FSLY Stock Plummets 18%: Fastly Snaps Six-Week Winning Streak As Agentic AI Jitters Resume

• Fastly’s edge-security model is being questioned as AI tools emerge capable of bypassing traditional safeguards.
• Anthropic’s Project Glasswing, with Fastly left out, has raised doubts about its ability to keep pace with evolving AI threats.
• The company indicated that capital spending may increase to 10% to 12% of revenue in 2026.

Fastly Inc. (FSLY) shares plunged sharply on Friday, reversing six-week gains as investors reacted to a major development in artificial intelligence that could reshape cybersecurity expectations across the edge computing sector.

The steep decline followed the introduction of Anthropic's advanced AI model, Claude Mythos. 

Security Model Under Pressure

Anthropic system’s reported ability to autonomously identify and exploit software vulnerabilities has unsettled markets, raising concerns about the resilience of existing edge-based security frameworks.

Fastly has positioned itself as a provider of secure, high-speed content delivery at the network edge. However, the emergence of AI tools that can bypass traditional safeguards has raised questions about whether speed-focused infrastructure can still provide meaningful protection. 

Fastly stock traded over 18% lower on Friday afternoon. 

Unease deepened after Anthropic revealed a cybersecurity collaboration known as Project Glasswing, which includes major technology players. Fastly’s absence from the initiative could make it harder to adapt to rapidly evolving AI-driven threats.

Valuation Reality Sets In

The sell-off reflects growing skepticism around Fastly’s premium valuation, which had climbed to lofty levels amid enthusiasm for “AI at the edge.” While the company posted strong fourth-quarter revenue growth of 23%, the market is questioning whether future earnings can justify the elevated price-to-earnings multiple of 106, according to Koyfin data. 

The company signaled that capital expenditures could rise to between 10% and 12% of revenue in 2026, roughly double the prior year’s level, suggesting a prolonged investment phase.

How Did Retail Traders React? 

On Stocktwits, retail sentiment around the stock remained in ‘extremely bearish’ territory while message volume shifted to ‘high’ from ‘low’ levels in 24 hours. 

One user said software-as-a-service businesses might take a huge hit. 

FSLY stock has gained over 134% year-to-date. 

Also See: Citron Shorts Applied Optoelectronics, Calls Valuation Detached From Fundamentals And Flags Downside Risks

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