diff --git a/server/controllers/websocket/mux.go b/server/controllers/websocket/mux.go
index ccfbdf99f9..8288df3212 100644
--- a/server/controllers/websocket/mux.go
+++ b/server/controllers/websocket/mux.go
@@ -1,6 +1,7 @@
 package websocket
 
 import (
+	"fmt"
 	"net/http"
 
 	"github.com/gorilla/websocket"
@@ -18,6 +19,7 @@ type PartitionKeyGenerator interface {
 type PartitionRegistry interface {
 	Register(key string, buffer chan string)
 	Deregister(key string, buffer chan string)
+	IsKeyExists(key string) bool
 }
 
 // Multiplexor is responsible for handling the data transfer between the storage layer
@@ -51,6 +53,11 @@ func (m *Multiplexor) Handle(w http.ResponseWriter, r *http.Request) error {
 		return errors.Wrapf(err, "generating partition key")
 	}
 
+	// check if the job ID exists before registering receiver
+	if !m.registry.IsKeyExists(key) {
+		return fmt.Errorf("invalid key: %s", key)
+	}
+
 	// Buffer size set to 1000 to ensure messages get queued.
 	// TODO: make buffer size configurable
 	buffer := make(chan string, 1000)
diff --git a/server/handlers/mocks/mock_project_command_output_handler.go b/server/handlers/mocks/mock_project_command_output_handler.go
index fa8fb149b6..926f1ca4b0 100644
--- a/server/handlers/mocks/mock_project_command_output_handler.go
+++ b/server/handlers/mocks/mock_project_command_output_handler.go
@@ -50,6 +50,21 @@ func (mock *MockProjectCommandOutputHandler) Handle() {
 	pegomock.GetGenericMockFrom(mock).Invoke("Handle", params, []reflect.Type{})
 }
 
+func (mock *MockProjectCommandOutputHandler) IsKeyExists(_param0 string) bool {
+	if mock == nil {
+		panic("mock must not be nil. Use myMock := NewMockProjectCommandOutputHandler().")
+	}
+	params := []pegomock.Param{_param0}
+	result := pegomock.GetGenericMockFrom(mock).Invoke("IsKeyExists", params, []reflect.Type{reflect.TypeOf((*bool)(nil)).Elem()})
+	var ret0 bool
+	if len(result) != 0 {
+		if result[0] != nil {
+			ret0 = result[0].(bool)
+		}
+	}
+	return ret0
+}
+
 func (mock *MockProjectCommandOutputHandler) Register(_param0 string, _param1 chan string) {
 	if mock == nil {
 		panic("mock must not be nil. Use myMock := NewMockProjectCommandOutputHandler().")
@@ -193,6 +208,33 @@ func (c *MockProjectCommandOutputHandler_Handle_OngoingVerification) GetCaptured
 func (c *MockProjectCommandOutputHandler_Handle_OngoingVerification) GetAllCapturedArguments() {
 }
 
+func (verifier *VerifierMockProjectCommandOutputHandler) IsKeyExists(_param0 string) *MockProjectCommandOutputHandler_IsKeyExists_OngoingVerification {
+	params := []pegomock.Param{_param0}
+	methodInvocations := pegomock.GetGenericMockFrom(verifier.mock).Verify(verifier.inOrderContext, verifier.invocationCountMatcher, "IsKeyExists", params, verifier.timeout)
+	return &MockProjectCommandOutputHandler_IsKeyExists_OngoingVerification{mock: verifier.mock, methodInvocations: methodInvocations}
+}
+
+type MockProjectCommandOutputHandler_IsKeyExists_OngoingVerification struct {
+	mock              *MockProjectCommandOutputHandler
+	methodInvocations []pegomock.MethodInvocation
+}
+
+func (c *MockProjectCommandOutputHandler_IsKeyExists_OngoingVerification) GetCapturedArguments() string {
+	_param0 := c.GetAllCapturedArguments()
+	return _param0[len(_param0)-1]
+}
+
+func (c *MockProjectCommandOutputHandler_IsKeyExists_OngoingVerification) GetAllCapturedArguments() (_param0 []string) {
+	params := pegomock.GetGenericMockFrom(c.mock).GetInvocationParams(c.methodInvocations)
+	if len(params) > 0 {
+		_param0 = make([]string, len(c.methodInvocations))
+		for u, param := range params[0] {
+			_param0[u] = param.(string)
+		}
+	}
+	return
+}
+
 func (verifier *VerifierMockProjectCommandOutputHandler) Register(_param0 string, _param1 chan string) *MockProjectCommandOutputHandler_Register_OngoingVerification {
 	params := []pegomock.Param{_param0, _param1}
 	methodInvocations := pegomock.GetGenericMockFrom(verifier.mock).Verify(verifier.inOrderContext, verifier.invocationCountMatcher, "Register", params, verifier.timeout)
diff --git a/server/handlers/project_command_output_handler.go b/server/handlers/project_command_output_handler.go
index 44a8e9ca7e..02cb851607 100644
--- a/server/handlers/project_command_output_handler.go
+++ b/server/handlers/project_command_output_handler.go
@@ -81,6 +81,8 @@ type ProjectCommandOutputHandler interface {
 	// Deregister removes a channel from successive updates and closes it.
 	Deregister(jobID string, receiver chan string)
 
+	IsKeyExists(key string) bool
+
 	// Listens for msg from channel
 	Handle()
 
@@ -114,6 +116,13 @@ func NewAsyncProjectCommandOutputHandler(
 	}
 }
 
+func (p *AsyncProjectCommandOutputHandler) IsKeyExists(key string) bool {
+	p.receiverBuffersLock.RLock()
+	defer p.receiverBuffersLock.RUnlock()
+	_, ok := p.receiverBuffers[key]
+	return ok
+}
+
 func (p *AsyncProjectCommandOutputHandler) Send(ctx models.ProjectCommandContext, msg string, operationComplete bool) {
 	p.projectCmdOutput <- &ProjectCmdOutputLine{
 		JobID: ctx.JobID,
@@ -219,12 +228,7 @@ func (p *AsyncProjectCommandOutputHandler) writeLogLine(jobID string, line strin
 		select {
 		case ch <- line:
 		default:
-			// Client ws conn could be closed in two ways:
-			// 1. Client closes the conn gracefully -> the closeHandler() is executed which
-			//  	closes the channel and cleans up resources.
-			// 2. Client does not close the conn and the closeHandler() is not executed -> the
-			// 		receiverChan will be blocking for N number of messages (equal to buffer size)
-			// 		before we delete the channel and clean up the resources.
+			// Delete buffered channel if it's blocking.
 			delete(p.receiverBuffers[jobID], ch)
 		}
 	}
@@ -274,9 +278,6 @@ func (p *AsyncProjectCommandOutputHandler) CleanUp(pullContext PullContext) {
 			delete(p.projectOutputBuffers, jobID)
 			p.projectOutputBuffersLock.Unlock()
 
-			// Only delete the pull record from receiver buffers.
-			// WS channel will be closed when the user closes the browser tab
-			// in closeHanlder().
 			p.receiverBuffersLock.Lock()
 			delete(p.receiverBuffers, jobID)
 			p.receiverBuffersLock.Unlock()
@@ -305,3 +306,7 @@ func (p *NoopProjectOutputHandler) SetJobURLWithStatus(ctx models.ProjectCommand
 
 func (p *NoopProjectOutputHandler) CleanUp(pullContext PullContext) {
 }
+
+func (p *NoopProjectOutputHandler) IsKeyExists(key string) bool {
+	return false
+}