7 Best Models for US Advisor Knowledge Work (2026)

Seven models for advisor knowledge work is a packet decision, not a “who won the internet on 3 Sep 2026” decision. An RIA operations lead has to take a household file, a quarterly review, a fee invoice, and a reviewer and land a memo the CCO can find. Claude Fable 5.1, GPT-6 Astra, Claude Opus 5, Claude Fable 5, GPT-5.6 Sol, Claude Mythos 5.1, and GPT-6 Pro are the seven names on this list. Two of them are not public pickers.

Fable 5.1 Intelligence Index (max): 66 according to Artificial Analysis, 66 on Intelligence Index v4.1.1 at max, with about 4% of that eval’s output tokens routed to Opus under Anthropic’s default safety fallback. Astra is 61 on the same index. No vendor paid for inclusion.

TL;DR

• Use Claude Fable 5.1 as the default knowledge-work model when the independent Intelligence Index is the test (66 vs Astra 61) and you can pay $10 / $50 list I/O for $0.25 cache reads.

• Use GPT-6 Astra when you need the cheaper AA Intelligence $/task ($1.67 vs $3.69) or a multi-app workflow score, and you can live with staged access on 3 Sep 2026.

• Use Claude Opus 5 or GPT-5.6 Sol when the memo is short and list price is the constraint ($5 / $25 and $4 / $20).

• Do not pick Claude Mythos 5.1 or treat GPT-6 Pro as a separate lab model with its own CAI cell. Mythos is invite-only. GPT-6 Pro is the ChatGPT plan name for Astra-class access still rolling out.

Key Takeaways

• Independent Intelligence Index (max), 3 Sep 2026: Fable 5.1 66, Astra 61. Sol’s max cell is not printed as a 66-class number in this pack.

• List I/O: Fable 5.1 / Fable 5 / Astra / Mythos 5.1 at $10 / $50; Opus 5 at $5 / $25; Sol at $4 / $20 (promotional at least through 21 Nov 2026).

• Cache reads: Fable 5.1 and Mythos 5.1 $0.25; Astra and Fable 5 $1.00; Opus 5 $0.50; Sol $0.40.

• Astra is not generally on ChatGPT on 3 Sep 2026. Fable 5.1 is live on paid Claude and API.

• Orchestrate the memo, the invoice, and the hold only after unique IDs and a reviewer exist.

How we evaluated

We ranked the seven names as advisor knowledge-work engines: quarterly memos, IPS drafts, and fee packets a principal still signs. Evidence is Artificial Analysis dated 1 Sep and 3 Sep 2026, Anthropic and OpenAI list prices counted 2026-09-03, and access on 3 Sep 2026. We did not invent METR horizons. We did not treat OpenAI’s launch table as independent. We did not treat Mythos 5.1 as a public SKU.

The step-by-step build

Step 1: pick the job. A quarterly review memo is knowledge work. A tender click-path is not. If the job is GDPval-like writing, start with Fable 5.1’s 66. If the job is a short invoice note, start with Sol or Opus 5.

Step 2: wire a real event, not a paste. A worked example: Stripe emits invoice.paid when a retainer or fee invoice is paid. Stripe documents that event type in the Events API types list. On 40 paid invoices a month, the workflow copies id, amount_paid (cents), and customer onto a packet, asks Claude Fable 5.1 (list $10 / $50, Intelligence 66) or GPT-5.6 Sol (list $4 / $20) for a 2-page household note, and holds for a CFP professional. Three figures, one real Stripe token.

Step 3: put the reviewer on the packet before any client send. US Tech Automations sits on that invoice.paid step: it files the draft, attaches the invoice ID, and will not send until the named principal releases the hold. It does not replace the CRM. It does not replace the model.

Quarterly review reminders still need a clock; see quarterly portfolio review reminder automation. The memo still has to look like a proposal the client can sign; see proposal software for financial advisors. The rest of the ops stack still has to move; see financial services automation complete guide.

CFP experience requirement: 4,000 or 6,000 hours according to CFP Board, 4,000 hours on the apprenticeship pathway or 6,000 hours on the standard pathway for initial certification. That is why a model draft is not a credential. A CFP professional still owns the memo.

According to DOL, ERISA (Public Law 93-406) has governed most private-sector retirement plans since 1974. Confirm with counsel whether a given packet is ERISA-covered. The model still does not get to be the fiduciary.

According to FDIC, the standard maximum deposit insurance amount is $250,000 per depositor, per insured bank, for each account ownership category. That is a cash-balance fact for client letters, not a model score. Do not let a draft invent coverage.

Tooling landscape

Seven names, two of them restricted. Cells that this pack does not publish stay blank rather than guessed.

Source line: AA cells from Artificial Analysis 2026-09-01 / 2026-09-03; list prices from Anthropic and OpenAI cards counted 2026-09-03. Astra public flag is 0 because it is not generally on ChatGPT on 3 Sep 2026 (Trusted Access / limited orgs; Enterprise off until an admin enables it). GPT-6 Pro has no separate API rate card in this pack — it is the ChatGPT plan name for Astra-class access still rolling out. Mythos 5.1 shares Fable 5.1 list prices and is Glasswing only.

According to Claude Docs, Claude Fable 5.1 and Claude Mythos 5.1 cache hits are $0.25 per million tokens; Claude Fable 5 cache hits remain $1.00; Claude Opus 5 cache hits are $0.50.

Source line: context and output from Anthropic models overview and OpenAI Astra/Sol cards counted 2026-09-03. Sol knowledge cutoff is omitted rather than guessed. Mythos 5.1 matches Fable 5.1 specs; GPT-6 Pro has no separate spec row.

The ROI math

ROI here is coordinator hours and a file the CCO can find, not a promised AUM lift.

Source line: token dollars use public list rates. Cache row applies Fable 5.1 $0.25 to 75% of input and $10 to the rest, plus $50 output; arithmetic, not a measured invoice. Astra list I/O matches Fable 5.1; Astra cache reads are $1.00, so the warm-cache lever is weaker.

AA Intelligence $/task: $1.67 Astra vs $3.69 Fable according to Artificial Analysis, $1.67 versus $3.69 on the Intelligence cost/task (max) column dated 2026-09-03. Sol is $0.95 on that column. Do not read that as “Fable is cheaper.”

Pitfalls and red flags

Do not paste household SSNs into a consumer chat tab. Send IDs. Keep the file in the CRM and the archive.

Do not treat Mythos 5.1 as the “smarter Fable.” It is the same weights with looser cyber and life-science gates, invite-only. This list will not document those gates, payloads, or exploits.

Do not treat GPT-6 Pro as a seventh lab score. There is no independent CAI cell under that plan name in the 3 Sep 2026 pack. It is access branding for Astra-class ChatGPT seats that are still coming days, with Enterprise off until an admin enables it.

Do not mix Astra Fast mode surfaces: API docs 2× Standard, Help Center Codex/Work 2.5×. Name the surface.

Do not skip the hold. A model that emails a client without a principal is a process failure.

Red flags: invite-only twin as the production default; promotional Sol $4 / $20 treated as permanent past 21 Nov 2026; Fable 5 kept after you could take Fable 5.1’s $0.25 cache; METR hour numbers invented; ARC-AGI-3 99.9% quoted without the provider-adapter / Responses API harness (independent standard harness is 62.7%).

Who this is for

This page is for an RIA operations lead, CCO, or lead advisor at a 6–40 professional firm whose stack already includes a CRM, billing, and an archive. The firm already writes quarterly memos. The gap is the packet.

Red flags: memos in personal Claude or ChatGPT tabs; no named reviewer; archive cannot produce last quarter; Mythos requested as if it were a public dropdown. When NOT to use US Tech Automations: if the CRM already turns invoice.paid into a reviewed note, stop. If a Zapier, Make, or n8n recipe already writes the one billing field you need, keep that recipe. US Tech Automations belongs when the same paid invoice still has to become a held memo and an archive file.

Pros and cons

Claude Fable 5.1

Pros

• Independent Intelligence Index 66 (max), the knowledge-work lead on this list.

• $0.25 cache reads at $10 / $50 list I/O; public on paid Claude and API as of 1 Sep 2026.

• Anthropic positions it for long-horizon agentic work when Opus 5 at high effort still misses.

Cons

• AA $/task $3.69, not cheaper than Astra on that column.

• Forced tool_choice any/tool returns 400; thinking always on; AWS Covered Model retention unless EFS-eligible ZDR through 2026-12-31.

GPT-6 Astra

Pros

• Intelligence Index 61 (max) and AA $/task $1.67; AutomationBench 41.4% on OpenAI’s 3 Sep 2026 provider-run table.

• CAI 67 in Codex at about one-third of Sol’s tokens in the Artificial Analysis note.

• 1,050,000-token context; reasoning.effort includes xhigh and max.

Cons

• Not generally on ChatGPT on 3 Sep 2026; Enterprise off until an admin enables it.

• Cache reads $1.00 versus $0.25 on Fable 5.1.

Claude Opus 5

Pros

• $5 / $25 list I/O; Anthropic’s published starting model for most workloads.

• 1M context, public API, no Trusted Access wait.

Cons

• Cache reads $0.50, double Fable 5.1.

• No Intelligence Index max cell in the 3 Sep 2026 pack used here; do not invent one.

Claude Fable 5

Pros

• Same $10 / $50 list I/O as Fable 5.1; already in production for teams that have not migrated.

• Public API; 1M context.

Cons

• Cache reads still $1.00 — the 75% cache cut is the 5.1 reason to move.

• Earlier models cannot read Fable 5.1 thinking blocks if you mix generations mid-memo.

GPT-5.6 Sol

Pros

• $4 / $20 list I/O (promotional at least through 21 Nov 2026) and AA $/task $0.95.

• Generally available; 1,050,000-token context.

Cons

• AutomationBench 18.1% on OpenAI’s provider-run table.

• Promotional price is dated; re-quote after 21 Nov 2026.

Claude Mythos 5.1

Pros

• Same list I/O and $0.25 cache as Fable 5.1; same weights.

Cons

• Glasswing / trusted-access only. Not a public picker.

• Looser cyber and life-science gates are not a feature this page will teach. Do not use it as a dropdown SKU.

GPT-6 Pro

Pros

• ChatGPT plan branding for Astra-class access as Plus/Pro/Business/Enterprise seats roll out over coming days from 3 Sep 2026.

Cons

• No separate independent CAI or Intelligence cell under this plan name in the pack.

• Enterprise remains off until an admin enables Astra. Not an API ID you can paste today as a distinct model.

FAQs

Which of the seven should draft a quarterly household memo?

Claude Fable 5.1 if the independent Intelligence Index is the test and the file is long. GPT-6 Astra if you have access and you care about AA $/task $1.67. Opus 5 or Sol if the note is short and list price is the constraint. Mythos 5.1 and GPT-6 Pro are not public lab winners on this list.

Does Fable 5.1 cost less than Astra for knowledge work?

Not on AA Intelligence $/task ($3.69 vs $1.67) and not on list I/O (both $10 / $50). Fable 5.1 can cost less on a warm cache because reads are $0.25 versus Astra’s $1.00. Measure last month’s packet sizes.

Should household identifiers go in the prompt?

No. Send invoice IDs, amounts, and reason codes. Keep the household file in the CRM. A model draft is not the archive. Confirm AWS Covered Model retention if you use Fable 5.1 on Bedrock.

How do you handle Mythos 5.1 or GPT-6 Pro on a procurement form?

List them as restricted or rolling-out access names, not as scored alternatives. Mythos is invite-only. GPT-6 Pro is a ChatGPT plan label, not a second API with its own CAI. Do not invent scores for either.

When is US Tech Automations the wrong buy on this shortlist?

When the CRM already turns a paid invoice into a reviewed note, or when a Zapier, Make, or n8n recipe already writes the one field you need. US Tech Automations is for the packet that still has to draft, hold, and archive across systems.

Can you quote ARC-AGI-3 99.9% as the knowledge-work score?

No. That 99.9% is OpenAI’s provider adapter / Responses API harness. The ARC Prize standard harness is 62.7% at max. Neither number is an advisor-memo score. Use Intelligence Index 66 vs 61 for this job.

If the CRM already turns a paid invoice into a reviewed note, you are done. If the same packet still has to draft, hold, and archive, map that hold on agentic workflows. For the company homepage, see US Tech Automations.