Harness² vs Superhuman Go: Features, Pricing & Which Is Better (2026)
A side-by-side comparison of Harness² and Superhuman Go — features, pricing, and ideal use cases — to help you decide which AI tool fits your workflow.
H
Harness²
Google Research
Google Research's open-source framework for recursive agent harnessing that refines an agent's prompts, tools and memory per task.
Key features
- Task-Level Recursion: A contrastive Propose-Probe-Compose step proposes edits, probes their effects on the same task and composes a refined harness without ground-truth feedback.
- Harnessing-Level Recursion: A persistent improvement harness is updated with adopted harnesses and evidence-supported lessons from each task.
- Eight Editable Components: Exposes system prompt, guardrails, memory, tool guidance, subagents, skills, scripts and plugins as tunable parts.
- Parallel and Sequential Modes: Scale the task-level recursion budget by exploring candidates in parallel or refining sequentially.
- Multiple Executors: Run refinement with OpenCode and Codex executors.
- Built-In Benchmarks: Setup and run commands for JobBench, LAB (legal work) and WorkBuddy Bench (office, web and code).
- Credential-Free Demo: A local demo with deterministic editors runs both recursion modes without model credentials.
Best for
- Agent Harness Research: Study how contrastive harness edits affect agent performance across benchmarks.
- Improving Base Agents: Raise results of models such as GLM 5 and Gemini 3.5 Flash over their default harnesses.
- Professional Task Evaluation: Evaluate agents on legal, office and coding tasks using bundled benchmark guides.
- Tuning Coding Agents: Refine system prompts, skills and subagents for OpenCode or Codex executors.
- Reproducible Experiments: Run, judge and report benchmark experiments with resume support.
Superhuman Go
Superhuman
Proactive AI assistant and agent platform that works inline across apps, sorting email, briefing you in Slack and improving your writing everywhere.
Key features
- Proactive Inline Suggestions: Annotates text in real time wherever you write, pointing out where you could be clearer, more convincing or factually wrong without needing a prompt.
- Email Assistant Agent: Sorts incoming mail, clears clutter, follows up and pre-drafts replies in your voice using context from your calendar and connected apps, powered by Superhuman Mail.
- Customizable Grammarly Agent: Built-in Grammarly writing intelligence that learns which underlines you find useful and adjusts its feedback accordingly.
- Knowledge Checker and Daily Brief: A background researcher that searches your data sources for evidence behind claims, plus a daily report surfacing Salesforce deals, Jira tickets, tasks and meetings needing attention.
- MCP Connectors: Connects to Gmail, Outlook, Calendar, Slack, Jira, Linear, Asana, Confluence, Zendesk, Salesforce, HubSpot, Workday, ServiceNow and more via pre-built or custom MCP connectors.
- Custom Agents and Agent Store: Build agents that trigger as you type, on a schedule or after events like a meeting ending, or add ready-made agents from Superhuman and partners.
- Many Surfaces: Works as inline underlines, a context-aware side chat, cursor actions on highlighted text, a Slack teammate you can @-mention, and a standalone Go app across desktop, browser and mobile.
Best for
- Inbox Triage: Letting Go sort email and draft replies each morning so you respond in a fraction of the time.
- Meeting Prep and Follow-Through: Crowdsourcing agendas before team syncs and auto-assigning tasks when meetings end.
- Live Call Support: Pulling key insights from a report in the side panel while answering unexpected questions on a partner call.
- Fact-Checked Writing: Drafting documents with inline suggestions and the Knowledge Checker verifying claims against company data.
- Project Tracking: Asking Go to build and maintain a team project tracker from connected tools like Jira or Asana.
- Team Q&A in Slack: At-mentioning Go in a channel for quick answers or tasks grounded in connected knowledge.