diff --git a/src/hooks/pre-read.ts b/src/hooks/pre-read.ts
index 335b140..988c7e5 100644
--- a/src/hooks/pre-read.ts
+++ b/src/hooks/pre-read.ts
@@ -5,10 +5,11 @@ import {
   estimateTokens, readStdin, normalizePath, getProjectDir
 } from "./shared.js";
 import { lookupEntry } from "./anatomy-store.js";
+import { trackRead, type FileReadEntry } from "./read-tracking.js";
 
 interface SessionData {
   session_id: string;
-  files_read: Record<string, { count: number; tokens: number; first_read: string }>;
+  files_read: Record<string, FileReadEntry>;
   anatomy_hits: number;
   anatomy_misses: number;
   repeated_reads_warned: number;
@@ -51,13 +52,20 @@ async function main(): Promise<void> {
     repeated_reads_warned: 0,
   });
 
-  // Check if already read this session
-  if (session.files_read[normalizedFile]) {
-    const prev = session.files_read[normalizedFile];
+  let currentMtime: number | undefined;
+  try {
+    const absolutePath = path.isAbsolute(filePath) ? filePath : path.join(projectDir, filePath);
+    currentMtime = fs.statSync(absolutePath).mtimeMs;
+  } catch {}
+
+  const previous = session.files_read[normalizedFile];
+  const read = trackRead(previous, currentMtime, new Date().toISOString());
+
+  if (previous && read.repeated) {
     process.stderr.write(
-      `⚡ OpenWolf: ${path.basename(normalizedFile)} was already read this session (~${prev.tokens} tokens). Consider using your existing knowledge of this file.\n`
+      `⚡ OpenWolf: ${path.basename(normalizedFile)} was already read this session (~${previous.tokens} tokens). Consider using your existing knowledge of this file.\n`
     );
-    session.files_read[normalizedFile].count++;
+    session.files_read[normalizedFile] = read.entry;
     session.repeated_reads_warned++;
     writeJSON(sessionFile, session);
     process.exit(0);
@@ -99,11 +107,7 @@ async function main(): Promise<void> {
   }
 
   // Record initial read entry (tokens will be updated in post-read)
-  session.files_read[normalizedFile] = {
-    count: 1,
-    tokens: 0,
-    first_read: new Date().toISOString(),
-  };
+  session.files_read[normalizedFile] = read.entry;
 
   writeJSON(sessionFile, session);
   process.exit(0);
diff --git a/src/hooks/read-tracking.ts b/src/hooks/read-tracking.ts
new file mode 100644
index 0000000..d96cfd3
--- /dev/null
+++ b/src/hooks/read-tracking.ts
@@ -0,0 +1,43 @@
+export interface FileReadEntry {
+  count: number;
+  tokens: number;
+  first_read: string;
+  read_mtime?: number;
+}
+
+interface ReadTransition {
+  entry: FileReadEntry;
+  repeated: boolean;
+}
+
+export function trackRead(
+  previous: FileReadEntry | undefined,
+  currentMtime: number | undefined,
+  readAt: string
+): ReadTransition {
+  const changed =
+    previous?.read_mtime !== undefined &&
+    currentMtime !== undefined &&
+    previous.read_mtime !== currentMtime;
+
+  if (previous && !changed) {
+    return {
+      repeated: true,
+      entry: {
+        ...previous,
+        count: previous.count + 1,
+        read_mtime: previous.read_mtime ?? currentMtime,
+      },
+    };
+  }
+
+  return {
+    repeated: false,
+    entry: {
+      count: 1,
+      tokens: 0,
+      first_read: readAt,
+      read_mtime: currentMtime,
+    },
+  };
+}
diff --git a/tests/pre-read.test.ts b/tests/pre-read.test.ts
new file mode 100644
index 0000000..70c018b
--- /dev/null
+++ b/tests/pre-read.test.ts
@@ -0,0 +1,57 @@
+import { test } from "node:test";
+import * as assert from "node:assert";
+
+import { trackRead, type FileReadEntry } from "../src/hooks/read-tracking.ts";
+
+const firstRead: FileReadEntry = {
+  count: 1,
+  tokens: 42,
+  first_read: "2026-07-15T00:00:00.000Z",
+  read_mtime: 1_700_000_000_000,
+};
+
+test("starts a new read entry with the current mtime", () => {
+  const result = trackRead(undefined, 1_700_000_000_000, "2026-07-15T00:00:00.000Z");
+
+  assert.strictEqual(result.repeated, false);
+  assert.deepStrictEqual(result.entry, {
+    count: 1,
+    tokens: 0,
+    first_read: "2026-07-15T00:00:00.000Z",
+    read_mtime: 1_700_000_000_000,
+  });
+});
+
+test("warns and preserves the baseline when the mtime is unchanged", () => {
+  const result = trackRead(firstRead, firstRead.read_mtime, "2026-07-15T00:01:00.000Z");
+
+  assert.strictEqual(result.repeated, true);
+  assert.deepStrictEqual(result.entry, { ...firstRead, count: 2 });
+});
+
+test("starts a fresh baseline when the mtime changed", () => {
+  const result = trackRead(firstRead, 1_700_000_100_000, "2026-07-15T00:01:00.000Z");
+
+  assert.strictEqual(result.repeated, false);
+  assert.deepStrictEqual(result.entry, {
+    count: 1,
+    tokens: 0,
+    first_read: "2026-07-15T00:01:00.000Z",
+    read_mtime: 1_700_000_100_000,
+  });
+});
+
+test("warns for a legacy entry and records its current mtime", () => {
+  const { read_mtime: _readMtime, ...legacyEntry } = firstRead;
+  const result = trackRead(legacyEntry, 1_700_000_000_000, "2026-07-15T00:01:00.000Z");
+
+  assert.strictEqual(result.repeated, true);
+  assert.deepStrictEqual(result.entry, { ...firstRead, count: 2 });
+});
+
+test("warns conservatively when the current mtime is unavailable", () => {
+  const result = trackRead(firstRead, undefined, "2026-07-15T00:01:00.000Z");
+
+  assert.strictEqual(result.repeated, true);
+  assert.deepStrictEqual(result.entry, { ...firstRead, count: 2 });
+});