diff --git a/protocol/job.go b/protocol/job.go
index 275f929..c43a9fd 100644
--- a/protocol/job.go
+++ b/protocol/job.go
@@ -44,6 +44,7 @@ type RunJobProgressReport struct {
 type RunJobExecutionInput struct {
 	WorkspaceScope       string                     `json:"workspaceScope,omitempty"`
 	Content              string                     `json:"content,omitempty"`
+	FileTargetKey        string                     `json:"fileTargetKey,omitempty"`
 	ExpectedVersion      int                        `json:"expectedVersion,omitempty"`
 	ExpectedChecksum     string                     `json:"expectedChecksum,omitempty"`
 	MaxReadBytes         int                        `json:"maxReadBytes,omitempty"`
diff --git a/protocol/job_validation.go b/protocol/job_validation.go
index 580ea04..e9b4fad 100644
--- a/protocol/job_validation.go
+++ b/protocol/job_validation.go
@@ -51,6 +51,9 @@ func ValidateRunJobAssignment(assignment RunJobAssignment) error {
 	if assignment.ExecutionInput.MaxReadBytes < 0 || assignment.ExecutionInput.MaxReadBytes > maxRunExecutionContentBytes {
 		return ValidationError("execution input maxReadBytes is out of bounds")
 	}
+	if assignment.ExecutionInput.FileTargetKey != "" && !ValidLogicalFileKey(assignment.ExecutionInput.FileTargetKey) {
+		return ValidationError("execution input fileTargetKey is not allowed")
+	}
 	if assignment.ExecutionInput.WorkspaceScope != "" && !ValidLogicalFileKey(assignment.ExecutionInput.WorkspaceScope) {
 		return ValidationError("execution input workspaceScope is not allowed")
 	}
diff --git a/protocol/job_validation_test.go b/protocol/job_validation_test.go
index c20a02a..205dc13 100644
--- a/protocol/job_validation_test.go
+++ b/protocol/job_validation_test.go
@@ -30,6 +30,15 @@ func TestValidateRunJobAssignmentScopedFilePayloads(t *testing.T) {
 	if err := ValidateRunJobAssignment(assignment); err == nil || !strings.Contains(err.Error(), "inputRef") {
 		t.Fatalf("expected raw credential ref rejection, got %v", err)
 	}
+	assignment.InputRef = "input://server-config/server-1/server.properties/v1"
+	assignment.ExecutionInput.FileTargetKey = "SCUM/Saved/Config/WindowsServer/ServerSettings.ini"
+	if err := ValidateRunJobAssignment(assignment); err != nil {
+		t.Fatalf("expected valid declared relative file target: %v", err)
+	}
+	assignment.ExecutionInput.FileTargetKey = "../outside.ini"
+	if err := ValidateRunJobAssignment(assignment); err == nil || !strings.Contains(err.Error(), "fileTargetKey") {
+		t.Fatalf("expected declared file target escape rejection, got %v", err)
+	}
 }
 
 func TestValidateRunJobAssignmentScopedReadDoesNotRequireInputRef(t *testing.T) {
diff --git a/runtime/execution_test.go b/runtime/execution_test.go
index 4aa2d7e..64320dc 100644
--- a/runtime/execution_test.go
+++ b/runtime/execution_test.go
@@ -704,6 +704,47 @@ func TestScopedFileExecutorBoundsReads(t *testing.T) {
 	}
 }
 
+func TestDeclaredFileTargetKeyReadsAndWritesRelativeToDeploymentRoot(t *testing.T) {
+	workspaceRoot := t.TempDir()
+	serverRoot := t.TempDir()
+	filePath := filepath.Join(serverRoot, "SCUM", "Saved", "Config", "WindowsServer", "ServerSettings.ini")
+	if err := os.MkdirAll(filepath.Dir(filePath), 0o700); err != nil {
+		t.Fatalf("mkdir declared file fixture: %v", err)
+	}
+	if err := os.WriteFile(filePath, []byte("[General]\nscum.MaxPlayers=63\n"), 0o600); err != nil {
+		t.Fatalf("write declared file fixture: %v", err)
+	}
+	executor, err := NewFileExecutor(workspaceRoot)
+	if err != nil {
+		t.Fatalf("new file executor: %v", err)
+	}
+	assignment := executionAssignment(protocol.RunCapabilityFilesRead)
+	assignment.TargetKey = "scum-server-settings"
+	assignment.ExecutionInput.FileTargetKey = "SCUM/Saved/Config/WindowsServer/ServerSettings.ini"
+	assignment.ExecutionInput.Deployment = &protocol.ServerDeploymentExecution{SchemaVersion: "1", Mode: "guided-install", ServerRoot: serverRoot, Revision: 1}
+	read := executor.Execute(context.Background(), assignment)
+	if read.State != lifecycleResultStateSucceeded || read.ExecutionResult.Kind != "file.read" || read.ExecutionResult.Content != "[General]\nscum.MaxPlayers=63\n" {
+		t.Fatalf("expected declared target read, got %+v", read)
+	}
+	assignment.Capability = protocol.RunCapabilityFilesWrite
+	assignment.InputRef = "input://server-execution/settings-write"
+	assignment.ExecutionInput.Content = "[General]\nscum.MaxPlayers=80\n"
+	assignment.ExecutionInput.ExpectedVersion = read.ExecutionResult.Version
+	assignment.ExecutionInput.ExpectedChecksum = read.ExecutionResult.Checksum
+	write := executor.Execute(context.Background(), assignment)
+	if write.State != lifecycleResultStateSucceeded || write.ExecutionResult.Kind != "file.write" {
+		t.Fatalf("expected declared target write, got %+v", write)
+	}
+	body, err := os.ReadFile(filePath)
+	if err != nil || string(body) != assignment.ExecutionInput.Content {
+		t.Fatalf("declared target write used the wrong path, body=%q err=%v", body, err)
+	}
+	assignment.ExecutionInput.FileTargetKey = "../outside.ini"
+	if unsafe := executor.Execute(context.Background(), assignment); unsafe.State != lifecycleResultStateFailed {
+		t.Fatalf("expected unsafe declared target rejection, got %+v", unsafe)
+	}
+}
+
 func TestScopedFileExecutorListsDirectories(t *testing.T) {
 	root := t.TempDir()
 	executor, err := NewFileExecutor(root)
diff --git a/runtime/file_execution.go b/runtime/file_execution.go
index 99b8db5..dd9c19d 100644
--- a/runtime/file_execution.go
+++ b/runtime/file_execution.go
@@ -106,8 +106,8 @@ func (executor *FileExecutor) existingReadTargetForAssignment(assignment protoco
 	if err != nil {
 		return "", "", false, err
 	}
-	targetKey := assignment.TargetKey
-	if deploymentRoot {
+	targetKey := fileTargetKeyForAssignment(assignment)
+	if deploymentRoot && assignment.ExecutionInput.FileTargetKey == "" {
 		targetKey = deploymentTargetKey(targetKey)
 		filePath, err := existingDeploymentTarget(scope, targetKey)
 		return scope, filePath, deploymentRoot, err
@@ -245,8 +245,8 @@ func (executor *FileExecutor) read(ctx context.Context, scope string, deployment
 	if err := ctx.Err(); err != nil {
 		return lifecycleExecutionFailure("file_cancelled", "file read cancelled", false)
 	}
-	targetKey := assignment.TargetKey
-	if deploymentRoot {
+	targetKey := fileTargetKeyForAssignment(assignment)
+	if deploymentRoot && assignment.ExecutionInput.FileTargetKey == "" {
 		targetKey = deploymentTargetKey(targetKey)
 	}
 	var filePath string
@@ -292,8 +292,8 @@ func (executor *FileExecutor) write(ctx context.Context, scope string, deploymen
 	if err := ctx.Err(); err != nil {
 		return lifecycleExecutionFailure("file_cancelled", "file write cancelled", false)
 	}
-	targetKey := assignment.TargetKey
-	if deploymentRoot {
+	targetKey := fileTargetKeyForAssignment(assignment)
+	if deploymentRoot && assignment.ExecutionInput.FileTargetKey == "" {
 		targetKey = deploymentTargetKey(targetKey)
 	}
 	var filePath string
@@ -365,6 +365,13 @@ func (executor *FileExecutor) write(ctx context.Context, scope string, deploymen
 	return LifecycleExecutionResult{State: lifecycleResultStateSucceeded, Progress: protocol.RunJobProgressReport{Percent: 100, Message: "file write completed"}, Message: "file write completed", ExecutionResult: protocol.RunJobExecutionResult{Kind: "file.write", Version: next.Version, Checksum: checksum, SizeBytes: int64(len(content)), Summary: "atomic compare-and-swap file write"}}
 }
 
+func fileTargetKeyForAssignment(assignment protocol.RunJobAssignment) string {
+	if targetKey := strings.TrimSpace(assignment.ExecutionInput.FileTargetKey); targetKey != "" {
+		return targetKey
+	}
+	return assignment.TargetKey
+}
+
 func deploymentTargetKey(value string) string {
 	cleaned := path.Clean(strings.TrimPrefix(strings.ReplaceAll(strings.TrimSpace(value), "\\", "/"), "/"))
 	if cleaned == "." || cleaned == "" {