# Secondary source

Concept · [Building with AI](https://ecosystem.samcarlton.com/ai)

Also called: secondary sources, summary, summaries, second-hand source

A description of the original material rather than the material itself, such as a summary, a README or a [compaction](https://ecosystem.samcarlton.com/compaction) note. It is cheap to load but always leaves things out and can go stale, so important decisions should be checked against the [primary source](https://ecosystem.samcarlton.com/primary-source).

**For example:** A [handoff note](https://ecosystem.samcarlton.com/handoff-artifact) says the payment [bug](https://ecosystem.samcarlton.com/bug) is fixed, but the [agent](https://ecosystem.samcarlton.com/ai-agent) [checks](https://ecosystem.samcarlton.com/automated-check) the code before telling the [founder](https://ecosystem.samcarlton.com/founder), because the note is only a secondary source.

## Connects to (6)

- [Primary source](https://ecosystem.samcarlton.com/primary-source): The original material itself, such as the code, a full transcript or the raw data.
- [Compaction](https://ecosystem.samcarlton.com/compaction): Shrinking a long session by replacing its history with a summary and carrying on from that summary in a fresh context window.
- [Handoff artifact](https://ecosystem.samcarlton.com/handoff-artifact): The written document that carries a handoff, produced by one session for another to read.
- [Memory system](https://ecosystem.samcarlton.com/memory-system): A setup that tries to give an agent memory across sessions by saving notes to files or a database and loading them back when a new session…
- [Subagent](https://ecosystem.samcarlton.com/subagent): A second agent that the main agent starts to handle one piece of a job in its own separate session.
- [Hallucination](https://ecosystem.samcarlton.com/hallucination): When an AI model states something false or invented as though it were true.

Map view: https://ecosystem.samcarlton.com/secondary-source