diff --git a/internal/server/work_checkpoint_eval_budget_test.go b/internal/server/work_checkpoint_eval_budget_test.go
index 5bc35f9..393f60d 100644
--- a/internal/server/work_checkpoint_eval_budget_test.go
+++ b/internal/server/work_checkpoint_eval_budget_test.go
@@ -249,29 +249,32 @@ func TestEvaluationStopsAfterMalformedToolTerminal(t *testing.T) {
 
 func TestEvaluationTransportObservationSanitized(t *testing.T) {
 	const maxTail, maxBytes = 10000, int64(32*1024*1024 + 1)
+	const maxFragments, maxArgumentBytes = 10000, 4*1024*1024 + 1
 	for _, tc := range []struct {
-		name       string
-		input      agentllm.TerminalObservation
-		wantTail   int
-		wantBytes  int64
-		wantKind   string
-		wantFields [3]string
+		name          string
+		input         agentllm.TerminalObservation
+		wantTail      int
+		wantBytes     int64
+		wantFragments int
+		wantArgBytes  int
+		wantKind      string
+		wantFields    [3]string
 	}{
 		{"negative-tail-oversized-body", agentllm.TerminalObservation{ReadOutcome: "done_marker",
-			TailEventKind: "PRIVATE_TAIL_R06", TailEventCount: -5,
+			TailEventKind: "PRIVATE_TAIL_R06", TailEventCount: -5, ToolFragments: -3, ToolArgumentBytes: 1 << 30,
 			BodyBoundary: &agentllm.BodyBoundaryObservation{ProtocolClass: "PRIVATE_HEADER_R06", FramingClass: "PRIVATE_FRAMING_R06",
 				LengthRelation: "PRIVATE_LENGTH_R06", BytesRead: 1 << 40, DeclaredLengthKnown: true, BytesSaturated: true, EOFSeen: true, Uncompressed: true}},
-			0, maxBytes, "unknown", [3]string{"other", "unknown", "unknown"}},
+			0, maxBytes, 0, maxArgumentBytes, "unknown", [3]string{"other", "unknown", "unknown"}},
 		{"oversized-tail-negative-body", agentllm.TerminalObservation{ReadOutcome: "done_marker",
-			TailEventKind: "PRIVATE_TAIL_R06", TailEventCount: 1 << 20,
+			TailEventKind: "PRIVATE_TAIL_R06", TailEventCount: 1 << 20, ToolFragments: 1 << 20, ToolArgumentBytes: -9,
 			BodyBoundary: &agentllm.BodyBoundaryObservation{ProtocolClass: "PRIVATE_HEADER_R06", FramingClass: "PRIVATE_FRAMING_R06",
 				LengthRelation: "PRIVATE_LENGTH_R06", BytesRead: -7, DeclaredLengthKnown: true, BytesSaturated: true, EOFSeen: true, Uncompressed: true}},
-			maxTail, 0, "unknown", [3]string{"other", "unknown", "unknown"}},
+			maxTail, 0, maxFragments, 0, "unknown", [3]string{"other", "unknown", "unknown"}},
 		{"known-values-kept", agentllm.TerminalObservation{ReadOutcome: "done_marker",
-			TailEventKind: "comment", TailEventCount: 3,
+			TailEventKind: "comment", TailEventCount: 3, ToolFragments: 2, ToolArgumentBytes: 64,
 			BodyBoundary: &agentllm.BodyBoundaryObservation{ProtocolClass: "http2", FramingClass: "chunked",
 				LengthRelation: "match", BytesRead: 128, DeclaredLengthKnown: true, BytesSaturated: true, EOFSeen: true, Uncompressed: true}},
-			3, 128, "comment", [3]string{"http2", "chunked", "match"}},
+			3, 128, 2, 64, "comment", [3]string{"http2", "chunked", "match"}},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			input := tc.input
@@ -283,6 +286,7 @@ func TestEvaluationTransportObservationSanitized(t *testing.T) {
 			}
 			body := clean.BodyBoundary
 			if clean.ReadOutcome != "done_marker" || clean.TailEventKind != tc.wantKind || clean.TailEventCount != tc.wantTail ||
+				clean.ToolFragments != tc.wantFragments || clean.ToolArgumentBytes != tc.wantArgBytes ||
 				body.ProtocolClass != tc.wantFields[0] || body.FramingClass != tc.wantFields[1] || body.LengthRelation != tc.wantFields[2] ||
 				body.BytesRead != tc.wantBytes || !body.DeclaredLengthKnown || !body.BytesSaturated || !body.EOFSeen || !body.Uncompressed {
 				t.Fatalf("unbounded observation: %+v body=%+v", clean, body)
@@ -331,7 +335,8 @@ func TestEvaluationTransportObservationSanitized(t *testing.T) {
 				t.Fatalf("sanitized record lost accounting: %s err=%v", raw, err)
 			}
 			got := record.Calls[0].Observation
-			if got.TailEventKind != tc.wantKind || got.TailEventCount != tc.wantTail || got.BodyBoundary.ProtocolClass != tc.wantFields[0] ||
+			if got.TailEventKind != tc.wantKind || got.TailEventCount != tc.wantTail || got.ToolFragments != tc.wantFragments ||
+				got.ToolArgumentBytes != tc.wantArgBytes || got.BodyBoundary.ProtocolClass != tc.wantFields[0] ||
 				got.BodyBoundary.FramingClass != tc.wantFields[1] || got.BodyBoundary.LengthRelation != tc.wantFields[2] ||
 				got.BodyBoundary.BytesRead != tc.wantBytes {
 				t.Fatalf("unbounded persisted observation: %s", raw)
diff --git a/internal/server/work_checkpoint_eval_test.go b/internal/server/work_checkpoint_eval_test.go
index 71bd1c6..6c2b227 100644
--- a/internal/server/work_checkpoint_eval_test.go
+++ b/internal/server/work_checkpoint_eval_test.go
@@ -464,8 +464,10 @@ func evalFinishReasonClass(reason string) string {
 
 // Limits mirror Agent-Native's saturating observation counters.
 const (
-	evalMaxTailEvents = 10000
-	evalMaxBodyBytes  = 32*1024*1024 + 1
+	evalMaxTailEvents        = 10000
+	evalMaxBodyBytes         = 32*1024*1024 + 1
+	evalMaxToolFragments     = 10000
+	evalMaxToolArgumentBytes = 4*1024*1024 + 1
 )
 
 func evalLabel(value, fallback string, allowed ...string) string {
@@ -496,8 +498,8 @@ func evalTerminalObservation(observation *agentllm.TerminalObservation) *agentll
 			"done_marker", "clean_eof", "read_error", "cancelled", "invalid_frame", "provider_error", "transport_error"),
 		LastFrameJSONComplete: observation.LastFrameJSONComplete,
 		UsagePresent:          observation.UsagePresent,
-		ToolFragments:         observation.ToolFragments,
-		ToolArgumentBytes:     observation.ToolArgumentBytes,
+		ToolFragments:         int(clampCount(int64(observation.ToolFragments), evalMaxToolFragments)),
+		ToolArgumentBytes:     int(clampCount(int64(observation.ToolArgumentBytes), evalMaxToolArgumentBytes)),
 		ToolArgumentsValid:    observation.ToolArgumentsValid,
 		TailEventKind: evalLabel(observation.TailEventKind, "unknown",
 			"done_literal", "json_frame", "comment", "empty_data", "partial_frame", "unknown_non_json", "unknown"),