Guides
MeloNX Stuck on Waiting for JIT or Crashing? Fixes for JIT Not Acquired, MeloNX Crashed! and Firmware Errors
Key points
- Waiting for JIT and JIT Not Acquired both mean MeloNX didn't get JIT. MeloNX can't run without JIT, so launch it from StikDebug.
- On iOS 26, A15 and newer iPhones and M2 and newer iPads also need a script assigned to MeloNX in StikDebug (universal.js is the recommended one). Without it, JIT never arrives.
- Ignore JIT Popup only skips the waiting screen. It doesn't give you JIT, and games still won't run without it.
- The Entitlement alert means Increased Memory Limit is missing, which every device needs. iPhones under 4GB of RAM and iPads under 8GB also need Extended Virtual Addressing, a paid-account entitlement.
- Key imports need files named exactly prod.keys and title.keys. If firmware import fails, update MeloNX first and make sure keys and firmware match.
- MeloNX's developer previewed a no-JIT mode on 2026-10-30, but it's a demo, not a release. As of 2026-11-01 JIT is still required.
On this page
When MeloNX shows "Waiting for JIT", or its settings say "JIT Not Acquired", it didn't get JIT. MeloNX states it can't run without JIT, so launch it from StikDebug. On iOS 26, A15 and newer iPhones and M2 and newer iPads also need a script assigned to MeloNX in StikDebug (universal.js is recommended). The other common messages: the "Entitlement" alert means Increased Memory Limit is missing. "MeloNX Crashed!" means the game crashed while running; the result text after it tells you more. "Import Keys Failed" and "Installing Firmware Failed" are import errors, usually a wrong file name or mismatched versions. This page covers what MeloNX shows and how to fix it. For the StikDebug side, see the StikDebug JIT guide.
The message text here comes from MeloNX's source as of 2026-08-26 (version 2.6). As of November 1, 2026 the latest release is 2.7 (2026-10-11), which improved firmware import errors, so a few messages may read slightly differently.
MeloNX messages at a glance
| Message | Where | Cause | Fix |
|---|---|---|---|
Waiting for JIT / Waiting for Just-In-Time compilation... | Full-screen page after you open a game | No JIT | Launch from StikDebug; assign a script on iOS 26 TXM devices |
JIT Not Acquired | Top of settings (JIT Enabled when it works) | Same | Same |
Entitlement / MeloNX REQUIRES the Increased Memory Limit entitlement… | At launch or when opening a game | Raised memory limit not granted | Sideload with Impactor, or enable it and reinstall |
Extended Virtual Addressing / The Extended Virtual Addressing entitlement is required for your device… | Same | Low-RAM device needs a paid entitlement too | Enable it with a paid developer account and reinstall |
Increased Memory Limit: Disabled | Settings | Entitlement not active | Same as Entitlement |
MeloNX Crashed! / MeloNX crashed with result: … | After a game crash | Varies | Read the result, then work through the table below |
Missing File / title.keys recommended. Continue at your own risk. | First-run key import | Only prod.keys imported | Safe to continue |
Import Keys Failed | Key import | Wrong file name, invalid file or copy error | See below |
Installing Firmware Failed | Firmware import | Wrong or damaged file, or an old-version bug | Update MeloNX; use matching firmware |
Failed to import / Unsupported file extension | Adding a game | File extension not supported | Use a game file format MeloNX supports |
Waiting for JIT / JIT Not Acquired
You open a game and see this full-screen page:
Waiting for JIT
Waiting for Just-In-Time compilation...
Enabling JIT is required for the emulator to function.
MeloNX checks for JIT every 0.2 seconds on this page and starts the game the moment JIT is on. Tap "Go Back" to leave. If it just sits there, JIT never came through. The status at the top of settings says the same thing: red JIT Not Acquired means no JIT, green JIT Enabled means you have it.
Check in this order:
- Launch MeloNX from StikDebug. Tap Enable JIT in StikDebug and pick MeloNX. Don't open it from the Home Screen icon.
- Assign a script on iOS 26 TXM devices. That's A15 and newer iPhones (including the iPhone 15 Pro and newer that MeloNX recommends) and M2 and newer iPads. In StikDebug's Scripts, long-press
universal.jsand set it as default or assign it to MeloNX. - Keep LocalDevVPN connected, and stay on Wi-Fi.
- Make sure the pairing file is valid. System updates and resets invalidate it, so generate a new one.
- Redo it every launch. JIT ends when MeloNX fully quits. Next time, launch it from StikDebug again.
- MeloNX missing from StikDebug's list? It wasn't sideloaded with an Apple ID, so it lacks the debug entitlement. Reinstall it with an Apple ID sideloading tool.
For StikDebug's own errors (Heartbeat, Device Not Mounted, E96 on iOS 27) and the full walkthrough, see the StikDebug JIT guide.
Ignore JIT Popup doesn't enable JIT
Settings (and per-game settings) have a toggle called Ignore JIT Popup: "Ignores the JIT popup and tries to load the game regardless." It only skips the waiting screen and tries to load the game anyway. It doesn't give MeloNX JIT. MeloNX's README is blunt: "MeloNX REQUIRES JIT and CANNOT run without it." With this on and no JIT, the game still fails to start or crashes. Turn it off while you troubleshoot, since the waiting screen tells you right away whether JIT arrived.
Entitlement: the memory entitlement is missing
Entitlement
MeloNX REQUIRES the Increased Memory Limit entitlement, Please follow the instructions on how to Install MeloNX and Enable the Entitlement.
iOS doesn't give apps enough memory for Switch games by default. MeloNX relies on the Increased Memory Limit entitlement, and every device needs it.
- Recommended: MeloNX recommends sideloading with Impactor on a computer. It requests this entitlement for MeloNX automatically.
- Older method with a paid developer account: in Apple's developer portal, enable Increased Memory Limit for MeloNX under Identifiers (MeloNX's instructions also list Increased Debugging Memory Limit), then delete MeloNX and install it again. The entitlement won't take effect without the reinstall, and settings keep showing
Increased Memory Limit: Disabled. - Afterward, check that MeloNX settings show
Increased Memory Limit: Enabled.
The full sideloading walkthrough is in the iPhone and iPad setup guide.
Extended Virtual Addressing: low-RAM devices need a paid entitlement
Extended Virtual Addressing
The Extended Virtual Addressing entitlement is required for your device, Please read the Information on how to Install MeloNX and Enable the PAID Entitlement.
Per MeloNX's README, iPhones with less than 4GB of RAM and iPads with less than 8GB also need Extended Virtual Addressing. Only a paid developer account can enable it. Turn it on with a paid account and reinstall MeloNX.
MeloNX Crashed!
MeloNX Crashed!
MeloNX crashed with result: …
The "result" is whatever the emulator core returned, so the cause varies. The usual suspects:
| Situation | How to check | Fix |
|---|---|---|
| No JIT, or no script on iOS 26 | Does settings say JIT Not Acquired? | See the JIT section above |
| Memory entitlement not active | Does settings say Increased Memory Limit: Disabled? | See the Entitlement section |
| Keys and firmware don't match, or firmware import was incomplete | Did you recently change keys or firmware? | Re-import keys and firmware from the same version; keys can't be older than the firmware |
| The game doesn't run in MeloNX yet | Check the game's compatibility page | Wait for a MeloNX update or try another device |
| A big game runs out of memory | Is it a large title? | Update to 2.7, which moves game memory into a system extension process to get around the per-app limit |
MeloNX was rebuilt on Ryubing in 2.4, so mismatched keys and firmware crash it for the same reasons as the desktop emulator. See Ryubing errors RYU-0001 to 0003 and MissingKeyException.
Key import errors
| Message | Meaning | Fix |
|---|---|---|
Missing File / title.keys recommended. Continue at your own risk. | You imported prod.keys without title.keys | Safe to continue; add title.keys later if digital games, updates or DLC have trouble |
Import Keys Failed / Only prod.keys and title.keys are supported here. Ignored: … | You picked another file, or the name is off | The name must be exactly prod.keys or title.keys (prod (1).keys and prod.keys.txt won't work) |
Import Keys Failed / Invalid key file format: … | The file isn't a valid keys file | Dump it again from your console |
Import Keys Failed / Failed to copy: … | Copying into MeloNX failed | Pick the file again; if that fails, fully quit MeloNX and retry |
For what keys are and how versions line up, see prod.keys, title.keys and firmware explained.
Installing Firmware Failed
Installing Firmware Failed
(followed by the specific error)
- Update MeloNX first. The 2.5 notes list "Fix crashing when importing firmware" and "Add Firmware & Keys Importing Error Handling". 2.6 fixed firmware importing again, and 2.7 moved the import to a background thread with better errors. Most import problems in old versions go away after updating.
- Import keys before firmware, and keep keys at least as new as the firmware.
- Make sure the file really is firmware and isn't damaged. The error text after the title tells you more.
Version history is in our MeloNX 2.7 release coverage.
No message, it just hangs or drops to the Home Screen
- Drops to the Home Screen when a game opens: usually no JIT. See the JIT section.
- Endless spinner, no progress: confirm keys and firmware are the same version, then update MeloNX.
- Crashes on game launch right after adding firmware: import the firmware again and confirm it succeeded.
More symptoms are in troubleshooting.
Will MeloNX ever work without JIT?
On October 30, 2026, a "MeloNX JITLESS" preview appeared on Reddit's r/EmulationOniOS, and MeloNX developer Stossy11 explained it in the comments. Code is generated ahead of time with the JIT compiler, saved, signed and then run. It uses LiveContainer's JIT-less approach, still needs a signing certificate (a free developer account counts) and can't go on the App Store. He also said it's mostly a demo for now and will ship in a future update.
So as of November 1, 2026, current MeloNX builds still require JIT. We'll update this page once there's an official release. For JIT on iOS 27, see the StikDebug guide. More Apple coverage is on the iOS platform hub.
FAQ
MeloNX is stuck on Waiting for JIT. How do I fix it?
MeloNX didn't get JIT. On that screen it checks every 0.2 seconds and starts the game as soon as JIT is on. Check these: you launched MeloNX from StikDebug; on iOS 26 with an A15+ iPhone or M2+ iPad, universal.js is assigned to MeloNX in StikDebug's Scripts; LocalDevVPN is connected; your pairing file is still valid after any system update. Tap Go Back to leave the screen.
What does JIT Not Acquired mean in MeloNX settings?
This session doesn't have JIT. When it does, the same spot shows JIT Enabled in green. JIT is gone once MeloNX fully quits, so launch it from StikDebug again each time.
Why does MeloNX crash when I open a game?
Most often there's no JIT (on iOS 26, usually a missing script). Next come a missing Increased Memory Limit entitlement, keys and firmware that don't match, an incomplete firmware import, or a game that doesn't run in MeloNX yet. Check the JIT and Increased Memory Limit status in settings, update MeloNX, and re-import keys and firmware from the same version.
MeloNX says it REQUIRES the Increased Memory Limit entitlement. What now?
MeloNX was installed without the raised memory limit, which every device needs. MeloNX recommends sideloading with Impactor, which requests it automatically. With a paid developer account you can also enable Increased Memory Limit for MeloNX in Apple's developer portal, then delete and reinstall MeloNX. Settings should then show Increased Memory Limit: Enabled.
Does Ignore JIT Popup let MeloNX run without JIT?
No. Its description is 'Ignores the JIT popup and tries to load the game regardless.' It only skips the Waiting for JIT screen. MeloNX states it cannot run without JIT, so games still fail or crash with this on.
MeloNX says Import Keys Failed. Why?
Read the line under it. 'Only prod.keys and title.keys are supported here' means the file name is wrong; it must be exactly prod.keys or title.keys. 'Invalid key file format' means the contents are invalid and need a fresh dump. 'Failed to copy' is a copy error, so try again. 'Missing File: title.keys recommended' after importing only prod.keys is safe to continue past.
How do I fix Installing Firmware Failed in MeloNX?
Update MeloNX first. 2.5 fixed a crash when importing firmware and added import error messages, 2.6 fixed firmware importing again, and 2.7 moved the import to a background thread with better errors. Then make sure the file really is firmware, isn't damaged, and that your keys aren't older than it.
Can MeloNX run without JIT now?
Not as of November 1, 2026. MeloNX's developer previewed a no-JIT mode on 2026-10-30: code is generated ahead of time, saved, signed and then run. He said it's mostly a demo for now and will ship in a later update. It still needs a signing certificate and can't go on the App Store.