From the free book Delta: Closing the Specification Gap (Dhuri, 2026). The PDF is the canonical edition — figures, tables, and code formatting are simplified online.
F Glossary Specification Gap The distance between what you intend for the AI to produce and what it actually produces. Three components: Domain Gap, Context Gap, Constraint Gap. The central concept of this book. Specification Frame Role + Context + Task + Constraints in XML tags. See Chapter 3. Specification Engineering The discipline of defining precisely what a system should do in machineexecutable form. The most durable career investment for engineers in 2026. Critic Frame A prompting technique that makes validation structurally impossible by instructing the model to find problems, not evaluate quality. Evidence Brief XML-structured incident evidence document assembled before a debugging prompt. Six sections: service, environment, frequency, stack trace, code at failure, recent changes, metrics, already-ruled-out. Specification Drift Multi-agent failure where orchestrator reformulates original specification. Prevented by passing spec verbatim as immutable XML.
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MCP Model Context Protocol (Anthropic, 2024). Open standard for connecting AI to tools and data sources. Host + Client + Server architecture. CLAUDE.md Project specification file read by Claude Code before any action. Defines stack, patterns, hard constraints. Result<T> Discriminated union: success value or failure code+message. For all business rule outcomes. See Appendix B. Money<T> Type-safe monetary value. Enforces decimal arithmetic. Prevents double/float at compile time. See Appendix B. Prompt Injection Attack where crafted input overrides AI system instructions. Direct: user input. Indirect: retrieved content. Prevented by structural isolation. Four-Stage Pipeline Domain Model Contracts Implementation Tests. Humans own Stages 1-2. Agents execute 3-4. Prompt Caching API feature caching stable prompt prefixes at ~90% cost reduction. Implemented with cache_control ephemeral markers.