Gustaf Rosenblad

Passion for Swift and iOS. Full-time Fullstack AI Engineer at @tradera. Part-time doing and other stuff.

Opinions are my own.

[Gustaf Rosenblad @rosecoder]

just fixed 65,000+ warnings/errors to adopt swift strict concurrency in the @tradera ios app. done with @cursor and plenty(!) of agents + subagents. each subagent was focused on a single warning/error.

not by adding main actor to everything, but by actually doing the migration properly.

rolling out to production next week.

[Gustaf Rosenblad @rosecoder]

@ericzakariasson my setup rn with local agents vs cloud agents

[Gustaf Rosenblad @rosecoder]

@da_fant @ericzakariasson @Lovable don't show this to @benln

[Gustaf Rosenblad @rosecoder]

native @cursor_ai – built in swift with cursor cli. performance is design.

[kepano @kepano]

opening files in Obsidian, not sped up — ez

[Gustaf Rosenblad @rosecoder]

fun little holiday refactor

[Tradera @Tradera]

Tech story: We rebuilt our internal feature toggle UI. It looks simple in the screenshot, but hides a lot of targeting and internal logic.

Biggest takeaway: with AI agents, a single developer got this done in under 5 hours.

AI agents are fantastic at handling the “boring” parts of internal tooling.

[Gustaf Rosenblad @rosecoder]

@ericzakariasson @milichab nice! next thing would be having the simulator as a tab in cursor + support for swiftui previews

[Gustaf Rosenblad @rosecoder]

when you are feeling lucky

[Gustaf Rosenblad @rosecoder]

@din0s_ @cursor_ai here you go

[Gustaf Rosenblad @rosecoder]

commit and create a pr is my favourite custom slash commands in @cursor_ai:
- commit: checks out to a feature branch if needed and creates the commit message with a ticket id included
- pr: uses the github cli to create a pr with a title and description based on the commits + context from the agent chat

keeps me locked in

[Gustaf Rosenblad @rosecoder]

@WilliamHolmbe19 just playwright rn

[Gustaf Rosenblad @rosecoder]

day 3: 58 PRs merged to production – still 0 bugs introduced!

now all of the nextjs backend is typescript. looking into components next (around 300 left to do)

855 javascript files when i began. now 560 left.

[Gustaf Rosenblad @rosecoder]

doing another big refactor with @cursor_ai background agents. this time converting all of https://t.co/XCSuJiZXpn to typescript - including all the legacy stuff from 15+ years ago

i guess it will be around 700 PRs in total

goal to complete it within a week with 0 production issues yet again

[Gustaf Rosenblad @rosecoder]

@WilliamHolmbe19 thanks! before each release we ran the basic pipeline with tsc, linting, unit tests and e2e tests. this caught a few issues that the agents missed.

it's been a few weeks now since this was released and still no reports that this migration has caused any bugs in production

[Gustaf Rosenblad @rosecoder]

basic stuff: tsc, linting (with some custom rules to require it to follow our design patterns), unit tests and just a few e2e tests on critical core flows

@cursor_ai bugbot but also human review

the only misstake the agent did was adding inline comments like ”replaced with named export”. we updated the rules and close those PRs and ran it again which fixed it

[Gustaf Rosenblad @rosecoder]

did a workshop session this week where we used @cursor_ai Cloud Agents to refactor away all default exports in the web of @Tradera

all done within 3 hours (300 default exports removed)

1. launch a bunch of agents via the API
2. each agent is in charge of a set of files to refactor
3. PR is created and verification steps are run
4. release to prod

no bugs introduced and all legacy gone

[Gustaf Rosenblad @rosecoder]

@SvenMeyer only @cursor_ai bugbot (with no custom rules) on this one. these PRs was really small and easy to review. i think that was a big deal in making it fast to review

[Gustaf Rosenblad @rosecoder]

hit a new record with +100 PRs in one single day.

almost done with this refactoring. more details coming later this week. (still 0 bugs introduced which is insane!)

my github contributions is ruined though lol

[Gustaf Rosenblad @rosecoder]

doing another big refactor with @cursor_ai background agents. this time converting all of https://t.co/XCSuJiZXpn to typescript - including all the legacy stuff from 15+ years ago

i guess it will be around 700 PRs in total

goal to complete it within a week with 0 production issues yet again

[Gustaf Rosenblad @rosecoder]

@SvenMeyer yup! gpt-5, but simple instructions and a way for the model to run verification steps to iterate helped a lot

[Gustaf Rosenblad @rosecoder]

@WilliamHolmbe19 nice explanation! can’t wait for this to be built into cursor

[Gustaf Rosenblad @rosecoder]

@WilliamHolmbe19 @cursor_ai @Tradera me too! like plan mode but ”build on multiple agents” kind of thing

[Gustaf Rosenblad @rosecoder]

@mattt nice! i had the same thought of building something similar but with focus on swift on server

[Gustaf Rosenblad @rosecoder]

@pontusab torsgatan? 👀