Address remaining review items: L4/M1 + L2/L5 cleanup

- L4: sync_bedrock_credentials (renamed from write_bedrock_static_
  credentials) now also clears a stale ~/.aws/credentials when the
  project no longer uses static-credential Bedrock, so static keys don't
  linger unused in the persistent home volume after switching backends.
  Skipped when /tmp/.host-aws is mounted (host-managed ~/.aws). HOME is
  also set explicitly on the exec env for robustness.
- M1: the Backup button now has a tooltip and the success toast notes
  that the archive includes MCP/config which may contain MCP-embedded
  API keys (OAuth tokens are excluded) — keep it private.
- L2: backup now uses async file IO (tokio::fs::File + AsyncWriteExt,
  tokio::fs::remove_file) instead of blocking std::fs between awaits;
  dropped-file reads use tokio::fs::metadata/read.
- L5: upload_host_file_to_terminal explicitly `mkdir -p`s
  /tmp/triple-c-drops instead of relying on Docker's tar extractor to
  create the parent dir.

Verified L4 cleanup guard, L5 mkdir, async IO, and exit-code paths
against real containers. cargo check / tsc / vitest all pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src-tauri/src/commands/file_commands.rs

@@ -254,10 +254,11 @@ rm -rf "$STAGE""#;
         StartExecResults::Detached => return Err("Backup exec started detached".to_string()),
     };
 
-    use std::io::Write;
-    let file =
-        std::fs::File::create(&host_path).map_err(|e| format!("Failed to create backup file: {}", e))?;
-    let mut writer = std::io::BufWriter::new(file);
+    use tokio::io::AsyncWriteExt;
+    let file = tokio::fs::File::create(&host_path)
+        .await
+        .map_err(|e| format!("Failed to create backup file: {}", e))?;
+    let mut writer = tokio::io::BufWriter::new(file);
     let mut total: u64 = 0;
     let mut stderr_text = String::new();
     let mut stream_err: Option<String> = None;
@@ -265,7 +266,7 @@ rm -rf "$STAGE""#;
     while let Some(msg) = output.next().await {
         match msg {
             Ok(LogOutput::StdOut { message }) => {
-                if let Err(e) = writer.write_all(&message) {
+                if let Err(e) = writer.write_all(&message).await {
                     stream_err = Some(format!("Failed to write backup file: {}", e));
                     break;
                 }
@@ -282,7 +283,7 @@ rm -rf "$STAGE""#;
         }
     }
     if stream_err.is_none() {
-        if let Err(e) = writer.flush() {
+        if let Err(e) = writer.flush().await {
             stream_err = Some(format!("Failed to finalize backup file: {}", e));
         }
     }
@@ -321,7 +322,7 @@ rm -rf "$STAGE""#;
 
     if let Some(err) = stream_err {
         // Don't leave a partial/corrupt archive behind.
-        let _ = std::fs::remove_file(&host_path);
+        let _ = tokio::fs::remove_file(&host_path).await;
         return Err(err);
     }
 

app/src-tauri/src/commands/project_commands.rs

@@ -432,11 +432,11 @@ pub async fn start_project_container(
             new_id
         };
 
-        // Refresh Bedrock static/session credentials on every start so rotated
-        // keys are picked up without a full container recreation. No-op for
-        // other backends / auth methods.
-        if let Err(e) = docker::write_bedrock_static_credentials(&container_id, &project).await {
-            log::warn!("Failed to refresh AWS credentials for project {}: {}", project.id, e);
+        // Sync Bedrock credentials on every start: refresh static/session creds
+        // so rotated keys are picked up without a full container recreation, and
+        // clear stale creds when the project no longer uses static-cred Bedrock.
+        if let Err(e) = docker::sync_bedrock_credentials(&container_id, &project).await {
+            log::warn!("Failed to sync AWS credentials for project {}: {}", project.id, e);
         }
 
         Ok(container_id)

app/src-tauri/src/commands/terminal_commands.rs

@@ -196,7 +196,8 @@ pub async fn upload_host_file_to_terminal(
 ) -> Result<String, String> {
     let container_id = state.exec_manager.get_container_id(&session_id).await?;
 
-    let meta = std::fs::metadata(&host_path)
+    let meta = tokio::fs::metadata(&host_path)
+        .await
         .map_err(|e| format!("Cannot access {}: {}", host_path, e))?;
     if meta.is_dir() {
         return Err(format!("{} is a directory — drop individual files", host_path));
@@ -213,8 +214,9 @@ pub async fn upload_host_file_to_terminal(
         ));
     }
 
-    let data =
-        std::fs::read(&host_path).map_err(|e| format!("Failed to read {}: {}", host_path, e))?;
+    let data = tokio::fs::read(&host_path)
+        .await
+        .map_err(|e| format!("Failed to read {}: {}", host_path, e))?;
 
     let base = std::path::Path::new(&host_path)
         .file_name()
@@ -222,6 +224,14 @@ pub async fn upload_host_file_to_terminal(
         .filter(|s| !s.is_empty())
         .unwrap_or_else(|| "dropped-file".to_string());
 
+    // Ensure the destination directory exists rather than relying on Docker's
+    // archive extractor to create the parent for the uploaded tar entry.
+    crate::docker::exec::exec_oneshot(
+        &container_id,
+        vec!["mkdir".to_string(), "-p".to_string(), "/tmp/triple-c-drops".to_string()],
+    )
+    .await?;
+
     let file_name = format!("triple-c-drops/{}", base);
     state
         .exec_manager

app/src-tauri/src/docker/container.rs

@@ -1097,36 +1097,61 @@ pub fn get_snapshot_image_name(project: &Project) -> String {
     format!("triple-c-snapshot-{}:latest", project.id)
 }
 
-/// Write Bedrock static/session credentials into the running container's
-/// ~/.aws/credentials file. Called on every container start (not just creation)
-/// so rotated keys or refreshed session tokens are picked up without recreating
-/// the container. Credentials are passed via the exec environment (not argv) and
-/// the file is written with 0600 permissions. No-op unless the project uses
-/// Bedrock with static-credential auth.
-pub async fn write_bedrock_static_credentials(
+/// Keep the container's `~/.aws/credentials` in sync with the project's Bedrock
+/// auth on every container start:
+///   - **Bedrock + static credentials**: (re)write `~/.aws/credentials` from the
+///     latest keychain values and drop a stale `~/.aws/config` left by a prior
+///     profile/SSO session, so rotated keys are picked up without recreating the
+///     container.
+///   - **Any other backend / auth method**: remove a stale `~/.aws/credentials`
+///     written by a previous static-credential session, so the secrets don't
+///     linger unused in the persistent home volume after switching away.
+///
+/// Both cleanups are skipped when `/tmp/.host-aws` is mounted (a global
+/// `aws_config_path` is configured), since the entrypoint already refreshes
+/// `~/.aws` from the host on every start in that case.
+pub async fn sync_bedrock_credentials(
     container_id: &str,
     project: &Project,
 ) -> Result<(), String> {
-    if project.backend != Backend::Bedrock {
-        return Ok(());
-    }
-    let bedrock = match project.bedrock_config {
-        Some(ref b) if b.auth_method == BedrockAuthMethod::StaticCredentials => b,
-        _ => return Ok(()),
+    let static_bedrock = if project.backend == Backend::Bedrock {
+        project
+            .bedrock_config
+            .as_ref()
+            .filter(|b| b.auth_method == BedrockAuthMethod::StaticCredentials)
+    } else {
+        None
     };
 
-    let key_id = match bedrock.aws_access_key_id.as_deref() {
-        Some(k) if !k.is_empty() => k,
+    let bedrock = match static_bedrock {
+        Some(b) if b.aws_access_key_id.as_deref().is_some_and(|k| !k.is_empty()) => b,
         _ => {
+            // Not static-credential Bedrock (or static selected but no key set):
+            // remove a stale credentials file from a previous static session.
+            if matches!(static_bedrock, Some(_)) {
                 log::warn!("Bedrock static auth selected but no AWS access key id is set");
+            }
+            let script = r#"if [ ! -d /tmp/.host-aws ]; then rm -f "$HOME/.aws/credentials"; fi"#;
+            let cmd = vec!["sh".to_string(), "-c".to_string(), script.to_string()];
+            let env = vec!["HOME=/home/claude".to_string()];
+            if let Err(e) = crate::docker::exec::exec_oneshot_env(container_id, cmd, env).await {
+                log::warn!(
+                    "Failed to clear stale AWS credentials in container {}: {}",
+                    container_id,
+                    e
+                );
+            }
             return Ok(());
         }
     };
+
+    let key_id = bedrock.aws_access_key_id.as_deref().unwrap_or("");
     let secret = bedrock.aws_secret_access_key.as_deref().unwrap_or("");
 
     // Pass secrets via the exec environment, then have the shell write them to
     // the file. This keeps them out of the process argv (visible via `ps`).
     let mut env = vec![
+        "HOME=/home/claude".to_string(),
         format!("TC_AWS_KEY_ID={}", key_id),
         format!("TC_AWS_SECRET={}", secret),
     ];

app/src/components/projects/ProjectCard.tsx

@@ -196,7 +196,7 @@ export default function ProjectCard({ project }: Props) {
       setError(null);
       const bytes = await commands.downloadContainerBackup(project.id, hostPath);
       const mb = (bytes / (1024 * 1024)).toFixed(1);
-      setProgressMsg(`Backup saved (${mb} MB)`);
+      setProgressMsg(`Backup saved (${mb} MB). Note: includes MCP/config — may contain MCP API keys. Keep it private.`);
     } catch (e) {
       setError(String(e));
     } finally {
@@ -531,7 +531,12 @@ export default function ProjectCard({ project }: Props) {
                 <ActionButton onClick={handleOpenTerminal} disabled={loading} label="Terminal" accent />
                 <ActionButton onClick={handleOpenBashShell} disabled={loading} label="Shell" />
                 <ActionButton onClick={() => setShowFileManager(true)} disabled={loading} label="Files" />
-                <ActionButton onClick={handleBackup} disabled={loading || backingUp} label={backingUp ? "Backing up…" : "Backup"} />
+                <ActionButton
+                  onClick={handleBackup}
+                  disabled={loading || backingUp}
+                  label={backingUp ? "Backing up…" : "Backup"}
+                  title="Downloads /workspace plus a sanitized home config (MCP servers, settings, skills). OAuth tokens are excluded, but MCP server configs may embed their own API keys/tokens — keep the archive private."
+                />
               </>
             ) : (
               <>
@@ -1221,12 +1226,14 @@ function ActionButton({
   label,
   accent,
   danger,
+  title,
 }: {
   onClick: (e?: React.MouseEvent) => void;
   disabled: boolean;
   label: string;
   accent?: boolean;
   danger?: boolean;
+  title?: string;
 }) {
   let color = "text-[var(--text-secondary)] hover:text-[var(--text-primary)]";
   if (accent) color = "text-[var(--accent)] hover:text-[var(--accent-hover)]";
@@ -1236,6 +1243,7 @@ function ActionButton({
     <button
       onClick={(e) => { e.stopPropagation(); onClick(e); }}
       disabled={disabled}
+      title={title}
       className={`text-xs px-2 py-0.5 rounded transition-colors disabled:opacity-50 ${color} hover:bg-[var(--bg-primary)]`}
     >
       {label}