What Callstack does

Callstack (Callstack.io Sp. z o.o.) is a Wrocław, Poland-headquartered engineering services firm founded in 2016 that specializes in React Native cross-platform mobile delivery. It serves large enterprises — including Microsoft, Meta, Amazon, PwC, Ticketmaster, Questrade, MLS, Dream11, Expensify, AutoZone, HelloFresh, and Momo — through custom, multi-year professional services engagements covering feature development, end-to-end product delivery, AI-assisted migrations, architecture and performance optimization, infrastructure setup, and team training. Buyer targets are CTOs, VP of Engineering, and mobile platform leaders; sales run through direct enterprise engagement and consultation booking.

The company's core technology combines React Native domain expertise with AI-native delivery infrastructure. Proprietary and open-source assets include Apex (a specialized coding model for React Native), Agent Device (an agent-native automation layer for mobile/TV/desktop apps with multimodal accessibility-tree inspection), Re.Pack (module federation for mini-apps), and React Native Builder Bob (scaffolding). These tools are delivered through four service umbrellas — AI-Native Engineering, Agentic Infrastructure, AI Engineering Adoption, and Enterprise AI Governance — supplemented by ISO 27001-certified processes and products serving 7B+ end users across 100+ enterprise clients.

The business model is professional engineering services billed via custom multi-year contracts, augmented by content and community-led demand generation (React Conf co-organization, Agent Conf, podcast, ebooks, open-source contributions). Distribution is global, headquarters-based in Wrocław, and the company is a founding Platinum member of the React Foundation under the Linux Foundation, providing governance influence over the underlying framework. Capital is provided by Viking Global Investors, and there is no public listing.

Name

Callstack

Legal name

Callstack.io Sp. z o.o.

Website

https://callstack.com

Company type

Private

Founded year

2016

Operating status

Operating

Headcount range

11–50 employees

Short description

Callstack is a Wrocław, Poland-based React Native engineering services firm serving 100+ global enterprise clients with AI-native cross-platform mobile delivery, backed by Viking Global Investors and a founding Platinum member of the React Foundation.

Ownership category

akta.pro rank

Product category

Mobile Engineering Consulting

NAICS

Custom Computer Programming Services (541511)

SIC

Services-Computer Programming Services (7371)

akta.pro primary industry

Conversational AI Platforms (chat/voice bots, orchestration) (HDAAAFAC)

akta.pro secondary industries

AI Integration & Orchestration Platforms (Connectors, Workflow, iPaaS for AI) (HDAEANAI), Contact Center (CCaaS) & Customer Engagement Voice (HDAIAHAF)

Keywords

• React Native development
• AI-native engineering
• Cross-platform mobile apps
• Agentic infrastructure services
• Open source React Native

Headquarters

HQ city

Wroclaw

HQ country

Poland

HQ region

Europe

Offices1 record

Markets served

GTM type

B2B

Offering type

Services

Cost components

Personnel, Technology or R&D, Marketing or Sales, Operations, Infrastructure

Revenue model

1. Professional Engineering Services: Consulting and engineering services for React Native development including feature development, end-to-end product development, AI-assisted migrations, architecture and performance optimization, infrastructure setup, and team training.

Pricing tiers

Go-to-market motion2 records

Distribution channels1 record

Marketing channels10 records

Core offering

Callstack delivers AI-native engineering services for React Native, providing feature development, end-to-end product development, AI-assisted migrations, architecture and performance optimization, infrastructure setup (AI-driven QA, custom agents, self-hosted CI/CD), and team training for enterprise clients. The firm also develops and open-sources complementary tools such as Agent Device (agent-native mobile automation), Apex (a specialized coding model for React Native), Re.Pack (module federation), and React Native Builder Bob (scaffolding).

Product overview

Callstack is a React Native-focused services and technology company offering AI-native engineering services, agentic infrastructure products, and AI engineering adoption programs. The core portfolio includes Apex (specialized coding model for React Native), Agent Device (agent-native automation layer for mobile/TV/desktop apps), and Re.Pack (module federation solution), alongside an extensive open source ecosystem of 300+ React Native libraries. These products are delivered alongside professional services under AI-Native Engineering, AI Engineering Adoption, and Enterprise AI Governance umbrellas. Callstack is a founding Platinum member of the React Foundation under the Linux Foundation, providing direct access to framework decisions.

Differentiator

Problem solved

Functional benefit

Products and services

• AI-Native Engineering Engineering service combining React Native expertise with AI tooling, including Feature Development, End-to-End Product Development, AI-Assisted Migrations, Architecture & Performance, and Infrastructure services (AI-Driven QA & Testing, Custom Agents, Self-Hosted CI/CD).
• AI Engineering Adoption Service helping teams adopt AI tools effectively, including Tooling Setup (Claude Code, Cursor, Codex, MCP configuration), Adoption Measurement, and Team Training to build AI-native engineering capabilities.
• Enterprise AI Governance Enterprise-focused service for adopting AI under compliance and security constraints, including Custom & Private Models, Regulatory Compliance, and AI Security & Audits for regulated industries.
• Agentic Infrastructure Infrastructure services for agentic delivery, including AI-Driven QA & Testing using Agent Device, Custom Agents for AI automation, and Self-Hosted CI/CD Infrastructure that turns agent output into faster engineering and smoother releases.
• Apex Specialized coding model designed for React Native that achieves frontier coding results for mobile workflows at a fraction of the cost compared to general-purpose models. Available via request access.
• Agent Device Open-source agent-native automation layer that gives AI coding agents hands and eyes for mobile, TV, and desktop apps. Enables agents to open apps in simulators, move through UI, inspect accessibility data, capture screenshots, pull logs, profile performance, debug crashes, and run tests. Published at agent-device.dev.
• Re.Pack Open-source module federation solution for React Native enabling code sharing across mini-apps. Used in production at Teamworks (achieving 10-minute change lead time for mini-app delivery) and Momo.
• React Native Builder Bob Open-source scaffolding tool for React Native libraries that generates platform folders, TypeScript specs, and default native code. Used to bootstrap TurboModule libraries.

Quantifiable outcome

• 5x faster message sending time for Expensify
• +7 more outcomes

Named customers15 records

Segments2 records

Ideal customer profiles2 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

AI capability7 records

Feature4 records

Partnerships

Five partnerships are on record, tiered core.

• React Foundation (under Linux Foundation)coreStrategic or Co-development PartnerCallstack is a founding Platinum member of the React Foundation, an independent entity hosted by the Linux Foundation to ensure long-term stewardship of React and React Native. The foundation supports React, React Native, and related components through open governance. Initial founding members include Meta, Amazon, Microsoft, Huawei, Vercel, Expo, and Software Mansion alongside Callstack.
• MetacoreStrategic or Co-development PartnerOfficial Meta partner for React Native. Co-organizers of React Conf. As core contributors to React Native, Callstack works closely with Meta on framework development and ecosystem growth.
• MicrosoftcoreStrategic or Co-development PartnerTrusted partner for React Native development. Collaborates on React Foundation alongside other major tech companies.
• ExpocoreTechnology or IntegrationCollaborative relationship on React Native ecosystem. Callstack engineers contribute to Expo and build browser-based React Native playground for Expo.
• AmazoncoreTechnology or IntegrationFounding member of React Foundation. Callstack works with Amazon on TV development including FireTV optimization and Amazon IVS integration.

Scale indicators8 records

Recent moves7 records

Expansion highlights6 records

Others

• Vercel: Vercel is a co-founding member of the React Foundation and the primary maintainer of Next.js. While Vercel operates in adjacent web framework infrastructure rather than React Native services, both companies share the React Foundation governance table and overlap on the broader React ecosystem positioning Callstack leverages for inbound demand.

Regional players

• Netguru: Netguru is a Poland-based digital consultancy offering mobile, web, and AI development services. While not React Native-specialist, it competes for the same enterprise engineering services budget from a similar cost-base geography and overlaps on cross-platform mobile delivery.
• Infinum: Infinum is a Croatia-based digital product development agency with strong mobile and React Native capabilities. It competes with Callstack for European enterprise mobile engagements from a neighboring CEE geography with similar cost structure.

Emerging players

• GenUI: GenUI is a US-based mobile engineering firm specializing in React Native and Flutter development. It directly overlaps with Callstack on cross-platform delivery but lacks the same depth of open source library footprint or React Foundation governance involvement.
• Viveo: Viveo is a mobile-focused engineering consultancy serving enterprise clients with React Native and Flutter expertise. While smaller than Callstack, it competes for the same enterprise cross-platform RFPs and represents the emerging specialist competitor profile.

Direct peers

• Theodo: Theodo is a global digital agency specializing in React, React Native, and Node.js with offices in Paris, London, and New York. It directly competes with Callstack for cross-platform mobile engineering projects and shares the same niche consultancy positioning with strong open source contributions.
• Expo: Expo is the React Native framework platform company (EAS, Expo Router) and a co-founding member of the React Foundation. While Callstack is services-led and Expo is tooling-led, both occupy the same React Native ecosystem and increasingly intersect as Callstack integrates Expo EAS into client deliveries (e.g., the 6x faster build case study).
• Infinite Red: Infinite Red is a US-based React Native consulting agency and core contributor that runs the popular 'Ignite' boilerplate. Both firms compete directly for enterprise React Native engagements, share core-contributor credibility, and operate in the same AI-native mobile delivery narrative.
• Software Mansion: Software Mansion is a Poland-based React Native and mobile development agency and a co-founding member of the React Foundation alongside Callstack. Both firms offer React Native consulting, open source contributions, and enterprise mobile delivery, making them the closest direct comparables in the specialist React Native services niche.

Broad incumbents

• Thoughtworks: Thoughtworks is a global technology consultancy with deep React Native practice and enterprise-scale delivery capability. It competes with Callstack on larger transformation programs and increasingly in AI-native engineering enablement, though without the same depth of React Native core-contributor credibility.

Market position

Strengths5 records

Weaknesses4 records

Competitive moat5 records

Key risks5 records

Key highlights7 records

Customer concentration

• Xx.com/callstackio

Compliance1 record

Revenue estimate

Valuation estimate

Number of profiles

Profiles1 record

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A1 record

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Callstack