Dev Tools
React Native and Expo techniques, build-error and crash troubleshooting, and API integrations that help you take Rork-generated code to production quality.
Find the Code That Trips App Store 2.5.2 Before You Submit
If a remote value can change what your app does, Guideline 2.5.2 may apply. Here is where the line actually sits, plus a script that surfaces the risky paths in your repo before submission.
Find the native edits expo prebuild will erase before you upgrade to SDK 57
Expo SDK 57 makes expo prebuild clear and regenerate ios and android by default. Here is how to audit your hand edits first, move them into config plugins, and why 57.0.9 matters for Reanimated apps.
Your lockfile's dev/prod split won't tell you which licenses your app must credit
A record of classifying every dependency in a production project to decide what belongs on an app's license screen, and where the copyleft findings and the actual shipped artifact turned out to disagree.
Switching to Signed URLs Killed My Image Cache — Decoupling expo-image Keys from the URL
Signed URLs rewrite their query string on every expiry, so a URL-keyed cache never hits. Here is how to pin the key with source.cacheKey, what the cache read and write APIs actually return, and what changed when I re-ran the measurements.
Measuring Hermes Bytecode Delta Updates: One Added Module Cost 29x More Than One Changed Line
I measured OTA delta sizes against a 2.4MB Hermes bytecode bundle. Changing one line cost 2,104 bytes; adding one module cost 61,197. The widely repeated advice about stable module IDs turned out to matter least.
The 429s Kept Coming After Recovery: Measuring Retry Jitter Across 2,000 Clients
My backend came back but the 429s did not stop. I rebuilt the scenario in a 2,000-client discrete simulator and measured what plain exponential backoff, delay caps, 10% jitter, and honoring Retry-After cost in seconds — then reran everything with server capacity that degrades under load.
Exactly 20 Characters, Still Rejected: Putting Character Counting Behind One Boundary
Emoji and combining marks make your client and your server disagree about length. I measured four counting methods on Node v22 and found 75.6% of naive truncations split a grapheme and 36.1% produced replacement characters over UTF-8. Here is the shared-module design that fixed it.
When Two-Character Queries Silently Return Nothing: Measuring Japanese Search Indexes in an Expo App
SQLite FTS5's trigram tokenizer returns zero rows for Japanese queries shorter than three characters, without raising anything. I benchmarked linear scan, a bigram inverted index, and FTS5 over a 20,000-item catalog to find the real threshold.
Every Experiment Kept Landing on the Same Devices: Hash Choice and Salt Position, Measured Across a Million IDs
On-device experiment assignment looked fine in isolation, then collapsed the moment two experiments ran side by side. Here is what one million IDs revealed about four hash functions, why the culprit was the concatenation order rather than hash quality, and the implementation I settled on, with the measured numbers.
What Renovate may bump in an Expo app, and what it must never touch
Turning on automated dependency updates in a Rork-generated app also hands Renovate the 123 packages Expo SDK 57 pins. Measured on 2026-07-30, six of them sit a full major version behind npm latest. Here is how to generate the ignore list from the SDK instead of maintaining it by hand.
Counting what prebuild --clean will erase before you upgrade to Expo SDK 57
A raw diff between two generated ios/ trees showed 649 changed lines; only 3 were real edits. How to count what prebuild --clean erases, and move it into a config plugin.
When to Raise Your Minimum iOS Version — Count Leftover Branches, Not User Percentages
Judging a minimum OS bump by usage share produces the same answer every year, so the decision never happens. Here is the annotation convention, the sweep script that counts how many iOS and Android branches each candidate floor would retire, and what to watch for 30 days after.
What Filtering Out Prerelease OS Devices Cost Me — Separating Telemetry Tracks Instead of Dropping Them
Filtering prerelease OS devices out of telemetry left me with no warning signs on GA day. Here is the rebuild: an os_track dimension, a remote GA baseline, split alert thresholds, and a release gate that separates blockers from fixes.
Collapsing Duplicate Requests Into One: A Reference-Counted Single-Flight Layer
When several components fire the same API call at launch, you get a burst of identical requests. Here is a single-flight layer that shares one in-flight promise instead: how to build the key that decides the folding, the trap of handing out a failed promise forever, the trap of one caller's abort cancelling everyone, and the test that keeps it all from regressing, with the real network numbers alongside.
Resolving App Config in Three Layers: Merging Defaults, User, and Remote With Bounded Overrides
A single type-safe layer that merges compiled defaults, user preferences, and remote config. So a broken remote value never takes your app down, each key gets its own override strength, plus schema validation and range clamping, built from a real production incident.
When Rork Max's Two-Click Submit Stalls, Tell Which Layer Broke
Rork Max's one-click install and two-click submit fold the complexity of iOS shipping into four hidden layers. When the abstraction leaks and your submission stalls, this map helps you tell which layer failed and fix it yourself.
Stop Spinning Up a Separate Server: Colocate Your Backend With Expo Router API Routes
Standing up yet another Worker just to receive a RevenueCat webhook gets old fast. Expo Router API Routes let you put the backend inside the same repo as your app. Here is the implementation, from signature verification to picking a deployment target.
The Generated Screen That Quietly Jams at AX5 and in German — Putting Layout Resilience Checks on Rork Max SwiftUI
A record of running every Rork Max generated SwiftUI screen through pseudolocalization and the largest text size to find exactly where it jams. Covers when to reach for ViewThatFits, ScaledMetric and layoutPriority, plus the snapshot checks that catch regressions every time you regenerate.
Your AR Furniture Is Gone by Morning — Persisting Placements with ARWorldMap
AR apps generated by Rork Max lose every placed object on relaunch. Here is the design that fixes it: when to save an ARWorldMap, how to encode custom anchors, how to handle the relocalization wait, and what to do when relocalization simply never lands.
Shipping Notifications Without Asking First — Provisional Authorization in Rork Apps, and the Expo Snippet That Quietly Undoes It
iOS lets you start delivering notifications with no permission dialog at all, via provisional authorization. The catch: expo-notifications reports granted as false for provisional devices, so the registration snippet in Expo's own docs re-requests permission and fires the very dialog you were avoiding. Here's why granted lies, a hook that models authorization as five states, how to write notifications for quiet delivery, when to ask for the upgrade, and how to keep provisional out of your CTR.
The Update That Failed Because a Profile Expired Three Months Ago
Apple signing assets expire quietly and nothing tells you. Here is how to count the days left with the App Store Connect API and put the audit on a weekly Cloudflare Workers cron.
Killing the Export Compliance Prompt in Rork Builds for Good
Every Rork and Rork Max build lands in App Store Connect with a Missing Compliance warning. Here is how to decide whether you qualify for the exemption, and how to set it once in app.json or Info.plist so the question never returns.
Regenerable Zones in Rork Max Code: Keeping the Freedom to Rebuild
Generated code carries an invisible asset: the option to throw it away and rebuild it. Every hand edit quietly expires that option. Here is how I track it with a ledger and CI checks across six live apps.
Test Generated Purchase Code Before You Touch Sandbox — Automating Refunds, Expiration, and Failures with SKTestSession
Rork Max generates StoreKit 2 code that proves people can buy. It does not prove refunds, expiration, or failed purchases are handled. Here is how to cover those paths with SKTestSession before you ever open Sandbox.
A Yellow Warning in Dev, a Crash on Resume — Functions in Route Params
Rork generated navigation code that put a function and a Date into route params. In development it was only a warning. After the OS reclaimed the process, resuming the app crashed with params.onFavorite is not a function. Here is the cause and the fix.
The Comma That Fell to the Start of a Line: Rork, Quote Cards, and Japanese Line Breaking
React Native's Text component does not guarantee Japanese line-breaking rules. Here are the violation rates I measured, a WORD JOINER implementation that survives copy and VoiceOver, an onTextLayout audit harness, and how Rork Max (SwiftUI) differs.
Half the Bytes, the Same Wait: What AVIF Actually Cost My Wallpaper Apps
Switching to AVIF cut my transfer bill in half and did nothing for perceived speed. Here is the transfer-versus-decode breakdown, the Accept-negotiation trade-off, per-device fallback tiers, and the staged migration order that finally worked across six apps.
My Rork sleep timer faded out on time — but the sound didn't
Rork writes sleep-timer fades against the wall clock with setInterval. The numbers say 30 minutes, but the real audio fades early or cuts out abruptly. Here is how to drive the fade from the actual playback position, why a logarithmic curve sounds natural, and the honest limit of JS fades when the screen is locked.
Designing Seams That Survive AI Regeneration in Rork
Every follow-up prompt to Rork can quietly wipe out logic you wrote by hand. Protecting it with prompts is a patch, not a fix. Here is how to separate generated code from code you own, and draw a boundary that regeneration cannot reach, with working Zustand and service-layer examples.
Adding a Single Zod Validation Boundary to Rork's Generated Fetch Code
The network code Rork generates implicitly trusts the shape of the response. When the API shifts, the screen quietly goes blank. Here is how to slip a single Zod parse layer between the generated UI and the network to make failures predictable, with numbers from real operation.
postMessage Is Fire-and-Forget — Designing a Correlated Request/Response Bridge Between a WebView and React Native
postMessage between a WebView and React Native is one-way, so you never learn whether the work you asked for actually succeeded. Here is a typed request/response bridge, with correlation IDs and timeouts, built in working TypeScript.
When "{n} items" Breaks Across Languages — Designing Quantity Strings with CLDR Plural Categories and Intl.PluralRules
The assumption that one is singular and everything else is plural falls apart in Russian and Arabic. Here is how to hold the CLDR plural categories as a map and render quantities correctly with Intl.PluralRules and i18next, drawn from localizing an indie wallpaper app into sixteen languages.
Your Detox and Maestro E2E Suite Was All Green — but the Retries Were Hiding a Flaky Test That Crashed in Production
Your E2E suite is green, yet production still crashes. The culprit: auto-retries quietly swallowing flaky failures. Field notes on measuring per-test flake rate, quarantining, and keeping only real failures as release gates.
Losing HealthKit Data on Incremental Sync — Designing HKQueryAnchor Persistence
When step or sleep data double-counts or goes missing on incremental HealthKit sync, the root cause is usually HKQueryAnchor persistence. Here is a working Swift design that handles newAnchor and deletedObjects correctly and stays consistent across reinstalls and background updates.
A symbolEffect Field Memo: Making Icons Move Nicely in Your Rork Max App
Animate SF Symbols in a Swift app generated by Rork Max using bounce, pulse, variableColor, and contentTransition, with working code, OS-version gating, and the mistakes I made from over-animating.
Undo That Jumps to the Wrong Place — Designing Edit History You Can Trust
Snapshotting the whole state on every edit crushes memory after a few dozen steps. Here's an undo/redo built on command history plus snapshots, with coalescing, a depth cap, and cross-session persistence, in working TypeScript.
Implementing App Clips with Rork Max — delivering the core of your app the moment someone scans a code
Building on the native Swift that Rork Max produces, this note walks through the 15 MB App Clip budget, receiving the launch URL, and handing state off to the full app.
The Device Clock Can Be Moved — Protecting Daily Features and Trial Logic from Time Tampering
Advancing the device clock by one day was enough to claim tomorrow's daily wallpaper today. Starting from that log entry, this article lays out a three-layer time model — wall clock, monotonic clock, server time — and shows how to build daily-reward and trial logic that survives clock rollbacks.
When Sentry Burned Through Its Event Quota in Days — Trimming Noise Before It Ships
A Sentry quota that empties early in the month is almost always a noise problem, not an error surge. Here is how to shrink event volume before it ships — with beforeSend, sampling, and grouping — while keeping the errors that actually matter inside the quota.
Verifying StoreKit 2 Signed Transactions in a Cloudflare Worker
If you trust whatever the device says about its purchase state, a tampered entitlement walks right through. This walks through verifying StoreKit 2 signed transactions (JWS) in a Cloudflare Worker so you grant entitlements without trusting the client, with working code.