diff --git a/internal/hooks/builtin/_placeholder.js b/internal/hooks/builtin/_placeholder.js
deleted file mode 100644
index bf490386..00000000
--- a/internal/hooks/builtin/_placeholder.js
+++ /dev/null
@@ -1,2 +0,0 @@
-// Placeholder to satisfy `//go:embed *.js` until the first real builtin
-// ships. Phase 05 adds pii-redactor.js and this file is removed.
diff --git a/internal/hooks/builtin/builtins.yaml b/internal/hooks/builtin/builtins.yaml
index bf1a13aa..7128a6d9 100644
--- a/internal/hooks/builtin/builtins.yaml
+++ b/internal/hooks/builtin/builtins.yaml
@@ -25,4 +25,24 @@
 # Phase 04 ships this registry empty. Phase 05 adds the first exemplar
 # (pii-redactor). When adding a builtin, also add the .js file + remove
 # the _placeholder.js once at least one real source_file exists.
-builtins: []
+builtins:
+  - id: pii-redactor
+    version: 1
+    events: [user_prompt_submit, pre_tool_use]
+    scope: global
+    matcher: ""
+    if_expr: ""
+    timeout_ms: 2000
+    # Fail-open on timeout: missing one redaction is less harmful than
+    # blocking the whole conversation. Operators who want strict behavior
+    # can toggle the row to matcher/disabled via config.
+    on_timeout: allow
+    # High priority so the redactor runs BEFORE other hooks see raw input.
+    priority: 900
+    mutable_fields:
+      - rawInput
+      - toolInput.command
+      - toolInput.query
+      - toolInput.content
+    source_file: pii-redactor.js
+    description: "Masks email addresses and E.164-ish phone numbers in user input and common tool-input fields."
diff --git a/internal/hooks/builtin/loader.go b/internal/hooks/builtin/loader.go
index c689fd98..f7ee6382 100644
--- a/internal/hooks/builtin/loader.go
+++ b/internal/hooks/builtin/loader.go
@@ -128,3 +128,11 @@ func source(file string) ([]byte, bool) {
 	b, ok := sourceCache[file]
 	return b, ok
 }
+
+// Source returns the raw bytes of an embedded builtin source file without
+// going through Load()/the in-memory cache. Primarily for handler tests that
+// want to exercise the real embedded JS in isolation. Returns the usual
+// fs.ErrNotExist when the file is missing.
+func Source(name string) ([]byte, error) {
+	return fs.ReadFile(name)
+}
diff --git a/internal/hooks/builtin/loader_test.go b/internal/hooks/builtin/loader_test.go
index 6f191976..d422ad90 100644
--- a/internal/hooks/builtin/loader_test.go
+++ b/internal/hooks/builtin/loader_test.go
@@ -6,15 +6,42 @@ import (
 	"github.com/google/uuid"
 )
 
-// TestLoad_EmptyYaml ensures the Phase 04 ship state (empty builtins list +
-// _placeholder.js) loads without error and leaves the registry empty.
-func TestLoad_EmptyYaml(t *testing.T) {
+// TestLoad_ShippedRegistry verifies the baked-in builtins parse clean at
+// build time. Phase 05 ships pii-redactor (2 events), so we assert the
+// registry contains at least that spec and that its embedded source file
+// loaded successfully.
+func TestLoad_ShippedRegistry(t *testing.T) {
 	if err := Load(); err != nil {
 		t.Fatalf("Load: %v", err)
 	}
-	if got := RegisteredSpecs(); len(got) != 0 {
-		t.Errorf("registered=%d, want 0 (empty builtins.yaml)", len(got))
+	specs := RegisteredSpecs()
+	var pii *Spec
+	for i := range specs {
+		if specs[i].ID == "pii-redactor" {
+			pii = &specs[i]
+			break
+		}
 	}
+	if pii == nil {
+		t.Fatalf("pii-redactor not in registry; have %v", specIDs(specs))
+	}
+	if pii.SourceFile != "pii-redactor.js" {
+		t.Errorf("pii-redactor source_file=%q, want pii-redactor.js", pii.SourceFile)
+	}
+	if len(pii.Events) != 2 {
+		t.Errorf("pii-redactor events=%v, want 2", pii.Events)
+	}
+	if src, ok := source("pii-redactor.js"); !ok || len(src) == 0 {
+		t.Error("pii-redactor.js bytes not cached after Load")
+	}
+}
+
+func specIDs(ss []Spec) []string {
+	out := make([]string, 0, len(ss))
+	for _, s := range ss {
+		out = append(out, s.ID)
+	}
+	return out
 }
 
 // TestBuiltinNamespace_Stable guards against a silent namespace change that
diff --git a/internal/hooks/builtin/pii-redactor.js b/internal/hooks/builtin/pii-redactor.js
new file mode 100644
index 00000000..d88ea642
--- /dev/null
+++ b/internal/hooks/builtin/pii-redactor.js
@@ -0,0 +1,56 @@
+// Builtin: PII redactor (email + phone)
+// Version: 1 — matches builtins.yaml
+// Runs on: user_prompt_submit, pre_tool_use
+// Mutates: rawInput, toolInput.command, toolInput.query, toolInput.content
+//
+// ES5.1 only — goja runtime. No let/const, no arrow functions, no template literals.
+
+var EMAIL_RE = /[A-Za-z0-9._%+\-]+@[A-Za-z0-9.\-]+\.[A-Za-z]{2,}/g;
+// E.164-ish: optional +, leading 1-9, 7-14 more digits; guarded so embedded
+// digits inside long tokens (ids, paths, filenames) are left alone.
+var PHONE_RE = /(^|[^0-9+])(\+?[1-9][0-9]{7,14})(?=[^0-9]|$)/g;
+
+function redact(s) {
+    if (typeof s !== "string" || s.length === 0) return s;
+    var out = s.replace(EMAIL_RE, "[REDACTED_EMAIL]");
+    out = out.replace(PHONE_RE, function (_m, lead) {
+        return lead + "[REDACTED_PHONE]";
+    });
+    return out;
+}
+
+function handle(event) {
+    var changed = false;
+    var updated = { toolInput: {} };
+
+    if (typeof event.rawInput === "string") {
+        var r = redact(event.rawInput);
+        if (r !== event.rawInput) {
+            updated.rawInput = r;
+            changed = true;
+        }
+    }
+
+    var fields = ["command", "query", "content"];
+    var ti = event.toolInput || {};
+    for (var i = 0; i < fields.length; i++) {
+        var k = fields[i];
+        var v = ti[k];
+        if (typeof v === "string") {
+            var rv = redact(v);
+            if (rv !== v) {
+                updated.toolInput[k] = rv;
+                changed = true;
+            }
+        }
+    }
+
+    if (!changed) {
+        return { decision: "allow" };
+    }
+    var tiKeys = Object.keys(updated.toolInput);
+    if (tiKeys.length === 0) {
+        delete updated.toolInput;
+    }
+    return { decision: "allow", updatedInput: updated };
+}
diff --git a/internal/hooks/dispatcher_test.go b/internal/hooks/dispatcher_test.go
index 10b4914f..7c7f673a 100644
--- a/internal/hooks/dispatcher_test.go
+++ b/internal/hooks/dispatcher_test.go
@@ -478,3 +478,148 @@ func TestDispatcher_ScriptMutation_UISourceDenied(t *testing.T) {
 		t.Fatalf("non-builtin mutation leaked: UpdatedRawInput=%v", *r.UpdatedRawInput)
 	}
 }
+
+// ── Phase 05: dotted-path allowlist walker (exercises Phase-03 walker)  ──────
+//
+// Phase 05 ships the pii-redactor whose mutable_fields are
+// [rawInput, toolInput.command, toolInput.query, toolInput.content].
+// These tests drive the dispatcher's applyBuiltinMutation via a mutating
+// handler + a custom lookup to prove the dotted-path and wildcard semantics
+// continue to hold with that specific allowlist. No actual JS runs here.
+
+func TestDispatcher_Walker_DottedPathOnlyAllowedKeys(t *testing.T) {
+	prev := installAllowlist(t, map[string][]string{
+		"pii": {"toolInput.command"},
+	})
+	defer prev()
+
+	cfg := newBaseHook(hooks.HandlerScript, hooks.EventPreToolUse)
+	cfg.Source = hooks.SourceBuiltin
+	cfg.ID = allowlistID("pii")
+	fs := &fakeStore{hooks: []hooks.HookConfig{cfg}}
+
+	// Handler "tries" to mutate both command (allowed) AND path (not allowed).
+	// The dispatcher must apply only the allowed key; path stays at its original
+	// event value — NOT the handler's forged override.
+	h := &mutatingHandler{updated: map[string]any{
+		"toolInput": map[string]any{
+			"command": "REDACTED",
+			"path":    "EVIL_OVERRIDE",
+		},
+	}}
+	d := hooks.NewStdDispatcher(hooks.StdDispatcherOpts{
+		Store:    fs,
+		Audit:    hooks.NewAuditWriter(fs, ""),
+		Handlers: map[hooks.HandlerType]hooks.Handler{hooks.HandlerScript: h},
+	})
+
+	r, err := d.Fire(context.Background(), hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventPreToolUse,
+		ToolInput: map[string]any{"path": "/safe/path", "command": "old"},
+	})
+	if err != nil {
+		t.Fatalf("Fire: %v", err)
+	}
+	if r.UpdatedToolInput == nil {
+		t.Fatal("walker dropped allowed key")
+	}
+	if got, _ := r.UpdatedToolInput["command"].(string); got != "REDACTED" {
+		t.Errorf("command=%q, want REDACTED", got)
+	}
+	if got, _ := r.UpdatedToolInput["path"].(string); got != "/safe/path" {
+		t.Errorf("disallowed key slipped through: path=%q, want /safe/path", got)
+	}
+}
+
+func TestDispatcher_Walker_RawInputOnly_IgnoresToolInput(t *testing.T) {
+	prev := installAllowlist(t, map[string][]string{"raw": {"rawInput"}})
+	defer prev()
+
+	cfg := newBaseHook(hooks.HandlerScript, hooks.EventUserPromptSubmit)
+	cfg.Source = hooks.SourceBuiltin
+	cfg.ID = allowlistID("raw")
+	fs := &fakeStore{hooks: []hooks.HookConfig{cfg}}
+
+	h := &mutatingHandler{updated: map[string]any{
+		"rawInput":  "redacted",
+		"toolInput": map[string]any{"command": "should-be-stripped"},
+	}}
+	d := hooks.NewStdDispatcher(hooks.StdDispatcherOpts{
+		Store:    fs,
+		Audit:    hooks.NewAuditWriter(fs, ""),
+		Handlers: map[hooks.HandlerType]hooks.Handler{hooks.HandlerScript: h},
+	})
+
+	r, err := d.Fire(context.Background(), hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  "original",
+		ToolInput: map[string]any{"command": "orig"},
+	})
+	if err != nil {
+		t.Fatalf("Fire: %v", err)
+	}
+	if r.UpdatedRawInput == nil || *r.UpdatedRawInput != "redacted" {
+		t.Fatalf("UpdatedRawInput=%v, want 'redacted'", r.UpdatedRawInput)
+	}
+	// UpdatedToolInput may be non-nil (dispatcher returns the evMut toolInput
+	// once any mutation happens), but each key must still equal its original
+	// event value — the handler's forged "should-be-stripped" must NOT appear.
+	if r.UpdatedToolInput != nil {
+		if got, _ := r.UpdatedToolInput["command"].(string); got != "orig" {
+			t.Errorf("toolInput.command leaked handler forge: got %q, want orig", got)
+		}
+	}
+}
+
+func TestDispatcher_Walker_ToolInputWildcard_MergesAll(t *testing.T) {
+	prev := installAllowlist(t, map[string][]string{"wild": {"toolInput"}})
+	defer prev()
+
+	cfg := newBaseHook(hooks.HandlerScript, hooks.EventPreToolUse)
+	cfg.Source = hooks.SourceBuiltin
+	cfg.ID = allowlistID("wild")
+	fs := &fakeStore{hooks: []hooks.HookConfig{cfg}}
+
+	h := &mutatingHandler{updated: map[string]any{
+		"toolInput": map[string]any{"a": 1, "b": 2, "c": 3},
+	}}
+	d := hooks.NewStdDispatcher(hooks.StdDispatcherOpts{
+		Store:    fs,
+		Audit:    hooks.NewAuditWriter(fs, ""),
+		Handlers: map[hooks.HandlerType]hooks.Handler{hooks.HandlerScript: h},
+	})
+
+	r, err := d.Fire(context.Background(), hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventPreToolUse,
+		ToolInput: map[string]any{},
+	})
+	if err != nil {
+		t.Fatalf("Fire: %v", err)
+	}
+	for _, k := range []string{"a", "b", "c"} {
+		if _, ok := r.UpdatedToolInput[k]; !ok {
+			t.Errorf("wildcard merge dropped key %q", k)
+		}
+	}
+}
+
+// installAllowlist swaps the dispatcher's per-id lookup for the duration of
+// a test. Keys in the map are resolved via allowlistID(name). Returns the
+// restore func; callers defer it.
+func installAllowlist(t *testing.T, m map[string][]string) func() {
+	t.Helper()
+	ids := map[uuid.UUID][]string{}
+	for name, fields := range m {
+		ids[allowlistID(name)] = fields
+	}
+	hooks.SetBuiltinAllowlistLookup(func(id uuid.UUID) []string { return ids[id] })
+	return func() { hooks.SetBuiltinAllowlistLookup(nil) }
+}
+
+func allowlistID(name string) uuid.UUID {
+	// Stable deterministic UUID per label so cfg.ID matches the lookup.
+	return uuid.NewSHA1(uuid.NameSpaceDNS, []byte("test.allowlist/"+name))
+}
diff --git a/internal/hooks/handlers/script_pii_redactor_test.go b/internal/hooks/handlers/script_pii_redactor_test.go
new file mode 100644
index 00000000..ba2d45f3
--- /dev/null
+++ b/internal/hooks/handlers/script_pii_redactor_test.go
@@ -0,0 +1,182 @@
+package handlers
+
+import (
+	"context"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+
+	"github.com/nextlevelbuilder/goclaw/internal/hooks"
+	"github.com/nextlevelbuilder/goclaw/internal/hooks/builtin"
+)
+
+// End-to-end tests for the Phase-05 pii-redactor builtin. These run the REAL
+// embedded JS through the REAL ScriptHandler (no stubs) so we catch any ES5.1
+// / goja regex compatibility issue at CI time.
+
+func piiHook(t *testing.T, event hooks.HookEvent) hooks.HookConfig {
+	t.Helper()
+	src, err := builtin.Source("pii-redactor.js")
+	if err != nil {
+		t.Fatalf("load pii-redactor.js: %v", err)
+	}
+	return hooks.HookConfig{
+		ID:          builtin.BuiltinEventID("pii-redactor", string(event)),
+		TenantID:    hooks.SentinelTenantID,
+		Event:       event,
+		HandlerType: hooks.HandlerScript,
+		Scope:       hooks.ScopeGlobal,
+		Source:      hooks.SourceBuiltin,
+		Config:      map[string]any{"source": string(src)},
+		Metadata:    map[string]any{"builtin": true, "version": 1},
+		TimeoutMS:   2000,
+		OnTimeout:   hooks.DecisionAllow,
+		Priority:    900,
+		Enabled:     true,
+		Version:     1,
+	}
+}
+
+func runPII(t *testing.T, ev hooks.Event) *hooks.ScriptResult {
+	t.Helper()
+	h := newTestHandler()
+	res := &hooks.ScriptResult{}
+	ctx, cancel := context.WithTimeout(hooks.WithScriptResult(context.Background(), res), 500*time.Millisecond)
+	defer cancel()
+	dec, err := h.Execute(ctx, piiHook(t, ev.HookEvent), ev)
+	if err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+	if dec != hooks.DecisionAllow {
+		t.Fatalf("decision=%v, want allow", dec)
+	}
+	return res
+}
+
+func TestPIIRedactor_RawInputEmail(t *testing.T) {
+	ev := hooks.Event{
+		EventID:   "e",
+		TenantID:  uuid.New(),
+		AgentID:   uuid.New(),
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  "email me at user@example.com please",
+	}
+	res := runPII(t, ev)
+	got, _ := res.UpdatedInput["rawInput"].(string)
+	if got != "email me at [REDACTED_EMAIL] please" {
+		t.Fatalf("rawInput: got %q", got)
+	}
+}
+
+func TestPIIRedactor_RawInputPhone(t *testing.T) {
+	ev := hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  "call me at +14155551212 tonight",
+	}
+	res := runPII(t, ev)
+	got, _ := res.UpdatedInput["rawInput"].(string)
+	if !strings.Contains(got, "[REDACTED_PHONE]") || strings.Contains(got, "+14155551212") {
+		t.Fatalf("rawInput: got %q; want phone masked", got)
+	}
+}
+
+// toolInput.command is in mutable_fields → gets redacted.
+func TestPIIRedactor_ToolInputCommandRedacted(t *testing.T) {
+	ev := hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventPreToolUse,
+		ToolName:  "shell",
+		ToolInput: map[string]any{
+			"command": "curl -d 'to=alice@co.com' https://svc",
+			"path":    "/etc/passwd",
+		},
+	}
+	res := runPII(t, ev)
+	ti, _ := res.UpdatedInput["toolInput"].(map[string]any)
+	if ti == nil {
+		t.Fatal("toolInput missing in updatedInput")
+	}
+	cmd, _ := ti["command"].(string)
+	if !strings.Contains(cmd, "[REDACTED_EMAIL]") || strings.Contains(cmd, "alice@co.com") {
+		t.Fatalf("command: got %q", cmd)
+	}
+	// toolInput.path is NOT in the JS's allowlist, so it stays unmutated.
+	if _, ok := ti["path"]; ok {
+		t.Fatalf("path should not be in updatedInput; got %v", ti["path"])
+	}
+}
+
+// No PII present → script returns {decision: "allow"} with no updatedInput.
+func TestPIIRedactor_NoPII_NoMutation(t *testing.T) {
+	ev := hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  "how do I reverse a list in Python?",
+	}
+	res := runPII(t, ev)
+	if len(res.UpdatedInput) > 0 {
+		t.Fatalf("updatedInput non-empty on clean input: %v", res.UpdatedInput)
+	}
+}
+
+// Idempotency: once redacted, running again must be a no-op.
+func TestPIIRedactor_Idempotent(t *testing.T) {
+	once := hooks.Event{
+		EventID:   "e",
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  "user@example.com and +14155551212",
+	}
+	r1 := runPII(t, once)
+	redacted, _ := r1.UpdatedInput["rawInput"].(string)
+	if redacted == "" {
+		t.Fatal("first pass produced no mutation")
+	}
+	twice := hooks.Event{
+		EventID:   "e2",
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  redacted,
+	}
+	r2 := runPII(t, twice)
+	if len(r2.UpdatedInput) > 0 {
+		t.Fatalf("second pass mutated already-redacted text: %v", r2.UpdatedInput)
+	}
+}
+
+// BenchmarkPIIRedactor_1KiB sanity-checks the <1ms median target. Informational.
+func BenchmarkPIIRedactor_1KiB(b *testing.B) {
+	src, err := builtin.Source("pii-redactor.js")
+	if err != nil {
+		b.Fatalf("load: %v", err)
+	}
+	cfg := hooks.HookConfig{
+		ID:          builtin.BuiltinEventID("pii-redactor", "user_prompt_submit"),
+		TenantID:    hooks.SentinelTenantID,
+		Event:       hooks.EventUserPromptSubmit,
+		HandlerType: hooks.HandlerScript,
+		Source:      hooks.SourceBuiltin,
+		Config:      map[string]any{"source": string(src)},
+		Version:     1,
+		Enabled:     true,
+	}
+	// ~1 KiB mostly-clean text with one email at the tail.
+	base := strings.Repeat("the quick brown fox jumps over the lazy dog. ", 24) // 1080 bytes
+	payload := base[:1010] + " u@example.com"
+	ev := hooks.Event{
+		EventID:   "bench",
+		HookEvent: hooks.EventUserPromptSubmit,
+		RawInput:  payload,
+	}
+
+	h := NewScriptHandler(8, 4, 64)
+	b.ResetTimer()
+	for b.Loop() {
+		res := &hooks.ScriptResult{}
+		ctx := hooks.WithScriptResult(context.Background(), res)
+		if _, err := h.Execute(ctx, cfg, ev); err != nil {
+			b.Fatalf("exec: %v", err)
+		}
+	}
+}