diff --git a/pkg/agent/commands.go b/pkg/agent/commands.go
index f16ee47..3ad5f6e 100644
--- a/pkg/agent/commands.go
+++ b/pkg/agent/commands.go
@@ -206,7 +206,8 @@ func (s *agent) handleCommand(ctx context.Context, input string, handler EventHa
 				return
 			}
 			d := s.newDispatcher()
-			env := BuildAgentEnv(cfg, d, s.cwd)
+			newSessID := NewSessionID()
+			env := BuildAgentEnv(cfg, d, s.cwd, []string{"OLLIE_SESSION_ID=" + newSessID})
 			if env.Backend != "" {
 				newBe, err := s.newBackend(env.Backend)
 				if err != nil {
@@ -229,7 +230,7 @@ func (s *agent) handleCommand(ctx context.Context, input string, handler EventHa
 			s.cfg.MaxSteps = env.maxSteps
 			s.agentName = name
 			s.session = nil
-			s.sessionID = NewSessionID()
+			s.sessionID = newSessID
 			s.pushSessionEnv()
 			for _, msg := range env.Messages {
 				handler(infoEvent(msg))
diff --git a/pkg/agent/core.go b/pkg/agent/core.go
index f698694..9cb3a9c 100644
--- a/pkg/agent/core.go
+++ b/pkg/agent/core.go
@@ -47,8 +47,10 @@ type AgentEnv struct {
 // BuildAgentEnv constructs an AgentEnv from a pre-configured Dispatcher and
 // optional agent config. cwd sets the working directory reported in the
 // system prompt; if empty, the process working directory is used.
+// env provides additional environment variables injected into prompt resolution
+// subprocesses (e.g. OLLIE_SESSION_ID=xxx).
 // The caller is responsible for registering all servers on d before calling this.
-func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv {
+func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string, env []string) AgentEnv {
 	var messages []string
 
 	var allToolInfos []tools.ToolInfo
@@ -75,7 +77,7 @@ func BuildAgentEnv(cfg *config.Config, d tools.Dispatcher, cwd string) AgentEnv
 		for k, v := range cfg.Hooks {
 			hooks[k] = []string(v)
 		}
-		if resolved, err := resolvePrompt(cfg.Prompt, cwd); err != nil {
+		if resolved, err := resolvePrompt(cfg.Prompt, cwd, env); err != nil {
 			fmt.Fprintf(os.Stderr, "resolve prompt: %v\n", err)
 		} else {
 			preamble = resolved
diff --git a/pkg/agent/core_test.go b/pkg/agent/core_test.go
index 984306b..21b7ff2 100644
--- a/pkg/agent/core_test.go
+++ b/pkg/agent/core_test.go
@@ -2226,7 +2226,7 @@ func setupCfgDir(t *testing.T) string {
 func TestBuildAgentEnv_NilConfig(t *testing.T) {
 	setupCfgDir(t)
 	d := tools.NewDispatcher()
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 
 	if env.preamble != "" {
 		t.Errorf("preamble = %q; want empty", env.preamble)
@@ -2246,7 +2246,7 @@ func TestBuildAgentEnv_PromptBecomesPreamble(t *testing.T) {
 	setupCfgDir(t)
 	d := tools.NewDispatcher()
 	cfg := &config.Config{Prompt: config.Prompt{Value: []string{"the prompt"}}}
-	env := BuildAgentEnv(cfg, d, t.TempDir())
+	env := BuildAgentEnv(cfg, d, t.TempDir(), nil)
 
 	if env.preamble != "the prompt" {
 		t.Errorf("preamble = %q; want %q", env.preamble, "the prompt")
@@ -2262,7 +2262,7 @@ func TestBuildAgentEnv_HooksAndParams(t *testing.T) {
 		MaxTokens:   512,
 		Temperature: &temp,
 	}
-	env := BuildAgentEnv(cfg, d, t.TempDir())
+	env := BuildAgentEnv(cfg, d, t.TempDir(), nil)
 
 	if cmds := env.Hooks[HookPreTurn]; len(cmds) != 1 || cmds[0] != "echo hi" {
 		t.Errorf("Hooks[preTurn] = %v", cmds)
@@ -2278,7 +2278,7 @@ func TestBuildAgentEnv_HooksAndParams(t *testing.T) {
 func TestBuildAgentEnv_ExecUnknownTool(t *testing.T) {
 	setupCfgDir(t)
 	d := tools.NewDispatcher()
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 
 	_, err := env.exec(context.Background(), "no_such_tool", json.RawMessage(`{}`))
 	if err == nil || !strings.Contains(err.Error(), "unknown tool") {
@@ -2318,7 +2318,7 @@ func (m *mockDispatcher) Dispatch(ctx context.Context, server, tool string, args
 func TestBuildAgentEnv_ListToolsError(t *testing.T) {
 	setupCfgDir(t)
 	d := &mockDispatcher{listErr: fmt.Errorf("boom")}
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 	if len(env.Messages) != 1 || !strings.Contains(env.Messages[0], "boom") {
 		t.Errorf("Messages = %v", env.Messages)
 	}
@@ -2329,7 +2329,7 @@ func TestBuildAgentEnv_ToolsPopulated(t *testing.T) {
 	d := &mockDispatcher{
 		tools: []tools.ToolInfo{{Server: "s1", Name: "mytool", Description: "desc", InputSchema: json.RawMessage(`{}`)}},
 	}
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 	if len(env.tools) != 1 || env.tools[0].Name != "mytool" {
 		t.Errorf("tools = %+v", env.tools)
 	}
@@ -2342,7 +2342,7 @@ func TestBuildAgentEnv_ToolsDisabled(t *testing.T) {
 	}
 	f := false
 	cfg := &config.Config{Tools: &f}
-	env := BuildAgentEnv(cfg, d, t.TempDir())
+	env := BuildAgentEnv(cfg, d, t.TempDir(), nil)
 	if len(env.tools) != 0 {
 		t.Errorf("expected no tools when disabled; got %+v", env.tools)
 	}
@@ -2352,7 +2352,7 @@ 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())
+	env := BuildAgentEnv(cfg, d, t.TempDir(), nil)
 	if env.preamble != "only agent" {
 		t.Errorf("preamble = %q; want %q", env.preamble, "only agent")
 	}
@@ -2365,7 +2365,7 @@ func TestBuildAgentEnv_ExecPrompt(t *testing.T) {
 		Value:  []string{"echo hello", "echo 'You are a security auditor.'", "echo world"},
 		IsExec: true,
 	}}
-	env := BuildAgentEnv(cfg, d, t.TempDir())
+	env := BuildAgentEnv(cfg, d, t.TempDir(), nil)
 	want := "hello\nYou are a security auditor.\nworld"
 	if env.preamble != want {
 		t.Errorf("preamble = %q; want %q", env.preamble, want)
@@ -2380,7 +2380,7 @@ func TestBuildAgentEnv_ExecDispatchSuccess(t *testing.T) {
 			return json.RawMessage(`{"content":[{"type":"text","text":"ok"}]}`), nil
 		},
 	}
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 	result, err := env.exec(context.Background(), "mytool", json.RawMessage(`{}`))
 	if err != nil {
 		t.Fatal(err)
@@ -2398,7 +2398,7 @@ func TestBuildAgentEnv_ExecDispatchError(t *testing.T) {
 			return nil, fmt.Errorf("dispatch failed")
 		},
 	}
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 	_, err := env.exec(context.Background(), "mytool", json.RawMessage(`{}`))
 	if err == nil || !strings.Contains(err.Error(), "dispatch failed") {
 		t.Errorf("err = %v", err)
@@ -2413,7 +2413,7 @@ func TestBuildAgentEnv_ExecToolResultIsError(t *testing.T) {
 			return json.RawMessage(`{"isError":true,"content":[{"type":"text","text":"bad thing"}]}`), nil
 		},
 	}
-	env := BuildAgentEnv(nil, d, t.TempDir())
+	env := BuildAgentEnv(nil, d, t.TempDir(), nil)
 	_, err := env.exec(context.Background(), "mytool", json.RawMessage(`{}`))
 	if err == nil || !strings.Contains(err.Error(), "bad thing") {
 		t.Errorf("err = %v", err)
diff --git a/pkg/agent/prompt_resolver.go b/pkg/agent/prompt_resolver.go
index 990bfed..956900b 100644
--- a/pkg/agent/prompt_resolver.go
+++ b/pkg/agent/prompt_resolver.go
@@ -24,17 +24,17 @@ import (
 //   - If the string starts with '!', the rest is executed as a shell command.
 //   - If the expanded string names an existing file, the file is read.
 //   - Otherwise the string is used as-is.
-func resolvePrompt(p config.Prompt, cwd string) (string, error) {
+func resolvePrompt(p config.Prompt, cwd string, env []string) (string, error) {
 	if len(p.Value) == 0 {
 		return "", nil
 	}
 	if p.IsExec {
-		return resolveExecPrompt(p.Value, cwd)
+		return resolveExecPrompt(p.Value, cwd, env)
 	}
 	return resolveStringPrompt(p.Value[0], cwd)
 }
 
-func resolveExecPrompt(cmds []string, cwd string) (string, error) {
+func resolveExecPrompt(cmds []string, cwd string, env []string) (string, error) {
 	var parts []string
 	for _, cmdStr := range cmds {
 		cmdStr = strings.TrimSpace(cmdStr)
@@ -46,6 +46,9 @@ func resolveExecPrompt(cmds []string, cwd string) (string, error) {
 		if cwd != "" {
 			cmd.Dir = cwd
 		}
+		if len(env) > 0 {
+			cmd.Env = append(os.Environ(), env...)
+		}
 		var stdout, stderr bytes.Buffer
 		cmd.Stdout = &stdout
 		cmd.Stderr = &stderr