Index: ext/wasm/api/sqlite3-vfs-opfs-sahpool.c-pp.js
==================================================================
--- ext/wasm/api/sqlite3-vfs-opfs-sahpool.c-pp.js
+++ ext/wasm/api/sqlite3-vfs-opfs-sahpool.c-pp.js
@@ -77,10 +77,52 @@
   const PERSISTENT_FILE_TYPES =
         capi.SQLITE_OPEN_MAIN_DB |
         capi.SQLITE_OPEN_MAIN_JOURNAL |
         capi.SQLITE_OPEN_SUPER_JOURNAL |
         capi.SQLITE_OPEN_WAL;
+  const FLAG_COMPUTE_DIGEST_V2 = capi.SQLITE_OPEN_MEMORY
+  /* Part of the fix for
+     https://github.com/sqlite/sqlite-wasm/issues/97
+
+     Summary: prior to version 3.50.0 computeDigest() always computes
+     a value of [0,0] due to overflows, so it does not do anything
+     useful.  Fixing it invalidates old persistent files, so we
+     instead only fix it for files created or updated since the bug
+     was discovered and fixed.
+
+     This flag determines whether we use the broken legacy
+     computeDigest() or the v2 variant. We only use this flag for
+     newly-created/overwritten files. Pre-existing files have the
+     broken digest stored in them so need to continue to use that.
+
+     What this means, in terms of db file compatibility between
+     versions:
+
+     - DBs created with versions older than this fix (<3.50.0)
+     can be read by post-fix versions. Such DBs which are written
+     to in-place (not replaced) by newer versions can still be read
+     by older versions, as the affected digest is only modified
+     when the SAH slot is assigned to a given filename.
+
+     - DBs created with post-fix versions will, when read by a pre-fix
+     version, be seen as having a "bad digest" and will be
+     unceremoniously replaced by that pre-fix version. When swapping
+     back to a post-fix version, that version will see that the file
+     entry is missing the FLAG_COMPUTE_DIGEST_V2 bit so will treat it
+     as a legacy file.
+
+     This flag is stored in the same memory as the various
+     SQLITE_OPEN_... flags and we must be careful here to not use a
+     flag bit which is otherwise relevant for the VFS.
+     SQLITE_OPEN_MEMORY is handled by sqlite3_open_v2() and friends,
+     not the VFS, so we'll repurpose that one.  If we take a
+     currently-unused bit and it ends up, at some later point, being
+     used, we would have to invalidate existing VFS files in order to
+     move to another bit.  Similarly, if the SQLITE_OPEN_MEMORY bit
+     were ever reassigned (which it won't be!), we'd invalidate all
+     VFS-side files.
+  */;
 
   /** Subdirectory of the VFS's space where "opaque" (randomly-named)
       files are stored. Changing this effectively invalidates the data
       stored under older names (orphaning it), so don't do that. */
   const OPAQUE_DIR_NAME = ".opaque";
@@ -327,10 +369,11 @@
     },
     //xSleep is optionally defined below
     xOpen: function f(pVfs, zName, pFile, flags, pOutFlags){
       const pool = getPoolForVfs(pVfs);
       try{
+        flags &= ~FLAG_COMPUTE_DIGEST_V2;
         pool.log(`xOpen ${wasm.cstrToJs(zName)} ${flags}`);
         // First try to open a path that already exists in the file system.
         const path = (zName && wasm.peek8(zName))
               ? pool.getPath(zName)
               : getRandomName();
@@ -622,11 +665,12 @@
         return '';
       }
 
       const fileDigest = new Uint32Array(HEADER_DIGEST_SIZE / 4);
       sah.read(fileDigest, {at: HEADER_OFFSET_DIGEST});
-      const compDigest = this.computeDigest(this.#apBody);
+      const compDigest = this.computeDigest(this.#apBody, flags);
+      //warn("getAssociatedPath() flags",'0x'+flags.toString(16), "compDigest", compDigest);
       if(fileDigest.every((v,i) => v===compDigest[i])){
         // Valid digest
         const pathBytes = this.#apBody.findIndex((v)=>0===v);
         if(0===pathBytes){
           // This file is unassociated, so truncate it to avoid
@@ -653,14 +697,21 @@
     setAssociatedPath(sah, path, flags){
       const enc = textEncoder.encodeInto(path, this.#apBody);
       if(HEADER_MAX_PATH_SIZE <= enc.written + 1/*NUL byte*/){
         toss("Path too long:",path);
       }
+      if(path && flags){
+        /* When creating or re-writing files, update their digest, if
+           needed, to v2. We continue to use v1 for the (!path) case
+           (empty files) because there's little reason not to use a
+           digest of 0 for empty entries. */
+        flags |= FLAG_COMPUTE_DIGEST_V2;
+      }
       this.#apBody.fill(0, enc.written, HEADER_MAX_PATH_SIZE);
       this.#dvBody.setUint32(HEADER_OFFSET_FLAGS, flags);
-
-      const digest = this.computeDigest(this.#apBody);
+      const digest = this.computeDigest(this.#apBody, flags);
+      //console.warn("setAssociatedPath(",path,") digest",digest);
       sah.write(this.#apBody, {at: 0});
       sah.write(digest, {at: HEADER_OFFSET_DIGEST});
       sah.flush();
 
       if(path){
@@ -677,19 +728,26 @@
        Computes a digest for the given byte array and returns it as a
        two-element Uint32Array. This digest gets stored in the
        metadata for each file as a validation check. Changing this
        algorithm invalidates all existing databases for this VFS, so
        don't do that.
+
+       See the docs for FLAG_COMPUTE_DIGEST_V2 for more details.
     */
-    computeDigest(byteArray){
-      let h1 = 0xdeadbeef;
-      let h2 = 0x41c6ce57;
-      for(const v of byteArray){
-        h1 = 31 * h1 + (v * 307);
-        h2 = 31 * h2 + (v * 307);
-      }
-      return new Uint32Array([h1>>>0, h2>>>0]);
+    computeDigest(byteArray, fileFlags){
+      if( fileFlags & FLAG_COMPUTE_DIGEST_V2 ){
+        let h1 = 0xdeadbeef;
+        let h2 = 0x41c6ce57;
+        for(const v of byteArray){
+          h1 = Math.imul(h1 ^ v, 2654435761);
+          h2 = Math.imul(h2 ^ v, 104729);
+        }
+        return new Uint32Array([h1>>>0, h2>>>0]);
+      }else{
+        /* this is what the buggy legacy computation worked out to */
+        return new Uint32Array([0,0]);
+      }
     }
 
     /**
        Re-initializes the state of the SAH pool, releasing and
        re-acquiring all handles.

Index: ext/wasm/tester1.c-pp.js
==================================================================
--- ext/wasm/tester1.c-pp.js
+++ ext/wasm/tester1.c-pp.js
@@ -3504,11 +3504,11 @@
               return x;
             }
           });
           db.exec([
             "create table t(a);",
-            "insert into t(a) values(1),(2),(3);",
+            "insert into t(a) values(1),(2),(1);",
             "select auxtest(1,a), auxtest(1,a) from t order by a"
           ]);
         }finally{
           db.close();
           wasm.pstack.restore(stack);

ADDED   ext/wasm/tests/opfs/sahpool/digest-worker.js
Index: ext/wasm/tests/opfs/sahpool/digest-worker.js
==================================================================
--- /dev/null
+++ ext/wasm/tests/opfs/sahpool/digest-worker.js
@@ -0,0 +1,94 @@
+/*
+  2025-01-31
+
+  The author disclaims copyright to this source code.  In place of a
+  legal notice, here is a blessing:
+
+  *   May you do good and not evil.
+  *   May you find forgiveness for yourself and forgive others.
+  *   May you share freely, never taking more than you give.
+
+  ***********************************************************************
+
+  This file is part of sahpool-pausing.js's demonstration of the
+  pause/unpause feature of the opfs-sahpool VFS.
+*/
+const clog = console.log.bind(console);
+const wPost = (type,...args)=>postMessage({type, payload:args});
+const log = (...args)=>{
+  clog("Worker:",...args);
+  wPost('log',...args);
+}
+
+const hasOpfs = ()=>{
+  return globalThis.FileSystemHandle
+    && globalThis.FileSystemDirectoryHandle
+    && globalThis.FileSystemFileHandle
+    && globalThis.FileSystemFileHandle.prototype.createSyncAccessHandle
+    && navigator?.storage?.getDirectory;
+};
+if( !hasOpfs() ){
+  wPost('error',"OPFS not detected");
+  throw new Error("OPFS not detected");
+}
+
+clog("Importing sqlite3...");
+const searchParams = new URL(self.location.href).searchParams;
+importScripts(searchParams.get('sqlite3.dir') + '/sqlite3.js');
+
+const runTests = function(sqlite3, poolUtil){
+  const fname = '/my.db';
+  let db = new poolUtil.OpfsSAHPoolDb(fname);
+  let n = (new Date()).valueOf();
+  try {
+    db.exec([
+      "create table if not exists t(a);"
+    ]);
+    db.exec({
+      sql: "insert into t(a) values(?)",
+      bind: n++
+    });
+    log(fname,"record count: ",db.selectValue("select count(*) from t"));
+  }finally{
+    db.close();
+  }
+
+  db = new poolUtil.OpfsSAHPoolDb(fname);
+  try {
+    db.exec({
+      sql: "insert into t(a) values(?)",
+      bind: n++
+    });
+    log(fname,"record count: ",db.selectValue("select count(*) from t"));
+  }finally{
+    db.close();
+  }
+
+  const fname2 = '/my2.db';
+  db = new poolUtil.OpfsSAHPoolDb(fname2);
+  try {
+    db.exec([
+      "create table if not exists t(a);"
+    ]);
+    db.exec({
+      sql: "insert into t(a) values(?)",
+      bind: n++
+    });
+    log(fname2,"record count: ",db.selectValue("select count(*) from t"));
+  }finally{
+    db.close();
+  }
+};
+
+globalThis.sqlite3InitModule().then(async function(sqlite3){
+  log("sqlite3 version:",sqlite3.version);
+  const sahPoolConfig = {
+    name: 'opfs-sahpool-digest',
+    clearOnInit: false,
+    initialCapacity: 6
+  };
+  return sqlite3.installOpfsSAHPoolVfs(sahPoolConfig).then(poolUtil=>{
+    log('vfs acquired');
+    runTests(sqlite3, poolUtil);
+  });
+});

ADDED   ext/wasm/tests/opfs/sahpool/digest.html
Index: ext/wasm/tests/opfs/sahpool/digest.html
==================================================================
--- /dev/null
+++ ext/wasm/tests/opfs/sahpool/digest.html
@@ -0,0 +1,141 @@
+<!doctype html>
+<html lang="en-us">
+  <head>
+    <meta charset="utf-8">
+    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+    <link rel="shortcut icon" href="data:image/x-icon;," type="image/x-icon">
+    <link rel="stylesheet" href="../../../common/emscripten.css"/>
+    <link rel="stylesheet" href="../../../common/testing.css"/>
+    <title>sqlite3 tester: OpfsSAHPool Digest</title>
+    <style></style>
+  </head>
+  <body><h1 id='color-target'></h1>
+
+    <p>
+      This is a test app for the digest calculation of the OPFS
+      SAHPool VFS. It requires running it with a new database created using
+      v3.49.0 or older, then running it again with a newer version, then
+      again with 3.49.0 or older.
+    </p>
+    <div class='input-wrapper'>
+      <input type='checkbox' id='cb-log-reverse'>
+      <label for='cb-log-reverse'>Reverse log order?</label>
+    </div>
+    <div id='test-output'></div>
+    <script>
+      /*
+        2025-02-03
+
+        The author disclaims copyright to this source code.  In place of a
+        legal notice, here is a blessing:
+
+        *   May you do good and not evil.
+        *   May you find forgiveness for yourself and forgive others.
+        *   May you share freely, never taking more than you give.
+
+        ***********************************************************************
+
+        This is a bugfix test for the OPFS SAHPool VFS. It requires setting up
+        a database created using v3.49.0 or older, then running it again with
+        a newer version.
+      */
+      (function(){
+        'use strict';
+        document.querySelector('h1').innerHTML =
+        document.querySelector('title').innerHTML;
+        const mapToString = (v)=>{
+          switch(typeof v){
+            case 'number': case 'string': case 'boolean':
+            case 'undefined': case 'bigint':
+              return ''+v;
+            default: break;
+          }
+          if(null===v) return 'null';
+          if(v instanceof Error){
+            v = {
+              message: v.message,
+              stack: v.stack,
+              errorClass: v.name
+            };
+          }
+          return JSON.stringify(v,undefined,2);
+        };
+        const normalizeArgs = (args)=>args.map(mapToString);
+        const logTarget = document.querySelector('#test-output');
+        const logClass = function(cssClass,...args){
+          const ln = document.createElement('div');
+          if(cssClass){
+            for(const c of (Array.isArray(cssClass) ? cssClass : [cssClass])){
+              ln.classList.add(c);
+            }
+          }
+          ln.append(document.createTextNode(normalizeArgs(args).join(' ')));
+          logTarget.append(ln);
+        };
+        const cbReverse = document.querySelector('#cb-log-reverse');
+        //cbReverse.setAttribute('checked','checked');
+        const cbReverseKey = 'tester1:cb-log-reverse';
+        const cbReverseIt = ()=>{
+          logTarget.classList[cbReverse.checked ? 'add' : 'remove']('reverse');
+          //localStorage.setItem(cbReverseKey, cbReverse.checked ? 1 : 0);
+        };
+        cbReverse.addEventListener('change', cbReverseIt, true);
+        /*if(localStorage.getItem(cbReverseKey)){
+          cbReverse.checked = !!(+localStorage.getItem(cbReverseKey));
+          }*/
+        cbReverseIt();
+
+        const log = (...args)=>{
+          //console.log(...args);
+          logClass('',...args);
+        }
+        const warn = (...args)=>{
+          console.warn(...args);
+          logClass('warning',...args);
+        }
+        const error = (...args)=>{
+          console.error(...args);
+          logClass('error',...args);
+        };
+
+        const toss = (...args)=>{
+          error(...args);
+          throw new Error(args.join(' '));
+        };
+
+        const endOfWork = (passed=true)=>{
+          const eH = document.querySelector('#color-target');
+          const eT = document.querySelector('title');
+          if(passed){
+            log("End of work chain. If you made it this far, you win.");
+            eH.innerText = 'PASS: '+eH.innerText;
+            eH.classList.add('tests-pass');
+            eT.innerText = 'PASS: '+eT.innerText;
+          }else{
+            eH.innerText = 'FAIL: '+eH.innerText;
+            eH.classList.add('tests-fail');
+            eT.innerText = 'FAIL: '+eT.innerText;
+          }
+        };
+
+        log("Running opfs-sahpool digest tests...");
+        const W1 = new Worker('digest-worker.js?sqlite3.dir=../../../jswasm');
+        W1.onmessage = function({data}){
+          //log("onmessage:",data);
+          switch(data.type){
+            case 'log':
+              log('worker says:', ...data.payload);
+              break;
+            case 'error':
+              error('worker says:', ...data.payload);
+              endOfWork(false);
+              break;
+            case 'initialized':
+              log(data.workerId, ': Worker initialized',...data.payload);
+              break;
+          }
+        };
+      })();
+    </script>
+  </body>
+</html>