Intelligence Index task, log scaleindexOpus high / xhigh: my defaultOpus 5.5Sonnet 5.5Fable 5.1GPT-6 AstraGPT-6.1 Sol (new)GPT-6 Sol (Sep 22), dashedGPT-6 Lunaup and to the left is better
Astra and Fable are shown at their top published setting. Luna starts at $0.0045 per task. GPT-6.1 Sol has no low or max setting published yet.

The effort dial moves the bill more than the model

Going from medium to max on Opus costs 4.46× more for 7 points. That is why I run high or xhigh.

Claude Opus 5.5

$0.55
42
$1.34
51
$1.82
54
$3.46
56
$5.98
58
low
medium
high
xhigh
max
Solid bars are where I run it. Max adds 2 points over xhigh for 73% more cost.

Claude Sonnet 5.5

$0.41
36
$0.59
41
$1.08
47
$2.74
52
$7.60
56
low
medium
high
xhigh
max
Best value is high. At max it writes about 193k output tokens per task, the most measured.

GPT-6.1 Sol: near-Astra scores at a fraction of the price

Launched 29 September at $2 in and $10 out per 1M tokens. It sits 1 to 2 points under Astra and Fable, and Opus xhigh still leads it by 5.

Three published settings

SettingIndexCost per taskOutput tokensFirst token
medium48$0.2115M5.3 s
high50$0.3225M57 s
xhigh51$0.3936M69 s
Median for comparable models is 82M output tokens. High and xhigh are not interactive: plan for a wait before the first token.

Same score band, very different bill

GPT-6.1 Sol xhigh
$0.39index 51
Opus 5.5 high
$1.82index 54
GPT-6 Astra max
$3.26index 53
Opus 5.5 xhigh
$3.46index 56
Fable 5.1 max
$7.63index 53
Cost per Intelligence Index task. A one-point gap is inside the noise.

My stack: who builds, who reviews

Opus does the work. A second model family reviews it, because a different reviewer catches what the author cannot see.
Stack diagram: Opus 5.5 builds at high effort, escalates to xhigh, and sends every change to GPT-6.1 Sol for review; Astra or Fable give a second opinionOpus 5.5 · xhighhard problems: architecture,migrations, trust boundariesOpus 5.5 · highMAIN BUILDERfeatures, APIs, multi-filework, refactorsescalate when it gets hardGPT-6.1 Solhigh or xhighdigs into details andreviews every change$0.32–0.39 per taskdifffindingsAstra or Fablesecond opinion, 8 to 20×the cost per taskif they disagreeSonnet 5.5 · Lunaside work: scopedsubtasks, bulk checksand routingFailed review? Hand Opus the failing case and the evidence.Never just “try harder”: effort cannot supply a missing requirement.
Effort is not capability. Turning the dial up does not make a model smarter.
Effort cannot fill gaps. A missing requirement stays missing at any setting.
Different model, same spec. That is not independent review if both read the same flawed brief.
Green tests are not approval. Passing tests only prove what the tests cover.

Cheaper tokens are not cheaper work

Illustrative, not measured: $1 of model time plus 4 minutes of review at $45 an hour. Halving the model price saves 12.5% of the total. One extra minute of review erases it.
$4.00
review $3.00
model $1.00
Baseline
$3.50
review $3.00
model $0.50
Model price cut 50%
$4.25
review $3.75
model $0.50
Cheaper model plus 1 extra minute of review
Track cost per accepted result: model, tools, review and rework, divided by the results someone actually uses.

Read the numbers with four warnings

The index movesFable scored 66 on an earlier version and 53 on v4.3. Compare within one version only.
Fallback is includedFlagged cyber and biology tasks route to older Anthropic models, now on Sonnet 5.5 too.
Max is not productionReal deployments run medium or high, where gaps narrow and costs fall.
Your work decidesShadow-test on your own tasks. Budget cost per task, not per token.

Part 2: Jev, the model that decides instead of writing

Jev cannot write, summarise or extract. It answers narrow typed questions with a probability and an honest confidence, in under a second, for about $0.04 per million input tokens.

One call in, typed answers out

Your code, not Jev, decides what to do with each answer, usually by confidence band.
Jev flow: state and typed questions go into one Jev call; typed answers with confidence come out; code acts alone, escalates the gray zone, or logsStatea ticket, a story,a site profile,a log line …+ typed questions,many per callJevone call0.3 to 0.9 s$0.042 / M tokens inAnswersnoul: 0.03choice: billing p 0.91, conf 0.86score: 2.7 of 3 conf 0.64code branches on thisAct aloneconf ≥ 0.8Escalategray zone toLLM or humanLogmeasure first

Three question types

noul
A yes/no question. Returns the probability of yes, 0 to 1.
gates, flags, filters
choice
Pick one option. Returns the choice, a probability per option, and a confidence.
routing, classification, taxonomy
score
Rate on your ordered levels. Returns a position (it can fall between levels) plus a confidence.
quality, fit, severity, priority

Confidence is the superpower

In my own measurement on a 31-topic classification, Jev agreed with a frontier LLM almost every time it was sure, and rarely when it was not. So: decide the clear cases, route the gray zone.
confidence 0.8 or higher
97–99%
all answers
89%
confidence below 0.5
42%
Agreement with a frontier LLM, my production data, September 2026, rounded.

Three uses running in my publishing operation

About 90,000 decisions so far. Checks I could only afford on a sample now cover everything.
$2.01
Language check
78,889 articles scanned overnight. 1,576 in the wrong language found, 1,553 fixed in place.
22%
Relevance gate
About 10,000 story-to-site pairings judged in 3 days. Only 22% were clearly on-topic.
89%
Classifier fallback
Agreement with the primary LLM across 31 topics, used when that LLM errors.

The fit test, then the shadow test

Use Jev only when all four hold. Then prove it on past decisions before it acts on anything.
High volumeThousands of small calls, not a handful of big ones.
Narrow questionNo multi-step reasoning needed.
Cheap errorsOr unsure cases go to something smarter.
Heuristic failsVisibly, and measured, not assumed.
  1. Replay 300 to 500 past decisions
  2. Compare overall and per confidence band
  3. Read 20 disagreements, decide who was right
  4. High band at 95% or better?
  5. Own flag, off by default
  6. Canary on 5 to 10 units
  7. Roll out in the confident band only

24 use cases, sorted by how well they fit

Start from the strong fits. The amber ones need a measurement before you trust them, and the red ones fail one of the four conditions.
in productionstrong fitmeasure firstpoor fit

Proven in production

  • 1Relevance gate
  • 2Language check
  • 3Classifier fallback

Publishing and content

  • 4Thin-source detector
  • 5Same-event dedupe
  • 6Product fits roundup
  • 7Disclosure present
  • 8Headline quality
  • 9Comment moderation

Commerce and support

  • 10Support-ticket routing
  • 11Return-reason coding
  • 12Review to feature complaints
  • 13Catalogue taxonomy
  • 14Order-fraud pre-triage

Software and AI systems

  • 15LLM guardrail
  • 16RAG passage filter
  • 17Citation check
  • 18Tool and intent routing
  • 19Log-line triage
  • 20PR risk triage

Business ops and home

  • 21Inbox triage
  • 22Expense categorisation
  • 23Lead qualification
  • 24Smart-home intent

Limits, cost and one hard rule

No writing, summarising or extractionPair it with an LLM for the write step.
No world knowledgePut a snippet in the state; a bare name means nothing.
Reads your wording literallyA rewording moved my results about 2 points. Freeze it, re-measure after changes.
Weaker on non-English, maths, datesKeep those checks on an LLM. Early access, hosted API only.
100,000 decisions ≈ $2.50
About 60M input tokens at $0.042 per million, output free, roughly 600 tokens per three-question call. Latency 0.3 to 0.9 seconds.
Never the sole decision-maker for consequences about people. Hiring, credit, medical and legal outcomes stay with a human. Jev can sort and flag. A person decides.
Sources. Model scores, cost per task and speeds: Artificial Analysis, Intelligence Index v4.3.x, including the GPT-6.1 Sol medium, high and xhigh pages, checked 29 September 2026. Astra and Fable scores from the Artificial Analysis v4.3 announcement. Jev figures are my own production measurements, September 2026, rounded. The review-bill example is illustrative. Read the full article on thorstenmeyerai.com.

How the Workflow Splits Model Costs

The account illustrates a practical way to use several AI models in development: reserve a more expensive model for work that calls for building or difficult reasoning, then use a cheaper model for repeatable review and routing. Meyer’s stated rationale is that a $0.39 review task can be run routinely, while a second model family may catch issues the builder missed. That is his operating judgment, not evidence that this arrangement improves software quality in every team or project.

The figures also show why the effort setting matters to his choices. In the supplied index table, Opus at max costs more per task than at xhigh for a two-point score difference. Sonnet 5.5 at max is listed at $7.60 per task for a score of 56; Meyer notes that its xhigh setting is $2.74 for a score of 52. These are index task costs, not a promise of what an individual user will pay. Actual costs depend on the work submitted and the usage behind it.

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The Index Behind Meyer’s Choices

Meyer bases the listed scores on the Artificial Analysis Intelligence Index v4.3.x, except where otherwise noted. In his account, Opus 5.5 scores 58 at its top setting; GPT-6.1 Sol scores 51 at xhigh; Astra scores 53 at max; and Fable 5.1 scores 53. Luna scores 37. He describes six models as sitting within about 20 index points while their costs per task differ substantially. The figures and rankings here reflect the supplied Sept. 29 source and may change as benchmark listings are updated.

His accompanying comparison lists token prices as input and output rates per million tokens: Opus 5.5 at $4/$20, Fable and Astra at $10/$50, GPT-6.1 Sol at $2/$10, and Luna at $0.10/$0.50. Those rates are distinct from the source’s per-task cost estimates. Meyer also says the index is a general capability map, not a verdict on a reader’s own work, and recommends shadow-testing before switching workflows.

““which model clears my quality bar at the lowest cost per task?””

— Thorsten Meyer

What the Benchmarks Cannot Establish

The supplied material does not report results from a controlled comparison of these models on Meyer’s own projects. It does not give the prompts, task mix or calculation method behind every per-task estimate, and it supplies no comparable performance or cost data for Jev. The figures should therefore be read as the source’s account of benchmark results and Meyer’s workflow, not as independently verified predictions for other users.

Meyer says a one-point index difference is within the noise and that Artificial Analysis had not yet published low or max settings for GPT-6.1 Sol. He also reports long first-token waits at Sol’s high and xhigh settings. The account does not establish whether those measurements will hold across different tasks or change as the model and index are updated.

Test the Workflow on Real Tasks

Meyer’s next step for readers is to shadow-test models against their current workflow before switching. That means checking candidate outputs against the same quality bar and tasks used in practice. The source does not give a timetable or results from a broader test, so it remains unclear whether the proposed split will generalize beyond his own use.

For review failures, Meyer says he sends the failing case and supporting evidence back to Opus rather than simply asking it to try harder. His account also cautions that passing tests alone is not approval to ship and that different models can still share the same flawed requirements. No further release or benchmark milestone is specified.

Key Questions

Which model does Meyer use to build?

He uses Opus 5.5 at high effort for features, APIs, multi-file work and refactoring, and xhigh for harder architecture and migration tasks.

What role does GPT-6.1 Sol play?

Meyer uses GPT-6.1 Sol for detailed investigation and independent review. The supplied account lists its high and xhigh task costs at $0.32 and $0.39.

What is Jev used for?

The source describes Jev as a decision model that cannot write sentences. Meyer assigns it high-volume yes-or-no decisions and routing judgments; no benchmark or price is provided.

Do the index scores show which model is best for every task?

No. Meyer describes the Artificial Analysis index as a general capability guide and says readers should test models on their own workloads before switching.

Source: ThorstenMeyerAI.com

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