diff --git a/cmd/picoclaw/internal/gateway/command.go b/cmd/picoclaw/internal/gateway/command.go
index 66a56f9ce..bfa69f072 100644
--- a/cmd/picoclaw/internal/gateway/command.go
+++ b/cmd/picoclaw/internal/gateway/command.go
@@ -1,23 +1,42 @@
 package gateway
 
 import (
+	"fmt"
+
 	"github.com/spf13/cobra"
+
+	"github.com/sipeed/picoclaw/pkg/logger"
+	"github.com/sipeed/picoclaw/pkg/utils"
 )
 
 func NewGatewayCommand() *cobra.Command {
 	var debug bool
+	var noTruncate bool
 
 	cmd := &cobra.Command{
 		Use:     "gateway",
 		Aliases: []string{"g"},
 		Short:   "Start picoclaw gateway",
 		Args:    cobra.NoArgs,
+		PreRunE: func(_ *cobra.Command, _ []string) error {
+			if noTruncate && !debug {
+				return fmt.Errorf("the --no-truncate option can only be used in conjunction with --debug (-d)")
+			}
+
+			if noTruncate {
+				utils.SetDisableTruncation(true)
+				logger.Info("String truncation is globally disabled via 'no-truncate' flag")
+			}
+
+			return nil
+		},
 		RunE: func(_ *cobra.Command, _ []string) error {
 			return gatewayCmd(debug)
 		},
 	}
 
 	cmd.Flags().BoolVarP(&debug, "debug", "d", false, "Enable debug logging")
+	cmd.Flags().BoolVarP(&noTruncate, "no-truncate", "T", false, "Disable string truncation in debug logs")
 
 	return cmd
 }
diff --git a/docs/debug.md b/docs/debug.md
new file mode 100644
index 000000000..7e28a15f2
--- /dev/null
+++ b/docs/debug.md
@@ -0,0 +1,33 @@
+# Debugging PicoClaw
+
+PicoClaw performs multiple complex interactions under the hood for every single request it receives—from routing messages and evaluating complexity, to executing tools and adapting to model failures. Being able to see exactly what is happening is crucial, not just for troubleshooting potential issues, but also for truly understanding how the agent operates.
+## Starting PicoClaw in Debug Mode
+
+To get detailed information about what the agent is doing (LLM requests, tool calls, message routing), you can start the PicoClaw gateway with the debug flag:
+
+```bash
+picoclaw gateway --debug
+# or
+picoclaw gateway -d
+```
+
+In this mode, the system will format the logs extensively and display previews of system prompts and tool execution results.
+
+## Disabling Log Truncation (Full Logs)
+
+By default, PicoClaw truncates very long strings (such as the *System Prompt* or large JSON output results) in the debug logs to keep the console readable.
+
+If you need to inspect the complete output of a command or the exact payload sent to the LLM model, you can use the `--no-truncate` flag.
+
+**Note:** This flag *only* works when combined with the `--debug` mode.
+
+```bash
+picoclaw gateway --debug --no-truncate
+
+```
+
+When this flag is active, the global truncation function is disabled. This is extremely useful for:
+
+* Verifying the exact syntax of the messages sent to the provider.
+* Reading the complete output of tools like `exec`, `web_fetch`, or `read_file`.
+* Debugging the session history saved in memory.
diff --git a/pkg/agent/context.go b/pkg/agent/context.go
index 33fe26001..5a84c45e2 100644
--- a/pkg/agent/context.go
+++ b/pkg/agent/context.go
@@ -16,6 +16,7 @@ import (
 	"github.com/sipeed/picoclaw/pkg/logger"
 	"github.com/sipeed/picoclaw/pkg/providers"
 	"github.com/sipeed/picoclaw/pkg/skills"
+	"github.com/sipeed/picoclaw/pkg/utils"
 )
 
 type ContextBuilder struct {
@@ -538,10 +539,7 @@ func (cb *ContextBuilder) BuildMessages(
 		})
 
 	// Log preview of system prompt (avoid logging huge content)
-	preview := fullSystemPrompt
-	if len(preview) > 500 {
-		preview = preview[:500] + "... (truncated)"
-	}
+	preview := utils.Truncate(fullSystemPrompt, 500)
 	logger.DebugCF("agent", "System prompt preview",
 		map[string]any{
 			"preview": preview,
diff --git a/pkg/utils/string.go b/pkg/utils/string.go
index 02f346db4..dbaafdb7f 100644
--- a/pkg/utils/string.go
+++ b/pkg/utils/string.go
@@ -2,9 +2,18 @@ package utils
 
 import (
 	"strings"
+	"sync/atomic"
 	"unicode"
 )
 
+// Global variable to disable truncation
+var disableTruncation atomic.Bool
+
+// SetDisableTruncation globally enables or disables string truncation
+func SetDisableTruncation(enabled bool) {
+	disableTruncation.Store(enabled)
+}
+
 // SanitizeMessageContent removes Unicode control characters, format characters (RTL overrides,
 // zero-width characters), and other non-graphic characters that could confuse an LLM
 // or cause display issues in the agent UI.
@@ -30,6 +39,10 @@ func SanitizeMessageContent(input string) string {
 // Handles multi-byte Unicode characters properly.
 // If the string is truncated, "..." is appended to indicate truncation.
 func Truncate(s string, maxLen int) string {
+	// If the no-truncate flag is active, it returns the full string
+	if disableTruncation.Load() {
+		return s
+	}
 	if maxLen <= 0 {
 		return ""
 	}