Record content-free stream terminal observations

Why: The r0.4 trial could prove that the parser missed [DONE] but could not distinguish clean EOF, malformed frames, read failure, or provider error without retaining raw SSE.

Evidence: RED receipts fast-slow-u3-r05-task1-terminal-red.json and task1-http-error-red.json; GREEN targeted receipt and full vet/test/race receipt fast-slow-u3-r05-task1-agent-native-full.json.

Impact: Add bounded scalar diagnostics and successful HTTP status to terminal events while preserving the existing incomplete-tool rejection, returned Usage, and retry behavior.

Refs: U3 r0.5 approved design and plan; Agent-Native PR #46

runtime/llm/client.go

@@ -100,10 +100,10 @@ func (c *Client) run(ctx context.Context, model string, messages []Message, tool
 	resp, err := hc.Do(req)
 	if err != nil {
 		if ctx.Err() != nil {
-			emitAbort(out, "", ctx.Err())
+			emitAbort(out, "", ctx.Err(), &TerminalObservation{ReadOutcome: "cancelled"})
 			return
 		}
-		emitError(out, "", true, err.Error())
+		emitError(out, "", true, err.Error(), &TerminalObservation{ReadOutcome: "transport_error"})
 		return
 	}
 	defer resp.Body.Close()
@@ -111,12 +111,13 @@ func (c *Client) run(ctx context.Context, model string, messages []Message, tool
 		slurp, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
 		msg := fmt.Sprintf("provider status %d: %s", resp.StatusCode, strings.TrimSpace(string(slurp)))
 		ev := Event{
-			Kind:         KindError,
-			HTTPStatus:   resp.StatusCode,
-			Retryable:    StatusRetryable(resp.StatusCode) && !ContextOverflow(msg),
-			ErrorMessage: msg,
-			Err:          &StreamError{Message: msg, Retryable: StatusRetryable(resp.StatusCode) && !ContextOverflow(msg)},
-			Message:      Message{Role: RoleAssistant, StopReason: StopError},
+			Kind:                KindError,
+			HTTPStatus:          resp.StatusCode,
+			TerminalObservation: &TerminalObservation{ReadOutcome: "provider_error"},
+			Retryable:           StatusRetryable(resp.StatusCode) && !ContextOverflow(msg),
+			ErrorMessage:        msg,
+			Err:                 &StreamError{Message: msg, Retryable: StatusRetryable(resp.StatusCode) && !ContextOverflow(msg)},
+			Message:             Message{Role: RoleAssistant, StopReason: StopError},
 		}
 		if d, ok := ParseRetryAfter(resp.Header.Get("Retry-After"), time.Now()); ok {
 			ev.HasRetryAfter = true
@@ -126,6 +127,9 @@ func (c *Client) run(ctx context.Context, model string, messages []Message, tool
 		return
 	}
 	for ev := range ParseSSE(ctx, resp.Body) {
+		if ev.Kind == KindMessageEnd || ev.Kind == KindError {
+			ev.HTTPStatus = resp.StatusCode
+		}
 		out <- ev
 	}
 }

runtime/llm/client_test.go

@@ -0,0 +1,65 @@
+package llm
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+type terminalRoundTripFunc func(*http.Request) (*http.Response, error)
+
+func (f terminalRoundTripFunc) RoundTrip(r *http.Request) (*http.Response, error) { return f(r) }
+
+func TestClientTerminalObservationHTTPStatus(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/chat/completions" {
+			t.Errorf("path = %q", r.URL.Path)
+		}
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = w.Write([]byte("data: {\"choices\":[{\"delta\":{\"content\":\"ok\"},\"finish_reason\":\"stop\"}],\"usage\":{\"prompt_tokens\":2,\"completion_tokens\":1,\"total_tokens\":3}}\n\ndata: [DONE]\n\n"))
+	}))
+	defer server.Close()
+	client := &Client{BaseURL: server.URL, APIKey: "fixture", HTTPClient: server.Client()}
+	var end Event
+	for ev := range client.Stream(context.Background(), "fixture", []Message{{Role: RoleUser, Content: "hello"}}, nil, StreamOptions{}) {
+		if ev.Kind == KindMessageEnd {
+			end = ev
+		}
+	}
+	if end.HTTPStatus != http.StatusOK || end.TerminalObservation == nil ||
+		end.TerminalObservation.ReadOutcome != "done_marker" || !end.StreamComplete || end.Usage.TotalTokens != 3 {
+		t.Fatalf("successful HTTP terminal lost transport evidence: %#v", end)
+	}
+}
+
+func TestClientTerminalObservationProviderAndTransportFailure(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "PRIVATE_PROVIDER_BODY_R05", http.StatusTooManyRequests)
+	}))
+	defer server.Close()
+	tests := []struct {
+		name    string
+		client  *Client
+		status  int
+		outcome string
+	}{
+		{"provider-http", &Client{BaseURL: server.URL, APIKey: "fixture", HTTPClient: server.Client()}, http.StatusTooManyRequests, "provider_error"},
+		{"transport", &Client{BaseURL: "http://test.invalid", APIKey: "fixture", HTTPClient: &http.Client{Transport: terminalRoundTripFunc(func(*http.Request) (*http.Response, error) {
+			return nil, errors.New("PRIVATE_TRANSPORT_ERROR_R05")
+		})}}, 0, "transport_error"},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			var end Event
+			for ev := range tc.client.Stream(context.Background(), "fixture", []Message{{Role: RoleUser, Content: "hello"}}, nil, StreamOptions{}) {
+				end = ev
+			}
+			if end.Kind != KindError || end.HTTPStatus != tc.status || end.TerminalObservation == nil ||
+				end.TerminalObservation.ReadOutcome != tc.outcome {
+				t.Fatalf("provider/transport failure was not classified: %#v", end)
+			}
+		})
+	}
+}

runtime/llm/sse.go

@@ -39,6 +39,11 @@ type usageWire struct {
 	} `json:"prompt_tokens_details"`
 }
 
+const (
+	maxObservedToolFragments     = 10000
+	maxObservedToolArgumentBytes = 4*1024*1024 + 1
+)
+
 // ParseSSE reads an OpenAI-compatible server-sent event body and emits
 // deltas plus one terminal message_end or error event.
 func ParseSSE(ctx context.Context, r io.Reader) <-chan Event {
@@ -59,15 +64,36 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 	finished := ""
 	sawDone := false
 	sawUsage := false
+	readOutcome := "clean_eof"
+	lastFrameJSONComplete := false
+	toolFragments := 0
+	toolArgumentBytes := 0
+	observation := func() *TerminalObservation {
+		argumentsValid := len(order) > 0
+		for _, idx := range order {
+			var args map[string]json.RawMessage
+			if err := json.Unmarshal([]byte(calls[idx].Arguments), &args); err != nil || args == nil {
+				argumentsValid = false
+				break
+			}
+		}
+		return &TerminalObservation{
+			ReadOutcome: readOutcome, LastFrameJSONComplete: lastFrameJSONComplete,
+			UsagePresent: sawUsage, ToolFragments: toolFragments,
+			ToolArgumentBytes: toolArgumentBytes, ToolArgumentsValid: argumentsValid,
+		}
+	}
 	sendTerminalFailure := func(why string) {
 		message := Message{Role: RoleAssistant, Content: content.String(), StopReason: StopError}
 		if reasoning.Len() > 0 {
 			message.Thinking = []ThinkingBlock{{Thinking: reasoning.String()}}
 		}
 		failed := terminalStreamFailure(message, usage, finished, sawDone, why)
+		failed.TerminalObservation = observation()
 		select {
 		case <-ctx.Done():
-			emitAbort(out, content.String(), ctx.Err())
+			readOutcome = "cancelled"
+			emitAbort(out, content.String(), ctx.Err(), observation())
 		case out <- failed:
 		}
 	}
@@ -80,30 +106,36 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 			break
 		}
 		if ctx.Err() != nil {
-			emitAbort(out, content.String(), ctx.Err())
+			readOutcome = "cancelled"
+			emitAbort(out, content.String(), ctx.Err(), observation())
 			return
 		}
 		if data == "[DONE]" {
 			sawDone = true
+			readOutcome = "done_marker"
 			break
 		}
 		var chunk sseChunk
 		if err := json.Unmarshal([]byte(data), &chunk); err != nil {
+			readOutcome = "invalid_frame"
+			lastFrameJSONComplete = false
 			if sawUsage {
 				sendTerminalFailure("malformed stream chunk after reported usage")
 				return
 			}
-			emitError(out, content.String(), false, "malformed stream chunk: "+err.Error())
+			emitError(out, content.String(), false, "malformed stream chunk: "+err.Error(), observation())
 			return
 		}
+		lastFrameJSONComplete = true
 		if chunk.Error != nil && chunk.Error.Message != "" {
+			readOutcome = "provider_error"
 			msg := chunk.Error.Message
 			if sawUsage {
 				sendTerminalFailure("provider error after reported usage: " + msg)
 				return
 			}
 			retryable := CapacityLimited(msg) && !ContextOverflow(msg)
-			emitError(out, content.String(), retryable, msg)
+			emitError(out, content.String(), retryable, msg, observation())
 			return
 		}
 		if chunk.Usage != nil {
@@ -124,7 +156,8 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 			content.WriteString(choice.Delta.Content)
 			select {
 			case <-ctx.Done():
-				emitAbort(out, content.String(), ctx.Err())
+				readOutcome = "cancelled"
+				emitAbort(out, content.String(), ctx.Err(), observation())
 				return
 			case out <- Event{Kind: KindTextDelta, Text: choice.Delta.Content}:
 			}
@@ -139,12 +172,23 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 			reasoning.WriteString(choice.Delta.Reasoning)
 			select {
 			case <-ctx.Done():
-				emitAbort(out, content.String(), ctx.Err())
+				readOutcome = "cancelled"
+				emitAbort(out, content.String(), ctx.Err(), observation())
 				return
 			case out <- Event{Kind: KindReasoningDelta, ReasoningDelta: choice.Delta.Reasoning}:
 			}
 		}
 		for _, tc := range choice.Delta.ToolCalls {
+			if toolFragments < maxObservedToolFragments {
+				toolFragments++
+			}
+			if n := len(tc.Function.Arguments); n > 0 && toolArgumentBytes < maxObservedToolArgumentBytes {
+				if n > maxObservedToolArgumentBytes-toolArgumentBytes {
+					toolArgumentBytes = maxObservedToolArgumentBytes
+				} else {
+					toolArgumentBytes += n
+				}
+			}
 			cur, ok := calls[tc.Index]
 			if !ok {
 				cur = &ToolCall{}
@@ -162,7 +206,8 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 			}
 			select {
 			case <-ctx.Done():
-				emitAbort(out, content.String(), ctx.Err())
+				readOutcome = "cancelled"
+				emitAbort(out, content.String(), ctx.Err(), observation())
 				return
 			case out <- Event{
 				Kind:           KindToolCallDelta,
@@ -175,21 +220,24 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 		}
 	}
 	if err := sc.Err(); err != nil {
+		readOutcome = "read_error"
 		if ctx.Err() != nil {
-			emitAbort(out, content.String(), ctx.Err())
+			readOutcome = "cancelled"
+			emitAbort(out, content.String(), ctx.Err(), observation())
 			return
 		}
 		if sawUsage {
 			sendTerminalFailure("stream read failed after reported usage")
 			return
 		}
-		emitError(out, content.String(), true, err.Error())
+		emitError(out, content.String(), true, err.Error(), observation())
 		return
 	}
 	// 取消必须压过正常结束。select 在两个分支都就绪时随机挑选，
 	// 竞态下会把 message_end 发给已经取消的调用方。
 	if ctx.Err() != nil {
-		emitAbort(out, content.String(), ctx.Err())
+		readOutcome = "cancelled"
+		emitAbort(out, content.String(), ctx.Err(), observation())
 		return
 	}
 	// A finish reason alone does not prove the tool arguments arrived intact.
@@ -237,8 +285,9 @@ func emitParsed(ctx context.Context, r io.Reader, out chan<- Event) {
 	}
 	select {
 	case <-ctx.Done():
-		emitAbort(out, content.String(), ctx.Err())
-	case out <- Event{Kind: KindMessageEnd, Message: msg, Usage: usage, FinishReason: finished, StreamComplete: sawDone}:
+		readOutcome = "cancelled"
+		emitAbort(out, content.String(), ctx.Err(), observation())
+	case out <- Event{Kind: KindMessageEnd, Message: msg, Usage: usage, FinishReason: finished, StreamComplete: sawDone, TerminalObservation: observation()}:
 	}
 }
 
@@ -337,8 +386,8 @@ func mapFinish(reason string, hasTools bool) StopReason {
 	}
 }
 
-func emitError(out chan<- Event, partial string, retryable bool, message string) {
-	out <- Event{
+func emitError(out chan<- Event, partial string, retryable bool, message string, observed ...*TerminalObservation) {
+	event := Event{
 		Kind:         KindError,
 		Retryable:    retryable,
 		ErrorMessage: message,
@@ -349,14 +398,18 @@ func emitError(out chan<- Event, partial string, retryable bool, message string)
 			StopReason: StopError,
 		},
 	}
+	if len(observed) > 0 {
+		event.TerminalObservation = observed[0]
+	}
+	out <- event
 }
 
-func emitAbort(out chan<- Event, partial string, err error) {
+func emitAbort(out chan<- Event, partial string, err error, observed ...*TerminalObservation) {
 	msg := "aborted"
 	if err != nil {
 		msg = err.Error()
 	}
-	out <- Event{
+	event := Event{
 		Kind:         KindError,
 		Retryable:    false,
 		ErrorMessage: msg,
@@ -367,6 +420,10 @@ func emitAbort(out chan<- Event, partial string, err error) {
 			StopReason: StopAborted,
 		},
 	}
+	if len(observed) > 0 {
+		event.TerminalObservation = observed[0]
+	}
+	out <- event
 }
 
 // StreamError is a provider or transport failure encoded on the event stream.

runtime/llm/sse_test.go

@@ -2,6 +2,7 @@ package llm
 
 import (
 	"context"
+	"encoding/json"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -87,6 +88,10 @@ func TestParseSSEToolCallIncrements(t *testing.T) {
 	if end.Message.StopReason != StopToolCalls || len(end.Message.ToolCalls) != 1 {
 		t.Fatalf("end %#v", end.Message)
 	}
+	if end.TerminalObservation == nil || end.TerminalObservation.ReadOutcome != "done_marker" ||
+		!end.TerminalObservation.ToolArgumentsValid || end.TerminalObservation.ToolFragments != 3 {
+		t.Fatalf("valid multi-fragment terminal was not classified: %#v", end.TerminalObservation)
+	}
 	tc := end.Message.ToolCalls[0]
 	if tc.ID != "call_1" || tc.Name != "read_file" || tc.Arguments != `{"path":"a.md"}` {
 		t.Fatalf("tool call %#v", tc)
@@ -168,6 +173,77 @@ func TestParseSSEToolFinishWithoutDone(t *testing.T) {
 	}
 }
 
+func TestTerminalObservationCleanEOFWithoutDone(t *testing.T) {
+	body := strings.Join([]string{
+		`data: {"choices":[{"delta":{"content":"PRIVATE_PROMPT_R05","tool_calls":[{"index":0,"id":"call_1","function":{"name":"PRIVATE_TOOL_R05","arguments":"{}"}}]}}]}`,
+		`data: {"choices":[{"delta":{},"finish_reason":"tool_calls"}],"usage":{"prompt_tokens":12,"completion_tokens":5,"total_tokens":17}}`,
+		"",
+	}, "\n\n")
+	var end Event
+	for ev := range ParseSSE(context.Background(), strings.NewReader(body)) {
+		if ev.Kind == KindMessageEnd {
+			end = ev
+		}
+	}
+	if end.Err == nil || end.StreamComplete || len(end.Message.ToolCalls) != 0 || end.Usage.TotalTokens != 17 {
+		t.Fatalf("unfinished tool stream was released or unmetered: %#v", end)
+	}
+	meta := end.TerminalObservation
+	if meta == nil || meta.ReadOutcome != "clean_eof" || !meta.LastFrameJSONComplete ||
+		!meta.UsagePresent || meta.ToolFragments != 1 || meta.ToolArgumentBytes != 2 || !meta.ToolArgumentsValid {
+		t.Fatalf("missing content-free clean EOF evidence: %#v", meta)
+	}
+	raw, err := json.Marshal(meta)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Contains(string(raw), "PRIVATE_PROMPT_R05") || strings.Contains(string(raw), "PRIVATE_TOOL_R05") {
+		t.Fatalf("terminal observation retained model content: %s", raw)
+	}
+}
+
+func TestTerminalObservationMalformedAndReadError(t *testing.T) {
+	usageAndTool := `data: {"choices":[{"delta":{"tool_calls":[{"index":0,"id":"call_1","function":{"name":"echo","arguments":"{}"}}]},"finish_reason":"tool_calls"}],"usage":{"prompt_tokens":12,"completion_tokens":5,"total_tokens":17}}` + "\n\n"
+	tests := []struct {
+		name       string
+		ctx        context.Context
+		reader     io.Reader
+		outcome    string
+		usage      int
+		frameValid bool
+	}{
+		{"invalid-frame", context.Background(), strings.NewReader(usageAndTool + "data: {not-json}\n\n"), "invalid_frame", 17, false},
+		{"read-error", context.Background(), &errorAfterDataReader{data: strings.NewReader(usageAndTool)}, "read_error", 17, true},
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	tests = append(tests, struct {
+		name       string
+		ctx        context.Context
+		reader     io.Reader
+		outcome    string
+		usage      int
+		frameValid bool
+	}{"cancelled", ctx, strings.NewReader(usageAndTool), "cancelled", 0, false})
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			var end Event
+			for ev := range ParseSSE(tc.ctx, tc.reader) {
+				if ev.Kind == KindMessageEnd || ev.Kind == KindError {
+					end = ev
+				}
+			}
+			if end.Err == nil || len(end.Message.ToolCalls) != 0 || end.Usage.TotalTokens != tc.usage {
+				t.Fatalf("failure lost Usage or released tools: %#v", end)
+			}
+			meta := end.TerminalObservation
+			if meta == nil || meta.ReadOutcome != tc.outcome || meta.LastFrameJSONComplete != tc.frameValid {
+				t.Fatalf("wrong terminal classification: %#v", meta)
+			}
+		})
+	}
+}
+
 func TestParseSSEInvalidToolArguments(t *testing.T) {
 	body := strings.Join([]string{
 		`data: {"choices":[{"delta":{"tool_calls":[{"index":0,"id":"call_1","function":{"name":"publish_work_checkpoint","arguments":"{\"findings\":"}}]}}]}`,
@@ -186,6 +262,10 @@ func TestParseSSEInvalidToolArguments(t *testing.T) {
 		end.Usage.TotalTokens != 17 {
 		t.Fatalf("unsafe tool call with invalid JSON arguments: %#v", end)
 	}
+	if end.TerminalObservation == nil || end.TerminalObservation.ToolArgumentsValid ||
+		end.TerminalObservation.ReadOutcome != "done_marker" {
+		t.Fatalf("invalid arguments incorrectly classified: %#v", end.TerminalObservation)
+	}
 }
 
 func TestParseSSERejectsMissingToolIdentity(t *testing.T) {

runtime/llm/types.go

@@ -98,6 +98,18 @@ type Usage struct {
 	LastTotalTokens      int `json:"last_total_tokens,omitempty"`
 }
 
+// TerminalObservation records how a stream ended without retaining provider
+// content, tool identity, arguments, request headers, or error text. Counts
+// saturate at fixed limits; this evidence never authorizes a tool call.
+type TerminalObservation struct {
+	ReadOutcome           string `json:"readOutcome"`
+	LastFrameJSONComplete bool   `json:"lastFrameJSONComplete"`
+	UsagePresent          bool   `json:"usagePresent"`
+	ToolFragments         int    `json:"toolFragments"`
+	ToolArgumentBytes     int    `json:"toolArgumentBytes"`
+	ToolArgumentsValid    bool   `json:"toolArgumentsValid"`
+}
+
 // Event is one streamed update. Failures are KindError plus a final assistant
 // message whose StopReason is error or aborted. Stream implementations do not panic.
 type Event struct {
@@ -116,10 +128,13 @@ type Event struct {
 	// StreamComplete records whether the OpenAI-compatible SSE stream supplied
 	// its explicit [DONE] marker. Tool calls require this before execution.
 	StreamComplete bool
-	Err            error
-	Retryable      bool
-	ErrorMessage   string
-	// HTTPStatus 是提供方的 HTTP 状态。0 表示这条错误不是 HTTP 响应。
+	// TerminalObservation is present only on a terminal/error event. It does
+	// not change StreamComplete or the tool-execution safety gate.
+	TerminalObservation *TerminalObservation
+	Err                 error
+	Retryable           bool
+	ErrorMessage        string
+	// HTTPStatus 是提供方的 HTTP 状态；0 表示尚无 HTTP 响应。
 	HTTPStatus int
 	// RetryAfter is the provider's requested wait. HasRetryAfter distinguishes
 	// a real zero from a missing or unparseable header.