Shares in IBM recorded their steepest daily drop in more than 25 years on Monday, after AI start-up Anthropic said its Claude Code tool could be used to modernise a programming language run on IBM systems. IBM shares sank 13.2%, their biggest drop since 18 October 2000.
Cobol is a programming language widely used on IBM mainframes across banking, insurance and government systems.
“Modernising a Cobol system once required armies of consultants spending years mapping workflows. Tools like Claude Code can automate the exploration and analysis phases that consume most of the effort in Cobol modernisation,” Anthropic said in a blog post on Monday.
“With AI, teams can modernise their Cobol codebase in quarters instead of years,” it added.
Software stocks have been battered in recent months by market fears around the growing capabilities of AI tools, particularly following the launch of plug-ins from Anthropic’s large language model Claude, seen as the start-up’s push to become an application layer.
Shares of cybersecurity companies including CrowdStrike and Datadog also slumped on Monday, as investors weighed the potential impact of Anthropic’s new security tool on the industry. — Chris Thomas, (c) 2026 Reuters
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