diff --git a/src/main/orcad/orcad-terminal-census.test.ts b/src/main/orcad/orcad-terminal-census.test.ts
index b2465d47902..c70ee02ba32 100644
--- a/src/main/orcad/orcad-terminal-census.test.ts
+++ b/src/main/orcad/orcad-terminal-census.test.ts
@@ -19,6 +19,7 @@ describe('orcad terminal census', () => {
       liveSessions: 3,
       startedSinceActivation: 2,
       daemonProtocolVersion: 7,
+      daemonProtocolVersions: [7],
       inProcessSessions: 0
     })
   })
@@ -34,18 +35,22 @@ describe('orcad terminal census', () => {
       liveSessions: 0,
       startedSinceActivation: 0,
       daemonProtocolVersion: null,
+      daemonProtocolVersions: [],
       inProcessSessions: 0
     })
   })
 
-  it('leaves the protocol unknown when sessions span daemon generations', async () => {
+  it('names every daemon generation when sessions span them', async () => {
     const census = await collectOrcadTerminalCensus(
       0,
-      async () => [session(1, 7), session(2, 6)],
+      async () => [session(1, 7), session(2, 6), session(3, 7)],
       async () => 0
     )
-    expect(census.daemonProtocolVersion).toBeNull()
-    expect(census.liveSessions).toBe(2)
+    expect(census).toMatchObject({
+      liveSessions: 3,
+      daemonProtocolVersion: null,
+      daemonProtocolVersions: [6, 7]
+    })
   })
 
   it('leaves the since-activation count unknown when a session has no creation time', async () => {
@@ -85,6 +90,7 @@ describe('orcad terminal census', () => {
       liveSessions: 1,
       startedSinceActivation: null,
       daemonProtocolVersion: null,
+      daemonProtocolVersions: [],
       inProcessSessions: 1
     })
   })
diff --git a/src/main/orcad/orcad-terminal-census.ts b/src/main/orcad/orcad-terminal-census.ts
index f10e733e34e..1629f2b4ed8 100644
--- a/src/main/orcad/orcad-terminal-census.ts
+++ b/src/main/orcad/orcad-terminal-census.ts
@@ -31,8 +31,9 @@ export async function collectOrcadTerminalCensus(
   const timestampsKnown = sessions.every(
     (session) => Number.isFinite(session.createdAt) && session.createdAt > 0
   )
-  const protocols = new Set(sessions.map((session) => session.protocolVersion))
-  const [protocol] = protocols
+  const protocols = [...new Set(sessions.map((session) => session.protocolVersion))].sort(
+    (a, b) => a - b
+  )
   return {
     liveSessions: sessions.length + inProcess,
     // Fallback terminals lack creation times, so activation-relative counts remain unknown.
@@ -40,8 +41,9 @@ export async function collectOrcadTerminalCensus(
       timestampsKnown && inProcess === 0
         ? sessions.filter((session) => session.createdAt >= activatedAt).length
         : null,
-    // Mixed daemon generations cannot establish one protocol owner for build compatibility.
-    daemonProtocolVersion: protocols.size === 1 && protocol !== undefined ? protocol : null,
+    // Older desktops read only the scalar, which cannot name mixed generations.
+    daemonProtocolVersion: protocols.length === 1 ? protocols[0] : null,
+    daemonProtocolVersions: protocols,
     inProcessSessions: inProcess
   }
 }
diff --git a/src/main/ssh/orcad-daemon-protocol-crossing.ts b/src/main/ssh/orcad-daemon-protocol-crossing.ts
index 5dd5653ccef..6517234a21b 100644
--- a/src/main/ssh/orcad-daemon-protocol-crossing.ts
+++ b/src/main/ssh/orcad-daemon-protocol-crossing.ts
@@ -26,10 +26,18 @@ export function orcadBuildCanAttachDaemon(
 }
 
 export type OrcadLiveDaemonCrossing =
-  | 'no-live-terminals'
-  | 'attachable'
-  | 'strands-live-terminals'
-  | 'unverifiable'
+  | { state: 'no-live-terminals' }
+  | { state: 'attachable' }
+  | { state: 'strands-live-terminals'; unattachable: readonly number[] }
+  | { state: 'unverifiable' }
+
+/** Hosts predating the protocol set report only a single-generation scalar. */
+function liveDaemonProtocols(census: OrcadTerminalCensus): readonly number[] | null {
+  if (census.daemonProtocolVersions !== undefined) {
+    return census.daemonProtocolVersions
+  }
+  return census.daemonProtocolVersion === null ? null : [census.daemonProtocolVersion]
+}
 
 /** An unknown session count or daemon protocol is planned for as live and unattachable. */
 export function assessOrcadLiveDaemonCrossing(
@@ -37,12 +45,21 @@ export function assessOrcadLiveDaemonCrossing(
   incoming: OrcadDaemonProtocolFacts
 ): OrcadLiveDaemonCrossing {
   if (census.liveSessions === 0) {
-    return 'no-live-terminals'
+    return { state: 'no-live-terminals' }
   }
-  if (census.daemonProtocolVersion === null) {
-    return 'unverifiable'
+  const protocols = liveDaemonProtocols(census)
+  if (protocols === null || protocols.length === 0) {
+    return { state: 'unverifiable' }
   }
-  return orcadBuildCanAttachDaemon(incoming, census.daemonProtocolVersion)
-    ? 'attachable'
-    : 'strands-live-terminals'
+  // Every generation must stay reachable; one unattachable daemon strands its terminals.
+  const unattachable = protocols.filter(
+    (protocol) => !orcadBuildCanAttachDaemon(incoming, protocol)
+  )
+  return unattachable.length === 0
+    ? { state: 'attachable' }
+    : { state: 'strands-live-terminals', unattachable }
+}
+
+export function describeDaemonProtocols(protocols: readonly number[]): string {
+  return protocols.length === 1 ? `protocol ${protocols[0]}` : `protocols ${protocols.join(', ')}`
 }
diff --git a/src/main/ssh/orcad-update-plan.test.ts b/src/main/ssh/orcad-update-plan.test.ts
index b476a7b54fb..a4f85337df8 100644
--- a/src/main/ssh/orcad-update-plan.test.ts
+++ b/src/main/ssh/orcad-update-plan.test.ts
@@ -291,6 +291,49 @@ describe('D7 daemon protocol crossing', () => {
     })
   })
 
+  const mixed = (daemonProtocolVersions: number[]) => ({
+    liveSessions: 80,
+    startedSinceActivation: 0,
+    daemonProtocolVersion: null,
+    daemonProtocolVersions
+  })
+
+  it('forces an update past mixed daemon generations only when the candidate attaches each', () => {
+    const plan = (daemonProtocolVersions: number[]) =>
+      planOrcadUpdate({
+        record: record(),
+        candidateVersion: '0.3.0+cc01',
+        candidateDaemonProtocol: PROTOCOL,
+        census: mixed(daemonProtocolVersions),
+        force: true
+      })
+    expect(plan([2, 3])).toMatchObject({ action: 'proceed', preservesLiveDaemon: true })
+    expect(plan([3, 4])).toMatchObject({
+      action: 'defer',
+      code: 'orcad_update_strands_live_terminals'
+    })
+    expect(plan([])).toMatchObject({
+      action: 'defer',
+      code: 'orcad_update_daemon_protocol_unverifiable'
+    })
+  })
+
+  it('rolls back over mixed daemon generations only when the target attaches each', () => {
+    const rollback = (daemonProtocolVersions: number[]) =>
+      assessOrcadRollback({
+        record: record(),
+        snapshotPresent: true,
+        census: mixed(daemonProtocolVersions),
+        targetDaemonProtocol: PROTOCOL,
+        stateWritesSinceActivation: false
+      })
+    expect(rollback([1, 3])).toMatchObject({ safety: 'clean' })
+    expect(rollback([2, 4])).toMatchObject({
+      safety: 'unsafe',
+      code: 'orcad_rollback_strands_live_terminals'
+    })
+  })
+
   it('needs no protocol answer when no terminals are running', () => {
     const plan = planOrcadUpdate({
       record: record(),
diff --git a/src/main/ssh/orcad-update-plan.ts b/src/main/ssh/orcad-update-plan.ts
index 83e03a92e08..4a6bd61fa4a 100644
--- a/src/main/ssh/orcad-update-plan.ts
+++ b/src/main/ssh/orcad-update-plan.ts
@@ -3,6 +3,7 @@ import type { OrcadActivationRecord } from '../managed-server/activation/orcad-a
 import type { OrcadTerminalCensus } from '../../shared/orcad-terminal-census'
 import {
   assessOrcadLiveDaemonCrossing,
+  describeDaemonProtocols,
   type OrcadDaemonProtocolFacts
 } from './orcad-daemon-protocol-crossing'
 
@@ -55,18 +56,18 @@ export function planOrcadUpdate(input: {
   }
   const crossing = assessOrcadLiveDaemonCrossing(input.census, input.candidateDaemonProtocol)
   // Force can accept mixed builds, never unreachable terminals.
-  if (crossing === 'strands-live-terminals') {
+  if (crossing.state === 'strands-live-terminals') {
     return {
       action: 'defer',
       code: 'orcad_update_strands_live_terminals',
       reason:
-        `The live terminal daemon speaks protocol ${String(input.census.daemonProtocolVersion)}, ` +
+        `A live terminal daemon speaks ${describeDaemonProtocols(crossing.unattachable)}, ` +
         `which orcad ${input.candidateVersion} cannot attach to. Restarting now would leave ` +
-        'every running terminal unreachable. Update when no terminals are running.'
+        'its running terminals unreachable. Update when no terminals are running.'
     }
   }
   const { liveSessions } = input.census
-  if (input.force && crossing === 'unverifiable') {
+  if (input.force && crossing.state === 'unverifiable') {
     return {
       action: 'defer',
       code: 'orcad_update_daemon_protocol_unverifiable',
@@ -209,7 +210,7 @@ export function assessOrcadRollback(input: {
     }
   }
   const crossing = assessOrcadLiveDaemonCrossing(input.census, input.targetDaemonProtocol)
-  if (crossing === 'unverifiable') {
+  if (crossing.state === 'unverifiable') {
     return {
       safety: 'unsafe',
       code: 'orcad_rollback_daemon_protocol_unverifiable',
@@ -218,13 +219,13 @@ export function assessOrcadRollback(input: {
         `${target} would reach the terminals still running. Retry when the daemon answers.`
     }
   }
-  if (crossing === 'strands-live-terminals') {
+  if (crossing.state === 'strands-live-terminals') {
     return {
       safety: 'unsafe',
       code: 'orcad_rollback_strands_live_terminals',
       reason:
-        `The live terminal daemon speaks protocol ${String(input.census.daemonProtocolVersion)}, ` +
-        `which ${target} does not list. Rolling back now would leave every running terminal ` +
+        `A live terminal daemon speaks ${describeDaemonProtocols(crossing.unattachable)}, ` +
+        `which ${target} does not list. Rolling back now would leave its running terminals ` +
         'unreachable. Roll back when no terminals are running, or deploy forward.'
     }
   }
diff --git a/src/shared/orcad-terminal-census.ts b/src/shared/orcad-terminal-census.ts
index 73b0c6f4384..bc50929a75c 100644
--- a/src/shared/orcad-terminal-census.ts
+++ b/src/shared/orcad-terminal-census.ts
@@ -9,8 +9,10 @@ export const OrcadTerminalCensusSchema = z.object({
   liveSessions: CountSchema,
   /** Of those, how many started at or after the active version's activation. */
   startedSinceActivation: CountSchema,
-  /** Protocol of the daemon that owns those sessions. */
+  /** Protocol of the daemon that owns those sessions; null unless exactly one generation owns them. */
   daemonProtocolVersion: z.number().int().positive().nullable(),
+  /** Protocol of every daemon generation owning those sessions; absent on older hosts. */
+  daemonProtocolVersions: z.array(z.number().int().positive()).optional(),
   /** In-process fallback sessions end with orcad, unlike daemon sessions; absent on older hosts. */
   inProcessSessions: CountSchema.optional(),
   /** Admission-fence expiry, epoch ms; 0 means reopened. Absence never proves older servers fenced admission. */