Install demo - error

[PetrovNV]

Installing twig/markdown-extra (v3.0.5): Extracting archive
0 [>---------------------------] 0 [>---------------------------]Package zendframework/zend-code is abandoned, you should avoid using it. Use laminas/laminas-code instead.
Package zendframework/zend-eventmanager is abandoned, you should avoid using it. Use laminas/laminas-eventmanager instead.
Generating autoload files
composer/package-versions-deprecated: Generating version class...
composer/package-versions-deprecated: ...done generating version class
86 packages you are using are looking for funding.
Use the composer fund command to find out more!

symfony-cmd
'symfony-cmd' is not recognized as an internal or external command,
operable program or batch file.
Script symfony-cmd handling the auto-scripts event returned with error code 1
Script @auto-scripts was called via post-install-cmd

[xabbuh]

Which command did you execute? Can you show the full output that you got when doing so?

[PetrovNV]

Which command did you execute? Can you show the full output that you got when doing so?

C:\DEV\PhpstormProjects\Symfony>symfony new --demo demo
* Creating a new Symfony Demo project with Composer
  (running C:\Users\petro\composer\composer.phar create-project symfony/symfony-demo C:\DEV\PhpstormProjects\Symfony\demo)

exit status 1
Creating a "symfony/symfony-demo" project at "./demo"
Installing symfony/symfony-demo (v1.6.2)
  - Installing symfony/symfony-demo (v1.6.2): Extracting archive
Created project in C:\DEV\PhpstormProjects\Symfony\demo
Installing dependencies from lock file (including require-dev)
Verifying lock file contents can be installed on current platform.
Package operations: 110 installs, 0 updates, 0 removals
    0 [>---------------------------]    0 [>---------------------------]  - Installing composer/package-versions-deprecated (1.11.99): Extracting archive
  - Installing symfony/flex (v1.9.6): Extracting archive
The "symfony/flex" plugin was skipped because it is not compatible with Composer 2+. Make sure to update it to version 1.9.8 or greater.
  - Installing symfony/polyfill-php80 (v1.18.1): Extracting archive
  - Installing symfony/deprecation-contracts (v2.2.0): Extracting archive
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  - Installing symfony/http-client-contracts (v2.2.0): Extracting archive
  - Installing psr/event-dispatcher (1.0.0): Extracting archive
  - Installing symfony/event-dispatcher-contracts (v2.2.0): Extracting archive
  - Installing symfony/event-dispatcher (v5.1.7): Extracting archive
  - Installing symfony/var-dumper (v5.1.7): Extracting archive
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  - Installing symfony/error-handler (v5.1.7): Extracting archive
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  - Installing symfony/dependency-injection (v5.1.7): Extracting archive
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  - Installing symfony/polyfill-intl-normalizer (v1.18.1): Extracting archive
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  - Installing doctrine/sql-formatter (1.1.1): Extracting archive
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  - Installing php-cs-fixer/diff (v2.0.1): Extracting archive
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  - Installing twig/twig (v3.0.5): Extracting archive
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  - Installing symfony/twig-bridge (v5.1.7): Extracting archive
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  - Installing symfony/property-access (v5.1.7): Extracting archive
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  - Installing symfony/polyfill-intl-icu (v1.18.1): Extracting archive
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  - Installing symfony/polyfill-intl-idn (v1.18.1): Extracting archive
  - Installing symfony/mime (v5.1.7): Extracting archive
  - Installing egulias/email-validator (2.1.22): Extracting archive
  - Installing symfony/mailer (v5.1.7): Extracting archive
  - Installing nikic/php-parser (v4.10.2): Extracting archive
  - Installing symfony/maker-bundle (v1.21.1): Extracting archive
  - Installing monolog/monolog (2.1.1): Extracting archive
  - Installing symfony/monolog-bridge (v5.1.7): Extracting archive
  - Installing symfony/monolog-bundle (v3.6.0): Extracting archive
  - Installing symfony/phpunit-bridge (v5.1.7): Extracting archive
  - Installing symfony/polyfill-intl-messageformatter (v1.18.1): Extracting archive
  - Installing symfony/security-core (v5.1.7): Extracting archive
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  - Installing symfony/security-bundle (v5.1.7): Extracting archive
  - Installing symfony/translation (v5.1.7): Extracting archive
  - Installing symfony/twig-bundle (v5.1.7): Extracting archive
  - Installing twig/extra-bundle (v3.0.5): Extracting archive
  - Installing symfony/twig-pack (v1.0.0): Extracting archive
  - Installing symfony/validator (v5.1.7): Extracting archive
  - Installing symfony/web-profiler-bundle (v5.1.7): Extracting archive
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  - Installing symfony/webpack-encore-bundle (v1.7.3): Extracting archive
  - Installing symfony/yaml (v5.1.7): Extracting archive
  - Installing tgalopin/html-sanitizer (1.4.0): Extracting archive
  - Installing tgalopin/html-sanitizer-bundle (1.2.0): Extracting archive
  - Installing twig/intl-extra (v3.0.5): Extracting archive
  - Installing twig/markdown-extra (v3.0.5): Extracting archive
    0 [>---------------------------]    0 [>---------------------------]Package zendframework/zend-code is abandoned, you should avoid using it. Use laminas/laminas-code instead.
Package zendframework/zend-eventmanager is abandoned, you should avoid using it. Use laminas/laminas-eventmanager instead.
Generating autoload files
composer/package-versions-deprecated: Generating version class...
composer/package-versions-deprecated: ...done generating version class
86 packages you are using are looking for funding.
Use the `composer fund` command to find out more!
> symfony-cmd
'symfony-cmd' is not recognized as an internal or external command,
operable program or batch file.
Script symfony-cmd handling the auto-scripts event returned with error code 1
Script @auto-scripts was called via post-install-cmd

C:\DEV\PhpstormProjects\Symfony>

[stof]

That's because of the warning here:

The "symfony/flex" plugin was skipped because it is not compatible with Composer 2+. Make sure to update it to version 1.9.8 or greater.

@javiereguiluz it would be great to upgrade symfony/flex in the demo to a version compatible with Composer 2 and make a new release of the demo, given that Composer 2 is now the stable release.