FIELD NOTE / X
One slide. Three different contracts.
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One slide. Three different contracts.
Day 103 - 2027-01-08 PT target - X
Video caption
One slide. Three different contracts. False interchange starts with merged vocabulary. A tools audit is not a kernel decision. Make the map visible. Narration uses Eric's authorized AI voice clone. #EricFieldNotes
Full written post / accessibility read
Builders keep collapsing three contracts into one agent protocol slide. A box labeled MCP, a box labeled harness, a box labeled sandbox, and one arrow that pretends they are interchangeable. They sit on different layers and fail differently when you review them as one thing.
MCP is the tools and data plane. UHP, still a draft dated September twelfth twenty twenty six, is a product to harness job contract. Execution substrate is where the agent runs. Merging them early creates false interchange and false security reviews.
Ask what the host exposes, how a product starts and cancels work, and where the process is isolated. Those are three reviews. When the seams blur, a tools audit stands in for a job lifecycle review, or a container flag checklist stands in for a kernel boundary decision.
Put model client, harness driver, tool plane, and substrate on separate rows in the architecture doc. My working rule is simple. Name the layer before you merge the stack, then measure each seam on its own claim class.
Narration uses Eric's authorized AI voice clone.
#EricFieldNotes
Four-beat scene transcript
1. One slide. Three different contracts.
Builders keep collapsing three contracts into one agent protocol slide. A box labeled MCP, a box labeled harness, a box labeled sandbox, and one arrow that pretends they are interchangeable. They sit on different layers and fail differently when you review them as one thing.
Visual: MCP, harness job, and substrate are not synonyms.
2. Name the layer first.
MCP is the tools and data plane. UHP, still a draft dated September twelfth twenty twenty six, is a product to harness job contract. Execution substrate is where the agent runs. Merging them early creates false interchange and false security reviews.
Visual: False interchange starts with merged vocabulary.
3. Separate the review questions.
Ask what the host exposes, how a product starts and cancels work, and where the process is isolated. Those are three reviews. When the seams blur, a tools audit stands in for a job lifecycle review, or a container flag checklist stands in for a kernel boundary decision.
Visual: A tools audit is not a kernel decision.
4. Make the map visible.
Put model client, harness driver, tool plane, and substrate on separate rows in the architecture doc. My working rule is simple. Name the layer before you merge the stack, then measure each seam on its own claim class.
Visual: One slide, three named rows.