Cooperation DetailsStart date: As soon as possible, within 3–4 weeksContract duration: 12 months initially, with possible extensionsContract type: B2BWorking model: Hybrid, with 2 days per week from the Warsaw office and the remaining days remotelyEquipment: Laptop provided by the clientTravel: Up to one possible business trip per year to the Netherlands or France (paid by the Client)Languages: fluent Polish and English are a mustWe are looking for a Senior Frontend Developer to join a new initiative delivered for an international client operating in the information services sector.Both projects are greenfield initiatives developed from scratch. Each team will consist of approximately five people, including a Tech Lead, Backend Developer, Frontend Developer, and QA Engineer.ResponsibilitiesDeveloping frontend applications using React and TypeScript.Building advanced enterprise-grade user interfaces, including dashboards, forms, filters, cards, and drill-down views.Integrating frontend applications with APIs using a contract-first approach.Designing and developing reusable components and solutions based on a design system.Ensuring accessibility, responsiveness, performance, usability, and overall application quality.Implementing explainability-focused UI patterns, including evidence, rationale, confidence levels, and source traceability.Building human review workflows that support approval, rejection, and manual override of system recommendations.Collaborating closely with the Tech Lead, Backend Developers, QA Engineers, and other team members.Contributing to component, UI integration, and regression testing.Working according to spec-driven development, API-first, and event-driven delivery principles.Ensuring auditability, traceability, and explainability by design.Supporting thin vertical slice and steel-thread delivery to validate end-to-end functionality early in the development process.RequirementsSenior-level experience in frontend software development.Strong practical knowledge of React and TypeScript.Experience in building complex enterprise-grade applications and user interfaces.Hands-on experience with API integration.Familiarity with contract-first or API-first development.Experience in creating reusable components and working with design systems.Good understanding of accessibility, responsive design, performance optimisation, and usability.Experience with frontend components, integration, and regression testing.Ability to work effectively in a cross-functional product team.Strong quality and validation mindset from the beginning of the development lifecycle.Fluency in Polish and English.Experience in projects involving AI, agentic workflows, human-in-the-loop governance, explainability, or decision-support systems will be considered an advantage.

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