> ## Documentation Index > Fetch the complete documentation index at: https://docs.usenexio.com/llms.txt > Use this file to discover all available pages before exploring further. # Glossary > Look up any term used in these docs, with a link to the page that explains it. Each platform term is defined once here and explained on its home page. | Term | Definition | Home page | | --------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------- | | Access plane | The part of Records that applies your own access rules to each person at request time: your identity provider, your HR directory, and your system of record's security groups and business-unit access. Every access change is audited. | [Access plane](/data-services/access) | | Acting principal | The person in your org that a server-side request acts for, sent in `X-Nexio-Acting-Principal`. It narrows what the API key allows. | [Authentication](/authentication) | | Action ledger | The append-only, per-organization record of governed write commands, from which current state is read back. | [Writes and the action ledger](/data-services/writes) | | Annotation | A rating and comment a person leaves on a run, on one part of its output, or on a conversation turn. | [Outcomes and annotations](/engines/outcomes-and-annotations) | | API key | The bearer credential on every request. It proves your org and one environment. There are two kinds: organization keys and scoped keys. | [Authentication](/authentication) | | Attachment | A file an end user adds to one turn of a conversation. | [Attachments](/conversations/attachments) | | Branch | One path through a conversation's messages, created when a user edits a message they already sent. | [Branching](/conversations/branching) | | Cancelled | A terminal run status: a cancel request stopped the run before it finished. | [Runs](/engines/runs) | | Capability | One permission a scoped key carries, such as `runs:write` or `records:read`. | [Authentication](/authentication#capabilities) | | Catalog | The read routes under `/api/v1/catalog` over served data, with citations to the source documents. | [Served data](/connections/served-data) | | Citation | A pointer from a served value to the document, and where known the page and region, it came from. | [Served data](/connections/served-data) | | Command | One governed write, such as `note.create` or `task.complete`, sent with its own idempotency key and appended to the action ledger. | [Writes and the action ledger](/data-services/writes) | | Connection | A configured link to one of your systems, such as a document library, a warehouse, a database, an API or an MCP server. Nexio operates it for you. | [Connections](/connections/overview) | | Conversation | One end user's exchange with a conversation instance: its messages, tool events and guardrail events. | [Conversations](/conversations/overview) | | Conversation instance | A configured assistant: instructions, tools, data access and guardrails, released as immutable versions. | [Conversations](/conversations/overview) | | Current read | How Records reads of connected data run: live against the warehouse's current data at request time, not held to a fixed instant, with the exceptions listed on Completeness and errors. `serving.as_of` records when it ran, and source changes can show between statements and between pages. | [Completeness and errors](/data-services/completeness) | | Defensibility packet | A customer-safe record of how a run's answer was sourced. | [Defensibility and trace](/engines/defensibility) | | Degraded | A terminal run status: the run finished with a usable answer, but part of it could not be produced, and the output says which part. | [Runs](/engines/runs) | | Diagnostic | A structured, non-fatal note on a run's output about input quality or a step that could not complete. | [Runs](/engines/runs) | | Effect | An action a subscription can take when an event matches, such as starting a run or sending a webhook. | [Automations](/events/automations) | | Engine | A configured capability that takes a typed input and returns a typed output. It has a stable slug, a type, a draft configuration and released versions. | [Engines](/engines/overview) | | Engine configuration | The JSON that defines an engine's behavior. Saving it changes the draft; runs use it once you publish a version, except three settings read from the saved configuration. | [Configuration and contract](/engines/configuration) | | Engine contract | The description of what an engine accepts and returns, shown on the engine's **Contract** page in the portal. | [Configuration and contract](/engines/configuration) | | Engine type | The kind an engine belongs to, which defines how it runs, how its configuration is validated and its schemas. Nexio ships a fixed set: `comparison`, `matching`, `entity_analysis`, `diligence`, `triage` and `opportunity`. | [Engines](/engines/overview) | | Engine version | An immutable, released snapshot of an engine's configuration, numbered `major.minor`. A run records the version it used. | [Versions and releases](/engines/versions) | | Enrichment source | A third-party data source that Nexio operates and an engine can consult during a run. | [Connections](/connections/overview) | | Environment | A partition of traffic inside your org: one `live` environment and up to 5 sandboxes. | [Environments](/environments) | | Eval set | A fixed set of reference cases used to measure an engine or assistant before a new version is released. | [Evaluation](/engines/evaluation) | | Extraction | Reading typed facts, each with a quote from its source, out of a document. | [Indexing and extraction](/connections/indexing-and-extraction) | | Extraction pass | A step that reads typed facts, each with a quote, from one class of document. A document is routed to a pass by its class. | [Indexing and extraction](/connections/indexing-and-extraction) | | Family | One named dataset on a plane, with a serve grain and a declared column set. Records reads any registered family through one route. | [Families](/data-services/families) | | Idempotency key | A value you send in `Idempotency-Key` so that a retried request returns the original result instead of repeating the work. | [Requests and errors](/reference/requests-and-errors) | | Indexing profile | The routing that decides which extraction pass reads each document class for a connection. A connection without its own uses the built-in profile. | [Indexing and extraction](/connections/indexing-and-extraction) | | Ingest source | A registered sender that may post events into your org, authenticated per source with a signature or, for an `ams360_ons` source, a shared code. | [Inbound events](/events/inbound) | | Lens | A read-only view of another person's data, requested with `X-Nexio-Records-Lens` by a caller whose own scope is `All` or `Platform`. | [Authority and scope](/data-services/scope) | | Org | Your organization in Nexio: the boundary for data, API keys and engines. | [Introduction](/introduction) | | Organization key | An API key issued in the portal for one environment, shaped `nx__...`. | [Authentication](/authentication) | | Outcome | An event your system reports about what happened after a run, such as a person accepting or overriding its answer. | [Outcomes and annotations](/engines/outcomes-and-annotations) | | Output | What an engine produces for a run, returned in the run's `output` field. | [Runs](/engines/runs) | | Plane | One source schema that Records reads, holding a set of families. | [Records](/data-services/overview) | | Platform event | An append-only record of a state change in your org, such as a sync finishing or a document changing. | [Platform events](/events/platform-events) | | Posture | The organization's access-plane setting (`dark`, `shadow` or `lit`) that decides where a person's authority comes from. | [Authority and scope](/data-services/scope) | | Profile | A documentation label, not an API object: one configured instance of the platform's primitives. | [Platform model](/platform-overview) | | Records | The platform's typed, authorized read and write layer over a connected system of record. Routes live under `/api/v1/records`. | [Records](/data-services/overview) | | Register | A paged, filterable list over one kind of record. Most registers also return totals and facets counted over the same authorized base population, and each sets its own facet filters; the activity register returns neither. | [Registers](/data-services/registers) | | Request bounds | The size and shape limits a run request must fit: string length, array items, object fields, depth and total bytes. | [Limits](/reference/limits) | | Review | A person checking work in the portal: extracted facts before they are trusted, or engine runs. | [Review](/connections/review) | | Run | One execution of an engine on one request. | [Runs](/engines/runs) | | Run cap | An optional monthly limit on how many runs your org can create. | [Limits](/reference/limits) | | Run status | Where a run is: `queued`, `processing`, or one of the terminal values `completed`, `degraded`, `failed`, `cancelled`. | [Runs](/engines/runs) | | Sandbox | An environment of kind `sandbox`, for building and testing. | [Environments](/environments) | | Sandbox fixture | A test scenario that drives a run of the fixture engine to a chosen terminal state with no provider calls. | [Sandbox fixtures](/reference/sandbox-fixtures) | | Scope | The records a person may read, resolved before a Records read runs. | [Authority and scope](/data-services/scope) | | Scoped key | An API key issued by Nexio, shaped `nxsk_v1_...`, bound to one environment, a set of engines and a set of capabilities. | [Authentication](/authentication) | | Seat | A person's authority in one organization, derived at request time from your own systems. | [Access plane](/data-services/access) | | Served data | Typed, versioned records Nexio extracts from a connection's documents, effective-dated and carrying citations to the source documents. | [Served data](/connections/served-data) | | Slug | A short, URL-safe identifier, such as an engine slug (`vendor-review`) or an environment slug (`dev`). | [Engines](/engines/overview) | | Subscription | A rule Nexio runs for your org: when a matching event arrives, perform an effect. | [Automations](/events/automations) | | Supersession | A corrected result attached to a run that already finished. | [Defensibility and trace](/engines/defensibility) | | System of record | The system your organization treats as the source of truth for its records. Nexio reads it, mostly through a replica in your warehouse, and does not write to it. | [Records](/data-services/overview) | | Trace ID | A 32-character hex identifier for one request, stamped on a run as `trace_id` and returned in `x-request-id` when you did not send your own request ID. Quote it to support. | [Requests and errors](/reference/requests-and-errors) | | Turn | One exchange in a conversation: a user message and the answer the assistant streams back. | [Turns and streaming](/conversations/turns-and-streaming) | | Verification tier | How strongly a delivered fact is backed: checked by a person, agreed by two models, or read once. | [Review](/connections/review) | | Webhook | A signed HTTP call Nexio sends to your endpoint, for example when a run finishes. | [Webhooks](/api-reference/webhooks/overview) |