[bug] First-connect failure misreported as 'reconnecting'; retry loop has no cap and no terminal error state

[JZQiang]

Summary

Two related connection-state issues in ConnectionController:

1. First-connect failure is reported as 'reconnecting' — the user has never been connected, yet the UI shows "reconnecting" semantics (should be "cannot connect / connection failed").
2. The retry loop has no cap and no terminal error state — when the backend exits, the page retries forever (500ms → 10s backoff) with only a console.warn as the user-visible error surface.

Evidence

packages/client/connection/src/client/connection.ts:107-168:

private async loop(): Promise<void> {
  while (this.running) {
    ...
    try {
      ...
      this.emitState('connected')          // only on success
      ...
    } catch {
      if (!ac.signal.aborted) ac.abort()
    }

    await failed
    if (!this.isRunning()) return
    this.emitState('reconnecting')         // ← line 163: fires even if never connected
    this.attempt += 1
    console.warn(`[web-runtime] connection lost, retry #${this.attempt}`)
    const idle = new AbortController()
    await sleep(this.backoffDelay(this.attempt), idle.signal)
  }
}

lastState starts as null (line 66) and emitState dedupes only against the previous value (line 172-176), so the very first failure — when the host is not yet ready or already gone — emits 'reconnecting' unconditionally. The UI banner then says "reconnecting" even though a connection never existed.

And nothing stops the loop: no retry ceiling, no 'error'/'failed' state in ConnectionState (only 'connected' | 'reconnecting', line 40). After the backend process exits, the page spins forever with no visible error guidance — the only trace is a browser console.warn.

Suggested fix

• Gate emitState('reconnecting') on this.lastState === 'connected'; if never connected, emit a distinct first-connect failure signal (or extend ConnectionState with 'failed').
• Add a retry ceiling / terminal state so the UI can render an error screen (with a "retry" affordance) instead of an eternal spinner.

Note

The "no visible error when backend exits" part overlaps with an existing discussion; the unique part here is (a) the false reconnecting on first-connect failure and (b) the absence of any terminal failure state in ConnectionState.

Verified at master 47f9438.