Principal Software Engineer (Agentic AI, C# / .NET)
We are seeking a Principal Software Engineer (Agentic AI & Legacy Modernization) to join a high-impact, four-person squad running an AI-augmented, specification-driven modernization program across 149 production applications for a leading global asset management firm. In this role, you will work hand-in-hand with senior consultants and embedded client engineering teams to build and scale an advanced AI-driven pipeline that remediates security vulnerabilities, expands automated test coverage to 70%+, and drives multi-year cloud migration. You will leverage cutting-edge agentic coding tools to analyze legacy codebases, perform autonomous defect remediation, and enforce high-confidence quality gates across an enterprise ecosystem primarily built on C# / .NET and Python.
Essential functions
- Drive agentic diagnostics, vulnerability triage, and automated code assessments using Copilot agent mode, Cursor/Windsurf/Claude Code, and client-internal LLM platforms.
- Validate and autonomously remediate pre-identified security vulnerabilities (CVE triage, dependency upgrades, SAST/DAST findings) to ensure codebases pass modern deployment gates.
- Architect functional and end-to-end test suites using AI, evaluating existing test quality and raising test coverage to 70%+ to eliminate reliance on manual QA.
- Apply spec-driven methodologies (e.g., JUXT Allium, GitHub spec-kit) to automatically analyze codebase correctness and enroll new services into the standing remediation pipeline.
- Perform deep architectural analyses on flagship codebases (>0.5M LoC) to uncover new strategies for automated refactoring, analysis, and cloud deployment via GitHub Actions.
- Collaborate closely with London-based onsite consultants, security leads, and technical client stakeholders to prioritize backlogs, validate findings, and ship production-ready updates.
Qualifications
- 8+ years of hands-on software engineering experience with strong versatility across legacy, under-documented enterprise codebases.
- Proven, practical experience leveraging LLMs and agentic coding workflows (Copilot agent mode, Cursor, Windsurf, Claude Code, or similar) to generate code, refactor applications, and review tests at scale.
- Deep polyglot development discipline with strong production-grade experience in C# / .NET and/or Python.
- Strong software testing discipline with a focus on test quality over vanity coverage metrics, test-driven refactoring, and automated test suite design.
- Hands-on experience with security remediation, dependency management, and clearing CVEs in enterprise systems.
- High autonomy, pragmatic problem-solving skills, and excellent written English communication for seamless remote collaboration with UK-based teams.
Would be a plus
- Experience with specification-driven AI development tools (such as JUXT Allium or GitHub spec-kit).
- Track record of modernizing legacy .NET ecosystems (.NET Framework to .NET 6/8) or frontend frameworks (Angular, replacing WPF/WCF surfaces).
- Practical experience designing or extending automated code-analysis and remediation CI/CD pipelines (GitHub Actions, Azure DevOps, Octopus Deploy).
- Background in financial services or other heavily regulated enterprise environments.
We offer
- Opportunity to work on bleeding-edge projects
- Work with a highly motivated and dedicated team
- Competitive salary
- Flexible schedule
- Benefits package - medical insurance, sports
- Corporate social events
- Professional development opportunities
- Well-equipped office
About us
Grid Dynamics (NASDAQ: GDYN) is a leading provider of technology consulting, platform and product engineering, AI, and advanced analytics services. Fusing technical vision with business acumen, we solve the most pressing technical challenges and enable positive business outcomes for enterprise companies undergoing business transformation. A key differentiator for Grid Dynamics is our 8 years of experience and leadership in enterprise AI, supported by profound expertise and ongoing investment in data, analytics, cloud & DevOps, application modernization and customer experience. Founded in 2006, Grid Dynamics is headquartered in Silicon Valley with offices across the Americas, Europe, and India.
