diff --git a/bench/template_cel_env_bench_test.go b/bench/template_cel_env_bench_test.go
new file mode 100644
index 000000000..c7e23cd66
--- /dev/null
+++ b/bench/template_cel_env_bench_test.go
@@ -0,0 +1,94 @@
+package bench_test
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	dutyctx "github.com/flanksource/duty/context"
+	"github.com/flanksource/gomplate/v3"
+	"github.com/google/cel-go/cel"
+	celtypes "github.com/google/cel-go/common/types"
+	"github.com/google/cel-go/common/types/ref"
+)
+
+// BenchmarkRunTemplateCELCacheHitRegisteredEnvFuncs isolates the duty-side
+// overhead of constructing registered CEL env functions on every RunTemplate
+// call. The expression does not call any registered function; the benchmark only
+// varies how many functions are registered globally.
+func BenchmarkRunTemplateCELCacheHitRegisteredEnvFuncs(b *testing.B) {
+	env := map[string]any{
+		"id":          "0192f0a4-1234-7000-8000-aaaaaaaaaaaa",
+		"namespace":   "default",
+		"name":        "nginx-7c5ddbdf54-abcde",
+		"index":       42,
+		"config_type": "Kubernetes::Pod",
+	}
+
+	for _, registeredFuncs := range []int{0, 18, 64} {
+		b.Run(fmt.Sprintf("registered=%02d", registeredFuncs), func(b *testing.B) {
+			installBenchmarkCelEnvFuncs(b, registeredFuncs)
+
+			ctx := dutyctx.New()
+			tmpl := gomplate.Template{
+				Expression: `config_type == "Kubernetes::Pod"`,
+				CacheKey:   fmt.Sprintf("benchmark.run-template.cel-env-funcs.%d", registeredFuncs),
+				CacheTime:  time.Hour,
+			}
+
+			// Warm gomplate's compiled CEL program cache. Any measured allocation after
+			// this point should be steady-state RunTemplate overhead, not CEL compile.
+			if _, err := ctx.RunTemplateBool(tmpl, env); err != nil {
+				b.Fatal(err)
+			}
+
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				ok, err := ctx.RunTemplateBool(tmpl, env)
+				if err != nil {
+					b.Fatal(err)
+				}
+				if !ok {
+					b.Fatal("expected expression to evaluate true")
+				}
+			}
+		})
+	}
+}
+
+func installBenchmarkCelEnvFuncs(b *testing.B, count int) {
+	b.Helper()
+
+	oldCelEnvFuncs := dutyctx.CelEnvFuncs
+	oldTemplateFuncs := dutyctx.TemplateFuncs
+
+	dutyctx.CelEnvFuncs = make(map[string]func(dutyctx.Context) cel.EnvOption, count)
+	for i := 0; i < count; i++ {
+		name := fmt.Sprintf("bench.func_%02d", i)
+		dutyctx.CelEnvFuncs[name] = benchmarkCelEnvFunc(name, fmt.Sprintf("bench_func_%02d_string", i))
+	}
+	dutyctx.TemplateFuncs = nil
+
+	b.Cleanup(func() {
+		dutyctx.CelEnvFuncs = oldCelEnvFuncs
+		dutyctx.TemplateFuncs = oldTemplateFuncs
+	})
+}
+
+func benchmarkCelEnvFunc(name, overloadID string) func(dutyctx.Context) cel.EnvOption {
+	return func(ctx dutyctx.Context) cel.EnvOption {
+		return cel.Function(name,
+			cel.Overload(overloadID,
+				[]*cel.Type{cel.StringType},
+				cel.StringType,
+				cel.UnaryBinding(func(arg ref.Val) ref.Val {
+					// Capture ctx like production DB/catalog functions do. This binding is
+					// intentionally never called by the benchmark expression.
+					_ = ctx
+					return celtypes.String(fmt.Sprintf("%s:%v", name, arg.Value()))
+				}),
+			),
+		)
+	}
+}
diff --git a/context/template.go b/context/template.go
index 313ef73dc..d51213c71 100644
--- a/context/template.go
+++ b/context/template.go
@@ -3,6 +3,7 @@ package context
 import (
 	"fmt"
 	"strconv"
+	"strings"
 
 	"github.com/flanksource/commons/collections"
 	"github.com/flanksource/commons/logger"
@@ -23,9 +24,7 @@ func (k Context) RunTemplate(t gomplate.Template, env map[string]any) (string, e
 	} else {
 		l.V(1).Infof("Running template: %s", t.String())
 	}
-	for _, f := range CelEnvFuncs {
-		t.CelEnvs = append(t.CelEnvs, f(k))
-	}
+	appendReferencedCelEnvFuncs(k, &t)
 	if t.Functions == nil {
 		t.Functions = make(map[string]any)
 	}
@@ -78,6 +77,61 @@ func (k Context) RunTemplate(t gomplate.Template, env map[string]any) (string, e
 	return val, nil
 }
 
+func appendReferencedCelEnvFuncs(ctx Context, t *gomplate.Template) {
+	if t.Expression == "" || !strings.Contains(t.Expression, "(") {
+		return
+	}
+
+	for name, f := range CelEnvFuncs {
+		if celExpressionCalls(t.Expression, name) || (strings.HasSuffix(name, "Cel") && celExpressionCalls(t.Expression, strings.TrimSuffix(name, "Cel"))) {
+			t.CelEnvs = append(t.CelEnvs, f(ctx))
+		}
+	}
+}
+
+func celExpressionCalls(expr, name string) bool {
+	if name == "" {
+		return false
+	}
+
+	for offset := 0; offset < len(expr); {
+		idx := strings.Index(expr[offset:], name)
+		if idx < 0 {
+			return false
+		}
+		idx += offset
+		afterName := idx + len(name)
+		if isCelNameBoundary(expr, idx, afterName) {
+			for afterName < len(expr) && isCELWhitespace(expr[afterName]) {
+				afterName++
+			}
+			if afterName < len(expr) && expr[afterName] == '(' {
+				return true
+			}
+		}
+		offset = idx + len(name)
+	}
+	return false
+}
+
+func isCelNameBoundary(expr string, start, end int) bool {
+	if start > 0 && isCELNameChar(expr[start-1]) {
+		return false
+	}
+	if end < len(expr) && isCELNameChar(expr[end]) {
+		return false
+	}
+	return true
+}
+
+func isCELNameChar(ch byte) bool {
+	return ch == '.' || ch == '_' || ('0' <= ch && ch <= '9') || ('A' <= ch && ch <= 'Z') || ('a' <= ch && ch <= 'z')
+}
+
+func isCELWhitespace(ch byte) bool {
+	return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r'
+}
+
 func (k Context) RunTemplateBool(t gomplate.Template, env map[string]any) (bool, error) {
 	output, err := k.RunTemplate(t, env)
 	if err != nil {
diff --git a/context/template_test.go b/context/template_test.go
index 3b55949f9..d5897f6e0 100644
--- a/context/template_test.go
+++ b/context/template_test.go
@@ -1,12 +1,101 @@
 package context
 
 import (
+	"sync/atomic"
 	"testing"
 
 	"github.com/flanksource/gomplate/v3"
+	"github.com/google/cel-go/cel"
+	celtypes "github.com/google/cel-go/common/types"
+	"github.com/google/cel-go/common/types/ref"
 	. "github.com/onsi/gomega"
 )
 
+func TestRunTemplateOnlyBuildsReferencedCelEnvFuncs(t *testing.T) {
+	g := NewWithT(t)
+	oldCelEnvFuncs := CelEnvFuncs
+	oldTemplateFuncs := TemplateFuncs
+	defer func() {
+		CelEnvFuncs = oldCelEnvFuncs
+		TemplateFuncs = oldTemplateFuncs
+	}()
+
+	var usedBuilt atomic.Int32
+	var unusedBuilt atomic.Int32
+	CelEnvFuncs = map[string]func(Context) cel.EnvOption{
+		"bench.usedCel": func(ctx Context) cel.EnvOption {
+			usedBuilt.Add(1)
+			return cel.Function("bench.used",
+				cel.Overload("bench_used_string",
+					[]*cel.Type{cel.StringType},
+					cel.BoolType,
+					cel.UnaryBinding(func(arg ref.Val) ref.Val {
+						return celtypes.Bool(arg.Value() == "default")
+					}),
+				),
+			)
+		},
+		"bench.unused": func(ctx Context) cel.EnvOption {
+			unusedBuilt.Add(1)
+			return cel.Function("bench.unused",
+				cel.Overload("bench_unused_string",
+					[]*cel.Type{cel.StringType},
+					cel.StringType,
+					cel.UnaryBinding(func(arg ref.Val) ref.Val {
+						return celtypes.String(arg.Value().(string))
+					}),
+				),
+			)
+		},
+	}
+	TemplateFuncs = nil
+
+	ctx := New()
+	env := map[string]any{"config_namespace": "default"}
+
+	ok, err := ctx.RunTemplateBool(gomplate.Template{
+		Expression: `config_namespace == "default"`,
+		CacheKey:   "test.run-template.no-registered-cel-func",
+	}, env)
+	g.Expect(err).NotTo(HaveOccurred())
+	g.Expect(ok).To(BeTrue())
+	g.Expect(usedBuilt.Load()).To(Equal(int32(0)))
+	g.Expect(unusedBuilt.Load()).To(Equal(int32(0)))
+
+	ok, err = ctx.RunTemplateBool(gomplate.Template{
+		Expression: `bench.used(config_namespace)`,
+		CacheKey:   "test.run-template.referenced-cel-func",
+	}, env)
+	g.Expect(err).NotTo(HaveOccurred())
+	g.Expect(ok).To(BeTrue())
+	g.Expect(usedBuilt.Load()).To(Equal(int32(1)))
+	g.Expect(unusedBuilt.Load()).To(Equal(int32(0)))
+}
+
+func TestCelExpressionCalls(t *testing.T) {
+	tests := []struct {
+		name string
+		expr string
+		fn   string
+		want bool
+	}{
+		{name: "direct namespaced call", expr: `bench.used(config_namespace)`, fn: "bench.used", want: true},
+		{name: "whitespace before args", expr: `bench.used (config_namespace)`, fn: "bench.used", want: true},
+		{name: "prefix is not a call", expr: `bench.used_extra(config_namespace)`, fn: "bench.used", want: false},
+		{name: "suffix is not a call", expr: `other.bench.used(config_namespace)`, fn: "bench.used", want: false},
+		{name: "similar db function prefix", expr: `db.external_users_all(scraper_id)`, fn: "db.external_users", want: false},
+		{name: "exact db function", expr: `db.external_users_all(scraper_id)`, fn: "db.external_users_all", want: true},
+		{name: "no function call", expr: `config_type == "Kubernetes::Pod"`, fn: "db.external_users", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			g := NewWithT(t)
+			g.Expect(celExpressionCalls(tt.expr, tt.fn)).To(Equal(tt.want))
+		})
+	}
+}
+
 func TestRunTemplate(t *testing.T) {
 	t.Parallel()