toolsrv: fix ReadAt offset for request-response files

After Write(), the file offset is at the end of the written data.
For request-response files (like proc/new), we need to read the
result from offset 0, not from the current offset.

Changed CallTool() to use ReadAt(buf, 0) instead of io.ReadAll()
which uses Read() and inherits the wrong offset.

Same fix was already applied to token reading in Dial().

Added TestIntegration_ToolExecution to verify the full tool
execution path works end-to-end.

toolsrv/client9p.go

@@ -148,9 +148,22 @@ func (c *Conn) CallTool(ctx context.Context, name string, args json.RawMessage)
 		return nil, fmt.Errorf("write: %w", err)
 	}
 
-	result, err := io.ReadAll(fid)
-	if err != nil {
-		return nil, fmt.Errorf("read: %w", err)
+	// Read result from offset 0 (Write advances the file offset, but
+	// for request-response files we need to read the result from the start)
+	var result []byte
+	buf := make([]byte, 8192)
+	for offset := int64(0); ; {
+		n, err := fid.ReadAt(buf, offset)
+		if n > 0 {
+			result = append(result, buf[:n]...)
+			offset += int64(n)
+		}
+		if err == io.EOF || n == 0 {
+			break
+		}
+		if err != nil {
+			return nil, fmt.Errorf("read: %w", err)
+		}
 	}
 
 	return json.RawMessage(result), nil

toolsrv/integration_test.go

@@ -6,10 +6,12 @@ package toolsrv
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 )
@@ -208,6 +210,53 @@ func TestIntegration_BasicOperations(t *testing.T) {
 	t.Logf("ListTools returned %d tools", len(tools))
 }
 
+func TestIntegration_ToolExecution(t *testing.T) {
+	socketPath, cleanup := startTestServer(t)
+	defer cleanup()
+
+	conn, err := Dial(socketPath, "test-secret-exec")
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+	defer conn.Close()
+
+	// Load the shell tool
+	if err := conn.LoadTool("shell"); err != nil {
+		t.Fatalf("LoadTool failed: %v", err)
+	}
+
+	// Verify it's loaded
+	tools, err := conn.ListTools()
+	if err != nil {
+		t.Fatalf("ListTools failed: %v", err)
+	}
+	found := false
+	for _, tool := range tools {
+		if tool.Name == "shell" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Fatal("shell tool not found after loading")
+	}
+
+	// Execute a tool
+	ctx := context.Background()
+	args := json.RawMessage(`{"cmd": "echo hello from test"}`)
+	result, err := conn.CallTool(ctx, "shell", args)
+	if err != nil {
+		t.Fatalf("CallTool failed: %v", err)
+	}
+
+	// Result should be JSON containing the output
+	resultStr := string(result)
+	if !strings.Contains(resultStr, "hello from test") {
+		t.Errorf("unexpected result: %s", resultStr)
+	}
+	t.Logf("Tool result: %s", resultStr)
+}
+
 func TestIntegration_ProcessKeeperReconnect(t *testing.T) {
 	socketPath, cleanup := startTestServer(t)
 	defer cleanup()