Task Summary

Move the repo runtime baseline to Node.js 25.9.0 while retaining Node.js 24.x LTS compatibility across local development, install-time validation, CI defaults, Docker, and setup documentation.

Context

The repo currently supports Node 20/22, with .nvmrc files pinned to Node 20.20.1 and install-time validation allowing Node 20 and 22. We want Node.js 25.9.0 to be the default runtime for forward-compatibility testing, while allowing Node.js 24.x LTS as the stable contributor path.

Node.js 25.9.0 release reference: https://nodejs.org/blog/release/v25.9.0
Node.js release schedule reference: https://github.com/nodejs/Release

Scope

Pin root and app Node version files to Node.js 25.9.0 as the default.
Support Node.js 24.x LTS and Node.js 25.9.x in package metadata and install-time validation.
Update the Docker base image to a Node 25.9-compatible image.
Keep CI reading next/.nvmrc through actions/setup-node.
Update environment setup docs with fnm-based Node installation and auto-switching instructions for macOS, Linux, and Windows.
Keep docs text-only with official links and command examples.

Acceptance Criteria

.nvmrc and next/.nvmrc both pin 25.9.0 as the default runtime.
next/package.json engines support Node 24.x LTS and Node 25.9.x.
next/scripts/check-node-version.cjs accepts Node 24.x LTS and Node 25.9.x, and updates its error/help text.
next/Dockerfile uses a Node 25.9-compatible image, preferably node:25.9.0-bookworm-slim if available.
CI continues using next/.nvmrc through actions/setup-node.
documentation/EnvironmentSetup.md explains fnm-based installation and project auto-switching for macOS, Linux, and Windows.
Lockfiles are updated if npm records changed engine metadata.

Subtasks / Checklist

Update Node version files and package metadata.
Update install-time Node version check.
Update Docker base image.
Update environment setup documentation.
Run local validation.

Validation

From next/, verify node -v reports v25.9.0 when using the default .nvmrc.
Run npm ci to confirm the preinstall version gate accepts Node 25.9.
Run npm run lint.
Run npm run test.
Run npm run typecheck.
Run npm run build.
Build the Docker image from next/.

# Task Summary Move the repo runtime baseline to Node.js 25.9.0 while retaining Node.js 24.x LTS compatibility across local development, install-time validation, CI defaults, Docker, and setup documentation. ## Context The repo currently supports Node 20/22, with .nvmrc files pinned to Node 20.20.1 and install-time validation allowing Node 20 and 22. We want Node.js 25.9.0 to be the default runtime for forward-compatibility testing, while allowing Node.js 24.x LTS as the stable contributor path. Node.js 25.9.0 release reference: https://nodejs.org/blog/release/v25.9.0 Node.js release schedule reference: https://github.com/nodejs/Release ## Scope - Pin root and app Node version files to Node.js 25.9.0 as the default. - Support Node.js 24.x LTS and Node.js 25.9.x in package metadata and install-time validation. - Update the Docker base image to a Node 25.9-compatible image. - Keep CI reading next/.nvmrc through actions/setup-node. - Update environment setup docs with fnm-based Node installation and auto-switching instructions for macOS, Linux, and Windows. - Keep docs text-only with official links and command examples. ## Acceptance Criteria - [x] .nvmrc and next/.nvmrc both pin 25.9.0 as the default runtime. - [x] next/package.json engines support Node 24.x LTS and Node 25.9.x. - [x] next/scripts/check-node-version.cjs accepts Node 24.x LTS and Node 25.9.x, and updates its error/help text. - [x] next/Dockerfile uses a Node 25.9-compatible image, preferably node:25.9.0-bookworm-slim if available. - [x] CI continues using next/.nvmrc through actions/setup-node. - [x] documentation/EnvironmentSetup.md explains fnm-based installation and project auto-switching for macOS, Linux, and Windows. - [x] Lockfiles are updated if npm records changed engine metadata. ## Subtasks / Checklist - [x] Update Node version files and package metadata. - [x] Update install-time Node version check. - [x] Update Docker base image. - [x] Update environment setup documentation. - [x] Run local validation. ## Validation - [x] From next/, verify node -v reports v25.9.0 when using the default .nvmrc. - [x] Run npm ci to confirm the preinstall version gate accepts Node 25.9. - [x] Run npm run lint. - [x] Run npm run test. - [x] Run npm run typecheck. - [x] Run npm run build. - [x] Build the Docker image from next/.

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Task: Move repo runtime to Node.js 25.9.0 #526