truncation: raise hard ceiling to 128KB, include tool name in message

pkg/agent/core.go

@@ -603,7 +603,7 @@ func (s *agent) SetSessionID(newID string) error {
 // actual context window (e.g. CodeWhisperer). 128k tokens is a safe default
 // for modern models.
 const defaultContextLength = 128000
-const defaultToolResultMaxBytes = 8192
+const defaultToolResultMaxBytes = 131072
 
 // autoCompactLimit returns the token threshold for auto-compaction (75%).
 func (s *agent) autoCompactLimit(ctx context.Context) int {

pkg/agent/loop.go

@@ -346,8 +346,8 @@ func run(ctx context.Context, cfg agentConfig, state state) error {
 			if !isErr && cfg.ToolResultMaxBytes > 0 && len(result) > cfg.ToolResultMaxBytes {
 				orig := len(result)
 				result = result[:cfg.ToolResultMaxBytes]
-				result += fmt.Sprintf("\n\n[result truncated: first %d of %d bytes shown; reissue with offset=%d to read more]",
-					cfg.ToolResultMaxBytes, orig, cfg.ToolResultMaxBytes)
+				result += fmt.Sprintf("\n\n[HARD LIMIT: %s output truncated — %d of %d bytes shown. This is a safety ceiling, not a semantic boundary.]",
+					tc.Name, cfg.ToolResultMaxBytes, orig)
 			}
 			if readSafe && !isErr {
 				resultCache.Store(tc.Name+"\x00"+string(tc.Arguments), result)

pkg/agent/loop_truncate_test.go

@@ -37,11 +37,11 @@ func TestTruncation_LargeResultTruncated(t *testing.T) {
 	if !strings.HasPrefix(result, strings.Repeat("x", maxBytes)) {
 		t.Errorf("result does not start with %d x's: %q", maxBytes, result[:min(len(result), 80)])
 	}
-	if !strings.Contains(result, "result truncated") {
+	if !strings.Contains(result, "HARD LIMIT") {
 		t.Errorf("truncation hint missing from result: %q", result)
 	}
-	if !strings.Contains(result, "offset=64") {
-		t.Errorf("offset hint missing from result: %q", result)
+	if !strings.Contains(result, "execute_code") {
+		t.Errorf("tool name missing from truncation hint: %q", result)
 	}
 }
 
@@ -120,7 +120,7 @@ func TestTruncation_ErrorNotTruncated(t *testing.T) {
 	if len(toolEvs) != 1 {
 		t.Fatalf("tool events = %d; want 1", len(toolEvs))
 	}
-	if strings.Contains(toolEvs[0], "result truncated") {
+	if strings.Contains(toolEvs[0], "HARD LIMIT") {
 		t.Errorf("error result was truncated; should be preserved in full")
 	}
 }
@@ -152,7 +152,7 @@ func TestTruncation_CachedResultAlreadyTruncated(t *testing.T) {
 	}
 	// Both should be the truncated form.
 	for i, ev := range toolEvs {
-		if !strings.Contains(ev, "result truncated") {
+		if !strings.Contains(ev, "HARD LIMIT") {
 			t.Errorf("event[%d] missing truncation hint: %q", i, ev[:min(len(ev), 80)])
 		}
 	}