diff --git a/schala-lang/language/src/lib.rs b/schala-lang/language/src/lib.rs
index d44815a..4cda23d 100644
--- a/schala-lang/language/src/lib.rs
+++ b/schala-lang/language/src/lib.rs
@@ -23,7 +23,7 @@ use std::cell::RefCell;
 use std::rc::Rc;
 
 use itertools::Itertools;
-use schala_repl::{ProgrammingLanguageInterface, EvalOptions, TraceArtifact, UnfinishedComputation, FinishedComputation, ComputationRequest, ComputationResponse, GlobalOutputStats};
+use schala_repl::{ProgrammingLanguageInterface, EvalOptions, ComputationRequest, ComputationResponse, GlobalOutputStats};
 
 macro_rules! bx {
   ($e:expr) => { Box::new($e) }
@@ -42,15 +42,6 @@ mod builtin;
 mod reduced_ast;
 mod eval;
 
-//trace_macros!(true);
-/*
-#[derive(ProgrammingLanguageInterface)]
-#[LanguageName = "Schala"]
-#[SourceFileExtension = "schala"]
-#[PipelineSteps(load_source, tokenizing, parsing(compact,expanded,trace), symbol_table, typechecking, ast_reducing, eval)]
-#[DocMethod = "get_doc"]
-#[HandleCustomInterpreterDirectives = "handle_custom_interpreter_directives"]
-*/
 /// All bits of state necessary to parse and execute a Schala program are stored in this struct.
 /// `state` represents the execution state for the AST-walking interpreter, the other fields
 /// should be self-explanatory.
@@ -90,21 +81,23 @@ impl Schala {
   pub fn new() -> Schala {
     let prelude = include_str!("prelude.schala");
     let mut s = Schala::new_blank_env();
-    s.execute_pipeline(prelude, &EvalOptions::default());
+
+    let request = ComputationRequest { source: prelude.to_string(), debug_requests: vec![] };
+    s.run_computation(request);
     s
   }
 }
 
-fn load_source<'a>(input: &'a str, handle: &mut Schala, _comp: Option<&mut UnfinishedComputation>) -> Result<&'a str, String> {
+fn load_source<'a>(input: &'a str, handle: &mut Schala) -> Result<&'a str, String> {
   handle.source_reference.load_new_source(input);
   Ok(input)
 }
 
-fn tokenizing(input: &str, _handle: &mut Schala, comp: Option<&mut UnfinishedComputation>) -> Result<Vec<tokenizing::Token>, String> {
+fn tokenizing(input: &str, _handle: &mut Schala, comp: Option<&mut PassDebugArtifact>) -> Result<Vec<tokenizing::Token>, String> {
   let tokens = tokenizing::tokenize(input);
   comp.map(|comp| {
     let token_string = tokens.iter().map(|t| t.to_string_with_metadata()).join(", ");
-    comp.add_artifact(TraceArtifact::new("tokens", token_string));
+    comp.add_artifact(token_string);
   });
 
   let errors: Vec<String> = tokens.iter().filter_map(|t| t.get_error()).collect();
@@ -115,7 +108,7 @@ fn tokenizing(input: &str, _handle: &mut Schala, comp: Option<&mut UnfinishedCom
   }
 }
 
-fn parsing(input: Vec<tokenizing::Token>, handle: &mut Schala, comp: Option<&mut UnfinishedComputation>) -> Result<ast::AST, String> {
+fn parsing(input: Vec<tokenizing::Token>, handle: &mut Schala, comp: Option<&mut PassDebugArtifact>) -> Result<ast::AST, String> {
   use crate::parsing::Parser;
 
   let mut parser = match handle.active_parser.take() {
@@ -127,6 +120,7 @@ fn parsing(input: Vec<tokenizing::Token>, handle: &mut Schala, comp: Option<&mut
   let trace = parser.format_parse_trace();
 
   comp.map(|comp| {
+    /*
     //TODO need to control which of these debug stages get added
     let opt = comp.cur_debug_options.get(0).map(|s| s.clone());
     match opt {
@@ -136,6 +130,7 @@ fn parsing(input: Vec<tokenizing::Token>, handle: &mut Schala, comp: Option<&mut
       Some(ref s) if s == "trace" => comp.add_artifact(TraceArtifact::new_parse_trace(trace)),
       Some(ref x) => println!("Bad parsing debug option: {}", x),
     };
+    */
   });
   ast.map_err(|err| format_parse_error(err, handle))
 }
@@ -157,41 +152,40 @@ fn format_parse_error(error: parsing::ParseError, handle: &mut Schala) -> String
 "#, line_from_program, location_pointer, error_msg=error.msg, space_padding=space_padding, line_num=line_num)
 }
 
-fn symbol_table(input: ast::AST, handle: &mut Schala, comp: Option<&mut UnfinishedComputation>) -> Result<ast::AST, String> {
+fn symbol_table(input: ast::AST, handle: &mut Schala, comp: Option<&mut PassDebugArtifact>) -> Result<ast::AST, String> {
   let add = handle.symbol_table.borrow_mut().add_top_level_symbols(&input);
   match add {
     Ok(()) => {
-      let artifact = TraceArtifact::new("symbol_table", handle.symbol_table.borrow().debug_symbol_table());
-      comp.map(|comp| comp.add_artifact(artifact));
+      let debug = handle.symbol_table.borrow().debug_symbol_table();
+      comp.map(|comp| comp.add_artifact(debug));
       Ok(input)
     },
     Err(msg) => Err(msg)
   }
 }
 
-fn typechecking(input: ast::AST, handle: &mut Schala, comp: Option<&mut UnfinishedComputation>) -> Result<ast::AST, String> {
+fn typechecking(input: ast::AST, handle: &mut Schala, comp: Option<&mut PassDebugArtifact>) -> Result<ast::AST, String> {
   let result = handle.type_context.typecheck(&input);
 
   comp.map(|comp| {
-    let artifact = TraceArtifact::new("type", match result {
+    comp.add_artifact(match result {
       Ok(ty) => ty.to_string(),
       Err(err) => format!("Type error: {}", err.msg)
     });
-    comp.add_artifact(artifact);
   });
 
   Ok(input)
 }
 
-fn ast_reducing(input: ast::AST, handle: &mut Schala, comp: Option<&mut UnfinishedComputation>) -> Result<reduced_ast::ReducedAST, String> {
+fn ast_reducing(input: ast::AST, handle: &mut Schala, comp: Option<&mut PassDebugArtifact>) -> Result<reduced_ast::ReducedAST, String> {
   let ref symbol_table = handle.symbol_table.borrow();
   let output = input.reduce(symbol_table);
-  comp.map(|comp| comp.add_artifact(TraceArtifact::new("ast_reducing", format!("{:?}", output))));
+  comp.map(|comp| comp.add_artifact(format!("{:?}", output)));
   Ok(output)
 }
 
-fn eval(input: reduced_ast::ReducedAST, handle: &mut Schala, comp: Option<&mut UnfinishedComputation>) -> Result<String, String> {
-  comp.map(|comp| comp.add_artifact(TraceArtifact::new("value_state", handle.state.debug_print())));
+fn eval(input: reduced_ast::ReducedAST, handle: &mut Schala, comp: Option<&mut PassDebugArtifact>) -> Result<String, String> {
+  comp.map(|comp| comp.add_artifact(handle.state.debug_print()));
   let evaluation_outputs = handle.state.evaluate(input, true);
   let text_output: Result<Vec<String>, String> = evaluation_outputs
     .into_iter()
@@ -221,6 +215,15 @@ impl SourceReference {
   }
 }
 
+struct PassDebugArtifact {
+  artifact: Option<String>
+}
+impl PassDebugArtifact {
+  fn add_artifact(&mut self, artifact: String) {
+    self.artifact = Some(artifact)
+  }
+}
+
 impl ProgrammingLanguageInterface for Schala {
   fn get_language_name(&self) -> String { format!("Schala") }
   fn get_source_file_suffix(&self) -> String { format!("schala") }
@@ -228,13 +231,20 @@ impl ProgrammingLanguageInterface for Schala {
   fn run_computation(&mut self, request: ComputationRequest) -> ComputationResponse {
     let ComputationRequest { source, debug_requests } = request;
 
-    load_source(&source, self, None);
-    let main_output: Result<String, String> = tokenizing(&source, self, None)
-      .and_then(|tokens| parsing(tokens, self, None))
-      .and_then(|ast| symbol_table(ast, self, None))
-      .and_then(|ast| typechecking(ast, self, None))
-      .and_then(|ast| ast_reducing(ast, self, None))
-      .and_then(|reduced_ast| eval(reduced_ast, self, None));
+    let mut token_debug_artifact = None;
+    let mut parsing_debug_artifact = None;
+    let mut symbol_debug_artifact = None;
+    let mut typechecking_debug_artifact = None;
+    let mut reducing_debug_artifact = None;
+    let mut eval_debug_artifact = None;
+
+    load_source(&source, self);
+    let main_output: Result<String, String> = tokenizing(&source, self, token_debug_artifact)
+      .and_then(|tokens| parsing(tokens, self, parsing_debug_artifact))
+      .and_then(|ast| symbol_table(ast, self, symbol_debug_artifact))
+      .and_then(|ast| typechecking(ast, self, typechecking_debug_artifact))
+      .and_then(|ast| ast_reducing(ast, self, reducing_debug_artifact))
+      .and_then(|reduced_ast| eval(reduced_ast, self, eval_debug_artifact));
 
     ComputationResponse {
       main_output,
diff --git a/schala-repl/src/language.rs b/schala-repl/src/language.rs
index d7bad6a..203eaa8 100644
--- a/schala-repl/src/language.rs
+++ b/schala-repl/src/language.rs
@@ -189,6 +189,7 @@ pub trait ProgrammingLanguageInterface {
   }
 }
 
+//TODO source can probably be a &str
 pub struct ComputationRequest {
   pub source: String,
   pub debug_requests: Vec<DebugRequest>,