[Backend] backend/src/controllers/sse.controller.ts does not cap the total number of concurrent SSE subscriptions per authenticated user across multiple streams

[grantfox-oss]

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Why this matters

sse.service.ts has a per-IP connection limit (MAX_PER_IP, already flagged elsewhere as env-configurable) but that's IP-scoped, not user-scoped. An authenticated user behind NAT or using multiple devices/tabs could still open an unbounded number of SSE subscriptions across different streams, each held open by the same account, contributing to file-descriptor exhaustion on the server that per-IP limiting alone doesn't fully prevent.

Acceptance criteria

• Add a per-authenticated-user cap on concurrent SSE subscriptions, independent of IP
• Return a clear error (e.g. 429) when the cap is exceeded
• Add a test covering the per-user cap

Files to touch

• backend/src/controllers/sse.controller.ts
• backend/src/services/sse.service.ts

Out of scope

• Changing the existing per-IP limit (tracked separately)
• Building a full connection-quota dashboard

[david87131]

@david87131 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi maintainer Let me work on this issue
I'll definitely give you quick response

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[Luchistack]

@Luchistack has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi Maintainer. i would love to work on this issue.

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[Hollujay]

@Hollujay has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Kindly assign to me.

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[Mikey-222]

@Mikey-222 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

can i work on this

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[drips-wave]

Congratulations, @david87131! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @david87131: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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