refactor(executions): Replace WebSocket execution updates with Server-Sent Events (SSE)

[ABUDIYAAAA]

Execution progress updates are currently delivered over WebSockets.

However, execution events are strictly server → client. The client does not need to continuously send data back to the server over the same connection, making WebSockets unnecessarily complex for this use case.

Migrating to Server-Sent Events (SSE) would simplify the implementation while reducing resource usage and maintenance overhead.

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Problem

WebSockets provide full-duplex communication, but execution monitoring only requires one-way event streaming.

Using WebSockets introduces unnecessary complexity such as:

• WebSocket connection lifecycle management
• Ping/Pong heartbeat handling
• Additional memory usage per active connection
• More complex reconnection logic
• Higher operational overhead for infrastructure that only pushes events

For a feature that only streams execution updates, this is more capability than we actually require.

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Proposed Solution

Replace the execution update transport layer with Server-Sent Events (SSE).

Execution flow would become:

1. Client starts an execution (HTTP)
2. Client opens an SSE stream for that execution
3. Server streams execution lifecycle events
4. Connection closes automatically when execution completes

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Benefits

Reduced Resource Usage

• Lower memory footprint per connection
• Less protocol overhead
• No bidirectional socket management

Simpler Implementation

• Native browser EventSource
• Automatic reconnection
• Plain HTTP endpoint
• Easier debugging using standard HTTP tooling

Better Fit for the Use Case

Execution updates are naturally append-only events flowing from server to client.

SSE is purpose-built for this communication pattern.

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Considerations

• User actions (cancel execution, retry, etc.) should continue using standard HTTP endpoints.
• Existing event payloads should remain unchanged where possible to minimize frontend changes.
• Streaming endpoint should terminate once execution reaches a terminal state.
• Authentication should match existing HTTP authentication middleware.

[ABUDIYAAAA]

@amaan1114 can I work on this?

[amaan1114]

@ABUDIYAAAA Yes yes go for it.