diff --git a/db/exploration.go b/db/exploration.go
index 4e679c5..5b0f79c 100644
--- a/db/exploration.go
+++ b/db/exploration.go
@@ -398,6 +398,23 @@ RETURNING id`, s.expID, a.NodeID, utf8Clean(a.Worker), utf8Clean(a.Kind), utf8Cl
 	return id, err
 }
 
+// ExplorationDiag probes, at the moment of an activity FK violation (23503), why the
+// parent row is unreachable. It reports whether the exploration row still exists, how
+// many task rows reference it (a live task should keep exactly 1 — and RESTRICT on
+// tasks.exploration_id means the exploration CANNOT be deleted while that row lives),
+// and the current MAX(explorations.id). Together these tell apart the failure modes:
+//   - expExists=false, taskRefs=0 → the whole row set is gone (DB reset / wrong DB).
+//   - expExists=false, taskRefs=1 → impossible under RESTRICT; would mean a broken FK.
+//   - expExists=true              → the write's expID is NOT this exploration (stale/
+//     wrong id in the in-memory store); compare against Store.ID().
+func (d *DB) ExplorationDiag(expID int64) (expExists bool, taskRefs int, maxExpID int64, err error) {
+	err = d.QueryRow(`SELECT
+		EXISTS(SELECT 1 FROM explorations WHERE id=$1),
+		(SELECT COUNT(*) FROM tasks WHERE exploration_id=$1),
+		COALESCE((SELECT MAX(id) FROM explorations),0)`, expID).Scan(&expExists, &taskRefs, &maxExpID)
+	return
+}
+
 // TokenTotal sums token usage across ALL workers for this exploration (whole-task
 // total). Same source as TokenStatsByWorker (kind='result' rows), just ungrouped.
 func (s *ExplorationStore) TokenTotal() (TokenUsage, error) {
diff --git a/server/engine.go b/server/engine.go
index c235d48..537853e 100644
--- a/server/engine.go
+++ b/server/engine.go
@@ -2,6 +2,7 @@ package server
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log"
 	"strconv"
@@ -14,8 +15,16 @@ import (
 	"github.com/Autumn-27/artex/intercept"
 	"github.com/Autumn-27/norma/harness"
 	"github.com/Autumn-27/norma/llm"
+	"github.com/jackc/pgx/v5/pgconn"
 )
 
+// isFKViolation reports whether err is a Postgres foreign-key violation (SQLSTATE
+// 23503) — e.g. an activity insert whose exploration_id has no parent row.
+func isFKViolation(err error) bool {
+	var pgErr *pgconn.PgError
+	return errors.As(err, &pgErr) && pgErr.Code == "23503"
+}
+
 // model_error（provider/API 故障：LLM 层瞬时重试耗尽，或流已开始后中途断流）
 // 收场的 work 不是「试过没做完」也不是真失败，而是外部抖动。默认把它当永久
 // blocked 会白丢一条意图，所以这里对该终态额外重跑几次，每次之间退避一下，给
@@ -273,6 +282,19 @@ func (e *Engine) emitActivity(t *Task, r db.Activity) {
 		// trace — a tool_use whose tool_result was lost shows as "执行中" forever.
 		log.Printf("[activity] task %s 重试后仍失败、丢弃该记录 (kind=%s tool=%s tuid=%s): %v",
 			t.ID, r.Kind, r.Tool, r.ToolUseID, err)
+		// On the FK-parent failure (23503) probe the live DB so the next occurrence
+		// records WHY the exploration is unreachable instead of just that it is.
+		if isFKViolation(err) {
+			storeID := t.Store.ID()
+			exists, refs, maxID, dErr := e.m.pg.ExplorationDiag(storeID)
+			if dErr != nil {
+				log.Printf("[activity] task %s FK 诊断查询失败 (store.expID=%d task.ExpID=%d): %v",
+					t.ID, storeID, t.ExpID, dErr)
+			} else {
+				log.Printf("[activity] task %s FK 诊断: store.expID=%d task.ExpID=%d exploration存在=%v 引用它的task数=%d 当前MAX(exploration.id)=%d",
+					t.ID, storeID, t.ExpID, exists, refs, maxID)
+			}
+		}
 		e.touch(t.ID)
 		return
 	}
@@ -300,8 +322,8 @@ func (e *Engine) appendActivity(t *Task, r db.Activity) (int64, error) {
 			}
 			return id, nil
 		}
-		log.Printf("[activity] task %s 写入失败 (第 %d/3 次, worker=%s kind=%s tool=%s): %v",
-			t.ID, attempt, r.Worker, r.Kind, r.Tool, err)
+		log.Printf("[activity] task %s 写入失败 (第 %d/3 次, worker=%s kind=%s tool=%s expID=%d): %v",
+			t.ID, attempt, r.Worker, r.Kind, r.Tool, t.Store.ID(), err)
 		time.Sleep(time.Duration(attempt) * 25 * time.Millisecond)
 	}
 	return 0, err
diff --git a/web/src/app/(main)/system/logs/page.tsx b/web/src/app/(main)/system/logs/page.tsx
index cb89f45..9ba1fca 100644
--- a/web/src/app/(main)/system/logs/page.tsx
+++ b/web/src/app/(main)/system/logs/page.tsx
@@ -31,7 +31,9 @@ const levelDot: Record<LogLine["level"], string> = {
 
 function fmtTime(ts: string) {
   const d = new Date(ts);
-  return isNaN(d.getTime()) ? "" : d.toLocaleTimeString("zh-CN", { hour12: false });
+  if (isNaN(d.getTime())) return "";
+  const p = (n: number) => String(n).padStart(2, "0");
+  return `${d.getFullYear()}-${p(d.getMonth() + 1)}-${p(d.getDate())} ${p(d.getHours())}:${p(d.getMinutes())}:${p(d.getSeconds())}`;
 }
 
 export default function LogsPage() {