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fix(mcp): harden notification system against race conditions #3168

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Merged
waleedlatif1 merged 8 commits into from
Feb 10, 2026
Merged

fix(mcp): harden notification system against race conditions #3168

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cf25fb0
fix(mcp): harden notification system against race conditions
waleedlatif1 Feb 8, 2026
7c6927d
updated tests
waleedlatif1 Feb 9, 2026
f844e25
plugged in new mcp event based system and create sse route to publish…
waleedlatif1 Feb 9, 2026
ec69103
ack commetns
waleedlatif1 Feb 9, 2026
3de6e3b
fix reconnect timer
waleedlatif1 Feb 9, 2026
4d53e35
cleanup when running onClose
waleedlatif1 Feb 9, 2026
0ba38ce
fixed spacing on mcp settings tab
waleedlatif1 Feb 9, 2026
44ebc51
keep error listeners before quiet in redis
waleedlatif1 Feb 10, 2026
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updated tests
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@waleedlatif1
waleedlatif1 committed Feb 9, 2026
commit 7c6927d6437ccfb6528815d50366836e7ae0a017
2 changes: 0 additions & 2 deletions apps/sim/lib/mcp/client.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -91,8 +91,6 @@ describe('McpClient notification handler', () => {
expect(capturedNotificationHandler).not.toBeNull()

await client.disconnect()

// Simulate a late notification arriving after disconnect
await capturedNotificationHandler!()

expect(onToolsChanged).not.toHaveBeenCalled()
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12 changes: 4 additions & 8 deletions apps/sim/lib/mcp/connection-manager.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,10 @@ function setupBaseMocks() {
}

describe('McpConnectionManager', () => {
let manager: { connect: Function; dispose: Function } | null = null
let manager: {
connect: (...args: unknown[]) => Promise<{ supportsListChanged: boolean }>
dispose: () => void
} | null = null

afterEach(() => {
manager?.dispose()
Expand Down Expand Up @@ -72,17 +75,14 @@ describe('McpConnectionManager', () => {

const config = serverConfig('server-1')

// Fire two concurrent connect() calls for the same server
const p1 = mgr.connect(config, 'user-1', 'ws-1')
const p2 = mgr.connect(config, 'user-1', 'ws-1')

deferred.resolve()
const [r1, r2] = await Promise.all([p1, p2])

// Only one McpClient should have been instantiated
expect(instances).toHaveLength(1)
expect(r1.supportsListChanged).toBe(true)
// Second call hits the connectingServers guard and returns false
expect(r2.supportsListChanged).toBe(false)
})

Expand All @@ -109,11 +109,9 @@ describe('McpConnectionManager', () => {

const config = serverConfig('server-2')

// First connect — server doesn't support listChanged, disconnects immediately
const r1 = await mgr.connect(config, 'user-1', 'ws-1')
expect(r1.supportsListChanged).toBe(false)

// connectingServers cleaned up via finally, so second connect proceeds
const r2 = await mgr.connect(config, 'user-1', 'ws-1')
expect(r2.supportsListChanged).toBe(false)

Expand Down Expand Up @@ -148,11 +146,9 @@ describe('McpConnectionManager', () => {

const config = serverConfig('server-3')

// First connect fails
const r1 = await mgr.connect(config, 'user-1', 'ws-1')
expect(r1.supportsListChanged).toBe(false)

// Second connect should NOT be blocked by a stale connectingServers entry
const r2 = await mgr.connect(config, 'user-1', 'ws-1')
expect(r2.supportsListChanged).toBe(true)
expect(instances).toHaveLength(2)
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