JIT causes non-deterministic results in Composer's SAT dependency resolver

Description

When JIT is enabled with opcache.jit=tracing, Composer's dependency resolver (SAT solver) produces non-deterministic results. The same composer update command with identical inputs sometimes succeeds and sometimes fails with a bogus dependency conflict.

Disabling JIT makes the issue disappear completely.

Reproducer:

git clone -b chore/jit-bug-composer https://github.com/sanmai/pipeline.git                                                                                                                                                                                              
cd pipeline                                                                                                                                                                                                                                                             
./doit2.sh                                                                                                                                                                                                                                                              

I'm looking at this error when it fails:

Running pool optimizer.
Updating dependencies
Generating rules
Resolving dependencies through SAT

Dependency resolution completed in 0.615 seconds
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires phpunit/phpunit ^11 || ^12 -> satisfiable by phpunit/phpunit[11.5.50, 12.5.8].
    - phpunit/phpunit[11.5.50, 12.5.8] require staabm/side-effects-detector ^1.0.5 -> satisfiable by staabm/side-effects-detector[1.0.5].
    - Conclusion: don't install staabm/side-effects-detector 1.0.5 (conflict analysis result)

Without JIT, it works like a clock.

PHP Version

PHP 8.5.2 (cli) (built: Jan 16 2026 23:13:28) (NTS)
Copyright (c) The PHP Group
Built by https://github.com/docker-library/php
Zend Engine v4.5.2, Copyright (c) Zend Technologies
    with Zend OPcache v8.5.2, Copyright (c), by Zend Technologies

Operating System

No response

Klone den verlinkten Reproducer, checke chore/jit-bug-composer aus und führe ./doit2.sh mit aktiviertem und deaktiviertem opcache.jit=tracing aus. Vergleiche die Ergebnisse des Composer SAT-Resolvers über wiederholte Ausführungen hinweg und verfolge anschließend den beteiligten PHP OPcache JIT-Pfad. Erledigt ist die Aufgabe, wenn identische Eingaben bei aktiviertem JIT eine stabile erfolgreiche Auflösung statt eines ungerechtfertigten Konflikts erzeugen.