diff --git a/README.md b/README.md
index 4b2c858..a29f2ec 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ $label = Markdown::github()->toInlineHtml('Install **Alto**');
 ```
 
 See [Installation](docs/installation.md), [HTML](docs/conversion/html.md),
-[Profiles](docs/documents/profiles.md), and [Security](docs/engine/security.md) to choose the
+[Profiles](docs/documents/profiles.md), and [Security](docs/security.md) to choose the
 right language and HTML policy.
 
 ## Open a document when you need more
@@ -118,7 +118,7 @@ if ($file->hasChanges()) {
 ```
 
 Source ranges use original byte offsets. `toMarkdown()` preserves unchanged
-bytes, line endings, and a UTF-8 BOM. Alto rejects an edit when it cannot apply
+bytes, line endings, and a UTF-8 BOM. ALTO rejects an edit when it cannot apply
 it safely under the documented V1 contract.
 
 The documentation covers this in more depth: [Queries](docs/documents/queries.md)
@@ -133,15 +133,26 @@ to enforce content and style policies.
 Trusted extensions add custom blocks, leaf inlines, native and link-aware HTML
 decoration, document render projections, lint, formatting, metrics,
 heading-level projection, permalinks, and generated tables of contents through
-compiled contracts. Read [Extensions](docs/extensions/index.md) and
+compiled contracts. Read [Extensions](docs/extensions.md) and
 [Compatibility](docs/extensions/compatibility.md) for the extension contracts
-and migration notes from historical Alto CommonMark extensions.
+and migration notes from historical ALTO CommonMark extensions.
 
 ## Documentation
 
-- [Documentation index](docs/index.md): browse the complete guide set.
-- [API reference](docs/api/index.md) and [Exceptions](docs/api/exceptions.md): the
-  public surface and recovery contracts.
+- [Installation](docs/installation.md): install the package and verify the runtime.
+- [Getting started](docs/getting-started.md): render and inspect a document.
+- [Conversion](docs/conversion.md): produce HTML or Markdown output.
+- [Documents](docs/documents.md): query, measure, and edit source-backed content.
+- [Quality](docs/quality.md): lint, fix, and format Markdown.
+- [Extensions](docs/extensions.md): choose bundled capabilities or create one.
+- [Syntax](docs/syntax.md): add authoring syntax.
+- [Rendering](docs/rendering.md): control document and HTML output.
+- [Resources](docs/resources.md): resolve imported, included, and embedded content.
+- [Security](docs/security.md): define HTML, input, and resource boundaries.
+- [Errors](docs/errors.md): recover from parse, edit, resource, and file failures.
+- [Performance](docs/performance.md): select and measure the processing path.
+- [Compliance](docs/compliance.md): review supported Markdown specifications.
+- [Documentation index](docs/index.md): browse every guide.
 
 ## Contributing
 
diff --git a/docs/api/documents.md b/docs/api/documents.md
deleted file mode 100644
index edeb978..0000000
--- a/docs/api/documents.md
+++ /dev/null
@@ -1,39 +0,0 @@
-# Documents API
-
-Factories create one of two document contracts: an in-memory
-`MarkdownDocument` or a path-backed `MarkdownFile`.
-
-## MarkdownFactory
-
-| Method | Return | Purpose |
-| --- | --- | --- |
-| `profile()` | `Profile` | Return the compiled language profile. |
-| `with(ExtensionInterface ...$extensions)` | `self` | Return a factory with trusted extensions. |
-| `fromString(string $source, ?ParseOptions $options = null)` | `MarkdownDocument` | Parse an in-memory document. |
-| `open(string $path, ?ParseOptions $options = null)` | `MarkdownFile` | Read and parse a file. |
-| `toHtml(...)` | `string` | Render block Markdown directly. |
-| `toInlineHtml(...)` | `string` | Render an inline fragment directly. |
-| `builder()` | `MarkdownBuilder` | Start a document builder. |
-| `fragment()` | `MarkdownFragmentBuilder` | Start a fragment builder. |
-
-## MarkdownDocument
-
-The document exposes its `profile()` and `model()`, typed accessors, `query()`,
-`ensure()`, `lint()`, `fix()`, `format()`, and `stats()`. Output methods are
-`toMarkdown()` and `toHtml()`. `hasChanges()` and `diff()` inspect pending
-source edits.
-
-```php
-$document = $factory->fromString($source);
-
-if ($document->hasChanges()) {
-    echo $document->diff()->toUnifiedString();
-}
-```
-
-## MarkdownFile
-
-`MarkdownFile` adds `path()`, `save()`, and `saveAs()`. Saving may reject a
-changed, missing, symbolic-link, or unauthorized target. See
-[Editing](editing.md) for persistence contracts and [Exceptions](exceptions.md)
-for recoverable failures.
diff --git a/docs/api/editing.md b/docs/api/editing.md
deleted file mode 100644
index 5753b75..0000000
--- a/docs/api/editing.md
+++ /dev/null
@@ -1,38 +0,0 @@
-# Editing API
-
-Editing APIs either build new Markdown or record validated patches against an
-existing source.
-
-## Builders
-
-`MarkdownBuilder` provides `heading()`, `h1()`, `h2()`, `paragraph()`,
-`codeBlock()`, `unorderedList()`, `orderedList()`, `blockquote()`, and
-`thematicBreak()`. Finish with `document()` or `toMarkdown()`.
-
-```php
-$markdown = $factory->builder()
-    ->h1('Guide')
-    ->paragraph('Start here.')
-    ->toMarkdown();
-```
-
-`MarkdownFragmentBuilder` creates content intended for insertion rather than a
-standalone document.
-
-## Pending patches
-
-Typed handle mutations update the in-memory model immediately and add source
-operations to the document journal. `toMarkdown()` lowers pending operations;
-`diff()` returns a `Diff` whose `toUnifiedString()` method is suitable for a
-preview.
-
-## SaveOptions
-
-`MarkdownFile::save()` replaces the opened file. `saveAs()` targets another
-path. `SaveOptions` controls compare-before-write and related persistence
-policies. Atomic replacement, permission preservation, line-ending retention,
-and conflict checks remain available through the file contract.
-
-Catch the file exceptions described in [Exceptions](exceptions.md) at the
-application boundary. See [Editing](../documents/editing.md) for complete
-source-preserving workflows.
diff --git a/docs/api/extensions.md b/docs/api/extensions.md
deleted file mode 100644
index ec4373b..0000000
--- a/docs/api/extensions.md
+++ /dev/null
@@ -1,31 +0,0 @@
-# Extensions API
-
-An extension has a stable name and implements only the public capability
-interfaces required by its behavior.
-
-| Capability | Public contract |
-| --- | --- |
-| Syntax | `BlockExtensionInterface`, `InlineExtensionInterface` |
-| HTML | `HtmlDecoratorExtensionInterface` |
-| Projection | `DocumentTransformExtensionInterface` |
-| Lint | `LintExtensionInterface` |
-| Format | `FormatterExtensionInterface` |
-| Statistics | `StatsExtensionInterface` |
-| Resources | `ResourceResolver` |
-
-Definitions, contexts, and value objects under `Alto\Markdown\Extension` are
-public unless marked `@internal`. Parser tapes, compact node IDs, compiler
-caches, and internal dispatch objects are not extension contracts.
-
-```php
-$extended = $factory->with($firstExtension, $secondExtension);
-```
-
-The returned factory is immutable. Extension compilation rejects invalid
-names, duplicate or incompatible definitions, and unavailable parser triggers
-before processing a document.
-
-Read [Extension points](../extensions/extension-points.md) to choose a contract,
-[Custom extension](../extensions/custom.md) for an implementation, and
-[Compatibility](../extensions/compatibility.md) before declaring a package
-version range.
diff --git a/docs/api/index.md b/docs/api/index.md
deleted file mode 100644
index 95eec51..0000000
--- a/docs/api/index.md
+++ /dev/null
@@ -1,32 +0,0 @@
-# API reference
-
-The public API is organized by application task. Types marked `@internal` in
-source are not part of the package contract.
-
-## Entry points
-
-`Markdown::commonmark()`, `Markdown::gfm()`, and `Markdown::github()` return a
-`MarkdownFactory` for the selected syntax profile. A factory can render a
-string directly, create a document, open a file, start a builder, or install
-trusted extensions.
-
-```php
-use Alto\Markdown\Markdown;
-
-$factory = Markdown::github();
-$document = $factory->fromString("# Guide\n");
-```
-
-## Reference domains
-
-- [Documents](documents.md): `MarkdownFactory`, `MarkdownDocument`, and
-  `MarkdownFile`.
-- [Nodes](nodes.md): headings, sections, links, images, code, and front matter.
-- [Queries](queries.md): collections, generic selectors, and statistics.
-- [Editing](editing.md): builders, source patches, diffs, and persistence.
-- [Extensions](extensions.md): profiles and public extension capabilities.
-- [Exceptions](exceptions.md): argument, parse, render, resource, and file
-  failures.
-
-Use the guide pages for decisions and workflows. These reference pages define
-callable contracts and observable boundaries.
diff --git a/docs/api/queries.md b/docs/api/queries.md
deleted file mode 100644
index 6703b65..0000000
--- a/docs/api/queries.md
+++ /dev/null
@@ -1,37 +0,0 @@
-# Queries API
-
-Documents provide typed accessors for common questions and `MarkdownQuery` for
-core or extension node kinds.
-
-## Typed accessors
-
-`title()`, `headings()`, `section()`, `sections()`, `links()`, `images()`,
-`codeBlocks()`, and `frontMatter()` return typed handles or lazy collections.
-
-## Collection
-
-`Collection` implements `Countable`, `IteratorAggregate`, and lazy operations:
-
-| Method | Result |
-| --- | --- |
-| `first()` | First item or `null`. |
-| `count()` | Number of matching items. |
-| `all()` | Materialized result array. |
-| `filter()` | Derived lazy collection. |
-
-## MarkdownQuery
-
-`kind()` adds an OR node-kind selector. `where()` adds an AND predicate.
-`get()` returns matching handles in source order.
-
-```php
-$tablesAndParagraphs = $document->query()
-    ->kind('paragraph')
-    ->kind('gfm:table')
-    ->get();
-```
-
-`stats()` returns `DocumentStats`, including headings, sections, links, images,
-code, words, reading time, tables, and extension metrics. See
-[Queries](../documents/queries.md) and [Statistics](../documents/statistics.md)
-for selection and counting semantics.
diff --git a/docs/engine/compliance.md b/docs/compliance.md
similarity index 99%
rename from docs/engine/compliance.md
rename to docs/compliance.md
index ddfb7be..cc0f144 100644
--- a/docs/engine/compliance.md
+++ b/docs/compliance.md
@@ -25,7 +25,7 @@ The published package carries the conformance fixtures and runs them with the
 rest of the suite:
 
 ```bash
-composer tests
+composer test
 ```
 
 The full quality gate also runs static analysis and style checks on top of the
diff --git a/docs/conversion.md b/docs/conversion.md
new file mode 100644
index 0000000..3d61bd0
--- /dev/null
+++ b/docs/conversion.md
@@ -0,0 +1,21 @@
+# Conversion
+
+Convert Markdown directly when the application only needs one output. Open a
+document first when the same parsed structure will also be queried, edited,
+linted, or rendered more than once.
+
+```php
+use Alto\Markdown\Markdown;
+
+$html = Markdown::github()->toHtml("# Guide\n\nRead **carefully**.\n");
+```
+
+## Output
+
+- [HTML](conversion/html.md): render blocks or inline fragments with an explicit
+  HTML policy.
+- [Markdown](conversion/markdown.md): preserve original source or produce
+  normalized Markdown.
+
+Direct conversion avoids retaining a document object. Document output preserves
+unchanged source bytes until an operation explicitly normalizes them.
diff --git a/docs/conversion/html.md b/docs/conversion/html.md
index d500ccf..f7bfb35 100644
--- a/docs/conversion/html.md
+++ b/docs/conversion/html.md
@@ -46,5 +46,5 @@ The default policy escapes raw HTML and filters unsafe URL schemes. Pass a
 `RenderOptions` value only when the application has an explicit reason to use
 another policy.
 
-Read [Security](../engine/security.md) before enabling authored HTML. Continue
+Read [Security](../security.md) before enabling authored HTML. Continue
 with [Markdown](markdown.md) when output must remain Markdown.
diff --git a/docs/documents.md b/docs/documents.md
new file mode 100644
index 0000000..0c0c51b
--- /dev/null
+++ b/docs/documents.md
@@ -0,0 +1,40 @@
+# Documents
+
+A document retains the parsed model and original source. Use it when an
+application needs to inspect, reuse, measure, or change Markdown without
+rewriting unrelated content.
+
+```php
+use Alto\Markdown\Markdown;
+
+$document = Markdown::github()->fromString("# Guide\n\nRead the docs.\n");
+$title = $document->title()?->text();
+```
+
+`$title` is `Guide`.
+
+## Guides
+
+- [Profiles](documents/profiles.md): choose CommonMark, GFM, or GitHub syntax.
+- [Queries](documents/queries.md): find headings, sections, links, and code.
+- [Statistics](documents/statistics.md): compute an immutable document summary.
+- [Editing](documents/editing.md): make source-preserving changes and save files.
+- [Nodes](documents/nodes.md): inspect and mutate typed handles.
+
+## Entry points
+
+| Method | Return | Purpose |
+| --- | --- | --- |
+| `profile()` | `Profile` | Return the compiled language profile. |
+| `with(ExtensionInterface ...$extensions)` | `self` | Return a factory with trusted extensions. |
+| `fromString(string $source, ?ParseOptions $options = null)` | `MarkdownDocument` | Parse an in-memory document. |
+| `open(string $path, ?ParseOptions $options = null)` | `MarkdownFile` | Read and parse a file. |
+| `toHtml(...)` | `string` | Render block Markdown directly. |
+| `toInlineHtml(...)` | `string` | Render an inline fragment directly. |
+| `builder()` | `MarkdownBuilder` | Start a document builder. |
+| `fragment()` | `MarkdownFragmentBuilder` | Start a fragment builder. |
+
+`MarkdownDocument` exposes typed accessors, `query()`, `ensure()`, `lint()`,
+`fix()`, `format()`, `stats()`, `toMarkdown()`, and `toHtml()`.
+`MarkdownFile` adds `path()`, `save()`, and `saveAs()`. See
+[Errors](errors.md) for recoverable parse, edit, resource, and file failures.
diff --git a/docs/documents/editing.md b/docs/documents/editing.md
index 1c7f837..447251e 100644
--- a/docs/documents/editing.md
+++ b/docs/documents/editing.md
@@ -27,6 +27,7 @@ The result changes only the section body:
 ## Install
 
 Run Composer.
+
 ```
 
 Available typed edits:
@@ -218,6 +219,10 @@ Compare-before-write protects against silently replacing bytes changed by
 another editor or process. It is optimistic conflict detection, not a
 filesystem lock.
 
+After a conflict, keep the pending diff for review, reopen the current file,
+and reapply the intended change against its updated content. Do not disable
+comparison merely to force a stale write over another editor's changes.
+
 Protected `saveAs()` can create a new target but refuses to replace an existing
 file that this document did not open. The default comparison option remains
 `false`, so enable it explicitly when concurrent changes are possible.
@@ -252,5 +257,5 @@ mode handling is platform-limited. Use `atomic: false` only when retaining the
 existing inode and its metadata is more important than all-or-nothing
 replacement. A non-atomic write can leave partial content after an I/O failure.
 
-See [Exceptions](../api/exceptions.md) for conflicts, stale handles, missing sections, and
+See [Errors](../errors.md) for conflicts, stale handles, missing sections, and
 unsupported edits.
diff --git a/docs/api/nodes.md b/docs/documents/nodes.md
similarity index 94%
rename from docs/api/nodes.md
rename to docs/documents/nodes.md
index 7676c66..337c3d5 100644
--- a/docs/api/nodes.md
+++ b/docs/documents/nodes.md
@@ -1,4 +1,4 @@
-# Nodes API
+# Nodes
 
 Typed handles expose semantic values and the mutations Alto can lower safely
 to source patches.
@@ -27,4 +27,4 @@ query the current document again.
 
 Generic block movement and insertion accept only direct children of the
 document root. Typed mutations retain their own documented boundaries. See
-[Editing](../documents/editing.md) for worked operations.
+[Editing](editing.md) for worked operations.
diff --git a/docs/api/exceptions.md b/docs/errors.md
similarity index 97%
rename from docs/api/exceptions.md
rename to docs/errors.md
index 0bf15d1..6bf9527 100644
--- a/docs/api/exceptions.md
+++ b/docs/errors.md
@@ -63,7 +63,7 @@ Use the precise subtype when its recovery is different:
 Parser limit subclasses expose the configured and attempted values. File
 exceptions expose the original application path through `path`. Resource limits
 and their exact counting rules are documented in
-[Security](../engine/security.md#bound-parsing-and-file-access).
+[Security](security.md#bound-parsing-and-file-access).
 
 Unknown generic node kinds also raise an Alto domain exception. Construct
 factories with custom extensions during application startup rather than after
@@ -122,5 +122,5 @@ own symlink policy. Existing non-regular targets are rejected. A relative path
 is anchored to its canonical parent when opened or adopted by `saveAs()`, but
 that does not replace application authorization. Permission inspection or
 restoration failures abort atomic replacement and preserve the pending diff.
-See [Editing](../documents/editing.md#preview-and-save) for the complete
+See [Editing](documents/editing.md#preview-and-save) for the complete
 persistence contract.
diff --git a/docs/extensions.md b/docs/extensions.md
new file mode 100644
index 0000000..8e171c6
--- /dev/null
+++ b/docs/extensions.md
@@ -0,0 +1,51 @@
+# Extensions
+
+Extensions add trusted syntax, rendering, transformations, analysis, or
+resource-backed behavior to an immutable factory profile. Install only the
+capabilities required by the document format.
+
+```php
+use Alto\Markdown\Extension\Footnote\FootnoteExtension;
+use Alto\Markdown\Extension\Highlight\HighlightExtension;
+use Alto\Markdown\Markdown;
+
+$factory = Markdown::github()->with(
+    new FootnoteExtension(),
+    new HighlightExtension(),
+);
+```
+
+Choose bundled extensions by outcome:
+
+- [Syntax](syntax.md) adds author-facing Markdown constructs.
+- [Rendering](rendering.md) projects or decorates document output.
+- [Resources](resources.md) resolves bounded external content.
+
+## Development
+
+- [Compatibility](extensions/compatibility.md): understand extension versioning.
+- [Extension points](extensions/extension-points.md): select the correct contract.
+- [Custom extension](extensions/custom.md): register trusted application behavior.
+
+## Capabilities
+
+An extension has a stable name and implements only the public capabilities its
+behavior requires.
+
+| Capability | Public contract |
+| --- | --- |
+| Syntax | `BlockExtensionInterface`, `InlineExtensionInterface` |
+| HTML | `HtmlDecoratorExtensionInterface` |
+| Projection | `DocumentTransformExtensionInterface` |
+| Lint | `LintExtensionInterface` |
+| Format | `FormatterExtensionInterface` |
+| Statistics | `StatsExtensionInterface` |
+| Resources | `ResourceResolver` |
+
+Definitions, contexts, and value objects under `Alto\Markdown\Extension` are
+public unless marked `@internal`. Parser tapes, compact node IDs, compiler
+caches, and internal dispatch objects are not extension contracts.
+
+The returned factory is immutable. Extension compilation rejects invalid
+names, duplicate or incompatible definitions, and unavailable parser triggers
+before processing a document. Extensions execute as trusted application code.
diff --git a/docs/extensions/compatibility.md b/docs/extensions/compatibility.md
index 2d87ea7..70ae6b3 100644
--- a/docs/extensions/compatibility.md
+++ b/docs/extensions/compatibility.md
@@ -1,6 +1,6 @@
 # Compatibility
 
-Alto extensions depend only on Alto's public contracts. Extensions written for
+ALTO extensions depend only on ALTO's public contracts. Extensions written for
 League CommonMark, Parsedown, or the historical `alto/commonmark` packages use
 different parser and renderer APIs. They cannot be passed directly to
 `MarkdownFactory::with()`.
@@ -62,7 +62,7 @@ Alto does not emit deprecation warnings from parser or renderer hot paths.
 Security fixes may narrow unsafe behavior in a patch release when preserving it
 would keep users exposed. Such changes require an explicit security notice.
 
-Package authors should test the lowest and newest Alto versions allowed by
+Package authors should test the lowest and newest ALTO versions allowed by
 their Composer constraint. Invalid definitions and callback results raise
 `InvalidExtensionException`; arbitrary exceptions thrown by application
 callbacks remain unchanged.
@@ -90,19 +90,19 @@ Map new block syntax to `BlockExtensionInterface`, leaf inline syntax to
 `HtmlDecoratorExtensionInterface`, and document-wide output decisions to
 `DocumentTransformExtensionInterface`. Do not adapt or expose the foreign AST.
 
-Every historical Alto CommonMark feature has a native replacement:
+Every historical ALTO CommonMark feature has a native replacement:
 
 | Historical package | Native Alto replacement | Migration note |
 | --- | --- | --- |
-| `alto/commonmark-code-block-title` | [`CodeBlockTitleExtension`](index.md) | Use the typed title policy |
-| `alto/commonmark-content-slicer` | [`ContentSlicerExtension`](index.md) | `minLevel` is the first heading level that opens a section |
-| `alto/commonmark-heading-level` | [`HeadingLevelExtension`](index.md) | Use `HeadingLevelPolicy::map()`, `shift()`, or `using()` |
-| `alto/commonmark-import` | [`ImportExtension`](index.md) | Inject a bounded `ResourceResolver` |
-| `alto/commonmark-include` | [`IncludeExtension`](index.md) | Inject a resolver and explicit recursion policy |
-| `alto/commonmark-link-rewriter` | [`LinkRewriterExtension`](index.md) | Build rules with `LinkRewriter` |
-| `alto/commonmark-source` | [`SourceExtension`](index.md) | Inject a bounded resolver |
-| `alto/commonmark-table-of-contents` | [`TableOfContentsExtension`](index.md) | Use the typed TOC policy |
-| `alto/commonmark-tabs` | [`TabsExtension`](index.md) | Review generated HTML and progressive behavior |
+| `alto/commonmark-code-block-title` | [`CodeBlockTitleExtension`](../rendering/code-block-titles.md) | Use the typed title policy |
+| `alto/commonmark-content-slicer` | [`ContentSlicerExtension`](../rendering/content-slicer.md) | `minLevel` is the first heading level that opens a section |
+| `alto/commonmark-heading-level` | [`HeadingLevelExtension`](../rendering/heading-levels.md) | Use `HeadingLevelPolicy::map()`, `shift()`, or `using()` |
+| `alto/commonmark-import` | [`ImportExtension`](../resources/import.md) | Inject a bounded `ResourceResolver` |
+| `alto/commonmark-include` | [`IncludeExtension`](../resources/include.md) | Inject a resolver and explicit recursion policy |
+| `alto/commonmark-link-rewriter` | [`LinkRewriterExtension`](../rendering/link-rewriting.md) | Build rules with `LinkRewriter` |
+| `alto/commonmark-source` | [`SourceExtension`](../resources/source.md) | Inject a bounded resolver |
+| `alto/commonmark-table-of-contents` | [`TableOfContentsExtension`](../rendering/table-of-contents.md) | Use the typed TOC policy |
+| `alto/commonmark-tabs` | [`TabsExtension`](../syntax/tabs.md) | Review generated HTML and progressive behavior |
 
 These are feature migrations, not drop-in class aliases. Re-run output,
 security, and source-preservation tests when moving an application.
diff --git a/docs/extensions/index.md b/docs/extensions/index.md
deleted file mode 100644
index e75d7c7..0000000
--- a/docs/extensions/index.md
+++ /dev/null
@@ -1,53 +0,0 @@
-# Extensions
-
-Extensions add trusted syntax, rendering, transformations, analysis, or
-resource-backed behavior to an immutable factory profile. Install only the
-capabilities required by the document format.
-
-```php
-use Alto\Markdown\Extension\Footnote\FootnoteExtension;
-use Alto\Markdown\Extension\Highlight\HighlightExtension;
-use Alto\Markdown\Markdown;
-
-$factory = Markdown::github()->with(
-    new FootnoteExtension(),
-    new HighlightExtension(),
-);
-```
-
-## Authoring syntax
-
-- [Paired delimiters](paired-delimiters.md): configurable leaf delimiter pairs.
-- [Smart punctuation](smart-punctuation.md): quotes, dashes, and ellipses.
-- [Highlight](highlight.md): highlighted inline text.
-- [Description lists](description-lists.md): terms and definitions.
-- [Footnotes](footnotes.md): definitions and references.
-- [Tabs](tabs.md): nested tab groups.
-- [Mentions](mentions.md): application-resolved references.
-- [Attributes](attributes.md): constrained source attributes.
-
-## Documents and HTML
-
-- [Heading levels](heading-levels.md): project heading levels at render time.
-- [Content slicer](content-slicer.md): group heading sections.
-- [Heading permalinks](heading-permalinks.md): add stable heading links.
-- [Table of contents](table-of-contents.md): generate a document outline.
-- [Default attributes](default-attributes.md): add controlled HTML attributes.
-- [Code block titles](code-block-titles.md): render code-block titles.
-- [External links](external-links.md): mark external links.
-- [Link rewriting](link-rewriting.md): rewrite link destinations.
-
-## External resources
-
-- [Import](import.md): insert escaped source code.
-- [Include](include.md): expand bounded Markdown resources.
-- [Source](source.md): display source excerpts.
-- [Embeds](embeds.md): resolve allowlisted rich content.
-
-Resource-backed extensions require an injected `ResourceResolver`; installing
-an extension never grants filesystem or network authority by itself. Read
-[Security](../engine/security.md) before enabling them on untrusted input.
-
-Use [Extension points](extension-points.md) to choose a public contract,
-[Custom extension](custom.md) for a minimal implementation, and
-[Compatibility](compatibility.md) before publishing an extension package.
diff --git a/docs/getting-started.md b/docs/getting-started.md
index c0a135d..69b3fda 100644
--- a/docs/getting-started.md
+++ b/docs/getting-started.md
@@ -5,7 +5,8 @@ without parsing the source twice.
 
 ## Create a document
 
-Start from a Composer application with `alto/markdown` installed:
+Start from a Composer application with `alto/markdown` installed. Save this
+as `render.php` beside `vendor/` and run `php render.php`:
 
 ```php
 <?php
@@ -27,8 +28,14 @@ echo $document->links()->count()."\n";
 echo $document->toHtml();
 ```
 
-The first two lines are `Project` and `1`. The remaining output is the rendered
-heading and paragraph.
+The complete output is:
+
+```text
+Project
+1
+<h1>Project</h1>
+<p>Read the <a href="https://example.com/guide">guide</a>.</p>
+```
 
 `github()` enables CommonMark, GitHub Flavored Markdown, GitHub alerts, and
 front matter. The returned document retains the parsed structure and original
diff --git a/docs/index.md b/docs/index.md
index 471eef6..fc03fac 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -1,6 +1,6 @@
-# Alto Markdown
+# ALTO Markdown
 
-Alto Markdown converts Markdown to safe HTML and keeps a source-backed
+ALTO Markdown converts Markdown to safe HTML and keeps a source-backed
 document model when an application needs to inspect, lint, or edit content.
 Use direct conversion for one result; open a document when later work depends
 on its structure.
@@ -11,80 +11,25 @@ use Alto\Markdown\Markdown;
 $html = Markdown::github()->toHtml("# Hello\n\nWelcome.\n");
 ```
 
-## Start
+The conversion returns `<h1>Hello</h1>` followed by a paragraph containing
+`Welcome.`. Raw HTML is escaped and unsafe URL schemes are rejected by default.
+
+## Documentation
 
 - [Installation](installation.md): install the package and verify the runtime.
 - [Getting started](getting-started.md): render and inspect one document.
-
-## Conversion
-
-- [HTML](conversion/html.md): render block or inline Markdown safely.
-- [Markdown](conversion/markdown.md): preserve source or normalize output.
-
-## Documents
-
-- [Profiles](documents/profiles.md): choose CommonMark, GFM, or GitHub syntax.
-- [Queries](documents/queries.md): find headings, sections, links, and code.
-- [Statistics](documents/statistics.md): compute one immutable document summary.
-- [Editing](documents/editing.md): make source-preserving changes and save files.
-
-## Quality
-
-- [Linting](quality/linting.md): report content and policy problems.
-- [Fixing](quality/fixing.md): apply enabled safe corrections.
-- [Formatting](quality/formatting.md): normalize selected Markdown style.
-
-## Extension API
-
-- [All extensions](extensions/index.md): choose bundled capabilities.
-- [Compatibility](extensions/compatibility.md): understand extension versioning.
-- [Extension points](extensions/extension-points.md): select the correct contract.
-- [Custom extension](extensions/custom.md): register trusted application behavior.
-
-## Syntax
-
-- [Paired delimiters](extensions/paired-delimiters.md): define a safe inline syntax.
-- [Smart punctuation](extensions/smart-punctuation.md): replace quotes, dashes, and ellipses.
-- [Highlight](extensions/highlight.md): mark inline text with paired delimiters.
-- [Description lists](extensions/description-lists.md): render terms and definitions.
-- [Footnotes](extensions/footnotes.md): connect references to endnotes.
-- [Tabs](extensions/tabs.md): group nested content into accessible panels.
-- [Mentions](extensions/mentions.md): resolve application-specific references.
-- [Attributes](extensions/attributes.md): attach constrained attributes to elements.
-
-## Rendering
-
-- [Heading levels](extensions/heading-levels.md): project headings to different HTML levels.
-- [Content slicer](extensions/content-slicer.md): wrap heading sections in semantic elements.
-- [Permalinks](extensions/heading-permalinks.md): add stable links to headings.
-- [Contents](extensions/table-of-contents.md): build a document outline.
-- [Default attributes](extensions/default-attributes.md): add controlled HTML attributes.
-- [Code titles](extensions/code-block-titles.md): label fenced code blocks.
-- [External links](extensions/external-links.md): classify and mark outbound links.
-- [Link rewriting](extensions/link-rewriting.md): transform destinations at render time.
-
-## Resources
-
-- [Import](extensions/import.md): insert escaped source code.
-- [Include](extensions/include.md): expand bounded Markdown resources.
-- [Source](extensions/source.md): display annotated source excerpts.
-- [Embeds](extensions/embeds.md): resolve allowlisted rich content.
-
-## Engine
-
-- [Security](engine/security.md): keep untrusted input within safe policies.
-- [Performance](engine/performance.md): measure the correct processing lane.
-- [Compliance](engine/compliance.md): review supported Markdown specifications.
-
-## API
-
-- [Overview](api/index.md): map the public surface by task.
-- [Documents](api/documents.md): factories, documents, and files.
-- [Nodes](api/nodes.md): inspect and mutate typed handles.
-- [Queries](api/queries.md): collections, selectors, and statistics.
-- [Editing](api/editing.md): builders, patches, diffs, and saves.
-- [Extensions](api/extensions.md): profile and extension contracts.
-- [Exceptions](api/exceptions.md): catch recoverable failures at boundaries.
-
-HTML escapes authored raw HTML and rejects unsafe URL schemes by default.
-Read [Security](engine/security.md) before changing those policies.
+- [Conversion](conversion.md): produce HTML or Markdown output.
+- [Documents](documents.md): inspect, query, measure, and edit parsed documents.
+- [Quality](quality.md): lint, fix, and format Markdown.
+- [Extensions](extensions.md): choose or create trusted capabilities.
+- [Syntax](syntax.md): add authoring syntax.
+- [Rendering](rendering.md): control document and HTML output.
+- [Resources](resources.md): resolve imported, included, and embedded content.
+- [Security](security.md): define input, HTML, and resource boundaries.
+- [Errors](errors.md): catch recoverable failures.
+- [Performance](performance.md): select and measure the correct processing path.
+- [Compliance](compliance.md): review supported Markdown specifications.
+
+The core has no runtime Composer dependencies. It supports CommonMark, GitHub
+Flavored Markdown, and GitHub-oriented documents. Extensions run as trusted
+application code and receive resource access only through an injected resolver.
diff --git a/docs/installation.md b/docs/installation.md
index 47ce1c1..bedbca0 100644
--- a/docs/installation.md
+++ b/docs/installation.md
@@ -1,6 +1,6 @@
 # Installation
 
-Install Alto Markdown in a PHP 8.4 or newer application, then run one smoke
+Install ALTO Markdown in a PHP 8.4 or newer application, then run one smoke
 test to confirm that Composer can load the package.
 
 ## Requirements
diff --git a/docs/engine/performance.md b/docs/performance.md
similarity index 100%
rename from docs/engine/performance.md
rename to docs/performance.md
diff --git a/docs/quality.md b/docs/quality.md
new file mode 100644
index 0000000..7fb1f61
--- /dev/null
+++ b/docs/quality.md
@@ -0,0 +1,18 @@
+# Quality
+
+Quality tools report content problems, apply explicit safe fixes, and normalize
+selected style without silently rewriting unrelated Markdown.
+
+```php
+$report = $document->lint($config);
+$document->fix($config);
+$document->format();
+```
+
+## Tools
+
+- [Linting](quality/linting.md): report content and policy problems.
+- [Fixing](quality/fixing.md): apply fixes attached to enabled rules.
+- [Formatting](quality/formatting.md): normalize selected Markdown style.
+
+Preview pending changes with `diff()` before saving a file.
diff --git a/docs/rendering.md b/docs/rendering.md
new file mode 100644
index 0000000..18139a8
--- /dev/null
+++ b/docs/rendering.md
@@ -0,0 +1,19 @@
+# Rendering
+
+Rendering extensions project or decorate a parsed document without changing its
+stored Markdown. Use them to control generated structure, links, headings, and
+attributes.
+
+## Extensions
+
+- [Heading levels](rendering/heading-levels.md): project headings to different HTML levels.
+- [Content slicer](rendering/content-slicer.md): wrap heading sections in semantic elements.
+- [Permalinks](rendering/heading-permalinks.md): add stable links to headings.
+- [Contents](rendering/table-of-contents.md): build a document outline.
+- [Default attributes](rendering/default-attributes.md): add controlled HTML attributes.
+- [Code titles](rendering/code-block-titles.md): label fenced code blocks.
+- [External links](rendering/external-links.md): classify and mark outbound links.
+- [Link rewriting](rendering/link-rewriting.md): transform destinations at render time.
+
+These projections affect rendered output. `toMarkdown()` continues to preserve
+the source unless a separate edit or formatting operation changes it.
diff --git a/docs/extensions/code-block-titles.md b/docs/rendering/code-block-titles.md
similarity index 100%
rename from docs/extensions/code-block-titles.md
rename to docs/rendering/code-block-titles.md
diff --git a/docs/extensions/content-slicer.md b/docs/rendering/content-slicer.md
similarity index 100%
rename from docs/extensions/content-slicer.md
rename to docs/rendering/content-slicer.md
diff --git a/docs/extensions/default-attributes.md b/docs/rendering/default-attributes.md
similarity index 100%
rename from docs/extensions/default-attributes.md
rename to docs/rendering/default-attributes.md
diff --git a/docs/extensions/external-links.md b/docs/rendering/external-links.md
similarity index 100%
rename from docs/extensions/external-links.md
rename to docs/rendering/external-links.md
diff --git a/docs/extensions/heading-levels.md b/docs/rendering/heading-levels.md
similarity index 100%
rename from docs/extensions/heading-levels.md
rename to docs/rendering/heading-levels.md
diff --git a/docs/extensions/heading-permalinks.md b/docs/rendering/heading-permalinks.md
similarity index 100%
rename from docs/extensions/heading-permalinks.md
rename to docs/rendering/heading-permalinks.md
diff --git a/docs/extensions/link-rewriting.md b/docs/rendering/link-rewriting.md
similarity index 100%
rename from docs/extensions/link-rewriting.md
rename to docs/rendering/link-rewriting.md
diff --git a/docs/extensions/table-of-contents.md b/docs/rendering/table-of-contents.md
similarity index 100%
rename from docs/extensions/table-of-contents.md
rename to docs/rendering/table-of-contents.md
diff --git a/docs/resources.md b/docs/resources.md
new file mode 100644
index 0000000..a8c47aa
--- /dev/null
+++ b/docs/resources.md
@@ -0,0 +1,16 @@
+# Resources
+
+Resource extensions resolve external content through an application-provided
+`ResourceResolver`. Installing an extension never grants filesystem or network
+authority by itself.
+
+## Extensions
+
+- [Import](resources/import.md): insert escaped source code.
+- [Include](resources/include.md): expand bounded Markdown resources.
+- [Source](resources/source.md): display annotated source excerpts.
+- [Embeds](resources/embeds.md): resolve allowlisted rich content.
+
+Set origin, size, recursion, and content-type limits in the resolver. Read
+[Security](security.md) before enabling resource-backed behavior on untrusted
+input, and [Errors](errors.md) for resolution failures.
diff --git a/docs/extensions/embeds.md b/docs/resources/embeds.md
similarity index 100%
rename from docs/extensions/embeds.md
rename to docs/resources/embeds.md
diff --git a/docs/extensions/import.md b/docs/resources/import.md
similarity index 82%
rename from docs/extensions/import.md
rename to docs/resources/import.md
index 82b8cb9..ce00122 100644
--- a/docs/extensions/import.md
+++ b/docs/resources/import.md
@@ -70,3 +70,11 @@ Resolution happens once while parsing; later renders perform no I/O.
 The resolver defines the available resources. `FilesystemResourceResolver`
 accepts relative paths only, rejects parent traversal and symlink components,
 and enforces both the extension allowlist and `maxBytes`.
+
+## When a resource is rejected
+
+Check that the requested path is relative to the configured resolver root,
+uses an allowed extension, and fits the byte limit. Verify the file exists and
+is readable. Keep the root bounded when correcting a rejected path; do not
+broaden filesystem authority to accept untrusted references. See
+[Security](../security.md) and [Errors](../errors.md).
diff --git a/docs/extensions/include.md b/docs/resources/include.md
similarity index 86%
rename from docs/extensions/include.md
rename to docs/resources/include.md
index 7951b69..7cebc9a 100644
--- a/docs/extensions/include.md
+++ b/docs/resources/include.md
@@ -89,3 +89,11 @@ raw HTML, or custom containers remain literal.
 
 The original `@include` directive is preserved when the document is rendered
 back to Markdown. Included HTML follows the active HTML policy.
+
+## When a resource is rejected
+
+Check that the requested path is relative to the configured resolver root,
+uses an allowed extension, and fits the byte limit. Verify the file exists and
+is readable. Keep the root bounded when correcting a rejected path; do not
+broaden filesystem authority to accept untrusted references. See
+[Security](../security.md) and [Errors](../errors.md).
diff --git a/docs/extensions/source.md b/docs/resources/source.md
similarity index 86%
rename from docs/extensions/source.md
rename to docs/resources/source.md
index 6c3d49b..a3f9b18 100644
--- a/docs/extensions/source.md
+++ b/docs/resources/source.md
@@ -78,3 +78,11 @@ literal and perform no I/O.
 The resolver defines the available resources. `FilesystemResourceResolver`
 accepts relative paths only, rejects parent traversal and symlink components,
 and enforces both the extension allowlist and `maxBytes`.
+
+## When a resource is rejected
+
+Check that the requested path is relative to the configured resolver root,
+uses an allowed extension, and fits the byte limit. Verify the file exists and
+is readable. Keep the root bounded when correcting a rejected path; do not
+broaden filesystem authority to accept untrusted references. See
+[Security](../security.md) and [Errors](../errors.md).
diff --git a/docs/engine/security.md b/docs/security.md
similarity index 98%
rename from docs/engine/security.md
rename to docs/security.md
index 03e8088..63075d0 100644
--- a/docs/engine/security.md
+++ b/docs/security.md
@@ -230,5 +230,5 @@ On POSIX, atomic replacement preserves permission and special mode bits or
 fails before replacement. It does not preserve ACLs, ownership, extended
 attributes, or other platform metadata. New files use `0666 & ~umask`.
 Windows replacement and mode semantics are platform-limited and may fail when
-the destination exists or is open. See [Exceptions](../api/exceptions.md) for recovery and
-[Editing](../documents/editing.md) for the complete save flow.
+the destination exists or is open. See [Errors](errors.md) for recovery and
+[Editing](documents/editing.md) for the complete save flow.
diff --git a/docs/syntax.md b/docs/syntax.md
new file mode 100644
index 0000000..f1c1599
--- /dev/null
+++ b/docs/syntax.md
@@ -0,0 +1,18 @@
+# Syntax
+
+Syntax extensions add author-facing Markdown constructs to a trusted factory
+profile. Enable only the constructs accepted by the document format.
+
+## Extensions
+
+- [Paired delimiters](syntax/paired-delimiters.md): define safe inline delimiter pairs.
+- [Smart punctuation](syntax/smart-punctuation.md): replace quotes, dashes, and ellipses.
+- [Highlight](syntax/highlight.md): mark inline text with paired delimiters.
+- [Description lists](syntax/description-lists.md): render terms and definitions.
+- [Footnotes](syntax/footnotes.md): connect references to endnotes.
+- [Tabs](syntax/tabs.md): group nested content into accessible panels.
+- [Mentions](syntax/mentions.md): resolve application-specific references.
+- [Attributes](syntax/attributes.md): attach constrained attributes to elements.
+
+Each guide shows installation, configuration, Markdown input, HTML output,
+options, and its security boundary.
diff --git a/docs/extensions/attributes.md b/docs/syntax/attributes.md
similarity index 100%
rename from docs/extensions/attributes.md
rename to docs/syntax/attributes.md
diff --git a/docs/extensions/description-lists.md b/docs/syntax/description-lists.md
similarity index 100%
rename from docs/extensions/description-lists.md
rename to docs/syntax/description-lists.md
diff --git a/docs/extensions/footnotes.md b/docs/syntax/footnotes.md
similarity index 100%
rename from docs/extensions/footnotes.md
rename to docs/syntax/footnotes.md
diff --git a/docs/extensions/highlight.md b/docs/syntax/highlight.md
similarity index 100%
rename from docs/extensions/highlight.md
rename to docs/syntax/highlight.md
diff --git a/docs/extensions/mentions.md b/docs/syntax/mentions.md
similarity index 100%
rename from docs/extensions/mentions.md
rename to docs/syntax/mentions.md
diff --git a/docs/extensions/paired-delimiters.md b/docs/syntax/paired-delimiters.md
similarity index 100%
rename from docs/extensions/paired-delimiters.md
rename to docs/syntax/paired-delimiters.md
diff --git a/docs/extensions/smart-punctuation.md b/docs/syntax/smart-punctuation.md
similarity index 100%
rename from docs/extensions/smart-punctuation.md
rename to docs/syntax/smart-punctuation.md
diff --git a/docs/extensions/tabs.md b/docs/syntax/tabs.md
similarity index 100%
rename from docs/extensions/tabs.md
rename to docs/syntax/tabs.md
diff --git a/tests/Documentation/ExtensionDocumentationTest.php b/tests/Documentation/ExtensionDocumentationTest.php
deleted file mode 100644
index c433c96..0000000
--- a/tests/Documentation/ExtensionDocumentationTest.php
+++ /dev/null
@@ -1,126 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-/*
- * This file is part of the ALTO library.
- *
- * © 2026-present Simon André
- *
- * For full copyright and license information, please see
- * the LICENSE file distributed with this source code.
- */
-
-namespace Alto\Markdown\Tests\Documentation;
-
-use PHPUnit\Framework\Attributes\DataProvider;
-use PHPUnit\Framework\TestCase;
-
-final class ExtensionDocumentationTest extends TestCase
-{
-    /**
-     * @var list<string>
-     */
-    private const array EXTENSIONS = [
-        'attributes',
-        'code-block-titles',
-        'content-slicer',
-        'default-attributes',
-        'description-lists',
-        'embeds',
-        'external-links',
-        'footnotes',
-        'heading-levels',
-        'heading-permalinks',
-        'highlight',
-        'import',
-        'include',
-        'link-rewriting',
-        'mentions',
-        'paired-delimiters',
-        'smart-punctuation',
-        'source',
-        'table-of-contents',
-        'tabs',
-    ];
-
-    #[DataProvider('provideExtensions')]
-    public function testEveryExtensionHasACompleteDocumentationPage(string $slug): void
-    {
-        $contents = $this->read('docs/extensions/' . $slug . '.md');
-
-        self::assertMatchesRegularExpression('/\A# [^\n]+\n\n\S/', $contents);
-        self::assertSame(
-            ['Install', 'Configure', 'Markdown', 'HTML', 'Options', 'Security'],
-            array_slice($this->levelTwoHeadings($contents), 0, 6),
-        );
-        self::assertStringContainsString("```bash\ncomposer require alto/markdown\n```", $contents);
-        self::assertMatchesRegularExpression('/```markdown\n.+?\n```/s', $contents);
-        self::assertMatchesRegularExpression('/```html\n.+?\n```/s', $contents);
-    }
-
-    #[DataProvider('provideExtensions')]
-    public function testEveryExtensionIsLinkedFromBothIndexes(string $slug): void
-    {
-        self::assertMatchesRegularExpression(
-            '/\]\(extensions\/' . $slug . '\.md\)/',
-            $this->read('docs/index.md'),
-        );
-        self::assertMatchesRegularExpression(
-            '/\]\(' . $slug . '\.md\)/',
-            $this->read('docs/extensions/index.md'),
-        );
-    }
-
-    /**
-     * @return iterable<string, array{string}>
-     */
-    public static function provideExtensions(): iterable
-    {
-        foreach (self::EXTENSIONS as $slug) {
-            yield $slug => [$slug];
-        }
-    }
-
-    private function read(string $path): string
-    {
-        $contents = file_get_contents(\dirname(__DIR__, 2) . '/' . $path);
-
-        self::assertIsString($contents, $path);
-
-        return $contents;
-    }
-
-    /**
-     * @return list<string>
-     */
-    private function levelTwoHeadings(string $contents): array
-    {
-        $headings = [];
-        $fenceCharacter = null;
-        $fenceLength = 0;
-
-        foreach (explode("\n", $contents) as $line) {
-            if (null !== $fenceCharacter) {
-                if (1 === preg_match('/^ {0,3}' . preg_quote($fenceCharacter, '/') . '{' . $fenceLength . ',}[ \t]*$/', $line)) {
-                    $fenceCharacter = null;
-                }
-
-                continue;
-            }
-
-            if (1 === preg_match('/^ {0,3}(`{3,}|~{3,})/', $line, $matches)) {
-                $fenceCharacter = $matches[1][0];
-                $fenceLength = \strlen($matches[1]);
-
-                continue;
-            }
-
-            if (1 === preg_match('/^## ([^#].*)$/', $line, $matches)) {
-                $headings[] = $matches[1];
-            }
-        }
-
-        return $headings;
-    }
-}
diff --git a/tests/Edit/ReadmeEditSuiteTest.php b/tests/Edit/ReadmeEditSuiteTest.php
index 35a7db2..e07f6d5 100644
--- a/tests/Edit/ReadmeEditSuiteTest.php
+++ b/tests/Edit/ReadmeEditSuiteTest.php
@@ -235,8 +235,8 @@ private function fuzzCorpus(): array
             'docs/quality/linting.md',
             'docs/quality/fixing.md',
             'docs/quality/formatting.md',
-            'docs/extensions/index.md',
-            'docs/engine/security.md',
+            'docs/extensions.md',
+            'docs/security.md',
         ];
     }