composer.json discovery fails in VS Code remote

In my (admittedly specific) use case the plugin is unable to find composer.json, which is plainly present in the root of the workspace.

Environment

Running VS Code with a devcontainer in Rancher Desktop. Prettier plugin is running inside the container.
prettier and @prettier/plugin-php are installed locally inside node_modules and the VS Code plugin uses the local installation.

Settings:
"phpVersion": "composer"

Filesystem layout:

• /workspaces/myproject/
  • composer.json
  • .prettierrc
  • node_modules/
  • src/
    • a.php

Result

When run on src/a.php through VS Code, the plugin fails.

["ERROR" - 9:22:26 AM] Error formatting document.
["ERROR" - 9:22:26 AM] Could not determine PHP version from composer; Could not find composer.json
Error: Could not determine PHP version from composer; Could not find composer.json
    at resolvePhpVersion (file:///workspaces/myproject/node_modules/@prettier/plugin-php/src/options.mjs:95:13)
    at Object.parse (file:///workspaces/myproject/node_modules/@prettier/plugin-php/src/parser.mjs:11:3)
    at parse5 (file:///workspaces/myproject/node_modules/prettier/index.mjs:16731:24)
    at async coreFormat (file:///workspaces/myproject/node_modules/prettier/index.mjs:17287:25)
    at async formatWithCursor (file:///workspaces/myproject/node_modules/prettier/index.mjs:17504:14)
    at async Module.format2 (file:///workspaces/myproject/node_modules/prettier/index.mjs:19051:25)

When doing the same thing through the CLI, not the VS Code plugin, everything works as expected.

Cause

A little bit of digging turns up the root cause here: https://github.com/prettier/plugin-php/blob/0c883a49850281077218007322f6149f853b2015/src/options.mjs#L23

In my environment, prettier is run in this directory: /vscode/vscode-server/bin/linux-x64/360a4e4fd251bfce169a4ddf857c7d25d1ad40da
The recursive search for composer.json upwards from process.cwd() fails.

I don't feel qualified to suggest a solution but maybe search from the target file's location upwards, instead of the process' working dir?

Start with src/options.mjs at the composer.json search referenced in the issue, then trace how src/parser.mjs passes the PHP file context. Reproduce the difference between the CLI and VS Code remote environment and verify that formatting src/a.php can discover the workspace-root composer.json while preserving existing CLI behavior.