fix: nil-close bug, stale docs, dead code, and tracked binaries (#7)

Provides a Go API for interactive maps within Via applications:
- Plugin serves vendored MapLibre GL JS v4.7.1 assets
- Map struct with pre/post-render source, layer, marker, popup management
- Viewport signal sync (center, zoom, bearing, pitch) via hidden inputs
- FlyTo, SetCenter, SetZoom and other viewport setters via ExecScript
- Idempotent init script with SPA cleanup via MutationObserver
- Example app demonstrating markers, GeoJSON layers, and FlyTo actions

.claude/commands/pr.md

@@ -0,0 +1,14 @@
+Create a PR on Gitea, wait for CI, and squash-merge it. Push code to both remotes.
+
+1. If in a worktree (working directory contains `.claude/worktrees/`), you are already on a feature branch — do NOT create a new one. Otherwise, create a new branch from main with a descriptive name.
+2. Stage and commit all changes with a clean, semantic commit message. No Claude attribution lines.
+3. Fetch latest main and rebase: `git fetch gitea main && git rebase gitea/main`.
+   - If conflicts occur, abort the rebase (`git rebase --abort`), analyze the conflicting files, write a plan to resolve them, and present the plan to the user before proceeding.
+4. Push the branch to both remotes: `git push -u gitea <branch> && git push origin <branch>` (use `--force-with-lease` if already pushed).
+5. Create a Gitea PR: `tea pr create --head <branch> --base main`. Reference related issues with `#X`. Only use `Closes #X` if the PR fully resolves the issue.
+6. Wait for CI to pass: poll Gitea CI status. If CI fails, report the failure and stop — do not merge.
+7. Once CI passes, squash-merge on Gitea: `tea pr merge <index> --style squash` with a clean, semantic commit message including the PR number. No Claude attribution lines.
+8. Update local main and push to both remotes. If in a worktree, `main` is checked out in the primary tree, so run from there: `cd <primary-worktree> && git pull gitea main && git push origin main` (the primary worktree path is the repo root without `.claude/worktrees/…`). If not in a worktree: `git checkout main && git pull gitea main && git push origin main`.
+9. Clean up remote branches: `git push gitea --delete <branch> && git push origin --delete <branch>`.
+10. Prune refs: `git remote prune gitea && git remote prune origin`.
+11. Report the merged PR URL.

.claude/commands/release.md

@@ -0,0 +1,20 @@
+Create a new release on Gitea. Push tags to both remotes.
+
+## Pre-flight
+
+1. **Worktree guard**: If the working directory is inside `.claude/worktrees/`, STOP and tell the user: "Releases must be created from a non-worktree session on main. Exit this worktree or start a new session, then run /release." Do not proceed.
+2. Verify you are on `main`. If not, STOP.
+3. Verify there are no uncommitted changes. If there are, STOP — they should go through a PR.
+4. Run `git pull --ff-only` on main. Fetch tags from all remotes.
+
+## Release
+
+5. Review commits since the last tag. Recommend a semver bump:
+   - **major**: breaking/incompatible API changes
+   - **minor**: new features, meaningful new behavior
+   - **patch**: bug fixes, docs, refactoring with no new features
+   Present the proposed version, bump rationale, and commit list. Wait for user approval.
+6. Tag the new version. Push the tag to both remotes: `git push gitea <tag> && git push origin <tag>`.
+7. Generate release notes grouped by type (features, fixes, chores).
+8. Create a Gitea release with `tea releases create` using the notes.
+9. Report the release URL and confirm all remotes are up to date.

.gitea/workflows/ci.yml

@@ -8,9 +8,6 @@ on:
     branches:
       - '**'
 
-permissions:
-  contents: read
-
 jobs:
   build-test:
     name: Build and Test

.gitignore

@@ -37,17 +37,12 @@ go.work.sum
 # Air artifacts
 *tmp/
 
-# binaries
-internal/examples/chatroom/chatroom
-internal/examples/counter/counter
-internal/examples/countercomp/countercomp
-internal/examples/greeter/greeter
-internal/examples/livereload/livereload
-internal/examples/picocss/picocss
-internal/examples/plugins/plugins
-internal/examples/realtimechart/realtimechart
-internal/examples/shakespeare/shakespeare
-internal/examples/nats-chatroom/nats-chatroom
+# Example binaries and data files
+internal/examples/*/[a-z]*[!.go]
+internal/examples/shakespeare/shake.db
 
 # NATS data directory
 data/
+
+# Claude Code worktrees
+.claude/worktrees/

CLAUDE.md

@@ -0,0 +1,20 @@
+# Via Project Instructions
+
+## Workflow
+
+All changes go through PRs:
+
+1. Enter a worktree (`EnterWorktree`) at session start.
+2. Make changes, commit with semantic messages.
+3. `/pr` to push, open a PR, wait for CI, and squash-merge.
+
+## Releasing
+
+Run `/release` from a **non-worktree session on main**. It tags and publishes
+what is already on main — it does not commit new changes.
+
+## Worktree Usage
+
+Always enter a worktree at the start of a session using the `EnterWorktree`
+tool. This prevents parallel Claude Code sessions from interfering with each
+other.

README.md

@@ -74,14 +74,13 @@ func main() {
 - **Plugin system** — `func(v *V)` hooks for integrating CSS/JS libraries
 - **Structured logging** — zerolog with configurable levels; console output in dev, JSON in production
 - **Graceful shutdown** — listens for SIGINT/SIGTERM, drains contexts, closes pub/sub
-- **Context lifecycle** — background reaper cleans up disconnected contexts; configurable TTL
 - **HTML DSL** — the `h` package provides type-safe Go-native HTML composition
 
 ## Examples
 
-The `internal/examples/` directory contains 14 runnable examples:
+The `internal/examples/` directory contains 19 runnable examples:
 
-`chatroom` · `counter` · `countercomp` · `greeter` · `keyboard` · `livereload` · `nats-chatroom` · `pathparams` · `picocss` · `plugins` · `pubsub-crud` · `realtimechart` · `session` · `shakespeare`
+`chatroom` · `counter` · `countercomp` · `effectspike` · `greeter` · `keyboard` · `livereload` · `maplibre` · `middleware` · `nats-chatroom` · `pathparams` · `picocss` · `plugins` · `pubsub-crud` · `realtimechart` · `session` · `shakespeare` · `signup` · `spa`
 
 ## Experimental
 

actiontrigger.go

@@ -3,6 +3,7 @@ package via
 import (
 	"fmt"
 	"strconv"
+	"time"
 
 	"github.com/ryanhamamura/via/h"
 )
@@ -23,6 +24,8 @@ type triggerOpts struct {
 	value          string
 	window         bool
 	preventDefault bool
+	debounce       time.Duration
+	throttle       time.Duration
 }
 
 type withSignalOpt struct {
@@ -58,8 +61,43 @@ func WithPreventDefault() ActionTriggerOption {
 	return withPreventDefaultOpt{}
 }
 
+type withDebounceOpt struct{ d time.Duration }
+
+func (o withDebounceOpt) apply(opts *triggerOpts) { opts.debounce = o.d }
+
+// WithDebounce adds a debounce modifier to the event trigger.
+func WithDebounce(d time.Duration) ActionTriggerOption { return withDebounceOpt{d} }
+
+type withThrottleOpt struct{ d time.Duration }
+
+func (o withThrottleOpt) apply(opts *triggerOpts) { opts.throttle = o.d }
+
+// WithThrottle adds a throttle modifier to the event trigger.
+func WithThrottle(d time.Duration) ActionTriggerOption { return withThrottleOpt{d} }
+
+// formatDuration renders a duration as e.g. "200ms" for Datastar modifiers.
+func formatDuration(d time.Duration) string {
+	return fmt.Sprintf("%dms", d.Milliseconds())
+}
+
+// buildAttrKey constructs a Datastar attribute key with modifiers.
+// Order: event → debounce/throttle → window.
+func buildAttrKey(event string, opts *triggerOpts) string {
+	key := "on:" + event
+	if opts.debounce > 0 {
+		key += "__debounce." + formatDuration(opts.debounce)
+	}
+	if opts.throttle > 0 {
+		key += "__throttle." + formatDuration(opts.throttle)
+	}
+	if opts.window {
+		key += "__window"
+	}
+	return key
+}
+
 // WithSignal sets a signal value before triggering the action.
-func WithSignal(sig *signal, value string) ActionTriggerOption {
+func WithSignal(sig *Signal, value string) ActionTriggerOption {
 	return withSignalOpt{
 		signalID: sig.ID(),
 		value:    fmt.Sprintf("'%s'", value),
@@ -67,7 +105,7 @@ func WithSignal(sig *signal, value string) ActionTriggerOption {
 }
 
 // WithSignalInt sets a signal to an int value before triggering the action.
-func WithSignalInt(sig *signal, value int) ActionTriggerOption {
+func WithSignalInt(sig *Signal, value int) ActionTriggerOption {
 	return withSignalOpt{
 		signalID: sig.ID(),
 		value:    strconv.Itoa(value),
@@ -97,62 +135,62 @@ func actionURL(id string) string {
 // to element nodes in a view.
 func (a *actionTrigger) OnClick(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:click", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("click", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnChange returns a via.h DOM attribute that triggers on input change. It can be added
 // to element nodes in a view.
 func (a *actionTrigger) OnChange(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:change__debounce.200ms", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("change", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnSubmit returns a via.h DOM attribute that triggers on form submit.
 func (a *actionTrigger) OnSubmit(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:submit", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("submit", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnInput returns a via.h DOM attribute that triggers on input (without debounce).
 func (a *actionTrigger) OnInput(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:input", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("input", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnFocus returns a via.h DOM attribute that triggers when the element gains focus.
 func (a *actionTrigger) OnFocus(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:focus", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("focus", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnBlur returns a via.h DOM attribute that triggers when the element loses focus.
 func (a *actionTrigger) OnBlur(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:blur", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("blur", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnMouseEnter returns a via.h DOM attribute that triggers when the mouse enters the element.
 func (a *actionTrigger) OnMouseEnter(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:mouseenter", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("mouseenter", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnMouseLeave returns a via.h DOM attribute that triggers when the mouse leaves the element.
 func (a *actionTrigger) OnMouseLeave(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:mouseleave", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("mouseleave", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnScroll returns a via.h DOM attribute that triggers on scroll.
 func (a *actionTrigger) OnScroll(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:scroll", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("scroll", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnDblClick returns a via.h DOM attribute that triggers on double click.
 func (a *actionTrigger) OnDblClick(options ...ActionTriggerOption) h.H {
 	opts := applyOptions(options...)
-	return h.Data("on:dblclick", buildOnExpr(actionURL(a.id), &opts))
+	return h.Data(buildAttrKey("dblclick", &opts), buildOnExpr(actionURL(a.id), &opts))
 }
 
 // OnKeyDown returns a via.h DOM attribute that triggers when a key is pressed.
@@ -164,11 +202,7 @@ func (a *actionTrigger) OnKeyDown(key string, options ...ActionTriggerOption) h.
 	if key != "" {
 		condition = fmt.Sprintf("evt.key==='%s' &&", key)
 	}
-	attrName := "on:keydown"
-	if opts.window {
-		attrName = "on:keydown__window"
-	}
-	return h.Data(attrName, fmt.Sprintf("%s%s", condition, buildOnExpr(actionURL(a.id), &opts)))
+	return h.Data(buildAttrKey("keydown", &opts), fmt.Sprintf("%s%s", condition, buildOnExpr(actionURL(a.id), &opts)))
 }
 
 // KeyBinding pairs a key with an action and per-binding options.

ci-check.sh

@@ -6,9 +6,13 @@ set -o pipefail
 ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 cd "$ROOT"
 
-echo "== CI: Format code =="
-go fmt ./...
-echo "OK: formatting complete"
+echo "== CI: Check formatting =="
+if [ -n "$(gofmt -l .)" ]; then
+  echo "ERROR: files not formatted:"
+  gofmt -l .
+  exit 1
+fi
+echo "OK: all files formatted"
 
 echo "== CI: Run go vet =="
 if ! go vet ./...; then

computed.go

@@ -0,0 +1,54 @@
+package via
+
+import (
+	"strconv"
+	"strings"
+
+	"github.com/ryanhamamura/via/h"
+)
+
+// computedSignal is a read-only signal whose value is derived from other signals.
+// It recomputes on every read and is included in patches only when the value changes.
+type computedSignal struct {
+	id      string
+	compute func() string
+	lastVal string
+	changed bool
+}
+
+func (s *computedSignal) ID() string {
+	return s.id
+}
+
+func (s *computedSignal) String() string {
+	return s.compute()
+}
+
+func (s *computedSignal) Int() int {
+	if n, err := strconv.Atoi(s.String()); err == nil {
+		return n
+	}
+	return 0
+}
+
+func (s *computedSignal) Bool() bool {
+	val := strings.ToLower(s.String())
+	return val == "true" || val == "1" || val == "yes" || val == "on"
+}
+
+func (s *computedSignal) Text() h.H {
+	return h.Span(h.Data("text", "$"+s.id))
+}
+
+// recompute calls the compute function and sets changed if the value differs from lastVal.
+func (s *computedSignal) recompute() {
+	val := s.compute()
+	if val != s.lastVal {
+		s.lastVal = val
+		s.changed = true
+	}
+}
+
+func (s *computedSignal) patchValue() string {
+	return s.lastVal
+}

computed_test.go

@@ -0,0 +1,190 @@
+package via
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+
+	"github.com/ryanhamamura/via/h"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestComputedBasic(t *testing.T) {
+	v := New()
+	var cs *computedSignal
+	v.Page("/", func(c *Context) {
+		sig1 := c.Signal("hello")
+		sig2 := c.Signal("world")
+		cs = c.Computed(func() string {
+			return sig1.String() + " " + sig2.String()
+		})
+		c.View(func() h.H { return h.Div() })
+	})
+	assert.Equal(t, "hello world", cs.String())
+}
+
+func TestComputedReactivity(t *testing.T) {
+	v := New()
+	var cs *computedSignal
+	var sig1 *Signal
+	v.Page("/", func(c *Context) {
+		sig1 = c.Signal("a")
+		sig2 := c.Signal("b")
+		cs = c.Computed(func() string {
+			return sig1.String() + sig2.String()
+		})
+		c.View(func() h.H { return h.Div() })
+	})
+	assert.Equal(t, "ab", cs.String())
+	sig1.SetValue("x")
+	assert.Equal(t, "xb", cs.String())
+}
+
+func TestComputedInt(t *testing.T) {
+	v := New()
+	var cs *computedSignal
+	v.Page("/", func(c *Context) {
+		sig := c.Signal(21)
+		cs = c.Computed(func() string {
+			return fmt.Sprintf("%d", sig.Int()*2)
+		})
+		c.View(func() h.H { return h.Div() })
+	})
+	assert.Equal(t, 42, cs.Int())
+}
+
+func TestComputedBool(t *testing.T) {
+	v := New()
+	var cs *computedSignal
+	v.Page("/", func(c *Context) {
+		sig := c.Signal("true")
+		cs = c.Computed(func() string {
+			return sig.String()
+		})
+		c.View(func() h.H { return h.Div() })
+	})
+	assert.True(t, cs.Bool())
+}
+
+func TestComputedText(t *testing.T) {
+	v := New()
+	var cs *computedSignal
+	v.Page("/", func(c *Context) {
+		cs = c.Computed(func() string { return "hi" })
+		c.View(func() h.H { return h.Div() })
+	})
+
+	var buf bytes.Buffer
+	err := cs.Text().Render(&buf)
+	assert.NoError(t, err)
+	assert.Contains(t, buf.String(), `data-text="$`+cs.ID()+`"`)
+}
+
+func TestComputedChangeDetection(t *testing.T) {
+	v := New()
+	var ctx *Context
+	var sig *Signal
+	v.Page("/", func(c *Context) {
+		ctx = c
+		sig = c.Signal("a")
+		c.Computed(func() string {
+			return sig.String() + "!"
+		})
+		c.View(func() h.H { return h.Div() })
+	})
+
+	// First patch includes computed (changed=true from init)
+	patch1 := ctx.prepareSignalsForPatch()
+	assert.NotEmpty(t, patch1)
+
+	// Second patch: nothing changed, computed should not be included
+	patch2 := ctx.prepareSignalsForPatch()
+	// Regular signal still has changed=true (not reset in prepareSignalsForPatch),
+	// but computed should not appear since its value didn't change.
+	hasComputed := false
+	ctx.signals.Range(func(_, value any) bool {
+		if cs, ok := value.(*computedSignal); ok {
+			_, inPatch := patch2[cs.ID()]
+			hasComputed = inPatch
+		}
+		return true
+	})
+	assert.False(t, hasComputed)
+
+	// After changing dependency, computed should reappear
+	sig.SetValue("b")
+	patch3 := ctx.prepareSignalsForPatch()
+	found := false
+	ctx.signals.Range(func(_, value any) bool {
+		if cs, ok := value.(*computedSignal); ok {
+			if v, ok := patch3[cs.ID()]; ok {
+				assert.Equal(t, "b!", v)
+				found = true
+			}
+		}
+		return true
+	})
+	assert.True(t, found)
+}
+
+func TestComputedInComponent(t *testing.T) {
+	v := New()
+	var cs *computedSignal
+	var parentCtx *Context
+	v.Page("/", func(c *Context) {
+		parentCtx = c
+		c.Component(func(comp *Context) {
+			sig := comp.Signal("via")
+			cs = comp.Computed(func() string {
+				return "hello " + sig.String()
+			})
+			comp.View(func() h.H { return h.Div() })
+		})
+		c.View(func() h.H { return h.Div() })
+	})
+
+	assert.Equal(t, "hello via", cs.String())
+	// Verify it's stored on the parent page context
+	found := false
+	parentCtx.signals.Range(func(_, value any) bool {
+		if stored, ok := value.(*computedSignal); ok && stored.ID() == cs.ID() {
+			found = true
+		}
+		return true
+	})
+	assert.True(t, found)
+}
+
+func TestComputedIsReadOnly(t *testing.T) {
+	// Compile-time guarantee: *computedSignal has no Bind() or SetValue() methods.
+	// This test exists as documentation — if someone adds those methods, the
+	// interface assertion below will need updating and serve as a reminder.
+	var cs interface{} = &computedSignal{}
+	type writable interface {
+		SetValue(any)
+	}
+	type bindable interface {
+		Bind() h.H
+	}
+	_, isWritable := cs.(writable)
+	_, isBindable := cs.(bindable)
+	assert.False(t, isWritable, "computedSignal must not have SetValue")
+	assert.False(t, isBindable, "computedSignal must not have Bind")
+}
+
+func TestComputedInjectSignalsSkips(t *testing.T) {
+	v := New()
+	var ctx *Context
+	var cs *computedSignal
+	v.Page("/", func(c *Context) {
+		ctx = c
+		cs = c.Computed(func() string { return "fixed" })
+		c.View(func() h.H { return h.Div() })
+	})
+
+	// Simulate browser sending back a value for the computed signal — should be ignored
+	ctx.injectSignals(map[string]any{
+		cs.ID(): "injected",
+	})
+	assert.Equal(t, "fixed", cs.String())
+}

configuration.go

@@ -1,8 +1,6 @@
 package via
 
 import (
-	"time"
-
 	"github.com/alexedwards/scs/v2"
 	"github.com/rs/zerolog"
 )
@@ -53,14 +51,14 @@ type Options struct {
 	// Defaults to "/_datastar.js" if empty.
 	DatastarPath string
 
-	// PubSub enables publish/subscribe messaging. Use vianats.New() for an
-	// embedded NATS backend, or supply any PubSub implementation.
+	// PubSub enables publish/subscribe messaging. When nil, an embedded NATS
+	// server starts automatically in Start(). Supply any PubSub implementation
+	// to replace it.
 	PubSub PubSub
 
-	// ContextTTL is the maximum time a context may exist without an SSE
-	// connection before the background reaper disposes it.
-	// Default: 30s. Negative value disables the reaper.
-	ContextTTL time.Duration
+	// Streams declares JetStream streams to create when Start() initializes
+	// the embedded NATS server. Ignored when a custom PubSub is configured.
+	Streams []StreamConfig
 
 	// ActionRateLimit configures the default token-bucket rate limiter for
 	// action endpoints. Zero values use built-in defaults (10 req/s, burst 20).

context.go

@@ -5,8 +5,8 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"net/url"
 	"reflect"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -31,6 +31,7 @@ type Context struct {
 	actionRegistry    map[string]actionEntry
 	signals           *sync.Map
 	mu                sync.RWMutex
+	navMu             sync.Mutex
 	ctxDisposedChan   chan struct{}
 	pageStopChan      chan struct{}
 	reqCtx            context.Context
@@ -40,6 +41,7 @@ type Context struct {
 	disposeOnce       sync.Once
 	createdAt         time.Time
 	sseConnected      atomic.Bool
+	sseDisconnectedAt atomic.Pointer[time.Time]
 }
 
 // View defines the UI rendered by this context.
@@ -171,11 +173,11 @@ func (c *Context) OnInterval(duration time.Duration, handler func()) func() {
 // the Context before each action call.
 // If any signal value is updated by the server, the update is automatically sent to the
 // browser when using Sync() or SyncSignsls().
-func (c *Context) Signal(v any) *signal {
+func (c *Context) Signal(v any) *Signal {
 	sigID := genRandID()
 	if v == nil {
 		c.app.logErr(c, "failed to bind signal: nil signal value")
-		return &signal{
+		return &Signal{
 			id:  sigID,
 			val: "error",
 			err: fmt.Errorf("context '%s' failed to bind signal '%s': nil signal value", c.id, sigID),
@@ -187,7 +189,7 @@ func (c *Context) Signal(v any) *signal {
 			v = string(j)
 		}
 	}
-	sig := &signal{
+	sig := &Signal{
 		id:      sigID,
 		val:     v,
 		changed: true,
@@ -204,6 +206,40 @@ func (c *Context) Signal(v any) *signal {
 
 }
 
+// Computed creates a read-only signal whose value is derived from the given function.
+// The function is called on every read (String/Int/Bool) for fresh values,
+// and during sync to detect changes for browser patches.
+//
+// Computed signals cannot be bound to inputs or set manually.
+//
+// Example:
+//
+//	full := c.Computed(func() string {
+//	    return first.String() + " " + last.String()
+//	})
+//	c.View(func() h.H {
+//	    return h.Span(full.Text())
+//	})
+func (c *Context) Computed(fn func() string) *computedSignal {
+	sigID := genRandID()
+	initial := fn()
+	cs := &computedSignal{
+		id:      sigID,
+		compute: fn,
+		lastVal: initial,
+		changed: true,
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.isComponent() {
+		c.parentPageCtx.signals.Store(sigID, cs)
+	} else {
+		c.signals.Store(sigID, cs)
+	}
+	return cs
+}
+
 func (c *Context) injectSignals(sigs map[string]any) {
 	if sigs == nil {
 		c.app.logErr(c, "signal injection failed: nil signals")
@@ -216,13 +252,13 @@ func (c *Context) injectSignals(sigs map[string]any) {
 	for sigID, val := range sigs {
 		item, ok := c.signals.Load(sigID)
 		if !ok {
-			c.signals.Store(sigID, &signal{
+			c.signals.Store(sigID, &Signal{
 				id:  sigID,
 				val: val,
 			})
 			continue
 		}
-		if sig, ok := item.(*signal); ok {
+		if sig, ok := item.(*Signal); ok {
 			sig.val = val
 			sig.changed = false
 		}
@@ -245,13 +281,21 @@ func (c *Context) prepareSignalsForPatch() map[string]any {
 	defer c.mu.RUnlock()
 	updatedSigs := make(map[string]any)
 	c.signals.Range(func(sigID, value any) bool {
-		if sig, ok := value.(*signal); ok {
+		switch sig := value.(type) {
+		case *Signal:
 			if sig.err != nil {
 				c.app.logWarn(c, "signal '%s' is out of sync: %v", sig.id, sig.err)
 				return true
 			}
 			if sig.changed {
 				updatedSigs[sigID.(string)] = fmt.Sprintf("%v", sig.val)
+				sig.changed = false
+			}
+		case *computedSignal:
+			sig.recompute()
+			if sig.changed {
+				updatedSigs[sigID.(string)] = sig.patchValue()
+				sig.changed = false
 			}
 		}
 		return true
@@ -272,15 +316,22 @@ func (c *Context) sendPatch(p patch) {
 // Sync pushes the current view state and signal changes to the browser immediately
 // over the live SSE event stream.
 func (c *Context) Sync() {
+	c.syncView(false)
+}
+
+func (c *Context) syncView(viewTransition bool) {
 	elemsPatch := new(bytes.Buffer)
 	if err := c.view().Render(elemsPatch); err != nil {
 		c.app.logErr(c, "sync view failed: %v", err)
 		return
 	}
-	c.sendPatch(patch{patchTypeElements, elemsPatch.String()})
+	typ := patchType(patchTypeElements)
+	if viewTransition {
+		typ = patchTypeElementsWithVT
+	}
+	c.sendPatch(patch{typ, elemsPatch.String()})
 
 	updatedSigs := c.prepareSignalsForPatch()
-
 	if len(updatedSigs) != 0 {
 		outgoingSigs, _ := json.Marshal(updatedSigs)
 		c.sendPatch(patch{patchTypeSignals, string(outgoingSigs)})
@@ -396,6 +447,9 @@ func (c *Context) resetPageState() {
 // view over the existing SSE connection with a view transition animation.
 // If popstate is true, replaceState is used instead of pushState.
 func (c *Context) Navigate(path string, popstate bool) {
+	c.navMu.Lock()
+	defer c.navMu.Unlock()
+
 	route, initFn, params := c.app.matchRoute(path)
 	if initFn == nil {
 		c.Redirect(path)
@@ -405,29 +459,12 @@ func (c *Context) Navigate(path string, popstate bool) {
 	c.route = route
 	c.injectRouteParams(params)
 	initFn(c)
-	c.syncWithViewTransition()
-	escaped := url.PathEscape(path)
+	c.syncView(true)
+	safe := strings.NewReplacer(`\`, `\\`, `'`, `\'`).Replace(path)
 	if popstate {
-		c.ExecScript(fmt.Sprintf("history.replaceState({},'',decodeURIComponent('%s'))", escaped))
+		c.ExecScript(fmt.Sprintf("history.replaceState({},'','%s')", safe))
 	} else {
-		c.ExecScript(fmt.Sprintf("history.pushState({},'',decodeURIComponent('%s'))", escaped))
-	}
-}
-
-// syncWithViewTransition renders the view and sends it as a PatchElements
-// with the view transition flag, plus any changed signals.
-func (c *Context) syncWithViewTransition() {
-	elemsPatch := new(bytes.Buffer)
-	if err := c.view().Render(elemsPatch); err != nil {
-		c.app.logErr(c, "sync view failed: %v", err)
-		return
-	}
-	c.sendPatch(patch{patchTypeElementsWithVT, elemsPatch.String()})
-
-	updatedSigs := c.prepareSignalsForPatch()
-	if len(updatedSigs) != 0 {
-		outgoingSigs, _ := json.Marshal(updatedSigs)
-		c.sendPatch(patch{patchTypeSignals, string(outgoingSigs)})
+		c.ExecScript(fmt.Sprintf("history.pushState({},'','%s')", safe))
 	}
 }
 
@@ -549,7 +586,7 @@ func (c *Context) unsubscribeAll() {
 // can operate on all fields by default.
 func (c *Context) Field(initial any, rules ...Rule) *Field {
 	f := &Field{
-		signal:     c.Signal(initial),
+		Signal:     c.Signal(initial),
 		rules:      rules,
 		initialVal: initial,
 	}

docs/getting-started.md

@@ -0,0 +1,177 @@
+# 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,
+    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) |
+| `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

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"
+```

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

docs/pubsub-and-sessions.md

@@ -0,0 +1,264 @@
+# PubSub and Sessions
+
+Infrastructure for multi-user real-time communication and persistent state.
+
+## PubSub
+
+Via includes an embedded NATS server that starts automatically with `v.Start()`. 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.
+
+### Declaring streams
+
+The recommended approach is to declare streams in `Options.Streams`. They are created automatically when `v.Start()` initializes the embedded NATS server:
+
+```go
+v.Config(via.Options{
+    Streams: []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 |
+
+For dynamic stream creation after startup, `EnsureStream` is also available:
+
+```go
+err := via.EnsureStream(v, via.StreamConfig{
+    Name:     "EVENTS",
+    Subjects: []string{"events.>"},
+    MaxMsgs:  500,
+    MaxAge:   12 * time.Hour,
+})
+```
+
+### 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).

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.

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 lives until the browser tab closes (detected via a `beforeunload` beacon) or the server shuts down. There is no background reaper — contexts persist across temporary SSE disconnections so backgrounded tabs resume seamlessly.
+
+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` | |
+| `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.

field.go

@@ -1,10 +1,10 @@
 package via
 
 // Field is a signal with built-in validation rules and error state.
-// It embeds *signal, so all signal methods (Bind, String, Int, Bool, SetValue, Text, ID)
+// It embeds *Signal, so all signal methods (Bind, String, Int, Bool, SetValue, Text, ID)
 // work transparently.
 type Field struct {
-	*signal
+	*Signal
 	rules      []Rule
 	errors     []string
 	initialVal any

h/datastar.go

@@ -14,7 +14,8 @@ func DataIgnoreMorph() H {
 
 // DataViewTransition sets the view-transition-name CSS property on an element
 // via an inline style. Elements with matching names animate between pages
-// during SPA navigation.
+// during SPA navigation. If the element also needs other inline styles,
+// include view-transition-name directly in the Style() call instead.
 func DataViewTransition(name string) H {
 	return Attr("style", "view-transition-name: "+name)
 }

h/h.go

@@ -5,7 +5,7 @@
 //
 //	h.Div(
 //		h.H1(h.Text("Hello, Via")),
-//		h.P(h.Text("Pure Go. No tmplates.")),
+//		h.P(h.Text("Pure Go. No templates.")),
 //	)
 package h
 

internal/examples/effectspike/main.go

@@ -0,0 +1,52 @@
+// Spike to validate that Datastar's data-effect re-evaluates when signals are
+// updated via PatchSignals from the server, and that Via's hex signal IDs work
+// in $signalID expression syntax.
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"time"
+
+	"github.com/ryanhamamura/via"
+	"github.com/ryanhamamura/via/h"
+)
+
+func main() {
+	v := via.New()
+	v.Config(via.Options{
+		DocumentTitle: "data-effect Spike",
+		ServerAddress: ":7332",
+		DevMode:       true,
+	})
+
+	v.Page("/", func(c *via.Context) {
+		x := c.Signal(0)
+		y := c.Signal(0)
+
+		c.OnInterval(time.Second, func() {
+			x.SetValue(rand.Intn(500))
+			y.SetValue(rand.Intn(500))
+			c.SyncSignals()
+		})
+
+		c.View(func() h.H {
+			return h.Div(
+				h.Attr("style", "padding:1rem;font-family:sans-serif"),
+				h.H1(h.Text("data-effect Spike")),
+				h.P(h.Text("x: "), x.Text(), h.Text(" y: "), y.Text()),
+				h.Div(
+					h.ID("box"),
+					h.Attr("style", "width:20px;height:20px;background:red;position:absolute"),
+					h.DataEffect(fmt.Sprintf(
+						"document.getElementById('box').style.left=$%s+'px';"+
+							"document.getElementById('box').style.top=$%s+'px'",
+						x.ID(), y.ID(),
+					)),
+				),
+			)
+		})
+	})
+
+	v.Start()
+}

internal/examples/livereload/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"github.com/ryanhamamura/via"
-	// "github.com/go-via/via-plugin-picocss/picocss"
 	"github.com/ryanhamamura/via/h"
 )
 
@@ -15,9 +14,6 @@ func main() {
 		DocumentTitle: "Live Reload Demo",
 		DevMode:       true,
 		LogLevel:      via.LogLevelDebug,
-		Plugins:       []via.Plugin{
-			// picocss.Default
-		},
 	})
 
 	v.Page("/", func(c *via.Context) {

internal/examples/maplibre/main.go

@@ -0,0 +1,154 @@
+package main
+
+import (
+	"math/rand"
+	"time"
+
+	"github.com/ryanhamamura/via"
+	"github.com/ryanhamamura/via/h"
+	"github.com/ryanhamamura/via/maplibre"
+)
+
+func main() {
+	v := via.New()
+	v.Config(via.Options{
+		DocumentTitle: "MapLibre GL Example",
+		ServerAddress: ":7331",
+		DevMode:       true,
+		Plugins:       []via.Plugin{maplibre.Plugin},
+	})
+
+	v.Page("/", func(c *via.Context) {
+		m := maplibre.New(c, maplibre.Options{
+			Style:  "https://demotiles.maplibre.org/style.json",
+			Center: maplibre.LngLat{Lng: -122.4194, Lat: 37.7749},
+			Zoom:   10,
+			Height: "500px",
+		})
+
+		m.AddControl("nav", maplibre.NavigationControl{})
+		m.AddControl("scale", maplibre.ScaleControl{Unit: "metric"})
+
+		// Static markers with popups
+		m.AddMarker("sf", maplibre.Marker{
+			LngLat: maplibre.LngLat{Lng: -122.4194, Lat: 37.7749},
+			Color:  "#e74c3c",
+			Popup: &maplibre.Popup{
+				Content: "<strong>San Francisco</strong><p>The Golden City</p>",
+			},
+		})
+		m.AddMarker("oak", maplibre.Marker{
+			LngLat: maplibre.LngLat{Lng: -122.2711, Lat: 37.8044},
+			Color:  "#2ecc71",
+			Popup: &maplibre.Popup{
+				Content: "<strong>Oakland</strong>",
+			},
+		})
+
+		// Signal-backed marker — server pushes position updates
+		vehicleLng := c.Signal(-122.43)
+		vehicleLat := c.Signal(37.77)
+
+		m.AddMarker("vehicle", maplibre.Marker{
+			LngSignal: vehicleLng,
+			LatSignal: vehicleLat,
+			Color:     "#9b59b6",
+		})
+
+		c.OnInterval(time.Second, func() {
+			vehicleLng.SetValue(-122.43 + (rand.Float64()-0.5)*0.02)
+			vehicleLat.SetValue(37.77 + (rand.Float64()-0.5)*0.02)
+			c.SyncSignals()
+		})
+
+		// Draggable marker — user drags, signals update
+		pinLng := c.Signal(-122.41)
+		pinLat := c.Signal(37.78)
+
+		m.AddMarker("pin", maplibre.Marker{
+			LngSignal: pinLng,
+			LatSignal: pinLat,
+			Color:     "#3498db",
+			Draggable: true,
+		})
+
+		// Click event — click to place a marker
+		click := m.OnClick()
+		handleClick := c.Action(func() {
+			e := click.Data()
+			m.AddMarker("clicked", maplibre.Marker{
+				LngLat: e.LngLat,
+				Color:  "#f39c12",
+			})
+		})
+
+		// GeoJSON polygon source + fill layer
+		m.AddSource("park", maplibre.GeoJSONSource{
+			Data: map[string]any{
+				"type": "Feature",
+				"geometry": map[string]any{
+					"type": "Polygon",
+					"coordinates": []any{[]any{
+						[]float64{-122.4547, 37.7654},
+						[]float64{-122.4547, 37.7754},
+						[]float64{-122.4387, 37.7754},
+						[]float64{-122.4387, 37.7654},
+						[]float64{-122.4547, 37.7654},
+					}},
+				},
+				"properties": map[string]any{
+					"name": "Golden Gate Park",
+				},
+			},
+		})
+		m.AddLayer(maplibre.Layer{
+			ID:     "park-fill",
+			Type:   "fill",
+			Source: "park",
+			Paint: map[string]any{
+				"fill-color":   "#2ecc71",
+				"fill-opacity": 0.3,
+			},
+		})
+
+		// FlyTo actions using CameraOptions
+		zoom14 := 14.0
+		flyToSF := c.Action(func() {
+			m.FlyTo(maplibre.CameraOptions{
+				Center: &maplibre.LngLat{Lng: -122.4194, Lat: 37.7749},
+				Zoom:   &zoom14,
+			})
+		})
+
+		flyToOak := c.Action(func() {
+			m.FlyTo(maplibre.CameraOptions{
+				Center: &maplibre.LngLat{Lng: -122.2711, Lat: 37.8044},
+				Zoom:   &zoom14,
+			})
+		})
+
+		c.View(func() h.H {
+			return h.Div(
+				h.Div(
+					h.Attr("style", "max-width:960px;margin:0 auto;padding:1rem;font-family:sans-serif"),
+					h.H1(h.Text("MapLibre GL Example")),
+					m.Element(
+						click.Input(handleClick.OnInput()),
+					),
+					h.Div(h.Attr("style", "margin-top:1rem;display:flex;gap:0.5rem;flex-wrap:wrap"),
+						h.Button(h.Text("Fly to San Francisco"), flyToSF.OnClick()),
+						h.Button(h.Text("Fly to Oakland"), flyToOak.OnClick()),
+					),
+					h.Div(h.Attr("style", "margin-top:0.5rem;font-size:0.9rem"),
+						h.P(h.Text("Zoom: "), m.Zoom.Text()),
+						h.P(h.Text("Center: "), m.CenterLng.Text(), h.Text(", "), m.CenterLat.Text()),
+						h.P(h.Text("Vehicle: "), vehicleLng.Text(), h.Text(", "), vehicleLat.Text()),
+						h.P(h.Text("Draggable Pin: "), pinLng.Text(), h.Text(", "), pinLat.Text()),
+					),
+				),
+			)
+		})
+	})
+
+	v.Start()
+}

internal/examples/nats-chatroom/README.md

@@ -2,7 +2,7 @@
 
 A chatroom built with Via and an **embedded NATS server**, demonstrating pub/sub messaging as an alternative to the custom `Rooms` implementation in `../chatroom`.
 
-Uses `delaneyj/toolbelt/embeddednats` to run NATS inside the same binary - no external server required.
+Via includes an embedded NATS server that starts automatically — no external server required.
 
 ## Key Differences from Original Chatroom
 
@@ -25,21 +25,6 @@ That's it. No separate NATS server needed.
 
 Open multiple browser tabs at http://localhost:7331 to see messages broadcast across all clients.
 
-## How Embedded NATS Works
-
-```go
-// Start embedded NATS server (JetStream enabled by default)
-ns, err := embeddednats.New(ctx,
-    embeddednats.WithDirectory("./data/nats"),
-)
-ns.WaitForServer()
-
-// Get client connection to embedded server
-nc, err := ns.Client()
-```
-
-Data is persisted to `./data/nats/` for JetStream durability.
-
 ## Architecture
 
 ```
@@ -65,14 +50,16 @@ Data is persisted to `./data/nats/` for JetStream durability.
 
 ## JetStream Durability
 
-Messages persist to disk via JetStream:
+Messages persist to disk via JetStream. Streams are declared in `Options.Streams` and created automatically when `v.Start()` initializes the embedded NATS server:
 
 ```go
-js.AddStream(&nats.StreamConfig{
+v.Config(via.Options{
+    Streams: []via.StreamConfig{{
         Name:     "CHAT",
         Subjects: []string{"chat.>"},
-    MaxMsgs:   1000,  // Keep last 1000 messages
+        MaxMsgs:  1000,
         MaxAge:   24 * time.Hour,
+    }},
 })
 ```
 
@@ -87,23 +74,6 @@ Stop and restart the app - chat history survives.
 - Manual join/leave channels
 
 **This example - ~60 lines of NATS integration:**
-- `embeddednats.New()` starts the server
-- `nc.Subscribe(subject, handler)` for receiving
-- `nc.Publish(subject, data)` for sending
-- NATS handles delivery, no polling
-
-## Next Steps
-
-If this pattern proves useful, it could be promoted to a Via plugin:
-
-```go
-// Hypothetical future API
-v.Config(via.WithEmbeddedNATS("./data/nats"))
-
-// In page init
-c.Subscribe("events.user.*", func(data []byte) {
-    c.Sync()
-})
-
-c.Publish("events.user.login", userData)
-```
+- `via.Subscribe(c, subject, handler)` for receiving
+- `via.Publish(c, subject, data)` for sending
+- Streams declared in `Options` — NATS handles delivery, no polling

internal/examples/nats-chatroom/chat.css

@@ -0,0 +1,153 @@
+body { margin: 0; }
+
+/* Layout navbar */
+.app-nav {
+	display: flex;
+	align-items: center;
+	gap: 1rem;
+	padding: 0.5rem 1rem;
+	background: var(--pico-card-background-color);
+	border-bottom: 1px solid var(--pico-muted-border-color);
+}
+.app-nav .brand {
+	font-weight: 700;
+	text-decoration: none;
+	margin-right: auto;
+}
+.nav-links {
+	display: flex;
+	gap: 1rem;
+}
+.nav-links a {
+	text-decoration: none;
+	font-size: 0.875rem;
+}
+
+/* Chat page */
+.chat-page {
+	display: flex;
+	flex-direction: column;
+	height: calc(100vh - 53px);
+}
+nav[role="tab-control"] ul li a[aria-current="page"] {
+	background-color: var(--pico-primary-background);
+	color: var(--pico-primary-inverse);
+	border-bottom: 2px solid var(--pico-primary);
+}
+.chat-message { display: flex; gap: 0.75rem; margin-bottom: 0.5rem; }
+.avatar {
+	width: 2rem;
+	height: 2rem;
+	border-radius: 50%;
+	background: var(--pico-muted-border-color);
+	display: grid;
+	place-items: center;
+	font-size: 1.5rem;
+	flex-shrink: 0;
+}
+.avatar-lg {
+	width: 3rem;
+	height: 3rem;
+	font-size: 2rem;
+}
+.bubble { flex: 1; }
+.bubble p { margin: 0; }
+.chat-history {
+	flex: 1;
+	overflow-y: auto;
+	padding: 1rem;
+	padding-bottom: calc(88px + env(safe-area-inset-bottom));
+}
+.chat-input {
+	position: fixed;
+	left: 0;
+	right: 0;
+	bottom: 0;
+	background: var(--pico-background-color);
+	display: flex;
+	align-items: center;
+	gap: 0.75rem;
+	padding: 0.75rem 1rem calc(0.75rem + env(safe-area-inset-bottom));
+	border-top: 1px solid var(--pico-muted-border-color);
+}
+.chat-input fieldset {
+	flex: 1;
+	margin: 0;
+}
+
+/* NATS badge with status dot */
+.nats-badge {
+	background: #27AAE1;
+	color: white;
+	padding: 0.25rem 0.5rem;
+	border-radius: 4px;
+	font-size: 0.75rem;
+	margin-left: auto;
+	display: flex;
+	align-items: center;
+	gap: 0.375rem;
+}
+.status-dot {
+	width: 8px;
+	height: 8px;
+	border-radius: 50%;
+	background: #4ade80;
+	animation: pulse 2s ease-in-out infinite;
+}
+@keyframes pulse {
+	0%, 100% { opacity: 1; }
+	50% { opacity: 0.4; }
+}
+
+/* Profile page */
+.profile-page {
+	max-width: 480px;
+	margin: 0 auto;
+	padding: 2rem 1rem;
+}
+.profile-preview {
+	display: flex;
+	align-items: center;
+	gap: 0.75rem;
+	margin-bottom: 1.5rem;
+	padding: 1rem;
+	background: var(--pico-card-background-color);
+	border-radius: 8px;
+}
+.preview-name {
+	font-size: 1.125rem;
+	font-weight: 600;
+}
+.profile-form label {
+	display: block;
+	margin-bottom: 0.5rem;
+}
+.emoji-grid {
+	display: grid;
+	grid-template-columns: repeat(10, 1fr);
+	gap: 0.25rem;
+	margin-bottom: 1.5rem;
+}
+.emoji-option {
+	padding: 0.375rem;
+	font-size: 1.25rem;
+	border: 2px solid transparent;
+	border-radius: 8px;
+	background: none;
+	cursor: pointer;
+	text-align: center;
+}
+.emoji-option:hover {
+	background: var(--pico-muted-border-color);
+}
+.emoji-selected {
+	border-color: var(--pico-primary);
+	background: var(--pico-primary-focus);
+}
+.profile-actions {
+	display: flex;
+	gap: 0.75rem;
+}
+.field-error {
+	color: var(--pico-del-color);
+}

internal/examples/nats-chatroom/chat.go

@@ -0,0 +1,148 @@
+package main
+
+import (
+	"sync"
+	"time"
+
+	"github.com/ryanhamamura/via"
+	"github.com/ryanhamamura/via/h"
+)
+
+var (
+	WithSignal = via.WithSignal
+)
+
+func ChatPage(c *via.Context) {
+	currentUser := UserInfo{
+		Name:  c.Session().GetString(SessionKeyUsername),
+		Emoji: c.Session().GetString(SessionKeyEmoji),
+	}
+
+	roomSignal := c.Signal("Go")
+	statement := c.Signal("")
+
+	var messages []ChatMessage
+	var messagesMu sync.Mutex
+	currentRoom := "Go"
+
+	var currentSub via.Subscription
+
+	subscribeToRoom := func(room string) {
+		if currentSub != nil {
+			currentSub.Unsubscribe()
+		}
+
+		subject := "chat.room." + room
+
+		if hist, err := via.ReplayHistory[ChatMessage](v, subject, 50); err == nil {
+			messages = hist
+		}
+
+		sub, _ := via.Subscribe(c, subject, func(msg ChatMessage) {
+			messagesMu.Lock()
+			messages = append(messages, msg)
+			if len(messages) > 50 {
+				messages = messages[len(messages)-50:]
+			}
+			messagesMu.Unlock()
+			c.Sync()
+		})
+		currentSub = sub
+		currentRoom = room
+	}
+
+	subscribeToRoom("Go")
+
+	// Heartbeat — keeps connected indicator alive
+	connected := true
+	c.OnInterval(30*time.Second, func() {
+		connected = true
+		c.Sync()
+	})
+
+	switchRoom := c.Action(func() {
+		newRoom := roomSignal.String()
+		if newRoom != currentRoom {
+			messagesMu.Lock()
+			messages = nil
+			messagesMu.Unlock()
+			subscribeToRoom(newRoom)
+			c.Sync()
+		}
+	})
+
+	say := c.Action(func() {
+		msg := statement.String()
+		if msg == "" {
+			msg = randomDevQuote()
+		}
+		statement.SetValue("")
+
+		via.Publish(c, "chat.room."+currentRoom, ChatMessage{
+			User:    currentUser,
+			Message: msg,
+			Time:    time.Now().UnixMilli(),
+		})
+	})
+
+	c.View(func() h.H {
+		var tabs []h.H
+		for _, name := range roomNames {
+			isCurrent := name == currentRoom
+			tabs = append(tabs, h.Li(
+				h.A(
+					h.If(isCurrent, h.Attr("aria-current", "page")),
+					h.Text(name),
+					switchRoom.OnClick(WithSignal(roomSignal, name)),
+				),
+			))
+		}
+
+		messagesMu.Lock()
+		chatHistoryChildren := []h.H{
+			h.Class("chat-history"),
+			h.Script(h.Raw(`new MutationObserver(()=>scrollChatToBottom()).observe(document.querySelector('.chat-history'), {childList:true})`)),
+		}
+		for _, msg := range messages {
+			chatHistoryChildren = append(chatHistoryChildren,
+				h.Div(h.Class("chat-message"),
+					h.Div(h.Class("avatar"), h.Attr("title", msg.User.Name), h.Text(msg.User.Emoji)),
+					h.Div(h.Class("bubble"),
+						h.P(h.Text(msg.Message)),
+					),
+				),
+			)
+		}
+		messagesMu.Unlock()
+
+		_ = connected
+
+		return h.Div(h.Class("chat-page"),
+			h.Nav(
+				h.Attr("role", "tab-control"),
+				h.Ul(tabs...),
+				h.Span(h.Class("nats-badge"),
+					h.Span(h.Class("status-dot")),
+					h.Text("NATS"),
+				),
+			),
+			h.Div(chatHistoryChildren...),
+			h.Div(
+				h.Class("chat-input"),
+				h.DataIgnoreMorph(),
+				currentUser.Avatar(),
+				h.FieldSet(
+					h.Attr("role", "group"),
+					h.Input(
+						h.Type("text"),
+						h.Placeholder(currentUser.Name+" says..."),
+						statement.Bind(),
+						h.Attr("autofocus"),
+						say.OnKeyDown("Enter"),
+					),
+					h.Button(h.Text("Send"), say.OnClick()),
+				),
+			),
+		)
+	})
+}

internal/examples/nats-chatroom/main.go

@@ -1,115 +1,37 @@
 package main
 
 import (
+	_ "embed"
 	"log"
-	"math/rand"
-	"sync"
 	"time"
 
 	"github.com/ryanhamamura/via"
 	"github.com/ryanhamamura/via/h"
 )
 
-var (
-	WithSignal = via.WithSignal
-)
+//go:embed chat.css
+var chatCSS string
 
-// ChatMessage represents a message in a chat room
-type ChatMessage struct {
-	User    UserInfo `json:"user"`
-	Message string   `json:"message"`
-	Time    int64    `json:"time"`
-}
-
-// UserInfo identifies a chat participant
-type UserInfo struct {
-	Name  string `json:"name"`
-	Emoji string `json:"emoji"`
-}
-
-func (u *UserInfo) Avatar() h.H {
-	return h.Div(h.Class("avatar"), h.Attr("title", u.Name), h.Text(u.Emoji))
-}
-
-var roomNames = []string{"Go", "Rust", "Python", "JavaScript", "Clojure"}
+var v *via.V
 
 func main() {
-	v := via.New()
+	v = via.New()
 	v.Config(via.Options{
 		DevMode:       true,
 		DocumentTitle: "NATS Chat",
 		LogLevel:      via.LogLevelInfo,
 		ServerAddress: ":7331",
-	})
-
-	err := via.EnsureStream(v, via.StreamConfig{
+		Streams: []via.StreamConfig{{
 			Name:     "CHAT",
 			Subjects: []string{"chat.>"},
 			MaxMsgs:  1000,
 			MaxAge:   24 * time.Hour,
+		}},
 	})
-	if err != nil {
-		log.Fatalf("Failed to ensure stream: %v", err)
-	}
 
 	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(`
-			body { margin: 0; }
-			main {
-				display: flex;
-				flex-direction: column;
-				height: 100vh;
-			}
-			nav[role="tab-control"] ul li a[aria-current="page"] {
-				background-color: var(--pico-primary-background);
-				color: var(--pico-primary-inverse);
-				border-bottom: 2px solid var(--pico-primary);
-			}
-			.chat-message { display: flex; gap: 0.75rem; margin-bottom: 0.5rem; }
-			.avatar {
-				width: 2rem;
-				height: 2rem;
-				border-radius: 50%;
-				background: var(--pico-muted-border-color);
-				display: grid;
-				place-items: center;
-				font-size: 1.5rem;
-				flex-shrink: 0;
-			}
-			.bubble { flex: 1; }
-			.bubble p { margin: 0; }
-			.chat-history {
-				flex: 1;
-				overflow-y: auto;
-				padding: 1rem;
-				padding-bottom: calc(88px + env(safe-area-inset-bottom));
-			}
-			.chat-input {
-				position: fixed;
-				left: 0;
-				right: 0;
-				bottom: 0;
-				background: var(--pico-background-color);
-				display: flex;
-				align-items: center;
-				gap: 0.75rem;
-				padding: 0.75rem 1rem calc(0.75rem + env(safe-area-inset-bottom));
-				border-top: 1px solid var(--pico-muted-border-color);
-			}
-			.chat-input fieldset {
-				flex: 1;
-				margin: 0;
-			}
-			.nats-badge {
-				background: #27AAE1;
-				color: white;
-				padding: 0.25rem 0.5rem;
-				border-radius: 4px;
-				font-size: 0.75rem;
-				margin-left: auto;
-			}
-		`)),
+		h.StyleEl(h.Raw(chatCSS)),
 		h.Script(h.Raw(`
 			function scrollChatToBottom() {
 				const chatHistory = document.querySelector('.chat-history');
@@ -118,156 +40,38 @@ func main() {
 		`)),
 	)
 
-	v.Page("/", func(c *via.Context) {
-		currentUser := randUser()
-		roomSignal := c.Signal("Go")
-		statement := c.Signal("")
-
-		var messages []ChatMessage
-		var messagesMu sync.Mutex
-		currentRoom := "Go"
-
-		var currentSub via.Subscription
-
-		subscribeToRoom := func(room string) {
-			if currentSub != nil {
-				currentSub.Unsubscribe()
-			}
-
-			subject := "chat.room." + room
-
-			// Replay history from JetStream
-			if hist, err := via.ReplayHistory[ChatMessage](v, subject, 50); err == nil {
-				messages = hist
-			}
-
-			sub, _ := via.Subscribe(c, subject, func(msg ChatMessage) {
-				messagesMu.Lock()
-				messages = append(messages, msg)
-				if len(messages) > 50 {
-					messages = messages[len(messages)-50:]
-				}
-				messagesMu.Unlock()
-				c.Sync()
-			})
-			currentSub = sub
-			currentRoom = room
-		}
-
-		subscribeToRoom("Go")
-
-		switchRoom := c.Action(func() {
-			newRoom := roomSignal.String()
-			if newRoom != currentRoom {
-				messagesMu.Lock()
-				messages = nil
-				messagesMu.Unlock()
-				subscribeToRoom(newRoom)
-				c.Sync()
-			}
-		})
-
-		say := c.Action(func() {
-			msg := statement.String()
-			if msg == "" {
-				msg = randomDevQuote()
-			}
-			statement.SetValue("")
-
-			via.Publish(c, "chat.room."+currentRoom, ChatMessage{
-				User:    currentUser,
-				Message: msg,
-				Time:    time.Now().UnixMilli(),
-			})
-		})
-
-		c.View(func() h.H {
-			var tabs []h.H
-			for _, name := range roomNames {
-				isCurrent := name == currentRoom
-				tabs = append(tabs, h.Li(
-					h.A(
-						h.If(isCurrent, h.Attr("aria-current", "page")),
-						h.Text(name),
-						switchRoom.OnClick(WithSignal(roomSignal, name)),
-					),
-				))
-			}
-
-			messagesMu.Lock()
-			chatHistoryChildren := []h.H{
-				h.Class("chat-history"),
-				h.Script(h.Raw(`new MutationObserver(()=>scrollChatToBottom()).observe(document.querySelector('.chat-history'), {childList:true})`)),
-			}
-			for _, msg := range messages {
-				chatHistoryChildren = append(chatHistoryChildren,
-					h.Div(h.Class("chat-message"),
-						h.Div(h.Class("avatar"), h.Attr("title", msg.User.Name), h.Text(msg.User.Emoji)),
-						h.Div(h.Class("bubble"),
-							h.P(h.Text(msg.Message)),
+	v.Layout(func(content func() h.H) h.H {
+		return h.Div(
+			h.Nav(h.Class("app-nav"),
+				h.A(h.Href("/"), h.Class("brand"), h.Text("NATS Chat")),
+				h.Div(h.Class("nav-links"),
+					h.A(h.Href("/"), h.Text("Chat")),
+					h.A(h.Href("/profile"), h.Text("Profile")),
 				),
 			),
-				)
-			}
-			messagesMu.Unlock()
-
-			return h.Main(h.Class("container"),
-				h.Nav(
-					h.Attr("role", "tab-control"),
-					h.Ul(tabs...),
-					h.Span(h.Class("nats-badge"), h.Text("NATS")),
-				),
-				h.Div(chatHistoryChildren...),
-				h.Div(
-					h.Class("chat-input"),
-					currentUser.Avatar(),
-					h.FieldSet(
-						h.Attr("role", "group"),
-						h.Input(
-							h.Type("text"),
-							h.Placeholder(currentUser.Name+" says..."),
-							statement.Bind(),
-							h.Attr("autofocus"),
-							say.OnKeyDown("Enter"),
-						),
-						h.Button(h.Text("Send"), say.OnClick()),
-					),
+			h.Main(h.Class("container"),
+				h.DataViewTransition("page-content"),
+				content(),
 			),
 		)
 	})
-	})
 
-	log.Println("Starting NATS chatroom on :7331 (embedded NATS server)")
+	// Profile page — public, no auth required
+	v.Page("/profile", ProfilePage)
+
+	// Auth middleware — redirects to profile if no identity set
+	requireProfile := func(c *via.Context, next func()) {
+		if c.Session().GetString(SessionKeyUsername) == "" {
+			c.RedirectView("/profile")
+			return
+		}
+		next()
+	}
+
+	// Chat page — protected by profile middleware
+	protected := v.Group("", requireProfile)
+	protected.Page("/", ChatPage)
+
+	log.Println("Starting NATS chatroom on :7331")
 	v.Start()
 }
-
-func randUser() UserInfo {
-	adjectives := []string{"Happy", "Clever", "Brave", "Swift", "Gentle", "Wise", "Bold", "Calm", "Eager", "Fierce"}
-	animals := []string{"Panda", "Tiger", "Eagle", "Dolphin", "Fox", "Wolf", "Bear", "Hawk", "Otter", "Lion"}
-	emojis := []string{"🐼", "🐯", "🦅", "🐬", "🦊", "🐺", "🐻", "🦅", "🦦", "🦁"}
-
-	idx := rand.Intn(len(animals))
-	return UserInfo{
-		Name:  adjectives[rand.Intn(len(adjectives))] + " " + animals[idx],
-		Emoji: emojis[idx],
-	}
-}
-
-var quoteIdx = rand.Intn(len(devQuotes))
-var devQuotes = []string{
-	"Just use NATS.",
-	"Pub/sub all the things!",
-	"Messages are the new API.",
-	"JetStream for durability.",
-	"No more polling.",
-	"Event-driven architecture FTW.",
-	"Decouple everything.",
-	"NATS is fast.",
-	"Subjects are like topics.",
-	"Request-reply is cool.",
-}
-
-func randomDevQuote() string {
-	quoteIdx = (quoteIdx + 1) % len(devQuotes)
-	return devQuotes[quoteIdx]
-}

internal/examples/nats-chatroom/profile.go

@@ -0,0 +1,111 @@
+package main
+
+import (
+	"github.com/ryanhamamura/via"
+	"github.com/ryanhamamura/via/h"
+)
+
+func ProfilePage(c *via.Context) {
+	existingName := c.Session().GetString(SessionKeyUsername)
+	existingEmoji := c.Session().GetString(SessionKeyEmoji)
+	if existingEmoji == "" {
+		existingEmoji = emojiChoices[0]
+	}
+
+	nameField := c.Field(existingName,
+		via.Required("Display name is required"),
+		via.MinLen(2, "Must be at least 2 characters"),
+		via.MaxLen(20, "Must be at most 20 characters"),
+	)
+	selectedEmoji := c.Signal(existingEmoji)
+	previewName := c.Computed(func() string {
+		if name := nameField.String(); name != "" {
+			return name
+		}
+		return "Your Name"
+	})
+
+	saveToSession := func() bool {
+		if !c.ValidateAll() {
+			c.Sync()
+			return false
+		}
+		c.Session().Set(SessionKeyUsername, nameField.String())
+		c.Session().Set(SessionKeyEmoji, selectedEmoji.String())
+		return true
+	}
+
+	save := c.Action(func() {
+		saveToSession()
+	})
+
+	saveAndChat := c.Action(func() {
+		if saveToSession() {
+			c.Navigate("/", false)
+		}
+	})
+
+	c.View(func() h.H {
+		// Emoji grid
+		emojiGrid := []h.H{h.Class("emoji-grid")}
+		for _, emoji := range emojiChoices {
+			cls := "emoji-option"
+			if emoji == selectedEmoji.String() {
+				cls += " emoji-selected"
+			}
+			emojiGrid = append(emojiGrid,
+				h.Button(
+					h.Class(cls),
+					h.Type("button"),
+					h.Text(emoji),
+					save.OnClick(WithSignal(selectedEmoji, emoji)),
+				),
+			)
+		}
+
+		// Action buttons — "Start Chatting" only if editing is meaningful
+		actionButtons := []h.H{h.Class("profile-actions")}
+		if existingName != "" {
+			actionButtons = append(actionButtons,
+				h.Button(h.Text("Save"), save.OnClick(), h.Class("secondary")),
+			)
+		}
+		actionButtons = append(actionButtons,
+			h.Button(h.Text("Start Chatting"), saveAndChat.OnClick()),
+		)
+
+		return h.Div(h.Class("profile-page"),
+			h.H2(h.Text("Your Profile"), h.DataViewTransition("page-title")),
+
+			// Live preview
+			h.Div(h.Class("profile-preview"),
+				h.Div(h.Class("avatar avatar-lg"), h.Text(selectedEmoji.String())),
+				h.Span(h.Class("preview-name"), previewName.Text()),
+			),
+
+			h.Div(h.Class("profile-form"),
+				// Name field
+				h.Label(h.Text("Display Name"),
+					h.Input(
+						h.Type("text"),
+						h.Placeholder("Enter a display name"),
+						nameField.Bind(),
+						h.Attr("autofocus"),
+						saveAndChat.OnKeyDown("Enter"),
+						h.If(nameField.HasError(), h.Attr("aria-invalid", "true")),
+					),
+					h.If(nameField.HasError(),
+						h.Small(h.Class("field-error"), h.Text(nameField.FirstError())),
+					),
+				),
+
+				// Emoji picker
+				h.Label(h.Text("Choose an Avatar")),
+				h.Div(emojiGrid...),
+
+				// Actions
+				h.Div(actionButtons...),
+			),
+		)
+	})
+}

internal/examples/nats-chatroom/types.go

@@ -0,0 +1,30 @@
+package main
+
+import "github.com/ryanhamamura/via/h"
+
+const (
+	SessionKeyUsername = "username"
+	SessionKeyEmoji    = "emoji"
+)
+
+type ChatMessage struct {
+	User    UserInfo `json:"user"`
+	Message string   `json:"message"`
+	Time    int64    `json:"time"`
+}
+
+type UserInfo struct {
+	Name  string `json:"name"`
+	Emoji string `json:"emoji"`
+}
+
+func (u *UserInfo) Avatar() h.H {
+	return h.Div(h.Class("avatar"), h.Attr("title", u.Name), h.Text(u.Emoji))
+}
+
+var roomNames = []string{"Go", "Rust", "Python", "JavaScript", "Clojure"}
+
+var emojiChoices = []string{
+	"🐼", "🐯", "🦅", "🐬", "🦊", "🐺", "🐻", "🦦", "🦁", "🐸",
+	"🦄", "🐙", "🦀", "🐝", "🦋", "🐢", "🦉", "🐳", "🦈", "🐧",
+}

internal/examples/nats-chatroom/userdata.go

@@ -0,0 +1,22 @@
+package main
+
+import "math/rand"
+
+var quoteIdx = rand.Intn(len(devQuotes))
+var devQuotes = []string{
+	"Just use NATS.",
+	"Pub/sub all the things!",
+	"Messages are the new API.",
+	"JetStream for durability.",
+	"No more polling.",
+	"Event-driven architecture FTW.",
+	"Decouple everything.",
+	"NATS is fast.",
+	"Subjects are like topics.",
+	"Request-reply is cool.",
+}
+
+func randomDevQuote() string {
+	quoteIdx = (quoteIdx + 1) % len(devQuotes)
+	return devQuotes[quoteIdx]
+}

internal/examples/pathparams/main.go

@@ -4,17 +4,12 @@ import (
 	"strconv"
 
 	"github.com/ryanhamamura/via"
-	// "github.com/go-via/via-plugin-picocss/picocss"
 	. "github.com/ryanhamamura/via/h"
 )
 
 func main() {
 	v := via.New()
 
-	v.Config(via.Options{
-		// Plugins: []via.Plugin{picocss.Default},
-	})
-
 	v.Page("/counters/{counter_id}/{start_at_step}", func(c *via.Context) {
 
 		counterID := c.GetPathParam("counter_id")

internal/examples/picocss/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"github.com/ryanhamamura/via"
-	// "github.com/go-via/via-plugin-picocss/picocss"
 	"github.com/ryanhamamura/via/h"
 )
 
@@ -13,11 +12,6 @@ func main() {
 
 	v.Config(via.Options{
 		DocumentTitle: "Via Counter",
-		// Plugin is placed here. Use picocss.WithOptions(pococss.Options) to add the plugin
-		// with a different color theme or to enable a classes for a wide range of colors.
-		// Plugins: []via.Plugin{
-		// 	picocss.Default,
-		// },
 	})
 
 	v.Page("/", func(c *via.Context) {

internal/examples/pubsub-crud/main.go

@@ -53,17 +53,13 @@ func main() {
 		DocumentTitle: "Bookmarks",
 		LogLevel:      via.LogLevelInfo,
 		ServerAddress: ":7331",
-	})
-
-	err := via.EnsureStream(v, via.StreamConfig{
+		Streams: []via.StreamConfig{{
 			Name:     "BOOKMARKS",
 			Subjects: []string{"bookmarks.>"},
 			MaxMsgs:  1000,
 			MaxAge:   24 * time.Hour,
+		}},
 	})
-	if err != nil {
-		log.Fatalf("Failed to ensure stream: %v", err)
-	}
 
 	v.AppendToHead(
 		h.Link(h.Rel("stylesheet"), h.Href("https://cdn.jsdelivr.net/npm/daisyui@4/dist/full.min.css")),
@@ -76,6 +72,12 @@ func main() {
 		titleSignal := c.Signal("")
 		urlSignal := c.Signal("")
 		targetIDSignal := c.Signal("")
+		saveLabel := c.Computed(func() string {
+			if targetIDSignal.String() != "" {
+				return "Update Bookmark"
+			}
+			return "Add Bookmark"
+		})
 
 		via.Subscribe(c, "bookmarks.events", func(evt CRUDEvent) {
 			if evt.UserID == userID {
@@ -205,11 +207,6 @@ func main() {
 			}
 			bookmarksMu.RUnlock()
 
-			saveLabel := "Add Bookmark"
-			if isEditing {
-				saveLabel = "Update Bookmark"
-			}
-
 			return h.Div(h.Class("min-h-screen bg-base-200"),
 				// Navbar
 				h.Div(h.Class("navbar bg-base-100 shadow-sm"),
@@ -225,7 +222,7 @@ func main() {
 					// Form card
 					h.Div(h.Class("card bg-base-100 shadow"),
 						h.Div(h.Class("card-body"),
-							h.H2(h.Class("card-title"), h.Text(saveLabel)),
+							h.H2(h.Class("card-title"), saveLabel.Text()),
 							h.Div(h.Class("flex flex-col gap-2"),
 								h.Input(h.Class("input input-bordered w-full"), h.Type("text"), h.Placeholder("Title"), titleSignal.Bind()),
 								h.Input(h.Class("input input-bordered w-full"), h.Type("text"), h.Placeholder("https://example.com"), urlSignal.Bind()),
@@ -233,7 +230,7 @@ func main() {
 									h.If(isEditing,
 										h.Button(h.Class("btn btn-ghost"), h.Text("Cancel"), cancelEdit.OnClick()),
 									),
-									h.Button(h.Class("btn btn-primary"), h.Text(saveLabel), save.OnClick()),
+									h.Button(h.Class("btn btn-primary"), saveLabel.Text(), save.OnClick()),
 								),
 							),
 						),

internal/examples/realtimechart/main.go

@@ -6,7 +6,6 @@ import (
 	"time"
 
 	"github.com/ryanhamamura/via"
-	// "github.com/go-via/via-plugin-picocss/picocss"
 	"github.com/ryanhamamura/via/h"
 )
 
@@ -16,9 +15,6 @@ func main() {
 	v.Config(via.Options{
 		LogLevel: via.LogLevelDebug,
 		DevMode:  true,
-		Plugins: []via.Plugin{
-			// picocss.Default,
-		},
 	})
 
 	v.AppendToHead(

internal/examples/shakespeare/main.go

@@ -6,9 +6,9 @@ import (
 	"log"
 	"time"
 
+	_ "github.com/mattn/go-sqlite3"
 	"github.com/ryanhamamura/via"
 	"github.com/ryanhamamura/via/h"
-	_ "github.com/mattn/go-sqlite3"
 )
 
 type DataSource interface {
@@ -22,6 +22,9 @@ type ShakeDB struct {
 	findByTextStmt *sql.Stmt
 }
 
+// Prepare opens shake.db, a ~22 MB SQLite database of Shakespeare's works.
+// Download from https://github.com/nicholasgasior/gopher-fizzbuzz/raw/master/shake.db
+// and place it in this directory before running.
 func (shakeDB *ShakeDB) Prepare() {
 	db, err := sql.Open("sqlite3", "shake.db")
 	if err != nil {

maplibre/js.go

@@ -0,0 +1,418 @@
+package maplibre
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// guard wraps JS code so it only runs when the map instance exists.
+// The body can reference the map as `m`.
+func guard(mapID, body string) string {
+	return fmt.Sprintf(
+		`(function(){var m=window.__via_maps&&window.__via_maps[%s];if(!m)return;%s})()`,
+		jsonStr(mapID), body,
+	)
+}
+
+// jsonStr JSON-encodes a string for safe embedding in JS.
+func jsonStr(s string) string {
+	b, _ := json.Marshal(s)
+	return string(b)
+}
+
+// jsonVal JSON-encodes an arbitrary value for safe embedding in JS.
+func jsonVal(v any) string {
+	b, _ := json.Marshal(v)
+	return string(b)
+}
+
+// initScript generates the idempotent map initialization JS.
+func initScript(m *Map) string {
+	var b strings.Builder
+
+	b.WriteString(fmt.Sprintf(
+		`(function(){if(window.__via_maps&&window.__via_maps[%[1]s])return;`,
+		jsonStr(m.id),
+	))
+
+	// Build constructor options object
+	b.WriteString(fmt.Sprintf(
+		`var opts={container:%s,style:%s,center:[%s,%s],zoom:%s`,
+		jsonStr("_vmap_"+m.id),
+		jsonStr(m.opts.Style),
+		formatFloat(m.opts.Center.Lng),
+		formatFloat(m.opts.Center.Lat),
+		formatFloat(m.opts.Zoom),
+	))
+	if m.opts.Bearing != 0 {
+		b.WriteString(fmt.Sprintf(`,bearing:%s`, formatFloat(m.opts.Bearing)))
+	}
+	if m.opts.Pitch != 0 {
+		b.WriteString(fmt.Sprintf(`,pitch:%s`, formatFloat(m.opts.Pitch)))
+	}
+	if m.opts.MinZoom != 0 {
+		b.WriteString(fmt.Sprintf(`,minZoom:%s`, formatFloat(m.opts.MinZoom)))
+	}
+	if m.opts.MaxZoom != 0 {
+		b.WriteString(fmt.Sprintf(`,maxZoom:%s`, formatFloat(m.opts.MaxZoom)))
+	}
+
+	// Interaction toggles
+	writeBoolOpt := func(name string, val *bool) {
+		if val != nil {
+			if *val {
+				b.WriteString(fmt.Sprintf(`,%s:true`, name))
+			} else {
+				b.WriteString(fmt.Sprintf(`,%s:false`, name))
+			}
+		}
+	}
+	writeBoolOpt("scrollZoom", m.opts.ScrollZoom)
+	writeBoolOpt("boxZoom", m.opts.BoxZoom)
+	writeBoolOpt("dragRotate", m.opts.DragRotate)
+	writeBoolOpt("dragPan", m.opts.DragPan)
+	writeBoolOpt("keyboard", m.opts.Keyboard)
+	writeBoolOpt("doubleClickZoom", m.opts.DoubleClickZoom)
+	writeBoolOpt("touchZoomRotate", m.opts.TouchZoomRotate)
+	writeBoolOpt("touchPitch", m.opts.TouchPitch)
+	writeBoolOpt("renderWorldCopies", m.opts.RenderWorldCopies)
+
+	if m.opts.MaxBounds != nil {
+		b.WriteString(fmt.Sprintf(`,maxBounds:[[%s,%s],[%s,%s]]`,
+			formatFloat(m.opts.MaxBounds.SW.Lng), formatFloat(m.opts.MaxBounds.SW.Lat),
+			formatFloat(m.opts.MaxBounds.NE.Lng), formatFloat(m.opts.MaxBounds.NE.Lat)))
+	}
+
+	b.WriteString(`};`)
+
+	// Merge Extra options
+	if len(m.opts.Extra) > 0 {
+		extra, _ := json.Marshal(m.opts.Extra)
+		b.WriteString(fmt.Sprintf(`Object.assign(opts,%s);`, string(extra)))
+	}
+
+	b.WriteString(`var map=new maplibregl.Map(opts);`)
+	b.WriteString(`if(!window.__via_maps)window.__via_maps={};`)
+	b.WriteString(fmt.Sprintf(`window.__via_maps[%s]=map;`, jsonStr(m.id)))
+	b.WriteString(`map._via_markers={};map._via_popups={};map._via_controls={};`)
+
+	// Pre-render sources, layers, markers, popups, controls run on 'load'
+	hasLoad := len(m.sources) > 0 || len(m.layers) > 0 || len(m.markers) > 0 || len(m.popups) > 0 || len(m.controls) > 0
+	if hasLoad {
+		b.WriteString(`map.on('load',function(){`)
+		for _, src := range m.sources {
+			b.WriteString(fmt.Sprintf(`map.addSource(%s,%s);`, jsonStr(src.id), src.js))
+		}
+		for _, layer := range m.layers {
+			if layer.Before != "" {
+				b.WriteString(fmt.Sprintf(`map.addLayer(%s,%s);`, layer.toJS(), jsonStr(layer.Before)))
+			} else {
+				b.WriteString(fmt.Sprintf(`map.addLayer(%s);`, layer.toJS()))
+			}
+		}
+		for _, me := range m.markers {
+			b.WriteString(markerBodyJS(m.id, me.id, me.marker))
+		}
+		for _, pe := range m.popups {
+			b.WriteString(popupBodyJS(pe.id, pe.popup))
+		}
+		for _, ce := range m.controls {
+			b.WriteString(controlBodyJS(ce.id, ce.ctrl))
+		}
+		b.WriteString(`});`)
+	}
+
+	// Event listeners
+	for _, ev := range m.events {
+		b.WriteString(eventListenerJS(m.id, ev))
+	}
+
+	// Sync viewport signals on moveend via hidden inputs
+	b.WriteString(fmt.Sprintf(`map.on('moveend',function(){`+
+		`var c=map.getCenter();`+
+		`var el=document.getElementById(%[1]s);if(!el)return;`+
+		`var inputs=el.querySelectorAll('input[data-bind]');`+
+		`inputs.forEach(function(inp){`+
+		`var sig=inp.getAttribute('data-bind');`+
+		`if(sig===%[2]s)inp.value=c.lng;`+
+		`else if(sig===%[3]s)inp.value=c.lat;`+
+		`else if(sig===%[4]s)inp.value=map.getZoom();`+
+		`else if(sig===%[5]s)inp.value=map.getBearing();`+
+		`else if(sig===%[6]s)inp.value=map.getPitch();`+
+		`else return;`+
+		`inp.dispatchEvent(new Event('input',{bubbles:true}));`+
+		`});`+
+		`});`,
+		jsonStr("_vwrap_"+m.id),
+		jsonStr(m.CenterLng.ID()),
+		jsonStr(m.CenterLat.ID()),
+		jsonStr(m.Zoom.ID()),
+		jsonStr(m.Bearing.ID()),
+		jsonStr(m.Pitch.ID()),
+	))
+
+	// ResizeObserver for auto-resize
+	b.WriteString(fmt.Sprintf(
+		`var ro=new ResizeObserver(function(){map.resize();});`+
+			`ro.observe(document.getElementById(%s));`,
+		jsonStr("_vmap_"+m.id),
+	))
+
+	// MutationObserver to clean up on DOM removal (SPA nav)
+	b.WriteString(fmt.Sprintf(
+		`var container=document.getElementById(%[1]s);`+
+			`if(container){var mo=new MutationObserver(function(){`+
+			`if(!document.contains(container)){`+
+			`mo.disconnect();ro.disconnect();map.remove();`+
+			`delete window.__via_maps[%[2]s];`+
+			`}});`+
+			`mo.observe(document.body,{childList:true,subtree:true});}`,
+		jsonStr("_vmap_"+m.id),
+		jsonStr(m.id),
+	))
+
+	b.WriteString(`})()`)
+	return b.String()
+}
+
+// markerBodyJS generates JS to add a marker, assuming `map` is in scope.
+func markerBodyJS(mapID, markerID string, mk Marker) string {
+	var b strings.Builder
+	opts := "{"
+	if mk.Color != "" {
+		opts += fmt.Sprintf(`color:%s,`, jsonStr(mk.Color))
+	}
+	if mk.Draggable {
+		opts += `draggable:true,`
+	}
+	opts += "}"
+
+	// Determine initial position
+	if mk.LngSignal != nil && mk.LatSignal != nil {
+		b.WriteString(fmt.Sprintf(`var mk=new maplibregl.Marker(%s).setLngLat([%s,%s]);`,
+			opts, mk.LngSignal.String(), mk.LatSignal.String()))
+	} else {
+		b.WriteString(fmt.Sprintf(`var mk=new maplibregl.Marker(%s).setLngLat([%s,%s]);`,
+			opts, formatFloat(mk.LngLat.Lng), formatFloat(mk.LngLat.Lat)))
+	}
+
+	if mk.Popup != nil {
+		b.WriteString(popupConstructorJS(*mk.Popup, "pk"))
+		b.WriteString(`mk.setPopup(pk);`)
+	}
+	b.WriteString(fmt.Sprintf(`mk.addTo(map);map._via_markers[%s]=mk;`, jsonStr(markerID)))
+
+	// Dragend → signal writeback
+	if mk.Draggable && mk.LngSignal != nil && mk.LatSignal != nil {
+		b.WriteString(dragendHandlerJS(mapID, markerID, mk))
+	}
+
+	return b.String()
+}
+
+// dragendHandlerJS generates JS that writes marker position back to signal hidden inputs on dragend.
+func dragendHandlerJS(mapID, markerID string, mk Marker) string {
+	return fmt.Sprintf(
+		`mk.on('dragend',function(){`+
+			`var pos=mk.getLngLat();`+
+			`var el=document.getElementById(%[1]s);if(!el)return;`+
+			`var inputs=el.querySelectorAll('input[data-bind]');`+
+			`inputs.forEach(function(inp){`+
+			`var sig=inp.getAttribute('data-bind');`+
+			`if(sig===%[2]s){inp.value=pos.lng;inp.dispatchEvent(new Event('input',{bubbles:true}))}`+
+			`if(sig===%[3]s){inp.value=pos.lat;inp.dispatchEvent(new Event('input',{bubbles:true}))}`+
+			`});`+
+			`});`,
+		jsonStr("_vwrap_"+mapID),
+		jsonStr(mk.LngSignal.ID()),
+		jsonStr(mk.LatSignal.ID()),
+	)
+}
+
+// markerEffectExpr generates a data-effect expression that moves a signal-backed marker
+// when its signals change.
+func markerEffectExpr(mapID, markerID string, mk Marker) string {
+	// Read signals before the guard so Datastar tracks them as dependencies
+	// even when the map/marker hasn't loaded yet on first evaluation.
+	return fmt.Sprintf(
+		`var lng=$%s,lat=$%s;`+
+			`var m=window.__via_maps&&window.__via_maps[%s];`+
+			`if(m&&m._via_markers[%s]){`+
+			`m._via_markers[%s].setLngLat([lng,lat])}`,
+		mk.LngSignal.ID(), mk.LatSignal.ID(),
+		jsonStr(mapID), jsonStr(markerID), jsonStr(markerID),
+	)
+}
+
+// addMarkerJS generates a self-contained IIFE to add a marker post-render.
+func addMarkerJS(mapID, markerID string, mk Marker) string {
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf(
+		`(function(){var map=window.__via_maps&&window.__via_maps[%s];if(!map)return;`,
+		jsonStr(mapID)))
+	// Remove existing marker with same ID
+	b.WriteString(fmt.Sprintf(
+		`if(map._via_markers[%[1]s]){map._via_markers[%[1]s].remove();delete map._via_markers[%[1]s];}`,
+		jsonStr(markerID)))
+	b.WriteString(markerBodyJS(mapID, markerID, mk))
+	b.WriteString(`})()`)
+	return b.String()
+}
+
+// removeMarkerJS generates JS to remove a marker. Expects `m` in scope (used inside guard).
+func removeMarkerJS(markerID string) string {
+	return fmt.Sprintf(
+		`if(m._via_markers[%[1]s]){m._via_markers[%[1]s].remove();delete m._via_markers[%[1]s];}`,
+		jsonStr(markerID))
+}
+
+// popupBodyJS generates JS to show a popup, assuming `map` is in scope.
+func popupBodyJS(popupID string, p Popup) string {
+	var b strings.Builder
+	b.WriteString(popupConstructorJS(p, "p"))
+	b.WriteString(fmt.Sprintf(
+		`p.setLngLat([%s,%s]).addTo(map);map._via_popups[%s]=p;`,
+		formatFloat(p.LngLat.Lng), formatFloat(p.LngLat.Lat), jsonStr(popupID)))
+	return b.String()
+}
+
+// showPopupJS generates a self-contained IIFE to show a popup post-render.
+func showPopupJS(mapID, popupID string, p Popup) string {
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf(
+		`(function(){var map=window.__via_maps&&window.__via_maps[%s];if(!map)return;`,
+		jsonStr(mapID)))
+	// Close existing popup with same ID
+	b.WriteString(fmt.Sprintf(
+		`if(map._via_popups[%[1]s]){map._via_popups[%[1]s].remove();delete map._via_popups[%[1]s];}`,
+		jsonStr(popupID)))
+	b.WriteString(popupBodyJS(popupID, p))
+	b.WriteString(`})()`)
+	return b.String()
+}
+
+// closePopupJS generates JS to close a popup. Expects `m` in scope (used inside guard).
+func closePopupJS(popupID string) string {
+	return fmt.Sprintf(
+		`if(m._via_popups[%[1]s]){m._via_popups[%[1]s].remove();delete m._via_popups[%[1]s];}`,
+		jsonStr(popupID))
+}
+
+// popupConstructorJS generates JS to create a Popup object stored in varName.
+func popupConstructorJS(p Popup, varName string) string {
+	opts := "{"
+	if p.HideCloseButton {
+		opts += `closeButton:false,`
+	}
+	if p.MaxWidth != "" {
+		opts += fmt.Sprintf(`maxWidth:%s,`, jsonStr(p.MaxWidth))
+	}
+	opts += "}"
+	return fmt.Sprintf(`var %s=new maplibregl.Popup(%s).setHTML(%s);`,
+		varName, opts, jsonStr(p.Content))
+}
+
+// --- Control JS ---
+
+// controlBodyJS generates JS to add a control, assuming `map` is in scope.
+func controlBodyJS(controlID string, ctrl Control) string {
+	return fmt.Sprintf(
+		`var ctrl=%s;map.addControl(ctrl,%s);map._via_controls[%s]=ctrl;`,
+		ctrl.controlJS(), jsonStr(ctrl.controlPosition()), jsonStr(controlID))
+}
+
+// addControlJS generates a self-contained IIFE to add a control post-render.
+func addControlJS(mapID, controlID string, ctrl Control) string {
+	return fmt.Sprintf(
+		`(function(){var map=window.__via_maps&&window.__via_maps[%[1]s];if(!map)return;`+
+			`if(map._via_controls[%[2]s]){map.removeControl(map._via_controls[%[2]s]);delete map._via_controls[%[2]s];}`+
+			`var ctrl=%[3]s;map.addControl(ctrl,%[4]s);map._via_controls[%[2]s]=ctrl;`+
+			`})()`,
+		jsonStr(mapID), jsonStr(controlID), ctrl.controlJS(), jsonStr(ctrl.controlPosition()))
+}
+
+// removeControlJS generates JS to remove a control. Expects `m` in scope.
+func removeControlJS(controlID string) string {
+	return fmt.Sprintf(
+		`if(m._via_controls[%[1]s]){m.removeControl(m._via_controls[%[1]s]);delete m._via_controls[%[1]s];}`,
+		jsonStr(controlID))
+}
+
+// --- Event JS ---
+
+// eventListenerJS generates JS to register a map event listener that writes
+// event data to a hidden signal input.
+func eventListenerJS(mapID string, ev eventEntry) string {
+	var handler string
+	if ev.layerID != "" {
+		handler = fmt.Sprintf(
+			`map.on(%[1]s,%[2]s,function(e){`+
+				`var d={lngLat:{Lng:e.lngLat.lng,Lat:e.lngLat.lat},point:[e.point.x,e.point.y],layerID:%[2]s};`+
+				`if(e.features)d.features=e.features.map(function(f){return JSON.parse(JSON.stringify(f))});`+
+				`var el=document.getElementById(%[3]s);if(!el)return;`+
+				`var inp=el.querySelector('input[data-bind=%[4]s]');`+
+				`if(inp){inp.value=JSON.stringify(d);inp.dispatchEvent(new Event('input',{bubbles:true}))}`+
+				`});`,
+			jsonStr(ev.event), jsonStr(ev.layerID),
+			jsonStr("_vwrap_"+mapID), jsonStr(ev.signal.ID()),
+		)
+	} else {
+		handler = fmt.Sprintf(
+			`map.on(%[1]s,function(e){`+
+				`var d={lngLat:{Lng:e.lngLat.lng,Lat:e.lngLat.lat},point:[e.point.x,e.point.y]};`+
+				`var el=document.getElementById(%[2]s);if(!el)return;`+
+				`var inp=el.querySelector('input[data-bind=%[3]s]');`+
+				`if(inp){inp.value=JSON.stringify(d);inp.dispatchEvent(new Event('input',{bubbles:true}))}`+
+				`});`,
+			jsonStr(ev.event),
+			jsonStr("_vwrap_"+mapID), jsonStr(ev.signal.ID()),
+		)
+	}
+	return handler
+}
+
+// --- Camera options JS ---
+
+// cameraOptionsJS converts CameraOptions to a JS object literal string.
+func cameraOptionsJS(opts CameraOptions) string {
+	obj := map[string]any{}
+	if opts.Center != nil {
+		obj["center"] = []float64{opts.Center.Lng, opts.Center.Lat}
+	}
+	if opts.Zoom != nil {
+		obj["zoom"] = *opts.Zoom
+	}
+	if opts.Bearing != nil {
+		obj["bearing"] = *opts.Bearing
+	}
+	if opts.Pitch != nil {
+		obj["pitch"] = *opts.Pitch
+	}
+	if opts.Duration != nil {
+		obj["duration"] = *opts.Duration
+	}
+	if opts.Speed != nil {
+		obj["speed"] = *opts.Speed
+	}
+	if opts.Curve != nil {
+		obj["curve"] = *opts.Curve
+	}
+	if opts.Padding != nil {
+		obj["padding"] = map[string]int{
+			"top":    opts.Padding.Top,
+			"bottom": opts.Padding.Bottom,
+			"left":   opts.Padding.Left,
+			"right":  opts.Padding.Right,
+		}
+	}
+	if opts.Animate != nil {
+		obj["animate"] = *opts.Animate
+	}
+	b, _ := json.Marshal(obj)
+	return string(b)
+}
+
+func formatFloat(f float64) string {
+	return fmt.Sprintf("%g", f)
+}

maplibre/maplibre.go

@@ -0,0 +1,440 @@
+// Package maplibre provides a Go API for MapLibre GL JS maps within Via applications.
+//
+// It follows the same ExecScript + DataIgnoreMorph pattern used for other client-side
+// JS library integrations (e.g. ECharts in the realtimechart example).
+package maplibre
+
+import (
+	"crypto/rand"
+	_ "embed"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strconv"
+
+	"github.com/ryanhamamura/via"
+	"github.com/ryanhamamura/via/h"
+)
+
+//go:embed maplibre-gl.js
+var maplibreJS []byte
+
+//go:embed maplibre-gl.css
+var maplibreCSS []byte
+
+// Plugin serves the embedded MapLibre GL JS/CSS and injects them into the document head.
+func Plugin(v *via.V) {
+	v.HTTPServeMux().HandleFunc("GET /_maplibre/maplibre-gl.js", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/javascript")
+		_, _ = w.Write(maplibreJS)
+	})
+	v.HTTPServeMux().HandleFunc("GET /_maplibre/maplibre-gl.css", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/css")
+		_, _ = w.Write(maplibreCSS)
+	})
+	v.AppendToHead(
+		h.Link(h.Rel("stylesheet"), h.Href("/_maplibre/maplibre-gl.css")),
+		h.Script(h.Src("/_maplibre/maplibre-gl.js")),
+	)
+}
+
+// Map represents a MapLibre GL map instance bound to a Via context.
+type Map struct {
+	// Viewport signals — readable with .Text(), .String(), etc.
+	CenterLng *via.Signal
+	CenterLat *via.Signal
+	Zoom      *via.Signal
+	Bearing   *via.Signal
+	Pitch     *via.Signal
+
+	id   string
+	ctx  *via.Context
+	opts Options
+
+	sources  []sourceEntry
+	layers   []Layer
+	markers  []markerEntry
+	popups   []popupEntry
+	events   []eventEntry
+	controls []controlEntry
+
+	rendered bool
+}
+
+// New creates a Map bound to the given Via context with the provided options.
+// It registers viewport signals on the context for browser → server sync.
+func New(c *via.Context, opts Options) *Map {
+	if opts.Width == "" {
+		opts.Width = "100%"
+	}
+	if opts.Height == "" {
+		opts.Height = "400px"
+	}
+
+	m := &Map{
+		id:   genID(),
+		ctx:  c,
+		opts: opts,
+	}
+
+	m.CenterLng = c.Signal(opts.Center.Lng)
+	m.CenterLat = c.Signal(opts.Center.Lat)
+	m.Zoom = c.Signal(opts.Zoom)
+	m.Bearing = c.Signal(opts.Bearing)
+	m.Pitch = c.Signal(opts.Pitch)
+
+	return m
+}
+
+// Element returns the h.H DOM tree for the map. Call this once inside your View function.
+// After Element() is called, subsequent source/layer/marker/popup operations
+// use ExecScript instead of accumulating for the init script.
+//
+// Extra children are appended inside the wrapper div (useful for event inputs
+// and data-effect binding elements).
+func (m *Map) Element(extra ...h.H) h.H {
+	m.rendered = true
+
+	children := []h.H{
+		h.ID("_vwrap_" + m.id),
+		// Map container — morph-ignored so MapLibre's DOM isn't destroyed on Sync()
+		h.Div(
+			h.ID("_vmap_"+m.id),
+			h.DataIgnoreMorph(),
+			h.Attr("style", fmt.Sprintf("width:%s;height:%s", m.opts.Width, m.opts.Height)),
+		),
+		// Hidden inputs for viewport signal binding (outside morph-ignored zone)
+		h.Input(h.Type("hidden"), m.CenterLng.Bind()),
+		h.Input(h.Type("hidden"), m.CenterLat.Bind()),
+		h.Input(h.Type("hidden"), m.Zoom.Bind()),
+		h.Input(h.Type("hidden"), m.Bearing.Bind()),
+		h.Input(h.Type("hidden"), m.Pitch.Bind()),
+	}
+
+	// data-effect elements for signal-backed markers
+	for _, me := range m.markers {
+		if me.marker.LngSignal != nil && me.marker.LatSignal != nil {
+			children = append(children, h.Div(
+				h.Attr("style", "display:none"),
+				h.DataEffect(markerEffectExpr(m.id, me.id, me.marker)),
+			))
+		}
+	}
+
+	// Hidden inputs for signal-backed marker position writeback (drag → signal)
+	for _, me := range m.markers {
+		if me.marker.LngSignal != nil && me.marker.LatSignal != nil {
+			children = append(children,
+				h.Input(h.Type("hidden"), me.marker.LngSignal.Bind()),
+				h.Input(h.Type("hidden"), me.marker.LatSignal.Bind()),
+			)
+		}
+	}
+
+	children = append(children, extra...)
+
+	// Init script last
+	children = append(children, h.Script(h.Raw(initScript(m))))
+
+	return h.Div(children...)
+}
+
+// --- Viewport readers (signal → Go) ---
+
+// Center returns the current map center from synced signals.
+func (m *Map) Center() LngLat {
+	return LngLat{
+		Lng: parseFloat(m.CenterLng.String()),
+		Lat: parseFloat(m.CenterLat.String()),
+	}
+}
+
+// --- Camera methods ---
+
+// FlyTo animates the map to the target camera state.
+func (m *Map) FlyTo(opts CameraOptions) {
+	m.exec(fmt.Sprintf(`m.flyTo(%s);`, cameraOptionsJS(opts)))
+}
+
+// EaseTo eases the map to the target camera state.
+func (m *Map) EaseTo(opts CameraOptions) {
+	m.exec(fmt.Sprintf(`m.easeTo(%s);`, cameraOptionsJS(opts)))
+}
+
+// JumpTo jumps the map to the target camera state without animation.
+func (m *Map) JumpTo(opts CameraOptions) {
+	m.exec(fmt.Sprintf(`m.jumpTo(%s);`, cameraOptionsJS(opts)))
+}
+
+// FitBounds fits the map to the given bounds with optional camera options.
+func (m *Map) FitBounds(bounds LngLatBounds, opts ...CameraOptions) {
+	boundsJS := fmt.Sprintf("[[%s,%s],[%s,%s]]",
+		formatFloat(bounds.SW.Lng), formatFloat(bounds.SW.Lat),
+		formatFloat(bounds.NE.Lng), formatFloat(bounds.NE.Lat))
+	if len(opts) > 0 {
+		m.exec(fmt.Sprintf(`m.fitBounds(%s,%s);`, boundsJS, cameraOptionsJS(opts[0])))
+	} else {
+		m.exec(fmt.Sprintf(`m.fitBounds(%s);`, boundsJS))
+	}
+}
+
+// Stop aborts any in-progress camera animation.
+func (m *Map) Stop() {
+	m.exec(`m.stop();`)
+}
+
+// SetCenter sets the map center without animation.
+func (m *Map) SetCenter(ll LngLat) {
+	m.exec(fmt.Sprintf(`m.setCenter([%s,%s]);`,
+		formatFloat(ll.Lng), formatFloat(ll.Lat)))
+}
+
+// SetZoom sets the map zoom level without animation.
+func (m *Map) SetZoom(z float64) {
+	m.exec(fmt.Sprintf(`m.setZoom(%s);`, formatFloat(z)))
+}
+
+// SetBearing sets the map bearing without animation.
+func (m *Map) SetBearing(b float64) {
+	m.exec(fmt.Sprintf(`m.setBearing(%s);`, formatFloat(b)))
+}
+
+// SetPitch sets the map pitch without animation.
+func (m *Map) SetPitch(p float64) {
+	m.exec(fmt.Sprintf(`m.setPitch(%s);`, formatFloat(p)))
+}
+
+// SetStyle changes the map's style URL.
+func (m *Map) SetStyle(url string) {
+	m.exec(fmt.Sprintf(`m.setStyle(%s);`, jsonStr(url)))
+}
+
+// --- Source methods ---
+
+// AddSource adds a source to the map.
+func (m *Map) AddSource(id string, src Source) {
+	js := src.sourceJS()
+	if !m.rendered {
+		m.sources = append(m.sources, sourceEntry{id: id, js: js})
+		return
+	}
+	m.exec(fmt.Sprintf(`m.addSource(%s,%s);`, jsonStr(id), js))
+}
+
+// RemoveSource removes a source from the map.
+func (m *Map) RemoveSource(id string) {
+	if !m.rendered {
+		for i, s := range m.sources {
+			if s.id == id {
+				m.sources = append(m.sources[:i], m.sources[i+1:]...)
+				return
+			}
+		}
+		return
+	}
+	m.exec(fmt.Sprintf(`m.removeSource(%s);`, jsonStr(id)))
+}
+
+// UpdateGeoJSONSource replaces the data of an existing GeoJSON source.
+func (m *Map) UpdateGeoJSONSource(sourceID string, data any) {
+	m.exec(fmt.Sprintf(`m.getSource(%s).setData(%s);`, jsonStr(sourceID), jsonVal(data)))
+}
+
+// --- Layer methods ---
+
+// AddLayer adds a layer to the map.
+func (m *Map) AddLayer(layer Layer) {
+	if !m.rendered {
+		m.layers = append(m.layers, layer)
+		return
+	}
+	before := "undefined"
+	if layer.Before != "" {
+		before = jsonStr(layer.Before)
+	}
+	m.exec(fmt.Sprintf(`m.addLayer(%s,%s);`, layer.toJS(), before))
+}
+
+// RemoveLayer removes a layer from the map.
+func (m *Map) RemoveLayer(id string) {
+	if !m.rendered {
+		for i, l := range m.layers {
+			if l.ID == id {
+				m.layers = append(m.layers[:i], m.layers[i+1:]...)
+				return
+			}
+		}
+		return
+	}
+	m.exec(fmt.Sprintf(`m.removeLayer(%s);`, jsonStr(id)))
+}
+
+// SetPaintProperty sets a paint property on a layer.
+func (m *Map) SetPaintProperty(layerID, name string, value any) {
+	m.exec(fmt.Sprintf(`m.setPaintProperty(%s,%s,%s);`,
+		jsonStr(layerID), jsonStr(name), jsonVal(value)))
+}
+
+// SetLayoutProperty sets a layout property on a layer.
+func (m *Map) SetLayoutProperty(layerID, name string, value any) {
+	m.exec(fmt.Sprintf(`m.setLayoutProperty(%s,%s,%s);`,
+		jsonStr(layerID), jsonStr(name), jsonVal(value)))
+}
+
+// --- Marker methods ---
+
+// AddMarker adds or replaces a marker on the map.
+func (m *Map) AddMarker(id string, marker Marker) {
+	if !m.rendered {
+		m.markers = append(m.markers, markerEntry{id: id, marker: marker})
+		return
+	}
+	js := addMarkerJS(m.id, id, marker)
+	m.ctx.ExecScript(js)
+}
+
+// RemoveMarker removes a marker from the map.
+func (m *Map) RemoveMarker(id string) {
+	if !m.rendered {
+		for i, me := range m.markers {
+			if me.id == id {
+				m.markers = append(m.markers[:i], m.markers[i+1:]...)
+				return
+			}
+		}
+		return
+	}
+	m.exec(removeMarkerJS(id))
+}
+
+// --- Popup methods ---
+
+// ShowPopup shows a standalone popup on the map.
+func (m *Map) ShowPopup(id string, popup Popup) {
+	if !m.rendered {
+		m.popups = append(m.popups, popupEntry{id: id, popup: popup})
+		return
+	}
+	js := showPopupJS(m.id, id, popup)
+	m.ctx.ExecScript(js)
+}
+
+// ClosePopup closes a standalone popup on the map.
+func (m *Map) ClosePopup(id string) {
+	if !m.rendered {
+		for i, pe := range m.popups {
+			if pe.id == id {
+				m.popups = append(m.popups[:i], m.popups[i+1:]...)
+				return
+			}
+		}
+		return
+	}
+	m.exec(closePopupJS(id))
+}
+
+// --- Control methods ---
+
+// AddControl adds a control to the map.
+func (m *Map) AddControl(id string, ctrl Control) {
+	if !m.rendered {
+		m.controls = append(m.controls, controlEntry{id: id, ctrl: ctrl})
+		return
+	}
+	m.exec(addControlJS(m.id, id, ctrl))
+}
+
+// RemoveControl removes a control from the map.
+func (m *Map) RemoveControl(id string) {
+	if !m.rendered {
+		for i, ce := range m.controls {
+			if ce.id == id {
+				m.controls = append(m.controls[:i], m.controls[i+1:]...)
+				return
+			}
+		}
+		return
+	}
+	m.exec(removeControlJS(id))
+}
+
+// --- Event methods ---
+
+// OnClick returns a MapEvent that fires on map click.
+func (m *Map) OnClick() *MapEvent {
+	return m.on("click", "")
+}
+
+// OnLayerClick returns a MapEvent that fires on click of a specific layer.
+func (m *Map) OnLayerClick(layerID string) *MapEvent {
+	return m.on("click", layerID)
+}
+
+// OnMouseMove returns a MapEvent that fires on map mouse movement.
+func (m *Map) OnMouseMove() *MapEvent {
+	return m.on("mousemove", "")
+}
+
+// OnContextMenu returns a MapEvent that fires on right-click.
+func (m *Map) OnContextMenu() *MapEvent {
+	return m.on("contextmenu", "")
+}
+
+func (m *Map) on(event, layerID string) *MapEvent {
+	sig := m.ctx.Signal("")
+	ev := &MapEvent{signal: sig}
+	m.events = append(m.events, eventEntry{
+		event:   event,
+		layerID: layerID,
+		signal:  sig,
+	})
+	return ev
+}
+
+// --- Escape hatch ---
+
+// Exec runs arbitrary JS with the map available as `m`.
+func (m *Map) Exec(js string) {
+	m.exec(js)
+}
+
+// exec sends guarded JS to the browser via ExecScript.
+func (m *Map) exec(body string) {
+	m.ctx.ExecScript(guard(m.id, body))
+}
+
+// --- MapEvent ---
+
+// MapEvent wraps a signal that receives map event data as JSON.
+type MapEvent struct {
+	signal *via.Signal
+}
+
+// Bind returns the data-bind attribute for this event's signal.
+func (e *MapEvent) Bind() h.H { return e.signal.Bind() }
+
+// Data parses the event signal's JSON value into EventData.
+func (e *MapEvent) Data() EventData {
+	var d EventData
+	json.Unmarshal([]byte(e.signal.String()), &d)
+	return d
+}
+
+// Input creates a hidden input wired to this event's signal.
+// Pass action triggers (e.g. handleClick.OnInput()) as attrs.
+func (e *MapEvent) Input(attrs ...h.H) h.H {
+	all := append([]h.H{h.Type("hidden"), e.Bind()}, attrs...)
+	return h.Input(all...)
+}
+
+func parseFloat(s string) float64 {
+	f, _ := strconv.ParseFloat(s, 64)
+	return f
+}
+
+func genID() string {
+	b := make([]byte, 4)
+	rand.Read(b)
+	return hex.EncodeToString(b)
+}

maplibre/types.go

@@ -0,0 +1,359 @@
+package maplibre
+
+import (
+	"encoding/json"
+
+	"github.com/ryanhamamura/via"
+)
+
+// LngLat represents a geographic coordinate.
+type LngLat struct {
+	Lng float64
+	Lat float64
+}
+
+// LngLatBounds represents a rectangular geographic area.
+type LngLatBounds struct {
+	SW LngLat
+	NE LngLat
+}
+
+// Padding represents padding in pixels on each side of the map viewport.
+type Padding struct {
+	Top    int
+	Bottom int
+	Left   int
+	Right  int
+}
+
+// Options configures the initial map state.
+type Options struct {
+	// Style is the map style URL (required).
+	Style string
+
+	Center  LngLat
+	Zoom    float64
+	Bearing float64
+	Pitch   float64
+	MinZoom float64
+	MaxZoom float64
+
+	// CSS dimensions for the map container. Defaults: "100%", "400px".
+	Width  string
+	Height string
+
+	// Interaction toggles (nil = MapLibre default)
+	ScrollZoom        *bool
+	BoxZoom           *bool
+	DragRotate        *bool
+	DragPan           *bool
+	Keyboard          *bool
+	DoubleClickZoom   *bool
+	TouchZoomRotate   *bool
+	TouchPitch        *bool
+	RenderWorldCopies *bool
+
+	MaxBounds *LngLatBounds
+
+	// Extra is merged last into the MapLibre constructor options object,
+	// allowing pass-through of any option not covered above.
+	Extra map[string]any
+}
+
+// --- Source interface ---
+
+// Source is implemented by map data sources (GeoJSON, vector, raster, etc.).
+type Source interface {
+	sourceJS() string
+}
+
+// GeoJSONSource provides inline GeoJSON data to MapLibre.
+// Data should be a GeoJSON-marshalable value (struct, map, or json.RawMessage).
+type GeoJSONSource struct {
+	Data any
+}
+
+func (s GeoJSONSource) sourceJS() string {
+	data, _ := json.Marshal(s.Data)
+	return `{"type":"geojson","data":` + string(data) + `}`
+}
+
+// VectorSource references a vector tile source.
+type VectorSource struct {
+	URL   string
+	Tiles []string
+}
+
+func (s VectorSource) sourceJS() string {
+	obj := map[string]any{"type": "vector"}
+	if s.URL != "" {
+		obj["url"] = s.URL
+	}
+	if len(s.Tiles) > 0 {
+		obj["tiles"] = s.Tiles
+	}
+	b, _ := json.Marshal(obj)
+	return string(b)
+}
+
+// RasterSource references a raster tile source.
+type RasterSource struct {
+	URL      string
+	Tiles    []string
+	TileSize int
+}
+
+func (s RasterSource) sourceJS() string {
+	obj := map[string]any{"type": "raster"}
+	if s.URL != "" {
+		obj["url"] = s.URL
+	}
+	if len(s.Tiles) > 0 {
+		obj["tiles"] = s.Tiles
+	}
+	if s.TileSize > 0 {
+		obj["tileSize"] = s.TileSize
+	}
+	b, _ := json.Marshal(obj)
+	return string(b)
+}
+
+// RawSource is an escape hatch that passes an arbitrary JSON-marshalable
+// value directly as a MapLibre source definition.
+type RawSource struct {
+	Value any
+}
+
+func (s RawSource) sourceJS() string {
+	b, _ := json.Marshal(s.Value)
+	return string(b)
+}
+
+// --- Control interface ---
+
+// Control is implemented by map controls (navigation, scale, etc.).
+type Control interface {
+	controlJS() string
+	controlPosition() string
+}
+
+// NavigationControl adds zoom and rotation buttons.
+type NavigationControl struct {
+	Position       string // "top-right" (default), "top-left", "bottom-right", "bottom-left"
+	ShowCompass    *bool
+	ShowZoom       *bool
+	VisualizeRoll  *bool
+	VisualizePitch *bool
+}
+
+func (c NavigationControl) controlJS() string {
+	opts := map[string]any{}
+	if c.ShowCompass != nil {
+		opts["showCompass"] = *c.ShowCompass
+	}
+	if c.ShowZoom != nil {
+		opts["showZoom"] = *c.ShowZoom
+	}
+	if c.VisualizeRoll != nil {
+		opts["visualizeRoll"] = *c.VisualizeRoll
+	}
+	if c.VisualizePitch != nil {
+		opts["visualizePitch"] = *c.VisualizePitch
+	}
+	b, _ := json.Marshal(opts)
+	return "new maplibregl.NavigationControl(" + string(b) + ")"
+}
+
+func (c NavigationControl) controlPosition() string {
+	if c.Position == "" {
+		return "top-right"
+	}
+	return c.Position
+}
+
+// ScaleControl displays a scale bar.
+type ScaleControl struct {
+	Position string // default "bottom-left"
+	MaxWidth int
+	Unit     string // "metric", "imperial", "nautical"
+}
+
+func (c ScaleControl) controlJS() string {
+	opts := map[string]any{}
+	if c.MaxWidth > 0 {
+		opts["maxWidth"] = c.MaxWidth
+	}
+	if c.Unit != "" {
+		opts["unit"] = c.Unit
+	}
+	b, _ := json.Marshal(opts)
+	return "new maplibregl.ScaleControl(" + string(b) + ")"
+}
+
+func (c ScaleControl) controlPosition() string {
+	if c.Position == "" {
+		return "bottom-left"
+	}
+	return c.Position
+}
+
+// GeolocateControl adds a button to track the user's location.
+type GeolocateControl struct {
+	Position string // default "top-right"
+}
+
+func (c GeolocateControl) controlJS() string {
+	return "new maplibregl.GeolocateControl()"
+}
+
+func (c GeolocateControl) controlPosition() string {
+	if c.Position == "" {
+		return "top-right"
+	}
+	return c.Position
+}
+
+// FullscreenControl adds a fullscreen toggle button.
+type FullscreenControl struct {
+	Position string // default "top-right"
+}
+
+func (c FullscreenControl) controlJS() string {
+	return "new maplibregl.FullscreenControl()"
+}
+
+func (c FullscreenControl) controlPosition() string {
+	if c.Position == "" {
+		return "top-right"
+	}
+	return c.Position
+}
+
+// --- Camera options ---
+
+// CameraOptions configures animated camera movements (FlyTo, EaseTo, JumpTo).
+// Nil pointer fields are omitted from the JS call.
+type CameraOptions struct {
+	Center   *LngLat
+	Zoom     *float64
+	Bearing  *float64
+	Pitch    *float64
+	Duration *int     // milliseconds
+	Speed    *float64 // FlyTo only
+	Curve    *float64 // FlyTo only
+	Padding  *Padding
+	Animate  *bool
+}
+
+// --- Layer ---
+
+// Layer describes a MapLibre style layer.
+type Layer struct {
+	ID          string
+	Type        string
+	Source      string
+	SourceLayer string
+	Paint       map[string]any
+	Layout      map[string]any
+	Filter      any
+	MinZoom     float64
+	MaxZoom     float64
+
+	// Before inserts this layer before the given layer ID in the stack.
+	Before string
+}
+
+func (l Layer) toJS() string {
+	obj := map[string]any{
+		"id":   l.ID,
+		"type": l.Type,
+	}
+	if l.Source != "" {
+		obj["source"] = l.Source
+	}
+	if l.SourceLayer != "" {
+		obj["source-layer"] = l.SourceLayer
+	}
+	if l.Paint != nil {
+		obj["paint"] = l.Paint
+	}
+	if l.Layout != nil {
+		obj["layout"] = l.Layout
+	}
+	if l.Filter != nil {
+		obj["filter"] = l.Filter
+	}
+	if l.MinZoom > 0 {
+		obj["minzoom"] = l.MinZoom
+	}
+	if l.MaxZoom > 0 {
+		obj["maxzoom"] = l.MaxZoom
+	}
+	b, _ := json.Marshal(obj)
+	return string(b)
+}
+
+// --- Marker ---
+
+// Marker describes a map marker.
+type Marker struct {
+	LngLat    LngLat // static position (used when signals are nil)
+	Color     string
+	Draggable bool
+	Popup     *Popup
+
+	// Signal-backed position. When set, signals drive marker position reactively.
+	// Initial position is read from the signal values. LngLat is ignored when signals are set.
+	// If Draggable is true, drag updates write back to these signals.
+	LngSignal *via.Signal
+	LatSignal *via.Signal
+}
+
+// Popup describes a map popup.
+//
+// Content is rendered as HTML via MapLibre's setHTML. Do not pass untrusted
+// user input without sanitizing it first.
+type Popup struct {
+	Content         string // HTML content
+	LngLat          LngLat
+	HideCloseButton bool // true removes the close button (MapLibre shows it by default)
+	MaxWidth        string
+}
+
+// --- Event data ---
+
+// EventData contains data from a map event (click, mousemove, etc.).
+type EventData struct {
+	LngLat   LngLat            `json:"lngLat"`
+	Point    [2]float64        `json:"point"`
+	Features []json.RawMessage `json:"features,omitempty"`
+	LayerID  string            `json:"layerID,omitempty"`
+}
+
+// --- Internal accumulation entries ---
+
+type sourceEntry struct {
+	id string
+	js string
+}
+
+type markerEntry struct {
+	id     string
+	marker Marker
+}
+
+type popupEntry struct {
+	id    string
+	popup Popup
+}
+
+type eventEntry struct {
+	event   string
+	layerID string
+	signal  *via.Signal
+}
+
+type controlEntry struct {
+	id   string
+	ctrl Control
+}

nats.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/delaneyj/toolbelt/embeddednats"
+	natsserver "github.com/nats-io/nats-server/v2/server"
 	"github.com/nats-io/nats.go"
 )
 
@@ -50,13 +51,32 @@ func startDefaultNATS() (dn *defaultNATS, err error) {
 
 	ctx, cancel := context.WithCancel(context.Background())
 
-	ns, err := embeddednats.New(ctx, embeddednats.WithDirectory(dataDir))
+	ns, err := embeddednats.New(ctx,
+		embeddednats.WithDirectory(dataDir),
+		embeddednats.WithNATSServerOptions(&natsserver.Options{
+			JetStream: true,
+			StoreDir:  dataDir,
+			Port:      -1,
+		}),
+	)
 	if err != nil {
 		cancel()
 		os.RemoveAll(dataDir)
 		return nil, fmt.Errorf("start embedded nats: %w", err)
 	}
+	ready := make(chan struct{})
+	go func() {
 		ns.WaitForServer()
+		close(ready)
+	}()
+	select {
+	case <-ready:
+	case <-time.After(10 * time.Second):
+		ns.Close()
+		cancel()
+		os.RemoveAll(dataDir)
+		return nil, fmt.Errorf("embedded nats server did not start within 10s")
+	}
 
 	nc, err := ns.Client()
 	if err != nil {

nats_test.go

@@ -10,9 +10,24 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestPubSub_RoundTrip(t *testing.T) {
+// setupNATSTest creates a *V with an embedded NATS server.
+// Skips the test if NATS fails to start (e.g. port conflict in CI).
+func setupNATSTest(t *testing.T) *V {
+	t.Helper()
 	v := New()
-	defer v.Shutdown()
+	dn, err := getSharedNATS()
+	if err != nil {
+		v.Shutdown()
+		t.Skipf("embedded NATS unavailable: %v", err)
+	}
+	v.defaultNATS = dn
+	v.pubsub = &natsRef{dn: dn}
+	t.Cleanup(v.Shutdown)
+	return v
+}
+
+func TestPubSub_RoundTrip(t *testing.T) {
+	v := setupNATSTest(t)
 
 	var received []byte
 	done := make(chan struct{})
@@ -38,8 +53,7 @@ func TestPubSub_RoundTrip(t *testing.T) {
 }
 
 func TestPubSub_MultipleSubscribers(t *testing.T) {
-	v := New()
-	defer v.Shutdown()
+	v := setupNATSTest(t)
 
 	var mu sync.Mutex
 	var results []string
@@ -84,8 +98,7 @@ func TestPubSub_MultipleSubscribers(t *testing.T) {
 }
 
 func TestPubSub_SubscriptionCleanupOnDispose(t *testing.T) {
-	v := New()
-	defer v.Shutdown()
+	v := setupNATSTest(t)
 
 	c := newContext("cleanup-ctx", "/", v)
 	c.View(func() h.H { return h.Div() })
@@ -100,8 +113,7 @@ func TestPubSub_SubscriptionCleanupOnDispose(t *testing.T) {
 }
 
 func TestPubSub_ManualUnsubscribe(t *testing.T) {
-	v := New()
-	defer v.Shutdown()
+	v := setupNATSTest(t)
 
 	c := newContext("unsub-ctx", "/", v)
 	c.View(func() h.H { return h.Div() })
@@ -120,8 +132,7 @@ func TestPubSub_ManualUnsubscribe(t *testing.T) {
 }
 
 func TestPubSub_NoOpDuringPanicCheck(t *testing.T) {
-	v := New()
-	defer v.Shutdown()
+	v := setupNATSTest(t)
 
 	// Panic-check context has id=""
 	c := newContext("", "/", v)

navigate.js

@@ -38,15 +38,14 @@
       var url = new URL(href, window.location.origin);
       if (url.origin !== window.location.origin) return;
       e.preventDefault();
-      navigate(url.pathname + url.search);
+      navigate(url.pathname + url.search + url.hash);
     } catch(_) {}
   });
 
   var ready = false;
   window.addEventListener('popstate', function() {
-    if (!ready) { ready = true; return; }
-    navigate(window.location.pathname + window.location.search, true);
+    if (!ready) return;
+    navigate(window.location.pathname + window.location.search + window.location.hash, true);
   });
-  // Mark as ready after initial load completes
   setTimeout(function() { ready = true; }, 0);
 })();

pubsub.go

@@ -1,8 +1,9 @@
 package via
 
 // PubSub is an interface for publish/subscribe messaging backends.
-// By default, New() starts an embedded NATS server. Supply a custom
-// implementation via Config(Options{PubSub: yourBackend}) to override.
+// By default, Start() launches an embedded NATS server if no backend
+// has been configured. Supply a custom implementation via
+// Config(Options{PubSub: yourBackend}) to override.
 type PubSub interface {
 	Publish(subject string, data []byte) error
 	Subscribe(subject string, handler func(data []byte)) (Subscription, error)

pubsub_helpers_test.go

@@ -10,8 +10,7 @@ import (
 )
 
 func TestPublishSubscribe_RoundTrip(t *testing.T) {
-	v := New()
-	defer v.Shutdown()
+	v := setupNATSTest(t)
 
 	type event struct {
 		Name  string `json:"name"`
@@ -43,8 +42,7 @@ func TestPublishSubscribe_RoundTrip(t *testing.T) {
 }
 
 func TestSubscribe_SkipsBadJSON(t *testing.T) {
-	v := New()
-	defer v.Shutdown()
+	v := setupNATSTest(t)
 
 	type msg struct {
 		Text string `json:"text"`

signal.go

@@ -9,27 +9,27 @@ import (
 )
 
 // Signal represents a value that is reactive in the browser. Signals
-// are synct with the server right before an action triggers.
+// are synced with the server right before an action triggers.
 //
 // Use Bind() to connect a signal to an input and Text() to display it
 // reactively on an html element.
-type signal struct {
+type Signal struct {
 	id      string
 	val     any
 	changed bool
 	err     error
 }
 
-// ID returns the signal ID
-func (s *signal) ID() string {
+// ID returns the signal ID.
+func (s *Signal) ID() string {
 	return s.id
 }
 
 // Err returns a signal error or nil if it contains no error.
 //
 // It is useful to check for errors after updating signals with
-// dinamic values.
-func (s *signal) Err() error {
+// dynamic values.
+func (s *Signal) Err() error {
 	return s.err
 }
 
@@ -39,7 +39,7 @@ func (s *signal) Err() error {
 // Example:
 //
 //	h.Input(h.Type("number"), mysignal.Bind())
-func (s *signal) Bind() h.H {
+func (s *Signal) Bind() h.H {
 	return h.Data("bind", s.id)
 }
 
@@ -48,36 +48,35 @@ func (s *signal) Bind() h.H {
 // Example:
 //
 //	h.Div(mysignal.Text())
-func (s *signal) Text() h.H {
+func (s *Signal) Text() h.H {
 	return h.Span(h.Data("text", "$"+s.id))
 }
 
 // SetValue updates the signal’s value and marks it for synchronization with the browser.
 // The change will be propagated to the browser using *Context.Sync() or *Context.SyncSignals().
-func (s *signal) SetValue(v any) {
+func (s *Signal) SetValue(v any) {
 	s.val = v
 	s.changed = true
 	s.err = nil
 }
 
-// String return the signal value as a string.
-func (s *signal) String() string {
+// String returns the signal value as a string.
+func (s *Signal) String() string {
 	return fmt.Sprintf("%v", s.val)
 }
 
 // Bool tries to read the signal value as a bool.
 // Returns the value or false on failure.
-func (s *signal) Bool() bool {
+func (s *Signal) Bool() bool {
 	val := strings.ToLower(s.String())
 	return val == "true" || val == "1" || val == "yes" || val == "on"
 }
 
 // Int tries to read the signal value as an int.
 // Returns the value or 0 on failure.
-func (s *signal) Int() int {
+func (s *Signal) Int() int {
 	if n, err := strconv.Atoi(s.String()); err == nil {
 		return n
 	}
 	return 0
 }
-

signal_test.go

@@ -1,7 +1,6 @@
 package via
 
 import (
-	//	"net/http/httptest"
 	"testing"
 
 	"github.com/ryanhamamura/via/h"
@@ -27,7 +26,7 @@ func TestSignalReturnAsString(t *testing.T) {
 	for _, testcase := range testcases {
 		t.Run(testcase.desc, func(t *testing.T) {
 			t.Parallel()
-			var sig *signal
+			var sig *Signal
 			v := New()
 			v.Page("/", func(c *Context) {
 				sig = c.Signal(testcase.given)
@@ -57,7 +56,7 @@ func TestSignalReturnAsStringComplexTypes(t *testing.T) {
 	for _, testcase := range testcases {
 		t.Run(testcase.desc, func(t *testing.T) {
 			t.Parallel()
-			var sig *signal
+			var sig *Signal
 			v := New()
 			v.Page("/", func(c *Context) {
 				c.View(func() h.H { return nil })

via.go

@@ -58,7 +58,6 @@ type V struct {
 	datastarPath         string
 	datastarContent      []byte
 	datastarOnce         sync.Once
-	reaperStop           chan struct{}
 	middleware           []Middleware
 	layout               func(func() h.H) h.H
 }
@@ -139,8 +138,8 @@ func (v *V) Config(cfg Options) {
 		v.defaultNATS = nil
 		v.pubsub = cfg.PubSub
 	}
-	if cfg.ContextTTL != 0 {
-		v.cfg.ContextTTL = cfg.ContextTTL
+	if cfg.Streams != nil {
+		v.cfg.Streams = cfg.Streams
 	}
 	if cfg.ActionRateLimit.Rate != 0 || cfg.ActionRateLimit.Burst != 0 {
 		v.actionRateLimit = cfg.ActionRateLimit
@@ -286,53 +285,25 @@ func (v *V) getCtx(id string) (*Context, error) {
 	return nil, fmt.Errorf("ctx '%s' not found", id)
 }
 
-func (v *V) startReaper() {
-	ttl := v.cfg.ContextTTL
-	if ttl < 0 {
-		return
-	}
-	if ttl == 0 {
-		ttl = 30 * time.Second
-	}
-	interval := ttl / 3
-	if interval < 5*time.Second {
-		interval = 5 * time.Second
-	}
-	v.reaperStop = make(chan struct{})
-	go func() {
-		ticker := time.NewTicker(interval)
-		defer ticker.Stop()
-		for {
-			select {
-			case <-v.reaperStop:
-				return
-			case <-ticker.C:
-				v.reapOrphanedContexts(ttl)
-			}
-		}
-	}()
-}
-
-func (v *V) reapOrphanedContexts(ttl time.Duration) {
-	now := time.Now()
-	v.contextRegistryMutex.RLock()
-	var orphans []*Context
-	for _, c := range v.contextRegistry {
-		if !c.sseConnected.Load() && now.Sub(c.createdAt) > ttl {
-			orphans = append(orphans, c)
-		}
-	}
-	v.contextRegistryMutex.RUnlock()
-
-	for _, c := range orphans {
-		v.logInfo(c, "reaping orphaned context (no SSE connection after %s)", ttl)
-		v.cleanupCtx(c)
-	}
-}
-
 // Start starts the Via HTTP server and blocks until a SIGINT or SIGTERM
 // signal is received, then performs a graceful shutdown.
 func (v *V) Start() {
+	if v.pubsub == nil {
+		dn, err := getSharedNATS()
+		if err != nil {
+			v.logWarn(nil, "embedded NATS unavailable: %v", err)
+		} else {
+			v.defaultNATS = dn
+			v.pubsub = &natsRef{dn: dn}
+		}
+	}
+
+	for _, sc := range v.cfg.Streams {
+		if err := EnsureStream(v, sc); err != nil {
+			v.logger.Fatal().Err(err).Msgf("failed to create stream %q", sc.Name)
+		}
+	}
+
 	handler := http.Handler(v.mux)
 	if v.sessionManager != nil {
 		handler = v.sessionManager.LoadAndSave(v.mux)
@@ -342,8 +313,6 @@ func (v *V) Start() {
 		Handler: handler,
 	}
 
-	v.startReaper()
-
 	errCh := make(chan error, 1)
 	go func() {
 		errCh <- v.server.ListenAndServe()
@@ -370,9 +339,6 @@ func (v *V) Start() {
 // Shutdown gracefully shuts down the server and all contexts.
 // Safe for programmatic or test use.
 func (v *V) Shutdown() {
-	if v.reaperStop != nil {
-		close(v.reaperStop)
-	}
 	v.logInfo(nil, "draining all contexts")
 	v.drainAllContexts()
 
@@ -419,6 +385,11 @@ func (v *V) HTTPServeMux() *http.ServeMux {
 	return v.mux
 }
 
+// PubSub returns the configured PubSub backend, or nil if none is set.
+func (v *V) PubSub() PubSub {
+	return v.pubsub
+}
+
 // Static serves files from a filesystem directory at the given URL prefix.
 //
 // Example:
@@ -468,36 +439,39 @@ func (v *V) ensureDatastarHandler() {
 	})
 }
 
+func loadDevModeMap(path string) map[string]string {
+	m := make(map[string]string)
+	file, err := os.Open(path)
+	if err != nil {
+		return m
+	}
+	defer file.Close()
+	json.NewDecoder(file).Decode(&m)
+	return m
+}
+
+func saveDevModeMap(path string, m map[string]string) error {
+	file, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	return json.NewEncoder(file).Encode(m)
+}
+
 func (v *V) devModePersist(c *Context) {
 	p := filepath.Join(".via", "devmode", "ctx.json")
 	if err := os.MkdirAll(filepath.Dir(p), 0755); err != nil {
 		v.logFatal("failed to create directory for devmode files: %v", err)
 	}
 
-	// load persisted list from file, or empty list if file not found
-	file, err := os.Open(p)
-	ctxRegMap := make(map[string]string)
-	if err == nil {
-		json.NewDecoder(file).Decode(&ctxRegMap)
-	}
-	file.Close()
-
-	// add ctx to persisted list
+	ctxRegMap := loadDevModeMap(p)
 	if _, ok := ctxRegMap[c.id]; !ok {
 		ctxRegMap[c.id] = c.route
 	}
 
-	// write persisted list to file
-	file, err = os.Create(p)
-	if err != nil {
-		v.logErr(c, "devmode failed to percist ctx: %v", err)
-
-	}
-	defer file.Close()
-
-	encoder := json.NewEncoder(file)
-	if err := encoder.Encode(ctxRegMap); err != nil {
-		v.logErr(c, "devmode failed to persist ctx")
+	if err := saveDevModeMap(p, ctxRegMap); err != nil {
+		v.logErr(c, "devmode failed to persist ctx: %v", err)
 	}
 	v.logDebug(c, "devmode persisted ctx to file")
 }
@@ -505,27 +479,11 @@ func (v *V) devModePersist(c *Context) {
 func (v *V) devModeRemovePersisted(c *Context) {
 	p := filepath.Join(".via", "devmode", "ctx.json")
 
-	// load persisted list from file, or empty list if file not found
-	file, err := os.Open(p)
-	ctxRegMap := make(map[string]string)
-	if err == nil {
-		json.NewDecoder(file).Decode(&ctxRegMap)
-	}
-	file.Close()
-
+	ctxRegMap := loadDevModeMap(p)
 	delete(ctxRegMap, c.id)
 
-	// write persisted list to file
-	file, err = os.Create(p)
-	if err != nil {
-		v.logErr(c, "devmode failed to remove percisted ctx: %v", err)
-
-	}
-	defer file.Close()
-
-	encoder := json.NewEncoder(file)
-	if err := encoder.Encode(ctxRegMap); err != nil {
-		v.logErr(c, "devmode failed to remove persisted ctx")
+	if err := saveDevModeMap(p, ctxRegMap); err != nil {
+		v.logErr(c, "devmode failed to remove persisted ctx: %v", err)
 	}
 	v.logDebug(c, "devmode removed persisted ctx from file")
 }
@@ -609,7 +567,9 @@ func New() *V {
 		}
 		c, err := v.getCtx(cID)
 		if err != nil {
-			v.logErr(nil, "sse stream failed to start: %v", err)
+			v.logInfo(nil, "context expired, reloading client: %s", cID)
+			sse := datastar.NewSSE(w, r)
+			sse.ExecuteScript("window.location.reload()")
 			return
 		}
 		c.reqCtx = r.Context()
@@ -619,20 +579,39 @@ func New() *V {
 		// use last-event-id to tell if request is a sse reconnect
 		sse.Send(datastar.EventTypePatchElements, []string{}, datastar.WithSSEEventId("via"))
 
+		// Drain stale patches on reconnect so the client gets fresh state
+		if c.sseDisconnectedAt.Load() != nil {
+			for {
+				select {
+				case <-c.patchChan:
+				default:
+					goto drained
+				}
+			}
+		drained:
+		}
 		c.sseConnected.Store(true)
+		c.sseDisconnectedAt.Store(nil)
 		v.logDebug(c, "SSE connection established")
 
 		go c.Sync()
 
+		keepalive := time.NewTicker(30 * time.Second)
+		defer keepalive.Stop()
+
 		for {
 			select {
 			case <-sse.Context().Done():
 				v.logDebug(c, "SSE connection ended")
-				v.cleanupCtx(c)
+				c.sseConnected.Store(false)
+				dcNow := time.Now()
+				c.sseDisconnectedAt.Store(&dcNow)
 				return
 			case <-c.ctxDisposedChan:
 				v.logDebug(c, "context disposed, closing SSE")
 				return
+			case <-keepalive.C:
+				sse.PatchSignals([]byte("{}"))
 			case patch := <-c.patchChan:
 				switch patch.typ {
 				case patchTypeElements:
@@ -777,14 +756,6 @@ func New() *V {
 		v.cleanupCtx(c)
 	})
 
-	dn, err := getSharedNATS()
-	if err != nil {
-		v.logWarn(nil, "embedded NATS unavailable: %v", err)
-	} else {
-		v.defaultNATS = dn
-		v.pubsub = &natsRef{dn: dn}
-	}
-
 	return v
 }
 

via_test.go

@@ -90,7 +90,7 @@ func TestCustomDatastarPath(t *testing.T) {
 }
 
 func TestSignal(t *testing.T) {
-	var sig *signal
+	var sig *Signal
 	v := New()
 	v.Page("/", func(c *Context) {
 		sig = c.Signal("test")
@@ -106,7 +106,7 @@ func TestSignal(t *testing.T) {
 
 func TestAction(t *testing.T) {
 	var trigger *actionTrigger
-	var sig *signal
+	var sig *Signal
 	v := New()
 	v.Page("/", func(c *Context) {
 		trigger = c.Action(func() {})
@@ -127,7 +127,7 @@ func TestAction(t *testing.T) {
 	v.mux.ServeHTTP(w, req)
 	body := w.Body.String()
 	assert.Contains(t, body, "data-on:click")
-	assert.Contains(t, body, "data-on:change__debounce.200ms")
+	assert.Contains(t, body, "data-on:change")
 	assert.Contains(t, body, "data-on:keydown")
 	assert.Contains(t, body, "/_action/")
 }
@@ -167,7 +167,7 @@ func TestEventTypes(t *testing.T) {
 
 	t.Run("WithSignal", func(t *testing.T) {
 		var trigger *actionTrigger
-		var sig *signal
+		var sig *Signal
 		v := New()
 		v.Page("/", func(c *Context) {
 			trigger = c.Action(func() {})
@@ -207,7 +207,7 @@ func TestOnKeyDownWithWindow(t *testing.T) {
 func TestOnKeyDownMap(t *testing.T) {
 	t.Run("multiple bindings with different actions", func(t *testing.T) {
 		var move, shoot *actionTrigger
-		var dir *signal
+		var dir *Signal
 		v := New()
 		v.Page("/", func(c *Context) {
 			dir = c.Signal("none")
@@ -251,7 +251,7 @@ func TestOnKeyDownMap(t *testing.T) {
 
 	t.Run("WithSignal per binding", func(t *testing.T) {
 		var move *actionTrigger
-		var dir *signal
+		var dir *Signal
 		v := New()
 		v.Page("/", func(c *Context) {
 			dir = c.Signal("none")
@@ -281,6 +281,112 @@ func TestOnKeyDownMap(t *testing.T) {
 	})
 }
 
+func TestFormatDuration(t *testing.T) {
+	tests := []struct {
+		d    time.Duration
+		want string
+	}{
+		{200 * time.Millisecond, "200ms"},
+		{1 * time.Second, "1000ms"},
+		{50 * time.Millisecond, "50ms"},
+	}
+	for _, tt := range tests {
+		assert.Equal(t, tt.want, formatDuration(tt.d))
+	}
+}
+
+func TestBuildAttrKey(t *testing.T) {
+	tests := []struct {
+		name  string
+		event string
+		opts  triggerOpts
+		want  string
+	}{
+		{"bare event", "click", triggerOpts{}, "on:click"},
+		{"debounce only", "change", triggerOpts{debounce: 200 * time.Millisecond}, "on:change__debounce.200ms"},
+		{"throttle only", "scroll", triggerOpts{throttle: 100 * time.Millisecond}, "on:scroll__throttle.100ms"},
+		{"window only", "keydown", triggerOpts{window: true}, "on:keydown__window"},
+		{"debounce + window", "input", triggerOpts{debounce: 300 * time.Millisecond, window: true}, "on:input__debounce.300ms__window"},
+		{"throttle + window", "scroll", triggerOpts{throttle: 500 * time.Millisecond, window: true}, "on:scroll__throttle.500ms__window"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, buildAttrKey(tt.event, &tt.opts))
+		})
+	}
+}
+
+func TestWithDebounce(t *testing.T) {
+	var trigger *actionTrigger
+	v := New()
+	v.Page("/", func(c *Context) {
+		trigger = c.Action(func() {})
+		c.View(func() h.H {
+			return h.Button(trigger.OnClick(WithDebounce(300 * time.Millisecond)))
+		})
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	v.mux.ServeHTTP(w, req)
+	body := w.Body.String()
+	assert.Contains(t, body, "data-on:click__debounce.300ms")
+	assert.Contains(t, body, "/_action/"+trigger.id)
+}
+
+func TestWithThrottle(t *testing.T) {
+	var trigger *actionTrigger
+	v := New()
+	v.Page("/", func(c *Context) {
+		trigger = c.Action(func() {})
+		c.View(func() h.H {
+			return h.Div(trigger.OnScroll(WithThrottle(100 * time.Millisecond)))
+		})
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	v.mux.ServeHTTP(w, req)
+	body := w.Body.String()
+	assert.Contains(t, body, "data-on:scroll__throttle.100ms")
+	assert.Contains(t, body, "/_action/"+trigger.id)
+}
+
+func TestWithDebounceOnChange(t *testing.T) {
+	var trigger *actionTrigger
+	v := New()
+	v.Page("/", func(c *Context) {
+		trigger = c.Action(func() {})
+		c.View(func() h.H {
+			return h.Input(trigger.OnChange(WithDebounce(200 * time.Millisecond)))
+		})
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	v.mux.ServeHTTP(w, req)
+	body := w.Body.String()
+	assert.Contains(t, body, "data-on:change__debounce.200ms")
+	assert.Contains(t, body, "/_action/"+trigger.id)
+}
+
+func TestDebounceWithWindow(t *testing.T) {
+	var trigger *actionTrigger
+	v := New()
+	v.Page("/", func(c *Context) {
+		trigger = c.Action(func() {})
+		c.View(func() h.H {
+			return h.Div(trigger.OnKeyDown("Enter", WithDebounce(150*time.Millisecond), WithWindow()))
+		})
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	w := httptest.NewRecorder()
+	v.mux.ServeHTTP(w, req)
+	body := w.Body.String()
+	assert.Contains(t, body, "data-on:keydown__debounce.150ms__window")
+}
+
 func TestConfig(t *testing.T) {
 	v := New()
 	v.Config(Options{DocumentTitle: "Test"})
@@ -294,41 +400,6 @@ func TestPage_PanicsOnNoView(t *testing.T) {
 	})
 }
 
-func TestReaperCleansOrphanedContexts(t *testing.T) {
-	v := New()
-	c := newContext("orphan-1", "/", v)
-	c.createdAt = time.Now().Add(-time.Minute) // created 1 min ago
-	v.registerCtx(c)
-
-	_, err := v.getCtx("orphan-1")
-	assert.NoError(t, err)
-
-	v.reapOrphanedContexts(10 * time.Second)
-
-	_, err = v.getCtx("orphan-1")
-	assert.Error(t, err, "orphaned context should have been reaped")
-}
-
-func TestReaperIgnoresConnectedContexts(t *testing.T) {
-	v := New()
-	c := newContext("connected-1", "/", v)
-	c.createdAt = time.Now().Add(-time.Minute)
-	c.sseConnected.Store(true)
-	v.registerCtx(c)
-
-	v.reapOrphanedContexts(10 * time.Second)
-
-	_, err := v.getCtx("connected-1")
-	assert.NoError(t, err, "connected context should survive reaping")
-}
-
-func TestReaperDisabledWithNegativeTTL(t *testing.T) {
-	v := New()
-	v.cfg.ContextTTL = -1
-	v.startReaper()
-	assert.Nil(t, v.reaperStop, "reaper should not start with negative TTL")
-}
-
 func TestCleanupCtxIdempotent(t *testing.T) {
 	v := New()
 	c := newContext("idempotent-1", "/", v)