fix(sessions): complete tail-read windows despite short positional reads

Monkey-wusky · Monkey-wusky · commit fe5295bc2b80 · 2026-07-16T14:02:43.000+08:00
Replace single-shot handle.read() calls in two session tail-read paths with readFileWindowFully so multibyte-range positional reads do not silently return incomplete tail data on network filesystems. - readRecentTranscriptTailLinesAsync: tail-window read for recent session messages now loops until the requested window fills - readLastMessagePreviewFromOpenTranscriptAsync: last-message preview tail read now loops until the requested window fills The same readFileWindowFully helper was introduced in #108253 and expanded with a sync variant in #108127 (both by sunlit-deng).
diff --git a/src/gateway/session-utils.fs.test.ts b/src/gateway/session-utils.fs.test.ts
@@ -2036,4 +2036,88 @@ describe("oversized transcript line guards", () => {
     expect(asyncResult.lastMessagePreview).toBe("Bot says hello");
   });
 });
+
+describe("short read resilience", () => {
+  let tmpDir: string;
+  let storePath: string;
+
+  registerTempSessionStore("openclaw-short-read-test-", (nextTmpDir, nextStorePath) => {
+    tmpDir = nextTmpDir;
+    storePath = nextStorePath;
+  });
+
+  function installShortReadProxy(maxPerCall = 16) {
+    const realOpen = fs.promises.open.bind(fs.promises);
+    return vi.spyOn(fs.promises, "open").mockImplementation(async (...args: unknown[]) => {
+      const handle = await realOpen(...(args as Parameters<typeof realOpen>));
+      const realRead = handle.read.bind(handle);
+      return new Proxy(handle, {
+        get(target, prop, receiver) {
+          if (prop !== "read") return Reflect.get(target, prop, receiver);
+          return (buf: Buffer, offset: number, length: number, position: number | null) =>
+            realRead(buf, offset, Math.min(length, maxPerCall), position);
+        },
+      });
+    });
+  }
+
+  test("readRecentSessionMessagesAsync survives 16-byte tail read caps", async () => {
+    const sessionId = "test-short-read-recent";
+    const lines = [
+      { type: "session", version: 1, id: sessionId },
+      ...Array.from({ length: 30 }, (_, i) => ({
+        message: {
+          role: i % 2 ? "assistant" : "user",
+          content: `message ${i}: ${"data ".repeat(40)}`,
+        },
+      })),
+    ];
+    writeTranscript(tmpDir, sessionId, lines);
+
+    installShortReadProxy(16);
+    try {
+      const result = await readRecentSessionMessagesAsync(sessionId, storePath, undefined, {
+        maxMessages: 20,
+        maxBytes: 8192,
+      });
+      expect(result.length).toBeGreaterThanOrEqual(5);
+      for (const msg of result) {
+        const content = (msg as Record<string, unknown>).content as string;
+        expect(content).toBeTruthy();
+      }
+    } finally {
+      vi.restoreAllMocks();
+    }
+  });
+
+  test("readRecentSessionMessagesAsync honors maxBytes under short reads", async () => {
+    const sessionId = "test-short-read-byte-cap";
+    const lines = [
+      { type: "session", version: 1, id: sessionId },
+      ...Array.from({ length: 20 }, (_, i) => ({
+        message: {
+          role: i % 2 ? "assistant" : "user",
+          content: `line ${String(i).padStart(2, "0")}: ${"payload ".repeat(30)}`,
+        },
+      })),
+    ];
+    writeTranscript(tmpDir, sessionId, lines);
+
+    const normal = await readRecentSessionMessagesAsync(sessionId, storePath, undefined, {
+      maxMessages: 20,
+      maxBytes: 4096,
+    });
+
+    installShortReadProxy(64);
+    try {
+      const short = await readRecentSessionMessagesAsync(sessionId, storePath, undefined, {
+        maxMessages: 20,
+        maxBytes: 4096,
+      });
+      expect(Math.abs(short.length - normal.length)).toBeLessThanOrEqual(1);
+    } finally {
+      vi.restoreAllMocks();
+    }
+  });
+});
 /* oxlint-disable max-lines -- TODO: split this grandfathered oversized file. */
diff --git a/src/gateway/session-utils.fs.ts b/src/gateway/session-utils.fs.ts
@@ -19,6 +19,7 @@ import {
   scanSessionTranscriptTree,
   selectSessionTranscriptTreePathNodes,
 } from "../config/sessions/transcript-tree.js";
+import { readFileWindowFully } from "../infra/file-read.js";
 import { jsonUtf8Bytes } from "../infra/json-utf8-bytes.js";
 import { hasInterSessionUserProvenance } from "../sessions/input-provenance.js";
 import { extractAssistantVisibleText } from "../shared/chat-message-content.js";
@@ -255,7 +256,7 @@ async function readRecentTranscriptTailLinesAsync(
   const handle = await fs.promises.open(filePath, "r");
   try {
     const buffer = Buffer.alloc(readLen);
-    const { bytesRead } = await handle.read(buffer, 0, readLen, readStart);
+    const bytesRead = await readFileWindowFully(handle, buffer, readStart);
     if (bytesRead <= 0) {
       return [];
     }
@@ -1188,7 +1189,7 @@ async function readLastMessagePreviewFromOpenTranscriptAsync(params: {
   const readStart = Math.max(0, params.size - LAST_MSG_MAX_BYTES);
   const readLen = Math.min(params.size, LAST_MSG_MAX_BYTES);
   const buffer = Buffer.alloc(readLen);
-  const { bytesRead } = await params.handle.read(buffer, 0, readLen, readStart);
+  const bytesRead = await readFileWindowFully(params.handle, buffer, readStart);
   if (bytesRead <= 0) {
     return null;
   }
