Index: ext/fts5/fts5_aux.c
==================================================================
--- ext/fts5/fts5_aux.c
+++ ext/fts5/fts5_aux.c
@@ -243,10 +243,119 @@
   }
 }
 /*
 ** End of highlight() implementation.
 **************************************************************************/
+
+/*
+** Context object passed to the fts5SentenceFinderCb() function.
+*/
+typedef struct Fts5SFinder Fts5SFinder;
+struct Fts5SFinder {
+  int iPos;                       /* Current token position */
+  int nFirstAlloc;                /* Allocated size of aFirst[] */
+  int nFirst;                     /* Number of entries in aFirst[] */
+  int *aFirst;                    /* Array of first token in each sentence */
+  const char *zDoc;               /* Document being tokenized */
+};
+
+/*
+** Add an entry to the Fts5SFinder.aFirst[] array. Grow the array if
+** necessary. Return SQLITE_OK if successful, or SQLITE_NOMEM if an
+** error occurs.
+*/
+static int fts5SentenceFinderAdd(Fts5SFinder *p, int iAdd){
+  if( p->nFirstAlloc==p->nFirst ){
+    int nNew = p->nFirstAlloc ? p->nFirstAlloc*2 : 64;
+    int *aNew;
+
+    aNew = (int*)sqlite3_realloc(p->aFirst, nNew*sizeof(int));
+    if( aNew==0 ) return SQLITE_NOMEM;
+    p->aFirst = aNew;
+    p->nFirstAlloc = nNew;
+  }
+  p->aFirst[p->nFirst++] = iAdd;
+  return SQLITE_OK;
+}
+
+/*
+** This function is an xTokenize() callback used by the auxiliary snippet()
+** function. Its job is to identify tokens that are the first in a sentence.
+** For each such token, an entry is added to the SFinder.aFirst[] array.
+*/
+static int fts5SentenceFinderCb(
+  void *pContext,                 /* Pointer to HighlightContext object */
+  int tflags,                     /* Mask of FTS5_TOKEN_* flags */
+  const char *pToken,             /* Buffer containing token */
+  int nToken,                     /* Size of token in bytes */
+  int iStartOff,                  /* Start offset of token */
+  int iEndOff                     /* End offset of token */
+){
+  int rc = SQLITE_OK;
+
+  if( (tflags & FTS5_TOKEN_COLOCATED)==0 ){
+    Fts5SFinder *p = (Fts5SFinder*)pContext;
+    if( p->iPos>0 ){
+      int i;
+      char c = 0;
+      for(i=iStartOff-1; i>=0; i--){
+        c = p->zDoc[i];
+        if( c!=' ' && c!='\t' && c!='\n' && c!='\r' ) break;
+      }
+      if( i!=iStartOff-1 && (c=='.' || c==':') ){
+        rc = fts5SentenceFinderAdd(p, p->iPos);
+      }
+    }else{
+      rc = fts5SentenceFinderAdd(p, 0);
+    }
+    p->iPos++;
+  }
+  return rc;
+}
+
+static int fts5SnippetScore(
+  const Fts5ExtensionApi *pApi,   /* API offered by current FTS version */
+  Fts5Context *pFts,              /* First arg to pass to pApi functions */
+  int nDocsize,                   /* Size of column in tokens */
+  unsigned char *aSeen,           /* Array with one element per query phrase */
+  int iCol,                       /* Column to score */
+  int iPos,                       /* Starting offset to score */
+  int nToken,                     /* Max tokens per snippet */
+  int *pnScore,                   /* OUT: Score */
+  int *piPos                      /* OUT: Adjusted offset */
+){
+  int rc;
+  int i;
+  int ip = 0;
+  int ic = 0;
+  int iOff = 0;
+  int iFirst = -1;
+  int nInst;
+  int nScore = 0;
+  int iLast = 0;
+
+  rc = pApi->xInstCount(pFts, &nInst);
+  for(i=0; i<nInst && rc==SQLITE_OK; i++){
+    rc = pApi->xInst(pFts, i, &ip, &ic, &iOff);
+    if( rc==SQLITE_OK && ic==iCol && iOff>=iPos && iOff<(iPos+nToken) ){
+      nScore += (aSeen[ip] ? 1 : 1000);
+      aSeen[ip] = 1;
+      if( iFirst<0 ) iFirst = iOff;
+      iLast = iOff + pApi->xPhraseSize(pFts, ip);
+    }
+  }
+
+  *pnScore = nScore;
+  if( piPos ){
+    int iAdj = iFirst - (nToken - (iLast-iFirst)) / 2;
+    if( (iAdj+nToken)>nDocsize ) iAdj = nDocsize - nToken;
+    if( iAdj<0 ) iAdj = 0;
+    *piPos = iAdj;
+  }
+
+  return rc;
+}
 
 /*
 ** Implementation of snippet() function.
 */
 static void fts5SnippetFunction(
@@ -265,86 +374,110 @@
   int i;                          /* Used to iterate through instances */
   int nPhrase;                    /* Number of phrases in query */
   unsigned char *aSeen;           /* Array of "seen instance" flags */
   int iBestCol;                   /* Column containing best snippet */
   int iBestStart = 0;             /* First token of best snippet */
-  int iBestLast;                  /* Last token of best snippet */
   int nBestScore = 0;             /* Score of best snippet */
   int nColSize = 0;               /* Total size of iBestCol in tokens */
+  Fts5SFinder sFinder;            /* Used to find the beginnings of sentences */
+  int nCol;
 
   if( nVal!=5 ){
     const char *zErr = "wrong number of arguments to function snippet()";
     sqlite3_result_error(pCtx, zErr, -1);
     return;
   }
 
+  nCol = pApi->xColumnCount(pFts);
   memset(&ctx, 0, sizeof(HighlightContext));
   iCol = sqlite3_value_int(apVal[0]);
   ctx.zOpen = (const char*)sqlite3_value_text(apVal[1]);
   ctx.zClose = (const char*)sqlite3_value_text(apVal[2]);
   zEllips = (const char*)sqlite3_value_text(apVal[3]);
   nToken = sqlite3_value_int(apVal[4]);
-  iBestLast = nToken-1;
 
   iBestCol = (iCol>=0 ? iCol : 0);
   nPhrase = pApi->xPhraseCount(pFts);
   aSeen = sqlite3_malloc(nPhrase);
   if( aSeen==0 ){
     rc = SQLITE_NOMEM;
   }
-
-  if( rc==SQLITE_OK ){
-    rc = pApi->xInstCount(pFts, &nInst);
-  }
-  for(i=0; rc==SQLITE_OK && i<nInst; i++){
-    int ip, iSnippetCol, iStart;
-    memset(aSeen, 0, nPhrase);
-    rc = pApi->xInst(pFts, i, &ip, &iSnippetCol, &iStart);
-    if( rc==SQLITE_OK && (iCol<0 || iSnippetCol==iCol) ){
-      int nScore = 1000;
-      int iLast = iStart - 1 + pApi->xPhraseSize(pFts, ip);
-      int j;
-      aSeen[ip] = 1;
-
-      for(j=i+1; rc==SQLITE_OK && j<nInst; j++){
-        int ic; int io; int iFinal;
-        rc = pApi->xInst(pFts, j, &ip, &ic, &io);
-        iFinal = io + pApi->xPhraseSize(pFts, ip) - 1;
-        if( rc==SQLITE_OK && ic==iSnippetCol && iLast<iStart+nToken ){
-          nScore += aSeen[ip] ? 1000 : 1;
-          aSeen[ip] = 1;
-          if( iFinal>iLast ) iLast = iFinal;
-        }
-      }
-
-      if( rc==SQLITE_OK && nScore>nBestScore ){
-        iBestCol = iSnippetCol;
-        iBestStart = iStart;
-        iBestLast = iLast;
-        nBestScore = nScore;
-      }
-    }
-  }
-
-  if( rc==SQLITE_OK ){
-    rc = pApi->xColumnSize(pFts, iBestCol, &nColSize);
-  }
-  if( rc==SQLITE_OK ){
-    rc = pApi->xColumnText(pFts, iBestCol, &ctx.zIn, &ctx.nIn);
-  }
-  if( ctx.zIn ){
-    if( rc==SQLITE_OK ){
-      rc = fts5CInstIterInit(pApi, pFts, iBestCol, &ctx.iter);
-    }
-
-    if( (iBestStart+nToken-1)>iBestLast ){
-      iBestStart -= (iBestStart+nToken-1-iBestLast) / 2;
-    }
-    if( iBestStart+nToken>nColSize ){
-      iBestStart = nColSize - nToken;
-    }
-    if( iBestStart<0 ) iBestStart = 0;
+  if( rc==SQLITE_OK ){
+    rc = pApi->xInstCount(pFts, &nInst);
+  }
+
+  memset(&sFinder, 0, sizeof(Fts5SFinder));
+  for(i=0; i<nCol; i++){
+    if( iCol<0 || iCol==i ){
+      int nDoc;
+      int nDocsize;
+      int ii;
+      sFinder.iPos = 0;
+      sFinder.nFirst = 0;
+      rc = pApi->xColumnText(pFts, i, &sFinder.zDoc, &nDoc);
+      if( rc!=SQLITE_OK ) break;
+      rc = pApi->xTokenize(pFts, 
+          sFinder.zDoc, nDoc, (void*)&sFinder,fts5SentenceFinderCb
+      );
+      if( rc!=SQLITE_OK ) break;
+      rc = pApi->xColumnSize(pFts, i, &nDocsize);
+      if( rc!=SQLITE_OK ) break;
+
+      for(ii=0; rc==SQLITE_OK && ii<nInst; ii++){
+        int ip, ic, io;
+        int iAdj;
+        int nScore;
+        int jj;
+
+        rc = pApi->xInst(pFts, ii, &ip, &ic, &io);
+        if( ic!=i || rc!=SQLITE_OK ) continue;
+        memset(aSeen, 0, nPhrase);
+        rc = fts5SnippetScore(pApi, pFts, nDocsize, aSeen, i,
+            io, nToken, &nScore, &iAdj
+        );
+        if( rc==SQLITE_OK && nScore>nBestScore ){
+          nBestScore = nScore;
+          iBestCol = i;
+          iBestStart = iAdj;
+          nColSize = nDocsize;
+        }
+
+        if( rc==SQLITE_OK && sFinder.nFirst && nDocsize>nToken ){
+          for(jj=0; jj<(sFinder.nFirst-1); jj++){
+            if( sFinder.aFirst[jj+1]>io ) break;
+          }
+
+          if( sFinder.aFirst[jj]<io ){
+            int nScore;
+            memset(aSeen, 0, nPhrase);
+            rc = fts5SnippetScore(pApi, pFts, nDocsize, aSeen, i, 
+              sFinder.aFirst[jj], nToken, &nScore, 0
+            );
+
+            nScore += (sFinder.aFirst[jj]==0 ? 120 : 100);
+            if( rc==SQLITE_OK && nScore>nBestScore ){
+              nBestScore = nScore;
+              iBestCol = i;
+              iBestStart = sFinder.aFirst[jj];
+              nColSize = nDocsize;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = pApi->xColumnText(pFts, iBestCol, &ctx.zIn, &ctx.nIn);
+  }
+  if( rc==SQLITE_OK && nColSize==0 ){
+    rc = pApi->xColumnSize(pFts, iBestCol, &nColSize);
+  }
+  if( ctx.zIn ){
+    if( rc==SQLITE_OK ){
+      rc = fts5CInstIterInit(pApi, pFts, iBestCol, &ctx.iter);
+    }
 
     ctx.iRangeStart = iBestStart;
     ctx.iRangeEnd = iBestStart + nToken - 1;
 
     if( iBestStart>0 ){
@@ -363,19 +496,19 @@
     if( ctx.iRangeEnd>=(nColSize-1) ){
       fts5HighlightAppend(&rc, &ctx, &ctx.zIn[ctx.iOff], ctx.nIn - ctx.iOff);
     }else{
       fts5HighlightAppend(&rc, &ctx, zEllips, -1);
     }
-
-    if( rc==SQLITE_OK ){
-      sqlite3_result_text(pCtx, (const char*)ctx.zOut, -1, SQLITE_TRANSIENT);
-    }else{
-      sqlite3_result_error_code(pCtx, rc);
-    }
-    sqlite3_free(ctx.zOut);
-  }
+  }
+  if( rc==SQLITE_OK ){
+    sqlite3_result_text(pCtx, (const char*)ctx.zOut, -1, SQLITE_TRANSIENT);
+  }else{
+    sqlite3_result_error_code(pCtx, rc);
+  }
+  sqlite3_free(ctx.zOut);
   sqlite3_free(aSeen);
+  sqlite3_free(sFinder.aFirst);
 }
 
 /************************************************************************/
 
 /*

Index: ext/fts5/test/fts5af.test
==================================================================
--- ext/fts5/test/fts5af.test
+++ ext/fts5/test/fts5af.test
@@ -70,49 +70,60 @@
 
   2.1 {X o o o o o o o} {[X] o o o o o o...}
   2.2 {o X o o o o o o} {o [X] o o o o o...}
   2.3 {o o X o o o o o} {o o [X] o o o o...}
   2.4 {o o o X o o o o} {o o o [X] o o o...}
-  2.5 {o o o o X o o o} {...o o o [X] o o o}
-  2.6 {o o o o o X o o} {...o o o o [X] o o}
-  2.7 {o o o o o o X o} {...o o o o o [X] o}
+  2.5 {o o o o X o o o} {o o o o [X] o o...}
+  2.6 {o o o o o X o o} {o o o o o [X] o...}
+  2.7 {o o o o o o X o} {o o o o o o [X]...}
   2.8 {o o o o o o o X} {...o o o o o o [X]}
+
+  2.9  {o o o o o o o X o}       {...o o o o o [X] o}
+  2.10 {o o o o o o o X o o}     {...o o o o [X] o o}
+  2.11 {o o o o o o o X o o o}   {...o o o [X] o o o}
+  2.12 {o o o o o o o X o o o o} {...o o o [X] o o o...}
+
 
   3.1 {X o o o o o o o o} {[X] o o o o o o...}
   3.2 {o X o o o o o o o} {o [X] o o o o o...}
   3.3 {o o X o o o o o o} {o o [X] o o o o...}
   3.4 {o o o X o o o o o} {o o o [X] o o o...}
-  3.5 {o o o o X o o o o} {...o o o [X] o o o...}
-  3.6 {o o o o o X o o o} {...o o o [X] o o o}
-  3.7 {o o o o o o X o o} {...o o o o [X] o o}
-  3.8 {o o o o o o o X o} {...o o o o o [X] o}
-  3.9 {o o o o o o o o X} {...o o o o o o [X]}
+
+  3.5 {o o o o o o o X o o o o} {...o o o [X] o o o...}
+  3.6 {o o o o o o o o X o o o} {...o o o [X] o o o}
+  3.7 {o o o o o o o o o X o o} {...o o o o [X] o o}
+  3.8 {o o o o o o o o o o X o} {...o o o o o [X] o}
+  3.9 {o o o o o o o o o o o X} {...o o o o o o [X]}
 
   4.1 {X o o o o o X o o} {[X] o o o o o [X]...}
-  4.2 {o X o o o o o X o} {...[X] o o o o o [X]...}
-  4.3 {o o X o o o o o X} {...[X] o o o o o [X]}
+  4.2 {o o o o o o o X o o o o o X o} {...[X] o o o o o [X]...}
+  4.3 {o o o o o o o o X o o o o o X} {...[X] o o o o o [X]}
 
   5.1 {X o o o o X o o o} {[X] o o o o [X] o...}
-  5.2 {o X o o o o X o o} {...[X] o o o o [X] o...}
-  5.3 {o o X o o o o X o} {...[X] o o o o [X] o}
-  5.4 {o o o X o o o o X} {...o [X] o o o o [X]}
+  5.2 {o o o o o o o X o o o o X o o} {...[X] o o o o [X] o...}
+  5.3 {o o o o o o o o X o o o o X o} {...[X] o o o o [X] o}
+  5.4 {o o o o o o o o o X o o o o X} {...o [X] o o o o [X]}
 
   6.1 {X o o o X o o o} {[X] o o o [X] o o...}
   6.2 {o X o o o X o o o} {o [X] o o o [X] o...}
-  6.3 {o o X o o o X o o} {...o [X] o o o [X] o...}
-  6.4 {o o o X o o o X o} {...o [X] o o o [X] o}
-  6.5 {o o o o X o o o X} {...o o [X] o o o [X]}
+  6.3 {o o o o o o o X o o o X o o} {...o [X] o o o [X] o...}
+  6.4 {o o o o o o o o X o o o X o} {...o [X] o o o [X] o}
+  6.5 {o o o o o o o o o X o o o X} {...o o [X] o o o [X]}
 
   7.1 {X o o X o o o o o} {[X] o o [X] o o o...}
   7.2 {o X o o X o o o o} {o [X] o o [X] o o...}
-  7.3 {o o X o o X o o o} {...o [X] o o [X] o o...}
-  7.4 {o o o X o o X o o} {...o [X] o o [X] o o}
-  7.5 {o o o o X o o X o} {...o o [X] o o [X] o}
-  7.6 {o o o o o X o o X} {...o o o [X] o o [X]}
+  7.3 {o o o o o o o X o o X o o o} {...o [X] o o [X] o o...}
+  7.4 {o o o o o o o o X o o X o o} {...o [X] o o [X] o o}
+  7.5 {o o o o o o o o o X o o X o} {...o o [X] o o [X] o}
+  7.6 {o o o o o o o o o o X o o X} {...o o o [X] o o [X]}
 
-  8.1 {o o o o X o o o o o o o o o o o o o o o o o o o o o X X X o o o}
+  8.1 {o o o o o o o o o X o o o o o o o o o o o o o o o o X X X o o o}
       {...o o [X] [X] [X] o o...}
+  8.2 {o o o o o o o. o o X o o o o o o o o o o o o o o o o X X X o o o} 
+      {...o o [X] o o o o...}
+  8.3 {o o o o X o o o o o o o o o o o o o o o o o o o o o X X X o o o} 
+      {o o o o [X] o o...}
 } {
   do_snippet_test 1.$tn $doc X $res
 }
 
 if {[detail_is_full]} {
@@ -125,27 +136,46 @@
     1.6 {o o o o o X Y} {o o o o o [X Y]}
 
     2.1 {X Y o o o o o o} {[X Y] o o o o o...}
     2.2 {o X Y o o o o o} {o [X Y] o o o o...}
     2.3 {o o X Y o o o o} {o o [X Y] o o o...}
-    2.4 {o o o X Y o o o} {...o o [X Y] o o o}
-    2.5 {o o o o X Y o o} {...o o o [X Y] o o}
-    2.6 {o o o o o X Y o} {...o o o o [X Y] o}
-    2.7 {o o o o o o X Y} {...o o o o o [X Y]}
+    2.4 {o o o o o o o X Y o o o} {...o o [X Y] o o o}
+    2.5 {o o o o o o o o X Y o o} {...o o o [X Y] o o}
+    2.6 {o o o o o o o o o X Y o} {...o o o o [X Y] o}
+    2.7 {o o o o o o o o o o X Y} {...o o o o o [X Y]}
 
     3.1 {X Y o o o o o o o} {[X Y] o o o o o...}
     3.2 {o X Y o o o o o o} {o [X Y] o o o o...}
     3.3 {o o X Y o o o o o} {o o [X Y] o o o...}
-    3.4 {o o o X Y o o o o} {...o o [X Y] o o o...}
-    3.5 {o o o o X Y o o o} {...o o [X Y] o o o}
-    3.6 {o o o o o X Y o o} {...o o o [X Y] o o}
-    3.7 {o o o o o o X Y o} {...o o o o [X Y] o}
-    3.8 {o o o o o o o X Y} {...o o o o o [X Y]}
+    3.4 {o o o o o o o X Y o o o o} {...o o [X Y] o o o...}
+    3.5 {o o o o o o o o X Y o o o} {...o o [X Y] o o o}
+    3.6 {o o o o o o o o o X Y o o} {...o o o [X Y] o o}
+    3.7 {o o o o o o o o o o X Y o} {...o o o o [X Y] o}
+    3.8 {o o o o o o o o o o o X Y} {...o o o o o [X Y]}
   } {
     do_snippet_test 2.$tn $doc "X + Y" $res
   }
 }
 
+do_execsql_test 4.0 {
+  CREATE VIRTUAL TABLE x1 USING fts5(a, b);
+  INSERT INTO x1 VALUES('xyz', '1 2 3 4 5 6 7 8 9 10 11 12 13');
+  SELECT snippet(x1, 1, '[', ']', '...', 5) FROM x1('xyz');
+} {
+  {1 2 3 4 5...}
+}
+
+do_execsql_test 5.0 {
+  CREATE VIRTUAL TABLE p1 USING fts5(a, b);
+  INSERT INTO p1 VALUES(
+    'x a a a a a a a a a a',
+    'a a a a a a a a a a a a a a a a a a a x'
+  );
+}
+do_execsql_test 5.1 {
+  SELECT snippet(p1, 0, '[', ']', '...', 6) FROM p1('x');
+} {{[x] a a a a a...}}
+
 } ;# foreach_detail_mode 
 
 finish_test
 

Index: ext/fts5/test/fts5unicode2.test
==================================================================
--- ext/fts5/test/fts5unicode2.test
+++ ext/fts5/test/fts5unicode2.test
@@ -158,16 +158,16 @@
   3 "ROW" {
      ...returns the value of y on the same [row] that contains 
      the maximum x value.
   }
   4 "rollback" {
-     ...[ROLLBACK]. Instead, the pending statement
-     will return SQLITE_ABORT upon next access after the [ROLLBACK].
+     Pending statements no longer block [ROLLBACK]. Instead, the pending
+     statement will return SQLITE_ABORT upon...
   }
   5 "rOllback" {
-     ...[ROLLBACK]. Instead, the pending statement
-     will return SQLITE_ABORT upon next access after the [ROLLBACK].
+     Pending statements no longer block [ROLLBACK]. Instead, the pending
+     statement will return SQLITE_ABORT upon...
   }
   6 "lang*" {
      Added support for the FTS4 [languageid] option.
   }
 } {

Index: src/main.c
==================================================================
--- src/main.c
+++ src/main.c
@@ -2946,15 +2946,24 @@
   ** database schema yet. This is delayed until the first time the database
   ** is accessed.
   */
   sqlite3Error(db, SQLITE_OK);
   sqlite3RegisterPerConnectionBuiltinFunctions(db);
+  rc = sqlite3_errcode(db);
+
+#ifdef SQLITE_ENABLE_FTS5
+  /* Register any built-in FTS5 module before loading the automatic
+  ** extensions. This allows automatic extensions to register FTS5 
+  ** tokenizers and auxiliary functions.  */
+  if( !db->mallocFailed && rc==SQLITE_OK ){
+    rc = sqlite3Fts5Init(db);
+  }
+#endif
 
   /* Load automatic extensions - extensions that have been registered
   ** using the sqlite3_automatic_extension() API.
   */
-  rc = sqlite3_errcode(db);
   if( rc==SQLITE_OK ){
     sqlite3AutoLoadExtensions(db);
     rc = sqlite3_errcode(db);
     if( rc!=SQLITE_OK ){
       goto opendb_out;
@@ -2977,16 +2986,10 @@
 
 #ifdef SQLITE_ENABLE_FTS3 /* automatically defined by SQLITE_ENABLE_FTS4 */
   if( !db->mallocFailed && rc==SQLITE_OK ){
     rc = sqlite3Fts3Init(db);
   }
-#endif
-
-#ifdef SQLITE_ENABLE_FTS5
-  if( !db->mallocFailed && rc==SQLITE_OK ){
-    rc = sqlite3Fts5Init(db);
-  }
 #endif
 
 #ifdef SQLITE_ENABLE_ICU
   if( !db->mallocFailed && rc==SQLITE_OK ){
     rc = sqlite3IcuInit(db);