feat: add root-path for opencode web

[DaehoYang]

Summary

This pull request adds robust support for deploying the OpenCode web app behind a reverse proxy at a configurable base path (rootPath). It introduces a new CLI/config option for rootPath, ensures all URLs and static assets are correctly resolved relative to this path, and injects the configuration into the frontend.

related issues:
#7624
#6336
and else...

Changes

Reverse Proxy & Root Path Support

• Added a new rootPath option to CLI (--root-path), config, and network options, allowing the app to be served at a custom base path for reverse proxy scenarios.
• Server startup now requires a local build when rootPath is set, enforcing this with a clear error message if the build is missing.
• All URLs (including those shown in CLI output and used by the frontend) are normalized to respect the rootPath, avoiding duplicate slashes and ensuring correct asset resolution.

Frontend Integration

• Injects the rootPath into the frontend via a <base> tag, a script setting window.__OPENCODE__.rootPath, and a data-root-path attribute on the root div, using the new injectRootPath utility.
• Frontend router and API base URL logic updated to use the injected rootPath, ensuring proper navigation and resource loading.
• Refactored server code to centralize static file serving and index.html handling, with clear separation between local and remote fallback modes.

Testing

git clone https://github.com/DaehoYang/opencode
cd opencode
bun install
cd packages/app
bun run build
cd ../..
bun run dev web --root-path /proxy

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate Found:

• PR feat: base path support #7625: "feat: base path support"
  • feat: base path support #7625

Why it's related: PR #7625 appears to address the same feature (base path support for reverse proxy scenarios). The current PR #11858 is also adding root-path support for deploying OpenCode behind a reverse proxy. These likely overlap in functionality or one may be addressing the same issue from a different branch/approach. You may want to check if #7625 is already merged or if there's work duplication.

[DaehoYang]

Duplicate