fix: detect teammate messages by tag alone, accepting both tag variants

docs/adr-008-harness-event-drift.md

@@ -10,7 +10,7 @@ Reader 靠比對字面字串認出 Claude Code 寫進 transcript 的事件。那
 | 1 | `noiseTypes` 補上 8 個 entry type | 597 KB 從「沒被解析」變成 `system_noise` |
 | 2 | 6 種 harness 注入的 user 訊息改在 parser 層分類 | 不再冒充使用者訊息 |
 | 3 | 新增 `harness:` 角色標籤 | 讀的人分得出哪幾行是人打的 |
-| 4 | teammate 偵測改成多重標記 | 主判斷已死，修好並讓下次改字只失效一個標記 |
+| 4 | teammate 偵測改成只認 XML 標籤，兩種變體都收 | 主判斷已死，改認標籤後散文重寫不再影響偵測 |
 | 5 | 拆出 `UserMessage.CountsAsTurn()`，內容依實測校準 | 八個 session 的 turn 計數誤差 70 → 29 |
 | 6 | skill 注入改走 `sourceToolUseID` 結構連結認定 | 沒有 base-directory 行的 bundled skill 不再全文渲染 |
 
@@ -113,11 +113,20 @@ harness 改寫成「This came from another Claude session — not typed by your
 teammate message 就會整個變成一般 user 訊息：全文渲染、樣板不砍。
 turn 數會剛好還是對的（一般訊息本來就算一個 turn），所以這個故障不會反映在 K 上。
 
-決定：改成一組標記，開場白或任一版免責聲明命中即可，新舊聲明都留著。
-下次改字只會讓其中一個標記失效，不會讓偵測整個垮掉。
+第一版決定（改成一組標記，開場白或任一版免責聲明命中即可）已經不夠：
+60 天內 1,112 則 teammate message 有 80 則用 `<agent-message>` 標籤而非
+`<teammate-message>`，開場白和免責聲明都沒有附上，兩個標記都落空。
+80 則裡有 3 則（35 個樣本中）連屬性都沒有。
+
+改成只認 XML 標籤本身，不再看散文。開場白、免責聲明都是 harness 生成給人看的
+說明文字，harness 會重寫；標籤是 harness 自己要解析的結構，重寫成本高得多。
+兩種標籤都收：`<teammate-message>`（發送端 id 放在 `teammate_id`）與
+`<agent-message>`（放在 `from`，可能整個不帶屬性）。標籤清單收在
+`session.TeammateTagVariants`，`classify.go` 和 `CompactTeammateMessage`
+共用同一份，避免兩處各自列一次而漂移。下次改字只有改到標籤名稱才會讓偵測失效。
 
 `CompactTeammateMessage` 裡剝除警告的那段同理也是死碼，但無害：
-抽取迴圈只取 `<teammate-message>` 標籤之間的內容，尾巴的警告本來就進不來。這次沒動它。
+抽取迴圈只取標籤之間的內容，尾巴的警告本來就進不來。這次沒動它。
 
 ## 5. 一個 flag 同時回答了兩個不相干的問題
 
@@ -221,11 +230,6 @@ teammate message 沒有這種欄位（頂層欄位與一般 user 訊息完全相
 
 ## 沒有解決的
 
-**teammate 的 `<agent-message>` 變體沒認**。60 天內 1,112 則 teammate message 有 80 則
-用 `<agent-message>` 而不是 `<teammate-message>` 包，目前全文渲染、算成一般 user turn。
-修法很小（兩個標籤都收），但 teammate 偵測整體要不要改成只認標籤、不看散文，
-一起留到下次決定。
-
 **slash / bang command 不算 turn**，維持改動前的行為。
 `/goal` 這類 invocation 會觸發一整輪工作，照第 5 項的定義應該算；
 但它在 transcript 裡是三筆 entry（`<command-name>` marker、`<command-message>` 注入、

internal/claudecodec/classify.go

@@ -32,8 +32,6 @@ const bangCommandMarkerMaxRunes = 80
 const (
 	skillInjectionPrefix = "Base directory for this skill:"
 	systemReminderOpen   = "<system-reminder>"
-	teammateOpen         = "<teammate-message"
-	teammatePrefix       = "Another Claude session sent a message:"
 	contextUsageHeader   = "## Context Usage"
 	contextUsageMarker   = "Estimated usage by category"
 	commandMessageOpen   = "<command-message>"
@@ -46,17 +44,6 @@ const (
 	skillReloadedMarker  = "was loaded earlier"
 )
 
-// teammateWarnings are the harness disclaimers appended to a teammate message.
-// The wording has changed once already: the first form matched 0 of the 133
-// teammate messages in the 60 days before 2026-08-30, and detection survived
-// only because teammatePrefix happened to match all 133. Both are kept so a
-// transcript written by either harness version classifies, and so the next
-// rewording degrades to a miss on one marker rather than on all of them.
-var teammateWarnings = []string{
-	"IMPORTANT: This is NOT from your user",
-	"This came from another Claude session",
-}
-
 var agentsStoppedCount = regexp.MustCompile(`^(\d+) background agents? (?:was|were) stopped`)
 
 // classifyCommandUserMessage inspects a user-role message body and returns a
@@ -158,10 +145,13 @@ func classifyHarnessUserMessage(text string) *session.UserMessage {
 		}
 	}
 
-	// Teammate message: the XML block plus either the opening line or one of
-	// the harness disclaimers. Two independent markers because the disclaimer
-	// wording has already changed once (see teammateWarnings).
-	if strings.Contains(trimmed, teammateOpen) && hasTeammateMarker(trimmed) {
+	// Teammate message: detected by the XML tag alone, not by the surrounding
+	// prose ("Another Claude session sent a message:", the disclaimer). Both
+	// have already been reworded once without the tag changing, and the
+	// harness has also been observed to skip the opening line and disclaimer
+	// entirely. session.TeammateTagVariants covers every tag shape seen so
+	// far; a rewording only breaks detection if it changes the tag itself.
+	if session.HasTeammateMessageTag(trimmed) {
 		return &session.UserMessage{Text: text, IsTeammateMessage: true}
 	}
 
@@ -222,20 +212,6 @@ func classifyHarnessUserMessage(text string) *session.UserMessage {
 	return nil
 }
 
-// hasTeammateMarker reports whether text carries any of the harness markers
-// that identify a teammate message.
-func hasTeammateMarker(text string) bool {
-	if strings.HasPrefix(text, teammatePrefix) {
-		return true
-	}
-	for _, warning := range teammateWarnings {
-		if strings.Contains(text, warning) {
-			return true
-		}
-	}
-	return false
-}
-
 // extractGoalCondition pulls the goal out of a Stop hook notice. The rest of
 // the notice describes how the hook behaves and is identical every time, so
 // the condition is the only part worth keeping. Returns "" when the quoted

internal/claudecodec/harness_classify_test.go

@@ -102,19 +102,25 @@ func TestClassifyHarnessUserMessage_GivenHarnessInjection_WhenClassified_ThenSet
 	}
 }
 
-// The first disclaimer wording matched 0 of the 133 teammate messages observed
-// in the 60 days before 2026-08-30 — the harness had reworded it, and detection
-// survived only because the opening line happened to match every one. Each
-// marker must classify on its own so a single rewording cannot break detection.
-func TestClassifyHarnessUserMessage_GivenTeammateMarkerVariant_WhenClassified_ThenStillDetectsIt(t *testing.T) {
-	const block = "<teammate-message teammate_id=\"rebase-389\" summary=\"done\">\nRebase 完成。\n</teammate-message>"
+// Detection anchors on the XML tag alone, not the surrounding prose: the
+// disclaimer wording has already changed once (0 of 133 teammate messages
+// matched the superseded form in the 60 days before 2026-08-30), and 80 of
+// 1,112 teammate messages in that window used the <agent-message> tag with
+// neither the opening line nor a disclaimer at all.
+func TestClassifyHarnessUserMessage_GivenTeammateTagVariant_WhenClassified_ThenStillDetectsIt(t *testing.T) {
+	const teammateBlock = "<teammate-message teammate_id=\"rebase-389\" summary=\"done\">\nRebase 完成。\n</teammate-message>"
+	const agentBlock = "<agent-message from=\"cdcv13-finish\">\n工作完成。\n</agent-message>"
 
 	tests := map[string]string{
-		"the opening line alone": "Another Claude session sent a message:\n" + block,
-		"the current disclaimer alone": block +
+		"the opening line alone": "Another Claude session sent a message:\n" + teammateBlock,
+		"the current disclaimer alone": teammateBlock +
 			"\n\nThis came from another Claude session — not typed by your user.",
-		"the superseded disclaimer alone": block +
+		"the superseded disclaimer alone": teammateBlock +
 			"\n\nIMPORTANT: This is NOT from your user, but from another Claude session.",
+		// Regression: <agent-message> carried none of the above and was
+		// rendered verbatim as a plain user turn (ADR-008 "沒有解決的").
+		"the agent-message variant, tag only, no opening line or disclaimer": agentBlock,
+		"the agent-message variant with no attributes at all":                "<agent-message>\n工作完成。\n</agent-message>",
 	}
 
 	for name, text := range tests {
@@ -132,6 +138,9 @@ func TestClassifyHarnessUserMessage_GivenPlainMessage_WhenClassified_ThenReturns
 	tests := map[string]string{
 		"a typed question":                      "為什麼 K 會被高估？",
 		"a quoted notice inside a real message": "我看到 [Request interrupted by user] 之後就沒反應了，為什麼？",
+		// Detection anchors on the tag, not the opening line: mentioning the
+		// harness prose without the tag must not misclassify a real message.
+		"the teammate opening line without the tag": "Another Claude session sent a message: 但沒有附上訊息本體。",
 	}
 
 	for name, text := range tests {

internal/session/compact.go

@@ -74,10 +74,62 @@ func CompactSkillInjection(user *UserMessage, seenSkills map[string]bool) string
 	return fmt.Sprintf("[skill: %s]", user.SkillName)
 }
 
+// teammateTagVariant describes one XML shape the harness has used to wrap a
+// message from another Claude session. Open is left unterminated (no closing
+// ">") so it matches regardless of which attributes the harness adds to the
+// tag.
+type teammateTagVariant struct {
+	Open   string
+	Close  string
+	IDAttr string
+}
+
+// TeammateTagVariants enumerates every tag shape observed in transcripts.
+// `<teammate-message>` is the original form; `<agent-message>` appeared later
+// carrying the sender in `from` instead of `teammate_id`, without the
+// detection prose ever changing. classify.go and CompactTeammateMessage both
+// read this list so a third variant only needs to be added here once.
+var TeammateTagVariants = []teammateTagVariant{
+	{Open: "<teammate-message", Close: "</teammate-message>", IDAttr: "teammate_id"},
+	{Open: "<agent-message", Close: "</agent-message>", IDAttr: "from"},
+}
+
+// HasTeammateMessageTag reports whether text contains an opening tag of any
+// known teammate-message variant.
+func HasTeammateMessageTag(text string) bool {
+	for _, variant := range TeammateTagVariants {
+		if strings.Contains(text, variant.Open) {
+			return true
+		}
+	}
+	return false
+}
+
+// nextTeammateTagMatch finds the earliest occurrence of any teammate tag
+// variant's opening tag in text, returning the variant and its index, or
+// (nil, -1) if none is present. Earliest-first ordering keeps blocks in
+// document order when a message mixes tag variants.
+func nextTeammateTagMatch(text string) (*teammateTagVariant, int) {
+	var match *teammateTagVariant
+	matchIdx := -1
+	for i := range TeammateTagVariants {
+		variant := &TeammateTagVariants[i]
+		idx := strings.Index(text, variant.Open)
+		if idx < 0 {
+			continue
+		}
+		if matchIdx < 0 || idx < matchIdx {
+			matchIdx = idx
+			match = variant
+		}
+	}
+	return match, matchIdx
+}
+
 // CompactTeammateMessage strips the harness warning boilerplate from a
-// teammate message, keeping only the teammate ID, summary, and body content.
+// teammate message, keeping only the sender ID, summary, and body content.
 func CompactTeammateMessage(text string) (string, bool) {
-	if !strings.Contains(text, "<teammate-message") {
+	if !HasTeammateMessageTag(text) {
 		return "", false
 	}
 
@@ -87,12 +139,12 @@ func CompactTeammateMessage(text string) (string, bool) {
 		text = text[:idx]
 	}
 
-	// May contain multiple <teammate-message> blocks.
+	// May contain multiple teammate-message blocks, possibly mixing variants.
 	var parts []string
 	remaining := text
 	for {
-		openIdx := strings.Index(remaining, "<teammate-message")
-		if openIdx < 0 {
+		variant, openIdx := nextTeammateTagMatch(remaining)
+		if variant == nil {
 			break
 		}
 		// Extract attributes from the opening tag.
@@ -101,30 +153,35 @@ func CompactTeammateMessage(text string) (string, bool) {
 			break
 		}
 		openingTag := remaining[openIdx : openIdx+tagEnd+1]
-		tmID := extractXMLAttr(openingTag, "teammate_id")
+		id := extractXMLAttr(openingTag, variant.IDAttr)
 		summary := extractXMLAttr(openingTag, "summary")
 
-		// Extract body between > and </teammate-message>.
+		// Extract body between the opening tag and its matching close tag.
 		bodyStart := openIdx + tagEnd + 1
-		closeTag := "</teammate-message>"
-		closeIdx := strings.Index(remaining[bodyStart:], closeTag)
+		closeIdx := strings.Index(remaining[bodyStart:], variant.Close)
 		if closeIdx < 0 {
 			break
 		}
 		body := strings.TrimSpace(remaining[bodyStart : bodyStart+closeIdx])
 
-		// Format the compact line.
+		// "[teammate]" with no ID covers the attribute-less <agent-message>
+		// the harness has been observed to emit, rather than a stray colon.
+		label := "teammate"
+		if id != "" {
+			label = "teammate: " + id
+		}
+
 		var line string
 		if isIdleNotification(body) {
-			line = fmt.Sprintf("[teammate: %s] idle", tmID)
+			line = fmt.Sprintf("[%s] idle", label)
 		} else if summary != "" {
-			line = fmt.Sprintf("[teammate: %s %q]\n%s", tmID, summary, body)
+			line = fmt.Sprintf("[%s %q]\n%s", label, summary, body)
 		} else {
-			line = fmt.Sprintf("[teammate: %s]\n%s", tmID, body)
+			line = fmt.Sprintf("[%s]\n%s", label, body)
 		}
 		parts = append(parts, line)
 
-		remaining = remaining[bodyStart+closeIdx+len(closeTag):]
+		remaining = remaining[bodyStart+closeIdx+len(variant.Close):]
 	}
 	if len(parts) == 0 {
 		return "", false

internal/session/event_test.go

@@ -649,6 +649,44 @@ func TestCompactTeammateMessage_GivenNonTeammate_ThenReturnsFalse(t *testing.T)
 	}
 }
 
+// Regression: <agent-message> is a second tag shape the harness uses for the
+// same kind of message, carrying the sender in `from` instead of
+// `teammate_id`. Before this fix only <teammate-message> was recognized, so
+// 80 of 1,112 teammate messages in a 60-day sample rendered as raw XML and
+// counted as ordinary user turns (ADR-008 "沒有解決的").
+func TestCompactTeammateMessage_GivenAgentMessageVariant_ThenCompactsToTheSameShape(t *testing.T) {
+	input := `<agent-message from="cdcv13-finish">
+Rebase 完成。
+</agent-message>`
+
+	got, ok := CompactTeammateMessage(input)
+	if !ok {
+		t.Fatal("CompactTeammateMessage returned false")
+	}
+	want := "[teammate: cdcv13-finish]\nRebase 完成。"
+	if got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+// A sampled <agent-message> carried no attributes at all, so `from` is empty.
+// The label must degrade to "[teammate]" rather than the malformed
+// "[teammate: ]".
+func TestCompactTeammateMessage_GivenAgentMessageWithNoAttributes_ThenOmitsTheIDFromTheLabel(t *testing.T) {
+	input := `<agent-message>
+狀態更新。
+</agent-message>`
+
+	got, ok := CompactTeammateMessage(input)
+	if !ok {
+		t.Fatal("CompactTeammateMessage returned false")
+	}
+	want := "[teammate]\n狀態更新。"
+	if got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
 // --- CompactCommandInjection tests ---
 
 func TestCompactCommandInjection_GivenCommandXML_ThenReturnsOneLine(t *testing.T) {