diff --git a/mercurial/bundlecaches.py b/mercurial/bundlecaches.py
--- a/mercurial/bundlecaches.py
+++ b/mercurial/bundlecaches.py
@@ -60,6 +60,7 @@ class bundlespec:
 _bundlespeccgversions = {
     b'v1': b'01',
     b'v2': b'02',
+    b'v3': b'03',
     b'packed1': b's1',
     b'bundle2': b'02',  # legacy
 }
@@ -82,6 +83,14 @@ class bundlespec:
         b'tagsfnodescache': True,
         b'revbranchcache': True,
     },
+    b'v3': {
+        b'changegroup': True,
+        b'cg.version': b'03',
+        b'obsolescence': False,
+        b'phases': True,
+        b'tagsfnodescache': True,
+        b'revbranchcache': True,
+    },
     b'streamv2': {
         b'changegroup': False,
         b'cg.version': b'02',
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1714,8 +1714,9 @@ def bundle(ui, repo, fname, *dests, **op
     bundlespec.set_param(
         b'obsolescence-mandatory', obs_mand_cfg, overwrite=False
     )
-    phases_cfg = cfg(b'experimental', b'bundle-phases')
-    bundlespec.set_param(b'phases', phases_cfg, overwrite=False)
+    if not bundlespec.params.get(b'phases', False):
+        phases_cfg = cfg(b'experimental', b'bundle-phases')
+        bundlespec.set_param(b'phases', phases_cfg, overwrite=False)
 
     bundle2.writenewbundle(
         ui,
diff --git a/tests/test-bundle-type.t b/tests/test-bundle-type.t
--- a/tests/test-bundle-type.t
+++ b/tests/test-bundle-type.t
@@ -109,7 +109,7 @@ unfortunate that the phase information f
   >   echo
   > }
 
-  $ for t in "None" "bzip2" "gzip" "none-v2" "v2" "v1" "gzip-v1"; do
+  $ for t in "None" "bzip2" "gzip" "none-v2" "v2" "v1" "gzip-v1" "v3"; do
   >   testbundle $t
   > done
   % test bundle type None
@@ -365,6 +365,47 @@ unfortunate that the phase information f
   o  [draft] commit_root
   
   
+  % test bundle type v3
+  ===================================
+  7 changesets found
+  HG20\x00\x00 (esc)
+  Stream params: {Compression: BZ}
+  changegroup -- {nbchanges: 7, targetphase: 2, version: 03} (mandatory: True)
+      ac39af4a9f7d2aaa7d244720e57838be9bf63b03
+      901e97fadc587978ec52f2fa76af4aefc2d191e8
+      a8c3a1ed30eb71f03f476c5fa7ead831ef991a55
+      66e2c4b43e0cf8f0bdff0733a0b97ce57874e35d
+      624e609639853fe22c88d42a8fd1f53a0e9b7ebe
+      2ea90778052ba7558fab36e3fd5d149512ff986b
+      b9f5f740a8cd76700020e3903ee55ecff78bd3e5
+  cache:rev-branch-cache -- {} (mandatory: False)
+  phase-heads -- {} (mandatory: True)
+      66e2c4b43e0cf8f0bdff0733a0b97ce57874e35d public
+      a8c3a1ed30eb71f03f476c5fa7ead831ef991a55 draft
+      2ea90778052ba7558fab36e3fd5d149512ff986b draft
+  bzip2-v2;cg.version=03
+  
+  adding changesets
+  adding manifests
+  adding file changes
+  added 7 changesets with 7 changes to 1 files (+1 heads)
+  new changesets ac39af4a9f7d:b9f5f740a8cd (4 drafts, 1 secrets)
+  (run 'hg heads' to see heads, 'hg merge' to merge)
+  o  [secret] commit_6
+  |
+  o  [draft] commit_5
+  |
+  o  [draft] commit_4
+  |
+  o  [public] commit_3
+  |
+  | o  [draft] commit_2
+  | |
+  | o  [draft] commit_1
+  |/
+  o  [public] commit_root
+  
+  
 
 Compression level can be adjusted for bundle2 bundles