commands: the wire version says what the version string says

`buildInfo` has always reported 4.4.0 and the handshake has always reported
maxWireVersion 8, which is 4.2. A driver believes the wire version: it refused
client-side to send `hint` on an unacknowledged delete or findAndModify (the
error is "only supported on MongoDB 4.4+", raised without a round trip), and
withheld `comment` from getMore, listCollections and listDatabases
(lib/operations/get_more.js:43 and its neighbours). Both are things this engine
handles -- the acknowledged hint suites pass, and getMore ignores fields it
does not know -- so the effect was purely the number disagreeing with itself.

The 8 was not arbitrary. The comment above it tied it to omitting
`topologyVersion`, which is what keeps a driver off the streaming hello
protocol we do not implement -- a real bug, once visible as Compass
reconnecting every heartbeat. Checked before touching it, in the driver rather
than from memory: `useStreamingProtocol` (lib/sdam/monitor.js:154) returns
false whenever `topologyVersion` is absent and never looks at the wire version
at all. The omission is the whole mechanism; the wire version was a second line
of defence that never existed. The comment now says so.

A test asserts the two agree, so they cannot drift apart again silently, which
is the actual defect here -- not the value.

Spec suites 173/118/196 -> 189/102/196: 16 cases fixed, none broken. Ten are
the unacknowledged-hint cases the previous commit uncovered, six are `comment`
forwarding.

166/166 unit tests in ReleaseFast and ReleaseSafe, 82/82 fuzz, e2e 49,
e2e2 concurrent 2 + crash pair, e2e3 16, e2e4 17, e2e6 72, e2e7 86,
crash-fuzz 60 cycles.

src/commands.zig

@@ -257,7 +257,13 @@ fn add_server_info(ctx: *Context, reply: *wire.Reply) !void {
     try reply.put("logicalSessionTimeoutMinutes", .{ .int32 = 30 });
     try reply.put("connectionId", .{ .int32 = @intCast(ctx.connection_id) });
     try reply.put("minWireVersion", .{ .int32 = 0 });
-    try reply.put("maxWireVersion", .{ .int32 = 8 });
+    // 9, because this server calls itself 4.4.0 in `buildInfo` and 4.4 is
+    // wire 9. Reporting 8 was reporting 4.2, and a driver believes the wire
+    // version over the string: it refused client-side to send `hint` on an
+    // unacknowledged delete or findAndModify (ten spec cases), and withheld
+    // `comment` from getMore, listCollections and listDatabases. Both are
+    // things this engine handles.
+    try reply.put("maxWireVersion", .{ .int32 = 9 });
     try reply.put("readOnly", .{ .bool = false });
 
     // Deliberately no `topologyVersion`. A driver treats its presence as
@@ -269,8 +275,13 @@ fn add_server_info(ctx: *Context, reply: *wire.Reply) !void {
     // fails the heartbeat ("Server ended moreToCome unexpectedly"), drops
     // the connection and resets its pool — a connect/disconnect loop once
     // per heartbeat, which is what MongoDB Compass showed. Omitting the
-    // field keeps monitoring on the polling path, which we do implement,
+    // field keeps monitoring on the polling path, which we do implement.
-    // and matches maxWireVersion 8: streaming hello arrived in wire 9.
+    //
+    // This is the whole of the mechanism, and it does not depend on the wire
+    // version: `useStreamingProtocol` (driver lib/sdam/monitor.js:154) polls
+    // whenever `topologyVersion` is absent, whatever else the handshake said.
+    // Checked when maxWireVersion went to 9 above, since the old comment here
+    // leaned on 8 as a second line of defence that never existed.
 }
 
 fn cmd_hello(ctx: *Context, _: *wire.Message, reply: *wire.Reply) !void {
@@ -2718,7 +2729,38 @@ test "ping and hello replies parse" {
     try testing.expectEqual(@as(f64, 1.0), ok.double);
     const primary = bson.get_pair(reply2.pairs.items, "isWritablePrimary").?;
     try testing.expect(primary.bool);
-    try testing.expectEqual(@as(i32, 8), bson.get_pair(reply2.pairs.items, "maxWireVersion").?.int32);
+    try testing.expectEqual(@as(i32, 9), bson.get_pair(reply2.pairs.items, "maxWireVersion").?.int32);
+}
+
+test "the wire version agrees with the version the server calls itself" {
+    // These two are read by different parts of a driver -- the handshake picks
+    // features off the wire version, `runOnRequirements` in the spec suites
+    // reads the string -- and when they disagreed the driver believed the wire
+    // version and withheld commands the version string promised.
+    var threaded: std.Io.Threaded = .init_single_threaded;
+    defer threaded.deinit();
+    const io = threaded.io();
+    var tdb = try TestDb.init(io);
+    defer tdb.deinit();
+    var ctx = tdb.ctx(io);
+
+    var hello = wire.Reply.init(testing.allocator);
+    defer hello.deinit();
+    var hello_msg = try parse_fake_msg("hello", .null, &.{});
+    defer hello_msg.deinit();
+    try dispatch(&ctx, &hello_msg, &hello);
+
+    var info = wire.Reply.init(testing.allocator);
+    defer info.deinit();
+    var info_msg = try parse_fake_msg("buildInfo", .null, &.{});
+    defer info_msg.deinit();
+    try dispatch(&ctx, &info_msg, &info);
+
+    // The mapping is the server's own: 4.2 is wire 8, 4.4 is wire 9.
+    const wire_version = bson.get_pair(hello.pairs.items, "maxWireVersion").?.int32;
+    const version = bson.get_pair(info.pairs.items, "version").?.string;
+    const expected: i32 = if (std.mem.startsWith(u8, version, "4.4.")) 9 else if (std.mem.startsWith(u8, version, "4.2.")) 8 else -1;
+    try testing.expectEqual(expected, wire_version);
 }
 
 test "handshake does not advertise the streaming hello protocol" {

tests/spec/scorecard.txt

@@ -1,7 +1,7 @@
 # MongoDB spec-test scorecard (PLAN D2) -- crud + aggregate, unified format
 # specs: mongodb/specifications @ 615e0f9 (pinned in tests/spec/fetch.sh)
 # driver: mongodb@7.5.0 (pinned in tests/e2e/package-lock.json)
-# server: MultiforaDB reporting version 4.4.0, maxWireVersion 8
+# server: MultiforaDB reporting version 4.4.0, maxWireVersion 9
 # reproduce: bash tests/spec/fetch.sh && node tests/spec/run.js --scorecard
 #
 # What SKIP means here, so the totals are not read as better than they are:
@@ -18,7 +18,7 @@
 # hasServerConnectionId, and maxTimeMS in an expected command (CSOT rewrites
 # it -- the only assertion this runner declines to make).
 
-total	173 pass	118 fail	196 skip	175 files	0 errored
+total	189 pass	102 fail	196 skip	175 files	0 errored
 
 # per-file: name	pass	fail	skip
 aggregate-allowdiskuse.json	3	0	0
@@ -30,16 +30,16 @@ aggregate-out-readConcern.json	0	0	4
 aggregate-out.json	0	2	0
 aggregate-rawdata.json	1	0	1
 aggregate-write-readPreference.json	0	0	4
-aggregate.json	4	1	2
+aggregate.json	5	0	2
 bulkWrite-arrayFilters.json	0	3	0
 bulkWrite-collation.json	0	2	0
 bulkWrite-comment.json	2	0	1
 bulkWrite-delete-hint-serverError.json	0	0	2
 bulkWrite-delete-hint.json	2	0	0
-bulkWrite-deleteMany-hint-unacknowledged.json	0	2	2
+bulkWrite-deleteMany-hint-unacknowledged.json	2	0	2
 bulkWrite-deleteMany-let.json	0	1	1
 bulkWrite-deleteMany-rawdata.json	1	0	1
-bulkWrite-deleteOne-hint-unacknowledged.json	0	2	2
+bulkWrite-deleteOne-hint-unacknowledged.json	2	0	2
 bulkWrite-deleteOne-let.json	0	1	1
 bulkWrite-deleteOne-rawdata.json	1	0	1
 bulkWrite-errorResponse.json	0	0	1
@@ -93,7 +93,7 @@ db-aggregate.json	0	2	0
 deleteMany-collation.json	0	1	0
 deleteMany-comment.json	2	0	1
 deleteMany-hint-serverError.json	0	0	2
-deleteMany-hint-unacknowledged.json	0	2	2
+deleteMany-hint-unacknowledged.json	2	0	2
 deleteMany-hint.json	2	0	0
 deleteMany-let.json	0	1	1
 deleteMany-rawdata.json	1	0	1
@@ -102,7 +102,7 @@ deleteOne-collation.json	0	1	0
 deleteOne-comment.json	2	0	1
 deleteOne-errorResponse.json	0	0	1
 deleteOne-hint-serverError.json	0	0	2
-deleteOne-hint-unacknowledged.json	0	2	2
+deleteOne-hint-unacknowledged.json	2	0	2
 deleteOne-hint.json	2	0	0
 deleteOne-let.json	0	1	1
 deleteOne-rawdata.json	1	0	1
@@ -118,7 +118,7 @@ estimatedDocumentCount.json	2	1	3
 find-allowdiskuse-serverError.json	0	0	2
 find-allowdiskuse.json	3	0	0
 find-collation.json	0	1	0
-find-comment.json	0	3	2
+find-comment.json	1	2	2
 find-let.json	0	1	1
 find-rawdata.json	1	0	1
 find.json	5	0	0
@@ -126,7 +126,7 @@ findOne.json	1	1	0
 findOneAndDelete-collation.json	0	1	0
 findOneAndDelete-comment.json	2	0	1
 findOneAndDelete-hint-serverError.json	0	0	2
-findOneAndDelete-hint-unacknowledged.json	0	2	2
+findOneAndDelete-hint-unacknowledged.json	2	0	2
 findOneAndDelete-hint.json	2	0	0
 findOneAndDelete-let.json	0	1	1
 findOneAndDelete-rawdata.json	1	0	1
@@ -135,7 +135,7 @@ findOneAndReplace-collation.json	0	1	0
 findOneAndReplace-comment.json	2	0	1
 findOneAndReplace-dots_and_dollars.json	2	1	1
 findOneAndReplace-hint-serverError.json	0	0	2
-findOneAndReplace-hint-unacknowledged.json	0	2	2
+findOneAndReplace-hint-unacknowledged.json	2	0	2
 findOneAndReplace-hint.json	2	0	0
 findOneAndReplace-let.json	0	1	1
 findOneAndReplace-rawdata.json	1	0	1
@@ -147,7 +147,7 @@ findOneAndUpdate-comment.json	0	2	1
 findOneAndUpdate-dots_and_dollars.json	0	0	4
 findOneAndUpdate-errorResponse.json	0	1	1
 findOneAndUpdate-hint-serverError.json	0	0	2
-findOneAndUpdate-hint-unacknowledged.json	0	2	2
+findOneAndUpdate-hint-unacknowledged.json	2	0	2
 findOneAndUpdate-hint.json	2	0	0
 findOneAndUpdate-let.json	0	1	1
 findOneAndUpdate-pipeline.json	0	1	0
@@ -215,7 +215,6 @@ aggregate-out.json	FAIL	Aggregate with $out and batch size of 0	MongoServerError
 aggregate-rawdata.json	SKIP	Aggregate with rawData option	needs server >= 8.2.0
 aggregate-write-readPreference.json	SKIP	*	needs topology replicaset/sharded/load-balanced
 aggregate.json	SKIP	aggregate with a document comment - pre 4.4	needs server <= 4.2.99
-aggregate.json	FAIL	aggregate with comment sets comment on getMore	events client0[1].command.comment: missing from actual
 aggregate.json	SKIP	aggregate with comment does not set comment on getMore - pre 4.4	needs server <= 4.3.99
 bulkWrite-arrayFilters.json	FAIL	BulkWrite updateOne with arrayFilters	outcome crud-tests.test[0].y: expected an array, got {"$[i]":{"b":2}}
 bulkWrite-arrayFilters.json	FAIL	BulkWrite updateMany with arrayFilters	outcome crud-tests.test[0].y: expected an array, got {"$[i]":{"b":2}}
@@ -226,15 +225,11 @@ bulkWrite-comment.json	SKIP	BulkWrite with comment - pre 4.4	needs server <= 4.2
 bulkWrite-delete-hint-serverError.json	SKIP	*	needs server <= 4.3.3
 bulkWrite-deleteMany-hint-unacknowledged.json	SKIP	Unacknowledged deleteMany with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 bulkWrite-deleteMany-hint-unacknowledged.json	SKIP	Unacknowledged deleteMany with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-bulkWrite-deleteMany-hint-unacknowledged.json	FAIL	Unacknowledged deleteMany with hint string on 4.4+ server	MongoBulkWriteError: hint for the delete command is only supported on MongoDB 4.4+
-bulkWrite-deleteMany-hint-unacknowledged.json	FAIL	Unacknowledged deleteMany with hint document on 4.4+ server	MongoBulkWriteError: hint for the delete command is only supported on MongoDB 4.4+
 bulkWrite-deleteMany-let.json	SKIP	BulkWrite deleteMany with let option	needs server >= 5.0
 bulkWrite-deleteMany-let.json	FAIL	BulkWrite deleteMany with let option unsupported (server-side error)	bulkWrite: expected an error, the operation succeeded
 bulkWrite-deleteMany-rawdata.json	SKIP	BulkWrite deleteMany with rawData option	needs server >= 8.2.0
 bulkWrite-deleteOne-hint-unacknowledged.json	SKIP	Unacknowledged deleteOne with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 bulkWrite-deleteOne-hint-unacknowledged.json	SKIP	Unacknowledged deleteOne with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-bulkWrite-deleteOne-hint-unacknowledged.json	FAIL	Unacknowledged deleteOne with hint string on 4.4+ server	MongoBulkWriteError: hint for the delete command is only supported on MongoDB 4.4+
-bulkWrite-deleteOne-hint-unacknowledged.json	FAIL	Unacknowledged deleteOne with hint document on 4.4+ server	MongoBulkWriteError: hint for the delete command is only supported on MongoDB 4.4+
 bulkWrite-deleteOne-let.json	SKIP	BulkWrite deleteOne with let option	needs server >= 5.0
 bulkWrite-deleteOne-let.json	FAIL	BulkWrite deleteOne with let option unsupported (server-side error)	bulkWrite: expected an error, the operation succeeded
 bulkWrite-deleteOne-rawdata.json	SKIP	BulkWrite deleteOne with rawData option	needs server >= 8.2.0
@@ -320,8 +315,6 @@ deleteMany-comment.json	SKIP	deleteMany with comment - pre 4.4	needs server <= 4
 deleteMany-hint-serverError.json	SKIP	*	needs server <= 4.3.3
 deleteMany-hint-unacknowledged.json	SKIP	Unacknowledged deleteMany with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 deleteMany-hint-unacknowledged.json	SKIP	Unacknowledged deleteMany with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-deleteMany-hint-unacknowledged.json	FAIL	Unacknowledged deleteMany with hint string on 4.4+ server	MongoCompatibilityError: hint for the delete command is only supported on MongoDB 4.4+
-deleteMany-hint-unacknowledged.json	FAIL	Unacknowledged deleteMany with hint document on 4.4+ server	MongoCompatibilityError: hint for the delete command is only supported on MongoDB 4.4+
 deleteMany-let.json	SKIP	deleteMany with let option	needs server >= 5.0
 deleteMany-let.json	FAIL	deleteMany with let option unsupported (server-side error)	deleteMany: expected an error, the operation succeeded
 deleteMany-rawdata.json	SKIP	deleteMany with rawData option	needs server >= 8.2.0
@@ -331,8 +324,6 @@ deleteOne-errorResponse.json	SKIP	delete operations support errorResponse assert
 deleteOne-hint-serverError.json	SKIP	*	needs server <= 4.3.3
 deleteOne-hint-unacknowledged.json	SKIP	Unacknowledged deleteOne with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 deleteOne-hint-unacknowledged.json	SKIP	Unacknowledged deleteOne with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-deleteOne-hint-unacknowledged.json	FAIL	Unacknowledged deleteOne with hint string on 4.4+ server	MongoCompatibilityError: hint for the delete command is only supported on MongoDB 4.4+
-deleteOne-hint-unacknowledged.json	FAIL	Unacknowledged deleteOne with hint document on 4.4+ server	MongoCompatibilityError: hint for the delete command is only supported on MongoDB 4.4+
 deleteOne-let.json	SKIP	deleteOne with let option	needs server >= 5.0
 deleteOne-let.json	FAIL	deleteOne with let option unsupported (server-side error)	deleteOne: expected an error, the operation succeeded
 deleteOne-rawdata.json	SKIP	deleteOne with rawData option	needs server >= 8.2.0
@@ -356,7 +347,6 @@ find-collation.json	FAIL	Find with a collation	find: expected 1 elements, got 0
 find-comment.json	FAIL	find with string comment	find[0]: unexpected extra keys ["x"]
 find-comment.json	FAIL	find with document comment	find[0]: unexpected extra keys ["x"]
 find-comment.json	SKIP	find with document comment - pre 4.4	needs server <= 4.2.99
-find-comment.json	FAIL	find with comment sets comment on getMore	events client0[1].command.comment: missing from actual
 find-comment.json	SKIP	find with comment does not set comment on getMore - pre 4.4	needs server <= 4.3.99
 find-let.json	SKIP	Find with let option	needs server >= 5.0
 find-let.json	FAIL	Find with let option unsupported (server-side error)	find: expected an error, the operation succeeded
@@ -367,8 +357,6 @@ findOneAndDelete-comment.json	SKIP	findOneAndDelete with comment - pre 4.4	needs
 findOneAndDelete-hint-serverError.json	SKIP	*	needs server <= 4.3.3
 findOneAndDelete-hint-unacknowledged.json	SKIP	Unacknowledged findOneAndDelete with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 findOneAndDelete-hint-unacknowledged.json	SKIP	Unacknowledged findOneAndDelete with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-findOneAndDelete-hint-unacknowledged.json	FAIL	Unacknowledged findOneAndDelete with hint string on 4.4+ server	MongoCompatibilityError: hint for the findAndModify command is only supported on MongoDB 4.4+
-findOneAndDelete-hint-unacknowledged.json	FAIL	Unacknowledged findOneAndDelete with hint document on 4.4+ server	MongoCompatibilityError: hint for the findAndModify command is only supported on MongoDB 4.4+
 findOneAndDelete-let.json	SKIP	findOneAndDelete with let option	needs server >= 5.0
 findOneAndDelete-let.json	FAIL	findOneAndDelete with let option unsupported (server-side error)	findOneAndDelete: expected an error, the operation succeeded
 findOneAndDelete-rawdata.json	SKIP	findOneAndDelete with rawData option	needs server >= 8.2.0
@@ -379,8 +367,6 @@ findOneAndReplace-dots_and_dollars.json	FAIL	Replacing document with dollar-pref
 findOneAndReplace-hint-serverError.json	SKIP	*	needs server <= 4.3.0
 findOneAndReplace-hint-unacknowledged.json	SKIP	Unacknowledged findOneAndReplace with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 findOneAndReplace-hint-unacknowledged.json	SKIP	Unacknowledged findOneAndReplace with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-findOneAndReplace-hint-unacknowledged.json	FAIL	Unacknowledged findOneAndReplace with hint string on 4.4+ server	MongoCompatibilityError: hint for the findAndModify command is only supported on MongoDB 4.4+
-findOneAndReplace-hint-unacknowledged.json	FAIL	Unacknowledged findOneAndReplace with hint document on 4.4+ server	MongoCompatibilityError: hint for the findAndModify command is only supported on MongoDB 4.4+
 findOneAndReplace-let.json	SKIP	findOneAndReplace with let option	needs server >= 5.0
 findOneAndReplace-let.json	FAIL	findOneAndReplace with let option unsupported (server-side error)	findOneAndReplace: expected an error, the operation succeeded
 findOneAndReplace-rawdata.json	SKIP	findOneAndReplace with rawData option	needs server >= 8.2.0
@@ -404,8 +390,6 @@ findOneAndUpdate-errorResponse.json	SKIP	findOneAndUpdate document validation er
 findOneAndUpdate-hint-serverError.json	SKIP	*	needs server <= 4.3.0
 findOneAndUpdate-hint-unacknowledged.json	SKIP	Unacknowledged findOneAndUpdate with hint string fails with client-side error on pre-4.4 server	needs server <= 4.2.99
 findOneAndUpdate-hint-unacknowledged.json	SKIP	Unacknowledged findOneAndUpdate with hint document fails with client-side error on pre-4.4 server	needs server <= 4.2.99
-findOneAndUpdate-hint-unacknowledged.json	FAIL	Unacknowledged findOneAndUpdate with hint string on 4.4+ server	MongoCompatibilityError: hint for the findAndModify command is only supported on MongoDB 4.4+
-findOneAndUpdate-hint-unacknowledged.json	FAIL	Unacknowledged findOneAndUpdate with hint document on 4.4+ server	MongoCompatibilityError: hint for the findAndModify command is only supported on MongoDB 4.4+
 findOneAndUpdate-let.json	SKIP	findOneAndUpdate with let option	needs server >= 5.0
 findOneAndUpdate-let.json	FAIL	findOneAndUpdate with let option unsupported (server-side error)	findOneAndUpdate: expected an error, the operation succeeded
 findOneAndUpdate-pipeline.json	FAIL	FindOneAndUpdate using pipelines	MongoServerError: update must be a document