Partial failure in every tool

When a model’s tool call is mostly right, making it resend everything wastes tokens and invites new mistakes in the parts that were fine. So every tool keeps what was right, repairs what it reliably can, and asks the model only for what is still wrong.

The user’s rule of 2026-10-10 (stated with HARNESS-DRIVES): tools accept partial corrections and MERGE them; the model only resends what is wrong.

• A tool accepts a partial correction and merges it with the accepted parts.
• A tool auto-repairs everything it reliably can, and every repair is logged.
• A tool asks the model for the minimum.
• It is a principle for all tools, not a setting of one gate.

What is missing: not built yet. The tool layer (engine/src/tools/) has no shared partial-correction or merge mechanism; it is carried out with the smaller tool set of FEW-TOOLS.