opencode -c hangs indefinitely in directories with no prior sessions #23437

Description

Running opencode -c in a directory that has never had a session causes the TUI to hang. The process becomes unresponsive and must be killed with kill -9.

This worked correctly in 1.4.11 and broke sometime between then and 1.14.18.

Root cause

The --continue flag seeds the router with an initial { type: "session", sessionID: "dummy" } route to prevent a visual flash when resuming a session (introduced in 65b2a10e9 / #23037). When no sessions exist in the directory:

1. The session route component eagerly fetches GET /session/dummy, which fails server-side validation ("dummy" doesn't start with "ses")
2. The createEffect in App() that is responsible for replacing the dummy route with the real most-recent session never fires, because there are no sessions to match against
3. The TUI stays stuck on the broken dummy session screen with no way to recover

Relevant code: packages/opencode/src/cli/cmd/tui/app.tsx lines 151-159 (initial route) and lines 345-366 (continue redirect effect).

Steps to reproduce

1. cd into a directory that has never had an opencode session (e.g. mktemp -d)
2. Run opencode -c
3. TUI hangs indefinitely
4. Process requires kill -9 to terminate

Plugins

None

OpenCode version

1.14.18

Operating System

macOS (Apple Silicon) -- likely affects all platforms

Terminal

Ghostty