diff --git a/internal/service/application_service_test.go b/internal/service/application_service_test.go
index 9683a87..ae0a080 100644
--- a/internal/service/application_service_test.go
+++ b/internal/service/application_service_test.go
@@ -104,6 +104,89 @@ func TestValidateParams_BooleanValues(t *testing.T) {
 	}
 }
 
+func TestValidateParams_FileTypeValid(t *testing.T) {
+	params := []model.ParameterSchema{
+		{Name: "MODEL", Type: model.ParamTypeFile, Required: true},
+	}
+	values := map[string]string{"MODEL": "12345"}
+	if err := ValidateParams(params, values); err != nil {
+		t.Errorf("expected no error for valid file ID, got %v", err)
+	}
+}
+
+func TestValidateParams_FileTypeInvalid(t *testing.T) {
+	params := []model.ParameterSchema{
+		{Name: "MODEL", Type: model.ParamTypeFile, Required: true},
+	}
+	values := map[string]string{"MODEL": "not_a_number"}
+	err := ValidateParams(params, values)
+	if err == nil {
+		t.Fatal("expected error for non-numeric file ID")
+	}
+	if !strings.Contains(err.Error(), "file ID") {
+		t.Errorf("error should mention 'file ID', got: %v", err)
+	}
+}
+
+func TestValidateParams_DirectoryTypeValid(t *testing.T) {
+	params := []model.ParameterSchema{
+		{Name: "DATA_DIR", Type: model.ParamTypeDirectory, Required: true},
+	}
+	values := map[string]string{"DATA_DIR": "99"}
+	if err := ValidateParams(params, values); err != nil {
+		t.Errorf("expected no error for valid directory ID, got %v", err)
+	}
+}
+
+func TestValidateParams_DirectoryTypeInvalid(t *testing.T) {
+	params := []model.ParameterSchema{
+		{Name: "DATA_DIR", Type: model.ParamTypeDirectory, Required: true},
+	}
+	values := map[string]string{"DATA_DIR": "abc"}
+	err := ValidateParams(params, values)
+	if err == nil {
+		t.Fatal("expected error for non-numeric directory ID")
+	}
+	if !strings.Contains(err.Error(), "file ID") {
+		t.Errorf("error should mention 'file ID', got: %v", err)
+	}
+}
+
+func TestRenderScript_FileTypeNotEscaped(t *testing.T) {
+	params := []model.ParameterSchema{{Name: "MODEL_PATH", Type: model.ParamTypeFile}}
+	values := map[string]string{"MODEL_PATH": "model_v2.bin"}
+	result := RenderScript("python train.py --model $MODEL_PATH", params, values)
+	expected := "python train.py --model model_v2.bin"
+	if result != expected {
+		t.Errorf("got %q, want %q", result, expected)
+	}
+}
+
+func TestRenderScript_WorkDirInjected(t *testing.T) {
+	params := []model.ParameterSchema{{Name: "INPUT", Type: model.ParamTypeString}}
+	values := map[string]string{
+		"INPUT":    "data.txt",
+		"WORK_DIR": "/data/work/myapp_20260101_abcd",
+	}
+	result := RenderScript("#SBATCH --chdir=$WORK_DIR\necho $INPUT", params, values)
+	if !strings.Contains(result, "#SBATCH --chdir=/data/work/myapp_20260101_abcd") {
+		t.Errorf("WORK_DIR should be replaced raw, got: %s", result)
+	}
+	if !strings.Contains(result, "'data.txt'") {
+		t.Errorf("INPUT should still be shell-escaped, got: %s", result)
+	}
+}
+
+func TestRenderScript_DirectoryTypeNotEscaped(t *testing.T) {
+	params := []model.ParameterSchema{{Name: "DATA_DIR", Type: model.ParamTypeDirectory}}
+	values := map[string]string{"DATA_DIR": "input_folder"}
+	result := RenderScript("ls $DATA_DIR", params, values)
+	expected := "ls input_folder"
+	if result != expected {
+		t.Errorf("got %q, want %q", result, expected)
+	}
+}
+
 func TestRenderScript_SimpleReplacement(t *testing.T) {
 	params := []model.ParameterSchema{{Name: "INPUT", Type: model.ParamTypeString}}
 	values := map[string]string{"INPUT": "data.txt"}
diff --git a/internal/service/task_service_test.go b/internal/service/task_service_test.go
index d87c70b..6360aa7 100644
--- a/internal/service/task_service_test.go
+++ b/internal/service/task_service_test.go
@@ -3,6 +3,7 @@ package service
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"os"
@@ -536,3 +537,139 @@ func TestTaskService_ProcessTask_ValidateParams_ValidParamsSucceed(t *testing.T)
 		t.Errorf("SlurmJobID = %v, want 99", updated.SlurmJobID)
 	}
 }
+
+func TestTaskService_ProcessTask_FileParamResolution(t *testing.T) {
+	jobID := int32(88)
+	env := newTaskTestEnv(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewEncoder(w).Encode(slurm.OpenapiJobSubmitResponse{
+			Result: &slurm.JobSubmitResponseMsg{JobID: &jobID},
+		})
+	}))
+	defer env.close()
+
+	ctx := context.Background()
+
+	blob := &model.FileBlob{SHA256: "deadbeef", MinioKey: "test/file.bin", FileSize: 1024}
+	if err := env.db.Create(blob).Error; err != nil {
+		t.Fatalf("create blob: %v", err)
+	}
+	file := &model.File{Name: "model_weights.bin", BlobSHA256: blob.SHA256}
+	if err := env.fileStore.Create(ctx, file); err != nil {
+		t.Fatalf("create file: %v", err)
+	}
+
+	appID := env.createApp(t, "file-param-app",
+		"#!/bin/bash\n#SBATCH --chdir=$WORK_DIR\npython train.py --model $MODEL_PATH",
+		json.RawMessage(`[{"name":"MODEL_PATH","type":"file","required":true}]`))
+
+	// No InputFileIDs because stagingSvc is nil in tests; file is still resolvable via fileStore.
+	task, err := env.svc.CreateTask(ctx, &model.CreateTaskRequest{
+		AppID:  appID,
+		Values: map[string]string{"MODEL_PATH": fmt.Sprintf("%d", file.ID)},
+	})
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+
+	err = env.svc.ProcessTask(ctx, task.ID)
+	if err != nil {
+		t.Fatalf("ProcessTask with file param: %v", err)
+	}
+
+	updated, _ := env.taskStore.GetByID(ctx, task.ID)
+	if updated.Status != model.TaskStatusQueued {
+		t.Errorf("Status = %q, want %q", updated.Status, model.TaskStatusQueued)
+	}
+}
+
+func TestTaskService_ProcessTask_WorkDirInScript(t *testing.T) {
+	jobID := int32(77)
+	env := newTaskTestEnv(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewEncoder(w).Encode(slurm.OpenapiJobSubmitResponse{
+			Result: &slurm.JobSubmitResponseMsg{JobID: &jobID},
+		})
+	}))
+	defer env.close()
+
+	appID := env.createApp(t, "workdir-app",
+		"#!/bin/bash\n#SBATCH --chdir=$WORK_DIR\necho hello",
+		json.RawMessage(`[]`))
+
+	task, err := env.svc.CreateTask(context.Background(), &model.CreateTaskRequest{
+		AppID:  appID,
+		Values: map[string]string{},
+	})
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+
+	err = env.svc.ProcessTask(context.Background(), task.ID)
+	if err != nil {
+		t.Fatalf("ProcessTask: %v", err)
+	}
+
+	updated, _ := env.taskStore.GetByID(context.Background(), task.ID)
+	if updated.WorkDir == "" {
+		t.Fatal("WorkDir should be set")
+	}
+}
+
+func TestTaskService_ProcessTask_FileParamInvalidID(t *testing.T) {
+	jobID := int32(42)
+	env := newTaskTestEnv(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewEncoder(w).Encode(slurm.OpenapiJobSubmitResponse{
+			Result: &slurm.JobSubmitResponseMsg{JobID: &jobID},
+		})
+	}))
+	defer env.close()
+
+	appID := env.createApp(t, "bad-file-app",
+		"#!/bin/bash\npython train.py --model $MODEL",
+		json.RawMessage(`[{"name":"MODEL","type":"file","required":true}]`))
+
+	task, err := env.svc.CreateTask(context.Background(), &model.CreateTaskRequest{
+		AppID:  appID,
+		Values: map[string]string{"MODEL": "not_a_number"},
+	})
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+
+	err = env.svc.ProcessTask(context.Background(), task.ID)
+	if err == nil {
+		t.Fatal("expected error for non-numeric file ID in file-type param")
+	}
+	if !strings.Contains(err.Error(), "file ID") {
+		t.Errorf("error should mention 'file ID', got: %v", err)
+	}
+}
+
+func TestTaskService_ProcessTask_FileParamNotInInputFiles(t *testing.T) {
+	jobID := int32(42)
+	env := newTaskTestEnv(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewEncoder(w).Encode(slurm.OpenapiJobSubmitResponse{
+			Result: &slurm.JobSubmitResponseMsg{JobID: &jobID},
+		})
+	}))
+	defer env.close()
+
+	appID := env.createApp(t, "missing-file-app",
+		"#!/bin/bash\npython train.py --model $MODEL",
+		json.RawMessage(`[{"name":"MODEL","type":"file","required":true}]`))
+
+	task, err := env.svc.CreateTask(context.Background(), &model.CreateTaskRequest{
+		AppID:  appID,
+		Values: map[string]string{"MODEL": "999"},
+	})
+	if err != nil {
+		t.Fatalf("CreateTask: %v", err)
+	}
+
+	err = env.svc.ProcessTask(context.Background(), task.ID)
+	if err == nil {
+		t.Fatal("expected error for file_id not in input_file_ids")
+	}
+	if !strings.Contains(err.Error(), "not found") {
+		t.Errorf("error should mention 'not found', got: %v", err)
+	}
+}