plugins: exact-spec install succeeds but TUI reports "Invalid V2 TUI plugin module" - non-exact specs fail reconciliation and the runtime package tree is never materialized #58045

Summary

Two related defects in the v2 plugin pipeline compound so that a successfully
installed TUI plugin never loads, and the TUI masks the real cause with the
generic Invalid V2 TUI plugin module error:

1. OpenCode's vendored npm resolution (prepare stage) fails with
   NpmInstallFailedError for tag/range specs (bare package name, @latest,
   ^x.y.z ranges in the config-root package.json) on a plugin whose peer
   dependency graph is resolvable — opencode plugin add <name>@<exact-version>
   succeeds with the identical release.
2. When the configured cli.json spec is a pinned version ([email protected]) but
   reconciliation keeps failing, no runtime package tree is materialized for
   that spec key, and the failed import is surfaced as
   Invalid V2 TUI plugin module: <name>@<version> with no underlying error,
   so it looks like a plugin-authoring problem when it is not.

Environment

• opencode version: v2.1.2 (channel: latest)
• OS: Windows 11 (10.0.26300), win32 x64
• Terminal: xterm-256color
• Shell: pwsh 7 / cmd.exe
• Install/channel: latest release, shared background service
• Active plugins: opencode-subagent-statusline (loads fine), [email protected] (fails), one local TUI plugin file under ~/.config/opencode/tui-plugins/

Reproduction

1. Configure a TUI plugin in cli.json: {"plugins": ["[email protected]"]}.
2. opencode plugin add opencode-sdd-engram-manage (bare/tag spec) → fails 100% of the time with
   NpmInstallFailedError (vendored @npmcli/arborist: unable to resolve dependency tree).
3. opencode plugin add [email protected] (exact spec) → succeeds, writing a complete install
   (plugin + all 5 peers) to ~/.cache/opencode/npm/[email protected]/<generation>/.
4. Start the TUI: the plugins list shows Status: failed — Invalid V2 TUI plugin module: [email protected].
5. Observe the cache state:
   • ~/.cache/opencode/packages/[email protected]/ — does not exist
   • ~/.cache/opencode/packages/opencode-sdd-engram-manage@latest/ — complete tree (unused; key does not match the cli.json spec)
   • ~/.config/opencode/node_modules/opencode-sdd-engram-manage/ — module present, peer deps missing
     (plain node import throws ERR_MODULE_NOT_FOUND: Cannot find package '@opentui/solid')
6. Logs (~/.local/share/opencode/log/opencode.log): repeated
   plugin operation failed ... error=NpmInstallFailedError target=opencode-sdd-engram-manage stage=prepare
   on every TUI/startup preparation.

The module itself is healthy: importing the complete npm-cache generation tree
under node 24 (import plugin dist/tui.js) succeeds, and the default export has
the expected TUI plugin shape ({ id, tui }).

Expected Behavior

• Tag/range plugin specs should reconcile like exact specs when the peer graph is resolvable (plain npm 11/12 resolves the same graph in ~16 s).
• After a successful opencode plugin add [email protected], the TUI runtime should have a working install for the configured spec — or reuse the complete generation — instead of failing to load.
• A failed plugin-module load should surface the underlying cause (e.g. ERR_MODULE_NOT_FOUND: '@opentui/solid') instead of the generic Invalid V2 TUI plugin module message, which points plugin authors at the wrong layer.

Actual Behavior

Plugin marked failed with Invalid V2 TUI plugin module: [email protected];
no error chain reaches the UI or the log; the complete install created by
plugin add sits unused because its cache key does not match the configured
spec, and no runtime tree exists under the pinned key.

Additional Context

• Plugin: [email protected] (latest published version). Peers:
  @opencode-ai/plugin >=1.17.11, @opentui/core|keymap|solid >=0.4.2 <1, solid-js 1.9.12.
• Workaround confirmed by hand: copy the complete packages/…@latest tree (or the
  completed npm cache generation) to packages/[email protected],
  then run plain npm install in ~/.config/opencode so the config-root project is
  consistent — after that, module imports succeed and the plugin prepares without
  NpmInstallFailedError warnings.
• Frequency: deterministic, reproduced on every TUI start and every bare/tag
  plugin add across multiple sessions and days.