Forum 1.13.0: a zero-dependency MCP orchestrator with a replayable causal ledger

[HarperZ9]

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What would you like to share?

I built Forum because a tool-using workflow needs more than a transport log when it branches, pauses for human approval, crashes, or resumes.

Forum 1.13.0 is a Python 3.11+ orchestration engine with no third-party runtime dependencies. forum mcp exposes the same engine as the CLI and HTTP daemon over stdio. The MCP surface includes routing, planning, submission, status, runtime inspection, context preflight, approval gates, ledger summaries, replay, and verification.

The part I most want feedback on is the causal record. Every request, plan, task, result, approval, and verdict is appended to a hash-chained, content-addressed ledger. The chain check and payload-body check are separate. That matters because a chain can still link after a stored body is altered; the offline demo deliberately makes that edit and shows verify(deep=True) fail.

A few implementation lessons so far:

• MCP, HTTP, and CLI share one engine so the tool surfaces cannot quietly drift apart.
• A resumed run reuses only tasks already witnessed as successful in the durable ledger.
• Human approvals are first-class events, including edits, rejection, deadlines, and witnessed expiry decisions.
• The record can establish integrity and causal linkage for what was captured. It does not prove that a tool call was authorized, correct, aligned, or safe.

Quick local proof:

pip install forum-engine
git clone https://github.com/HarperZ9/forum
cd forum
python examples/demo.py

That demo needs no model and no network call. For an MCP client, the server starts with forum mcp; a model command or OpenAI-compatible endpoint can be supplied when task execution is needed.

I am especially interested in feedback on two questions:

1. What is the smallest useful causal receipt for an MCP workflow that can pause and resume?
2. Where should replay, approval, and payload-integrity evidence align with MCP logging or tracing work already underway?

Forum is fair-source rather than OSI open source. The repository is public, the package is installable, and commercial use is reserved under the project license.

Relevant Links

• Repository: https://github.com/HarperZ9/forum
• PyPI: https://pypi.org/project/forum-engine/
• Browser-viewable replay demo: https://harperz9.github.io/demo-forum.html
• Current green CI run: https://github.com/HarperZ9/forum/actions/runs/29538279528