## ADDED Requirements

### Requirement: Single polling interval per active session
The SSE infrastructure SHALL maintain at most one active DB polling interval per session, regardless of the number of connected clients.

#### Scenario: First client connects starts polling
- **WHEN** the first client connects to a session's SSE endpoint
- **THEN** a single polling interval SHALL be started for that session

#### Scenario: Additional clients share existing polling
- **WHEN** a second or subsequent client connects to the same session's SSE endpoint
- **THEN** no additional polling interval SHALL be created
- **THEN** the new client SHALL receive events from the shared poll

#### Scenario: Last client disconnect stops polling
- **WHEN** all clients disconnect from a session's SSE endpoint
- **THEN** the polling interval for that session SHALL be stopped and cleaned up