`api.midiLoaded.on()` registered after the MIDI is loaded throws "RangeError: Maximum call stack size exceeded" (WebWorker player)

[gabbe]

Is there an existing issue for this?

• I have searched the existing issues

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• I have read CONTRIBUTING.md and, if any AI agent helped draft this issue, AGENTS.md.

AI authorship

AI-assisted (disclosure block included as described in AGENTS.md)

Current Behavior

Note

AI-authored disclosure (alphatab-ai-authored-v1)

Portions of this content were authored by an AI agent. The agent has read
AGENTS.md and the human submitter accepts responsibility for
compliance with the rules in that document.

With the default (WebWorker) player, calling api.midiLoaded.on(handler)
after a score has been loaded and its MIDI generated throws immediately:

RangeError: Maximum call stack size exceeded
    at get loadedMidiInfo (https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/alphaTab.min.js:51:517921)
    at get loadedMidiInfo (https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/alphaTab.min.js:51:517921)
    at get loadedMidiInfo (https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/alphaTab.min.js:51:517921)
    ...

Firefox reports the same recursion with its own wording:

InternalError: too much recursion
get loadedMidiInfo@https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/alphaTab.min.js:51:517906
get loadedMidiInfo@https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/alphaTab.min.js:51:517909
get loadedMidiInfo@https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/alphaTab.min.js:51:517909
...

The same registration made before the first load works, and the handler is
then called on every later loadMidiForScore().

Expected Behavior

Registering a midiLoaded handler at any time should work. Other events
(scoreLoaded, playerReady) accept late registration and immediately hand
the current value to the new handler; midiLoaded should do the same instead
of throwing.

Steps To Reproduce

1. Create the API with the player enabled and load any score:

   const api = new alphaTab.AlphaTabApi(el, {
     player: { enablePlayer: true, soundFont: 'https://cdn.jsdelivr.net/npm/@coderline/alphatab@1.8.4/dist/soundfont/sonivox.sf2' }
   });
   api.tex('\\tempo 120 . 3.3*4');

2. Wait until playerReady has fired (the MIDI is generated and loaded).

3. Run

   api.midiLoaded.on(e => console.log('midi loaded', e));

4. Observe the RangeError above. Repeating step 3 before step 1's load
   instead works.

Link to jsFiddle, CodePen, Project

No response

Version and Environment

[AlphaTab][VersionInfo] alphaTab 1.8.4
[AlphaTab][VersionInfo] commit: 022a45c8e42370f9e12e68949d11eada370da83d
[AlphaTab][VersionInfo] build date: 2026-07-05T14:46:18.224Z
[AlphaTab][VersionInfo] High DPI: 1
[AlphaTab][VersionInfo] Platform: Browser
[AlphaTab][VersionInfo] WebPack: false
[AlphaTab][VersionInfo] Vite: false
[AlphaTab][VersionInfo] Browser: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/152.0.0.0 Safari/537.36
[AlphaTab][VersionInfo] Window Size: 2560x1392
[AlphaTab][VersionInfo] Screen Size: 2560x1440

(also reproduced on Firefox/155.0)

Platform

Web

Anything else?

No response