From 735187c86cadeb3c195ebf48fbdaa86d10e882a2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=8E=8B=E5=9B=BD=E6=A0=8B0668001083?=
 <wang.guodong2@xydigit.com>
Date: Mon, 20 Apr 2026 17:22:04 +0800
Subject: [PATCH 1/2] fix(gateway): include tail logs on abnormal exit

When the managed gateway process exits with an error, append the last buffered stdout/stderr lines to the exit log to make root causes visible.

Closes #2513
---
 web/backend/api/gateway.go |  7 ++++++-
 web/backend/api/log.go     | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/web/backend/api/gateway.go b/web/backend/api/gateway.go
index 201000ff3..90a31b2ff 100644
--- a/web/backend/api/gateway.go
+++ b/web/backend/api/gateway.go
@@ -762,7 +762,12 @@ func (h *Handler) startGatewayLocked(initialStatus string, existingPid int) (int
 	// Wait for exit in background and clean up
 	go func() {
 		if err := cmd.Wait(); err != nil {
-			logger.ErrorC("gateway", fmt.Sprintf("Gateway process exited: %v", err))
+			tail := gateway.logs.Tail(50)
+			if len(tail) > 0 {
+				logger.ErrorC("gateway", fmt.Sprintf("Gateway process exited: %v\nLast gateway logs:\n%s", err, strings.Join(tail, "\n")))
+			} else {
+				logger.ErrorC("gateway", fmt.Sprintf("Gateway process exited: %v", err))
+			}
 		} else {
 			logger.InfoC("gateway", "Gateway process exited normally")
 		}
diff --git a/web/backend/api/log.go b/web/backend/api/log.go
index f83f6f34c..8ebb60384 100644
--- a/web/backend/api/log.go
+++ b/web/backend/api/log.go
@@ -95,3 +95,35 @@ func (b *LogBuffer) RunID() int {
 
 	return b.runID
 }
+
+// Tail returns up to the last n buffered lines (newest last).
+// If n <= 0, it returns nil.
+func (b *LogBuffer) Tail(n int) []string {
+	if n <= 0 {
+		return nil
+	}
+
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	if b.total == 0 || len(b.lines) == 0 {
+		return nil
+	}
+
+	if n > len(b.lines) {
+		n = len(b.lines)
+	}
+
+	result := make([]string, n)
+
+	if b.total <= b.cap {
+		copy(result, b.lines[len(b.lines)-n:])
+		return result
+	}
+
+	start := (b.total - n) % b.cap
+	for i := 0; i < n; i++ {
+		result[i] = b.lines[(start+i)%b.cap]
+	}
+	return result
+}

From 1c953db972b183298de7429157e08613ee22af72 Mon Sep 17 00:00:00 2001
From: Yum-King <wang.guodong2@xydigit.com>
Date: Mon, 20 Apr 2026 20:44:41 +0800
Subject: [PATCH 2/2] chore(lint): wrap gateway exit log line

---
 web/backend/api/gateway.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/web/backend/api/gateway.go b/web/backend/api/gateway.go
index 90a31b2ff..c7d695824 100644
--- a/web/backend/api/gateway.go
+++ b/web/backend/api/gateway.go
@@ -764,7 +764,14 @@ func (h *Handler) startGatewayLocked(initialStatus string, existingPid int) (int
 		if err := cmd.Wait(); err != nil {
 			tail := gateway.logs.Tail(50)
 			if len(tail) > 0 {
-				logger.ErrorC("gateway", fmt.Sprintf("Gateway process exited: %v\nLast gateway logs:\n%s", err, strings.Join(tail, "\n")))
+				logger.ErrorC(
+					"gateway",
+					fmt.Sprintf(
+						"Gateway process exited: %v\nLast gateway logs:\n%s",
+						err,
+						strings.Join(tail, "\n"),
+					),
+				)
 			} else {
 				logger.ErrorC("gateway", fmt.Sprintf("Gateway process exited: %v", err))
 			}