# Best AI Development Agencies for Retainer Work

> 44 agencies. Top-ranked: Square Root Solutions, Storm Technology, Lexunit.

Canonical page: https://www.aiagencies.eu/services/ai-development/for/retainer
Generated: 2026-09-28 · Curated by Gabor Kiss · No paid placements — inclusion, score, and rank are never sold.

## Ranked roster
Top 30 of 44 agencies on this page.

1. **Square Root Solutions** — Dublin, Ireland · €20-40/hr (directory-listed) · team 10-49 · founded 2018 · services: AI Development, Generative AI · 10 documented client engagements with source URLs · reviewed 2026-09-16 · https://www.aiagencies.eu/agency/square-root-solutions
2. **Storm Technology** — Dublin, Ireland · rate not published · team 50-249 · founded 1995 · services: AI Consulting, Generative AI, AI Development · 8 documented client engagements with source URLs · reviewed 2026-09-03 · https://www.aiagencies.eu/agency/storm-technology
3. **Lexunit** — Budapest, Hungary · €45-85/hr (directory-listed) · team 10-49 · founded 2017 · services: AI Development, AI Automation, AI Consulting · 9 documented client engagements with source URLs · reviewed 2026-09-03 · https://www.aiagencies.eu/agency/lexunit
4. **ontolux** — Berlin, Germany · rate not published · team 10-49 · services: AI Development, AI Consulting, Generative AI · 11 documented client engagements with source URLs · reviewed 2026-09-24 · https://www.aiagencies.eu/agency/ontolux
5. **Cloud District** — Madrid, Spain · €45-85/hr (directory-listed) · team 50-249 · founded 2010 · services: AI Development, AI Consulting · 11 documented client engagements with source URLs · reviewed 2026-09-20 · https://www.aiagencies.eu/agency/cloud-district
6. **Hiflylabs** — Budapest, Hungary · rate not published · team 250+ · founded 2015 · services: AI Consulting, AI Development, AI Automation · 8 documented client engagements with source URLs · reviewed 2026-09-03 · https://www.aiagencies.eu/agency/hiflylabs
7. **HolistiCRM** — Budapest, Hungary · €20-40/hr (directory-listed) · team 2-9 · founded 2014 · services: AI Automation, AI Consulting, AI Development · 7 documented client engagements with source URLs · reviewed 2026-09-09 · https://www.aiagencies.eu/agency/holisticrm
8. **Hybrid Heroes** — Berlin, Germany · €85-130/hr (directory-listed) · team 10-49 · founded 2015 · services: AI Consulting, AI Development, Generative AI, AI Agents · 7 documented client engagements with source URLs · reviewed 2026-08-05 · https://www.aiagencies.eu/agency/hybrid-heroes
9. **QED Software** — Warsaw, Poland · €85-130/hr (directory-listed) · team 10-49 · founded 1999 · services: AI Consulting, AI Development, Generative AI · 7 documented client engagements with source URLs · reviewed 2026-09-23 · https://www.aiagencies.eu/agency/qed-software
10. **Version 1** — Dublin, Ireland · rate not published · team 250+ · founded 1996 · services: AI Consulting, AI Development, Generative AI · 6 documented client engagements with source URLs · reviewed 2026-09-03 · https://www.aiagencies.eu/agency/version-1
11. **Bismart** — Barcelona, Spain · rate not published · team 50-249 · founded 2009 · services: AI Consulting, AI Development, Generative AI · 6 documented client engagements with source URLs · reviewed 2026-09-07 · https://www.aiagencies.eu/agency/bismart
12. **Siili Solutions** — Helsinki, Finland · €45-85/hr (directory-listed) · team 250+ · founded 2005 · services: AI Consulting, AI Development, AI Automation · 5 documented client engagements with source URLs · reviewed 2026-09-07 · https://www.aiagencies.eu/agency/siili-solutions
13. **Adnovum** — Zurich, Switzerland · rate not published · team 250+ · founded 1988 · services: AI Development, AI Consulting, Generative AI · 5 documented client engagements with source URLs · reviewed 2026-08-07 · https://www.aiagencies.eu/agency/adnovum
14. **Atomic Actions** — Warsaw, Poland · €45-85/hr (directory-listed) · team 10-49 · founded 2024 · services: AI Automation, AI Consulting, AI Development · 5 documented client engagements with source URLs · reviewed 2026-09-23 · https://www.aiagencies.eu/agency/atomic-actions
15. **Pexon Consulting** — Munich, Germany · €130-175/hr (directory-listed) · team 50-249 · founded 2019 · services: AI Consulting, AI Development, AI Automation · 6 documented client engagements with source URLs · reviewed 2026-09-20 · https://www.aiagencies.eu/agency/pexon-consulting
16. **Plain Concepts** — Madrid, Spain · €85-130/hr (directory-listed) · team 250+ · founded 2006 · services: AI Consulting, AI Development, Generative AI · 4 documented client engagements with source URLs · reviewed 2026-09-07 · https://www.aiagencies.eu/agency/plain-concepts
17. **Spanish Point Technologies** — Dublin, Ireland · rate not published · team 50-249 · founded 2005 · services: AI Development, AI Consulting · 4 documented client engagements with source URLs · reviewed 2026-09-16 · https://www.aiagencies.eu/agency/spanish-point-technologies
18. **Squirro** — Zurich, Switzerland · rate not published · team 50-249 · founded 2012 · services: Generative AI, AI Development · 6 documented client engagements with source URLs · reviewed 2026-08-07 · https://www.aiagencies.eu/agency/squirro
19. **Imobisoft** — London, United Kingdom · €45-85/hr (directory-listed) · team 10-49 · founded 2009 · services: AI Consulting, AI Development, Generative AI · 4 documented client engagements with source URLs · reviewed 2026-09-04 · https://www.aiagencies.eu/agency/imobisoft
20. **Contiamo** — Berlin, Germany · rate not published · team 10-49 · founded 2012 · services: AI Consulting, AI Development, Generative AI · 6 documented client engagements with source URLs · reviewed 2026-09-24 · https://www.aiagencies.eu/agency/contiamo
21. **TEKenable** — Dublin, Ireland · rate not published · team 50-249 · founded 2002 · services: AI Consulting, Generative AI, AI Development · 4 documented client engagements with source URLs · reviewed 2026-09-07 · https://www.aiagencies.eu/agency/tekenable
22. **Idiro Analytics** — Dublin, Ireland · rate not published · team 10-49 · founded 2003 · services: AI Consulting, AI Development · 4 documented client engagements with source URLs · reviewed 2026-09-16 · https://www.aiagencies.eu/agency/idiro-analytics
23. **Faculty** — London, United Kingdom · rate not published · founded 2014 · services: AI Consulting, AI Development, AI Automation, AI Agents · 3 documented client engagements with source URLs · reviewed 2026-08-04 · https://www.aiagencies.eu/agency/faculty-ai
24. **Flobotics** — Warsaw, Poland · €85-130/hr (directory-listed) · team 10-49 · founded 2019 · services: AI Automation, AI Agents, AI Development · 3 documented client engagements with source URLs · reviewed 2026-09-07 · https://www.aiagencies.eu/agency/flobotics
25. **Xomnia** — Amsterdam, Netherlands · rate not published · team 50-249 · founded 2013 · services: AI Consulting, AI Development, Generative AI · 3 documented client engagements with source URLs · reviewed 2026-08-04 · https://www.aiagencies.eu/agency/xomnia
26. **Sngular** — Madrid, Spain · rate not published · team 1000+ · founded 2014 · services: AI Development, AI Consulting · 3 documented client engagements with source URLs · reviewed 2026-09-20 · https://www.aiagencies.eu/agency/sngular
27. **Boldare** — Amsterdam, Netherlands · €45-85/hr (directory-listed) · team 50-249 · founded 2004 · services: AI Development, Generative AI, AI Consulting · 5 documented client engagements with source URLs · reviewed 2026-09-24 · https://www.aiagencies.eu/agency/boldare
28. **Neuron Solutions** — Budapest, Hungary · €85-130/hr (directory-listed) · team 10-49 · founded 2018 · services: AI Consulting, AI Development, AI Automation · 3 documented client engagements with source URLs · reviewed 2026-09-09 · https://www.aiagencies.eu/agency/neuron-solutions
29. **wegewerk** — Berlin, Germany · rate not published · services: AI Consulting, AI Development, Generative AI · 3 documented client engagements with source URLs · reviewed 2026-08-05 · https://www.aiagencies.eu/agency/wegewerk
30. **Birds on Mars** — Berlin, Germany · rate not published · founded 2017 · services: AI Consulting, AI Development · 3 documented client engagements with source URLs · reviewed 2026-08-04 · https://www.aiagencies.eu/agency/birds-on-mars

## Compared head-to-head
Curated comparison pages (published rates, team size, coverage, projected 12-week engagement cost, and the curator's verdict on both sides — pairings are never sold):
- Faculty vs Hiflylabs: https://www.aiagencies.eu/compare/faculty-ai-vs-hiflylabs
- Hiflylabs vs HolistiCRM: https://www.aiagencies.eu/compare/hiflylabs-vs-holisticrm
- Spanish Point Technologies vs Square Root Solutions: https://www.aiagencies.eu/compare/spanish-point-technologies-vs-square-root-solutions

## About this market
The development retainers here differ mainly in where the code ends up. Pexon Consulting builds inside the client's tenant: Deutz's private retrieval platform, Klinikum Landsberg am Lech's speech documentation live since March 2025, Liebherr's internal assistant reading a user's own Outlook and Teams content under existing Entra rights. Siili Solutions builds and then operates, with Bobotin at LähiTapiola Finance maintained as a managed service rather than handed over. Adnovum's Berna voicebot at Gebäudeversicherung Bern runs on Spitch speech technology with Adnovum owning the architecture and Azure integration. Squirro's work is engineering around its own licensed Insights Engine, documented at Henkel across 45 or more data sources. Xomnia's Enexis excavation-risk model is documented down to logistic regression, MLflow and Airflow in production, and Faculty's generative-AI tools run inside Tide's customer-service workflows with a published 10% cut in ticket-handle time. Hiflylabs took Billingo's text-to-SQL and RAG agent from proof of concept to full production on OpenAI, Snowflake and OpenSearch. The evidence is thinner in several cases: Mobile Reality's most inspectable AI is its own open-source MDMA forms framework, with Nestmedic's Pregnabit CTG algorithms the one named client build; Intunio publishes its prices in full and says on its own site that model training goes to partners; G+D Netcetera's and Bismart's named clients carry platform and BI work while their AI stays unnamed.

Ask each candidate what your own engineers could change without them. Code in your tenant and a bespoke build on a third-party speech layer leave different things behind; a licensed engine leaves a knowledge graph whose fate on non-renewal the curator says to confirm; a partner-built model leaves an ownership question Intunio's site does not answer. Mobile Reality's team page lists no data scientist, so a retainer there is LLM integration rather than model maintenance.

## Questions buyers ask

### How many AI agencies work with retainer on ai development?
44 agencies in our directory combine verified retainer client evidence with documented AI Development work. The current top-ranked are Square Root Solutions, Storm Technology, Lexunit — ordered by depth of documented client evidence, then our editorial scoring (portfolio quality, credibility, completeness); placement is never paid.

### How much does an AI agency cost for ai development?
Published rates across this page's agencies run €20–175 per hour (median ~€65). Project totals depend on scope — the rate index at /rates breaks the computed bands down by region, country and team size.

### How is the retainer model verified?
Every agency here documents retainer work on its own site or in a published case study, describing the engagement structure rather than a service-list claim. We never infer the model from portfolio tone, so this list only contains agencies that operate retainer engagements deliberately.

### Can these agencies embed consultants with our team?
9 of the agencies on this page document an embedded / team-extension working model. See the team-extension page for the full verified list, or check the engagement chips on individual profiles.

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Source: AIAgencies.eu — the curated register of European AI agencies. Rate provenance: "agency-confirmed" = disclosed via submission or claimed profile; "directory-listed" = Clutch or two agreeing B2B directories (lone unverified sources are never written). Full method: https://www.aiagencies.eu/methodology · Rate index: https://www.aiagencies.eu/rates