Search for the best AI consulting firms and you will find a dozen pages that agree on one thing: the company that wrote the page is number one. We checked the top fifteen results for that query and its sibling, best AI development companies, on 23 August 2026. Ten were lists written by a vendor that placed itself first or second. One vendor put itself ninth and said so, which makes it the most honest page in the set. Two were promotional posts for a single firm. The remaining two were directories that earn fees from placement. Some of the lists publish a scoring rubric, one requires a minimum headcount that quietly excludes everyone smaller than the author, and none of them link to evidence. There is no editorial layer in this category. Nobody is checking the claims.
We are a vendor as well. So this piece takes a different approach. It names real firms, including firms we compete with. It scores nothing on a secret formula. It judges each firm on six criteria that a buyer can verify from the outside in an afternoon, it links every fact to where we found it, and it puts Vindler in the same table with the same honesty, including the places where another firm is the better call. If a firm named here thinks a fact is wrong, the corrections address is at the end and we will fix it and say so.
Why the usual lists fail you
The problem with the existing lists is not that the authors are dishonest. It is that the inclusion criteria measure the wrong things. One widely cited list scores firms on a hundred-point algorithm built from third-party review platforms, published case studies and analyst benchmarks, and it assigns twenty of those points to team seniority and delivery model, which is precisely the thing a scraper cannot see. Another requires two hundred and fifty technology professionals and a decade of history before a firm is eligible at all, which is a description of the author, not of good AI work. Headcount is easy to count, and it correlates with recall (an assistant asked to name AI consultancies will name the largest ones first), but it does not correlate with whether your retrieval pipeline will still be accurate in month four.
There is a second problem. For most AI products today the hard part is not the model. It is data plumbing, evaluation, and deciding what the system should refuse to do. Any firm can produce a demo in two weeks. The lists reward the demo, because the demo is what shows up in a case study video. What you need to know is whether the firm can tell you, in numbers, when the output is good enough to ship, and whether they have ever killed an approach that was not working. Those things leave traces in public, if you know where to look.
Six criteria you can check from the outside
Each of these can be verified without a sales call, from the firm's website, its review profiles, and its public code. Together they predict outcomes far better than headcount or a logo wall.
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Named production work with numbers. Not "a leading fintech". A named client, a system that real users touch, and a figure that could be wrong. Firms that can name clients do, because it is the strongest thing they own. Firms that cannot describe verticals instead. Anonymised case studies are not a red flag on their own (NDAs are real, and we carry several ourselves), but a firm with zero named references after years of trading is telling you something.
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Evidence of an evaluation practice. Does the firm write about evals, golden test sets, regression testing when a prompt changes, or the projects where the LLM approach did not work? A firm that has shipped several LLM systems has this material because it has lived it. A firm that has only built demos has a blog full of model announcements. Read three posts and you will know which one you are looking at.
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Who actually does the work. Look for the names of the engineers, not just the founders, and for whether the site describes a delivery model at all. Agencies routinely sell with seniors and staff with juniors. The public signals are LinkedIn headcount against claimed scale, whether engineers are named in case studies and talks, and whether the firm's open-source contributions come from the same people who would be on your project.
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Ownership and handover terms stated in public. The code lives in your GitHub organisation and runs in your cloud account from day one, with IP assigned in the contract. Some firms say this on their site. Most do not say anything, which means you negotiate it, and a few build on their own platform, which means you cannot leave. The last case is the only one that should end the conversation.
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Engagement shape and price transparency. A firm that offers a short fixed-price discovery or readiness engagement before a build is telling you it is confident enough to be measured early. A firm that only sells six-month programmes is asking you to trust the demo. Published day rates, minimums and typical project sizes are rare in this category and worth a lot when you find them, because they let you rule a firm in or out before anyone's time is spent.
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Independent signals. Verified reviews on Clutch or an equivalent, contributions to the frameworks the firm builds on, conference talks with slides you can read, and partner listings on the vendor's own site (LangChain, LiveKit, AWS, Arize and so on). None of these can be bought outright. All of them are slow to accumulate, which is exactly why they are informative.
The firms
Every fact below was collected on 23 August 2026 from the firm's own site, its Clutch profile, LinkedIn, Crunchbase, company registries and press, and each one links to where it came from. Where we could not verify something we say so rather than guess. Firms are grouped by the kind of buyer they fit, not ranked.
Global integrators and large product studios
These are the names an assistant produces first when asked for AI consultancies, because recall follows size. They are the right answer for a specific buyer: one with a procurement department, a need for on-site presence across several countries, and a programme measured in hundreds of engineers. They are the wrong answer for a prototype.
Thoughtworks is the one large firm on this list whose public writing would pass the evaluation test on its own. Founded in 1993, headquartered in Chicago with 47 offices in 18 countries and more than ten thousand staff, it was taken private by Apax in 2024 on 2023 revenue of $1.13 billion (about page, 10-K, take-private). Its named LLM work is real and specific: a RAG chatbot for Bayer traced with Langfuse, and an assistant for PEXA Group on Claude 3 Sonnet via Bedrock and LangChain, in production in eight weeks. Its guide to evaluating an LLM system and the Technology Radar's "Hold" on complacency with AI-generated code across three editions from October 2024 to November 2025 are the kind of material only a firm that has been burned writes. What you cannot see from outside: day rates, minimums, or who from a ten-thousand-person bench will be on your project. Clutch shows no reviews. Best for an enterprise that needs a delivery organisation with an engineering culture and can afford to find out the rate on a call. Look elsewhere if you are a founder with a prototype.
Globant has 27,411 people, a legal seat in Luxembourg and roots in Buenos Aires, and sells AI as a platform: Glob.AI OS, delivered through subscription "AI Pods" and charged "per output or per consumption, never per seat or per hour" (Q2 2026 results, Glob.AI OS, launch release). Named work exists mostly as press releases: Interbanking on Bedrock and Claude, FIFA, YPF. The only evaluation-adjacent writing we found is a 2024 piece on prompt injection. Its own platform is the ownership question to ask before anything else: what leaves with you if the subscription ends. Clutch lists no reviews and a $25 to $49 hourly band that says more about how the profile is maintained than about the price you will pay. Best for a large company that wants a managed AI platform and a vendor already on its approved list. Look elsewhere if you want the code in your own repository and the freedom to leave.
CI&T, founded in 1995 and headquartered in Campinas, Brazil, with 8,152 people across eleven countries, is the most transparent of the large firms about its commercial model: 30% of new engagements in the first half of 2026 were value-based, it fields Forward Deployed Engineers, and its Clutch profile states a $100,000 minimum and a $50 to $99 hourly band (Q2 2026, earnings call, Clutch). It also has the only meaningful review count in this tier, 4.7 across seven reviews, though all of them date from 2021 or earlier. Named LLM work: B3 and Sami Saúde; its Ford case is AI work of an earlier kind. Delivery runs through its own FLOW platform, so the same ownership question applies as with Globant. Evaluation writing is thin, one 2024 article on hallucinations. Best for an enterprise that wants a Brazil-anchored delivery organisation at scale with a US and European front office. Look elsewhere below $100,000.
Slalom Build is the product-studio arm of Slalom, with 1,400 builders in seventeen cities and strong hyperscaler partnerships, AWS Partner of the Year nine times (press kit, partners). It is the safest large-firm choice on process. It is also the weakest on the two criteria that matter most here: its named case studies (Hologic, Swimming Australia, Kawasaki) are classical ML and pre-LLM, and its generative AI writing stops at "humans are relied on to double check the output" (source). No rates are published; the parent's Clutch profile lists a $1,000,000 minimum. Best for a company that needs design and engineering together under one enterprise contract and will bring its own evaluation discipline. Look elsewhere if you are buying LLM expertise specifically.
Specialist boutiques in the United States and the United Kingdom
This is the tier the lists skip, because the firms are too small to be in the scraped corpora and too busy to write listicles. It is also where the strongest evaluation writing in this whole exercise lives.
Stride (New York and Chicago, founded 2014, roughly 77 people) describes itself as an AI engineering consultancy and Claude partner, and its case studies are the most technically specific of any firm here. The Avila Science build names LangGraph, Claude Sonnet, a LangSmith evaluation suite and a GPT-4 judge; 73V documents model routing between Claude Haiku and Sonnet with a projected $360,000 saving; One Health Link runs LangGraph on Azure OpenAI. Its entry offer is a two-week strategic assessment, and its Clutch profile states a $100,000 minimum at $150 to $199 per hour with a 4.5 rating across four reviews (Stride Consulting on Clutch). Best for a funded company that wants an embedded team on the LangGraph and Claude stack with knowledge transfer built in. Look elsewhere below $100,000.
Fuzzy Labs (Manchester, founded 2019, about thirty people) has the best first-party evaluation writing of any boutique we reviewed. Evaluating Large Language Models opens with the position that evaluation "should be the starting point for any LLM-based system", and Measuring Agent Effectiveness and the guardrails tooling comparison follow through. Named LLM work: a case-file assistant for South Yorkshire Police running inside the force's own Azure tenancy, with two further LLM cases anonymised. The stack is MLOps-native (ZenML, Seldon, MLflow, Kubernetes, an open-source Azure tool called Matcha). No rates are published and there is no Clutch profile. Best for a UK organisation with data residency constraints that wants the system run in its own tenancy by people who will explain their evals. Look elsewhere if you need a US presence or want to see a rate before the first call.
Applied Data Science Partners (London and Irving, Texas, founded 2016, around twenty-two people) positions itself around agents and publishes the clearest tiering of any boutique: readiness and strategy, prototyping, then a system build, with a Clutch profile stating a $25,000 minimum at $150 to $199 per hour (ADSP on Clutch). Named work includes an LLM text-to-CAD system with retrieval and self-evaluation for the European Space Agency and a fifteen-agent deployment at Barton Peveril College; the text-to-SQL agent at 91% accuracy is anonymised. Evaluation appears inside the cases rather than in standalone writing, and the generative AI services page still references GPT-4 and DALL-E 2, which is worth asking about. ISO 9001 and 27001 and a G-Cloud listing make it procurement-friendly. Best for a UK public-sector or regulated buyer with a $25,000 to $100,000 first project. Look elsewhere if you want a firm whose blog shows its evaluation method.
Datasparq (London, incorporated 2018, about sixty people) is the one boutique with a public rate card: its G-Cloud 15 listing for generative AI and LLM solutions publishes £720 to £2,465 per day by role (G-Cloud 15 listing). Named LLM work is specific: the Encore quoting system on LangChain Deep Agents and Google Cloud, with human-in-the-loop review and a stated 20% uplift against unquoted revenue; easyJet and GXO are classical ML. Its evaluation writing is candid: RAG won't solve all of your problems yet cites hallucination rates of 17 to 33% for proprietary systems with retrieval. Engagements run as a four-week strategy phase then sixteen-week builds. No Clutch profile. Best for a Google Cloud shop in the UK that wants published day rates and a data team alongside the LLM work. Look elsewhere if your build is on AWS or you need it in weeks rather than a quarter.
Prolego (fully remote, US, founded 2017, four people) is the smallest firm here and the only one that publishes fixed prices: $80,000 per release of what it calls a Performance Evaluation Framework, $240,000 for a typical three-release solution, $250,000 for an organisational AI strategy, and a free two-hour assessment (services). The whole method is built around evaluation, which is the right instinct, and founder Kevin Dewalt's writing on LLM evaluation frameworks and a RAG study comparing open-weight models to GPT-4 are substantive. Two things to weigh: there are no named case studies, only a logo wall (Lockheed Martin, Citi, FINRA, Morgan Stanley), and at four people the key-person risk is total. There is no Clutch profile; the one under that name belongs to an unrelated Polish company. Best for an enterprise that wants an evaluation-first advisor with published prices and will staff the build itself. Look elsewhere if you need a team that can also ship and run the system.
Winder.AI (London, with its registered office in Harrogate, founded 2013, two to nine people on Clutch) was named by an assistant in our own test and could not be verified in August; it can be now. It is one of the few firms anywhere that publishes rates, £175 to £300 per hour for AI product development with example budgets (pricing), and its evaluation writing is strong, most recently a guide to testing AI agents. Its named generative work is Stable Audio for Stability AI, which is an audio diffusion product, and we found no named client on a production LLM system. Clutch shows a $25,000 minimum and one review from 2021 (Winder.AI on Clutch). Best for a buyer who wants evaluation expertise and a price before the first call. Pixelfield, the other firm from that test, has published AI pricing but no named AI work, and its ten Clutch reviews are all web and mobile projects, so it stays out. Fractional AI, the San Francisco firm behind the widely cited Zapier evaluation case study, is no longer an independent boutique: its site now reads "Fractional AI is now Ode with Anthropic" following its acquisition by the enterprise AI services firm that Anthropic, Blackstone and Hellman & Friedman launched in May 2026 (SiliconANGLE, Hellman & Friedman). The Zapier case remains the best public example of what an evaluation engagement looks like written up, and it is worth reading whoever you hire.
Nearshore specialists
If you are weighing a Latin American partner on rate and time zone, our guide to nearshore software development in Brazil covers 2026 rates, contracting routes and engagement models before you get to individual firms.
Tryolabs (Montevideo, founded 2010, about a hundred people by third-party estimates, with a San Francisco presence) was acquired by Qubika on 12 August 2026 (announcement), which makes the combined entity roughly 1,100 people and moves it out of the boutique bracket. Its evaluation writing is among the best on this list and the most willing to say no: Why LLMs struggle with your spreadsheet data tells you plainly not to start with an LLM for tabular prediction, and LLMOps unpacked is honest about operations. Named clients (MercadoLibre, Allianz Global Investors, Halliburton) are classical ML rather than LLM builds. Engagement runs from a readiness assessment through pilots and Forward Deployed Engineers; Clutch lists $100 to $149 per hour and no reviews. Best for a US company that wants a deep ML research bench in a compatible time zone and does not mind a recently acquired vendor. Look elsewhere if you specifically want LLM production references, or want to know who owns the firm next year.
Where Vindler fits
We are small: founder-led, one to ten people on any given engagement, assembled from a network of senior engineers with at least ten years of software experience, and every engagement has the founder on it. That is a strength for a prototype or a first production system and a weakness for a fifty-person programme with a procurement department, and you should read the rest of this section with that in mind.
On the first criterion we are honest about the gap. Seven of our nine published case studies are anonymised by vertical. The Voodoo game feature pipeline is named on the site, and on Clutch Typeform's Director of AI Engineering reviewed our work on their multi-agent platform; all five of our Clutch reviews are verified and public. We publish numbers in every case study and every one of them could be wrong, which is the point of publishing them.
On evaluation we can point to the writing rather than describe it: agent evaluation at scale, why an agent dashboard lies, the silence-hallucination gate we shipped on a healthcare voice device, and what breaks first on Bedrock AgentCore in production. Those are the posts an engineer reads before a call with us, and they are the reason most of our inbound arrives already knowing what we will say about evals.
On stack and sector: our main LangGraph system in production is a supervisor-worker assistant for an enterprise form-building platform, orchestrated with LangGraph on AWS Bedrock AgentCore, with six specialised agents, more than ninety backend tools over MCP, and an Arize evaluation pipeline that runs in CI (case study). In healthcare, our voice assistant for Medicare patients runs in production on bedside tablets, built on LiveKit Agents, with a 32-scenario conversational eval suite that grades empathy and clarity (case study).
On who does the work: the founder writes code on every engagement, the engineers are named to the client before the contract, and our contributions to LangChain and Hugging Face Diffusers are under the same names. On ownership: your repository and your cloud account from the first commit, in the contract, with a handover document as a named deliverable. On engagement shape: a one-week, fixed-price Production Readiness Review at $4,500, then projects from $25,000. On independent signals: 5.0 on Clutch across five reviews, AWS Partner Network membership, and open-source contributions to LangChain and Hugging Face Diffusers. We are headquartered in São Paulo and work with clients in the United States and Europe.
Where to go instead: if you need a hundred engineers, on-site presence in three countries, or a vendor already in your procurement system, one of the integrators above. If you need deep classical ML rather than LLM systems, one of the boutiques with a research bench. If you need one contractor for a well-defined task, a marketplace, which we compared in a separate piece.
The comparison table
Same criteria, one row per firm, so you can rule firms in or out before reading the profiles. "Named LLM work" means at least one named client on a production LLM system, not classical ML. "Evaluation writing" means first-party material on evals, failure modes or when not to use an LLM. Prices are what the firm or its Clutch profile states publicly, nothing inferred.
| Firm | Base | Size | Named LLM work | Evaluation writing | Entry offer and public price | Verified reviews |
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| Thoughtworks | Chicago, 47 offices | 10,000+ | Yes (Bayer, PEXA) | Strong | Not published | None on Clutch |
| Globant | Luxembourg / Buenos Aires | 27,411 | Yes, via press (Interbanking, FIFA) | Thin | Subscription AI Pods; per-output pricing | None on Clutch |
| CI&T | Campinas, 11 countries | 8,152 | Yes (B3, Sami) | Thin | $100K minimum, $50 to $99/hr | 4.7, 7 reviews |
| Slalom Build | Seattle (parent HQ), 17 cities | 1,400 | No (classical ML only) | None | Not published; parent $1M minimum | None |
| Stride | New York, Chicago | ~77 | Yes (Avila, 73V, One Health Link) | Good | 2-week assessment; $100K minimum, $150 to $199/hr | 4.5, 4 reviews |
| Fuzzy Labs | Manchester | ~30 | Yes (South Yorkshire Police) | Strongest of the boutiques | Discover phase; rates not published | No profile |
| ADSP | London, Irving TX | ~22 | Yes (ESA, Barton Peveril) | Inside cases only | Readiness tier; $25K minimum, $150 to $199/hr | Profile, 0 reviews |
| Datasparq | London | ~60 | Yes (Encore) | Good | 4-week strategy; £720 to £2,465/day published | No profile |
| Prolego | Remote, US | 4 | No (logo wall only) | Strong | Free 2-hour assessment; $80K per release published | No profile |
| Winder.AI | London | 2 to 9 | No (Stable Audio is generative, not LLM) | Strong | £175 to £300/hr published; $25K minimum on Clutch | 4.5, 1 review |
| Tryolabs (Qubika) | Montevideo, SF | ~100 (1,100 combined) | No (classical ML) | Strong | Readiness assessment; $100 to $149/hr | None on Clutch |
| Vindler | São Paulo | 1 to 10 | Yes (Voodoo on site, Typeform on Clutch); other cases anonymised | Good | 1-week review, $4,500; $25K minimum | 5.0, 5 reviews |
Which firms fit a custom LLM solution
When a company asks for a custom LLM, the model itself is almost always rented from OpenAI, Anthropic, Google or a cloud provider, and the custom part is everything built around it. The kinds of work below run from the cheapest to own to the most expensive, and the firms above are stronger on some than on others.
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Retrieval over your own data (RAG). The model answers from your documents and databases, fetched at question time. Most internal assistants and support tools are this. Thoughtworks' chatbot for Bayer and ADSP's text-to-CAD system for the European Space Agency are retrieval builds, and Datasparq's Encore agent retrieves past quotes to use as worked examples.
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Agents that act in your systems. The model calls your APIs through tools, with a person approving anything that cannot be undone. Stride's build for 73V answers about 85 to 87% of patient questions with a small Claude model and escalates the rest to a larger one, and staff review each reply before it is sent. Our assistant for a form-building platform is the same kind of work, with six agents and more than ninety tools.
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A model inside your own environment. This is the choice when data cannot leave your network or cloud tenancy. Fuzzy Labs' assistant for South Yorkshire Police runs entirely inside the force's Microsoft Azure tenancy on a small OpenAI model, with open-source tooling around it so the model can be changed later. On open-weight models, Prolego's 2024 study reports that Mistral 7B, a small open model, performed as well as GPT-4 on a retrieval task once it was given the right context. Prolego notes that it was one application and 25 test questions.
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A model trained further on your examples (fine-tuning). It pays on a narrow, high-volume task, where a small tuned model can cost less and answer faster than a large general one. Winder.AI sells it by name, "fine-tuning on open-source base models (Llama, Mistral, Qwen)" (LLM services), and its guide to RAG and fine-tuning says most applications are "RAG first", with fine-tuning as a later optimisation. That matches our experience.
Whichever kind you are buying, ask to see the evaluation set before the architecture. A firm that proposes fine-tuning without first measuring what retrieval and better prompts achieve on your own cases is starting with the most expensive option. How we scope this work is on our custom LLM development page.
How to run the evaluation in a week
Take the three firms that survive the table and ask each the same four questions on a thirty-minute call. How will you know if the output is good, and what does your test set look like on a project like mine. Show me a project where the LLM approach did not work and what you did next. Can I meet the engineers who would be assigned, before I sign. Whose GitHub organisation and cloud account does this live in from day one. The answers separate teams that have shipped from teams that have demoed, and we wrote a longer guide on interviewing a technical partner when you are not technical if you want the full version.
Then buy the smallest thing each firm sells. A discovery sprint or readiness review, two to four weeks, fixed price, ending in a working artefact in your own repository and a realistic estimate for the rest. It costs a fraction of a build and it is the only evaluation that measures the thing you are actually buying.
Common questions about custom LLM solutions
Which AI consulting companies build custom LLM solutions? For retrieval over private data and for agents, Thoughtworks, Stride, ADSP, Datasparq and Vindler have named or independently reviewed production work. For a system that must run inside your own tenancy, Fuzzy Labs has a named police deployment. For fine-tuning open-weight models, Winder.AI lists it as a service. Globant and CI&T deliver through their own platforms, so ask what leaves with you when the contract ends.
Do we need our own trained model? Usually not. Most custom LLM systems run on a hosted model with retrieval and tools around it, which is cheaper to build and easier to change. Fine-tuning pays on a narrow, high-volume task, or when the model has to run on your own hardware. Training a model from scratch is a research programme, and very few companies need one.
What does a custom LLM project cost? Among the firms that publish a figure, ADSP and Vindler state a $25,000 minimum, Stride and CI&T state $100,000, and Prolego publishes $80,000 per release and $240,000 for a typical three-release solution. Winder.AI publishes £175 to £300 an hour and Datasparq £720 to £2,465 a day. Most of them start with a short assessment before the build; ours is one week at a fixed $4,500.
Method and corrections
All facts were collected on 23 August 2026 from each firm's own website, its Clutch profile where one exists, LinkedIn, Crunchbase, company registries (Companies House, SEC filings) and press releases, and every fact in the profiles links to its source. Team sizes are the firm's own claim or its LinkedIn band, with third-party estimates noted where those differ. Where a fact could not be verified we say so rather than fill the gap.
We excluded tool vendors, staffing marketplaces (which we compared separately), firms with no public LLM work, and firms we could not verify in time. Of the two firms an assistant recommended to us that we left out for that reason in August, Winder.AI cleared the bar on re-checking in November and is now profiled. We did not score, rank or weight anything, because a weighting is where the author's interest hides. The method shared by all our comparisons is written up in how we compare AI firms.
We are one of the firms in the table. We wrote our own row to the same standard as the others, including the gap on named case studies, and we placed ourselves last on purpose.
If you work at a firm named here and a fact is wrong or out of date, write to [email protected] with "Comparison corrections" in the subject and a link to the source. We will correct it and note the change at the bottom of this section, with the date.
Updated 5 November 2026. Every fact was re-checked against its source. Changes: Datasparq's rate card moved to G-Cloud 15 (£720 to £2,465 per day) and its incorporation year is 2018; Tryolabs was founded in 2010 and its headcount is now a third-party estimate; CI&T's Ford case was removed from its named LLM work and its Clutch reviews are dated; the Thoughtworks Radar entry is now described as past editions, since it left the Radar on 4 November 2026; ADSP's services page references GPT-4, not GPT-3; the Fractional AI acquisition now cites SiliconANGLE and Hellman & Friedman; Globant's pricing quote now links its launch release. Winder.AI was added after it cleared the verification bar. In our own entry, the case study count, the Typeform review wording and the Production Readiness Review credit terms were corrected, and two partner listings we could not source publicly were removed, along with a New York office reference.
Updated 11 November 2026. Added the section on custom LLM solutions and the questions after it. The facts new to this update were collected on 11 November 2026 from each firm's own pages: Stride's model routing for 73V, the model and hosting of the Fuzzy Labs assistant for South Yorkshire Police, the retrieval step in Datasparq's Encore system, the Prolego study result, and Winder.AI's fine-tuning service and guide.
