DEV Community: Zlatko Marjanovic

GPT-6 Astra: Pricing, API Access, and What Founders Should Change

Zlatko Marjanovic — Sat, 26 Sep 2026 01:55:23 +0000

OpenAI launched GPT-6 Astra on 3 September 2026. If you ship with agents, the useful questions are pricing, API access, and what still needs a human owner.

Computer-use claims are not a production plan. A model that can click around a desktop still needs auth boundaries, spend caps, and someone who can say no.

What I would change first

Confirm you can actually call gpt-6-astra on the API you already pay for.
Put a budget cap on any computer-use loop before you demo it to a customer.
Keep a human on auth, billing, and anything that can email or pay.

Do not rip out the current model because the changelog is loud. Route one high-value job, measure cost and failure rate, then decide.

The longer founder notes are here: GPT-6 Astra.

If your team is also staring at Cursor's self-hosted machines announcement, I wrote that one too: Cursor Self-Hosted Machines.

Supabase RLS Is Where Vibe-Coded SaaS Starts Getting Dangerous

Zlatko Marjanovic — Sat, 26 Sep 2026 01:54:31 +0000

A vibe-coded Supabase app usually ships with a publishable API key in the browser. That is fine.

It is only fine if every exposed table has RLS on, leftover grants revoked, and policies you have tested as a second user.

Most AI-built apps miss that third part.

The failure mode

Lovable, Bolt, Cursor, and v0 will happily create tables and a client. They will not reliably:

enable RLS on every table the client can see
stop using the service_role key in Vite
write policies that fail closed for anon and authenticated
prove a second account cannot read the first account's rows

The publishable key is not the leak. The open table is the leak.

The five-minute test

Open the live app.
Create two users.
As user B, request user A's rows with the same client the app uses.
If you get data back, you do not have a product. You have a public database.

If service_role or a VITE_ secret is in the bundle, rotate first. RLS cannot save you while that key is public. I wrote that check here: Is your Lovable app leaking the service_role key?

What to do before the next 50 users

Enable RLS. Revoke grants you do not need. Write policies per table. Test as a stranger. Move privileged writes to Edge Functions.

Do not start with a rewrite.

The longer checklist is here: Supabase RLS for vibe-coded SaaS.

Cursor Self-Hosted Machines (My Machines): What Actually Changes

Zlatko Marjanovic — Sat, 26 Sep 2026 01:54:29 +0000

Cursor can now run Cloud Agent tool execution on machines you manage. That is what Self-Hosted Machines (My Machines) actually are.

Inference still lives in Cursor's cloud. The agent loop still lives in Cursor's cloud. Your repo, file edits, and terminal commands can run on your box.

That is the whole product. Most SaaS teams do not need it yet.

Who should care

You should care if Cloud Agents need to touch code that cannot leave your network: customer data in fixtures, private packages, or a locked-down CI image.

You should also care if legal already asked where agent commands execute.

Who should ignore it

If your team is still leaking secrets into the client, skipping RLS, or running Cloud Agents against a public repo with no review, this feature is a distraction.

Self-hosted machines do not fix a leaked service_role key. They do not write your policies. They do not review the PR.

What changes for SaaS teams

Tool execution can sit next to your existing runners.
Model calls still leave the building.
You now have another machine to patch, observe, and rotate credentials on.

Treat it like adding a CI runner that can write to the repo, not like going air-gapped.

I wrote the longer version for SaaS teams deciding whether this is a 2026 infrastructure change or just a changelog item: Cursor Self-Hosted Machines.

If the bigger risk is the database, start here: Supabase RLS for vibe-coded SaaS.

Do Heat Pumps Work in Cold Weather? Yes, If You Size Them Right

Zlatko Marjanovic — Mon, 14 Sep 2026 21:33:14 +0000

This is a republished excerpt. The full guide is Do heat pumps work in cold weather.

Do heat pumps work in cold weather? Yes. Modern cold-climate air source units keep heating well below freezing, and the best of them are rated to produce useful heat below 0 F.

The reputation for failing in the cold comes from older equipment and undersized installs, not from the physics of today's machines.

What actually happens as it gets colder

A heat pump gathers heat from outdoor air. As that air gets colder, two things happen at once: capacity falls and efficiency falls. The unit does not shut off at 32 F. It just has to work harder.

That is why what size heat pump do I need is not a square-foot rule. A Manual J at your design temperature decides whether January feels effortless or miserable.

Backup heat is still a real conversation in the coldest climates. A dual fuel heat pump that hands off to a furnace on the worst nights is a design choice, not a failure.

If you want the operating cost side of this, see heat pump operating cost or run the calculator.

Full guide: https://heatpumpatlasusa.com/guides/do-heat-pumps-work-in-cold-weather/

Are Heat Pumps Worth It? The Honest Answer Depends on Your Fuel

Zlatko Marjanovic — Mon, 14 Sep 2026 21:33:09 +0000

This is a republished excerpt. The full guide is Are heat pumps worth it.

Are heat pumps worth it? Almost always yes if you heat with oil, propane or electric baseboard. It is a genuine question if you heat with cheap natural gas.

The equipment is the same either way. Three variables set the outcome:

The fuel you burn today. A heat pump delivers about three to four units of heat per unit of electricity. That wins easily against expensive fuels.
Your electricity price. A high residential rate erodes the advantage.
Your climate. More cold hours means more runtime, as long as it is a cold-climate unit sized correctly.

Clear yes

Oil, propane, electric resistance, or an air conditioner you were about to replace anyway.

Real question

Cheap gas and mild winters, or a new healthy furnace. In those cases a dual fuel heat pump is often the smarter middle path.

Open heat pump rebates can flip a close case. The federal tax credit cannot. 25C ended for 2026 installs.

Run the heat pump cost calculator with your ZIP before you take a national average seriously.

Full guide: https://heatpumpatlasusa.com/guides/are-heat-pumps-worth-it/

A Free Heat Pump Cost Calculator That Publishes the Losing Cases

Zlatko Marjanovic — Mon, 14 Sep 2026 21:32:33 +0000

This is a republished excerpt. The live model is the heat pump cost calculator.

Most heat pump calculators exist to produce a lead. They always show a saving. That is why homeowners do not trust them.

This one models your ZIP, your fuel, your floor area and only the heat pump rebates we have verified as open. In cheap-gas states it will often say the furnace still wins on running cost. That is the point.

What it returns

Heat pump installation cost as a regional range
Heat pump operating cost against the fuel you burn today
Open rebates only. Reserved programs are labelled and excluded
A 10-year total and simple payback

Electricity prices and climate come from EIA and NOAA. Installed cost is modelled, not a quote. Two contractors bidding the same job routinely differ by 30 percent, so treat the install number as a range to interrogate quotes with.

If you heat with oil, propane or electric resistance, the operating case is usually strong. If you heat with cheap natural gas, run the model before you believe a national average.

Full tool: https://heatpumpatlasusa.com/calculator/

Heat Pump vs Furnace: The Heat Pump Wins in 27 of 51 States

Zlatko Marjanovic — Mon, 14 Sep 2026 21:32:24 +0000

This is a republished excerpt. The state table and method live on HeatPumpAtlasUSA: heat pump vs furnace.

Heat pump vs furnace is the comparison most homeowners actually need, and it is the one most pages refuse to answer honestly. The gas industry says the furnace wins in 36 states. Some heat pump pages say the heat pump always wins. Both are sales copy.

We modelled delivered heating cost for a heat pump against a 90 percent gas furnace in every state with published gas prices. The heat pump wins on running cost in 27 of 51. The furnace still wins where gas is cheap and winters are milder.

What actually decides it

One ratio: your electricity price against your gas price, multiplied by how many cold hours you have.

Oil, propane and electric resistance lose to a heat pump almost everywhere.
Cheap natural gas can still beat a heat pump on the monthly bill.
If you were going to replace the air conditioner anyway, the heat pump does both jobs and the install comparison changes.

A dual fuel heat pump that keeps the furnace for the coldest snaps is the option that ends the argument in a lot of cheap-gas states.

Run your ZIP in the heat pump cost calculator before you take anyone's national average seriously.

Full article: https://heatpumpatlasusa.com/heat-pump-vs-furnace/

Mass Save Heat Pump Rebate in 2026: Amounts, Tiers and the Reservation Rule

Zlatko Marjanovic — Mon, 14 Sep 2026 21:31:47 +0000

This is a republished excerpt. Program amounts, stacking notes and sources live on HeatPumpAtlasUSA: Mass Save heat pump rebate.

The Mass Save heat pump rebate is the easiest high-intent term in this category, and for a reason: Massachusetts is the most mature incentive market in the country. The program has been running long enough that most contractors know the paperwork. That is not true in a lot of other states.

What it pays

Mass Save splits air source projects into two tiers:

Whole-home: the heat pump is the primary heating system, sized to the design load. This is the tier that reaches the upper end, up to about $10,000.
Partial-home: part of the house, often leaving an existing system in place. Lower rebate, cheaper project.

There is also a $500 sizing bonus when a partial-home job is still sized to the full load.

The part people miss

Order of operations beats rebate size. Mass Save generally requires a rebate commitment letter before installation. If the work happens first, the project can be ineligible. Confirm the reservation in writing before you sign a contract.

Massachusetts electricity is expensive, so the seasonal heat pump rate can be worth more over ten years than the one-time check. Ask about the rate at the same time as the rebate.

The federal 25C tax credit is gone for 2026 installs. Mass Save is one of the programs that still moves the math. Verify current funding before you schedule work.

Full article: https://heatpumpatlasusa.com/rebates/mass-save/

Heat Pump Installation Cost in 2026: What US Homeowners Actually Pay

Zlatko Marjanovic — Mon, 14 Sep 2026 21:31:42 +0000

This is a republished excerpt. The full cost tables, state factors and sources live on HeatPumpAtlasUSA: heat pump installation cost.

Heat pump installation cost in the US is not one number. A typical ducted air source system in a 1,800 to 2,200 square foot home runs about $9,500 to $22,000 installed before incentives. A like-for-like replacement that reuses ducts and line sets often lands between $7,000 and $16,000. Cold-climate equipment adds a few thousand more because the outdoor unit is a different class of machine.

Why the range is so wide

The equipment is usually $4,000 to $9,000 of the invoice. The rest is labor, line sets, controls, permit, and whatever the contractor finds. A house with existing ducts, a 200 amp panel and a clear path to the outdoor unit is a straightforward job. A 1920s house with no ducts and a tight electrical panel is not.

The five things that actually move the price:

Ductwork, or the absence of it
Electrical capacity
Line set length and refrigerant work
Cold-climate equipment
Local labor market

Installation cost is only half the decision

A gas furnace replacement is cheaper on day one. A heat pump also replaces the air conditioner, so the fair comparison is furnace plus new AC, plus ten years of fuel. That is why we model heat pump vs furnace state by state instead of publishing a national winner.

The federal 25C heat pump tax credit ended for equipment installed after 2025. State and utility heat pump rebates still matter, but only if the program is actually accepting applications.

If you want a local range, use the heat pump cost calculator. It applies EIA prices, NOAA climate and only the rebates we have verified as open.

Full article: https://heatpumpatlasusa.com/heat-pump-cost/

A small public index for my AI, Webflow, and automation Fiverr gigs

Zlatko Marjanovic — Thu, 10 Sep 2026 15:35:07 +0000

I put together a clean public index for my active Fiverr gigs so the links are easier to crawl, share, and audit.

The current focus is pretty specific:

Webflow and Framer websites
AI SaaS MVPs and web apps
Claude Code, Cursor, Lovable, and vibe-coded app fixes
n8n AI agents and workflow automation
Shopify builds and optimization
Chrome extensions with browser automation
Med spa websites and SEO content

Full index: https://zlatkomarjanovic.github.io/fiverr-gigs/

Fiverr profile: https://www.fiverr.com/zlatkomarjanovi

The index uses clean Fiverr URLs, one page per service, a sitemap, RSS, llms.txt, and basic structured data. Nothing fancy. Just making the services easier for humans and crawlers to understand.

Website Strategy Consultant: What Good Discovery Actually Covers

Zlatko Marjanovic — Mon, 07 Sep 2026 20:59:15 +0000

Good website strategy discovery produces written decisions on audience, offer, architecture, proof, SEO inventory, and CMS, not a moodboard.

Four takeaways

Discovery is a decision set: ICP, offer, IA, proof, SEO inventory, CMS model.
Moodboards can wait until those artifacts exist.
SEO inventory belongs in strategy, not as a post-launch apology.
This role is not a fractional CTO and not a product consultant for authenticated apps.

Full walkthrough: Website Strategy Consultant: What Good Discovery Actually Covers

AI Search Optimization Guide for Service Businesses

Zlatko Marjanovic — Mon, 07 Sep 2026 20:50:35 +0000

Service businesses win AI search by making services, proof, FAQs, and booking pages quoteable and crawlable, not by publishing a SaaS-scale blog.

Four takeaways

Service businesses need four quoteable templates: services, proof, FAQs, booking.
Write the offer the way you say it on a call, in HTML a crawler can fetch.
Keep FAQs as visible content. Do not chase retired Google FAQ rich results.
A citation that cannot start an engagement is an incomplete win.

Full walkthrough: AI Search Optimization Guide for Service Businesses