diff --git a/manifest b/manifest
index 94ba7c9f22..84b0a387af 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Merge\sthe\slatest\strunk\sfixes\sand\senhancements\sinto\sthe\sbedrock\sbranch.
-D 2024-12-07T23:29:06.209
+C Merge\schanges\sfrom\swal2,\sincluding\sthe\sfix\sto\sprevent\snon-PASSIVE\scheckpoints\sfrom\sever\staking\sthe\swriter\slock.
+D 2024-12-14T17:36:12.410
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
@@ -866,7 +866,7 @@ F src/vdbetrace.c fe0bc29ebd4e02c8bc5c1945f1d2e6be5927ec12c06d89b03ef2a4def34bf8
 F src/vdbevtab.c fc46b9cbd759dc013f0b3724549cc0d71379183c667df3a5988f7e2f1bd485f3
 F src/vtab.c 316cd48e9320660db3047cd306cd056e4361180cebb4d0f10a39244e10c11422
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c 77f875970ad28d658d3804c21bd72918604267478f1ee7986cceb7e765f0ba35
+F src/wal.c 3dfcce08758eec841bab07320c2b4e495c1c0621c2fd6327b3c3b19f52da48b6
 F src/wal.h 8d02ab8c2a93a941f5898eb3345bf711c1d3f8f86f4be8d5428fb6c074962d8a
 F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
 F src/where.c b34adb09fdb2a4f57a0bafd4194b501047ef383976fef9f0ac3f395f4881694d
@@ -2024,7 +2024,7 @@ F test/wal2recover3.test 4a91689e165a38bc401736e6518188c2b0ff4fa1566d1810b886753
 F test/wal2rewrite.test 6ca6f631ffcf871240beab5f02608913fd075c6d0d31310b026c8383c65c9f9c
 F test/wal2rollback.test 23adc4a099b23f6aaea8b04fdca1c35861d887dd80f8be7da2d5273eb777e428
 F test/wal2savepoint.test c2410acac73bfa63827f9346d060205080b747f0414ff27273d417dadfea28d0
-F test/wal2simple.test 320a08927f307d0ead26fa3fcef4e3f64279f49be9504f918cb33294f75aeec8
+F test/wal2simple.test d2d94fe1f30700c9f30e46c16f1c3d7d245b861a1be2bfe5ead701484c6dd38e
 F test/wal2snapshot.test f6c3945bea572fd8745774e95b8dca1e5832c696e2251bb0db33391ee567fe60
 F test/wal3.test 5de023bb862fd1eb9d2ad26fa8d9c43abb5370582e5b08b2ae0d6f93661bc310
 F test/wal4.test 4744e155cd6299c6bd99d3eab1c82f77db9cdb3c
@@ -2239,8 +2239,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P e03dd0bd313817da7ebf2989e1a423d95503044310d9efa02610d4d3a5973996 d3ce95f7e0335b8522a1805ab602b64856ced3007c507ba42039c6183ef9ac3d
-R d8823e691da2b0f9a9ba0ce3199f7f80
-U drh
-Z 2951534e15570812952f9e1a2d7a743c
+P 08cfa7e8b3090151a56b3898ebf0526d765b4ab276d1186d8c3e850c9408899d 88d7fb2aef882fc41a4f9c1bdd2f0162289e90d62df50af1b0eb6994c5c94c28
+R f44d51de9edfea1408778c5a30d0bdec
+U dan
+Z 1f3094698fe34000e0ec18f27e27e594
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index f87133fbe6..be068ab9d0 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-08cfa7e8b3090151a56b3898ebf0526d765b4ab276d1186d8c3e850c9408899d
+eb8449ea9ac8e29425f7127535a1db328d56c86382919fb1fcf42324b71de013
diff --git a/src/wal.c b/src/wal.c
index 8eb3912bfe..1f2db82f05 100644
--- a/src/wal.c
+++ b/src/wal.c
@@ -4947,37 +4947,61 @@ static int walRestartLog(Wal *pWal){
     int iApp = walidxGetFile(&pWal->hdr);
     u32 nWalSize = WAL_DEFAULT_WALSIZE;
     if( pWal->mxWalSize>0 ){
+      /* mxWalSize is in bytes. Convert this to a number of frames. */
       nWalSize = (pWal->mxWalSize-WAL_HDRSIZE+pWal->szPage+WAL_FRAME_HDRSIZE-1) 
         / (pWal->szPage+WAL_FRAME_HDRSIZE);
       nWalSize = MAX(nWalSize, 1);
     }
 
-    assert( 1==WAL_LOCK_PART1 );
-    assert( 4==WAL_LOCK_PART2 );
-    assert( 1+(iApp*3)==WAL_LOCK_PART1 || 1+(iApp*3)==WAL_LOCK_PART2 );
-    if( pWal->readLock==1+(iApp*3)
+    /* With a BEGIN CONCURRENT transaction, it is possible for a connection
+    ** to hold the WAL_LOCK_PART1 lock even if iApp==1 (or WAL_LOCK_PART2
+    ** when iApp==0). This is because a connection running concurrent to this
+    ** one may have switched the wal file after this connection took the
+    ** read lock.
+    **
+    ** This is not a problem, as if this happens it means the current lock 
+    ** is more restrictive, not less, than required. And a BEGIN CONCURRENT
+    ** transaction cannot be committed and downgraded to a read-transaction,
+    ** so there is no chance of continuing while holding the wrong lock.
+    */
+    assert( iApp==0 || pWal->readLock==WAL_LOCK_PART2 
+                    || pWal->readLock==WAL_LOCK_PART2_FULL1 
+                    || pWal->readLock==WAL_LOCK_PART1 );
+    assert( iApp==1 || pWal->readLock==WAL_LOCK_PART1 
+                    || pWal->readLock==WAL_LOCK_PART1_FULL2 
+                    || pWal->readLock==WAL_LOCK_PART2 );
+
+    /* Switch to wal file !iApp if 
+    **
+    **   (a) Wal file iApp (the current wal file) contains >= nWalSize frames.
+    **   (b) This client is not reading from wal file !iApp.
+    **   (c) No other client is reading from wal file !iApp.
+    **
+    ** Condition (b) guarantees that wal file !iApp is either empty or
+    ** completely checkpointed. 
+    */
+    assert( (0*3)+1==WAL_LOCK_PART1 ); /* iApp==0 -> require WAL_LOCK_PART1 */
+    assert( (1*3)+1==WAL_LOCK_PART2 ); /* iApp==1 -> require WAL_LOCK_PART2 */
+    if( pWal->readLock==(iApp*3)+1
      && walidxGetMxFrame(&pWal->hdr, iApp)>=nWalSize 
     ){
-      volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
-      u32 mxFrame = walidxGetMxFrame(&pWal->hdr, !iApp);
-      if( mxFrame==0 || pInfo->nBackfill ){
-        rc = wal2RestartOk(pWal, iApp);
-        if( rc==SQLITE_OK ){
-          int iNew = !iApp;
-          pWal->nCkpt++;
-          walidxSetFile(&pWal->hdr, iNew);
-          walidxSetMxFrame(&pWal->hdr, iNew, 0);
-          sqlite3Put4byte((u8*)&pWal->hdr.aSalt[0], pWal->hdr.aFrameCksum[0]);
-          sqlite3Put4byte((u8*)&pWal->hdr.aSalt[1], pWal->hdr.aFrameCksum[1]);
-          walIndexWriteHdr(pWal);
-          pInfo->nBackfill = 0;
-          wal2RestartFinished(pWal, iApp);
-          walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
-          pWal->readLock = iNew ? WAL_LOCK_PART2_FULL1 : WAL_LOCK_PART1_FULL2;
-          rc = walLockShared(pWal, WAL_READ_LOCK(pWal->readLock));
-        }else if( rc==SQLITE_BUSY ){
-          rc = SQLITE_OK;
-        }
+      rc = wal2RestartOk(pWal, iApp);
+      if( rc==SQLITE_OK ){
+        volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
+        int iNew = !iApp;
+        pWal->nCkpt++;
+        walidxSetFile(&pWal->hdr, iNew);
+        walidxSetMxFrame(&pWal->hdr, iNew, 0);
+        sqlite3Put4byte((u8*)&pWal->hdr.aSalt[0], pWal->hdr.aFrameCksum[0]);
+        sqlite3Put4byte((u8*)&pWal->hdr.aSalt[1], pWal->hdr.aFrameCksum[1]);
+        walIndexWriteHdr(pWal);
+        pInfo->nBackfill = 0;
+        wal2RestartFinished(pWal, iApp);
+        walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+        pWal->readLock = iNew ? WAL_LOCK_PART2_FULL1 : WAL_LOCK_PART1_FULL2;
+        rc = walLockShared(pWal, WAL_READ_LOCK(pWal->readLock));
+      }else if( rc==SQLITE_BUSY ){
+        rc = SQLITE_OK;
       }
     }
   }else if( pWal->readLock==0 ){
@@ -5504,7 +5528,7 @@ int sqlite3WalCheckpoint(
     ** writer lock retried until either the busy-handler returns 0 or the
     ** lock is successfully obtained.
     */
-    if( eMode!=SQLITE_CHECKPOINT_PASSIVE ){
+    if( eMode!=SQLITE_CHECKPOINT_PASSIVE && isWalMode2(pWal)==0 ){
       rc = walBusyLock(pWal, xBusy2, pBusyArg, WAL_WRITE_LOCK, 1);
       if( rc==SQLITE_OK ){
         pWal->writeLock = 1;
diff --git a/test/wal2simple.test b/test/wal2simple.test
index e63f4e1759..1a8c1e63bd 100644
--- a/test/wal2simple.test
+++ b/test/wal2simple.test
@@ -470,6 +470,74 @@ do_test 7.5.4 {
   list [file size test.db-wal] [file size test.db-wal2] [file size test.db]
 } {22040 12608 87040}
 
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 8.0 {
+  PRAGMA journal_size_limit = 10000;
+  PRAGMA journal_mode = wal2;
+  CREATE TABLE t1(x);
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  BEGIN;
+    INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+} {10000 wal2}
+
+sqlite3 db2 test.db
+do_execsql_test -db db2 8.1 {
+  PRAGMA wal_checkpoint;
+} {0 50 13}
+
+do_execsql_test 8.2 {
+  COMMIT;
+}
+
+db2 close
+
+
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 9.0 {
+  PRAGMA journal_size_limit = 10000;
+  PRAGMA journal_mode = wal2;
+  CREATE TABLE t1(x);
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+} {10000 wal2}
+
+do_execsql_test 9.1 {
+  PRAGMA wal_checkpoint;
+} {0 50 13}
+
+
+#-------------------------------------------------------------------------
+# Check that it is possible to do a non-PASSIVE checkpoint on a wal2
+# db without blocking writers.
+#
+reset_db
+do_execsql_test 10.0 {
+  PRAGMA journal_size_limit = 10000;
+  PRAGMA journal_mode = wal2;
+  CREATE TABLE t1(x);
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+  BEGIN;
+    INSERT INTO t1 VALUES( hex( randomblob(5000) ) );
+} {10000 wal2}
+
+sqlite3 db2 test.db
+do_execsql_test -db db2 10.1 {
+  PRAGMA wal_checkpoint = FULL;
+} {0 50 13}
+
+do_execsql_test 10.2 {
+  COMMIT;
+}
 
 finish_test