diff --git a/server/internal/daemon/repocache/cache.go b/server/internal/daemon/repocache/cache.go
index d747fa060..ec3a91830 100644
--- a/server/internal/daemon/repocache/cache.go
+++ b/server/internal/daemon/repocache/cache.go
@@ -399,19 +399,23 @@ func (c *Cache) CreateWorktree(params WorktreeParams) (*WorktreeResult, error) {
 	}
 
 	// Determine the ref to base the worktree on. By default this is the remote's
-	// default branch. Callers may request a specific branch, tag, or commit so
-	// review/QA agents can inspect the exact revision without trying to mutate
-	// the daemon-owned worktree metadata themselves.
+	// default branch (resolved internally via getRemoteDefaultBranch, which walks
+	// origin/HEAD → origin/main, origin/master → bare-HEAD hint into origin/<same>
+	// → single-entry scan of origin/* → bare HEAD when origin/* is empty).
+	// Callers may request a specific branch, tag, or commit so review/QA agents
+	// can inspect the exact revision without trying to mutate the daemon-owned
+	// worktree metadata themselves.
 	baseRef, err := resolveBaseRef(barePath, params.Ref)
 	if err != nil {
 		return nil, err
 	}
 
-	// getRemoteDefaultBranch walks origin/HEAD → origin/main, origin/master →
-	// bare-HEAD hint into origin/<same> → single-entry scan of origin/* → bare
-	// HEAD (only if origin/* is empty). Reaching "" here means the cache is in a
-	// state we refuse to guess from (no origin/HEAD, no main/master, bare HEAD
-	// doesn't match any origin/* entry, and origin/* has multiple candidates).
+	// Empty here means params.Ref was unset and getRemoteDefaultBranch couldn't
+	// resolve a default — the cache is in a state we refuse to guess from (no
+	// origin/HEAD, no main/master, bare HEAD doesn't match any origin/* entry,
+	// and origin/* has multiple candidates). The requested-ref path returns an
+	// explicit error before reaching here, so this branch only fires for the
+	// default-branch case.
 	if baseRef == "" {
 		return nil, fmt.Errorf("cannot resolve default branch for %s: bare cache at %s has no usable refs (origin/* is empty or ambiguous and bare HEAD has no match). The cache may be corrupted; delete it and retry", params.RepoURL, barePath)
 	}
diff --git a/server/internal/daemon/repocache/cache_test.go b/server/internal/daemon/repocache/cache_test.go
index a910a4fe7..971ef8b30 100644
--- a/server/internal/daemon/repocache/cache_test.go
+++ b/server/internal/daemon/repocache/cache_test.go
@@ -591,6 +591,38 @@ func TestCreateWorktreeWithRequestedCommitRef(t *testing.T) {
 	}
 }
 
+func TestCreateWorktreeWithRequestedTagRef(t *testing.T) {
+	t.Parallel()
+	sourceRepo := createTestRepo(t)
+	taggedCommit := gitHead(t, sourceRepo)
+	runGitAuthored(t, sourceRepo, "tag", "v1")
+	// Advance the default branch past the tag so worktree HEAD == taggedCommit
+	// can only be true if the tag was actually resolved (vs falling back to
+	// the default branch tip).
+	addEmptyCommit(t, sourceRepo, "post-tag commit")
+
+	cache := New(t.TempDir(), testLogger())
+	if err := cache.Sync("ws-1", []RepoInfo{{URL: sourceRepo}}); err != nil {
+		t.Fatalf("sync failed: %v", err)
+	}
+
+	result, err := cache.CreateWorktree(WorktreeParams{
+		WorkspaceID: "ws-1",
+		RepoURL:     sourceRepo,
+		WorkDir:     t.TempDir(),
+		Ref:         "v1",
+		AgentName:   "Reviewer",
+		TaskID:      "tag-task-id",
+	})
+	if err != nil {
+		t.Fatalf("CreateWorktree failed: %v", err)
+	}
+
+	if got := gitHead(t, result.Path); got != taggedCommit {
+		t.Fatalf("worktree HEAD = %s, want tagged commit %s", got, taggedCommit)
+	}
+}
+
 func TestCreateWorktreeWithUnknownRequestedRef(t *testing.T) {
 	t.Parallel()
 	sourceRepo := createTestRepo(t)