diff --git a/eden/scm/sapling/ext/github/submit.py b/eden/scm/sapling/ext/github/submit.py
index 423bdaff16bcf..b502359956847 100644
--- a/eden/scm/sapling/ext/github/submit.py
+++ b/eden/scm/sapling/ext/github/submit.py
@@ -75,17 +75,17 @@ def from_config(ui) -> "SubmitWorkflow":
         workflow = ui.config(
             "github", "pr-workflow", ui.config("github", "pr_workflow")
         )
-        if not workflow or workflow == "overlap":
-            # For now, default to OVERLAP.
-            return SubmitWorkflow.OVERLAP
-        elif workflow == "single":
+        if not workflow or workflow == "single":
+            # Default to SINGLE.
             return SubmitWorkflow.SINGLE
+        elif workflow == "overlap":
+            return SubmitWorkflow.OVERLAP
         else:
             # Note that "classic" is not recognized yet.
             ui.warn(
                 _("unrecognized config for github.pr_workflow: defaulting to 'overlap'")
             )
-            return SubmitWorkflow.OVERLAP
+            return SubmitWorkflow.SINGLE
 
 
 @dataclass
@@ -160,8 +160,6 @@ async def update_commits_in_stack(
 
     store = PullRequestStore(repo)
 
-    workflow = SubmitWorkflow.from_config(ui)
-
     partitions = await get_partitions(ui, repo, store, "sort(. %% public(), -rev)")
     if not partitions:
         ui.status_err(_("no commits to submit\n"))
@@ -211,6 +209,14 @@ def get_gitdir() -> str:
         return 0
 
     repository = params.repository
+    if not repository:
+        repository = await get_repository_for_origin(origin, github_repo.hostname)
+
+    if repository.upstream is not None:
+        # Always use OVERLAP workflow for forked repositories
+        workflow = SubmitWorkflow.OVERLAP
+    else:
+        workflow = SubmitWorkflow.from_config(ui)
 
     # For the SINGLE workflow, we must update the base branch on existing PRs
     # BEFORE pushing the new branch contents. Otherwise, when commits are
@@ -223,10 +229,6 @@ def get_gitdir() -> str:
             p for p in partitions if p[0].pr and p[0].pr.state == PullRequestState.OPEN
         ]
         if existing_prs:
-            if not repository:
-                repository = await get_repository_for_origin(
-                    origin, github_repo.hostname
-                )
             # Update base branches on existing PRs before pushing.
             # Process from bottom of stack to top so bases are set correctly.
             for index in range(len(partitions)):
@@ -254,8 +256,6 @@ def get_gitdir() -> str:
     run_git_command(git_push_args, gitdir)
 
     if params.pull_requests_to_create:
-        if not repository:
-            repository = await get_repository_for_origin(origin, github_repo.hostname)
         if use_placeholder_strategy:
             assert isinstance(params, PlaceholderStrategyParams)
             await create_pull_requests_from_placeholder_issues(
@@ -286,8 +286,6 @@ def get_gitdir() -> str:
     # Add the head of the stack to the sapling-pr-archive branch.
     tip = hex(partitions[0][0].node)
 
-    if not repository:
-        repository = await get_repository_for_origin(origin, github_repo.hostname)
     rewrite_and_archive_requests = [
         rewrite_pull_request_body(
             partitions, index, workflow, pr_numbers_and_num_commits, repository, ui
diff --git a/eden/scm/tests/github/mock_create_prs.py b/eden/scm/tests/github/mock_create_prs.py
index 2bd5cd653b503..64523a34afe50 100644
--- a/eden/scm/tests/github/mock_create_prs.py
+++ b/eden/scm/tests/github/mock_create_prs.py
@@ -26,7 +26,7 @@ def setup_mock_github_server(ui) -> MockGitHubServer:
         (43, "two\n"),
     ]
 
-    single = ui.config("github", "pr-workflow") == "single"
+    single = ui.config("github", "pr-workflow") != "overlap"
 
     for idx, (num, msg) in enumerate(prs):
         title, body = title_and_body(msg)
diff --git a/eden/scm/tests/test-ext-github-pr-submit-closed.t b/eden/scm/tests/test-ext-github-pr-submit-closed.t
index cf4244c465667..ea5af78c403be 100644
--- a/eden/scm/tests/test-ext-github-pr-submit-closed.t
+++ b/eden/scm/tests/test-ext-github-pr-submit-closed.t
@@ -4,7 +4,7 @@
   $ enable github
   $ export SL_TEST_GH_URL=https://github.com/facebook/test_github_repo.git
   $ . $TESTDIR/git.sh
-  $ configure github.pr-workflow=single
+  $ setconfig github.pr-workflow=single
 
 build up a github repo
 
diff --git a/eden/scm/tests/test-ext-github-pr-submit-open.t b/eden/scm/tests/test-ext-github-pr-submit-open.t
index 3d5a2ee37b5d9..215868b0694f3 100644
--- a/eden/scm/tests/test-ext-github-pr-submit-open.t
+++ b/eden/scm/tests/test-ext-github-pr-submit-open.t
@@ -6,7 +6,7 @@ Test that `sl pr submit --open` opens created PRs in the browser.
   $ enable github
   $ export SL_TEST_GH_URL=https://github.com/facebook/test_github_repo.git
   $ . $TESTDIR/git.sh
-  $ configure github.pr-workflow=overlap
+  $ setconfig github.pr-workflow=overlap
 
 build up a github repo
 
diff --git a/eden/scm/tests/test-ext-github-pr-submit-overlap.t b/eden/scm/tests/test-ext-github-pr-submit-overlap.t
index eeac14c337fe0..eeab63272e6af 100644
--- a/eden/scm/tests/test-ext-github-pr-submit-overlap.t
+++ b/eden/scm/tests/test-ext-github-pr-submit-overlap.t
@@ -4,7 +4,7 @@
   $ enable github
   $ export SL_TEST_GH_URL=https://github.com/facebook/test_github_repo.git
   $ . $TESTDIR/git.sh
-  $ configure github.pr-workflow=overlap
+  $ setconfig github.pr-workflow=overlap
 
 build up a github repo
 
diff --git a/eden/scm/tests/test-ext-github-pr-submit-single.t b/eden/scm/tests/test-ext-github-pr-submit-single.t
index b9e4d8fd527a6..7cc8746e667ad 100644
--- a/eden/scm/tests/test-ext-github-pr-submit-single.t
+++ b/eden/scm/tests/test-ext-github-pr-submit-single.t
@@ -4,7 +4,7 @@
   $ enable github
   $ export SL_TEST_GH_URL=https://github.com/facebook/test_github_repo.git
   $ . $TESTDIR/git.sh
-  $ configure github.pr-workflow=single
+  $ setconfig github.pr-workflow=single
 
 build up a github repo