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

Clona el reproductor vinculado, cambia a chore/jit-bug-composer y ejecuta ./doit2.sh con opcache.jit=tracing habilitado y deshabilitado. Compara los resultados del resolvedor SAT de Composer entre ejecuciones repetidas y, después, rastrea la ruta de PHP OPcache JIT involucrada. Se considera completado cuando entradas idénticas producen una resolución exitosa estable con JIT habilitado, en lugar de un conflicto espurio.