Brent crude has fallen 33% from its April peak of $117 a barrel to $77.80 this week, as the Islamabad Memorandum, signed June 17, set in motion the fastest reopening of the Strait of Hormuz since Iran effectively closed it on February 28. Persian Gulf oil flows through the strait are now running at roughly 75% of prewar levels.
None of that has stopped someone from firing on a commercial vessel in the same waterway. An unidentified projectile struck a cargo ship off the coast of Oman on Wednesday, reported by the maritime monitoring group UKMTO. Several commercial ships turned back. The strait has reopened faster than almost anyone expected in May. It has not yet reopened completely, and the gap between those two facts is where the risk to Canadian portfolios now sits.
The Mechanism: From a Shipping Lane to the TSX
The chain from this specific waterway to a Canadian portfolio runs through one number: the price of oil. Roughly 20% of the world's oil passes through the Strait of Hormuz on its way to market. When Iran moved to control transit through the strait at the war's outset, oil prices surged more than 55% within weeks, dragging the TSX energy sub-index, which carries Suncor, Canadian Natural Resources and Cenovus at a combined weight north of 60%, to new highs alongside it.
The same mechanism now works in reverse. As tankers move again, the price falls, and the TSX energy names that rallied hardest on the way up are the same names giving back the most on the way down. The TSX's broader index has been somewhat insulated by financials and gold miners, but energy is, and has been all year, the single largest swing factor in the composite's direction.
Brent crude's path since the war began shows a premium that built over March and April and has now mostly unwound, even as the specific incident behind this week's shift in sentiment shows the unwind is not guaranteed to continue in a straight line.
Brent prices are shown as monthly averages for January through May and daily closes for June, the resolution at which each figure is reported. The reference line uses Brent's close on February 27, the day before military action began.
Base Case Versus Tail Risk
The base case, and the one priced into oil markets through Friday's session, is that the reopening continues. Saudi Arabia has resumed tanker traffic toward its Ras Tanura terminal for the first time since March. Qatar issued its first post-war crude tender. Iran and the United States have agreed to a shipping hotline specifically to manage incidents like Wednesday's without escalating them into something larger. Technical talks in Switzerland are continuing under a 60-day roadmap toward a final agreement, even after one earlier round of talks was postponed.
The tail risk is narrower than it was in April but has not disappeared. Iran's chief negotiator said this week that the strait would be managed under Iranian arrangements going forward, language that leaves room for Tehran to reassert control if talks on its nuclear program, still unresolved, break down. An estimated 80 mines remain in the strait's central shipping route, according to the tanker owners' trade group Intertanko, with vessels currently routed around them through Iranian and Omani waters instead of the main channel.
What Would Actually Move This Again
A move back toward the April peak would require either a collapse of the Switzerland talks specifically over Iran's nuclear enrichment levels, the single issue both sides have explicitly left for the next 60 days, or a second attack serious enough to make tanker owners turn back en masse rather than individually, as happened after Wednesday's strike. Neither is the expected outcome. Both are more plausible this month than they were when the Islamabad Memorandum was signed, precisely because the easier, symbolic step of signing an agreement has already happened, and the harder work of clearing mines from the shipping lane and resolving a nuclear dispute has not.
The TSX energy names that drove this year's index gains are now trading the mirror image of the trade that built them. That is not a verdict on whether the original positions made sense. It is a description of a single shipping lane doing what shipping lanes do when the flag on the map changes from red to a cautious yellow, not yet green.