Historical sessions disappear - Expected a string starting with "ses", got "dummy" error

[DANG9185]

Description

Environment:

• opencode version: 1.15.5
• OS: Windows (win32)
• Shell: PowerShell
  Description:
  After upgrading or running opencode, all historical sessions are no longer visible in the UI. The application still functions correctly for new sessions, but the session history is lost.
  Error from log:
  ERROR 2026-05-20T15:48:39 service=server error=Expected a string starting with "ses", got "dummy" cause=Error: Expected a string starting with "ses", got "dummy"
  at (B:/~BUN/root/chunk-b1nng1ye.js:25:10123)
  at (B:/~BUN/root/chunk-b1nng1ye.js:35:4256)
  at (B:/~BUN/root/chunk-gx4g06p1.js:2:107948) {
  [cause]: Error: Expected a string starting with "ses", got "dummy"
  } failed
  Additional Info:
• Database file (opencode.db) is 63MB, suggesting data is still present
• storage/session_diff/ contains 18 session files (from May 13-15)
• New sessions are created successfully after the error
• The error appears to be a session ID validation failure where "dummy" was found instead of a proper "ses_*" format
  Expected Behavior:
  Historical sessions should remain visible and accessible after upgrades/restarts.
  Actual Behavior:
  All historical sessions disappear from the UI, though the database file size indicates data is still present.

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

windows 11

Terminal

Windows Terminal

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Sessions and auth state lost after auto-upgrade from 1.15.0 to 1.15.1 #27859: Sessions and auth state lost after auto-upgrade (similar symptom of session history disappearing after upgrade)
• Upgrading to 1.14.20 looses session history #23814: Upgrading to 1.14.20 loses session history (similar symptom of empty session list after upgrade)
• [Bug] Tauri v1 migration silently discards all historical session data in workspace .dat files #27431: Tauri v1 migration silently discards all historical session data (most similar — session data present in storage but not visible in UI after upgrade)

If your issue is the same root cause, consider adding a comment there instead. If the specific Expected a string starting with "ses", got "dummy" error is distinct from those issues, this report is still valuable — please add any additional reproduction details if possible.