feat(chat): auto-abort agent on exact "stop" keyword during active run

When user sends exact cancel keywords (stop, cancel, abort, thôi, dừng,
hủy, 取消, 停, nevermind) while agent is busy, auto-trigger abort instead
of injecting as follow-up message. Exact match only - "stop now" still
injects normally to avoid false positives.

internal/agent/intent_classify.go

@@ -40,6 +40,23 @@ var cancelKeywords = []string{
 	"nevermind", "never mind",
 }
 
+// exactCancelKeywords is a set of keywords that trigger immediate abort when
+// sent as the entire message (exact match, case-insensitive, trimmed).
+// Used by chat.send to auto-abort when user sends "stop" during an active run.
+var exactCancelKeywords = map[string]bool{
+	"stop": true, "cancel": true, "abort": true,
+	"thôi": true, "dừng": true, "hủy": true,
+	"取消": true, "停": true,
+	"nevermind": true, "never mind": true,
+}
+
+// IsExactCancelKeyword returns true if the message is an exact cancel keyword
+// (case-insensitive, whitespace-trimmed). Used by chat.send to auto-abort
+// running agent loops when user explicitly sends a stop command.
+func IsExactCancelKeyword(msg string) bool {
+	return exactCancelKeywords[strings.ToLower(strings.TrimSpace(msg))]
+}
+
 // quickClassify attempts keyword-based classification for ultra-short messages
 // before calling the LLM. Only messages ≤ 15 runes are fast-pathed; longer
 // messages always go to LLM for proper context understanding.

internal/agent/intent_classify_test.go

@@ -227,3 +227,59 @@ func TestFormatStatusReply_WithStatus(t *testing.T) {
 		t.Error("expected non-empty reply with status")
 	}
 }
+
+// ─── IsExactCancelKeyword ─────────────────────────────────────────────────
+
+func TestIsExactCancelKeyword_ExactMatches(t *testing.T) {
+	cases := []string{"stop", "cancel", "abort", "thôi", "dừng", "hủy", "取消", "停", "nevermind", "never mind"}
+	for _, kw := range cases {
+		t.Run(kw, func(t *testing.T) {
+			if !IsExactCancelKeyword(kw) {
+				t.Errorf("%q should be recognized as cancel keyword", kw)
+			}
+		})
+	}
+}
+
+func TestIsExactCancelKeyword_CaseInsensitive(t *testing.T) {
+	cases := []string{"STOP", "Stop", "CANCEL", "Cancel", "ABORT", "Abort"}
+	for _, kw := range cases {
+		t.Run(kw, func(t *testing.T) {
+			if !IsExactCancelKeyword(kw) {
+				t.Errorf("%q should be recognized (case-insensitive)", kw)
+			}
+		})
+	}
+}
+
+func TestIsExactCancelKeyword_WithWhitespace(t *testing.T) {
+	cases := []string{"  stop  ", "\tstop\n", " cancel "}
+	for _, kw := range cases {
+		t.Run(kw, func(t *testing.T) {
+			if !IsExactCancelKeyword(kw) {
+				t.Errorf("%q should be recognized after trimming", kw)
+			}
+		})
+	}
+}
+
+func TestIsExactCancelKeyword_NonMatches(t *testing.T) {
+	cases := []string{
+		"stop now",           // not exact
+		"please stop",        // not exact
+		"nonstop",            // embedded
+		"stop it",            // not exact
+		"cancel the order",   // not exact
+		"don't stop",         // not exact
+		"",                   // empty
+		"hello",              // unrelated
+		"làm đơn giản thôi",  // contains "thôi" but not exact
+	}
+	for _, msg := range cases {
+		t.Run(msg, func(t *testing.T) {
+			if IsExactCancelKeyword(msg) {
+				t.Errorf("%q should NOT be recognized as cancel keyword", msg)
+			}
+		})
+	}
+}

internal/gateway/methods/chat.go

@@ -195,6 +195,23 @@ func (m *ChatMethods) handleSend(ctx context.Context, client *gateway.Client, re
 	// Mid-run injection: if session already has an active run, inject the message
 	// into the running loop instead of starting a new concurrent run.
 	if m.agents.IsSessionBusy(sessionKey) {
+		// Exact cancel keyword detection: auto-abort when user sends "stop", "cancel", etc.
+		if agent.IsExactCancelKeyword(params.Message) {
+			results := m.agents.AbortRunsForSession(sessionKey)
+			aborted := false
+			for _, r := range results {
+				if r.Stopped || r.Forced {
+					aborted = true
+					break
+				}
+			}
+			client.SendResponse(protocol.NewOKResponse(req.ID, map[string]any{
+				"cancelled": true,
+				"aborted":   aborted,
+			}))
+			return
+		}
+
 		injected := m.agents.InjectMessage(sessionKey, agent.InjectedMessage{
 			Content: params.Message,
 			UserID:  userID,