diff --git a/src/agents/sessions/session-manager.test.ts b/src/agents/sessions/session-manager.test.ts
index 14092ad99944..cd713e2c25f7 100644
--- a/src/agents/sessions/session-manager.test.ts
+++ b/src/agents/sessions/session-manager.test.ts
@@ -6,6 +6,7 @@ import os from "node:os";
 import path from "node:path";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import { withOwnedSessionTranscriptWrites } from "../../config/sessions/transcript-write-context.js";
+import * as Logger from "../../logger.js";
 import { isTranscriptOnlyOpenClawAssistantMessage } from "../../shared/transcript-only-openclaw-assistant.js";
 import { prepareSessionManagerForRun } from "../embedded-agent-runner/session-manager-init.js";
 import { repairSessionFileIfNeeded } from "../session-file-repair.js";
@@ -13,6 +14,7 @@ import {
   CURRENT_SESSION_VERSION,
   findMostRecentSession,
   loadEntriesFromFile,
+  parseSessionEntries,
   SessionManager,
   type SessionEntry,
 } from "./session-manager.js";
@@ -2647,6 +2649,140 @@ describe("SessionManager.open", () => {
   });
 });
 
+describe("parseSessionEntries", () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("parses valid JSONL lines without logging warnings", () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const content = [
+      JSON.stringify({ type: "session", id: "s1" }),
+      JSON.stringify({ type: "message", id: "m1" }),
+    ].join("\n");
+
+    const entries = parseSessionEntries(content);
+
+    expect(entries).toHaveLength(2);
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it("logs a warning and skips malformed JSONL lines while preserving valid entries", () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const content = [
+      JSON.stringify({ type: "session", id: "s1" }),
+      "not valid json {{{",
+      JSON.stringify({ type: "message", id: "m1" }),
+    ].join("\n");
+
+    const entries = parseSessionEntries(content);
+
+    expect(entries).toHaveLength(2);
+    expect(warnSpy).toHaveBeenCalledTimes(1);
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining("parseJsonlEntries: skipped 1 malformed JSONL line"),
+    );
+  });
+
+  it("reports the correct skip count for multiple malformed lines", () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const content = [
+      "bad line 1",
+      JSON.stringify({ type: "session", id: "s1" }),
+      "bad line 2",
+      "bad line 3",
+    ].join("\n");
+
+    const entries = parseSessionEntries(content);
+
+    expect(entries).toHaveLength(1);
+    expect(warnSpy).toHaveBeenCalledTimes(1);
+    expect(warnSpy).toHaveBeenCalledWith(
+      expect.stringContaining("parseJsonlEntries: skipped 3 malformed JSONL line"),
+    );
+  });
+
+  it("skips empty lines without counting them as malformed", () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const content = [
+      "",
+      JSON.stringify({ type: "session", id: "s1" }),
+      "",
+      JSON.stringify({ type: "message", id: "m1" }),
+      "",
+    ].join("\n");
+
+    const entries = parseSessionEntries(content);
+
+    expect(entries).toHaveLength(2);
+    expect(warnSpy).not.toHaveBeenCalled();
+  });
+
+  it("parseJsonlEntries logs warning for malformed lines via loadEntriesFromFile", async () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const dir = await makeTempDir();
+    const sessionFile = path.join(dir, "session.jsonl");
+    const header = buildSessionHeader(dir);
+    const content = [
+      JSON.stringify(header),
+      "not valid json {{{",
+      JSON.stringify(buildMessageEntry(1, null)),
+    ].join("\n");
+    await fs.writeFile(sessionFile, content, "utf8");
+
+    const entries = loadEntriesFromFile(sessionFile);
+
+    expect(entries.length).toBeGreaterThanOrEqual(1);
+    expect(warnSpy).toHaveBeenCalled();
+    expect(
+      warnSpy.mock.calls.some((call) =>
+        call[0].includes("parseJsonlEntries: skipped 1 malformed JSONL line"),
+      ),
+    ).toBe(true);
+  });
+
+  it("buildSessionInfo logs warning for malformed lines via SessionManager.list", async () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const dir = await makeTempDir();
+    const sessionFile = path.join(dir, "session.jsonl");
+    const header = buildSessionHeader(dir);
+    const content = [
+      JSON.stringify(header),
+      "not valid json {{{",
+      JSON.stringify(buildMessageEntry(1, null)),
+    ].join("\n");
+    await fs.writeFile(sessionFile, content, "utf8");
+
+    const sessions = await SessionManager.list(dir, dir);
+
+    expect(sessions).toHaveLength(1);
+    expect(warnSpy).toHaveBeenCalled();
+    expect(
+      warnSpy.mock.calls.some((call) =>
+        call[0].includes("buildSessionInfo: skipped 1 malformed JSONL line"),
+      ),
+    ).toBe(true);
+  });
+
+  it("buildSessionInfo does not log warning for clean session listing", async () => {
+    const warnSpy = vi.spyOn(Logger, "logWarn").mockImplementation(() => {});
+    const dir = await makeTempDir();
+    const sessionFile = path.join(dir, "session.jsonl");
+    const header = buildSessionHeader(dir);
+    const content = [JSON.stringify(header), JSON.stringify(buildMessageEntry(1, null))].join("\n");
+    await fs.writeFile(sessionFile, content, "utf8");
+
+    const sessions = await SessionManager.list(dir, dir);
+
+    expect(sessions).toHaveLength(1);
+    // buildSessionInfo must not log any warning for a clean listing.
+    const buildSessionInfoCalls = warnSpy.mock.calls.filter((call) =>
+      call[0].includes("buildSessionInfo"),
+    );
+    expect(buildSessionInfoCalls).toHaveLength(0);
+  });
+});
+
 function readMessageContent(entry: SessionEntry): unknown {
   const content = (entry as { message: { content: unknown } }).message.content;
   if (Array.isArray(content)) {
diff --git a/src/agents/sessions/session-manager.ts b/src/agents/sessions/session-manager.ts
index 4f9e3e152f46..9b808ee9ba79 100644
--- a/src/agents/sessions/session-manager.ts
+++ b/src/agents/sessions/session-manager.ts
@@ -38,6 +38,7 @@ import {
 } from "../../config/sessions/transcript-write-context.js";
 import { CURRENT_SESSION_VERSION } from "../../config/sessions/version.js";
 import type { ImageContent, Message, TextContent } from "../../llm/types.js";
+import { logWarn } from "../../logger.js";
 import { getAgentDir as getDefaultAgentDir, getSessionsDir } from "../config.js";
 import {
   type AgentMessage,
@@ -938,6 +939,7 @@ function freezeJsonLikeValue(value: unknown, seen = new WeakSet<object>()): void
 function parseJsonlEntries(content: string): FileEntry[] {
   const entries: FileEntry[] = [];
   const lines = content.trim().split("\n");
+  let skipped = 0;
 
   for (const line of lines) {
     if (!line.trim()) {
@@ -947,10 +949,20 @@ function parseJsonlEntries(content: string): FileEntry[] {
       const entry = JSON.parse(line) as FileEntry;
       entries.push(normalizeLoadedFileEntry(entry));
     } catch {
-      // Skip malformed lines
+      skipped++;
     }
   }
 
+  // Transcripts written by older code or repaired externally may contain
+  // malformed entries that JSON.parse cannot deserialize. Warn once so the
+  // operator knows data was skipped instead of silently dropping entries.
+  if (skipped > 0) {
+    logWarn(
+      `parseJsonlEntries: skipped ${skipped} malformed JSONL line(s) — ` +
+        `${entries.length} valid entries were loaded`,
+    );
+  }
+
   return entries;
 }
 
@@ -1283,6 +1295,7 @@ async function buildSessionInfo(filePath: string): Promise<SessionInfo | null> {
     const content = await readFile(filePath, "utf8");
     const entries: FileEntry[] = [];
     const lines = content.trim().split("\n");
+    let skipped = 0;
 
     for (const line of lines) {
       if (!line.trim()) {
@@ -1291,10 +1304,17 @@ async function buildSessionInfo(filePath: string): Promise<SessionInfo | null> {
       try {
         entries.push(JSON.parse(line) as FileEntry);
       } catch {
-        // Skip malformed lines
+        skipped++;
       }
     }
 
+    if (skipped > 0) {
+      logWarn(
+        `buildSessionInfo: skipped ${skipped} malformed JSONL line(s) in ${filePath} — ` +
+          `${entries.length} valid entries were loaded`,
+      );
+    }
+
     if (entries.length === 0) {
       return null;
     }