Summary

Fixes a bug in the CLI where delayed IPC messages with partial=true could overwrite completed messages, causing context loss during active sessions.

Problem

Users reported that the CLI "constantly drops context" making it unreliable. The context drops happened randomly during active sessions.

Root Cause

In updateChatMessageByTsAtom, when a delayed IPC message with partial=true arrived after a message had already been completed (partial=false), the stale update would overwrite the completed message:

1. Message completes streaming: {text: "Complete content here", partial: false}
2. Delayed IPC message arrives: {text: "Partial", partial: true}
3. BUG: The stale partial message overwrites the complete one → context lost!

Solution

Added a check in updateChatMessageByTsAtom to prevent stale partial updates from overwriting completed messages:

// BUG FIX: Don't allow stale partial updates to overwrite completed messages
const isStalePartialUpdate = existingMessage.partial === false && updatedMessage.partial === true

if (isStalePartialUpdate && newVersion <= currentVersion) {
    return  // Preserve the completed message
}

Testing

• Added 28 tests specifically for context drop scenarios
• Updated 2 existing tests to reflect correct behavior
• All 260 CLI state atom tests pass

Files Changed

• cli/src/state/atoms/extension.ts - Added the fix
• cli/src/state/atoms/__tests__/extension-context-drop.test.ts - Updated test to verify fix
• cli/src/state/atoms/__tests__/message-reconciliation.test.ts - Updated 2 tests
• cli/src/state/atoms/__tests__/CLI_CONTEXT_DROP_INVESTIGATION.md - Investigation documentation