Product Build Day // Podcast

About Product Build Day // Podcast

Building got cheap. Deciding got hard. You can vibe code a working app in five minutes now, so the hard part is finding out which idea is worth building. I'm Marcin Klimaszewski. I run Product Build Day, and in every episode answer one question that product managers, designers and founders keep asking, in about ten minutes. Topics: product discovery, testing ideas, vibe coding and prototyping with AI. Each episode brings a real story from our build days across Europe, numbers with sources, and one thing to try this week.

Publisher

Marcin Klimaszewski

Category

business

Language

en

Explicit

No

First episode

2 Oct 2026

Latest episode

23 Oct 2026

Latest episodes

16 episodes in the feed.

1. 

   23 Oct 2026

   Don't ask for a project. Ask for one day that earns the next one.

   This spring, 85 percent of the finance chiefs Deloitte asked in twelve European countries said now is not the time to take on more risk. A request for a project gets a no. A day is a small risk with a ceiling. Ask for one day with a number that could kill the idea, put the do-nothing option on the page with its own number, and let the day earn the next step. What you'll hear: What happened in Thessaloniki after the day The five-line ask that fits on one page What the UK's Green Book says about doing nothing Why each step gets approved on what the last one showed What to say when your manager works in sprints Try this week: write your one-day ask: the challenge, the metric that would kill the idea, the do-nothing option and its number, who you need and which day, and what you'll ask for next. Send it, and ask for a yes or a no by Friday. That's the end of the third week of Product Build Day Podcast. Thank you for listening. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Deloitte: European CFO Survey, spring 2026 (https://www.deloitte.com/global/en/insights/topics/business-strategy-growth/european-cfo-survey-spring-2026.html) HM Treasury: The Green Book 2026 (https://www.gov.uk/government/publications/the-green-book--2/the-green-book-2026) Die Produktwerker: Making decisions under uncertainty, Dominique Winter (23 February 2026, in German) (https://produktwerker.de/entscheidungen-unter-unsicherheit-treffen/) Product Build Day with Ionian Technologies, Thessaloniki, May 2026 (https://productbuildday.com/case-studies/ionian-technologies)

2. 

   22 Oct 2026

   Why the decision is made before your first slide

   Show people the same idea twice, and the second time they rate it almost a full point higher. The decision about your idea starts before your first slide. The meeting is the second time they see your idea. Make sure the first time happened: a link two days ahead, the first slot on the agenda, and a decision rule everyone agreed to before seeing the result. What you'll hear: A mistake I made in Athens, and the rule the room noticed What 210 car-maker employees did with an idea they had seen before Why the proposal after a funded one gets less money Why a former CPO calls corridor conversations essential When talking before the meeting turns into lobbying Try this week: before your next decision meeting, send the decider the prototype two days ahead with one question, ask for the first slot, and write the decision rule into the agenda. Next episode: don't ask for a project. Ask for one day that earns the next one. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Greul, Schweisfurth and Raasch: Does familiarity with an idea bias its evaluation? (PLOS One, July 2023) (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0286968) Criscuolo, Dahlander, Grohsjean and Salter: The sequence effect in panel decisions (Organization Science, 2021) (https://pubsonline.informs.org/doi/10.1287/orsc.2020.1413) Le Ticket: François de Bodinat on why the CPO role is hard (17 May 2026, in French) (https://www.le-ticket.fr/francois-de-bodinat-le-role-de-cpo-est-difficile-mais-pas-pour-les-raisons-dont-on-parle-generalement/150234/) Itamar Gilad: Why good product ideas don't survive (24 September 2026) (https://itamargilad.com/good-ideas/) Product Build Day Athens, July 2026 (https://productbuildday.com/case-studies/athens-july-2026) Product Build Day September tour: Amsterdam, Copenhagen, Stockholm and Berlin (https://productbuildday.com/case-studies/september-tour-2026)

3. 

   21 Oct 2026

   How do you do discovery when nobody gives you the time?

   Almost everyone says AI saves them time. Few can say where that time went. And 71 percent of product people say they don't spend enough time with customers. Nobody gives you time for discovery. Claim ninety minutes a week, the same slot every week, and name it after one decision. What you'll hear: Where a third of a product owner's week goes A street test in Zwolle with clear findings, and what happened next Why findings without a decision get filed What fits into ninety minutes: two conversations and one decision What to do when your manager keeps taking the slot Try this week: write the one decision you want to make by the end of the month, book ninety minutes at the same time every week for four weeks, put the decision in the title, and invite your first two people. Next episode: why the decision is made before your first slide. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Product Focus: 2026 Survey of the Product Management Profession (PDF) (https://cdn.productfocus.com/wp/wp-content/uploads/2026/03/Product-Focus-Industry-Survey-Report-2026.pdf) ProductCraft: The state of product management in Poland 2025 (3 February 2025, in Polish) (https://newsletter.productcraft.pl/p/stan-product-managementu-w-polsce-2025) Productowner.nl: National Product Owner Survey 2026 (April 2026, PDF, in Dutch) (https://productowner.nl/app/uploads/2026/04/260410-Nationale-Product-owner-onderzoek-2026-1-1.pdf) Linus Wiggers, Productowner.nl: Product owners and AI (12 October 2026, in Dutch) (https://www.productowner.nl/blogs/product-owner-en-ai/) Gebruiker Centraal: Testember 2025, election materials tested on the street in Zwolle (in Dutch) (https://www.gebruikercentraal.nl/testember-2025/communicatiemateriaal-over-verkiezingen/) Product Build Day with Ionian Technologies, Thessaloniki, May 2026 (https://productbuildday.com/case-studies/ionian-technologies)

4. 

   20 Oct 2026

   My CEO counts AI features. What now?

   Ninety-six percent of companies plan new AI features. For most of them, the revenue impact stays below ten percent. So what do you do when your CEO counts AI features? The CEO's wish is reasonable. The unit is wrong. Count customer problems where a number you already track moved, and let AI compete for the job against simpler answers. What you'll hear: Two winning teams, one with AI at its center and one without The question I asked on stage in Athens, and why the challenge's last words decided it What Klarna counted in 2024, and what its CEO said in 2025 The report to bring your CEO instead of a feature count When AI is the whole answer Try this week: take your AI feature list, write next to each feature the customer problem it solves and the number that should move, check the clearest problem with five conversations, and propose a new report: problems solved and numbers moved. Next episode: how do you do discovery when nobody gives you the time? I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Simon-Kucher: How to win with AI in 2026 (3 February 2026) (https://www.simon-kucher.com/en/insights/how-win-ai-2026) Product Focus: 2026 Survey of the Product Management Profession (PDF) (https://cdn.productfocus.com/wp/wp-content/uploads/2026/03/Product-Focus-Industry-Survey-Report-2026.pdf) Productowner.nl: National Product Owner Survey 2026 (April 2026, PDF, in Dutch) (https://productowner.nl/app/uploads/2026/04/260410-Nationale-Product-owner-onderzoek-2026-1-1.pdf) Linus Wiggers, Productowner.nl: Product owners and AI (12 October 2026, in Dutch) (https://www.productowner.nl/blogs/product-owner-en-ai/) tech.eu: Klarna's AI assistant does the work of 700 people (28 February 2024) (https://tech.eu/2024/02/28/power-of-ai-is-happening-right-now-says-klarna-boss-as/) Maginative: Klarna dials back its AI customer service strategy, reporting Bloomberg (8 May 2025) (https://www.maginative.com/article/klarna-dials-back-its-ai-customer-service-strategy-now-its-hiring-humans-again/) Mind the Product: Klarna goes on recruitment drive after ditching AI-first policy (14 May 2025) (https://mindtheproduct.com/klarna-goes-on-recruitment-drive-after-ditching-ai-first-policy) Product Build Day Warsaw, July 2026 (https://productbuildday.com/case-studies/warsaw-july-2026) Product Build Day Athens, July 2026 (https://productbuildday.com/case-studies/athens-july-2026)

5. 

   19 Oct 2026

   "I think this is a good idea" isn't enough. What is?

   "I think this is a good idea" is not enough. Product owners in the Netherlands gave that advice to new colleagues this year. So what is enough to win your idea a place on the roadmap? A one-pager full of conviction answers one question, and only in words. Bring a prototype your boss can click, a first signal from real people measured against today's number, and a date for the decision. What you'll hear: How a product lead at Payfit got another squad's roadmap to make room The question an experienced product person asked me in Stockholm, 45 minutes in Why a baseline wins budget conversations The three answers to ask your boss for, with a date Why a bad signal is still a good meeting Try this week: pick one idea, write today's number and the metric that would kill it, build one path with fake data, show it to five people who have the problem, and ask your boss for a decision with a date: build more, change one thing, or stop. Next episode: my CEO counts AI features. What now? I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Le Ticket: Being a senior product manager in 2026, lessons from Dust, Payfit and Pennylane (15 February 2026, in French) (https://www.le-ticket.fr/etre-senior-product-manager-en-2026-retours-croises-et-actionnables-chez-dust-payfit-et-pennylane/149021/) Itamar Gilad: Why good product ideas don't survive (24 September 2026) (https://itamargilad.com/good-ideas/) Productowner.nl: National Product Owner Survey 2026 (April 2026, PDF, in Dutch) (https://productowner.nl/app/uploads/2026/04/260410-Nationale-Product-owner-onderzoek-2026-1-1.pdf) Linus Wiggers, Productowner.nl: Product owners and AI (12 October 2026, in Dutch) (https://www.productowner.nl/blogs/product-owner-en-ai/) ProductCraft: The state of product management in Poland 2025 (3 February 2025, in Polish) (https://newsletter.productcraft.pl/p/stan-product-managementu-w-polsce-2025) Product Build Day September tour: Amsterdam, Copenhagen, Stockholm and Berlin (https://productbuildday.com/case-studies/september-tour-2026)

6. 

   16 Oct 2026

   Stop looking for the perfect prompt. Start building, then iterate.

   In Bucharest I had ninety minutes on stage to build an app, test it and fix it, and the room had just voted on what I'd build. My first prompt was everything in my head, dictated in one go, filler words included. It's AI. It will understand you anyway. Say it all once, press the button, and do your thinking with the first version on the screen. What you'll hear: Ninety minutes, two votes, one dictated prompt Where I've watched people wait too long, from Athens to Berlin Why your thinking gets better once something is on the screen The number from 1993 that still decides how fast you improve When planning first is right Try this week: say everything you know about your idea into the tool in one message, dictate it if you can, press the button within ten minutes, then fix one thing per message until a stranger could finish the one path. That's the end of the second week of Product Build Day Podcast. Thank you for listening. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: How to Web 2026, Bucharest, 6 to 8 October (https://www.howtoweb.co/) How to Web agenda 2026: Build & Grow Stage, 7 October (https://www.howtoweb.co/agenda-2026/) Plateful, the prototype built live on stage (https://s.gonogo.design/aTMUk8) The synthetic usability test report from the stage (https://s.gonogo.design/HHm9E7) Jakob Nielsen: Iterative user-interface design (IEEE Computer, November 1993) (https://www.nngroup.com/articles/iterative-design/) Product Build Day Warsaw, July 2026 (https://productbuildday.com/case-studies/warsaw-july-2026) Product Build Day Athens, July 2026 (https://productbuildday.com/case-studies/athens-july-2026) Product Build Day September tour: Amsterdam, Copenhagen, Stockholm and Berlin (https://productbuildday.com/case-studies/september-tour-2026)

7. 

   15 Oct 2026

   The skill that's still rare when everyone can build

   LinkedIn stopped training junior product managers and started training product builders. Its chief product officer at the time, Tomer Cohen, put it in one line: "We're going to teach them how to code, design, and PM at LinkedIn." So if everyone can build now, which skill is still rare? Building fast is the entry ticket. The rare skill is bringing back data from real customers, fast enough and good enough to decide. What you'll hear: What LinkedIn's new program asks for, and how Europe is moving the same way Why building no longer separates teams What people said they learned, in Warsaw, Athens and four September evenings in Amsterdam, Copenhagen, Stockholm and Berlin Four skills, in order: build fast, define the challenge and the metric that would kill it, get the first signals from real people in days, turn the signal into a decision Why fast data is small data Try this week: take one idea through one full day, or one week in small steps: the challenge and the metric, the first version, the usability fix, five real conversations, and one decision sentence.Next episode: stop looking for the perfect prompt. Start building, then iterate. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: [Lenny's Podcast with Tomer Cohen: Why LinkedIn is replacing PMs (4 December 2025)](https://www.lennysnewsletter.com/p/why-linkedin-is-replacing-pms) [Business Insider: LinkedIn is scrapping its associate product manager program (5 December 2025)](https://finance.yahoo.com/news/linkedin-scrapping-associate-product-manager-063508011.html) [LinkedIn job ad: Associate Product Builder, rotational program (expired)](https://jobs.smartrecruiters.com/LinkedIn3/a3b09881-7c3e-444c-9e65-ac0e2c6a8970) [Product Focus: 2026 Survey of the Product Management Profession (677 respondents)](https://cdn.productfocus.com/wp/wp-content/uploads/2026/03/Product-Focus-Industry-Survey-Report-2026.pdf) [Product Focus: Product management, amplified, part 2 (8 April 2026)](https://www.productfocus.com/product-management-amplified-part-2-its-not-just-the-ai-its-the-organisation/) [Spotify Engineering: Spotify's experiments with learning framework (September 2025)](https://engineering.atspotify.com/2025/9/spotifys-experiments-with-learning-framework) [Product Build Day Warsaw, July 2026](https://productbuildday.com/case-studies/warsaw-july-2026) [Product Build Day with Ionian Technologies, Thessaloniki, May 2026](https://productbuildday.com/case-studies/ionian-technologies) [Product Build Day September tour: Amsterdam, Copenhagen, Stockholm and Berlin](https://productbuildday.com/case-studies/september-tour-2026)

8. 

   14 Oct 2026

   Hackathons for people who don't code

   A day of building teaches you the tools. Delivering a better product takes a decision and a test. Inside a company, a hackathon is worth it when it ends with both. What you'll hear: What happens to hackathon projects afterwards What I changed after the first of four September evenings in Amsterdam, Copenhagen, Stockholm and Berlin Products that came out of hackathons that took a year and a half to decide What helps a hackathon project survive inside a company How to design a company hackathon backwards When a day of play is enough Try this week: write a one-page plan for a company build day, backwards from the decision, and send it to the person who decides before you send a single invite. Next episode: Which skills matter now that everyone can build? I'm Marcin Klimaszewski and I run ⁠Product Build Day⁠ (https://s.gonogo.design/vTvyj5). Send me your question on ⁠LinkedIn⁠ (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Hacker News: Are hackathons still worth doing? (19 February 2026) (https://news.ycombinator.com/item?id=47077312) OpenBSD: Hackathons (https://www.openbsd.org/hackathons.html) Devpost: World's Largest Hackathon (2025) (https://worldslargesthackathon.devpost.com/) Michael Matloka: Running hackathons, startup and scaleup edition (30 May 2026) (https://matloka.com/blog/internal-hackathon-playbook) Nolte, Chounta and Herbsleb: What happens to all these hackathon projects? (CSCW 2020) (https://doi.org/10.1145/3415216) TechCrunch: Zuckerberg's letter in Facebook's S-1 (1 February 2012) (https://techcrunch.com/2012/02/01/facebook-ipo-letter/) Atlassian: From ideas to impact, the story of ShipIt (14 January 2025) (https://www.atlassian.com/blog/development/from-ideas-to-impact-the-story-of-shipit) Fast Company: How Facebook designed the like button (15 November 2022) (https://www.fastcompany.com/90780140/the-inside-story-of-how-facebook-designed-the-like-button-and-made-social-media-into-a-popularity-contest) Pe-Than and colleagues: Corporate hackathons, how and why? (Human-Computer Interaction) (https://doi.org/10.1080/07370024.2020.1760869) Product Build Day September tour: Amsterdam, Copenhagen, Stockholm and Berlin (https://productbuildday.com/case-studies/september-tour-2026)

9. 

   13 Oct 2026

   Hand your CPO a better hour

   Your CPO looks after many teams, so your idea gets twenty minutes between two meetings, and the decision happens later, somewhere else. This episode is about another way: your whole team vibe codes a few versions of the solution, you test them, and your CPO comes for the last hour of the day. You leave with a decision in the room, and a team that saw its CPO show up. What you'll hear: Who really sets priorities: only 6% of product people say their roadmap follows a structured framework The three questions every team answered in Product Build Day // Athens Why the people with the most power should arrive once the options exist Why progress you can see is what lifts motivation at work How to run the last hour, and what to do when your CPO won't come Try this week: pick one challenge your team is stuck on and send your CPO an invite for the last hour of a build day: three versions, test results, a decision at the end. Next episode: hackathons used to be for people who write code. Now anyone can build. Are they still worth doing? I'm Marcin Klimaszewski and I run ⁠Product Build Day⁠ (https://productbuildday.com). Send me your question on ⁠LinkedIn⁠ (https://www.linkedin.com/in/marcinklimaszewski/), and it might become an episode. Sources: Product Build Day: Ionian Technologies case study, Thessaloniki (May 2026) (https://productbuildday.com/case-studies/ionian-technologies) ProductPlan: State of Product Management 2026 (https://3434168.fs1.hubspotusercontent-na1.net/hubfs/3434168/SPM26/State%20of%20Product%20Management%202026_Final.pdf) Chip and Dan Heath, Decisive: notes on Paul Nutt's research (https://heathbrothers.com/wp-content/uploads/2013/03/backmatter-1.pdf) Lovallo and Sibony: The case for behavioral strategy (McKinsey Quarterly, March 2010) (https://www.mckinsey.com/capabilities/strategy-and-corporate-finance/our-insights/the-case-for-behavioral-strategy) Amabile and Kramer: The power of small wins (Harvard Business Review, May 2011) (https://hbr.org/2011/05/the-power-of-small-wins)

10. 

    12 Oct 2026

    470 visitors, 3 clicks. Continue or stop?

    "Landing page visitors: 470. Users who took purchase action: 3. Given these metrics, should I continue pursuing this idea?" Someone asked that on Hacker News, and nobody could answer, because the number that would answer it was never written down. This episode is about setting your metrics before the test, so the result gives you a clear decision: invest more, stop, or change one thing and run it again. What you'll hear: Why deciding after the test goes wrong Pick a signal that costs people something Three lines to write before you build Where benchmarks come from, and why 200 views is the minimum for a rough signal How often the best teams are wrong: Microsoft, Booking.com and Supercell Try this week: for your next test, write what you'll invest if it works, the go line, the stop line and the middle. Send them to one colleague before the test goes live. Next episode: your CPO is busy with other teams. How do you get a decision out of them? Hand them a better hour. I'm Marcin Klimaszewski and I run ⁠Product Build Day⁠ (https://s.gonogo.design/vTvyj5). Send me your question on ⁠LinkedIn⁠ (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Hacker News: Should I continue based on my fake door test results? (7 February 2025) (https://news.ycombinator.com/item?id=42968544) Atlassian: The State of Product in 2026 (3 September 2025) (https://www.atlassian.com/blog/announcements/state-of-product-2026) Norton, Mochon and Ariely: The IKEA effect: when labor leads to love (Journal of Consumer Psychology, 2012) (https://doi.org/10.1016/j.jcps.2011.08.002) Kromatic, The Real Startup Book: Fake door test (https://kromatic.com/real-startup-book/2-evaluative-market-experiments/value-proposition-test/fake-door-smoke-test/) Kohavi and colleagues: Online experimentation at Microsoft (2009) (https://exp-platform.com/Documents/ExPThinkWeek2009Public.pdf) HBR Cold Call with Stefan Thomke: At Booking.com, innovation means constant failure (3 September 2019) (https://hbr.org/podcast/2019/09/at-booking-com-innovation-means-constant-failure) Ilkka Paananen, Supercell: The next chapter (15 February 2023) (https://supercell.com/en/news/next-chapter/) Indie Hackers: How do you validate your ideas? (20 September 2025) (https://www.indiehackers.com/post/how-do-you-validate-your-ideas-f4b788e78d)

11. 

    9 Oct 2026

    Can you trust synthetic users?

    "It really felt like you were going through a survey and reading real comments." Someone said that at Product Build Day Stockholm, after their team tested a prototype with synthetic users. More than 100 people ran synthetic tests in my rooms this year. So can you trust synthetic users? There are two questions hiding in that one: can people use it, and do people want it? Synthetic users answer the first one at light speed, and that makes your time with real people worth more. Only real people can answer the second. What you'll hear: The two camps: "fake research" against "the obvious next step" Why 100% task success is a usability result and not a market signal What synthetic users are best at for now, and what they can't do Will synthetic users replace testing with real people? When a mature product needs something else, and why someone has to read the findings with judgment Try this week: test a website you often struggle with using synthetic users. Before you look at the results, write down where you expect them to get stuck. I'm Marcin Klimaszewski and I run ⁠Product Build Day⁠ (https://s.gonogo.design/vTvyj5). Send me your question on ⁠LinkedIn⁠ (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: User Interviews: State of User Research 2025 (10 September 2025) (https://www.userinterviews.com/state-of-user-research-report) uhura: AI personas and synthetic users: fast research or risky illusion? (10 September 2025) (https://www.uhura.de/en/blog/ai-personas-and-synthetic-users-fast-research-or-risky-illusion) Nielsen Norman Group: Synthetic users: if, when, and how to use AI-generated "research" (21 June 2024) (https://www.nngroup.com/articles/synthetic-users/) MeasuringU: A review of experiments with synthetic users (14 April 2026) (https://measuringu.com/review-of-experiments-with-synthetic-users/) Sauer, Braun, Kostic and Krauß: Humans vs. AI: who's the better usability evaluator? (HCI International 2026) (https://link.springer.com/chapter/10.1007/978-3-032-30044-7_9) Product Build Day September tour: Amsterdam, Copenhagen, Stockholm and Berlin (https://productbuildday.com/case-studies/september-tour-2026)

12. 

    8 Oct 2026

    Four people alone had twice the ideas of four together

    "Who produces better ideas: individuals or teams?" Stanford's d.school asks that in its online library of design questions. The usual answer at work is to start together, all in one room. But in a study from Wharton and INSEAD, groups that spent the first ten minutes alone came up with about three times as many ideas in the same half hour, and their best ideas were better. This episode is about why starting alone makes the whole team better, and how to run the part where the team decides together. What you'll hear: The 1957 claim behind brainstorming, and the study where starting together lost Product Build Day Athens: two real challenges, everyone building alone first, then deciding as a team What teams in Copenhagen, Stockholm and Berlin named as the hardest part, and why the time limit helps Four good moves when a team sits down with everyone's ideas Why the test comes first, and why "assumption" scares so many managers Where this breaks: people, and weak facilitation Try this week: pair up with a colleague, build against the same challenge separately, compare what you found, what you built and what you assumed, then build one thing together. Next episode: Can you trust synthetic users? I'm Marcin Klimaszewski and I run ⁠Product Build Day⁠ (https://s.gonogo.design/vTvyj5). Send me your question on ⁠LinkedIn⁠ (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: Stanford d.school library: Who produces better ideas: individuals or teams? (with Robert Sutton) (https://dlibrary.stanford.edu/questions/who-produces-better-ideas-individuals-or-teams) Stanford d.school, Jeremy Utley: To brainstorm better, alternate solo and team work (2 September 2021) (https://medium.com/stanford-d-school/alternate-solo-team-work-eb7431893b42) Korde and Paulus: Alternating individual and group idea generation (Journal of Experimental Social Psychology, 2017) (https://doi.org/10.1016/j.jesp.2016.11.002) Girotra, Terwiesch and Ulrich: Idea generation and the quality of the best idea (Management Science, 2010) (https://doi.org/10.1287/mnsc.1090.1144) Knowledge at Wharton: How group dynamics may be killing innovation (12 May 2010) (https://knowledge.wharton.upenn.edu/article/how-group-dynamics-may-be-killing-innovation/) Diehl and Stroebe: Productivity loss in brainstorming groups (1987), quoting Alex Osborn's 1957 claim (https://doi.org/10.1037/0022-3514.53.3.497) Jake Knapp, John Zeratsky and Braden Kowitz: Sprint (2016) (https://www.thesprintbook.com/) Product Build Day Athens, July 2026 (https://productbuildday.com/case-studies/athens-july-2026) Product Build Day September tour: Copenhagen, Stockholm and Berlin (https://productbuildday.com/case-studies/september-tour-2026)

13. 

    7 Oct 2026

    A prototype is an instrument with an end date

    "Did you really throw everything away, or only the code?" Someone asked that on a French forum, under a post from a developer who vibe coded an app for a month, about 20,000 lines of code, and then threw it all away. AI-built prototypes look finished, so the usual move is to call them version one and keep going. But in Veracode's 2026 report, AI-generated code had an average security pass rate of 56%. This episode is about what a prototype is actually for: learning what's worth building, before a development team builds it for real. What you'll hear: Why the handoff in product discovery is knowledge of what to build Build before you build: vibe code to prove it's worth building, then let a development team build the real thing The four-line contract to put at the top of every prototype When a prototype can do a real job, and when it can't Try this week: before your next build, write the four-line contract: the test, the one path, what it must never hold, and the signal that ends it. Next episode: Four people alone had twice the ideas of four together. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: ⁠LinuxFr: J'ai vibe-codé une appli pendant un mois, puis j'ai tout jeté (11 September 2026)⁠ (https://linuxfr.org/users/mattpiz/journaux/j-ai-vibe-code-une-appli-pendant-un-mois-puis-j-ai-tout-jete) ⁠SweClockers forum thread (29 July 2026)⁠ (https://www.sweclockers.com/forum/trad/1760655-base44-apptillverkare) ⁠Veracode: GenAI Code Security Report (30 July 2025)⁠ (https://www.veracode.com/blog/genai-code-security-report/) ⁠Veracode: 2026 GenAI Code Security Report (28 July 2026)⁠ (https://www.veracode.com/blog/2026-genai-code-security-report-ai-risk/) ⁠WIRED: Thousands of vibe-coded apps expose corporate and personal data on the open web (7 May 2026)⁠ (https://www.wired.com/story/thousands-of-vibe-coded-apps-expose-corporate-and-personal-data-on-the-open-web/) ⁠Security Boulevard: the RedAccess scan of about 380,000 apps (7 May 2026)⁠ (https://securityboulevard.com/2026/05/thousands-of-vibe-coded-apps-exposing-corporate-personal-data-redaccess/) ⁠Product Build Day Warsaw, July 2026 (https://productbuildday.com/case-studies/warsaw-july-2026)

14. 

    6 Oct 2026

    Should product managers learn to vibe code?

    Your boss is probably vibe coding more than you are. In a French survey of 1,031 people in product teams, 29% of CPOs said they use a vibe coding tool, against 12% of product owners. So yes, learn it. The tools take one afternoon. The skill that takes practice is writing the challenge: one or two sentences that tell your team exactly what to vibe code, so you can test four assumptions in one day. What you'll hear: Why your boss is probably ahead of you on vibe coding How to write a challenge you can vibe code against, with the real one from Product Build Day // Stockholm Why one challenge gave us four different apps, and when to write four challenges instead A case study When same-day testing doesn't work, and why a challenge is only the start Try this week: write four challenges for your next idea, one or two sentences each, and vibe code against one of them. Sources: Reddit, r/ProductManagement: How important is vibe-coding for PMs apart from core PM work? (7 July 2026) (https://www.reddit.com/r/ProductManagement/comments/1upi3bc/) Le Ticket: L'IA dans les équipes produit, quel est le vrai état du marché ? (7 September 2025) (https://www.le-ticket.fr/lia-dans-les-equipes-produit-quel-est-le-vrai-etat-du-marche/147596/) Product Build Day Warsaw, July 2026 (https://productbuildday.com/case-studies/warsaw-july-2026) Product Build Day Athens, July 2026 (https://productbuildday.com/case-studies/athens-july-2026) Product Build Day September tour, including Stockholm (https://productbuildday.com/case-studies/september-tour-2026) Ionian Technologies: four ideas, one day, one decision (https://productbuildday.com/case-studies/ionian-technologies) Next episode: A prototype is an instrument with an end date. I'm Marcin Klimaszewski and I run Product Build Day (https://s.gonogo.design/vTvyj5). Send me your question on LinkedIn (https://s.gonogo.design/vKNmKt), and it might become an episode.

15. 

    5 Oct 2026

    You built it. Now try to kill it.

    A startup founder told me they can vibe code faster than their dev team, and they still don't know what to ship. I hear the same question at every conference and in almost every conversation with product managers. When anyone can build a working first version in about five minutes, "it works" stops telling you which idea is worth building. This episode is about finding the one belief your idea can't survive without, and testing it fast, before it costs you money and time. What you'll hear: What makes you different when everyone in the room can build The test that kills it, with a real brief from Product Build Day // Copenhagen Build before you build: synthetic users for usability, The Mom Test interviews, then a fake door How many clicks a fake door needs, and why you write your kill line before you look When "just build it and see" is the right call Try this week: circle the belief that would kill your idea, and write a kill line before you test it. Next episode: should product managers learn to vibe code? I'm Marcin Klimaszewski and I run ⁠Product Build Day⁠ (https://s.gonogo.design/vTvyj5). Send me your question on ⁠LinkedIn⁠ (https://s.gonogo.design/vKNmKt), and it might become an episode. Sources: ⁠⁠Product Focus, 2026 Survey of the Product Management Profession⁠⁠ (https://cdn.productfocus.com/wp/wp-content/uploads/2026/03/Product-Focus-Industry-Survey-Report-2026.pdf) ⁠⁠Eurostat, Labour cost levels by economic activity, 2025⁠⁠ (https://ec.europa.eu/eurostat/databrowser/view/lc_lci_lev/default/table) ⁠⁠Die Produktwerker, episode 340, 24 August 2026⁠⁠ (https://produktwerker.de/product-backlog-priorisierung-wenn-aufwand-nicht-mehr-die-bremse-ist/) ⁠⁠Rob Fitzpatrick, The Mom Test⁠⁠ (https://www.momtestbook.com/) ⁠⁠Kromatic, The Real Startup Book: Fake Door Smoke Test⁠⁠ (https://kromatic.com/real-startup-book/2-evaluative-market-experiments/value-proposition-test/fake-door-smoke-test/) ⁠⁠Product Build Day Warsaw, July 2026⁠⁠ (https://productbuildday.com/case-studies/warsaw-july-2026) ⁠⁠Product Build Day September tour, including Copenhagen⁠ (https://productbuildday.com/case-studies/september-tour-2026)

16. 

    2 Oct 2026

    Welcome to Product Build Day // Podcast!

    Building got cheap. Deciding got hard. This year, over 120 people joined Product Build Day in six European cities to build an idea with AI and test it within one day. A working first version took minutes. The hard part came after: does anyone want this, and how do you find out before you spend a month on it? I'm Marcin Klimaszewski. I run Product Build Day (https://s.gonogo.design/vTvyj5), and in this podcast I answer one question product people keep asking, in about ten minutes, every weekday. In every episode: The question, as it was asked The usual answer, and why it makes sense A moment from one of our build days where that answer broke One thing to try that week Every number comes with a source in the show notes. Topics: product discovery, testing ideas before you build them, vibe coding and prototyping with AI, and getting to a clear decision. Start with episode 1: You built it. Now try to kill it. If there's a question you keep asking yourself, send it to me on LinkedIn (https://s.gonogo.design/vKNmKt). It might become an episode.

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