Summary

Fixes a remote terminal rendering issue where terminal input/output can remain invisible until the user switches terminal tabs. The active terminal viewport now owns a live terminal event subscription in addition to the existing environment-level terminal event store path.

Root Cause

Terminal open/snapshot calls and terminal live events travel through different client paths:

• terminal.open returns the server-side terminal history snapshot.
• subscribeTerminalEvents pushes incremental TerminalEvent updates into the client store.
• TerminalViewport previously depended on the environment-level subscription populating useTerminalStateStore, then rendered from that store.

When the environment-level terminal event path is stale, gated, or otherwise fails to deliver remote events to the store, the server can still receive PTY output and persist history, but the visible xterm does not receive incremental updates. Switching terminal tabs remounts/reopens the terminal and repaints from the snapshot, making the buffered input/output appear all at once.

Changes

• Add a viewport-owned api.terminal.onEvent subscription inside TerminalViewport.
• Filter live terminal events to the active threadId and terminalId before applying them to xterm.
• De-dupe terminal events so the new viewport-owned stream and the existing store-backed stream can both be active without double-writing output.
• Reuse the existing terminal input helper for terminal.write error handling.
• Add browser test coverage proving that output emitted through the viewport-owned terminal event stream is written to xterm.

User Impact

This keeps active remote terminal panes live even when the broader environment terminal event/store path does not update promptly. In the reported Mac-to-Windows remote case, this fixes commands and results not appearing until switching terminal tabs.

Validation

• bun run fmt apps/web/src/components/ThreadTerminalDrawer.tsx apps/web/src/components/ThreadTerminalDrawer.browser.tsx
• bun run test -- src/components/ThreadTerminalDrawer.test.ts
• bun run test -- src/environments/runtime/service.test.ts
• bun run test:browser -- src/components/ThreadTerminalDrawer.browser.tsx
• bun run typecheck
• git diff --check

Also manually tested against a Mac client connected to a Windows remote server matching 0.0.25-nightly.20260515.295; the reporter confirmed terminal updates now appear live instead of only after tab switching.