diff --git a/forge/ee/routes/teamBroker/3rdPartyBroker.js b/forge/ee/routes/teamBroker/3rdPartyBroker.js
index 481d9616c6..a1a65f7194 100644
--- a/forge/ee/routes/teamBroker/3rdPartyBroker.js
+++ b/forge/ee/routes/teamBroker/3rdPartyBroker.js
@@ -445,16 +445,30 @@ module.exports = async function (app) {
     }, async (request, reply) => {
         if (request.params.brokerId === 'team-broker') {
             const agent = await app.db.models.TeamBrokerAgent.byTeam(request.team.hashid)
-            if (agent && agent.state !== 'running') {
+            if (agent?.state === 'suspending') {
+                reply.status(409).send({ code: 'agent_suspending', error: 'The Team Broker agent is still suspending, try again shortly' })
+            } else if (agent?.state === 'starting') {
+                // Another start is already launching the agent: starting is a no-op
+                reply.status(200).send({})
+            } else if (agent && agent.state !== 'running') {
                 await app.containers.sendBrokerAgentCommand(agent, 'start')
                 reply.status(200).send({})
             } else if (!agent) {
+                // Stays 'starting' until the driver has launched the agent, so a suspend
+                // arriving meanwhile is refused rather than missing a process it can't stop yet
                 const agent = await app.db.models.TeamBrokerAgent.create({
-                    state: 'running',
+                    state: 'starting',
                     TeamId: request.team.id
                 })
                 await agent.reload({ include: [{ model: app.db.models.Team }] })
-                await app.containers.startBrokerAgent(agent)
+                try {
+                    await app.containers.startBrokerAgent(agent)
+                } catch (err) {
+                    await agent.destroy()
+                    throw err
+                }
+                agent.state = 'running'
+                await agent.save()
                 reply.status(200).send({})
             } else {
                 // Agent already running: starting is a no-op
@@ -509,7 +523,13 @@ module.exports = async function (app) {
     }, async (request, reply) => {
         if (request.params.brokerId === 'team-broker') {
             const agent = await app.db.models.TeamBrokerAgent.byTeam(request.team.id)
-            if (agent) {
+            if (agent?.state === 'starting') {
+                reply.status(409).send({ code: 'agent_starting', error: 'The Team Broker agent is still starting, try again shortly' })
+            } else if (agent) {
+                // Marked before stopping, so a start arriving before the row is removed is refused
+                // rather than treating the agent as already running
+                agent.state = 'suspending'
+                await agent.save()
                 await app.containers.stopBrokerAgent(agent)
                 setTimeout(async () => {
                     await agent.destroy()
diff --git a/test/unit/forge/ee/routes/teamBroker/3rdPartyBroker_spec.js b/test/unit/forge/ee/routes/teamBroker/3rdPartyBroker_spec.js
index 9b3c3ae421..2cf80a3579 100644
--- a/test/unit/forge/ee/routes/teamBroker/3rdPartyBroker_spec.js
+++ b/test/unit/forge/ee/routes/teamBroker/3rdPartyBroker_spec.js
@@ -1,5 +1,7 @@
 const { Op } = require('sequelize')
-const should = require('should') // eslint-disable-line
+const should = require('should')
+const sinon = require('sinon')
+
 const setup = require('../../setup')
 
 const FF_UTIL = require('flowforge-test-utils')
@@ -806,6 +808,91 @@ describe('3rd Party Broker API', function () {
             response.statusCode.should.equal(200)
         })
 
+        it('start keeps a new team-broker agent starting until the driver has launched it', async function () {
+            let stateDuringLaunch
+            const startBrokerAgent = sinon.stub(app.containers, 'startBrokerAgent').callsFake(async () => {
+                stateDuringLaunch = (await app.db.models.TeamBrokerAgent.byTeam(app.team.id)).state
+            })
+            try {
+                const response = await app.inject({
+                    method: 'POST',
+                    url: `/api/v1/teams/${app.team.hashid}/brokers/team-broker/start`,
+                    cookies: { sid: TestObjects.tokens.bob }
+                })
+                response.statusCode.should.equal(200)
+                stateDuringLaunch.should.equal('starting')
+                const agent = await app.db.models.TeamBrokerAgent.byTeam(app.team.id)
+                agent.state.should.equal('running')
+            } finally {
+                startBrokerAgent.restore()
+            }
+        })
+
+        it('start removes the team-broker agent if the driver fails to launch it', async function () {
+            const startBrokerAgent = sinon.stub(app.containers, 'startBrokerAgent').rejects(new Error('launch failed'))
+            try {
+                const response = await app.inject({
+                    method: 'POST',
+                    url: `/api/v1/teams/${app.team.hashid}/brokers/team-broker/start`,
+                    cookies: { sid: TestObjects.tokens.bob }
+                })
+                response.statusCode.should.equal(500)
+                const agent = await app.db.models.TeamBrokerAgent.byTeam(app.team.id)
+                should(agent?.state).be.undefined()
+            } finally {
+                startBrokerAgent.restore()
+            }
+        })
+
+        it('start replies 409 while the team-broker agent is suspending', async function () {
+            await app.db.models.TeamBrokerAgent.create({ state: 'suspending', TeamId: app.team.id })
+            const response = await app.inject({
+                method: 'POST',
+                url: `/api/v1/teams/${app.team.hashid}/brokers/team-broker/start`,
+                cookies: { sid: TestObjects.tokens.bob }
+            })
+            response.statusCode.should.equal(409)
+            response.json().should.have.property('code', 'agent_suspending')
+        })
+
+        it('suspend replies 409 while the team-broker agent is starting', async function () {
+            await app.db.models.TeamBrokerAgent.create({ state: 'starting', TeamId: app.team.id })
+            const stopBrokerAgent = sinon.spy(app.containers, 'stopBrokerAgent')
+            try {
+                const response = await app.inject({
+                    method: 'POST',
+                    url: `/api/v1/teams/${app.team.hashid}/brokers/team-broker/suspend`,
+                    cookies: { sid: TestObjects.tokens.bob }
+                })
+                response.statusCode.should.equal(409)
+                response.json().should.have.property('code', 'agent_starting')
+                stopBrokerAgent.called.should.be.false()
+                const agent = await app.db.models.TeamBrokerAgent.byTeam(app.team.id)
+                agent.state.should.equal('starting')
+            } finally {
+                stopBrokerAgent.restore()
+            }
+        })
+
+        it('suspend marks the team-broker agent suspending before stopping it', async function () {
+            await app.db.models.TeamBrokerAgent.create({ state: 'running', TeamId: app.team.id })
+            let stateDuringStop
+            const stopBrokerAgent = sinon.stub(app.containers, 'stopBrokerAgent').callsFake(async () => {
+                stateDuringStop = (await app.db.models.TeamBrokerAgent.byTeam(app.team.id)).state
+            })
+            try {
+                const response = await app.inject({
+                    method: 'POST',
+                    url: `/api/v1/teams/${app.team.hashid}/brokers/team-broker/suspend`,
+                    cookies: { sid: TestObjects.tokens.bob }
+                })
+                response.statusCode.should.equal(200)
+                stateDuringStop.should.equal('suspending')
+            } finally {
+                stopBrokerAgent.restore()
+            }
+        })
+
         it('suspend replies not_found when there is no team-broker agent', async function () {
             const response = await app.inject({
                 method: 'POST',