[bugf][swarm-router][drop "auto" from SwarmType, which had no factory entry (kyegomez#2057)]

"auto" was a member of the SwarmType Literal but absent from
_initialize_swarm_factory, so reliability_check accepted it at construction and
the first run() raised. A caller reading the type hint, or an IDE completing
it, saw a legitimate option that always failed later.

Removed rather than implemented: the class docstring's supported list and its
factory-backed list both already exclude it, and there is no auto-selection
anywhere in the file. Construction now rejects it with the same message that
lists the valid types, which is what "AutoSwarmBuilder" already does.

CLAUDE.md advertised it in the swarm_type table and the choosing-a-structure
table; both now point at AutoSwarmBuilder.

test_run_with_auto asserted the old behaviour and failed on master. It now
pins that the value is absent from the Literal and rejected at construction.

Author: ayaangazali

CLAUDE.md

@@ -510,7 +510,6 @@ result = router.run("Write a blog post about transformer architectures.")
 | `"BatchedGridWorkflow"` | Grid-based batch execution |
 | `"LLMCouncil"` | LLM-based council decisions |
 | `"AutoSwarmBuilder"` | Auto-configures everything |
-| `"auto"` | Router selects swarm_type automatically |
 
 ---
 
@@ -938,7 +937,7 @@ agent = Agent(
 | High-stakes ruling with deliberation | `CouncilAsAJudge` |
 | Structured adversarial debate | `DebateWithJudge` |
 | Deep research, many loops | `HeavySwarm` |
-| Don't know yet / rapid prototyping | `AutoSwarmBuilder` or `SwarmRouter(swarm_type="auto")` |
+| Don't know yet / rapid prototyping | `AutoSwarmBuilder` |
 | Need to switch architectures easily | `SwarmRouter` |
 
 ---

swarms/structs/swarm_router.py

@@ -137,7 +137,6 @@ def _msg_batch_run_error(err: Exception, tb: str) -> str:
     "GroupChat",
     "MultiAgentRouter",
     "HierarchicalSwarm",
-    "auto",
     "MajorityVoting",
     "CouncilAsAJudge",
     "HeavySwarm",
@@ -303,7 +302,7 @@ def __init__(
         description: str = "Routes your task to the desired swarm",
         max_loops: int = 1,
         agents: List[Union[Agent, Callable]] = [],
-        swarm_type: SwarmType = "SequentialWorkflow",  # "ConcurrentWorkflow" # "auto"
+        swarm_type: SwarmType = "SequentialWorkflow",
         autosave: bool = False,
         rearrange_flow: str = None,
         output_type: OutputType = "dict",

tests/structs/test_swarm_router.py

@@ -1,4 +1,5 @@
 import pytest
+from typing import get_args
 
 from swarms.structs.swarm_router import (
     SwarmRouter,
@@ -473,19 +474,21 @@ def test_run_with_hierarchical_swarm():
     assert result is not None
 
 
-def test_run_with_auto():
-    """SwarmRouter dispatches to 'auto' (embedding-based selection)."""
-    sample_agents = create_sample_agents()
-
-    router = SwarmRouter(
-        agents=sample_agents,
-        swarm_type="auto",
-        max_loops=1,
-        verbose=False,
+def test_auto_is_rejected_at_construction():
+    from swarms.structs.swarm_router import (
+        SwarmRouterConfigError,
+        SwarmType,
     )
 
-    result = router.run("What is 1+1?")
-    assert result is not None
+    assert "auto" not in get_args(SwarmType)
+
+    with pytest.raises(SwarmRouterConfigError):
+        SwarmRouter(
+            agents=create_sample_agents(),
+            swarm_type="auto",
+            max_loops=1,
+            verbose=False,
+        )
 
 
 def test_run_with_majority_voting():