How PwC Uses Claude Code to Cut Legacy Analysis from 6 Weeks to 2.5 Days

PwC is one of the world’s largest professional services firms, with 400,000 employees providing audit, tax, and consulting services to organizations globally. Partner Ussama Baggili leads the legacy and mainframe modernization practice, working with clients who rely on decades-old systems—AS400 installations, ERP platforms for supply chain, healthcare TPA systems—whose original documentation has disappeared and whose code no longer has authors who can explain it.

The traditional discovery process for these engagements was time-consuming by design: collect documentation, interview stakeholders, manually review code, iterate over interim deliverables, and shape a final recommendation. This process routinely took six weeks before any client saw a result. For complex legacy systems, even getting to a credible point of view required significant upfront investment that made early-stage client conversations difficult.

Baggili began using Claude Code for the analysis phase rather than just the coding output, discovering that the analysis itself—when produced well—was the deliverable. He built systemized Claude Code workflows: given access to a client’s codebase, Claude can produce deliverable-worthy documentation and recommendations in 2.5 days. He packaged these workflows into Claude Skills that any consultant can trigger, and built what amounts to an executive assistant in Claude Code that produces branded decks, diagrams, and content in minutes. Believing non-technical users should start with Claude Code rather than graduate to it, he ran a firm-wide training session with a single-line install script, a coaching plugin wired into a CLAUDE.md project structure, and a simulated day-in-the-life walkthrough of three core tasks.

The results were immediate. Within one hour, 400 leaders and consultants had built their first RFP response drafts, functional specs, and mobile app prototypes. The six-week discovery engagement now takes 2.5 days. Clients who previously had to invest heavily in scoping work can now see what their legacy system contains—and what modernization would require—before committing significant resources.

PwC is now scaling the approach globally. A 30,000-person training rollout is underway, using the same coaching plugin and project structure that worked for the initial 400. The goal is to treat Claude as a capable colleague across all 400,000 employees, not a specialist tool reserved for technical staff—starting with Claude Code as the entry point that builds the muscle memory for everything that follows.