Formal semantics for CancellationToken and topic-based pub/sub

[greatmengqi]

AutoGen v0.4's CancellationToken (_cancellation_token.py) and topic-subscription model are the most principled cancellation and observability designs among the major agent frameworks.

I wrote a paper formalizing these patterns. The cancellation result that may interest you: cancellation can be modeled as a monad transformer on the interpreter's effect functor, adding zero new AST primitives. This gives you structural propagation through shared context and cleanup soundness for free — which aligns closely with how AutoGen's CancellationToken.cancel() + link_future() already works.

Papers:

• v1 — primitives + DAG completeness: https://doi.org/10.5281/zenodo.19573903
• v2 — six extensions with proofs: https://doi.org/10.5281/zenodo.19574625

The formalization covers six axes (observability, shared state, event rendezvous, control transfer, sessions, cancellation) across four frameworks. AutoGen is the only one that gets cancellation right at the API level.