diff --git a/resolver-go/cmd/api-server/main.go b/resolver-go/cmd/api-server/main.go
index bf03610..6a9e144 100644
--- a/resolver-go/cmd/api-server/main.go
+++ b/resolver-go/cmd/api-server/main.go
@@ -8,7 +8,9 @@ import (
 	"time"
 
 	"github.com/tgckpg/resolver-go/internal/closure"
+	"github.com/tgckpg/resolver-go/internal/compilecache"
 	"github.com/tgckpg/resolver-go/internal/generated"
+	"github.com/tgckpg/resolver-go/internal/minifier/css"
 	"github.com/tgckpg/resolver-go/internal/resolver"
 )
 
@@ -23,8 +25,13 @@ func main() {
 	}
 
 	h := handler{
-		r:       r,
-		closure: closure.NewCompileCache(2),
+		r: r,
+		jsCache: compilecache.New(
+			closure.NewCompiler(), 2, 128,
+		),
+		cssCache: compilecache.New(
+			css.NewEsbuildCompiler(), 2, 128,
+		),
 	}
 	http.HandleFunc("/", h.index)
 	log.Printf("botan-api listening on %s", *addr)
@@ -32,8 +39,9 @@ func main() {
 }
 
 type handler struct {
-	r       *resolver.Resolver
-	closure *closure.CompileCache
+	r        *resolver.Resolver
+	jsCache  *compilecache.Cache
+	cssCache *compilecache.Cache
 }
 
 func (h handler) index(w http.ResponseWriter, req *http.Request) {
@@ -71,7 +79,8 @@ func (h handler) index(w http.ResponseWriter, req *http.Request) {
 	}
 
 	if outMode == resolver.ModeJS {
-		if compiled, ok := h.closure.Get(res.Hash); ok {
+		state, compiled, err := h.jsCache.Get(res.Hash)
+		if state == compilecache.Ready {
 			w.Header().Set("Content-Type", "application/javascript")
 			w.Header().Set("X-Botan-Compiled", "hit")
 			elapsed := time.Since(timerStart)
@@ -86,31 +95,43 @@ func (h handler) index(w http.ResponseWriter, req *http.Request) {
 			return
 		}
 
-		h.closure.Enqueue(closure.CompileJob{
-			Hash:          res.Hash,
-			Mode:          "js",
-			ExternSources: jsExterns,
-			JSSources: []closure.SourceInput{
-				{
-					Name:   "botanjs-" + res.Hash + ".js",
-					Source: string(res.Content),
+		h.jsCache.Enqueue(compilecache.Job{
+			Hash: res.Hash,
+			Mode: "js",
+			Payload: closure.CompilePayload{
+				ExternSources: jsExterns,
+				JSSources: []closure.SourceInput{
+					{
+						Name:   "botanjs-" + res.Hash + ".js",
+						Source: string(res.Content),
+					},
+				},
+				Defines: map[string]any{
+					"DEBUG": false,
 				},
 			},
-			Defines: map[string]any{
-				"DEBUG": false,
+		})
+	} else if outMode == resolver.ModeCSS {
+		state, compiled, _ := h.cssCache.Get(res.Hash)
+		if state == compilecache.Ready {
+			w.Header().Set("Content-Type", "text/css")
+			w.Header().Set("X-Botan-Compiled", "hit")
+			elapsed := time.Since(timerStart)
+			w.Header().Set("X-Botan-Resolve-Time", elapsed.String())
+			w.Write(compiled)
+			return
+		}
+
+		h.cssCache.Enqueue(compilecache.Job{
+			Hash: res.Hash,
+			Mode: "css",
+			Payload: css.CompilePayload{
+				Name:   "style.css",
+				Source: string(res.Content),
 			},
 		})
 	}
 
-	// Compatibility flags:
-	//   rjs/rcss/ojs/ocss => content
-	//   hjs/hcss          => hash filename only
-	//   js/css            => currently content; cluster compiler can switch this later.
-	if strings.HasPrefix(modeText, "h") {
-		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
-		_, _ = w.Write([]byte(res.Hash))
-		return
-	}
 	w.Header().Set("Content-Type", res.ContentType)
 	w.Header().Set("X-Botan-Compiled", "miss")
 
diff --git a/resolver-go/go.mod b/resolver-go/go.mod
index ad1c6f3..4e0a19f 100644
--- a/resolver-go/go.mod
+++ b/resolver-go/go.mod
@@ -1,3 +1,7 @@
 module github.com/tgckpg/resolver-go
 
 go 1.26
+
+require github.com/evanw/esbuild v0.28.1
+
+require golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 // indirect
diff --git a/resolver-go/go.sum b/resolver-go/go.sum
index e69de29..82e4e7e 100644
--- a/resolver-go/go.sum
+++ b/resolver-go/go.sum
@@ -0,0 +1,4 @@
+github.com/evanw/esbuild v0.28.1 h1:ds+yuRyUaZGx++GR56CrCeuXh8PVhVM4xq8v7PNELFc=
+github.com/evanw/esbuild v0.28.1/go.mod h1:D2vIQZqV/vIf/VRHtViaUtViZmG7o+kKmlBfVQuRi48=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8 h1:0A+M6Uqn+Eje4kHMK80dtF3JCXC4ykBgQG4Fe06QRhQ=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/resolver-go/internal/closure/cache.go b/resolver-go/internal/closure/cache.go
deleted file mode 100644
index 547bdf4..0000000
--- a/resolver-go/internal/closure/cache.go
+++ /dev/null
@@ -1,87 +0,0 @@
-package closure
-
-import (
-	"context"
-	"errors"
-	"log"
-	"time"
-)
-
-func NewCompileCache(workers int) *CompileCache {
-	c := &CompileCache{
-		client:  NewClientFromEnv(),
-		states:  make(map[string]CompileState),
-		results: make(map[string][]byte),
-		errors:  make(map[string]error),
-		jobs:    make(chan CompileJob, 128),
-	}
-
-	for i := 0; i < workers; i++ {
-		go c.worker()
-	}
-
-	return c
-}
-
-func (c *CompileCache) Get(hash string) ([]byte, bool) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	if c.states[hash] != CompileReady {
-		return nil, false
-	}
-
-	return c.results[hash], true
-}
-
-func (c *CompileCache) Enqueue(job CompileJob) {
-	c.mu.Lock()
-
-	switch c.states[job.Hash] {
-	case CompilePending, CompileReady:
-		c.mu.Unlock()
-		return
-	}
-
-	c.states[job.Hash] = CompilePending
-	c.mu.Unlock()
-
-	select {
-	case c.jobs <- job:
-	default:
-		// Queue full. Don't block request path.
-		c.mu.Lock()
-		c.states[job.Hash] = CompileMissing
-		c.errors[job.Hash] = errors.New("compile queue full")
-		c.mu.Unlock()
-	}
-}
-
-func (c *CompileCache) worker() {
-	for job := range c.jobs {
-		ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
-
-		req := CompileRequest{
-			ExternSources: job.ExternSources,
-			JSSources:     job.JSSources,
-			Defines:       job.Defines,
-		}
-
-		c.client.DebugPrintCurl(ctx, req)
-
-		out, err := c.client.Compile(ctx, req)
-		cancel()
-
-		c.mu.Lock()
-		if err == nil {
-			c.states[job.Hash] = CompileReady
-			c.results[job.Hash] = out
-			delete(c.errors, job.Hash)
-		} else {
-			log.Printf("compile failed: %v", err)
-			c.states[job.Hash] = CompileFailed
-			c.errors[job.Hash] = err
-		}
-		c.mu.Unlock()
-	}
-}
diff --git a/resolver-go/internal/closure/compiler.go b/resolver-go/internal/closure/compiler.go
new file mode 100644
index 0000000..c0e2432
--- /dev/null
+++ b/resolver-go/internal/closure/compiler.go
@@ -0,0 +1,31 @@
+package closure
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/tgckpg/resolver-go/internal/compilecache"
+)
+
+type Compiler struct {
+	client *Client
+}
+
+func NewCompiler() *Compiler {
+	return &Compiler{client: NewClientFromEnv()}
+}
+
+func (c *Compiler) Compile(ctx context.Context, job compilecache.Job) ([]byte, error) {
+	payload, ok := job.Payload.(CompilePayload)
+	if !ok {
+		return nil, fmt.Errorf("closure compiler got invalid payload type %T", job.Payload)
+	}
+
+	req := CompileRequest{
+		ExternSources: payload.ExternSources,
+		JSSources:     payload.JSSources,
+		Defines:       payload.Defines,
+	}
+
+	return c.client.Compile(ctx, req)
+}
diff --git a/resolver-go/internal/closure/types.go b/resolver-go/internal/closure/types.go
index 064cd92..ea7a464 100644
--- a/resolver-go/internal/closure/types.go
+++ b/resolver-go/internal/closure/types.go
@@ -1,20 +1,9 @@
 package closure
 
-import "sync"
-
-type CompileState int
-
-const (
-	CompileMissing CompileState = iota
-	CompilePending
-	CompileReady
-	CompileFailed
-)
-
-type CompileRequest struct {
-	ExternSources []SourceInput  `json:"externSources,omitempty"`
-	JSSources     []SourceInput  `json:"jsSources"`
-	Defines       map[string]any `json:"defines,omitempty"`
+type CompilePayload struct {
+	ExternSources []SourceInput
+	JSSources     []SourceInput
+	Defines       map[string]any
 }
 
 type SourceInput struct {
@@ -22,22 +11,10 @@ type SourceInput struct {
 	Source string `json:"source"`
 }
 
-type CompileJob struct {
-	Hash string
-	Mode string
-
-	ExternSources []SourceInput
-	JSSources     []SourceInput
-	Defines       map[string]any
-}
-
-type CompileCache struct {
-	client  *Client
-	mu      sync.Mutex
-	states  map[string]CompileState
-	results map[string][]byte
-	errors  map[string]error
-	jobs    chan CompileJob
+type CompileRequest struct {
+	ExternSources []SourceInput  `json:"externSources,omitempty"`
+	JSSources     []SourceInput  `json:"jsSources"`
+	Defines       map[string]any `json:"defines,omitempty"`
 }
 
 type CompileResponse struct {
diff --git a/resolver-go/internal/compilecache/cache.go b/resolver-go/internal/compilecache/cache.go
new file mode 100644
index 0000000..85b8903
--- /dev/null
+++ b/resolver-go/internal/compilecache/cache.go
@@ -0,0 +1,89 @@
+package compilecache
+
+import (
+	"context"
+)
+
+func New(compiler Compiler, workers int, queueSize int) *Cache {
+	if workers <= 0 {
+		workers = 1
+	}
+	if queueSize <= 0 {
+		queueSize = 128
+	}
+
+	c := &Cache{
+		compiler: compiler,
+		states:   make(map[string]State),
+		results:  make(map[string][]byte),
+		errors:   make(map[string]error),
+		jobs:     make(chan Job, queueSize),
+	}
+
+	for i := 0; i < workers; i++ {
+		go c.worker()
+	}
+
+	return c
+}
+
+func (c *Cache) Get(hash string) (State, []byte, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	state, ok := c.states[hash]
+	if !ok {
+		return Missing, nil, nil
+	}
+
+	switch state {
+	case Ready:
+		return Ready, c.results[hash], nil
+	case Failed:
+		return Failed, nil, c.errors[hash]
+	default:
+		return state, nil, nil
+	}
+}
+
+func (c *Cache) Enqueue(job Job) State {
+	c.mu.Lock()
+
+	state, ok := c.states[job.Hash]
+	if ok {
+		c.mu.Unlock()
+		return state
+	}
+
+	c.states[job.Hash] = Pending
+	c.mu.Unlock()
+
+	// Do not hold the lock while sending.
+	c.jobs <- job
+
+	return Pending
+}
+
+func (c *Cache) worker() {
+	for job := range c.jobs {
+		c.run(job)
+	}
+}
+
+func (c *Cache) run(job Job) {
+	result, err := c.compiler.Compile(context.Background(), job)
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if err != nil {
+		c.states[job.Hash] = Failed
+		c.errors[job.Hash] = err
+		delete(c.results, job.Hash)
+		return
+	}
+
+	c.states[job.Hash] = Ready
+	c.results[job.Hash] = result
+	delete(c.errors, job.Hash)
+}
diff --git a/resolver-go/internal/compilecache/types.go b/resolver-go/internal/compilecache/types.go
new file mode 100644
index 0000000..1fa6ab2
--- /dev/null
+++ b/resolver-go/internal/compilecache/types.go
@@ -0,0 +1,36 @@
+package compilecache
+
+import (
+	"context"
+	"sync"
+)
+
+type State int
+
+const (
+	Missing State = iota
+	Pending
+	Ready
+	Failed
+)
+
+type Job struct {
+	Hash string
+	Mode string
+
+	Payload any
+}
+
+type Compiler interface {
+	Compile(ctx context.Context, job Job) ([]byte, error)
+}
+
+type Cache struct {
+	compiler Compiler
+
+	mu      sync.Mutex
+	states  map[string]State
+	results map[string][]byte
+	errors  map[string]error
+	jobs    chan Job
+}
diff --git a/resolver-go/internal/minifier/css/compiler.go b/resolver-go/internal/minifier/css/compiler.go
new file mode 100644
index 0000000..ad0e63e
--- /dev/null
+++ b/resolver-go/internal/minifier/css/compiler.go
@@ -0,0 +1,34 @@
+package css
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/evanw/esbuild/pkg/api"
+	"github.com/tgckpg/resolver-go/internal/compilecache"
+)
+
+func NewEsbuildCompiler() *EsbuildCompiler {
+	return &EsbuildCompiler{}
+}
+
+func (c *EsbuildCompiler) Compile(ctx context.Context, job compilecache.Job) ([]byte, error) {
+	payload, ok := job.Payload.(CompilePayload)
+	if !ok {
+		return nil, fmt.Errorf("esbuild css compiler got invalid payload type %T", job.Payload)
+	}
+
+	result := api.Transform(payload.Source, api.TransformOptions{
+		Loader:            api.LoaderCSS,
+		Sourcefile:        payload.Name,
+		MinifyWhitespace:  true,
+		MinifyIdentifiers: true,
+		MinifySyntax:      true,
+	})
+
+	if len(result.Errors) > 0 {
+		return nil, fmt.Errorf("css compile failed: %s", result.Errors[0].Text)
+	}
+
+	return result.Code, nil
+}
diff --git a/resolver-go/internal/minifier/css/types.go b/resolver-go/internal/minifier/css/types.go
new file mode 100644
index 0000000..5191dee
--- /dev/null
+++ b/resolver-go/internal/minifier/css/types.go
@@ -0,0 +1,8 @@
+package css
+
+type CompilePayload struct {
+	Name   string
+	Source string
+}
+
+type EsbuildCompiler struct{}