Seven Harness Subsystems

A harness has to cover seven subsystems (loop, LLM integration, tools, memory and context, safety and permissions, orchestration, extensibility), which gives a shared vocabulary for saying which layer broke.

Evidence: weak

"The agent is broken" is not an actionable diagnosis. Once a team accepts that an agent is a model plus a harness, it still needs names for the parts of the harness, so that an incident can be pinned to a layer and the right owner or fix can be found.

The Wavestone source-code study of eleven harnesses proposes seven canonical subsystems:

  1. the agent loop;
  2. LLM (large language model) integration;
  3. tools and actions, the layer that descends from the agent-computer interface;
  4. memory and context;
  5. safety and permissions;
  6. orchestration;
  7. extensibility.

Two other 2026 taxonomies overlap heavily with it. The Agentic Harness Engineering (AHE) paper lists seven editable component types: system prompt, tool descriptions, tool implementations, middleware, skills, sub-agent configurations and long-term memory. A position paper on harness disclosure proposes a seven-layer ETCSOVG scheme (Execution, Tool, Context, Scheduling, Observability, Verification, Governance), which it pairs with a harness card for benchmark results. The Wavestone list has the advantage of being grounded in reading the source code of real harnesses, and its later sections on memory (§9), permissions (§10) and orchestration (§11) work as reference descriptions of how those layers are built in practice.

The evidence is weak in the sense that all three taxonomies are fresh 2026 preprints without peer review, and none has been validated as a diagnostic tool. Their agreement with each other is the main reason to trust the shape.

A practical use, offered as an implication rather than a sourced finding, is to tag every incident or failed run with one of the seven subsystems, so recurring faults can be counted per layer. Several patterns sit squarely on one layer: the layered agent permission stack is the safety layer, and the harness memory strategy spectrum is the memory layer.

Sources

  • Barbaste, Darrigol, Vu, Wiltberger (Wavestone AI Lab), arXiv 2609.00006, July 2026 preprint, §2.3 and Table 1 — https://arxiv.org/html/2609.00006v1
  • Lin, Liu, Pan et al., arXiv 2604.25850, 28 Apr 2026 preprint, editable component types — https://arxiv.org/html/2604.25850v1
  • Zhang, Wang, Ge, Xu, Hamm, Reddy, arXiv 2605.23950, 7 May 2026 position preprint, ETCSOVG taxonomy — https://arxiv.org/html/2605.23950v1