What causes "sandbox: create input directory: %w" in Tencent/WeKnora?

Check the wrapped error for permission vs. invalid-path causes.

sandbox: create input directory: %w

Error message

sandbox: create input directory: %w

What it means

WriteSessionInputFile resolves the session (provisioning the sandbox if needed via resolveSession) and first creates the parent directory of the cleaned target path with MakeDir, wrapped as "sandbox: create input directory". It indicates the parent directory for a staged attachment could not be created in the remote sandbox.

Source

Thrown at internal/sandbox/session_manager.go:521

func (m *SessionBoundManager) WriteSessionInputFile(
	ctx context.Context, sessionID, filePath string, content []byte,
) error {
	if err := m.requireRemoteBackend(); err != nil {
		return err
	}
	if strings.TrimSpace(sessionID) == "" {
		return errors.New("sandbox: session ID required for input staging")
	}
	clean, err := cleanSessionInputPath(filePath)
	if err != nil {
		return err
	}
	handle, err := m.resolveSession(ctx, sessionID)
	if err != nil {
		return err
	}
	if err := ignoreExistingDir(m.client.MakeDir(ctx, handle, path.Dir(clean))); err != nil {
		return fmt.Errorf("sandbox: create input directory: %w", err)
	}
	if err := m.client.WriteFile(ctx, handle, clean, content); err != nil {
		return fmt.Errorf("sandbox: write session input %s: %w", clean, err)
	}
	return nil
}

// WriteSessionWorkspaceFile writes a model-authored file into the session's
// remote sandbox, provisioning the sandbox on first call. Paths must sit
// under /workspace and must not land in /workspace/input.
func (m *SessionBoundManager) WriteSessionWorkspaceFile(
	ctx context.Context, sessionID, filePath string, content []byte,
) error {
	if err := m.requireRemoteBackend(); err != nil {
		return err
	}
	if strings.TrimSpace(sessionID) == "" {
		return errors.New("sandbox: session ID required for workspace write")

View on GitHub (pinned to 988cbb0330)

Solutions

Check the wrapped error for permission vs. invalid-path causes.
Ensure the target path resolves under the session input root and uses provider-safe characters.
Verify the sandbox is still alive and re-resolve the session, then retry.
Check provider disk/quota limits.

Example fix

// before
err := mgr.WriteSessionInputFile(ctx, sessionID, "../../etc/evil.txt", data)
// after
clean := path.Clean(filepath.Join("/inputs", attachmentName))
err := mgr.WriteSessionInputFile(ctx, sessionID, clean, data)

Defensive patterns

Strategy: validation

Validate before calling

// validate the attachment path before writing
func validInputPath(p string) bool {
    clean := path.Clean(p)
    return path.IsAbs(clean) && !strings.Contains(clean, "..") &&
        strings.HasPrefix(clean, "/inputs/")
}

Try / catch

if err := mgr.WriteSessionInputFile(ctx, sessionID, p, data); err != nil {
    if strings.Contains(err.Error(), "create input directory") {
        // sandbox may have expired mid-call: re-resolve and retry once
        return mgr.WriteSessionInputFile(ctx, sessionID, p, data)
    }
    return err
}

Prevention

Sanitize attachment filenames (strip odd characters, force clean absolute paths under the input root).
Keep attachments within expected size limits to avoid slow uploads expiring the sandbox.
Check sandbox liveness before long write sequences.
Log the wrapped error chain to distinguish mkdir vs. write failures.

When it happens

Trigger: Calling WriteSessionInputFile when MakeDir on path.Dir(clean) fails after resolveSession succeeded — e.g. permission denied, invalid parent path, sandbox terminated between provision and mkdir, or provider API error.

Common situations: Attachment path with unexpected characters or bad nesting, sandbox image restricting writes to the input root, provider quota exceeded, or race with sandbox cleanup.

Related errors

AI-assisted analysis of Tencent/WeKnora@988cbb0330 (2026-09-02). Data as JSON: /api/errors/d9b7474de75af9f5. Report an issue: GitHub.