diff --git a/mobile/src/mobile-web/mobile-web-terminal-input.ts b/mobile/src/mobile-web/mobile-web-terminal-input.ts
index f619ab6fe31..f76c520a2e7 100644
--- a/mobile/src/mobile-web/mobile-web-terminal-input.ts
+++ b/mobile/src/mobile-web/mobile-web-terminal-input.ts
@@ -29,14 +29,18 @@ export function handleMobileWebTerminalInput(args: {
     requireLive(args.isLive)
     if (args.request.operation === 'input' || args.request.operation === 'queryReply') {
       const bytes = atob(args.request.data)
-      // Why: the page's own label is not evidence; the host drops opcode 18 that fails this same grammar check.
-      if (args.request.operation === 'queryReply' && !isTerminalQueryReply(bytes)) {
-        return null
+      if (args.request.operation === 'queryReply') {
+        // Why: the page's own label is not evidence; the host drops opcode 18 that fails this same grammar check.
+        // A host that never echoed the queryReply capability would take the reply as floor-taking
+        // shell input, so drop rather than downgrade to opcode 0 (TERMINAL_QUERY_REPLY_INPUT_RUNTIME_CAPABILITY).
+        if (!isTerminalQueryReply(bytes) || !args.record.supportsQueryReply) {
+          return null
+        }
       }
       sendMobileWebTerminalFrame(
         args.client,
         args.record,
-        args.request.operation === 'queryReply' && args.record.supportsQueryReply
+        args.request.operation === 'queryReply'
           ? TerminalStreamOpcode.QueryReply
           : TerminalStreamOpcode.Input,
         Uint8Array.from(bytes, (character) => character.charCodeAt(0))
diff --git a/mobile/src/mobile-web/mobile-web-terminal-lease-streams.ts b/mobile/src/mobile-web/mobile-web-terminal-lease-streams.ts
index 38e8e50cb2c..95ffc34ab36 100644
--- a/mobile/src/mobile-web/mobile-web-terminal-lease-streams.ts
+++ b/mobile/src/mobile-web/mobile-web-terminal-lease-streams.ts
@@ -149,11 +149,9 @@ export class MobileWebTerminalLeaseStreams {
         streamId: record.pageStreamId,
         viewport: record.viewport,
         startSequence: 0,
+        // Why: a lease stream negotiates no output multiplex, so it carries no reply opcode.
         maxOutstandingBytes: MOBILE_WEB_TERMINAL_MAX_OUTSTANDING_BYTES,
-        // Constants for the same reason as the multiplex path: the host publishes no floor state and
-        // no reply-authority verdict over the terminal stream, so neither can be derived here.
-        inputFloor: 'held',
-        queryReplyAuthority: true
+        queryReplyNegotiated: false
       })
       return
     }
diff --git a/mobile/src/mobile-web/mobile-web-terminal-multiplex-events.ts b/mobile/src/mobile-web/mobile-web-terminal-multiplex-events.ts
index fe676d7a833..bed0816cf5e 100644
--- a/mobile/src/mobile-web/mobile-web-terminal-multiplex-events.ts
+++ b/mobile/src/mobile-web/mobile-web-terminal-multiplex-events.ts
@@ -37,11 +37,7 @@ export function handleMobileWebTerminalMultiplexEvent(args: {
         viewport: record.viewport,
         startSequence: record.sentSequence,
         maxOutstandingBytes: MOBILE_WEB_TERMINAL_MAX_OUTSTANDING_BYTES,
-        // Constants: the host publishes neither over the terminal stream. `isMobileTerminalQueryReplyAuthority`
-        // elects one subscriber but is never sent, and opcode-17 WriteUnavailable reports a single
-        // refused write with no regain signal, so it is not the floor state this field declares.
-        inputFloor: 'held',
-        queryReplyAuthority: true
+        queryReplyNegotiated: record.supportsQueryReply
       })
     }
     return false
diff --git a/mobile/src/mobile-web/mobile-web-terminal-streams.test.ts b/mobile/src/mobile-web/mobile-web-terminal-streams.test.ts
index 43ede100bc7..563d7aa08ec 100644
--- a/mobile/src/mobile-web/mobile-web-terminal-streams.test.ts
+++ b/mobile/src/mobile-web/mobile-web-terminal-streams.test.ts
@@ -270,6 +270,41 @@ describe('MobileWebTerminalStreams', () => {
     expect(decodeTerminalStreamText(harness.sentFrames.at(-1)!.payload)).toBe('\x1b[0n')
   })
 
+  it('tells the page a host that never echoed queryReply negotiated no reply opcode', async () => {
+    const harness = createHarness()
+    await harness.streams.start({
+      requestId: 'request-old-host',
+      subscriptionId: SUBSCRIPTION_ID,
+      payload: subscribePayload(),
+      client: harness.client,
+      isRequestActive: () => true
+    })
+    harness.emitMultiplex({ type: 'ready' })
+    const subscribe = harness.sentFrames.at(-1)!
+    const hostStreamId = decodeTerminalStreamJson<Record<string, unknown>>(subscribe.payload)!
+      .streamId as number
+    harness.emitMultiplex({ type: 'subscribed', streamId: hostStreamId })
+    await settle()
+
+    expect(harness.events.at(-1)?.event).toMatchObject({
+      type: 'subscribed',
+      queryReplyNegotiated: false
+    })
+    const framesBefore = harness.sentFrames.length
+    await harness.streams.handle(
+      {
+        operation: 'queryReply',
+        streamId: SUBSCRIPTION_ID,
+        sequence: 0,
+        data: Buffer.from('\x1b[0n').toString('base64')
+      },
+      harness.client
+    )
+
+    // Why: opcode 0 would land the reply as floor-taking shell input on that host.
+    expect(harness.sentFrames).toHaveLength(framesBefore)
+  })
+
   it('drops a page query-reply that is not a reply grammar', async () => {
     const harness = createHarness()
     await harness.streams.start({
@@ -303,35 +338,6 @@ describe('MobileWebTerminalStreams', () => {
     expect(harness.sentFrames.length).toBe(framesBefore)
   })
 
-  it('falls back to legacy input when an older host omits query-reply support', async () => {
-    const harness = createHarness()
-    await harness.streams.start({
-      requestId: 'request-legacy-query',
-      subscriptionId: SUBSCRIPTION_ID,
-      payload: subscribePayload(),
-      client: harness.client,
-      isRequestActive: () => true
-    })
-    harness.emitMultiplex({ type: 'ready' })
-    const subscribe = harness.sentFrames.at(-1)!
-    const hostStreamId = decodeTerminalStreamJson<Record<string, unknown>>(subscribe.payload)!
-      .streamId as number
-    harness.emitMultiplex({ type: 'subscribed', streamId: hostStreamId })
-
-    await harness.streams.handle(
-      {
-        operation: 'queryReply',
-        streamId: SUBSCRIPTION_ID,
-        sequence: 0,
-        data: Buffer.from('\x1b[0n').toString('base64')
-      },
-      harness.client
-    )
-
-    expect(harness.sentFrames.at(-1)?.opcode).toBe(TerminalStreamOpcode.Input)
-    expect(decodeTerminalStreamText(harness.sentFrames.at(-1)!.payload)).toBe('\x1b[0n')
-  })
-
   it('keeps shell-owned device input native and returns status without native paths', async () => {
     const harness = createHarness()
     await harness.streams.start({
@@ -475,8 +481,7 @@ describe('MobileWebTerminalStreams', () => {
           viewport: { cols: 80, rows: 24 },
           startSequence: 0,
           maxOutstandingBytes: 256 * 1024,
-          inputFloor: 'held',
-          queryReplyAuthority: true
+          queryReplyNegotiated: false
         }
       }
     ])
diff --git a/mobile/src/session/host-session-terminal-operations.ts b/mobile/src/session/host-session-terminal-operations.ts
index 001da88f87a..0fce6b0a8e9 100644
--- a/mobile/src/session/host-session-terminal-operations.ts
+++ b/mobile/src/session/host-session-terminal-operations.ts
@@ -7,8 +7,6 @@ export type HostSessionTerminalStreamEvent =
       type: 'subscribed'
       cols?: number
       rows?: number
-      inputFloor?: 'held' | 'read-only'
-      queryReplyAuthority?: boolean
     }
   | {
       type: 'scrollback'
@@ -40,8 +38,6 @@ export type HostSessionTerminalStreamEvent =
   | {
       type: 'metadata'
       displayMode?: 'auto' | 'desktop' | 'phone'
-      inputFloor?: 'held' | 'read-only'
-      queryReplyAuthority?: boolean
       cwd?: string
     }
   | { type: 'end' | 'error' }
diff --git a/mobile/src/session/web-host-session-terminal-operations.test.ts b/mobile/src/session/web-host-session-terminal-operations.test.ts
index 607ddfca7b6..8026906d9db 100644
--- a/mobile/src/session/web-host-session-terminal-operations.test.ts
+++ b/mobile/src/session/web-host-session-terminal-operations.test.ts
@@ -232,7 +232,6 @@ function subscribed(): MobileWebTerminalEvent {
     viewport: { cols: 90, rows: 30 },
     startSequence: 0,
     maxOutstandingBytes: 256 * 1024,
-    inputFloor: 'held',
-    queryReplyAuthority: true
+    queryReplyNegotiated: true
   }
 }
diff --git a/mobile/src/session/web-host-session-terminal-operations.ts b/mobile/src/session/web-host-session-terminal-operations.ts
index aaf8090f2a1..adb44ffcece 100644
--- a/mobile/src/session/web-host-session-terminal-operations.ts
+++ b/mobile/src/session/web-host-session-terminal-operations.ts
@@ -109,22 +109,14 @@ function applyWebTerminalEffect(
   onEvent: (event: HostSessionTerminalStreamEvent) => void
 ): void {
   if (effect.type === 'ready') {
-    scheduler.markHostReady(effect.inputFloor, effect.queryReplyAuthority)
+    scheduler.markHostReady(effect.queryReplyNegotiated)
     onEvent({
       type: 'subscribed',
       cols: effect.viewport.cols,
-      rows: effect.viewport.rows,
-      inputFloor: effect.inputFloor,
-      queryReplyAuthority: effect.queryReplyAuthority
-    })
-  } else if (effect.type === 'authority') {
-    scheduler.setAuthority(effect.inputFloor, effect.queryReplyAuthority)
-    onEvent({
-      type: 'metadata',
-      displayMode: effect.displayMode,
-      inputFloor: effect.inputFloor,
-      queryReplyAuthority: effect.queryReplyAuthority
+      rows: effect.viewport.rows
     })
+  } else if (effect.type === 'displayMode') {
+    onEvent({ type: 'metadata', displayMode: effect.displayMode })
   } else if (effect.type === 'write') {
     onEvent({
       type: 'data',
diff --git a/src/mobile-web/src/mobile-web-bridge-post-dispose.test.ts b/src/mobile-web/src/mobile-web-bridge-post-dispose.test.ts
index 85589d23e92..49bc0b819be 100644
--- a/src/mobile-web/src/mobile-web-bridge-post-dispose.test.ts
+++ b/src/mobile-web/src/mobile-web-bridge-post-dispose.test.ts
@@ -81,7 +81,7 @@ describe('after dispose', () => {
       terminalDeviceInputRequest: vi.fn()
     } as unknown as MobileWebBridgeClientType
     const scheduler = new MobileWebTerminalRequestScheduler(client, 'T'.repeat(22), onError)
-    scheduler.markHostReady('held', true)
+    scheduler.markHostReady(true)
 
     const inFlight = scheduler.sendInputAsync('input', 'YQ==')
     await vi.waitFor(() => expect(terminalRequest).toHaveBeenCalledTimes(1))
diff --git a/src/mobile-web/src/mobile-web-terminal-bridge-client.test.ts b/src/mobile-web/src/mobile-web-terminal-bridge-client.test.ts
index 04f36863da1..c12b103f99c 100644
--- a/src/mobile-web/src/mobile-web-terminal-bridge-client.test.ts
+++ b/src/mobile-web/src/mobile-web-terminal-bridge-client.test.ts
@@ -61,8 +61,7 @@ it('subscribes by workspace/tab IDs and sends typed terminal ACKs', async () =>
       viewport: { cols: 80, rows: 24 },
       startSequence: 0,
       maxOutstandingBytes: 256 * 1024,
-      inputFloor: 'held',
-      queryReplyAuthority: true
+      queryReplyNegotiated: true
     }
   })
   expect(onEvent).toHaveBeenCalledOnce()
diff --git a/src/mobile-web/src/mobile-web-terminal-event-state.test.ts b/src/mobile-web/src/mobile-web-terminal-event-state.test.ts
index 064c3964235..3aebde95ae2 100644
--- a/src/mobile-web/src/mobile-web-terminal-event-state.test.ts
+++ b/src/mobile-web/src/mobile-web-terminal-event-state.test.ts
@@ -18,15 +18,13 @@ describe('MobileWebTerminalEventState', () => {
         viewport: { cols: 80, rows: 24 },
         startSequence: 10,
         maxOutstandingBytes: 256 * 1024,
-        inputFloor: 'held',
-        queryReplyAuthority: true
+        queryReplyNegotiated: true
       })
     ).toEqual({
       type: 'ready',
       sequence: 10,
       viewport: { cols: 80, rows: 24 },
-      inputFloor: 'held',
-      queryReplyAuthority: true
+      queryReplyNegotiated: true
     })
     state.apply({
       type: 'snapshotStart',
@@ -86,8 +84,7 @@ describe('MobileWebTerminalEventState', () => {
       viewport: { cols: 80, rows: 24 },
       startSequence: 4,
       maxOutstandingBytes: 256 * 1024,
-      inputFloor: 'held',
-      queryReplyAuthority: true
+      queryReplyNegotiated: true
     })
     expect(
       state.apply({
@@ -100,21 +97,29 @@ describe('MobileWebTerminalEventState', () => {
     ).toEqual({ type: 'resync', fromSequence: 4, reason: 'gap' })
   })
 
-  it('publishes input authority changes without exposing host metadata', () => {
+  it('publishes display mode changes without exposing host metadata', () => {
+    const state = new MobileWebTerminalEventState(STREAM_ID)
+    expect(state.apply({ type: 'metadata', streamId: STREAM_ID, displayMode: 'desktop' })).toEqual({
+      type: 'displayMode',
+      displayMode: 'desktop'
+    })
+  })
+
+  it('reads a shell that omits queryReplyNegotiated as no negotiated reply opcode', () => {
     const state = new MobileWebTerminalEventState(STREAM_ID)
     expect(
       state.apply({
-        type: 'metadata',
+        type: 'subscribed',
         streamId: STREAM_ID,
-        displayMode: 'desktop',
-        inputFloor: 'read-only',
-        queryReplyAuthority: false
+        viewport: { cols: 80, rows: 24 },
+        startSequence: 0,
+        maxOutstandingBytes: 256 * 1024
       })
     ).toEqual({
-      type: 'authority',
-      displayMode: 'desktop',
-      inputFloor: 'read-only',
-      queryReplyAuthority: false
+      type: 'ready',
+      sequence: 0,
+      viewport: { cols: 80, rows: 24 },
+      queryReplyNegotiated: false
     })
   })
 })
diff --git a/src/mobile-web/src/mobile-web-terminal-event-state.ts b/src/mobile-web/src/mobile-web-terminal-event-state.ts
index 46756600429..17e465a66fe 100644
--- a/src/mobile-web/src/mobile-web-terminal-event-state.ts
+++ b/src/mobile-web/src/mobile-web-terminal-event-state.ts
@@ -24,15 +24,9 @@ export type MobileWebTerminalEffect =
       type: 'ready'
       sequence: number
       viewport: { cols: number; rows: number }
-      inputFloor: 'held' | 'read-only'
-      queryReplyAuthority: boolean
-    }
-  | {
-      type: 'authority'
-      displayMode: 'auto' | 'desktop'
-      inputFloor: 'held' | 'read-only'
-      queryReplyAuthority: boolean
+      queryReplyNegotiated: boolean
     }
+  | { type: 'displayMode'; displayMode: 'auto' | 'desktop' }
   | { type: 'write'; data: Uint8Array; throughSequence: number }
   | {
       type: 'replace'
@@ -64,8 +58,7 @@ export class MobileWebTerminalEventState {
         type: 'ready',
         sequence: event.startSequence,
         viewport: event.viewport,
-        inputFloor: event.inputFloor,
-        queryReplyAuthority: event.queryReplyAuthority
+        queryReplyNegotiated: event.queryReplyNegotiated === true
       }
     }
     if (event.type === 'output') {
@@ -95,12 +88,7 @@ export class MobileWebTerminalEventState {
       return { type: 'closed' }
     }
     if (event.type === 'metadata') {
-      return {
-        type: 'authority',
-        displayMode: event.displayMode,
-        inputFloor: event.inputFloor,
-        queryReplyAuthority: event.queryReplyAuthority
-      }
+      return { type: 'displayMode', displayMode: event.displayMode }
     }
     if (event.type === 'resized') {
       return { type: 'resized', viewport: event.viewport }
diff --git a/src/mobile-web/src/mobile-web-terminal-request-scheduler-authority.test.ts b/src/mobile-web/src/mobile-web-terminal-request-scheduler-authority.test.ts
index 028d67e1f1a..c5525f5609a 100644
--- a/src/mobile-web/src/mobile-web-terminal-request-scheduler-authority.test.ts
+++ b/src/mobile-web/src/mobile-web-terminal-request-scheduler-authority.test.ts
@@ -9,7 +9,7 @@ describe('MobileWebTerminalRequestScheduler authority lifecycle', () => {
   it('drops host readiness and write authority when the terminal goes invisible', async () => {
     const harness = createHarness()
     harness.scheduler.markBridgeReady()
-    harness.scheduler.markHostReady('held', true)
+    harness.scheduler.markHostReady(true)
 
     await expect(harness.scheduler.sendInputAsync('input', 'YQ==')).resolves.toBe(true)
     expect(harness.operations('input')).toHaveLength(1)
@@ -33,14 +33,14 @@ describe('MobileWebTerminalRequestScheduler authority lifecycle', () => {
     const harness = createHarness((request) =>
       request.operation === 'input' && inFlight.pending() ? inFlight.promise : Promise.resolve(null)
     )
-    harness.scheduler.markHostReady('held', true)
+    harness.scheduler.markHostReady(true)
 
     const first = harness.scheduler.sendInputAsync('input', 'YQ==')
     const queued = harness.scheduler.sendInputAsync('input', 'Yg==')
     await vi.waitFor(() => expect(harness.operations('input')).toHaveLength(1))
 
     // Authority is revoked while the queued write is still parked behind the in-flight one.
-    harness.scheduler.setAuthority('read-only', false)
+    harness.scheduler.setVisible(false)
     inFlight.resolve(null)
 
     await expect(first).resolves.toBe(true)
@@ -48,14 +48,27 @@ describe('MobileWebTerminalRequestScheduler authority lifecycle', () => {
     expect(harness.operations('input')).toHaveLength(1)
   })
 
+  it('sends a query reply only when the shell reported a negotiated reply opcode', async () => {
+    const harness = createHarness()
+    harness.scheduler.markHostReady(false)
+
+    await expect(harness.scheduler.sendInputAsync('queryReply', 'YQ==')).resolves.toBe(false)
+    await expect(harness.scheduler.sendInputAsync('input', 'Yg==')).resolves.toBe(true)
+    harness.scheduler.markHostReady(true)
+    await expect(harness.scheduler.sendInputAsync('queryReply', 'Yw==')).resolves.toBe(true)
+
+    expect(harness.operations('queryReply')).toHaveLength(1)
+    expect(harness.operations('input')).toHaveLength(1)
+  })
+
   it('makes every entry point inert after dispose', async () => {
     const harness = createHarness()
     harness.scheduler.markBridgeReady()
-    harness.scheduler.markHostReady('held', true)
+    harness.scheduler.markHostReady(true)
     harness.scheduler.dispose()
 
     harness.scheduler.markBridgeReady()
-    harness.scheduler.markHostReady('held', true)
+    harness.scheduler.markHostReady(true)
     harness.scheduler.acknowledge(4)
     harness.scheduler.resize({ cols: 80, rows: 24 })
     harness.scheduler.setVisible(true)
diff --git a/src/mobile-web/src/mobile-web-terminal-request-scheduler.test.ts b/src/mobile-web/src/mobile-web-terminal-request-scheduler.test.ts
index fcb2e0d1621..597ae546463 100644
--- a/src/mobile-web/src/mobile-web-terminal-request-scheduler.test.ts
+++ b/src/mobile-web/src/mobile-web-terminal-request-scheduler.test.ts
@@ -11,7 +11,7 @@ describe('MobileWebTerminalRequestScheduler', () => {
     const first = deferred<null>()
     const terminalRequest = vi.fn().mockReturnValueOnce(first.promise).mockResolvedValue(null)
     const scheduler = createScheduler(terminalRequest)
-    scheduler.markHostReady('held', true)
+    scheduler.markHostReady(true)
 
     scheduler.sendInput('input', 'YQ==')
     scheduler.sendInput('input', 'Yg==')
@@ -26,7 +26,7 @@ describe('MobileWebTerminalRequestScheduler', () => {
     const terminalRequest = vi.fn().mockRejectedValueOnce(new Error('busy')).mockResolvedValue(null)
     const onError = vi.fn()
     const scheduler = createScheduler(terminalRequest, onError)
-    scheduler.markHostReady('held', true)
+    scheduler.markHostReady(true)
 
     scheduler.sendInput('input', 'YQ==')
     scheduler.sendInput('input', 'Yg==')
@@ -34,7 +34,7 @@ describe('MobileWebTerminalRequestScheduler', () => {
     expect(terminalRequest.mock.calls.map(([request]) => request.sequence)).toEqual([0, 0])
     expect(onError).toHaveBeenCalledOnce()
 
-    scheduler.setAuthority('read-only', false)
+    scheduler.setVisible(false)
     scheduler.sendInput('input', 'Yw==')
     scheduler.sendInput('queryReply', 'ZA==')
     await Promise.resolve()
@@ -54,7 +54,7 @@ describe('MobileWebTerminalRequestScheduler', () => {
       return Promise.resolve(null)
     })
     const scheduler = createScheduler(terminalRequest)
-    scheduler.markHostReady('held', true)
+    scheduler.markHostReady(true)
 
     scheduler.acknowledge(5)
     scheduler.acknowledge(8)
@@ -91,7 +91,7 @@ describe('MobileWebTerminalRequestScheduler', () => {
 
     scheduler.requestResync(4, 'gap')
     expect(terminalRequest).toHaveBeenCalledTimes(1)
-    scheduler.markHostReady('held', true)
+    scheduler.markHostReady(true)
     scheduler.requestResync(4, 'gap')
     scheduler.requestResync(4, 'gap')
     await vi.waitFor(() => expect(terminalRequest).toHaveBeenCalledTimes(2))
@@ -129,7 +129,7 @@ describe('MobileWebTerminalRequestScheduler', () => {
       .mockResolvedValueOnce({ status: 'accepted' })
       .mockResolvedValueOnce({ status: 'cancelled' })
     const scheduler = createScheduler(terminalRequest, vi.fn(), terminalDeviceInputRequest)
-    scheduler.markHostReady('held', true)
+    scheduler.markHostReady(true)
 
     const input = scheduler.sendInputAsync('input', 'YQ==')
     const paste = scheduler.pasteClipboard(true)
diff --git a/src/mobile-web/src/mobile-web-terminal-request-scheduler.ts b/src/mobile-web/src/mobile-web-terminal-request-scheduler.ts
index 5276f994077..a5d16107f22 100644
--- a/src/mobile-web/src/mobile-web-terminal-request-scheduler.ts
+++ b/src/mobile-web/src/mobile-web-terminal-request-scheduler.ts
@@ -19,8 +19,7 @@ export class MobileWebTerminalRequestScheduler {
   private bridgeReady = false
   private hostReady = false
   private disposed = false
-  private inputFloor: 'held' | 'read-only' = 'read-only'
-  private queryReplyAuthority = false
+  private queryReplyNegotiated = false
   private inputSequence = 0
   private inputTail = Promise.resolve()
   private pendingAck: number | null = null
@@ -45,22 +44,17 @@ export class MobileWebTerminalRequestScheduler {
     this.drainVisibility()
   }
 
-  markHostReady(inputFloor: 'held' | 'read-only', queryReplyAuthority: boolean): void {
+  markHostReady(queryReplyNegotiated: boolean): void {
     if (this.disposed) {
       return
     }
     this.hostReady = true
     this.resyncPending = false
-    this.setAuthority(inputFloor, queryReplyAuthority)
+    this.queryReplyNegotiated = queryReplyNegotiated
     this.drainResize()
     this.drainAck()
   }
 
-  setAuthority(inputFloor: 'held' | 'read-only', queryReplyAuthority: boolean): void {
-    this.inputFloor = inputFloor
-    this.queryReplyAuthority = queryReplyAuthority
-  }
-
   sendInput(operation: InputOperation, data: string): void {
     void this.sendInputAsync(operation, data)
   }
@@ -131,8 +125,7 @@ export class MobileWebTerminalRequestScheduler {
     }
     if (!visible) {
       this.hostReady = false
-      this.inputFloor = 'read-only'
-      this.queryReplyAuthority = false
+      this.queryReplyNegotiated = false
       this.pendingAck = null
       this.resyncPending = false
     }
@@ -185,10 +178,7 @@ export class MobileWebTerminalRequestScheduler {
   }
 
   private canSendInput(operation: InputOperation): boolean {
-    return (
-      this.hostReady &&
-      (operation === 'queryReply' ? this.queryReplyAuthority : this.inputFloor === 'held')
-    )
+    return this.hostReady && (operation !== 'queryReply' || this.queryReplyNegotiated)
   }
 
   private drainAck(): void {
diff --git a/src/shared/mobile-web/terminal-stream-contract.test.ts b/src/shared/mobile-web/terminal-stream-contract.test.ts
index a727cdcf942..67ccdc94ea5 100644
--- a/src/shared/mobile-web/terminal-stream-contract.test.ts
+++ b/src/shared/mobile-web/terminal-stream-contract.test.ts
@@ -229,9 +229,7 @@ describe('mobile web terminal snapshot and lifecycle contract', () => {
       {
         type: 'metadata',
         streamId: STREAM_ID,
-        displayMode: 'auto',
-        inputFloor: 'held',
-        queryReplyAuthority: true
+        displayMode: 'auto'
       },
       { type: 'closed', streamId: STREAM_ID, reason: 'terminal-exited' },
       { type: 'error', streamId: STREAM_ID, code: 'host_error', recoverable: true }
diff --git a/src/shared/mobile-web/terminal-stream-contract.ts b/src/shared/mobile-web/terminal-stream-contract.ts
index 3179249f7d0..fdec738666c 100644
--- a/src/shared/mobile-web/terminal-stream-contract.ts
+++ b/src/shared/mobile-web/terminal-stream-contract.ts
@@ -142,8 +142,10 @@ const SubscribedEventSchema = z
     viewport: ViewportSchema,
     startSequence: SequenceSchema,
     maxOutstandingBytes: z.literal(MOBILE_WEB_TERMINAL_MAX_OUTSTANDING_BYTES),
-    inputFloor: z.enum(['held', 'read-only']),
-    queryReplyAuthority: z.boolean()
+    // Whether the host negotiated opcode 18 on this stream, not an election verdict: the host
+    // re-checks reply authority per frame and never publishes it. Absent means a shell that
+    // predates the field, which cannot prove negotiation, so the page must not attempt a reply.
+    queryReplyNegotiated: z.boolean().optional()
   })
   .strict()
 
@@ -215,9 +217,7 @@ const MetadataEventSchema = z
   .object({
     type: z.literal('metadata'),
     streamId: StreamIdSchema,
-    displayMode: z.enum(['auto', 'desktop']),
-    inputFloor: z.enum(['held', 'read-only']),
-    queryReplyAuthority: z.boolean()
+    displayMode: z.enum(['auto', 'desktop'])
   })
   .strict()
 const ClosedEventSchema = z