fix: skip registry republish for tools never exported on source

Empty Prompt Studio projects cannot be exported (backend guard), so
they have no source registry entry and no workflow references. The
phase previously republished unconditionally, turning these into
counted failures on every run. Now the source registry lookup runs
first and the export + remap are skipped when no entry exists.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: chandrasekharan-zipstack

src/unstract/clone/phases/custom_tool.py

@@ -18,6 +18,8 @@
 5. Republishes ``PromptStudioRegistry`` via the export action and
    records the ``custom_tool`` + ``prompt_studio_registry`` remaps so
    downstream ToolInstancePhase can rewrite ``ToolInstance.tool_id``.
+   Skipped for tools with no source registry entry (never exported —
+   e.g. empty projects, which the backend refuses to export).
 
 Adapter id discovery for the fresh path needs all four of LLM,
 vector_db, embedding, x2text. If any source adapter can't be resolved
@@ -163,6 +165,30 @@ def _clone_one(
         if self.ctx.options.dry_run:
             return
 
+        # Tools never exported on source (e.g. empty projects — backend
+        # blocks their export) have no registry entry and no workflow
+        # references; republishing would fail the same backend guard.
+        try:
+            src_regs = self.ctx.source.list_registries(custom_tool=src_tool_id)
+        except Exception as e:
+            logger.warning(
+                "source registry lookup failed for tool '%s' "
+                "(downstream ToolInstance clone may skip): %s",
+                tool_name,
+                e,
+            )
+            with lock:
+                result.failed += 1
+                result.errors.append(f"registry remap lookup {tool_name}: {e}")
+            return
+
+        if not src_regs:
+            logger.info(
+                "tool '%s' was never exported on source; skipping registry republish",
+                tool_name,
+            )
+            return
+
         try:
             self.ctx.target.export_custom_tool(tgt_tool_id)
             logger.info(
@@ -176,11 +202,10 @@ def _clone_one(
             return
 
         try:
-            src_regs = self.ctx.source.list_registries(custom_tool=src_tool_id)
             tgt_regs = self.ctx.target.list_registries(custom_tool=tgt_tool_id)
         except Exception as e:
             logger.warning(
-                "registry remap lookup failed for tool '%s' "
+                "target registry lookup failed for tool '%s' "
                 "(downstream ToolInstance clone may skip): %s",
                 tool_name,
                 e,

tests/clone/test_custom_tool_phase.py

@@ -363,6 +363,31 @@ def test_frictionless_adapter_dependence_skips_tool_and_records_for_cascade():
     assert SRC_REG in ctx.skipped_custom_tool_registry_ids
 
 
+def test_never_exported_source_tool_skips_registry_republish():
+    """A source tool with no registry entry (e.g. an empty project — the
+    backend blocks exporting those) clones cleanly without republishing.
+    """
+    src = FakeClient()
+    tgt = FakeClient()
+    _preload_source_tool(src, "src-tool-x", "Empty Project")
+    del src.registries_by_tool["src-tool-x"]
+    src.export_blobs["src-tool-x"]["prompts"] = []
+    _seed_source_adapters(src)
+    _seed_target_adapters(tgt)
+    ctx = _ctx(src, tgt)
+
+    result = CustomToolPhase(ctx).run(CloneReport())
+
+    assert result.created == 1
+    assert result.failed == 0
+    # No registry on source → republish must not fire (it would hit the
+    # backend's empty-project export guard).
+    assert tgt.export_tool_calls == []
+    # Tool remap still recorded; registry remap absent.
+    assert ctx.remap.resolve("custom_tool", "src-tool-x") is not None
+    assert ctx.remap.resolve("prompt_studio_registry", SRC_REG) is None
+
+
 def test_missing_target_adapter_fails_tool_cleanly():
     src = FakeClient()
     tgt = FakeClient()