diff --git a/crates/arc-agent/src/docker_sandbox.rs b/crates/arc-agent/src/docker_sandbox.rs
index ff9d54657..c636e8404 100644
--- a/crates/arc-agent/src/docker_sandbox.rs
+++ b/crates/arc-agent/src/docker_sandbox.rs
@@ -956,4 +956,4 @@ mod tests {
 
         std::fs::remove_dir_all(&host_dir).ok();
     }
-}
\ No newline at end of file
+}
diff --git a/crates/arc-exe/src/lib.rs b/crates/arc-exe/src/lib.rs
index 91fc12372..07af21d1b 100644
--- a/crates/arc-exe/src/lib.rs
+++ b/crates/arc-exe/src/lib.rs
@@ -164,7 +164,9 @@ impl ExeSandbox {
             rg_available: tokio::sync::OnceCell::const_new(),
             event_callback: None,
             data_ssh_factory: Box::new(|_: &str| {
-                Box::pin(async { Err("from_existing sandbox cannot create new SSH connections".to_string()) })
+                Box::pin(async {
+                    Err("from_existing sandbox cannot create new SSH connections".to_string())
+                })
             }),
             config: ExeConfig::default(),
             clone_params: None,
diff --git a/crates/arc-workflows/src/cli/cp.rs b/crates/arc-workflows/src/cli/cp.rs
index 9ed0a25d3..e75cd67a7 100644
--- a/crates/arc-workflows/src/cli/cp.rs
+++ b/crates/arc-workflows/src/cli/cp.rs
@@ -53,7 +53,9 @@ fn parse_direction(src: &str, dst: &str) -> Result<CopyDirection> {
             run_prefix: run_prefix.to_string(),
             remote_path: remote_path.to_string(),
         }),
-        (Some(_), Some(_)) => bail!("Cannot copy between two sandboxes; one argument must be a local path"),
+        (Some(_), Some(_)) => {
+            bail!("Cannot copy between two sandboxes; one argument must be a local path")
+        }
         (None, None) => bail!("One argument must contain a run-id prefix (e.g. <run-id>:<path>)"),
     }
 }
@@ -104,9 +106,7 @@ fn find_run_by_prefix(base: &Path, prefix: &str) -> Result<PathBuf> {
 /// Returns a sandbox that can perform file operations.
 /// Note: for Docker and Local sandboxes, the container/directory may still
 /// need to be alive. For Daytona and Exe, we reconnect via their APIs.
-async fn reconnect(
-    record: &SandboxRecord,
-) -> Result<Box<dyn arc_agent::sandbox::Sandbox>> {
+pub async fn reconnect(record: &SandboxRecord) -> Result<Box<dyn arc_agent::sandbox::Sandbox>> {
     debug!(
         provider = %record.provider,
         identifier = record.identifier.as_deref().unwrap_or(""),
@@ -115,8 +115,9 @@ async fn reconnect(
 
     match record.provider.as_str() {
         "local" => {
-            let sandbox =
-                arc_agent::local_sandbox::LocalSandbox::new(PathBuf::from(&record.working_directory));
+            let sandbox = arc_agent::local_sandbox::LocalSandbox::new(PathBuf::from(
+                &record.working_directory,
+            ));
             Ok(Box::new(sandbox))
         }
         "docker" => {
@@ -153,15 +154,12 @@ async fn reconnect(
                 .await
                 .map_err(|e| anyhow::anyhow!("Failed to create Daytona client: {e}"))?;
 
-            let sdk_sandbox = client
-                .get(name)
-                .await
-                .map_err(|e| anyhow::anyhow!("Failed to reconnect to Daytona sandbox '{name}': {e}"))?;
+            let sdk_sandbox = client.get(name).await.map_err(|e| {
+                anyhow::anyhow!("Failed to reconnect to Daytona sandbox '{name}': {e}")
+            })?;
 
-            let sandbox = crate::daytona_sandbox::DaytonaSandbox::from_existing(
-                client,
-                sdk_sandbox,
-            );
+            let sandbox =
+                crate::daytona_sandbox::DaytonaSandbox::from_existing(client, sdk_sandbox);
             Ok(Box::new(sandbox))
         }
         "exe" => {
@@ -172,7 +170,9 @@ async fn reconnect(
 
             let data_ssh = arc_exe::OpensshRunner::connect(data_host)
                 .await
-                .map_err(|e| anyhow::anyhow!("Failed to connect to exe sandbox '{data_host}': {e}"))?;
+                .map_err(|e| {
+                    anyhow::anyhow!("Failed to connect to exe sandbox '{data_host}': {e}")
+                })?;
 
             let sandbox = arc_exe::ExeSandbox::from_existing(Box::new(data_ssh));
             Ok(Box::new(sandbox))
@@ -194,8 +194,9 @@ pub async fn cp_command(args: CpArgs) -> Result<()> {
             let run_dir = find_run_by_prefix(&base, &run_prefix)?;
             let sandbox_json = run_dir.join("sandbox.json");
             debug!(path = %sandbox_json.display(), "Loading sandbox record");
-            let record = SandboxRecord::load(&sandbox_json)
-                .context("Failed to load sandbox.json — was this run started with a recent version of arc?")?;
+            let record = SandboxRecord::load(&sandbox_json).context(
+                "Failed to load sandbox.json — was this run started with a recent version of arc?",
+            )?;
 
             info!(run_id = %run_prefix, provider = %record.provider, "Connecting to sandbox");
             let sandbox = reconnect(&record).await?;
@@ -219,8 +220,9 @@ pub async fn cp_command(args: CpArgs) -> Result<()> {
             let run_dir = find_run_by_prefix(&base, &run_prefix)?;
             let sandbox_json = run_dir.join("sandbox.json");
             debug!(path = %sandbox_json.display(), "Loading sandbox record");
-            let record = SandboxRecord::load(&sandbox_json)
-                .context("Failed to load sandbox.json — was this run started with a recent version of arc?")?;
+            let record = SandboxRecord::load(&sandbox_json).context(
+                "Failed to load sandbox.json — was this run started with a recent version of arc?",
+            )?;
 
             info!(run_id = %run_prefix, provider = %record.provider, "Connecting to sandbox");
             let sandbox = reconnect(&record).await?;
@@ -278,7 +280,8 @@ async fn upload_recursive(
     remote_path: &str,
 ) -> Result<()> {
     let mut file_count = 0usize;
-    let mut stack: Vec<(PathBuf, String)> = vec![(local_path.to_path_buf(), remote_path.to_string())];
+    let mut stack: Vec<(PathBuf, String)> =
+        vec![(local_path.to_path_buf(), remote_path.to_string())];
 
     while let Some((dir_path, dir_remote)) = stack.pop() {
         let mut entries = tokio::fs::read_dir(&dir_path)
@@ -448,4 +451,4 @@ mod tests {
             "Should mention ambiguity"
         );
     }
-}
\ No newline at end of file
+}
diff --git a/crates/arc-workflows/src/cli/run.rs b/crates/arc-workflows/src/cli/run.rs
index 488f104a7..89fa68628 100644
--- a/crates/arc-workflows/src/cli/run.rs
+++ b/crates/arc-workflows/src/cli/run.rs
@@ -519,7 +519,7 @@ pub async fn run_command(
     };
 
     // Set up git worktree for local execution (must happen before cwd is captured)
-    let (worktree_work_dir, worktree_path, worktree_branch, worktree_base_sha) = if git_clean {
+    let (worktree_work_dir, _worktree_path, worktree_branch, worktree_base_sha) = if git_clean {
         match setup_worktree(&original_cwd, &logs_dir, &run_id) {
             Ok((wd, wt, branch, base)) => (Some(wd), Some(wt), Some(branch), Some(base)),
             Err(e) => {
@@ -617,7 +617,11 @@ pub async fn run_command(
     {
         let sandbox_info_opt = {
             let info = sandbox.sandbox_info();
-            if info.is_empty() { None } else { Some(info) }
+            if info.is_empty() {
+                None
+            } else {
+                Some(info)
+            }
         };
         let record = match sandbox_provider {
             SandboxProvider::Local => crate::sandbox_record::SandboxRecord {
@@ -933,11 +937,8 @@ pub async fn run_command(
     };
     let run_duration_ms = run_start.elapsed().as_millis() as u64;
 
-    // Restore cwd and clean up worktree (best-effort)
+    // Restore cwd (worktree is kept for `arc cp` access; pruned separately)
     let _ = std::env::set_current_dir(&original_cwd);
-    if let Some(ref wt) = worktree_path {
-        let _ = crate::git::remove_worktree(&original_cwd, wt);
-    }
 
     {
         let (status, failure_reason) = match &engine_result {
@@ -1447,11 +1448,8 @@ async fn run_from_branch(
         .await;
     let run_duration_ms = run_start.elapsed().as_millis() as u64;
 
-    // Clean up
+    // Restore cwd (worktree is kept for `arc cp` access; pruned separately)
     let _ = std::env::set_current_dir(&original_cwd);
-    if let Some(ref wt) = worktree_path {
-        let _ = crate::git::remove_worktree(&original_cwd, wt);
-    }
     if sandbox_provider == SandboxProvider::Exe {
         let _ = sandbox.cleanup().await;
     }
@@ -2258,4 +2256,4 @@ mod tests {
         let parsed: serde_json::Value = serde_json::from_str(&redacted).unwrap();
         assert_eq!(parsed["run_id"], "def-456");
     }
-}
\ No newline at end of file
+}
diff --git a/crates/arc-workflows/src/cli/runs.rs b/crates/arc-workflows/src/cli/runs.rs
index a6a2d9fc2..afde94821 100644
--- a/crates/arc-workflows/src/cli/runs.rs
+++ b/crates/arc-workflows/src/cli/runs.rs
@@ -660,4 +660,4 @@ mod tests {
         let result = parse_label_filters(&args);
         assert!(result.is_empty());
     }
-}
\ No newline at end of file
+}
diff --git a/crates/arc-workflows/src/sandbox_record.rs b/crates/arc-workflows/src/sandbox_record.rs
index 15dab4431..167cf79f8 100644
--- a/crates/arc-workflows/src/sandbox_record.rs
+++ b/crates/arc-workflows/src/sandbox_record.rs
@@ -81,10 +81,7 @@ mod tests {
             loaded.host_working_directory.as_deref(),
             Some("/home/user/project")
         );
-        assert_eq!(
-            loaded.container_mount_point.as_deref(),
-            Some("/workspace")
-        );
+        assert_eq!(loaded.container_mount_point.as_deref(), Some("/workspace"));
         assert!(loaded.data_host.is_none());
     }
 
diff --git a/crates/arc-workflows/tests/cp_integration.rs b/crates/arc-workflows/tests/cp_integration.rs
new file mode 100644
index 000000000..a4e8a6ec0
--- /dev/null
+++ b/crates/arc-workflows/tests/cp_integration.rs
@@ -0,0 +1,303 @@
+//! E2E tests for `arc cp` against local and Docker sandbox backends.
+//!
+//! Local tests run without `#[ignore]` (no external dependencies).
+//! Docker tests require a Docker daemon and are marked `#[ignore]`.
+//! Run Docker tests with: `cargo test --package arc-workflows --test cp_integration -- --ignored`
+
+use arc_workflows::cli::cp::reconnect;
+use arc_workflows::sandbox_record::SandboxRecord;
+
+// ---------------------------------------------------------------------------
+// Local sandbox
+// ---------------------------------------------------------------------------
+
+fn local_record(working_directory: &std::path::Path) -> SandboxRecord {
+    SandboxRecord {
+        provider: "local".to_string(),
+        working_directory: working_directory.to_string_lossy().to_string(),
+        identifier: None,
+        host_working_directory: None,
+        container_mount_point: None,
+        data_host: None,
+    }
+}
+
+#[tokio::test]
+async fn local_cp_upload_download_round_trip() {
+    let sandbox_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = local_record(sandbox_dir.path());
+    let sandbox = reconnect(&record).await.expect("reconnect local");
+
+    // Upload a text file
+    let content = b"hello from local cp test\n";
+    let local_src = scratch.path().join("upload.txt");
+    std::fs::write(&local_src, content).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "cp_test.txt")
+        .await
+        .expect("upload text");
+
+    // Verify it landed in the sandbox working directory
+    assert!(sandbox_dir.path().join("cp_test.txt").exists());
+
+    // Download it back
+    let local_dst = scratch.path().join("download.txt");
+    sandbox
+        .download_file_to_local("cp_test.txt", &local_dst)
+        .await
+        .expect("download text");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), content);
+}
+
+#[tokio::test]
+async fn local_cp_binary_round_trip() {
+    let sandbox_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = local_record(sandbox_dir.path());
+    let sandbox = reconnect(&record).await.expect("reconnect local");
+
+    // All 256 byte values
+    let binary: Vec<u8> = (0..=255).collect();
+    let local_src = scratch.path().join("binary.bin");
+    std::fs::write(&local_src, &binary).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "binary.bin")
+        .await
+        .expect("upload binary");
+
+    let local_dst = scratch.path().join("binary_dl.bin");
+    sandbox
+        .download_file_to_local("binary.bin", &local_dst)
+        .await
+        .expect("download binary");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), binary);
+}
+
+#[tokio::test]
+async fn local_cp_creates_parent_dirs() {
+    let sandbox_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = local_record(sandbox_dir.path());
+    let sandbox = reconnect(&record).await.expect("reconnect local");
+
+    let content = b"nested file\n";
+    let local_src = scratch.path().join("nested.txt");
+    std::fs::write(&local_src, content).unwrap();
+
+    // Upload to a nested path that doesn't exist yet
+    sandbox
+        .upload_file_from_local(&local_src, "a/b/c/nested.txt")
+        .await
+        .expect("upload to nested path");
+
+    assert!(sandbox_dir.path().join("a/b/c/nested.txt").exists());
+
+    // Download to a nested local path that doesn't exist yet
+    let local_dst = scratch.path().join("x/y/z/nested.txt");
+    sandbox
+        .download_file_to_local("a/b/c/nested.txt", &local_dst)
+        .await
+        .expect("download to nested path");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), content);
+}
+
+#[tokio::test]
+async fn local_cp_record_save_load_round_trip() {
+    let sandbox_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = local_record(sandbox_dir.path());
+    let path = scratch.path().join("sandbox.json");
+    record.save(&path).unwrap();
+
+    let loaded = SandboxRecord::load(&path).unwrap();
+    assert_eq!(loaded.provider, "local");
+    assert_eq!(loaded.working_directory, record.working_directory);
+    assert!(loaded.identifier.is_none());
+
+    // Reconnect from the loaded record still works
+    let sandbox = reconnect(&loaded).await.expect("reconnect from loaded");
+    assert_eq!(sandbox.working_directory(), record.working_directory);
+}
+
+// ---------------------------------------------------------------------------
+// Docker sandbox
+// ---------------------------------------------------------------------------
+
+fn docker_record(host_dir: &std::path::Path, mount_point: &str) -> SandboxRecord {
+    SandboxRecord {
+        provider: "docker".to_string(),
+        working_directory: mount_point.to_string(),
+        identifier: None,
+        host_working_directory: Some(host_dir.to_string_lossy().to_string()),
+        container_mount_point: Some(mount_point.to_string()),
+        data_host: None,
+    }
+}
+
+#[tokio::test]
+#[ignore] // requires Docker daemon
+async fn docker_cp_upload_download_round_trip() {
+    let host_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = docker_record(host_dir.path(), "/workspace");
+    let sandbox = reconnect(&record).await.expect("reconnect docker");
+
+    // Upload a text file
+    let content = b"hello from docker cp test\n";
+    let local_src = scratch.path().join("upload.txt");
+    std::fs::write(&local_src, content).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "cp_test.txt")
+        .await
+        .expect("upload text");
+
+    // Verify it landed on the host filesystem (bind mount path)
+    assert!(host_dir.path().join("cp_test.txt").exists());
+    assert_eq!(
+        std::fs::read(host_dir.path().join("cp_test.txt")).unwrap(),
+        content
+    );
+
+    // Download it back
+    let local_dst = scratch.path().join("download.txt");
+    sandbox
+        .download_file_to_local("cp_test.txt", &local_dst)
+        .await
+        .expect("download text");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), content);
+}
+
+#[tokio::test]
+#[ignore] // requires Docker daemon
+async fn docker_cp_binary_round_trip() {
+    let host_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = docker_record(host_dir.path(), "/workspace");
+    let sandbox = reconnect(&record).await.expect("reconnect docker");
+
+    let binary: Vec<u8> = (0..=255).collect();
+    let local_src = scratch.path().join("binary.bin");
+    std::fs::write(&local_src, &binary).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "binary.bin")
+        .await
+        .expect("upload binary");
+
+    let local_dst = scratch.path().join("binary_dl.bin");
+    sandbox
+        .download_file_to_local("binary.bin", &local_dst)
+        .await
+        .expect("download binary");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), binary);
+}
+
+#[tokio::test]
+#[ignore] // requires Docker daemon
+async fn docker_cp_creates_parent_dirs() {
+    let host_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = docker_record(host_dir.path(), "/workspace");
+    let sandbox = reconnect(&record).await.expect("reconnect docker");
+
+    let content = b"nested docker file\n";
+    let local_src = scratch.path().join("nested.txt");
+    std::fs::write(&local_src, content).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "deep/nested/file.txt")
+        .await
+        .expect("upload to nested path");
+
+    assert!(host_dir.path().join("deep/nested/file.txt").exists());
+
+    let local_dst = scratch.path().join("p/q/file.txt");
+    sandbox
+        .download_file_to_local("deep/nested/file.txt", &local_dst)
+        .await
+        .expect("download to nested path");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), content);
+}
+
+#[tokio::test]
+#[ignore] // requires Docker daemon
+async fn docker_cp_custom_mount_point() {
+    let host_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    // Use a non-default mount point
+    let record = docker_record(host_dir.path(), "/app");
+    let sandbox = reconnect(&record).await.expect("reconnect docker");
+
+    let content = b"custom mount\n";
+    let local_src = scratch.path().join("mount.txt");
+    std::fs::write(&local_src, content).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "mount.txt")
+        .await
+        .expect("upload with custom mount");
+
+    assert!(host_dir.path().join("mount.txt").exists());
+
+    let local_dst = scratch.path().join("mount_dl.txt");
+    sandbox
+        .download_file_to_local("mount.txt", &local_dst)
+        .await
+        .expect("download with custom mount");
+
+    assert_eq!(std::fs::read(&local_dst).unwrap(), content);
+}
+
+#[tokio::test]
+#[ignore] // requires Docker daemon
+async fn docker_cp_record_save_load_round_trip() {
+    let host_dir = tempfile::tempdir().unwrap();
+    let scratch = tempfile::tempdir().unwrap();
+
+    let record = docker_record(host_dir.path(), "/workspace");
+    let path = scratch.path().join("sandbox.json");
+    record.save(&path).unwrap();
+
+    let loaded = SandboxRecord::load(&path).unwrap();
+    assert_eq!(loaded.provider, "docker");
+    assert_eq!(
+        loaded.host_working_directory.as_deref(),
+        Some(host_dir.path().to_str().unwrap())
+    );
+    assert_eq!(loaded.container_mount_point.as_deref(), Some("/workspace"));
+
+    // Reconnect from the loaded record still works
+    let sandbox = reconnect(&loaded).await.expect("reconnect from loaded");
+
+    let content = b"from loaded record\n";
+    let local_src = scratch.path().join("loaded.txt");
+    std::fs::write(&local_src, content).unwrap();
+
+    sandbox
+        .upload_file_from_local(&local_src, "loaded.txt")
+        .await
+        .expect("upload via loaded record");
+
+    assert_eq!(
+        std::fs::read(host_dir.path().join("loaded.txt")).unwrap(),
+        content
+    );
+}
diff --git a/crates/arc-workflows/tests/daytona_integration.rs b/crates/arc-workflows/tests/daytona_integration.rs
index d599f9b55..a41a7485f 100644
--- a/crates/arc-workflows/tests/daytona_integration.rs
+++ b/crates/arc-workflows/tests/daytona_integration.rs
@@ -1743,3 +1743,104 @@ async fn daytona_toolbox_idle_diagnostic() {
     eprintln!("\n=== PASS: all idle durations survived ===");
     env.cleanup().await.unwrap();
 }
+
+/// E2E test for `arc cp` against a live Daytona sandbox.
+///
+/// Creates a sandbox, saves a SandboxRecord, reconnects via `cp::reconnect`,
+/// uploads a file, downloads it back, and verifies the round-trip.
+#[tokio::test]
+#[ignore]
+async fn daytona_cp_upload_download_round_trip() {
+    use arc_workflows::cli::cp::reconnect;
+    use arc_workflows::sandbox_record::SandboxRecord;
+
+    // 1. Create and initialize a real Daytona sandbox
+    let env = create_env().await;
+    env.initialize().await.unwrap();
+
+    let sandbox_name = env.sandbox_info();
+    assert!(
+        !sandbox_name.is_empty(),
+        "sandbox_info() should return the Daytona sandbox name"
+    );
+
+    // 2. Build a SandboxRecord (same as `arc run` would persist)
+    let record = SandboxRecord {
+        provider: "daytona".to_string(),
+        working_directory: env.working_directory().to_string(),
+        identifier: Some(sandbox_name.clone()),
+        host_working_directory: None,
+        container_mount_point: None,
+        data_host: None,
+    };
+
+    // 3. Save to temp dir and reload (verify serialization round-trip)
+    let tmp = tempfile::tempdir().unwrap();
+    let record_path = tmp.path().join("sandbox.json");
+    record.save(&record_path).unwrap();
+    let loaded = SandboxRecord::load(&record_path).unwrap();
+    assert_eq!(loaded.provider, "daytona");
+    assert_eq!(loaded.identifier.as_deref(), Some(sandbox_name.as_str()));
+
+    // 4. Reconnect via the real cp::reconnect path
+    let reconnected = reconnect(&loaded).await.expect("reconnect should succeed");
+
+    // 5. Upload: write a local file, then upload it to the sandbox
+    let upload_content = b"hello from arc cp e2e test\n";
+    let local_upload = tmp.path().join("upload.txt");
+    std::fs::write(&local_upload, upload_content).unwrap();
+
+    reconnected
+        .upload_file_from_local(&local_upload, "cp_test_upload.txt")
+        .await
+        .expect("upload_file_from_local should succeed");
+
+    // 6. Verify the file exists in the sandbox via the original connection
+    assert!(
+        env.file_exists("cp_test_upload.txt").await.unwrap(),
+        "uploaded file should exist in the sandbox"
+    );
+    let remote_content = env
+        .read_file("cp_test_upload.txt", None, None)
+        .await
+        .unwrap();
+    assert!(
+        remote_content.contains("hello from arc cp e2e test"),
+        "expected uploaded content in sandbox, got: {remote_content}"
+    );
+
+    // 7. Download: retrieve the file back to local via the reconnected sandbox
+    let local_download = tmp.path().join("download.txt");
+    reconnected
+        .download_file_to_local("cp_test_upload.txt", &local_download)
+        .await
+        .expect("download_file_to_local should succeed");
+
+    let downloaded = std::fs::read(&local_download).unwrap();
+    assert_eq!(downloaded, upload_content);
+
+    // 8. Upload a binary file to test non-UTF-8 content
+    let binary_content: Vec<u8> = (0..=255).collect();
+    let local_binary = tmp.path().join("binary.bin");
+    std::fs::write(&local_binary, &binary_content).unwrap();
+
+    reconnected
+        .upload_file_from_local(&local_binary, "cp_test_binary.bin")
+        .await
+        .expect("binary upload should succeed");
+
+    let local_binary_dl = tmp.path().join("binary_dl.bin");
+    reconnected
+        .download_file_to_local("cp_test_binary.bin", &local_binary_dl)
+        .await
+        .expect("binary download should succeed");
+
+    let downloaded_binary = std::fs::read(&local_binary_dl).unwrap();
+    assert_eq!(
+        downloaded_binary, binary_content,
+        "binary round-trip should be exact"
+    );
+
+    // 9. Cleanup
+    env.cleanup().await.unwrap();
+}
diff --git a/crates/arc-workflows/tests/integration.rs b/crates/arc-workflows/tests/integration.rs
index 7ad76f5ce..dd5eec2cb 100644
--- a/crates/arc-workflows/tests/integration.rs
+++ b/crates/arc-workflows/tests/integration.rs
@@ -8926,7 +8926,11 @@ impl arc_agent::Sandbox for RemoteMockEnv {
         Err("not implemented".to_string())
     }
 
-    async fn upload_file_from_local(&self, _: &std::path::Path, _: &str) -> std::result::Result<(), String> {
+    async fn upload_file_from_local(
+        &self,
+        _: &std::path::Path,
+        _: &str,
+    ) -> std::result::Result<(), String> {
         Err("not implemented".to_string())
     }
 
@@ -13256,4 +13260,4 @@ async fn wait_timer_e2e() {
     };
     let outcome = engine.run(&graph, &config).await.expect("run");
     assert_eq!(outcome.status, StageStatus::Success);
-}
\ No newline at end of file
+}