> ## Documentation Index > Fetch the complete documentation index at: https://docs.stacknext.space/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > StackNext documentation is written for developers using StackNext in a Next.js App Router project. Use the getting-started and guides sections to install and operate the product, and the reference section for CLI, configuration, MCP and package surfaces. Version-matched package API reference ships inside each npm package under node_modules/@stacknext//docs/ and is preferred over this site for installed-version APIs. Diagnostic findings are evidence, not confirmed root causes; regression comparisons are deterministic and report-only. Contributor and repository-maintenance documentation is not part of this site. # Core concepts > The sample, traces, coverage, diagnostics, snapshots and regression records that StackNext exposes. ## Sample and retention A **sample** is the telemetry currently held in the collector's in-memory store. `collector.maxSpans` limits spans. Error and query buffers have separate capacities derived from that setting; each type can hold up to its own capacity. `collector.retentionMs` bounds retention (10 minutes by default). When capacity or retention removes data, the store records drops. Every count and finding describes this sample, not all activity since the app started. See [configuration](https://docs.stacknext.space/reference/configuration.md). ## Requests, traces and spans A **request** is an incoming HTTP request to the Next.js app. A **trace** is the tree of spans produced while handling it. StackNext preserves documented Next.js span types and parent ids; unknown span types remain visible as verbose evidence rather than being guessed. A span's duration includes its children. To find where time is spent, compare child spans or inspect self time; never sum a parent and its child as if they ran sequentially. ## Queries and errors Drizzle query events never include durations, so `durationMs` is `null`, not zero. Prisma events can include a duration. SQL text is redacted; bind parameters are neither read nor sent. Request errors arrive through the Next.js error hook with a redacted message and stack. A trace link may be exact (active span context) or a route/method plus 30-second fallback. ## Coverage is evidence **Instrumentation coverage** answers what the current sample observed for a feature such as fetch spans, database adapters, custom spans, Server Actions or verbose tracing. Statuses include `observed`, `active`, `configured`, `not-observed`, `unknown` and `unsupported`. They are not a percentage or health score, and absence is not proof that a feature is broken. See [instrumentation coverage](https://docs.stacknext.space/instrumentation-coverage.md). ## Diagnostics are deterministic findings **Diagnostics** are six conservative rules over the current sample. A finding has a deterministic id, a rule, a status (`possible`, `observed` or `insufficient-evidence`), a severity, bounded evidence and limitations. `possible` means the pattern is consistent with a problem; `observed` means the measurement exists. Neither proves a root cause. See [diagnostics](https://docs.stacknext.space/guides/diagnostics.md). ## Snapshots are frozen evidence A **snapshot** is a versioned, redacted copy of one sample saved under `.stacknext/snapshots`. It is never replayed into the live store. Snapshot reads use a detached store and carry no live diagnostics or coverage. Manual and imported snapshots never rotate automatically. See [snapshots](https://docs.stacknext.space/guides/snapshots.md). ## Regression records A **capture run** contains Playwright scenarios and their verified runtime samples. A **baseline** is an immutable saved run. A **comparison** matches scenarios by stable id and traces/spans by normalized keys, then reports `improved`, `regressed`, `unchanged` or `inconclusive` with a separate severity. A sample is verified only when the collector found the injected trace and a server span parented to the injected span id. See [regression testing](https://docs.stacknext.space/regression-testing.md). ## Redaction Redaction happens twice: in the app process before enqueueing, and in the collector before storing. URLs keep the path only; sensitive keys become `[redacted]`; error text is sanitized; resource attributes use an allowlist. Captured files are re-redacted. See [privacy](https://docs.stacknext.space/privacy.md). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.