diff --git a/mercurial/help/internals/wireprotocol.txt b/mercurial/help/internals/wireprotocol.txt
--- a/mercurial/help/internals/wireprotocol.txt
+++ b/mercurial/help/internals/wireprotocol.txt
@@ -1778,6 +1778,21 @@ The response is a map with bytestring ke
 
 TODO consider using binary to represent nodes in certain pushkey namespaces.
 
+lookup
+------
+
+Try to resolve a value to a changeset revision.
+
+Unlike ``known`` which operates on changeset nodes, lookup operates on
+node fragments and other names that a user may use.
+
+The command receives the following arguments:
+
+key
+   (bytestring) Value to try to resolve.
+
+On success, returns a bytestring containing the resolved node.
+
 pushkey
 -------
 
diff --git a/mercurial/wireproto.py b/mercurial/wireproto.py
--- a/mercurial/wireproto.py
+++ b/mercurial/wireproto.py
@@ -1120,7 +1120,8 @@ def listkeys(repo, proto, namespace):
     d = sorted(repo.listkeys(encoding.tolocal(namespace)).items())
     return wireprototypes.bytesresponse(pushkeymod.encodekeys(d))
 
-@wireprotocommand('lookup', 'key', permission='pull')
+@wireprotocommand('lookup', 'key', permission='pull',
+                  transportpolicy=POLICY_V1_ONLY)
 def lookup(repo, proto, key):
     try:
         k = encoding.tolocal(key)
@@ -1378,6 +1379,20 @@ def listkeysv2(repo, proto, namespace=No
 
     return wireprototypes.cborresponse(keys)
 
+@wireprotocommand('lookup',
+                  args={
+                      'key': b'foo',
+                  },
+                  permission='pull',
+                  transportpolicy=POLICY_V2_ONLY)
+def lookupv2(repo, proto, key):
+    key = encoding.tolocal(key)
+
+    # TODO handle exception.
+    node = repo.lookup(key)
+
+    return wireprototypes.cborresponse(node)
+
 @wireprotocommand('pushkey',
                   args={
                       'namespace': b'ns',
diff --git a/tests/test-wireproto-command-capabilities.t b/tests/test-wireproto-command-capabilities.t
--- a/tests/test-wireproto-command-capabilities.t
+++ b/tests/test-wireproto-command-capabilities.t
@@ -30,11 +30,11 @@ capabilities request returns an array of
   s>     \r\n
   s>     *\r\n (glob)
   s>     *\x00\x01\x00\x02\x01F (glob)
-  s>     \xa2Hcommands\xa9Eheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyFlegacyKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyCnewCnewColdColdInamespaceBnsKpermissions\x81DpullHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullHunbundle\xa2Dargs\xa1EheadsFlegacyKpermissions\x81DpushIbranchmap\xa2Dargs\xa0Kpermissions\x81DpullIgetbundle\xa2Dargs\xa1A*FlegacyKpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullKcompression\x82\xa1DnameDzstd\xa1DnameDzlib
+  s>     \xa2Hcommands\xa9Eheads\xa2Dargs\xa1Jpubliconly\xf4Kpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\x81HdeadbeefKpermissions\x81DpullFlookup\xa2Dargs\xa1CkeyCfooKpermissions\x81DpullGpushkey\xa2Dargs\xa4CkeyCkeyCnewCnewColdColdInamespaceBnsKpermissions\x81DpushHlistkeys\xa2Dargs\xa1InamespaceBnsKpermissions\x81DpullHunbundle\xa2Dargs\xa1EheadsFlegacyKpermissions\x81DpushIbranchmap\xa2Dargs\xa0Kpermissions\x81DpullIgetbundle\xa2Dargs\xa1A*FlegacyKpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullKcompression\x82\xa1DnameDzstd\xa1DnameDzlib
   s>     \r\n
   received frame(size=*; request=1; stream=2; streamflags=stream-begin; type=bytes-response; flags=eos|cbor) (glob)
   s>     0\r\n
   s>     \r\n
-  response: [{b'commands': {b'branchmap': {b'args': {}, b'permissions': [b'pull']}, b'capabilities': {b'args': {}, b'permissions': [b'pull']}, b'getbundle': {b'args': {b'*': b'legacy'}, b'permissions': [b'pull']}, b'heads': {b'args': {b'publiconly': False}, b'permissions': [b'pull']}, b'known': {b'args': {b'nodes': [b'deadbeef']}, b'permissions': [b'pull']}, b'listkeys': {b'args': {b'namespace': b'ns'}, b'permissions': [b'pull']}, b'lookup': {b'args': {b'key': b'legacy'}, b'permissions': [b'pull']}, b'pushkey': {b'args': {b'key': b'key', b'namespace': b'ns', b'new': b'new', b'old': b'old'}, b'permissions': [b'pull']}, b'unbundle': {b'args': {b'heads': b'legacy'}, b'permissions': [b'push']}}, b'compression': [{b'name': b'zstd'}, {b'name': b'zlib'}]}]
+  response: [{b'commands': {b'branchmap': {b'args': {}, b'permissions': [b'pull']}, b'capabilities': {b'args': {}, b'permissions': [b'pull']}, b'getbundle': {b'args': {b'*': b'legacy'}, b'permissions': [b'pull']}, b'heads': {b'args': {b'publiconly': False}, b'permissions': [b'pull']}, b'known': {b'args': {b'nodes': [b'deadbeef']}, b'permissions': [b'pull']}, b'listkeys': {b'args': {b'namespace': b'ns'}, b'permissions': [b'pull']}, b'lookup': {b'args': {b'key': b'foo'}, b'permissions': [b'pull']}, b'pushkey': {b'args': {b'key': b'key', b'namespace': b'ns', b'new': b'new', b'old': b'old'}, b'permissions': [b'push']}, b'unbundle': {b'args': {b'heads': b'legacy'}, b'permissions': [b'push']}}, b'compression': [{b'name': b'zstd'}, {b'name': b'zlib'}]}]
 
   $ cat error.log
diff --git a/tests/test-wireproto-command-lookup.t b/tests/test-wireproto-command-lookup.t
new file mode 100644
--- /dev/null
+++ b/tests/test-wireproto-command-lookup.t
@@ -0,0 +1,55 @@
+  $ . $TESTDIR/wireprotohelpers.sh
+
+  $ hg init server
+  $ enablehttpv2 server
+  $ cd server
+  $ cat >> .hg/hgrc << EOF
+  > [web]
+  > push_ssl = false
+  > allow-push = *
+  > EOF
+  $ hg debugdrawdag << EOF
+  > C D
+  > |/
+  > B
+  > |
+  > A
+  > EOF
+
+  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
+  $ cat hg.pid > $DAEMON_PIDS
+
+lookup for known node works
+
+  $ sendhttpv2peer << EOF
+  > command lookup
+  >     key 426bada5c67598ca65036d57d9e4b64b0c1ce7a0
+  > EOF
+  creating http peer for wire protocol version 2
+  sending lookup command
+  s>     *\r\n (glob)
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0003\r\n
+  s>     content-type: application/mercurial-exp-framing-0003\r\n
+  s>     content-length: 73\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     A\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa1CkeyX(426bada5c67598ca65036d57d9e4b64b0c1ce7a0DnameFlookup
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0003\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     1d\r\n
+  s>     *\x00\x01\x00\x02\x01F (glob)
+  s>     TBk\xad\xa5\xc6u\x98\xcae\x03mW\xd9\xe4\xb6K\x0c\x1c\xe7\xa0
+  s>     \r\n
+  received frame(size=*; request=1; stream=2; streamflags=stream-begin; type=bytes-response; flags=eos|cbor) (glob)
+  s>     0\r\n
+  s>     \r\n
+  response: [b'Bk\xad\xa5\xc6u\x98\xcae\x03mW\xd9\xe4\xb6K\x0c\x1c\xe7\xa0']
+
+  $ cat error.log