diff --git a/pkg/agent/commands.go b/pkg/agent/commands.go
index bcbcad4..96a4f1f 100644
--- a/pkg/agent/commands.go
+++ b/pkg/agent/commands.go
@@ -186,7 +186,6 @@ func (s *agent) handleCommand(ctx context.Context, input string, handler EventHa
 			s.cfg.Tools = env.tools
 			s.cfg.Exec = env.exec
 			s.cfg.GenerationParams = env.genParams
-			s.agentPrompt = env.agentPrompt
 			s.agentName = name
 			s.session = nil
 			s.sessionID = NewSessionID()
diff --git a/pkg/agent/core.go b/pkg/agent/core.go
index a555dac..9b986d5 100644
--- a/pkg/agent/core.go
+++ b/pkg/agent/core.go
@@ -9,7 +9,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"runtime"
 	"runtime/debug"
 	"slices"
 	"strconv"
@@ -32,7 +31,6 @@ type AgentEnv struct {
 	exec         toolExecutor
 	Hooks        Hooks
 	preamble string
-	agentPrompt  string // agent-specific suffix appended after the base system prompt
 	genParams    backend.GenerationParams
 	Messages     []string
 }
@@ -57,14 +55,14 @@ func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv
 	allTools := toolInfosToBackend(allToolInfos)
 
 	hooks := Hooks{}
-	agentPrompt := ""
+	var preamble string
 	var genParams backend.GenerationParams
 	if cfg != nil {
 		for k, v := range cfg.Hooks {
 			hooks[k] = []string(v)
 		}
 		if resolved, err := resolvePrompt(cfg.Prompt, cwd); err == nil {
-			agentPrompt = resolved
+			preamble = resolved
 		}
 		genParams = backend.GenerationParams{
 			MaxTokens:        cfg.MaxTokens,
@@ -81,13 +79,6 @@ func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv
 		}
 	}
 
-	path := DefaultPromptsDir() + "/SYSTEM_PROMPT.md"
-	data, err := os.ReadFile(path)
-	if err != nil {
-		panic(fmt.Sprintf("loadSystemPrompt: %s: %v", path, err))
-	}
-	preamble := expandSystemPrompt(string(data), cwd)
-
 	exec := func(ctx context.Context, name string, args json.RawMessage) (string, error) {
 		server, ok := serverOf[name]
 		if !ok {
@@ -110,7 +101,6 @@ func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv
 		exec:        exec,
 		Hooks:       hooks,
 		preamble:    preamble,
-		agentPrompt: agentPrompt,
 		genParams:    genParams,
 		Messages:     messages,
 	}
@@ -122,31 +112,6 @@ func DefaultPromptsDir() string {
 	return paths.CfgDir() + "/prompts"
 }
 
-func expandSystemPrompt(content, cwd string) string {
-	if cwd == "" {
-		cwd, _ = os.Getwd()
-	}
-	isGit := "false"
-	if _, err := os.Stat(filepath.Join(cwd, ".git")); err == nil {
-		isGit = "true"
-	}
-	mapper := func(key string) string {
-		switch key {
-		case "PWD":
-			return cwd
-		case "PRIME_DATE":
-			return time.Now().Format("2006-01-02")
-		case "PRIME_PLATFORM":
-			return strings.ToLower(runtime.GOOS)
-		case "PRIME_IS_GIT_REPO":
-			return isGit
-		default:
-			return os.Getenv(key)
-		}
-	}
-	return os.Expand(content, mapper)
-}
-
 
 // AgentConfigPath resolves the config file path for a named agent.
 func AgentConfigPath(agentsDir, name string) string {
@@ -204,7 +169,6 @@ type agent struct {
 	newDispatcher   func() tools.Dispatcher
 	newBackend      func(string) (backend.Backend, error)
 	cwd             string
-	agentPrompt      string // agent-specific prompt suffix; kept for system prompt rebuilds
 	startupMessages  []string
 	currentAction   atomic.Pointer[actionHandle]
 	fifo            PromptFIFO
@@ -318,7 +282,6 @@ func NewAgentCore(cfg AgentCoreConfig) Core {
 		sessionsDir:     cfg.SessionsDir,
 		sessionID:       cfg.SessionID,
 		cwd:             paths.ExpandHome(cfg.CWD),
-		agentPrompt:     cfg.Env.agentPrompt,
 		startupMessages: cfg.Env.Messages,
 		dispatcher:      cfg.Env.dispatcher,
 		newDispatcher:   cfg.NewDispatcher,
@@ -512,9 +475,6 @@ func (s *agent) spawnContext(ctx context.Context, handler EventHandler) string {
 		handler(infoEvent(result.Warning))
 	}
 	var parts []string
-	if s.agentPrompt != "" {
-		parts = append(parts, s.agentPrompt)
-	}
 	if result.Context != "" {
 		parts = append(parts, result.Context)
 	}
diff --git a/pkg/agent/core_test.go b/pkg/agent/core_test.go
index 5c828b3..a62d55c 100644
--- a/pkg/agent/core_test.go
+++ b/pkg/agent/core_test.go
@@ -526,45 +526,6 @@ func TestAgentSpawnFiresOnce(t *testing.T) {
 	}
 }
 
-// --- expandSystemPrompt ---
-
-func TestExpandSystemPrompt_IsGitTrue(t *testing.T) {
-	dir := t.TempDir()
-	os.Mkdir(filepath.Join(dir, ".git"), 0700)
-	got := expandSystemPrompt("${PRIME_IS_GIT_REPO}", dir)
-	if got != "true" {
-		t.Errorf("got %q; want true", got)
-	}
-}
-
-func TestExpandSystemPrompt_IsGitFalse(t *testing.T) {
-	got := expandSystemPrompt("${PRIME_IS_GIT_REPO}", t.TempDir())
-	if got != "false" {
-		t.Errorf("got %q; want false", got)
-	}
-}
-
-func TestExpandSystemPrompt_PWDUsesCWD(t *testing.T) {
-	dir := t.TempDir()
-	got := expandSystemPrompt("${PWD}", dir)
-	if got != dir {
-		t.Errorf("got %q; want %q", got, dir)
-	}
-}
-
-// --- BuildAgentEnv: missing system prompt ---
-
-func TestBuildAgentEnv_MissingSystemPrompt(t *testing.T) {
-	t.Setenv("OLLIE_CFG_PATH", t.TempDir()) // no SYSTEM_PROMPT.md written
-
-	defer func() {
-		if recover() == nil {
-			t.Error("expected panic from BuildAgentEnv; got none")
-		}
-	}()
-	BuildAgentEnv(nil, tools.NewDispatcher(), "")
-}
-
 // --- panic recovery ---
 
 func TestSubmit_PanicRecovery(t *testing.T) {
@@ -2237,26 +2198,20 @@ func TestFirstSentence_ShortNoSentenceEnd(t *testing.T) {
 
 // --- BuildAgentEnv (nil config path) ---
 
-func setupCfgDir(t *testing.T, preamble string) string {
+func setupCfgDir(t *testing.T) string {
 	t.Helper()
 	dir := t.TempDir()
-	if err := os.MkdirAll(dir+"/prompts", 0700); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(dir+"/prompts/SYSTEM_PROMPT.md", []byte(preamble), 0600); err != nil {
-		t.Fatal(err)
-	}
 	t.Setenv("OLLIE_CFG_PATH", dir)
 	return dir
 }
 
 func TestBuildAgentEnv_NilConfig(t *testing.T) {
-	setupCfgDir(t, "base prompt")
+	setupCfgDir(t)
 	d := tools.NewDispatcher()
 	env := BuildAgentEnv(nil, d, t.TempDir())
 
-	if env.preamble != "base prompt" {
-		t.Errorf("preamble = %q; want %q", env.preamble, "base prompt")
+	if env.preamble != "" {
+		t.Errorf("preamble = %q; want empty", env.preamble)
 	}
 	if len(env.Hooks) != 0 {
 		t.Errorf("expected no hooks; got %v", env.Hooks)
@@ -2269,23 +2224,19 @@ func TestBuildAgentEnv_NilConfig(t *testing.T) {
 	}
 }
 
-func TestBuildAgentEnv_AgentPromptAppended(t *testing.T) {
-	setupCfgDir(t, "base prompt")
+func TestBuildAgentEnv_PromptBecomesPreamble(t *testing.T) {
+	setupCfgDir(t)
 	d := tools.NewDispatcher()
-	cfg := &config.Config{Prompt: config.Prompt{Value: []string{"agent suffix"}}}
+	cfg := &config.Config{Prompt: config.Prompt{Value: []string{"the prompt"}}}
 	env := BuildAgentEnv(cfg, d, t.TempDir())
 
-	// preamble contains only the system prompt; agent prompt is kept separate
-	if !strings.Contains(env.preamble, "base prompt") {
-		t.Errorf("preamble missing base: %q", env.preamble)
-	}
-	if env.agentPrompt != "agent suffix" {
-		t.Errorf("agentPrompt = %q; want %q", env.agentPrompt, "agent suffix")
+	if env.preamble != "the prompt" {
+		t.Errorf("preamble = %q; want %q", env.preamble, "the prompt")
 	}
 }
 
 func TestBuildAgentEnv_HooksAndParams(t *testing.T) {
-	setupCfgDir(t, "base")
+	setupCfgDir(t)
 	d := tools.NewDispatcher()
 	temp := 0.7
 	cfg := &config.Config{
@@ -2307,7 +2258,7 @@ func TestBuildAgentEnv_HooksAndParams(t *testing.T) {
 }
 
 func TestBuildAgentEnv_ExecUnknownTool(t *testing.T) {
-	setupCfgDir(t, "base")
+	setupCfgDir(t)
 	d := tools.NewDispatcher()
 	env := BuildAgentEnv(nil, d, t.TempDir())
 
@@ -2360,7 +2311,7 @@ func (m *mockTrustedSetter) CallTool(ctx context.Context, tool string, args json
 }
 
 func TestBuildAgentEnv_ListToolsError(t *testing.T) {
-	setupCfgDir(t, "")
+	setupCfgDir(t)
 	d := &mockDispatcher{listErr: fmt.Errorf("boom")}
 	env := BuildAgentEnv(nil, d, t.TempDir())
 	if len(env.Messages) != 1 || !strings.Contains(env.Messages[0], "boom") {
@@ -2369,7 +2320,7 @@ func TestBuildAgentEnv_ListToolsError(t *testing.T) {
 }
 
 func TestBuildAgentEnv_ToolsPopulated(t *testing.T) {
-	setupCfgDir(t, "")
+	setupCfgDir(t)
 	d := &mockDispatcher{
 		tools: []tools.ToolInfo{{Server: "s1", Name: "mytool", Description: "desc", InputSchema: json.RawMessage(`{}`)}},
 	}
@@ -2380,7 +2331,7 @@ func TestBuildAgentEnv_ToolsPopulated(t *testing.T) {
 }
 
 func TestBuildAgentEnv_TrustedTools(t *testing.T) {
-	setupCfgDir(t, "")
+	setupCfgDir(t)
 	setter := &mockTrustedSetter{}
 	d := &mockDispatcher{servers: map[string]tools.Server{"execute": setter}}
 	cfg := &config.Config{TrustedTools: []string{"bash"}}
@@ -2390,19 +2341,18 @@ func TestBuildAgentEnv_TrustedTools(t *testing.T) {
 	}
 }
 
-func TestBuildAgentEnv_AgentPromptNoSystemPrompt(t *testing.T) {
-	// Empty system prompt file — agentPrompt is kept separate from preamble.
-	setupCfgDir(t, "")
+func TestBuildAgentEnv_PromptOnly(t *testing.T) {
+	setupCfgDir(t)
 	d := tools.NewDispatcher()
 	cfg := &config.Config{Prompt: config.Prompt{Value: []string{"only agent"}}}
 	env := BuildAgentEnv(cfg, d, t.TempDir())
-	if env.agentPrompt != "only agent" {
-		t.Errorf("agentPrompt = %q; want %q", env.agentPrompt, "only agent")
+	if env.preamble != "only agent" {
+		t.Errorf("preamble = %q; want %q", env.preamble, "only agent")
 	}
 }
 
 func TestBuildAgentEnv_ExecDispatchSuccess(t *testing.T) {
-	setupCfgDir(t, "")
+	setupCfgDir(t)
 	d := &mockDispatcher{
 		tools: []tools.ToolInfo{{Server: "s1", Name: "mytool"}},
 		dispatch: func(ctx context.Context, server, tool string, args json.RawMessage) (json.RawMessage, error) {
@@ -2420,7 +2370,7 @@ func TestBuildAgentEnv_ExecDispatchSuccess(t *testing.T) {
 }
 
 func TestBuildAgentEnv_ExecDispatchError(t *testing.T) {
-	setupCfgDir(t, "")
+	setupCfgDir(t)
 	d := &mockDispatcher{
 		tools: []tools.ToolInfo{{Server: "s1", Name: "mytool"}},
 		dispatch: func(ctx context.Context, server, tool string, args json.RawMessage) (json.RawMessage, error) {
@@ -2435,7 +2385,7 @@ func TestBuildAgentEnv_ExecDispatchError(t *testing.T) {
 }
 
 func TestBuildAgentEnv_ExecToolResultIsError(t *testing.T) {
-	setupCfgDir(t, "")
+	setupCfgDir(t)
 	d := &mockDispatcher{
 		tools: []tools.ToolInfo{{Server: "s1", Name: "mytool"}},
 		dispatch: func(ctx context.Context, server, tool string, args json.RawMessage) (json.RawMessage, error) {