> ## Documentation Index
> Fetch the complete documentation index at: https://docs.threadify.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Core concepts

> The pieces of execution intelligence and how they fit together.

| Concept                                                  | Responsibility                                           |
| -------------------------------------------------------- | -------------------------------------------------------- |
| [Thread](/core-concepts/threads)                         | One execution, optionally governed by a contract version |
| [Step](/core-concepts/tracking-workflows)                | A recorded operation, outcome, and context               |
| [Contract](/core-concepts/creating-contracts)            | Deterministic rules for that execution                   |
| [Execution wait](/core-concepts/execution-waits)         | Permission before acting or validation after reporting   |
| [Sub-step](/core-concepts/sub-steps)                     | A detail within an operation                             |
| [Reference](/core-concepts/external-references)          | A business identifier or explicit run correlation        |
| [Entity profile](/core-concepts/entity-profiles)         | History and configured metrics across an entity's runs   |
| [Notification](/core-concepts/notifications/subscribing) | An event your application can react to                   |
| [Integrity verification](/things-to-know/hash-chain)     | Check the recorded chain for tampering                   |

Threadify records and checks execution. Your services and agent tools perform
the work, and decide how to act on permission or validation results.