diff --git a/compiler.go b/compiler.go
index 733d5f3b21..3b00bc3cab 100644
--- a/compiler.go
+++ b/compiler.go
@@ -54,30 +54,45 @@ func (c *Compiler) getVariables(t *ast.Task, call *Call, evaluateShVars bool) (*
 		result.Set(k, ast.Var{Value: v})
 	}
 
+	// Share a single Cache across every rangeFunc invocation below. The
+	// previous implementation allocated a fresh Cache per variable, which
+	// caused Replace -> ToCacheMap to rebuild the full cacheMap on every
+	// call. SyncVarSet keeps the cacheMap in sync after each result.Set so
+	// subsequent Replace calls on the same cache can reuse it.
+	sharedCache := &templater.Cache{Vars: result}
+
 	getRangeFunc := func(dir string) func(k string, v ast.Var) error {
 		return func(k string, v ast.Var) error {
-			cache := &templater.Cache{Vars: result}
+			// Each variable is processed independently, so clear any sticky
+			// error from a previous template before evaluating this one.
+			sharedCache.ResetErr()
 			// Replace values
-			newVar := templater.ReplaceVar(v, cache)
+			newVar := templater.ReplaceVar(v, sharedCache)
 			// If the variable should not be evaluated, but is nil, set it to an empty string
 			// This stops empty interface errors when using the templater to replace values later
 			// Preserve the Sh field so it can be displayed in summary
 			if !evaluateShVars && newVar.Value == nil {
-				result.Set(k, ast.Var{Value: "", Sh: newVar.Sh})
+				out := ast.Var{Value: "", Sh: newVar.Sh}
+				result.Set(k, out)
+				sharedCache.SyncVarSet(k, out)
 				return nil
 			}
 			// If the variable should not be evaluated and it is set, we can set it and return
 			if !evaluateShVars {
-				result.Set(k, ast.Var{Value: newVar.Value, Sh: newVar.Sh})
+				out := ast.Var{Value: newVar.Value, Sh: newVar.Sh}
+				result.Set(k, out)
+				sharedCache.SyncVarSet(k, out)
 				return nil
 			}
 			// Now we can check for errors since we've handled all the cases when we don't want to evaluate
-			if err := cache.Err(); err != nil {
+			if err := sharedCache.Err(); err != nil {
 				return err
 			}
 			// If the variable is already set, we can set it and return
 			if newVar.Value != nil || newVar.Sh == nil {
-				result.Set(k, ast.Var{Value: newVar.Value})
+				out := ast.Var{Value: newVar.Value}
+				result.Set(k, out)
+				sharedCache.SyncVarSet(k, out)
 				return nil
 			}
 			// If the variable is dynamic, we need to resolve it first
@@ -85,7 +100,9 @@ func (c *Compiler) getVariables(t *ast.Task, call *Call, evaluateShVars bool) (*
 			if err != nil {
 				return err
 			}
-			result.Set(k, ast.Var{Value: static})
+			out := ast.Var{Value: static}
+			result.Set(k, out)
+			sharedCache.SyncVarSet(k, out)
 			return nil
 		}
 	}
@@ -95,11 +112,11 @@ func (c *Compiler) getVariables(t *ast.Task, call *Call, evaluateShVars bool) (*
 	if t != nil {
 		// NOTE(@andreynering): We're manually joining these paths here because
 		// this is the raw task, not the compiled one.
-		cache := &templater.Cache{Vars: result}
-		dir := templater.Replace(t.Dir, cache)
-		if err := cache.Err(); err != nil {
+		dir := templater.Replace(t.Dir, sharedCache)
+		if err := sharedCache.Err(); err != nil {
 			return nil, err
 		}
+		sharedCache.ResetErr()
 		dir = filepathext.SmartJoin(c.Dir, dir)
 		taskRangeFunc = getRangeFunc(dir)
 	}
diff --git a/internal/templater/templater.go b/internal/templater/templater.go
index 896cba23c1..7a0af39a5f 100644
--- a/internal/templater/templater.go
+++ b/internal/templater/templater.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"maps"
 	"strings"
+	"sync"
 
 	"github.com/go-task/template"
 
@@ -12,6 +13,76 @@ import (
 	"github.com/go-task/task/v3/taskfile/ast"
 )
 
+// dataMapPool reuses map[string]any backing memory across [ReplaceWithExtra]
+// calls. When a template might mutate the dot via sprig's set/unset, we
+// clone cache.cacheMap into a fresh map so those mutations cannot leak back
+// into cache.cacheMap. The maps are short-lived and identically shaped, so a
+// pool drops the per-call allocation without changing semantics.
+var dataMapPool = sync.Pool{
+	New: func() any {
+		m := make(map[string]any, 64)
+		return &m
+	},
+}
+
+func acquireDataMap() *map[string]any {
+	return dataMapPool.Get().(*map[string]any)
+}
+
+func releaseDataMap(m *map[string]any) {
+	clear(*m)
+	dataMapPool.Put(m)
+}
+
+// templateMayMutateDot reports whether a template source string might mutate
+// its dot (root data map). The only functions registered in templateFuncs
+// that mutate the dict passed to them are sprig's `set` and `unset`. Other
+// sprig mutators (push/append/prepend on slices) operate on slice values
+// retrieved from the dict — they do not modify the dict itself, and the
+// original code's shallow [maps.Clone] never protected against those either.
+//
+// This is a conservative substring check: false positives are fine (they
+// just force an unnecessary clone), false negatives would leak mutations.
+// "set" appearing inside a literal string ({{"set"}}) or inside an unrelated
+// identifier (settings, subset) is treated as potentially mutating, which is
+// safe. Checking for "set" alone also catches "unset".
+func templateMayMutateDot(s string) bool {
+	return strings.Contains(s, "set")
+}
+
+// parsedTemplateCache memoizes parsed [template.Template] objects keyed by
+// their source string. Each call to template.New("").Funcs(templateFuncs)
+// copies the ~170-entry FuncMap into a fresh Template (sprig + go-task
+// builtins) — that copy is the single largest allocator on the hot path of
+// listing tasks in a project with many includes, because the same merged
+// TaskfileEnv values are processed once per task.
+//
+// Caching the parsed Template is safe: once parsed, a Template may be
+// executed concurrently from multiple goroutines (Go docs guarantee this),
+// and Execute reads from but does not mutate the Template. The cache key is
+// the unparsed source — sufficient because templateFuncs is a package-level
+// singleton.
+//
+// We cache errors as well so that a malformed template surfaces the same
+// error on every call instead of being re-parsed each time.
+var parsedTemplateCache sync.Map // map[string]parsedTemplateEntry
+
+type parsedTemplateEntry struct {
+	tpl *template.Template
+	err error
+}
+
+func cachedParse(text string) (*template.Template, error) {
+	if v, ok := parsedTemplateCache.Load(text); ok {
+		entry := v.(parsedTemplateEntry)
+		return entry.tpl, entry.err
+	}
+	tpl, err := template.New("").Funcs(templateFuncs).Parse(text)
+	actual, _ := parsedTemplateCache.LoadOrStore(text, parsedTemplateEntry{tpl: tpl, err: err})
+	entry := actual.(parsedTemplateEntry)
+	return entry.tpl, entry.err
+}
+
 // Cache is a help struct that allow us to call "replaceX" funcs multiple
 // times, without having to check for error each time. The first error that
 // happen will be assigned to r.err, and consecutive calls to funcs will just
@@ -31,6 +102,38 @@ func (r *Cache) Err() error {
 	return r.err
 }
 
+// ResetErr clears the sticky error flag so a single Cache can be reused for
+// a sequence of independent template operations. Without this, the first
+// failed Replace would short-circuit every subsequent call on the same
+// Cache.
+func (r *Cache) ResetErr() {
+	r.err = nil
+}
+
+// SyncVarSet updates the internal cacheMap after the caller mutates Vars via
+// [ast.Vars.Set]. This lets a single Cache be reused across many Replace
+// calls (each interleaved with a Vars.Set) without rebuilding the entire
+// cacheMap from scratch via [ast.Vars.ToCacheMap]. The mirroring rules match
+// [ast.Vars.ToCacheMap]: dynamic-only entries are excluded, Live takes
+// precedence over Value.
+//
+// No-op if cacheMap has not yet been initialized — the lazy init in Replace
+// will pick up the value on first use.
+func (r *Cache) SyncVarSet(key string, v ast.Var) {
+	if r.cacheMap == nil {
+		return
+	}
+	if v.Sh != nil && *v.Sh != "" {
+		delete(r.cacheMap, key)
+		return
+	}
+	if v.Live != nil {
+		r.cacheMap[key] = v.Live
+	} else {
+		r.cacheMap[key] = v.Value
+	}
+}
+
 func ResolveRef(ref string, cache *Cache) any {
 	// If there is already an error, do nothing
 	if cache.err != nil {
@@ -45,7 +148,7 @@ func ResolveRef(ref string, cache *Cache) any {
 	if ref == "." {
 		return cache.cacheMap
 	}
-	t, err := template.New("resolver").Funcs(templateFuncs).Parse(fmt.Sprintf("{{%s}}", ref))
+	t, err := cachedParse(fmt.Sprintf("{{%s}}", ref))
 	if err != nil {
 		cache.err = err
 		return nil
@@ -73,16 +176,58 @@ func ReplaceWithExtra[T any](v T, cache *Cache, extra map[string]any) T {
 		cache.cacheMap = cache.Vars.ToCacheMap()
 	}
 
-	// Create a copy of the cache map to avoid editing the original
-	// If there is extra data, merge it with the cache map
-	data := maps.Clone(cache.cacheMap)
-	if extra != nil {
-		maps.Copy(data, extra)
+	// Decide whether the template can read directly from cache.cacheMap or
+	// whether we must clone it. Cloning is required when there is `extra`
+	// data to merge in, or when any template traversed below might mutate
+	// the dict via sprig's set/unset. For all other cases the clone is pure
+	// overhead — tpl.Execute only reads from the data map.
+	//
+	// nil values (nil interface, nil *string) cannot run any template at
+	// all, so they don't need a cloned data map. Strings are checked for
+	// "set" anywhere. For other concrete types we conservatively clone.
+	mayMutate := false
+	switch {
+	case extra != nil:
+		mayMutate = true
+	case any(v) == nil:
+		// nil interface — TraverseStringsFunc has no strings to visit.
+		mayMutate = false
+	default:
+		switch tv := any(v).(type) {
+		case string:
+			mayMutate = templateMayMutateDot(tv)
+		case *string:
+			// nil pointer — no template runs.
+			mayMutate = tv != nil && templateMayMutateDot(*tv)
+		default:
+			// []string, map, struct, etc. — don't risk it.
+			mayMutate = true
+		}
+	}
+
+	var data map[string]any
+	if mayMutate {
+		dataPtr := acquireDataMap()
+		defer releaseDataMap(dataPtr)
+		data = *dataPtr
+		maps.Copy(data, cache.cacheMap)
+		if extra != nil {
+			maps.Copy(data, extra)
+		}
+	} else {
+		data = cache.cacheMap
 	}
 
 	// Traverse the value and parse any template variables
 	copy, err := deepcopy.TraverseStringsFunc(v, func(v string) (string, error) {
-		tpl, err := template.New("").Funcs(templateFuncs).Parse(v)
+		// Skip the template engine entirely if the string has no actions.
+		// Go templates only fire on `{{`; pure literals can short-circuit.
+		// This is a large win when iterating many merged taskfile env vars
+		// whose values are static strings.
+		if !strings.Contains(v, "{{") {
+			return v, nil
+		}
+		tpl, err := cachedParse(v)
 		if err != nil {
 			return v, err
 		}