diff --git a/.specs/features/pty-session-rename/spec.md b/.specs/features/pty-session-rename/spec.md
index 1333085..93f83c0 100644
--- a/.specs/features/pty-session-rename/spec.md
+++ b/.specs/features/pty-session-rename/spec.md
@@ -78,6 +78,16 @@ to own the terminal.
   guess is a rename that lands one prompt later.
 - Terminal focus reports (`ESC[I`, `ESC[O`, sent as whole chunks) SHALL NOT
   mark the box dirty.
+- An SGR mouse report (`ESC[<` followed by three digit fields separated by
+  semicolons and terminated by `M` or `m`) SHALL NOT mark the input box dirty.
+- An SGR mouse report SHALL NOT guard the next Enter.
+- WHEN an SGR mouse report shares a chunk with typed text, THEN the typed text
+  SHALL still mark the box dirty (the report alone is neutral, and the rest of
+  the chunk is processed as before).
+- WHEN an SGR mouse report is split across two chunks, THEN it SHALL still be
+  neutral.
+- IF a sequence starts with `ESC[<` but breaks the SGR mouse grammar, THEN it
+  SHALL be handled like any other unrecognised escape (dirty and guard).
 - The rename SHALL be typed at most once per session, and a held name SHALL be
   dropped when the session is disposed (no timer fires after dispose).
 
diff --git a/docs/harness-behaviour.md b/docs/harness-behaviour.md
index fc4703a..18b5c4c 100644
--- a/docs/harness-behaviour.md
+++ b/docs/harness-behaviour.md
@@ -241,6 +241,10 @@ DECRPM terminal replies arrived on stdin before the first prompt.
 submits a first prompt to a real session and then greps the transcript for the
 matching `custom-title`.
 
+Claude Code 2.1.281, launched from a trusted directory, enables the alternate
+screen (`ESC[?1049h`), any-event mouse tracking (`ESC[?1003h`), and SGR mouse
+encoding (`ESC[?1006h`), so mouse reports arrive on stdin during a session.
+
 ### `script(1)` hands over a pty with no size
 
 `script` only dimensions its pty when its own stdin is a terminal. CodeDeck
diff --git a/src/open/pty.ts b/src/open/pty.ts
index 2c691de..5cce8d3 100644
--- a/src/open/pty.ts
+++ b/src/open/pty.ts
@@ -35,6 +35,8 @@ const FALLBACK_COLUMNS = 80;
 const QUIET_MS = 300;
 const BRACKETED_PASTE_START = "\u001b[200~";
 const BRACKETED_PASTE_END = "\u001b[201~";
+const SGR_MOUSE_START = "\u001b[<";
+const SGR_MOUSE_REPORT = /^\u001b\[<[0-9]+;[0-9]+;[0-9]+[Mm]$/;
 // Matching terminal replies needs ESC and BEL in the pattern.
 const TERMINAL_REPLY = /^(?:(?:\u001bP[^\u001b]*\u001b\\)|(?:\u001b\][^\u001b\u0007]*(?:\u0007|\u001b\\))|(?:\u001b\[[?>][0-?]*[ -/]*(?:c|\$y|u|R|n)))+$/; // NOSONAR
 
@@ -61,6 +63,9 @@ export function createInputGate(options: InputGateOptions) {
   let disposed = false;
   let inPaste = false;
   let escapeCandidate = "";
+  let sgrMouseCandidate = false;
+  let dirtyBeforeEscape = false;
+  let previousByteBeforeEscape: number | undefined;
   let guardNextEnter = false;
   let previousByte: number | undefined;
   let lastActivity = now();
@@ -99,7 +104,35 @@ export function createInputGate(options: InputGateOptions) {
     guardNextEnter = false;
   };
 
-  const observeByte = (byte: number): void => {
+  const isSgrMousePrefix = (candidate: string): boolean => {
+    if (!candidate.startsWith(SGR_MOUSE_START)) return false;
+    const body = candidate.slice(SGR_MOUSE_START.length);
+    if (SGR_MOUSE_REPORT.test(candidate)) return true;
+    if (!/^[0-9;]*$/.test(body)) return false;
+    const fields = body.split(";");
+    return fields.length <= 3 && fields.slice(0, -1).every(Boolean);
+  };
+
+  const flushUnknownEscape = (byte: number): void => {
+    // Unrecognised escape sequences can edit earlier text, so guard the next Enter.
+    if (escapeCandidate !== "\u001b\r") guardNextEnter = true;
+    const candidate = Buffer.from(escapeCandidate);
+    const retryEscape = byte === 0x1b;
+    const flush = retryEscape ? candidate.subarray(0, -1) : candidate;
+    for (const candidateByte of flush) {
+      if (isSubmit(candidateByte, previousByte, inPaste)) observeEnter();
+      else markDirty();
+      previousByte = candidateByte;
+    }
+    escapeCandidate = retryEscape ? String.fromCharCode(byte) : "";
+    sgrMouseCandidate = false;
+    if (retryEscape) {
+      dirtyBeforeEscape = dirty;
+      previousByteBeforeEscape = previousByte;
+    }
+  };
+
+  const observeByte = (byte: number): boolean => {
     const char = String.fromCharCode(byte);
     if (escapeCandidate !== "") {
       escapeCandidate += char;
@@ -109,31 +142,44 @@ export function createInputGate(options: InputGateOptions) {
         inPaste = true;
         escapeCandidate = "";
         markDirty();
+        return true;
       } else if (escapeCandidate === BRACKETED_PASTE_END) {
         inPaste = false;
         escapeCandidate = "";
         markDirty();
-      } else if (!isStart && !isEnd) {
-        // Unrecognised escape sequences can edit earlier text, so guard the next Enter.
-        if (escapeCandidate !== "\u001b\r") guardNextEnter = true;
-        const candidate = Buffer.from(escapeCandidate);
-        const retryEscape = byte === 0x1b;
-        const flush = retryEscape ? candidate.subarray(0, -1) : candidate;
-        for (const candidateByte of flush) {
-          if (isSubmit(candidateByte, previousByte, inPaste)) observeEnter();
-          else markDirty();
-          previousByte = candidateByte;
+        return true;
+      } else if (escapeCandidate === SGR_MOUSE_START && !inPaste) {
+        sgrMouseCandidate = true;
+      } else if (sgrMouseCandidate) {
+        if (SGR_MOUSE_REPORT.test(escapeCandidate)) {
+          escapeCandidate = "";
+          sgrMouseCandidate = false;
+          dirty = dirtyBeforeEscape;
+          previousByte = previousByteBeforeEscape;
+          return false;
+        }
+        if (isSgrMousePrefix(escapeCandidate)) {
+          previousByte = byte;
+          return false;
         }
-        escapeCandidate = retryEscape ? char : "";
+        flushUnknownEscape(byte);
+        previousByte = byte;
+        return true;
+      } else if (!isStart && !isEnd) {
+        flushUnknownEscape(byte);
+        previousByte = byte;
+        return true;
       }
       previousByte = byte;
-      return;
+      return false;
     }
     if (byte === 0x1b) {
+      dirtyBeforeEscape = dirty;
+      previousByteBeforeEscape = previousByte;
       escapeCandidate = char;
       markDirty();
       previousByte = byte;
-      return;
+      return false;
     }
     if (isSubmit(byte, previousByte, inPaste)) {
       observeEnter();
@@ -145,6 +191,7 @@ export function createInputGate(options: InputGateOptions) {
       }
     }
     previousByte = byte;
+    return true;
   };
 
   return {
@@ -155,8 +202,10 @@ export function createInputGate(options: InputGateOptions) {
         chunk.equals(Buffer.from("\u001b[O")) ||
         TERMINAL_REPLY.test(chunk.toString("latin1"))
       ) return;
-      lastActivity = now();
-      for (const byte of chunk) observeByte(byte);
+      const observedAt = now();
+      let hasActivity = false;
+      for (const byte of chunk) hasActivity = observeByte(byte) || hasActivity;
+      if (hasActivity) lastActivity = observedAt;
       scheduleQuiet();
     },
     offer(keystrokes: string): void {
diff --git a/tests/open-pty.test.ts b/tests/open-pty.test.ts
index 7d8643f..018a86d 100644
--- a/tests/open-pty.test.ts
+++ b/tests/open-pty.test.ts
@@ -463,6 +463,86 @@ describe("pty input gate", () => {
     expect(inject).toHaveBeenCalledOnce();
   });
 
+  type InputGateStep =
+    | "offer"
+    | { observe: string }
+    | { advance: number }
+    | { assert: "held" | "injected" | "called" };
+  it.each([
+    [
+      "ignores a complete SGR mouse report without dirtying the input box",
+      [
+        "offer",
+        { advance: quietMs - 1 },
+        { observe: "\u001b[<35;40;12M" },
+        { advance: 1 },
+        { assert: "called" },
+      ],
+    ],
+    [
+      "does not guard the next Enter after an SGR mouse report",
+      [
+        { observe: "prompt" },
+        "offer",
+        { observe: "\r" },
+        { observe: "\u001b[<65;40;12m" },
+        { observe: "\r" },
+        { assert: "injected" },
+      ],
+    ],
+    [
+      "still marks typed text beside an SGR mouse report as dirty",
+      [
+        "offer",
+        { observe: "\u001b[<35;40;12Mtyped" },
+        { assert: "held" },
+      ],
+    ],
+    [
+      "ignores an SGR mouse report split across chunks",
+      [
+        { observe: "\u001b[<35;40;" },
+        { observe: "12M" },
+        "offer",
+        { assert: "injected" },
+      ],
+    ],
+    [
+      "guards Enter when an SGR mouse prefix breaks its grammar",
+      [
+        "offer",
+        { observe: "\u001b[<35x" },
+        { observe: "\r" },
+        { assert: "held" },
+        { observe: "\r" },
+        { assert: "injected" },
+      ],
+    ],
+    [
+      "still guards Enter after the Up arrow escape",
+      [
+        { observe: "prompt" },
+        "offer",
+        { observe: "\u001b[A" },
+        { observe: "\r" },
+        { assert: "held" },
+        { observe: "\r" },
+        { assert: "injected" },
+      ],
+    ],
+  ] satisfies Array<[string, InputGateStep[]]>)("%s", (_name, steps) => {
+    const { gate, inject } = setup();
+    for (const step of steps) {
+      if (step === "offer") gate.offer("/rename nome\r");
+      else if ("observe" in step) gate.observe(Buffer.from(step.observe));
+      else if ("advance" in step) vi.advanceTimersByTime(step.advance);
+      else if (step.assert === "held") expectHeldAfterQuiet(inject);
+      else if (step.assert === "injected") expectInjectedAfterQuiet(inject);
+      else if (step.assert === "called") expect(inject).toHaveBeenCalledOnce();
+      else throw new Error("Unhandled input gate step");
+    }
+  });
+
   it.each([
     {
       name: "separate chunks",