Add dualpass to Demo Harnesses

[Chris-Rebentisch]

Summary

Adds dualpass to the Demo Harnesses section under Reference Implementations.

What it is

dualpass is a reliability-first agent harness whose headline primitive is cross-vendor independent review: the author agent runs on one CLI (e.g. claude), the reviewer agent runs on a different vendor's CLI (e.g. cursor-agent), and either is swappable without touching the harness. The pattern this productizes — a different-vendor model as the reviewer of every stage's output — is the strongest documented lever against self-evaluation bias in long-running coding agents.

Why it fits Demo Harnesses

Like Open SWE / OpenHands / Aider / SmallCode in this section, dualpass is a complete open-source harness with a specific design point worth studying:

• Fixed-cycle pipeline (research → outline → spec → prompt → code → audit → handoff)
• Dual-pass parallel reviewer with cross-vendor fallback on [resource_exhausted]
• Build-marker YAML frontmatter — author-driven halt contract (only the author can stop the pipeline mid-stage; reviewers always auto-continue to next revision round)
• Five built-in preflight gates (frontmatter, line-citations, single-flight, marker-frontmatter, acceptance-criteria-wording)
• Circuit breaker on no-progress loops (SHA-256 artifact hash + 3-strike heuristic)
• Background watchers (research/prompt/handoff) for overnight unattended runs
• Cross-unit retro pattern aggregator (EventType counts + bigram frequencies across units)

Distilled from a real production-campaign of multi-day agent builds. Apache-2.0, Python 3.12+, on PyPI as of today.

Contribution checklist

• Addresses a specific harness problem (cross-vendor reviewer as a primitive, preflight gates, author-driven halts).
• Vendor-agnostic by principle — CLIs are templated; claude + cursor-agent are defaults but swap freely (codex, any CLI matching the agent-template contract).
• Format: - [Name](URL) — 1–2 sentence note explaining why it's worth including.
• Added under the appropriate section: Reference Implementations → Demo Harnesses.

Happy to adjust placement or wording per your preference.