Aditya Karnam · AI Research Notes
Free practical systems guide · Edition 1
Building a Coding Agent Harness
From model calls to a safe, observable, evaluable runtime. Build the runnable Rust core, then study how its boundaries map to Quecto in production.By Aditya Karnam and Arjun Jaggi. Chapters 2–5 develop a compact teaching harness you can run; Chapters 6–12 clearly mark production-runtime concerns as design studies.
Pages75
Chapters14
ImplementationRust
LicenseMIT
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The PDF is embedded below. If your browser does not display it inline, use Download the PDF above or open the standalone HTML edition.What You Will Build
A small, testable harness — one boundary at a time
The reference crate keeps the executable core deliberately small, then uses the production Quecto project to ground the wider runtime architecture.Runnable coreModel transport, a bounded tool loop, typed tools, repository context, and execution policy, assembled and tested in the book's Rust crate.
Production concernsVerification, sessions, configuration, MCP, telemetry, and evaluation—explicitly labeled as design extensions where the compact crate does not implement them.
Quecto as evidenceA source-mapped tour of the larger open-source Rust system, including the production crates, features, and boundaries behind the examples.
For working engineersShort code excerpts, failure modes, invariants, build checkpoints, and exercises make the guide useful at the terminal, not just on the shelf.
Contents
Fourteen chapters, from API boundary to production system
- 01The Harness Is the System
- 02One Model Call, No Framework
- 03The Bounded Agent Loop
- 04Typed, Unsafe-Free Communication
- 05Execution Policy and Approval Gates
- 06Verification as a Completion Gate
- 07Context and Instruction Loading
- 08Sessions and State Management
- 09Profiles and Security Gates
- 10MCP: Model Context Protocol
- 11Observability and Telemetry
- 12Evaluation and Benchmarks
- 13The Complete Reference Harness
- 14Appendix: The Quecto Reference
The proof project