Wire Protocol

Feature	Status
OP_MSG (commands)	✅ Supported
OP_QUERY (legacy)	✅ Supported
OP_GET_MORE	✅ Supported
OP_KILL_CURSORS	✅ Supported
TLS (--tls flag)	✅ Supported
Checksum flag (0x10000) parse	✅ Supported
Checksum flag (0x10000) write	❌ Not implemented
maxWireVersion	✅ 21 (MongoDB 8.0+)

CRUD Operations

Operation	Status
insertOne / insertMany	✅ Supported
find with filter, projection, sort, skip, limit	✅ Supported
findOne	✅ Supported
updateOne / updateMany	✅ Supported
deleteOne / deleteMany	✅ Supported
findAndModify (update, remove, upsert, returnNew, sort, fields)	✅ Supported
count	✅ Supported
distinct	✅ Supported
getMore (batched cursor)	✅ Supported
killCursors	✅ Supported
Bulk writes (document sequences)	✅ Supported

Aggregation Pipeline

Stage	Status
$match (pushdown + in-memory)	✅ Supported
$sort (multi-field)	✅ Supported
$skip	✅ Supported
$limit	✅ Supported
$project (inclusion/exclusion, _id handling)	✅ Supported
$group — $sum, $avg, $min, $max, $first, $last, $push, $addToSet, $stdDevPop, $stdDevSamp, $mergeObjects	✅ Supported
$count	✅ Supported
$unwind (string + document syntax)	✅ Supported
$addFields / $set	✅ Supported
$sample	✅ Supported
$replaceRoot	✅ Supported
$sortByCount	✅ Supported
$lookup (equality + pipeline syntax)	✅ Supported
$out	✅ Supported
$facet	✅ Supported
$unset	✅ Supported
$replaceWith	✅ Supported
Expression operators ($gt, $gte, $lt, $lte, $eq, $ne, $and, $or, $not, $add, $subtract, $multiply, $divide, $mod, $concat, $cond, $ifNull, $literal, $size)	✅ Supported
String operators ($toLower, $toUpper, $substrCP, $strLenCP, $trim, $ltrim, $rtrim, $regexMatch)	✅ Supported
Array operators ($arrayElemAt, $reverseArray, $slice, $in, $size)	✅ Supported
Math operators ($abs, $ceil, $floor, $round, $trunc, $sqrt, $cmp)	✅ Supported
Type operators ($type, $toDouble, $toInt, $toLong, $toString, $convert)	✅ Supported
Date operators ($year, $month, $dayOfMonth, $dayOfWeek, $dayOfYear, $hour, $minute, $second, $millisecond, $week)	✅ Supported
$bucket, $bucketAuto	❌ Not implemented
$graphLookup, $geoNear	❌ Not implemented
$merge	❌ Not implemented

Index Management

Operation	Status
createIndexes (single, compound, unique)	✅ Supported
listIndexes	✅ Supported
dropIndexes	✅ Supported
Index-backed queries	✅ Supported
TTL / text / geospatial indexes	❌ Not implemented

Authentication & Authorization

Feature	Status
SCRAM-SHA-256	✅ Supported
SCRAM-SHA-1	✅ Supported
--no-auth flag	✅ Supported
Client proof verification	✅ Supported
Role-based authorization	✅ Supported
Roles: root, readWrite, read, userAdmin	✅ Supported
createUser / updateUser / dropUser	✅ Supported
usersInfo	✅ Supported
User persistence (SQLite)	✅ Supported

Database & Collection Management

Operation	Status
createCollection	✅ Supported
drop collection	✅ Supported
dropDatabase	✅ Supported
listDatabases	✅ Supported
listCollections	✅ Supported
collStats / dbStats	✅ Supported

Tool Compatibility

Tool	Status
mongosh	✅ Verified
mongodump	✅ Verified
mongorestore	✅ Verified
pymongo 4.x	⚠️ See note
MongoDB drivers (OP_MSG)	✅ Verified

⚠️ pymongo 4.17+ C-level BSON encoder strips $-prefixed keys from documents nested inside arrays, which breaks aggregate pipeline stages sent via coll.aggregate(). Use mongosh or raw BSON for aggregate commands. All other operations work correctly with pymongo.

Type Sensitivity

Behavior	Detail
Bson::as_i64() / as_f64() / as_str()	✅ Match exact types only — Int32(5).as_i64() returns None
bson_to_i64() / bson_to_f64()	✅ Used throughout — handle Int32, Int64, Double correctly
$regex with RegularExpression	✅ Both string and /pattern/ syntax supported
Int32/Int64/Double in arithmetic	✅ All operators preserve correct types — $add returns Int64 when all inputs are integer