diff --git a/Sources/RestorableAgentSession.swift b/Sources/RestorableAgentSession.swift
index 68e6bf8f27ce..5b901d9ce1e6 100644
--- a/Sources/RestorableAgentSession.swift
+++ b/Sources/RestorableAgentSession.swift
@@ -1,8 +1,35 @@
 import Foundation
 import CMUXAgentLaunch
 
+nonisolated enum TerminalStartupShellQuoting {
+    static func singleQuoted(_ value: String) -> String {
+        if value.utf8.contains(where: { $0 >= 0x80 }) {
+            return asciiPrintfCommandSubstitution(for: value)
+        }
+        return "'" + value.replacingOccurrences(of: "'", with: "'\\''") + "'"
+    }
+
+    static func shellToken(_ value: String, allowingBareASCII: Bool) -> String {
+        if value.utf8.contains(where: { $0 >= 0x80 }) {
+            return asciiPrintfCommandSubstitution(for: value)
+        }
+        if allowingBareASCII,
+           value.range(of: "[^A-Za-z0-9_./:=+-]", options: .regularExpression) == nil {
+            return value
+        }
+        return singleQuoted(value)
+    }
+
+    private static func asciiPrintfCommandSubstitution(for value: String) -> String {
+        let octalBytes = value.utf8
+            .map { String(format: #"\%03o"#, Int($0)) }
+            .joined()
+        return #""$(printf '"# + octalBytes + #"')""#
+    }
+}
+
 fileprivate func shellSingleQuoted(_ value: String) -> String {
-    "'" + value.replacingOccurrences(of: "'", with: "'\\''") + "'"
+    TerminalStartupShellQuoting.singleQuoted(value)
 }
 
 enum AgentResumeCommandBuilder {
diff --git a/Sources/SessionIndexModels.swift b/Sources/SessionIndexModels.swift
index baaddd5a897d..7ea3d9920751 100644
--- a/Sources/SessionIndexModels.swift
+++ b/Sources/SessionIndexModels.swift
@@ -432,16 +432,12 @@ struct SessionEntry: Identifiable, Hashable {
     }
 
     private static func shellSingleQuote(_ value: String) -> String {
-        "'\(value.replacingOccurrences(of: "'", with: #"'\''"#))'"
+        TerminalStartupShellQuoting.singleQuoted(value)
     }
 
     /// Single-quote a value for safe shell injection. Escapes embedded single quotes.
     static func shellQuote(_ value: String) -> String {
-        if value.range(of: "[^A-Za-z0-9_./:=+-]", options: .regularExpression) == nil {
-            return value
-        }
-        let escaped = value.replacingOccurrences(of: "'", with: #"'\''"#)
-        return "'\(escaped)'"
+        TerminalStartupShellQuoting.shellToken(value, allowingBareASCII: true)
     }
 
     var displayTitle: String {
diff --git a/cmuxTests/SessionPersistenceTests.swift b/cmuxTests/SessionPersistenceTests.swift
index 3e5750ad76ca..05e95522b590 100644
--- a/cmuxTests/SessionPersistenceTests.swift
+++ b/cmuxTests/SessionPersistenceTests.swift
@@ -1948,6 +1948,45 @@ final class SocketListenerAcceptPolicyTests: XCTestCase {
         )
     }
 
+    func testRestorableAgentResumeStartupInputEscapesNonAsciiWorkingDirectoryAsAsciiShellInput() throws {
+        let root = FileManager.default.temporaryDirectory
+            .appendingPathComponent("cmux-agent-resume-\(UUID().uuidString)", isDirectory: true)
+        let cwdURL = root
+            .appendingPathComponent("中文路径", isDirectory: true)
+            .appendingPathComponent("uam-service", isDirectory: true)
+        try FileManager.default.createDirectory(at: cwdURL, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: root) }
+
+        let snapshot = SessionRestorableAgentSnapshot(
+            kind: .claude,
+            sessionId: "claude-session-123",
+            workingDirectory: cwdURL.path,
+            launchCommand: AgentLaunchCommandSnapshot(
+                launcher: "claude",
+                executablePath: "/opt/Claude Code/bin/claude",
+                arguments: [
+                    "/opt/Claude Code/bin/claude",
+                    "--model",
+                    "sonnet"
+                ],
+                workingDirectory: cwdURL.path,
+                environment: ["CLAUDE_CONFIG_DIR": cwdURL.path],
+                capturedAt: 123,
+                source: "environment"
+            )
+        )
+
+        let startupInput = try XCTUnwrap(snapshot.resumeStartupInput())
+        XCTAssertTrue(
+            startupInput.utf8.allSatisfy { $0 < 0x80 },
+            "Terminal startup input must stay ASCII-only so UTF-8 paths are reconstructed by the shell instead of being mojibaked before execution."
+        )
+
+        let command = startupInput.trimmingCharacters(in: .newlines)
+        let cdCommand = try leadingCdCommand(from: command)
+        try assertZshCommandChangesDirectory(cdCommand, expectedPath: cwdURL.path)
+    }
+
     func testSessionEntryClaudeResumeCommandChangesToSessionCwdBeforeResume() throws {
         let root = FileManager.default.temporaryDirectory
             .appendingPathComponent("cmux-claude-resume-\(UUID().uuidString)", isDirectory: true)
@@ -1986,6 +2025,76 @@ final class SocketListenerAcceptPolicyTests: XCTestCase {
         )
     }
 
+    func testSessionEntryClaudeResumeCommandEscapesNonAsciiCwdAsAsciiShellInput() throws {
+        let root = FileManager.default.temporaryDirectory
+            .appendingPathComponent("cmux-claude-resume-\(UUID().uuidString)", isDirectory: true)
+        let cwdURL = root
+            .appendingPathComponent("中文路径", isDirectory: true)
+            .appendingPathComponent("uam-service", isDirectory: true)
+        try FileManager.default.createDirectory(at: cwdURL, withIntermediateDirectories: true)
+        defer { try? FileManager.default.removeItem(at: root) }
+
+        let entry = SessionEntry(
+            id: "claude:4d8cfb79-ef17-41a7-a0ac-2f0c25ac1519",
+            agent: .claude,
+            sessionId: "4d8cfb79-ef17-41a7-a0ac-2f0c25ac1519",
+            title: "resume me",
+            cwd: cwdURL.path,
+            gitBranch: nil,
+            pullRequest: nil,
+            modified: Date(timeIntervalSince1970: 0),
+            fileURL: nil,
+            specifics: .claude(
+                model: "gpt-5.5",
+                permissionMode: "bypassPermissions",
+                configDirectoryForResume: nil
+            )
+        )
+
+        let command = try XCTUnwrap(entry.resumeCommand)
+        XCTAssertTrue(
+            command.utf8.allSatisfy { $0 < 0x80 },
+            "Terminal startup input must stay ASCII-only so UTF-8 paths are reconstructed by the shell instead of being mojibaked before execution."
+        )
+
+        let cdCommand = try leadingCdCommand(from: command)
+        try assertZshCommandChangesDirectory(cdCommand, expectedPath: cwdURL.path)
+    }
+
+    private func leadingCdCommand(from command: String) throws -> String {
+        let separator = try XCTUnwrap(command.range(of: " && "))
+        return String(command[..<separator.lowerBound])
+    }
+
+    private func assertZshCommandChangesDirectory(
+        _ cdCommand: String,
+        expectedPath: String,
+        file: StaticString = #filePath,
+        line: UInt = #line
+    ) throws {
+        let process = Process()
+        process.executableURL = URL(fileURLWithPath: "/bin/zsh")
+        process.arguments = ["-fc", "\(cdCommand) && pwd"]
+
+        let output = Pipe()
+        let error = Pipe()
+        process.standardOutput = output
+        process.standardError = error
+
+        try process.run()
+        process.waitUntilExit()
+
+        let outputData = output.fileHandleForReading.readDataToEndOfFile()
+        let errorData = error.fileHandleForReading.readDataToEndOfFile()
+        let stdout = String(data: outputData, encoding: .utf8)?
+            .trimmingCharacters(in: .newlines)
+        let stderr = String(data: errorData, encoding: .utf8)?
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+
+        XCTAssertEqual(process.terminationStatus, 0, stderr ?? "", file: file, line: line)
+        XCTAssertEqual(stdout, expectedPath, file: file, line: line)
+    }
+
     func testRestorableAgentStartupInputUsesInlineCommandWhenShort() {
         let snapshot = SessionRestorableAgentSnapshot(
             kind: .claude,