Surge, Now Always On: Surge for Flows Is Live

If you've been following along, you already know Surge. We launched it earlier this year as a drag-and-drop universal content block that drops Backstroke's predictive hero intelligence directly into your Klaviyo campaigns. Customers using Surge have documented an average 31% revenue lift on the campaigns it touches.

It works. The only catch: until today, it only worked on campaigns.

Now, that changes.

Surge is now live inside Klaviyo flows. The same predictive hero intelligence that's been lifting campaign revenue now runs automatically on every welcome, every abandoned cart, every browse abandon and every post-purchase send, without your creative team building anything new.

Flows Are Ice Cream. Campaigns Are the Cherry.

The marketing-ops version of this thesis is simple. Customers update their flow content roughly once a quarter (site-wide sales, brand refreshes, seasonal swaps). The rest of the time, flows just run. Quietly. Continuously. They send the moment a subscriber joins your list, the moment they abandon a cart, the moment they buy.

Across the average Backstroke account, there are around 13 active flows doing exactly that. For some of our customers, those flows generate 40 to 70% of total email revenue. They are the baseline (the ice cream), and Surge has not been available here until now.

Campaigns are still the cherry. They're where you push your hero moments, your launch sends, your sale calendars. Surge has been making those campaigns 31% more profitable on average. But every week of revenue depended on you choosing to push another campaign through it.

Surge for Flows changes the math. Drop the Surge block into your welcome step once. Backstroke serves the predicted-best hero variant to every cohort that enters that flow, forever, without your creative team queuing up a single additional asset.

What Surge for Flows Actually Does (In Plain English)

You drop a single Backstroke universal content block into any Klaviyo flow step that contains a hero. From that moment forward:

• Every subscriber who enters the flow gets the predicted-best hero variant for them, not a one-size-fits-all static image.

• Cohorts are scored continuously, and winners are recalculated as new performance data comes in.

• New cohorts in the account get picked up automatically; you don't have to rebuild the block.

• New subscribers who haven't been profiled yet receive the fallback variant, which is already the predicted-best performer across your audience. The cost of being unprofiled is muted, not catastrophic.

You manage flow content the way you've always managed flow content. We just make sure that whenever a flow fires, the hero inside it is the right hero for the person receiving it.

What This Means for You

1) The lift you've been seeing on campaigns now runs on every send. If you've been using Surge on campaigns, you already know the pattern: the right hero, in front of the right cohort, lifts revenue. Until today that lift only showed up on the campaigns you remembered to push through Surge. Now it shows up on every welcome, every abandoned cart, every browse abandon and every post-purchase send. Same lift mechanic, on a much bigger surface.

2) Revenue compounds while you sleep. A Surge campaign drives lift the week it sends. A Surge flow drives lift on Tuesday at 2:14 a.m. when a new subscriber joins your welcome series, again at 9:07 p.m. when someone abandons a cart and again at 11:30 a.m. next Sunday when a post-purchase trigger fires. You stop choosing between "the campaign I sent this week" and "the campaign I'll send next week." Every flow you already have running becomes another revenue lift surface, working in the background, on its own schedule.

3) Your creative team gets their time back. Backstroke's job is to make the email you're already sending more profitable. The version of that promise that scales doesn't ask your creative team for new assets every week. Set Surge inside a flow once. Refresh it on the same cadence you already refresh your flow art (about once a quarter). Same workload as today. Materially more revenue out the other end.

Who's Already Using It

Three Backstroke customers are in the first wave:

• Perry Ellis: pairing Surge for Flows with their Shopify-native catalog

• Homeroom: the premiere retention agency is piloting Surge for Flows with multiple customers

• PSD: running Surge for Flows on their welcome series and abandoned cart, the two highest-revenue flow steps in their account

We're running a controlled A/B with these accounts over a 4-week window, instrumenting Welcome and Abandoned Cart first. Primary metric: revenue per recipient on the instrumented step. Look out for detailed case studies soon.

The Road That Got Us Here

Surge for Flows is the latest in a string of releases that, taken together, tell a single story. Backstroke's predictive intelligence is moving deeper into the email surfaces our customers already use.

• Our L5 Agentic Engine shipped in December, giving us the dynamic email generation stack that everything since has been built on.

• Hero Lab followed in February with AI-generated hero images and Predictive Templates for the campaigns side of the house.

• We launched Surge earlier this year: predictive hero intelligence inside Klaviyo's universal content blocks, on the campaign surface.

• Last week, we hit the final milestone of our SOC 2 Type II audit: 100% of our control evidence has been reviewed and the official attestation report is on its way.

• This week: Surge moves into flows.

Each step compounds on the last. The L5 engine made dynamic generation possible. Surge made it easily accessible inside your ESP. SOC 2 makes it deployable inside an enterprise stack. Surge for Flows makes it run forever.

What's In It If You're Already a Surge Customer

You're getting more Surge for the same Surge. Reach out to your account manager, as we're rolling Surge for Flows into existing Surge subscriptions for customers in the first wave, with a structured upgrade path for everyone else. If you've been throttling campaign cadence to "save Surge for the big sends," you no longer have to.

What's In It If You're Not Yet a Customer

Two things.

First: the most common pushback we hear from prospects is "we already have a creative team. What does Surge actually save us?" The answer used to be "more lift on the campaigns you're already running." The answer now is "plus a 13-flow baseline that produces variant-driven revenue without ever asking your team for another asset." That's a different conversation.

Second: if you've been waiting to evaluate Backstroke until the security story was settled, that wait is nearly over. Our SOC 2 Type II evidence review is complete and the official attestation is imminent. The procurement objection is on its way out. The product surface just got bigger. The case for getting started got harder to ignore.

What's Next

A few things on deck:

• Subject Line & Preheader Surge is in dev. Same predictive engine, applied to the #1 and #2 drivers of open rate.

• Surge in Slack (campaign-level Surge optimization without leaving Slack) is also in dev. Detect, score, approve, ship. One thread.

• Cohort lifecycle inside flows (what happens when your account's cohort set changes after a flow has been live for two weeks) is the next discovery question we're answering.

The shape of Backstroke's product is the same as it's always been: make the email you're already sending more profitable. The surface area is just getting bigger every month.

Ready to put Surge inside your flows?

• Request a demo and we'll wire up your highest-revenue flow as the first proof point.

• Already a Surge customer? Reach out to your account manager about the Surge for Flows upgrade path.