From 11c6354da0b2b33de943d4aa5f612d48ce29876c Mon Sep 17 00:00:00 2001
From: Ryan Hamamura <58859899+ryanhamamura@users.noreply.github.com>
Date: Fri, 13 Feb 2026 10:55:07 -1000
Subject: [PATCH] docs: add guide covering routing, state, HTML DSL, pubsub,
 and project structure

---
 docs/getting-started.md         | 179 ++++++++++++++++++
 docs/html-dsl.md                | 164 +++++++++++++++++
 docs/project-structure.md       | 164 +++++++++++++++++
 docs/pubsub-and-sessions.md     | 251 +++++++++++++++++++++++++
 docs/routing-and-navigation.md  | 222 ++++++++++++++++++++++
 docs/state-and-interactivity.md | 313 ++++++++++++++++++++++++++++++++
 6 files changed, 1293 insertions(+)
 create mode 100644 docs/getting-started.md
 create mode 100644 docs/html-dsl.md
 create mode 100644 docs/project-structure.md
 create mode 100644 docs/pubsub-and-sessions.md
 create mode 100644 docs/routing-and-navigation.md
 create mode 100644 docs/state-and-interactivity.md

diff --git a/docs/getting-started.md b/docs/getting-started.md
new file mode 100644
index 0000000..0c20ca3
--- /dev/null
+++ b/docs/getting-started.md
@@ -0,0 +1,179 @@
+# Getting Started
+
+Via is a server-side reactive web framework for Go. The browser connects over SSE (Server-Sent Events), and all state lives on the server — signals, actions, and view rendering happen in Go. The browser is a thin display layer that Datastar keeps in sync via DOM morphing.
+
+## Core Loop
+
+Every Via app follows the same pattern:
+
+```go
+package main
+
+import (
+    "github.com/ryanhamamura/via"
+    "github.com/ryanhamamura/via/h"
+)
+
+func main() {
+    v := via.New()
+
+    v.Config(via.Options{
+        DocumentTitle: "My App",
+    })
+
+    v.Page("/", func(c *via.Context) {
+        count := 0
+        step := c.Signal(1)
+
+        increment := c.Action(func() {
+            count += step.Int()
+            c.Sync()
+        })
+
+        c.View(func() h.H {
+            return h.Div(
+                h.P(h.Textf("Count: %d", count)),
+                h.Label(
+                    h.Text("Step: "),
+                    h.Input(h.Type("number"), step.Bind()),
+                ),
+                h.Button(h.Text("+"), increment.OnClick()),
+            )
+        })
+    })
+
+    v.Start()
+}
+```
+
+What happens:
+
+1. `via.New()` creates the app, starts an embedded NATS server, and registers internal routes (`/_sse`, `/_action/{id}`, `/_navigate`, `/_session/close`).
+2. `v.Config()` applies settings.
+3. `v.Page()` registers a route. The init function receives a `*Context` where you define signals, actions, and the view.
+4. `v.Start()` starts the HTTP server and blocks until SIGINT/SIGTERM.
+
+When a browser hits the page, Via creates a new `Context`, runs the init function, renders the full HTML document, and opens an SSE connection. From that point, every `c.Sync()` re-renders the view and pushes a DOM patch to the browser.
+
+## Configuration
+
+```go
+v.Config(via.Options{
+    DevMode:         true,
+    ServerAddress:   ":8080",
+    LogLevel:        via.LogLevelDebug,
+    DocumentTitle:   "My App",
+    Plugins:         []via.Plugin{MyPlugin},
+    SessionManager:  sm,
+    PubSub:          customBackend,
+    ContextTTL:      60 * time.Second,
+    ActionRateLimit: via.RateLimitConfig{Rate: 20, Burst: 40},
+})
+```
+
+| Field | Default | Description |
+|-------|---------|-------------|
+| `DevMode` | `false` | Enables context persistence across restarts, console logger, and Datastar inspector widget |
+| `ServerAddress` | `":3000"` | HTTP listen address |
+| `LogLevel` | `InfoLevel` | Minimum log level. Use `via.LogLevelDebug`, `LogLevelInfo`, `LogLevelWarn`, `LogLevelError` |
+| `Logger` | (auto) | Replace the default logger entirely. When set, `LogLevel` and `DevMode` have no effect on logging |
+| `DocumentTitle` | `"⚡ Via"` | The `<title>` of the HTML document |
+| `Plugins` | `nil` | Slice of plugin functions executed during `Config()` |
+| `SessionManager` | in-memory | Cookie-based session manager. See [PubSub and Sessions](pubsub-and-sessions.md) |
+| `DatastarContent` | (embedded) | Custom Datastar JS bytes |
+| `DatastarPath` | `"/_datastar.js"` | URL path for the Datastar script |
+| `PubSub` | embedded NATS | Custom PubSub backend. Replaces the default NATS. See [PubSub and Sessions](pubsub-and-sessions.md) |
+| `ContextTTL` | `30s` | Max time a context survives without an SSE connection before cleanup. Negative value disables the reaper |
+| `ActionRateLimit` | `10 req/s, burst 20` | Default token-bucket rate limiter for action endpoints. Rate of `-1` disables limiting |
+
+## Static Files
+
+Serve files from a directory:
+
+```go
+v.Static("/assets/", "./static")
+```
+
+Or from an embedded filesystem:
+
+```go
+//go:embed static
+var staticFS embed.FS
+
+v.StaticFS("/assets/", staticFS)
+```
+
+Both disable directory listing and return 404 for directory paths.
+
+## Head and Foot Injection
+
+Add elements to every page's `<head>` or end of `<body>`:
+
+```go
+v.AppendToHead(
+    h.Link(h.Rel("stylesheet"), h.Href("/assets/style.css")),
+    h.Meta(h.Attr("name", "viewport"), h.Attr("content", "width=device-width, initial-scale=1")),
+)
+
+v.AppendToFoot(
+    h.Script(h.Src("/assets/app.js")),
+)
+```
+
+These are additive and affect all pages globally.
+
+## Plugins
+
+A plugin is a `func(v *via.V)` that mutates the app during configuration — registering routes, injecting assets, or applying middleware.
+
+```go
+func PicoCSSPlugin(v *via.V) {
+    v.HTTPServeMux().HandleFunc("GET /css/pico.css", func(w http.ResponseWriter, r *http.Request) {
+        w.Header().Set("Content-Type", "text/css")
+        w.Write(picoCSSBytes)
+    })
+    v.AppendToHead(h.Link(h.Rel("stylesheet"), h.Href("/css/pico.css")))
+}
+
+// Usage:
+v.Config(via.Options{
+    Plugins: []via.Plugin{PicoCSSPlugin},
+})
+```
+
+Plugins have full access to the `*V` public API: `HTTPServeMux()`, `AppendToHead()`, `AppendToFoot()`, `Config()`, etc.
+
+## DevMode
+
+Enable during development for a better feedback loop:
+
+```go
+v.Config(via.Options{DevMode: true})
+```
+
+What it does:
+
+- **Console logger** — Human-readable log output with timestamps.
+- **Context persistence** — Saves context-to-route mappings to `.via/devmode/ctx.json`. On server restart, reconnecting browsers restore their state instead of getting a blank page. Pair with [Air](https://github.com/air-verse/air) for hot-reloading.
+- **Datastar inspector** — Injects a widget showing live signal values and SSE activity.
+
+## Custom HTTP Handlers
+
+Access the underlying `*http.ServeMux` for custom routes:
+
+```go
+mux := v.HTTPServeMux()
+mux.HandleFunc("GET /api/health", func(w http.ResponseWriter, r *http.Request) {
+    w.Write([]byte("ok"))
+})
+```
+
+Register custom handlers before calling `v.Start()`.
+
+## Next Steps
+
+- [State and Interactivity](state-and-interactivity.md) — Signals, actions, components, validation
+- [Routing and Navigation](routing-and-navigation.md) — Multi-page apps, middleware, SPA navigation
+- [PubSub and Sessions](pubsub-and-sessions.md) — Real-time messaging, persistent sessions
+- [HTML DSL](html-dsl.md) — The `h` package reference
+- [Project Structure](project-structure.md) — Organizing files as your app grows
diff --git a/docs/html-dsl.md b/docs/html-dsl.md
new file mode 100644
index 0000000..aec3155
--- /dev/null
+++ b/docs/html-dsl.md
@@ -0,0 +1,164 @@
+# HTML DSL
+
+Reference for the `h` package — Via's HTML builder.
+
+## Overview
+
+The `h` package wraps [gomponents](https://github.com/maragudk/gomponents) with a single interface:
+
+```go
+type H interface {
+    Render(w io.Writer) error
+}
+```
+
+Every element, attribute, and text node implements `H`. Build HTML by nesting function calls:
+
+```go
+import "github.com/ryanhamamura/via/h"
+
+h.Div(h.Class("card"),
+    h.H2(h.Text("Title")),
+    h.P(h.Textf("Count: %d", count)),
+    h.Button(h.Text("Click"), action.OnClick()),
+)
+```
+
+For cleaner templates, use a dot import:
+
+```go
+import . "github.com/ryanhamamura/via/h"
+
+Div(Class("card"),
+    H2(Text("Title")),
+    P(Textf("Count: %d", count)),
+    Button(Text("Click"), action.OnClick()),
+)
+```
+
+## Text Nodes
+
+| Function | Description |
+|----------|-------------|
+| `Text(s)` | Escaped text node |
+| `Textf(fmt, args...)` | Escaped text with `fmt.Sprintf` |
+| `Raw(s)` | Unescaped raw HTML — use for trusted content like SVG |
+| `Rawf(fmt, args...)` | Unescaped raw HTML with `fmt.Sprintf` |
+
+## Elements
+
+Every element function takes `...H` children (elements, attributes, and text nodes mixed together) except `Style(v string)` and `Title(v string)` which take a single string.
+
+### Document structure
+
+`HTML`, `Head`, `Body`, `Main`, `Header`, `Footer`, `Section`, `Article`, `Aside`, `Nav`, `Div`, `Span`
+
+### Headings
+
+`H1`, `H2`, `H3`, `H4`, `H5`, `H6`
+
+### Text
+
+`P`, `A`, `Strong`, `Em`, `B`, `I`, `U`, `S`, `Small`, `Mark`, `Del`, `Ins`, `Sub`, `Sup`, `Abbr`, `Cite`, `Code`, `Pre`, `Samp`, `Kbd`, `Var`, `Q`, `BlockQuote`, `Dfn`, `Wbr`, `Br`, `Hr`
+
+### Forms
+
+`Form`, `Input`, `Textarea`, `Select`, `Option`, `OptGroup`, `Button`, `Label`, `FieldSet`, `Legend`, `DataList`, `Meter`, `Progress`
+
+### Tables
+
+`Table`, `THead`, `TBody`, `TFoot`, `Tr`, `Th`, `Td`, `Caption`, `Col`, `ColGroup`
+
+### Lists
+
+`Ul`, `Ol`, `Li`, `Dl`, `Dt`, `Dd`
+
+### Media
+
+`Img`, `Audio`, `Video`, `Source`, `Picture`, `Canvas`, `IFrame`, `Embed`, `Object`
+
+### Other
+
+`Details`, `Summary`, `Dialog`, `Template`, `NoScript`, `Figure`, `FigCaption`, `Address`, `Time`, `Base`, `Link`, `Meta`, `Script`, `Area`
+
+### Special signatures
+
+| Function | Signature | Notes |
+|----------|-----------|-------|
+| `Style(v)` | `func Style(v string) H` | Inline `style` attribute, not a container element |
+| `StyleEl(children...)` | `func StyleEl(children ...H) H` | The `<style>` element as a container |
+| `Title(v)` | `func Title(v string) H` | Sets `<title>` text |
+
+## Attributes
+
+### Generic
+
+```go
+Attr("name", "value")     // name="value"
+Attr("disabled")           // boolean attribute (no value)
+```
+
+`Attr` with no value produces a boolean attribute. With one value, it produces a name-value pair. More than one value panics.
+
+### Named helpers
+
+| Function | HTML output |
+|----------|-------------|
+| `ID(v)` | `id="v"` |
+| `Class(v)` | `class="v"` |
+| `Href(v)` | `href="v"` |
+| `Src(v)` | `src="v"` |
+| `Type(v)` | `type="v"` |
+| `Value(v)` | `value="v"` |
+| `Placeholder(v)` | `placeholder="v"` |
+| `Rel(v)` | `rel="v"` |
+| `Role(v)` | `role="v"` |
+| `Data(name, v)` | `data-name="v"` (auto-prefixes `data-`) |
+
+## Conditional Rendering
+
+```go
+h.If(showError, h.P(h.Class("error"), h.Text("Something went wrong")))
+```
+
+Returns the node when `true`, `nil` (renders nothing) when `false`.
+
+## Datastar Helpers
+
+These produce attributes used by Datastar for client-side reactivity.
+
+| Function | Output | Description |
+|----------|--------|-------------|
+| `DataInit(expr)` | `data-init="expr"` | Initialize client-side state |
+| `DataEffect(expr)` | `data-effect="expr"` | Reactive side effect expression |
+| `DataIgnoreMorph()` | `data-ignore-morph` | Skip this element during DOM morph. See [SPA Navigation](routing-and-navigation.md#dataignoremorph) |
+| `DataViewTransition(name)` | `style="view-transition-name: name"` | Animate element across SPA navigations. See [View Transitions](routing-and-navigation.md#view-transitions) |
+
+> `DataViewTransition` sets the entire `style` attribute. If you also need other inline styles, include `view-transition-name` directly in a `Style()` call.
+
+## Utilities
+
+### HTML5
+
+Full HTML5 document template:
+
+```go
+h.HTML5(h.HTML5Props{
+    Title:       "My Page",
+    Description: "Page description",
+    Language:    "en",
+    Head:        []h.H{h.Link(h.Rel("stylesheet"), h.Href("/style.css"))},
+    Body:        []h.H{h.Div(h.Text("Hello"))},
+})
+```
+
+Via uses this internally to render the initial page document. You typically don't need it directly.
+
+### JoinAttrs
+
+Joins attribute values from child nodes by spaces:
+
+```go
+h.JoinAttrs("class", h.Class("card"), h.Class("active"))
+// → class="card active"
+```
diff --git a/docs/project-structure.md b/docs/project-structure.md
new file mode 100644
index 0000000..97caf5b
--- /dev/null
+++ b/docs/project-structure.md
@@ -0,0 +1,164 @@
+# Project Structure
+
+Via's closure-based page model pulls signals, actions, and views into a single scope — similar to Svelte's single-file components. This works well at every scale, but the way you organize files should evolve as your app grows.
+
+## Stage 1: Everything in main.go
+
+For small apps and prototypes, keep everything in `main.go`. This is the right choice when your app is under ~150 lines or has a single page.
+
+Within the file, follow this ordering convention inside each page:
+
+```go
+v.Page("/", func(c *via.Context) {
+    // State — plain Go variables and signals
+    count := 0
+    step := c.Signal(1)
+
+    // Actions — event handlers that mutate state
+    increment := c.Action(func() {
+        count += step.Int()
+        c.Sync()
+    })
+
+    // View — returns the HTML tree
+    c.View(func() h.H {
+        return h.Div(
+            h.P(h.Textf("Count: %d", count)),
+            h.Button(h.Text("+"), increment.OnClick()),
+        )
+    })
+})
+```
+
+State → signals → actions → view. This reads top-to-bottom and matches the data flow: state is declared, actions mutate it, the view renders it.
+
+The [counter](../internal/examples/counter/main.go) and [greeter](../internal/examples/greeter/main.go) examples use this layout.
+
+## Stage 2: Page per file
+
+When `main.go` has multiple pages or exceeds ~150 lines, extract each page into its own file as a package-level function.
+
+`main.go` becomes the app skeleton — setup, configuration, routes, and start:
+
+```go
+package main
+
+import (
+    "github.com/ryanhamamura/via"
+    "github.com/ryanhamamura/via/h"
+)
+
+func main() {
+    v := via.New()
+    v.Config(via.Options{
+        DocumentTitle: "My App",
+    })
+
+    v.AppendToHead(
+        h.Link(h.Rel("stylesheet"), h.Href("/css/pico.css")),
+    )
+
+    v.Page("/", HomePage)
+    v.Page("/chat", ChatPage)
+
+    v.Start()
+}
+```
+
+Each page lives in its own file with a descriptive name:
+
+```go
+// home.go
+package main
+
+import (
+    "github.com/ryanhamamura/via"
+    "github.com/ryanhamamura/via/h"
+)
+
+func HomePage(c *via.Context) {
+    greeting := c.Signal("Hello")
+
+    c.View(func() h.H {
+        return h.Div(h.P(h.Text(greeting.String())))
+    })
+}
+```
+
+Components follow the same pattern — keep them in the page file if single-use, or extract to their own file if reused across pages. Middleware goes in the same file as the route group it protects, or in `middleware.go` if shared.
+
+```
+myapp/
+├── main.go         # skeleton + routes
+├── home.go         # func HomePage(c *via.Context)
+├── chat.go         # func ChatPage(c *via.Context)
+└── middleware.go    # shared middleware
+```
+
+## Stage 3: Co-located CSS and shared types
+
+As pages accumulate custom styling, CSS strings in Go become hard to maintain — no syntax highlighting, no linting. Extract them to `.css` files alongside the pages they belong to and use `//go:embed` to load them.
+
+```go
+// main.go
+package main
+
+import "embed"
+
+//go:embed chat.css
+var chatCSS string
+
+func main() {
+    v := via.New()
+
+    v.AppendToHead(
+        h.Link(h.Rel("stylesheet"), h.Href("https://cdn.jsdelivr.net/npm/@picocss/pico@2/css/pico.min.css")),
+        h.StyleEl(h.Raw(chatCSS)),
+    )
+
+    // ...
+}
+```
+
+When multiple pages share the same structs, extract them to `types.go`. Framework-agnostic domain logic (helpers, dummy data, business rules) gets its own file too.
+
+```
+myapp/
+├── main.go         # skeleton + routes + global styles
+├── home.go
+├── chat.go
+├── chat.css        # //go:embed in main.go
+├── types.go        # shared types
+└── userdata.go     # helpers, dummy data
+```
+
+The [nats-chatroom](../internal/examples/nats-chatroom/) example demonstrates this layout.
+
+## CSS Approaches
+
+Via doesn't prescribe a CSS strategy. Two approaches work well:
+
+**CSS framework classes in Go code** — Use Pico, Tailwind, or similar. Classes go directly in the view via `h.Class()`. Good for rapid prototyping since there's nothing to extract.
+
+```go
+h.Div(h.Class("container"),
+    h.Button(h.Class("primary"), h.Text("Save")),
+)
+```
+
+**Co-located `.css` files with `//go:embed`** — Write plain CSS in a separate file, embed it, and inject via `AppendToHead`. You get syntax highlighting, linting, and clean separation.
+
+```go
+//go:embed chat.css
+var chatCSS string
+
+// in main():
+v.AppendToHead(h.StyleEl(h.Raw(chatCSS)))
+```
+
+Use a framework for quick prototypes and dashboards. Switch to co-located CSS files when you have significant custom styling or want tooling support.
+
+## Next Steps
+
+- [Getting Started](getting-started.md) — The core loop and configuration
+- [State and Interactivity](state-and-interactivity.md) — Signals, actions, components, validation
diff --git a/docs/pubsub-and-sessions.md b/docs/pubsub-and-sessions.md
new file mode 100644
index 0000000..1d6f4aa
--- /dev/null
+++ b/docs/pubsub-and-sessions.md
@@ -0,0 +1,251 @@
+# PubSub and Sessions
+
+Infrastructure for multi-user real-time communication and persistent state.
+
+## PubSub
+
+Via includes an embedded NATS server that starts automatically with `via.New()`. No external services required — pub/sub works out of the box.
+
+### Interface
+
+```go
+type PubSub interface {
+    Publish(subject string, data []byte) error
+    Subscribe(subject string, handler func(data []byte)) (Subscription, error)
+    Close() error
+}
+
+type Subscription interface {
+    Unsubscribe() error
+}
+```
+
+You can replace the default NATS with any backend implementing this interface via `Options.PubSub`.
+
+### Basic pub/sub
+
+```go
+// Subscribe to messages
+via.Subscribe(c, "chat.room.general", func(msg ChatMessage) {
+    messages = append(messages, msg)
+    c.Sync()
+})
+
+// Publish a message
+via.Publish(c, "chat.room.general", ChatMessage{
+    User:    username,
+    Message: text,
+    Time:    time.Now().UnixMilli(),
+})
+```
+
+The generic helpers `via.Publish[T]` and `via.Subscribe[T]` handle JSON marshaling/unmarshaling automatically. They are package-level functions (not methods) because Go doesn't support generic methods.
+
+Raw byte-level access is also available on the context:
+
+```go
+c.Publish("subject", []byte("raw data"))
+c.Subscribe("subject", func(data []byte) { /* ... */ })
+```
+
+### Auto-cleanup
+
+Subscriptions created via `c.Subscribe()` or `via.Subscribe()` are tracked on the context and automatically unsubscribed when:
+
+- The context is disposed (browser disconnects, tab closes)
+- SPA navigation moves to a different page
+
+You don't need to manually unsubscribe in normal usage.
+
+### Custom backend
+
+Replace the embedded NATS with your own PubSub implementation:
+
+```go
+v.Config(via.Options{
+    PubSub: myRedisBackend,
+})
+```
+
+This disables the embedded NATS server. The `NATSConn()` and `JetStream()` accessors will return nil.
+
+## JetStream
+
+NATS JetStream provides persistent, replayable message streams. Useful for chat history, event logs, or any scenario where new subscribers need to catch up on past messages.
+
+### Ensure a stream exists
+
+```go
+err := via.EnsureStream(v, via.StreamConfig{
+    Name:     "CHAT",
+    Subjects: []string{"chat.>"},
+    MaxMsgs:  1000,
+    MaxAge:   24 * time.Hour,
+})
+```
+
+| Field | Description |
+|-------|-------------|
+| `Name` | Stream name |
+| `Subjects` | NATS subjects to capture (supports wildcards: `>` matches all sub-levels) |
+| `MaxMsgs` | Maximum number of messages to retain |
+| `MaxAge` | Maximum age before messages are discarded |
+
+Call `EnsureStream` during app initialization, before `v.Start()`.
+
+### Replay history
+
+Retrieve recent messages from a stream:
+
+```go
+messages, err := via.ReplayHistory[ChatMessage](v, "chat.room.general", 50)
+```
+
+Returns up to the last `limit` messages on the subject, deserialized as `T`. Use this when a new user joins and needs to see recent history.
+
+### Direct NATS access
+
+For advanced use cases, access the NATS connection and JetStream context directly:
+
+```go
+nc := v.NATSConn()       // *nats.Conn, nil if custom PubSub
+js := v.JetStream()      // nats.JetStreamContext, nil if custom PubSub
+```
+
+### PubSub accessor
+
+Access the configured PubSub backend from the `V` instance:
+
+```go
+ps := v.PubSub() // via.PubSub interface, nil if none configured
+```
+
+## Sessions
+
+Via uses [SCS](https://github.com/alexedwards/scs) for cookie-based session management.
+
+### Setup with SQLite
+
+```go
+db, _ := sql.Open("sqlite3", "app.db")
+
+sm, _ := via.NewSQLiteSessionManager(db)
+sm.Lifetime = 24 * time.Hour
+sm.Cookie.SameSite = http.SameSiteLaxMode
+
+v.Config(via.Options{SessionManager: sm})
+```
+
+`NewSQLiteSessionManager` creates the `sessions` table and index if they don't exist. The returned `*scs.SessionManager` can be configured further (lifetime, cookie settings) before passing to `Config`.
+
+A default in-memory session manager is always available, even without explicit configuration. Use `NewSQLiteSessionManager` when you need sessions to survive server restarts.
+
+### Session API
+
+Access the session from any context:
+
+```go
+s := c.Session()
+```
+
+**Getters:**
+
+| Method | Return type |
+|--------|-------------|
+| `s.Get(key)` | `any` |
+| `s.GetString(key)` | `string` |
+| `s.GetInt(key)` | `int` |
+| `s.GetBool(key)` | `bool` |
+| `s.GetFloat64(key)` | `float64` |
+| `s.GetTime(key)` | `time.Time` |
+| `s.GetBytes(key)` | `[]byte` |
+
+**Pop** (get and delete — useful for flash messages):
+
+| Method | Return type |
+|--------|-------------|
+| `s.Pop(key)` | `any` |
+| `s.PopString(key)` | `string` |
+| `s.PopInt(key)` | `int` |
+| `s.PopBool(key)` | `bool` |
+| `s.PopFloat64(key)` | `float64` |
+| `s.PopTime(key)` | `time.Time` |
+| `s.PopBytes(key)` | `[]byte` |
+
+**Mutators:**
+
+| Method | Description |
+|--------|-------------|
+| `s.Set(key, val)` | Store a value |
+| `s.Delete(key)` | Remove a single key |
+| `s.Clear()` | Remove all session data |
+| `s.Destroy()` | Destroy the entire session (for logout) |
+| `s.RenewToken()` | Regenerate session ID (prevents session fixation — call after login) |
+
+**Introspection:**
+
+| Method | Description |
+|--------|-------------|
+| `s.Exists(key)` | True if key exists |
+| `s.Keys()` | All keys in the session |
+| `s.ID()` | Session token (cookie value) |
+
+All getters return zero values if the key doesn't exist or the session manager is nil.
+
+### Auth pattern
+
+A common login/logout flow using sessions and middleware:
+
+```go
+// Middleware
+func authRequired(c *via.Context, next func()) {
+    if c.Session().GetString("username") == "" {
+        c.Session().Set("flash", "Please log in first")
+        c.RedirectView("/login")
+        return
+    }
+    next()
+}
+
+// Login page
+v.Page("/login", func(c *via.Context) {
+    user := c.Signal("")
+    pass := c.Signal("")
+    flash := c.Session().PopString("flash")
+
+    login := c.Action(func() {
+        if authenticate(user.String(), pass.String()) {
+            c.Session().RenewToken()
+            c.Session().Set("username", user.String())
+            c.Redirect("/dashboard")
+        } else {
+            flash = "Invalid credentials"
+            c.Sync()
+        }
+    })
+
+    c.View(func() h.H {
+        return h.Form(login.OnSubmit(),
+            h.If(flash != "", h.P(h.Text(flash))),
+            h.Input(h.Type("text"), user.Bind(), h.Placeholder("Username")),
+            h.Input(h.Type("password"), pass.Bind(), h.Placeholder("Password")),
+            h.Button(h.Type("submit"), h.Text("Log In")),
+        )
+    })
+})
+
+// Protected pages
+protected := v.Group("", authRequired)
+protected.Page("/dashboard", dashboardHandler)
+
+// Logout action (inside a protected page)
+logout := c.Action(func() {
+    c.Session().Destroy()
+    c.Redirect("/login")
+})
+```
+
+Key points:
+- Call `RenewToken()` after login to prevent session fixation.
+- Use `PopString` for flash messages — they're read once then removed.
+- Use `RedirectView` in middleware, `Redirect` in actions. See the [gotcha in routing](routing-and-navigation.md#middleware).
diff --git a/docs/routing-and-navigation.md b/docs/routing-and-navigation.md
new file mode 100644
index 0000000..10762c9
--- /dev/null
+++ b/docs/routing-and-navigation.md
@@ -0,0 +1,222 @@
+# Routing and Navigation
+
+Multi-page app structure, middleware, and Via's SPA navigation system.
+
+## Pages
+
+Register a page with a route pattern and an init function:
+
+```go
+v.Page("/", func(c *via.Context) {
+    c.View(func() h.H {
+        return h.H1(h.Text("Home"))
+    })
+})
+```
+
+Routes use Go's standard `net/http.ServeMux` patterns. Via registers each page as a `GET` handler.
+
+> **Gotcha:** Via runs every page init function at registration time (in a `defer/recover` block) to catch panics early. If your init function panics — e.g. by forgetting `c.View()` — the app crashes at startup, not at request time.
+
+## Path Parameters
+
+Use `{param}` syntax in route patterns:
+
+```go
+v.Page("/users/{id}/posts/{post_id}", func(c *via.Context) {
+    userID := c.GetPathParam("id")
+    postID := c.GetPathParam("post_id")
+
+    c.View(func() h.H {
+        return h.P(h.Textf("User %s, Post %s", userID, postID))
+    })
+})
+```
+
+`GetPathParam` returns an empty string if the parameter doesn't exist.
+
+## Route Groups
+
+Group pages under a shared prefix with shared middleware:
+
+```go
+admin := v.Group("/admin", authRequired)
+admin.Page("/dashboard", dashboardHandler) // route: /admin/dashboard
+admin.Page("/settings", settingsHandler)   // route: /admin/settings
+```
+
+### Nesting
+
+Groups nest — the child inherits the parent's prefix and middleware:
+
+```go
+admin := v.Group("/admin", authRequired)
+admin.Use(auditLog) // add middleware after creation
+
+superAdmin := admin.Group("/super", superAdminOnly)
+superAdmin.Page("/nuke", nukeHandler) // route: /admin/super/nuke
+// middleware order: global → authRequired → auditLog → superAdminOnly → handler
+```
+
+### Empty prefix
+
+Use an empty prefix when you need shared middleware without a path prefix:
+
+```go
+protected := v.Group("", authRequired)
+protected.Page("/dashboard", dashboardHandler) // route: /dashboard
+protected.Page("/profile", profileHandler)     // route: /profile
+```
+
+## Middleware
+
+```go
+type Middleware func(c *Context, next func())
+```
+
+Call `next()` to continue the chain. Return without calling `next()` to abort — but set a view first.
+
+```go
+func authRequired(c *via.Context, next func()) {
+    if c.Session().GetString("username") == "" {
+        c.Session().Set("flash", "Please log in")
+        c.RedirectView("/login")
+        return // don't call next — chain is aborted
+    }
+    next()
+}
+```
+
+> **Gotcha:** Use `c.RedirectView()` in middleware, not `c.Redirect()`. The SSE connection isn't open yet during the initial page load, so `Redirect()` (which sends a patch over SSE) won't work. `RedirectView()` sets the view to one that triggers a redirect once SSE connects.
+
+### Three levels
+
+| Level | Registration | Scope |
+|-------|-------------|-------|
+| Global | `v.Use(mw...)` | Every page |
+| Group | `v.Group(prefix, mw...)` or `g.Use(mw...)` | Pages in the group |
+| Action | `c.Action(fn, via.WithMiddleware(mw...))` | A single action endpoint |
+
+### Execution order
+
+Middleware runs in registration order: global first, then group, then the handler.
+
+```go
+v.Use(logger)                        // 1st
+admin := v.Group("/admin", auth)     // 2nd
+admin.Use(audit)                     // 3rd
+admin.Page("/x", handler)           // 4th
+// execution: logger → auth → audit → handler
+```
+
+Action-level middleware runs after CSRF validation and rate limiting, when the action endpoint is invoked.
+
+## SPA Navigation
+
+Via intercepts same-origin link clicks and navigates without a full page reload. The SSE connection persists, and the new page's view is morphed into the DOM with a view transition.
+
+### How it works
+
+1. `navigate.js` (embedded in every page) intercepts clicks on `<a>` elements.
+2. For same-origin links, it POSTs to `/_navigate` with the context ID, CSRF token, and target URL.
+3. The server calls `c.Navigate()`, which:
+   - Resets page state (stops intervals, unsubscribes PubSub, clears signals/actions/fields)
+   - Runs the target page's init function (with middleware) on the **same context**
+   - Pushes the new view via SSE with a view transition
+   - Updates the browser URL via `history.pushState()`
+
+### What gets cleaned up on navigate
+
+- Intervals stop (via `pageStopChan`)
+- PubSub subscriptions are unsubscribed
+- Signals, actions, and fields are cleared
+- The new page starts completely fresh
+
+The SSE connection and the context itself survive. This is what makes it an SPA — the existing stream is reused.
+
+### Layouts
+
+Define a layout to provide persistent chrome (nav bars, sidebars) that wraps every page:
+
+```go
+v.Layout(func(content func() h.H) h.H {
+    return h.Div(
+        h.Nav(
+            h.A(h.Href("/"), h.Text("Home")),
+            h.A(h.Href("/counter"), h.Text("Counter")),
+            h.A(h.Href("/clock"), h.Text("Clock")),
+        ),
+        h.Main(content()),
+    )
+})
+```
+
+The `content` parameter is the page's view function. During SPA navigation, the entire layout + content is re-rendered and morphed — Datastar's morph algorithm (idiomorph) efficiently updates only the changed parts, so the nav bar stays visually stable while the main content transitions.
+
+> **Gotcha:** Layout state does not persist across navigations in the way page state doesn't — the layout is re-rendered from scratch each time. If you need state that survives navigation (like a selected nav item), derive it from the current route rather than storing it in a variable.
+
+### View transitions
+
+Animate elements across page navigations using the browser View Transitions API:
+
+```go
+// On the home page:
+h.H1(h.Text("Home"), h.DataViewTransition("page-title"))
+
+// On the counter page:
+h.H1(h.Text("Counter"), h.DataViewTransition("page-title"))
+```
+
+Elements with matching `view-transition-name` values animate smoothly during SPA navigation. `DataViewTransition` sets the CSS `view-transition-name` as an inline `style` attribute. If the element also needs other inline styles, set `view-transition-name` directly in a `Style()` call instead.
+
+Via automatically includes the `<meta name="view-transition" content="same-origin">` tag to enable the API.
+
+### Opting out
+
+Add `data-via-no-boost` to links that should trigger a full page reload:
+
+```go
+h.A(h.Href("/"), h.Text("Full Reload"), h.Attr("data-via-no-boost"))
+```
+
+Links are also auto-ignored when:
+- They have a `target` attribute (e.g. `target="_blank"`)
+- Modifier keys are held (Ctrl, Meta, Shift, Alt)
+- The `href` starts with `#` or is cross-origin
+- The `href` is missing
+
+### Programmatic navigation
+
+Trigger SPA navigation from an action handler:
+
+```go
+goCounter := c.Action(func() {
+    c.Navigate("/counter", false)
+})
+```
+
+The second parameter controls history behavior: `false` for `pushState` (normal navigation), `true` for `replaceState` (back/forward).
+
+If the path doesn't match any registered route, `Navigate` falls back to `c.Redirect()` (full page navigation).
+
+### DataIgnoreMorph
+
+Prevent Datastar from overwriting an element during morph:
+
+```go
+h.Div(h.ID("toast-container"), h.DataIgnoreMorph())
+```
+
+The element and its subtree are skipped during DOM patches. Useful for elements with client-side state: a focused input, an animation, a third-party widget, or a toast notification container.
+
+## Custom HTTP Handlers
+
+Access the underlying mux for non-Via routes (APIs, webhooks, health checks):
+
+```go
+mux := v.HTTPServeMux()
+mux.HandleFunc("GET /api/health", healthHandler)
+mux.HandleFunc("POST /api/webhook", webhookHandler)
+```
+
+Register before `v.Start()`. These routes bypass Via's context/SSE system entirely.
diff --git a/docs/state-and-interactivity.md b/docs/state-and-interactivity.md
new file mode 100644
index 0000000..3bf4a94
--- /dev/null
+++ b/docs/state-and-interactivity.md
@@ -0,0 +1,313 @@
+# State and Interactivity
+
+This is the core reactive model — signals, actions, views, components, and validation.
+
+## Context Lifecycle
+
+A `*Context` is created per browser visit. It holds all page state: signals, actions, fields, subscriptions, and the view function.
+
+```
+Browser hits page → new Context created → init function runs → HTML rendered
+                                                                    ↓
+                                        SSE connection opens ← browser loads page
+                                                ↓
+                        action fires → signals injected from browser → handler runs → Sync() → DOM patched
+```
+
+The context is disposed when the SSE connection closes (tab close, navigation away, network loss). A background reaper also cleans up contexts that never establish an SSE connection within `ContextTTL` (default 30s).
+
+During [SPA navigation](routing-and-navigation.md#spa-navigation), the context itself survives — only page-level state (signals, actions, fields, intervals, subscriptions) is reset. The SSE connection persists.
+
+## Signals
+
+Signals are reactive values synchronized between server and browser. Create one with an initial value:
+
+```go
+name := c.Signal("world")
+count := c.Signal(0)
+items := c.Signal([]string{"a", "b"})
+```
+
+### Reading values
+
+```go
+name.String()  // "world"
+count.Int()    // 0
+count.Bool()   // false (parses "true", "1", "yes", "on")
+```
+
+Signal values come from the browser. Before every action call, the browser sends all current signal values to the server. You always read the latest browser state inside action handlers.
+
+### Writing values
+
+```go
+name.SetValue("Via")
+c.SyncSignals()  // push only changed signals to browser
+// or
+c.Sync()  // re-render view AND push changed signals
+```
+
+`SetValue` marks the signal as changed. The change is not sent to the browser until you call `Sync()` or `SyncSignals()`.
+
+### Rendering in the view
+
+```go
+// Two-way binding on an input — browser edits update the signal
+h.Input(h.Type("text"), name.Bind())
+
+// Reactive text display — updates when the signal changes
+h.Span(name.Text())
+
+// Read value at render time — static until next Sync()
+h.P(h.Textf("Count: %d", count.Int()))
+```
+
+`Bind()` outputs a `data-bind` attribute for two-way binding. `Text()` outputs a `<span data-text="$signalID">` for reactive display.
+
+## Actions
+
+Actions are server-side event handlers. They run on the server when triggered by a browser event.
+
+```go
+submit := c.Action(func() {
+    // signals are already injected — read them here
+    fmt.Println(name.String())
+    count.SetValue(count.Int() + 1)
+    c.Sync()
+})
+```
+
+### Trigger methods
+
+Attach an action to a DOM event by calling a trigger method in the view:
+
+```go
+h.Button(h.Text("Submit"), submit.OnClick())
+h.Input(name.Bind(), submit.OnKeyDown("Enter"))
+h.Select(category.Bind(), filter.OnChange())
+h.Form(submit.OnSubmit())
+```
+
+Available triggers:
+
+| Method | Event | Notes |
+|--------|-------|-------|
+| `OnClick()` | `click` | |
+| `OnDblClick()` | `dblclick` | |
+| `OnChange()` | `change` | 200ms debounce |
+| `OnInput()` | `input` | No debounce |
+| `OnSubmit()` | `submit` | |
+| `OnKeyDown(key)` | `keydown` | Filtered by key name (e.g. `"Enter"`, `"Escape"`) |
+| `OnFocus()` | `focus` | |
+| `OnBlur()` | `blur` | |
+| `OnMouseEnter()` | `mouseenter` | |
+| `OnMouseLeave()` | `mouseleave` | |
+| `OnScroll()` | `scroll` | |
+
+### Trigger options
+
+Every trigger method accepts `ActionTriggerOption` values:
+
+```go
+// Set a signal value before the action fires
+submit.OnClick(via.WithSignal(mode, "delete"))
+submit.OnClick(via.WithSignalInt(page, 3))
+
+// Listen on window instead of the element
+submit.OnKeyDown("Escape", via.WithWindow())
+
+// Prevent browser default behavior
+submit.OnKeyDown("ArrowDown", via.WithPreventDefault())
+```
+
+### Multi-key dispatch
+
+`OnKeyDownMap` binds multiple keys to different actions in a single attribute:
+
+```go
+via.OnKeyDownMap(
+    via.KeyBind("w", move, via.WithSignal(dir, "up")),
+    via.KeyBind("s", move, via.WithSignal(dir, "down")),
+    via.KeyBind("ArrowUp", move, via.WithSignal(dir, "up"), via.WithPreventDefault()),
+    via.KeyBind("ArrowDown", move, via.WithSignal(dir, "down"), via.WithPreventDefault()),
+)
+```
+
+This produces a single `data-on:keydown__window` attribute. Place it on any element in the view.
+
+### Action options
+
+```go
+// Per-action rate limiting (overrides the context-level default)
+c.Action(handler, via.WithRateLimit(5, 10))
+
+// Per-action middleware (runs after CSRF and rate-limit checks)
+c.Action(handler, via.WithMiddleware(requireAdmin))
+```
+
+## Views and Sync
+
+Every page handler must call `c.View()` to define the UI:
+
+```go
+c.View(func() h.H {
+    return h.Div(
+        h.P(h.Textf("Hello, %s!", name.String())),
+    )
+})
+```
+
+> **Gotcha:** If you forget `c.View()`, the app panics at startup during route registration — not at request time.
+
+The view function is re-evaluated on every `c.Sync()`. The resulting HTML is pushed to the browser via SSE, where Datastar morphs the DOM.
+
+### Sync variants
+
+| Method | What it sends |
+|--------|---------------|
+| `c.Sync()` | Re-renders the view HTML **and** pushes changed signals |
+| `c.SyncSignals()` | Pushes only changed signals, no view re-render |
+| `c.SyncElements(elem...)` | Pushes specific HTML elements to merge into the DOM. Each element **must have an ID** matching an existing DOM element |
+| `c.ExecScript(js)` | Sends JavaScript for the browser to execute (auto-removed after execution) |
+
+Use `SyncSignals()` when only signal values changed and the view structure is the same. Use `SyncElements()` for targeted updates without re-rendering the entire view. Use `ExecScript()` to interact with client-side libraries (e.g. pushing data to a chart).
+
+## Components
+
+Extract reusable UI with `c.Component()`:
+
+```go
+func counterFn(c *via.Context) {
+    count := 0
+    step := c.Signal(1)
+
+    increment := c.Action(func() {
+        count += step.Int()
+        c.Sync()
+    })
+
+    c.View(func() h.H {
+        return h.Div(
+            h.P(h.Textf("Count: %d", count)),
+            h.Input(h.Type("number"), step.Bind()),
+            h.Button(h.Text("+"), increment.OnClick()),
+        )
+    })
+}
+
+// In a page:
+v.Page("/", func(c *via.Context) {
+    counter1 := c.Component(counterFn)
+    counter2 := c.Component(counterFn)
+
+    c.View(func() h.H {
+        return h.Div(
+            h.H2(h.Text("Counter 1")), counter1(),
+            h.H2(h.Text("Counter 2")), counter2(),
+        )
+    })
+})
+```
+
+Each component instance gets its own closure state, but signals, actions, and fields are registered on the parent page context. Components share the parent's SSE stream — `c.Sync()` from a component re-renders the entire page view.
+
+## Fields and Validation
+
+Fields are signals with validation rules. Use them for form inputs:
+
+```go
+username := c.Field("", via.Required(), via.MinLen(3), via.MaxLen(20))
+email := c.Field("", via.Required(), via.Email())
+age := c.Field("", via.Required(), via.Min(13), via.Max(120))
+website := c.Field("", via.Pattern(`^https?://`, "Must start with http:// or https://"))
+```
+
+### Built-in rules
+
+| Rule | Description |
+|------|-------------|
+| `Required(msg...)` | Rejects empty/whitespace-only values |
+| `MinLen(n, msg...)` | Minimum character count (Unicode-aware) |
+| `MaxLen(n, msg...)` | Maximum character count (Unicode-aware) |
+| `Min(n, msg...)` | Minimum numeric value (parsed as int) |
+| `Max(n, msg...)` | Maximum numeric value (parsed as int) |
+| `Email(msg...)` | Email format regex |
+| `Pattern(re, msg...)` | Custom regex |
+| `Custom(fn)` | `func(string) error` — return non-nil to fail |
+
+All rules accept an optional custom error message as the last argument.
+
+### Using fields in views and actions
+
+```go
+submit := c.Action(func() {
+    if !c.ValidateAll() {
+        c.Sync()
+        return
+    }
+    // Server-side validation
+    if userExists(username.String()) {
+        username.AddError("Username taken")
+        c.Sync()
+        return
+    }
+    createUser(username.String(), email.String())
+    c.ResetFields()
+    c.Sync()
+})
+
+c.View(func() h.H {
+    return h.Form(submit.OnSubmit(),
+        h.Input(h.Type("text"), username.Bind(), h.Placeholder("Username")),
+        h.If(username.HasError(), h.Small(h.Text(username.FirstError()))),
+
+        h.Input(h.Type("email"), email.Bind(), h.Placeholder("Email")),
+        h.If(email.HasError(), h.Small(h.Text(email.FirstError()))),
+
+        h.Button(h.Type("submit"), h.Text("Sign Up")),
+    )
+})
+```
+
+| Method | Description |
+|--------|-------------|
+| `field.Validate()` | Run rules, return true if all pass |
+| `field.HasError()` | True if any validation errors exist |
+| `field.FirstError()` | First error message, or `""` |
+| `field.Errors()` | All error messages |
+| `field.AddError(msg)` | Add a custom server-side error |
+| `field.ClearErrors()` | Remove all errors |
+| `field.Reset()` | Restore initial value and clear errors |
+| `c.ValidateAll(fields...)` | Validate given fields (or all if none specified). Does not short-circuit — all fields get validated so all errors are populated |
+| `c.ResetFields(fields...)` | Reset given fields (or all if none specified) |
+
+Fields embed `*signal`, so `Bind()`, `Text()`, `String()`, `Int()`, `Bool()`, `SetValue()`, and `ID()` all work.
+
+## OnInterval
+
+Run a function at regular intervals, tied to the page lifecycle:
+
+```go
+stop := c.OnInterval(time.Second, func() {
+    now = time.Now()
+    c.Sync()
+})
+```
+
+- Starts immediately — no separate start call needed.
+- Returns a `func()` that stops the interval (idempotent).
+- Automatically stops on context disposal (tab close) or SPA navigation away.
+- Call `c.Sync()` inside the handler to push updates to the browser.
+
+## Navigation Helpers
+
+| Method | Effect |
+|--------|--------|
+| `c.Redirect(url)` | Full page navigation. Disposes the context, browser loads a new page |
+| `c.Redirectf(fmt, args...)` | `Redirect` with `fmt.Sprintf` |
+| `c.RedirectView(url)` | Sets the view to trigger a redirect on SSE connect. Use in [middleware](routing-and-navigation.md#middleware) to abort the chain and redirect |
+| `c.ReplaceURL(url)` | Updates the browser URL bar without navigation. Useful for reflecting state in query params |
+| `c.ReplaceURLf(fmt, args...)` | `ReplaceURL` with `fmt.Sprintf` |
+| `c.Navigate(path, popstate)` | [SPA navigation](routing-and-navigation.md#spa-navigation). Resets page state, runs the target page handler on the same context, pushes the new view with a view transition |
+
+> **Gotcha:** In middleware, use `c.RedirectView()`, not `c.Redirect()`. `Redirect` sends a patch over SSE, but the SSE connection isn't established yet during the initial page load.