diff --git a/Pantograph.lean b/Pantograph.lean
index 42d46a7..4272001 100644
--- a/Pantograph.lean
+++ b/Pantograph.lean
@@ -45,7 +45,7 @@ def execute (command: Protocol.Command): MainM Lean.Json := do
   | "goal.continue" => run goal_continue
   | "goal.delete"   => run goal_delete
   | "goal.print"    => run goal_print
-  | "compile.tactics" => run compile_tactics
+  | "compile.unit"  => run compile_unit
   | cmd =>
     let error: Protocol.InteractionError :=
       errorCommand s!"Unknown command {cmd}"
@@ -192,11 +192,19 @@ def execute (command: Protocol.Command): MainM Lean.Json := do
     | .none => return .error $ errorIndex s!"Invalid state index {args.stateId}"
     | .some goalState => runMetaM <| do
       return .ok (← goalPrint goalState state.options)
-  compile_tactics (args: Protocol.CompileTactics): MainM (CR Protocol.CompileTacticsResult) := do
+  compile_unit (args: Protocol.CompileUnit): MainM (CR Protocol.CompileUnitResult) := do
     let module := args.module.toName
     try
-      let result ← Compile.compileAndCollectTacticInvocations module
-      return .ok result
+      let steps ← Compile.processSource module
+      let units? := if args.compilationUnits then
+          .some $ steps.map λ step => (step.src.startPos.byteIdx, step.src.stopPos.byteIdx)
+        else
+          .none
+      let invocations? ← if args.invocations then
+          pure $ .some (← Compile.collectTacticsFromCompilation steps)
+        else
+          pure .none
+      return .ok { units?, invocations? }
     catch e =>
       return .error $ errorI "compile" (← e.toMessageData.toString)
 
diff --git a/Pantograph/Compile.lean b/Pantograph/Compile.lean
index 7ac4d27..6d3f5d9 100644
--- a/Pantograph/Compile.lean
+++ b/Pantograph/Compile.lean
@@ -8,22 +8,23 @@ open Lean
 
 namespace Pantograph.Compile
 
-def compileAndCollectTacticInvocations (module : Name) : IO Protocol.CompileTacticsResult := do
-  let steps ← processSource module
+--def readCompilationUnits (module : Name) : IO Protocol.CompileUnitsResult := do
+--  let steps ← processSource module
+--  return { units := steps.map (·.src.toString) }
+def collectTacticsFromCompilation (steps : List CompilationStep) : IO (List Protocol.InvokedTactic) := do
   let infoTrees := steps.bind (·.trees)
   let tacticInfoTrees := infoTrees.bind λ tree => tree.filter λ
     | info@(.ofTacticInfo _) => info.isOriginal
     | _ => false
   let tactics := tacticInfoTrees.bind collectTactics
   IO.println s!"{steps.length} compilation steps, {infoTrees.length} trees found, {tacticInfoTrees.length} tactic trees, {tactics.length} tactics found"
-  let invocations : List Protocol.InvokedTactic ← tactics.mapM λ invocation => do
+  tactics.mapM λ invocation => do
     let goalBefore := (Format.joinSep (← invocation.goalState) "\n").pretty
     let goalAfter := (Format.joinSep (← invocation.goalStateAfter) "\n").pretty
     let tactic ← invocation.ctx.runMetaM {} do
       let t ← Lean.PrettyPrinter.ppTactic ⟨invocation.info.stx⟩
       return t.pretty
     return { goalBefore, goalAfter, tactic }
-  return { invocations }
 
 
 end Pantograph.Compile
diff --git a/Pantograph/Protocol.lean b/Pantograph/Protocol.lean
index 87c511a..8f4f947 100644
--- a/Pantograph/Protocol.lean
+++ b/Pantograph/Protocol.lean
@@ -275,17 +275,23 @@ structure GoalDiag where
   printAll: Bool := false
   instantiate: Bool := true
 
-structure CompileTactics where
-  module: String
-  deriving Lean.FromJson
 
+/-- Executes the Lean compiler on a single file -/
+structure CompileUnit where
+  module: String
+  -- If set to true, query the string boundaries of compilation units
+  compilationUnits: Bool := false
+  -- If set to true, collect tactic invocations
+  invocations: Bool := false
+  deriving Lean.FromJson
 structure InvokedTactic where
   goalBefore: String
   goalAfter: String
   tactic: String
   deriving Lean.ToJson
-structure CompileTacticsResult where
-  invocations: List InvokedTactic
+structure CompileUnitResult where
+  units?: Option $ List (Nat × Nat)
+  invocations?: Option $ List InvokedTactic
   deriving Lean.ToJson
 
 abbrev CR α := Except InteractionError α