diff --git a/src/main/daemon/headless-emulator.test.ts b/src/main/daemon/headless-emulator.test.ts
index d59a8d798..fd4a4a15c 100644
--- a/src/main/daemon/headless-emulator.test.ts
+++ b/src/main/daemon/headless-emulator.test.ts
@@ -138,22 +138,6 @@ describe('HeadlessEmulator', () => {
     })
   })
 
-  describe('onData callback', () => {
-    it('fires onData for terminal query responses', async () => {
-      const responses: string[] = []
-      emulator = new HeadlessEmulator({
-        cols: 80,
-        rows: 24,
-        onData: (data) => responses.push(data)
-      })
-
-      // DA1 query — xterm.js will respond with a device attributes string
-      await emulator.write('\x1b[c')
-
-      expect(responses.length).toBeGreaterThan(0)
-    })
-  })
-
   describe('terminal modes', () => {
     it('tracks bracketed paste mode', async () => {
       emulator = new HeadlessEmulator({ cols: 80, rows: 24 })
diff --git a/src/main/daemon/headless-emulator.ts b/src/main/daemon/headless-emulator.ts
index 101cb471d..6491e435d 100644
--- a/src/main/daemon/headless-emulator.ts
+++ b/src/main/daemon/headless-emulator.ts
@@ -7,7 +7,6 @@ export type HeadlessEmulatorOptions = {
   cols: number
   rows: number
   scrollback?: number
-  onData?: (data: string) => void
 }
 
 const DEFAULT_SCROLLBACK = 5000
@@ -57,9 +56,17 @@ export class HeadlessEmulator {
     this.serializer = new SerializeAddon()
     this.terminal.loadAddon(this.serializer)
 
-    if (opts.onData) {
-      this.terminal.onData(opts.onData)
-    }
+    // Why no onData wiring: this emulator exists purely for state tracking
+    // (snapshots, cwd, mode flags). It MUST NOT respond to terminal query
+    // sequences (DA1/DA2, DSR, OSC 10/11/12, DECRPM). The emulator parses
+    // data in-process synchronously before `handleSubprocessData` forwards
+    // it to the renderer over IPC, so any reply it emits would land on the
+    // shell's stdin ahead of the renderer's xterm reply and win the race.
+    // The renderer is the authoritative responder (it has the real theme,
+    // cursor position, and paste mode); a daemon-side reply would be a
+    // double-reply with wrong values. OSC 11 was the visible casualty:
+    // Claude Code's /theme auto always saw the emulator's default-black
+    // background regardless of Orca's configured terminal theme.
   }
 
   write(data: string): Promise<void> {
diff --git a/src/main/daemon/session.test.ts b/src/main/daemon/session.test.ts
index 119c2cf13..c15d1107e 100644
--- a/src/main/daemon/session.test.ts
+++ b/src/main/daemon/session.test.ts
@@ -156,6 +156,27 @@ describe('Session', () => {
     })
   })
 
+  describe('emulator does not reply to terminal queries', () => {
+    // Why: daemon emulator parses in-process synchronously — before
+    // handleSubprocessData forwards bytes to the renderer over IPC — so any
+    // auto-reply it emits races ahead of the renderer's xterm and clobbers
+    // it with default-xterm values (no theme, stale cursor). The renderer is
+    // the authoritative responder; a daemon-side reply to any query is a bug.
+    it.each([
+      ['OSC 11 background-color', '\x1b]11;?\x07'],
+      ['DA1 device-attributes', '\x1b[c'],
+      ['DSR cursor-position', '\x1b[6n']
+    ])('does not reply to %s query', async (_label, query) => {
+      createSession({ shellReadySupported: false })
+      subprocess.simulateData(query)
+      // xterm.js fires terminal.write's completion callback via a microtask;
+      // two resolved-promise awaits flush any nested scheduling.
+      await Promise.resolve()
+      await Promise.resolve()
+      expect(subprocess.written).toEqual([])
+    })
+  })
+
   describe('shell readiness gating', () => {
     it('buffers writes during pending state', () => {
       createSession({ shellReadySupported: true })
diff --git a/src/main/daemon/session.ts b/src/main/daemon/session.ts
index 12c9ca067..e01627ff3 100644
--- a/src/main/daemon/session.ts
+++ b/src/main/daemon/session.ts
@@ -54,16 +54,11 @@ export class Session {
     this.emulator = new HeadlessEmulator({
       cols: size.cols,
       rows: size.rows,
-      scrollback: opts.scrollback,
-      // Why: xterm.js generates query responses (DA1, DSR) asynchronously.
-      // If the subprocess has already exited, writing to it would hit a dead
-      // NAPI handle. Check session state before forwarding.
-      onData: (data) => {
-        if (this._state === 'exited' || this._disposed) {
-          return
-        }
-        opts.subprocess.write(data)
-      }
+      scrollback: opts.scrollback
+      // No onData wiring: the daemon-side emulator must never reply to
+      // terminal query sequences. The renderer's xterm is the authoritative
+      // responder; any daemon reply races ahead via in-process parsing and
+      // clobbers the renderer's answer. See the comment in HeadlessEmulator.
     })
 
     if (opts.shellReadySupported) {