Porter’s Five Forces, Reread for 2026
Industry boundaries are now capability stacks. Buyer power moved to AI agents. The framework still holds. The reading order inverted.
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In 1979, Michael Porter published “How Competitive Forces Shape Strategy” in Harvard Business Review. The article reframed strategy. Industry profitability is determined by five structural forces: rivalry among existing competitors, threat of new entrants, threat of substitutes, bargaining power of buyers, and bargaining power of suppliers. Forty-six years on, the framework still anchors nearly every MBA strategy syllabus.
It still holds. The operating context is inverted underneath it.
Porter’s framework rests on a single assumption that was unimpeachable in 1979 and questionable in 2026. Industry boundaries were stable enough to draw a line around. Actors inside that line were knowable, countable, and slow-moving. Information was asymmetric, expensive to gather, and bound by human cycle time. The framework was built on that floor.
That floor moved.
AI-mediated discovery breaks the asymmetries Porter took as foundational. Buyers compare hundreds of options in seconds through autonomous agents. New entrants face near-zero capability barriers in software-mediated work. Substitutes appear from adjacent capability stacks, not from within the named industry. The five forces still apply. Their relative weights inverted.
Most strategic plans still front-load rivalry analysis. The two forces that matter most in 2026 sit at the bottom of most leaders’ attention. Buyer power mediated by AI agents. Substitution from adjacent capability stacks. The framework holds. The reading order is inverted.
The solo operator stops positioning against named competitors. They map their business as a node in a capability stack and ask which adjacent capabilities to absorb and which to hand to an agent. The stack moves faster than the org chart.
The startup founder runs Five Forces weekly, not annually. The threat of new entrants is measured in months. Build the analysis into the Friday review. The first force to spike tells you where the next quarter’s capital goes.
The small-business strategist treats the buyer power inversion as the urgent threat. Customers are choosing through AI-mediated discovery. The buyer relationship built over decades is now intermediated by an agent that did not exist 18 months ago. The other four forces matter. This one moves first.
The companion prompt pack turns these ideas into a practice.
Five prompts: Diagnose, Stress-test, Translate, Decide, Loop. The first runs Five Forces on your company. The second re-runs it under AI-era conditions. The third translates to your operator tier. The fourth forces a decision and names the trade-off. The fifth schedules the practice as a weekly cadence with a 90-day review.
Porter was correct for 1979. The translation is our work in 2026.
Companies are becoming tech stacks.
We are all becoming companies.
- j -
Download a pdf of the prompt pack here.
John Brewton documents the history and future of operating companies at Operating by John Brewton. He is a graduate of Harvard University and began his career as a Phd. student in economics at the University of Chicago. After selling his family’s B2B industrial distribution company in 2021, he has been helping business owners, founders and investors optimize their operations ever since. He is the founder of 6A East Partners, a research and advisory firm asking the question: What is the future of companies? He still cringes at his early LinkedIn posts and loves making content each and everyday, despite the protestations of his beloved wife, Fabiola, at times.