bug: Users cannot see threads after updating from 0.5.3 to 0.7.1 due to missing engine field in thread.json

[louis-jan]

Description

After upgrading from version 0.5.3 to 0.7.1, users are unable to see their existing threads. This is caused by a missing engine field in the model object within thread.json files.

Steps to Reproduce

1. Use Jan version 0.5.3 and create threads
2. Upgrade to Jan version 0.7.1
3. Open the application
4. Observe that existing threads are not visible

Root Cause

The thread.json file's model object is missing the engine field, which is now required in version 0.7.1. Older thread files from 0.5.3 do not have this field, causing them to fail validation or parsing.

Expected Behavior

• Existing threads from 0.5.3 should remain visible after upgrading to 0.7.1
• The application should handle migration of old thread.json files gracefully
• Missing engine field should either be set to a default value or handled gracefully

Actual Behavior

Threads created in 0.5.3 are not visible in 0.7.1 due to the missing engine field in the model object.

Suggested Fix

Implement a migration script or backwards compatibility check that:

1. Detects thread.json files missing the engine field
2. Sets a default value (e.g., llamacpp) for the engine field
3. Updates the thread.json file accordingly

Impact

• Severity: High
• Affected Users: Anyone upgrading from 0.5.3 to 0.7.1
• Data Loss Risk: Threads are not visible but data may still exist

Environment

• Previous Version: 0.5.3
• Current Version: 0.7.1