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Building a Local-First Agent Framework in Rust (Part 19): Measuring Behavior With eval

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 19: Measuring Behavior With eval By Chapter 18, the model boundary has a clearer shape. The system prompt tells the model what envelope to emit. The parser tolerates the common

Building a Local-First Agent Framework in Rust (Part 18): Teaching the Model

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 18: Teaching the Model: The System Prompt and Robust Parsing By Chapter 17, abcb run has become a real loop. It can keep a session, call tools, deny tools, record

Building a Local-First Agent Framework in Rust (Part 17): The Run Summary

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 17: The Run Summary: A Read-Model From the Log Chapter 14 gave the loop an event log. Chapter 16 added another kind of event: a denied tool call. By

Building a Local-First Agent Framework in Rust (Part 16): Approval: Gating Tool Calls

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 16: Approval: Gating Tool Calls By the end of Chapter 15, the agent could remember notes across runs. It could call tools, write event logs, keep sessions on disk, and

Building a Local-First Agent Framework in Rust (Part 15): Memory Tiers: Notes

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 15: Memory Tiers: Notes Chapter 14 gave the agent run an audit trail. Every run can now leave an events.jsonl file inside its session directory. That file is about

Building a Local-First Agent Framework in Rust (Part 14): Recording the Loop

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 14: Recording the Loop: Events as JSONL Chapter 13 gave each run a place to live. A session now has a creation time, an id, and a directory under .abcb/

Building a Local-First Agent Framework in Rust (Part 13): Time, Identity, and Sessions on Disk

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 13: Time, Identity, and Sessions on Disk So far, a session has mostly been a conversation container. It held an id and a list of messages, but the id was

Building a Local-First Agent Framework in Rust (Part 12): Health Checks, doctor, and Testing HTTP

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 12: Health Checks, doctor, and Testing HTTP In the previous chapter, abcb crossed an important line. The provider stopped being only an in-process mock and became something that could

Building a Local-First Agent Framework in Rust (Part 11): Going Async and Over HTTP

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 11: Going Async and Over HTTP Until now, abcb has been living in a controlled room. The provider was a mock. It returned scripted strings from memory. That was not

Building a Local-First Agent Framework in Rust (Part 10): Configuration With TOML

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 10: Configuration With TOML So far, abcb has been mostly self-contained. The mock provider lives in the process. The default notes file is hardcoded. The loop step limit is

Building a Local-First Agent Framework in Rust (Part 9): Failing Gracefully With Recovery

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 9: Failing Gracefully With Recovery Chapter 8 gave abcb a loop. The framework could create a session, send it to the provider, parse the model's structured output, execute

Building a Local-First Agent Framework in Rust (Part 8): The Agent Loop and Session Continuity

See Part 0 for the latest table of contents and sample code. New chapters will be added over time. Chapter 8: The Agent Loop and Session Continuity Chapter 7 gave abcb one clean step. The framework could ask the provider for one assistant message, parse that message as ModelOutput, and