fix(sse): rotate workspace streams without gaps

[waleedlatif1]

Summary

• Bound workspace SSE connections with make-before-break rotation
• Preserve cache reconciliation for genuine reconnect gaps without refetching on seamless rotations
• Make subscription setup and teardown failure-safe

Type of Change

• Bug fix

Testing

• bun run --cwd apps/sim test -- lib/events/sse-endpoint.test.ts lib/events/rotating-event-source.test.ts hooks/use-mothership-chat-events.test.ts hooks/queries/mcp.test.tsx
• bun run type-check
• bun run lint
• bun run apps/sim/scripts/check-block-registry.ts origin/staging
• bun run check:audits
• Standalone Next.js production-server validation under Bun 1.3.14

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove the fix is effective
• New and existing unit tests pass locally
• My changes generate no new warnings

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Aug 25, 2026 4:24am

[greptile-apps]

Greptile Summary

The PR bounds workspace SSE lifetimes while using make-before-break client rotation to preserve event delivery and reconcile caches after genuine reconnect gaps.

• Adds a reusable rotating EventSource connection that retains the current stream until its replacement opens.
• Updates MCP and mothership chat subscriptions to use rotation-aware reconnect handling.
• Makes SSE subscription setup and teardown failure-safe and adds lifecycle coverage.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
apps/sim/lib/events/rotating-event-source.ts	Introduces rotation-aware EventSource ownership, make-before-break replacement, reconnect classification, and complete disposal.
apps/sim/lib/events/sse-endpoint.ts	Replaces hard expiration with announced rotation and a grace period while making setup and teardown failure-safe.
apps/sim/hooks/queries/mcp.ts	Migrates MCP event subscriptions to the rotating connection and reconciles queries after genuine reconnects.
apps/sim/hooks/use-mothership-chat-events.ts	Migrates mothership chat events to rotation-aware subscriptions while preserving cache reconciliation behavior.
apps/sim/lib/events/rotating-event-source.test.ts	Covers seamless replacement, reconnect classification, disposal during rotation, and replacement-construction failure.
apps/sim/lib/events/sse-endpoint.test.ts	Covers rotation grace behavior and failure-safe subscription setup and teardown.

Sequence Diagram

sequenceDiagram
    participant Client
    participant Old as Current SSE stream
    participant Server
    participant New as Replacement SSE stream
    Server->>Old: rotate event
    Old->>Client: rotation requested
    Client->>New: open replacement connection
    Note over Old,New: Current stream remains active
    New-->>Client: connection opened
    Client->>Old: close current connection
    Client->>New: promote replacement
    alt Current stream dropped before replacement opened
        Client->>Client: classify as reconnect
        Client->>Client: reconcile affected caches
    else Seamless replacement
        Client->>Client: classify as rotation
    end

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[cubic-dev-ai]

1 issue found across 7 files

Confidence score: 4/5

• apps/sim/hooks/queries/mcp.ts can leave the legacy global connection map undiscovered during refresh, causing the hook to open a second workspace SSE stream; preserve or migrate the legacy key and close any stale connection.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="apps/sim/hooks/queries/mcp.ts">

<violation number="1" location="apps/sim/hooks/queries/mcp.ts:546">
P2: During a refresh from the previous implementation, this new key leaves the old global connection map undiscovered, so the hook can open a second workspace SSE stream. Preserve or migrate the legacy key, and close any legacy entries that cannot be reused.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[waleedlatif1]

@greptile