diff --git a/engines/brainfuck/runtime.ts b/engines/brainfuck/runtime.ts
index 436f68c..fe6a8ba 100644
--- a/engines/brainfuck/runtime.ts
+++ b/engines/brainfuck/runtime.ts
@@ -85,7 +85,7 @@ export default class BrainfuckLanguageEngine implements LanguageEngine<BFRS> {
         // Add instruction to AST
         ast.push({
           instr: { type: char as BF_OP, param: jumpTarget },
-          location: { line: lIdx + 1, char: cIdx + 1 },
+          location: { line: lIdx, char: cIdx },
         });
       });
     });
diff --git a/engines/chef/runtime/index.ts b/engines/chef/runtime/index.ts
index 1add1aa..4e8da56 100644
--- a/engines/chef/runtime/index.ts
+++ b/engines/chef/runtime/index.ts
@@ -98,7 +98,7 @@ export default class ChefLanguageEngine implements LanguageEngine<T.ChefRS> {
       } else {
         // Next step is a regular method instruction
         const nextOp = currFrame.recipe.method[currFrame.pc];
-        nextStepLocation = this.convertTo1Index(nextOp.location);
+        nextStepLocation = nextOp.location;
       }
     }
 
@@ -191,19 +191,6 @@ export default class ChefLanguageEngine implements LanguageEngine<T.ChefRS> {
     if (opOutput) return opOutput;
   }
 
-  private convertTo1Index(location: DocumentRange): DocumentRange {
-    const lineNum = location.line + 1;
-    const charRange = location.charRange
-      ? {
-          start: location.charRange.start
-            ? location.charRange.start + 1
-            : undefined,
-          end: location.charRange.end ? location.charRange.end + 1 : undefined,
-        }
-      : undefined;
-    return { line: lineNum, charRange };
-  }
-
   /**
    * Empty the first N dishes of given kitchen into text output.
    * @param numDishes Number of dishes to empty as output
diff --git a/engines/deadfish/runtime.ts b/engines/deadfish/runtime.ts
index 0358606..f53abd8 100644
--- a/engines/deadfish/runtime.ts
+++ b/engines/deadfish/runtime.ts
@@ -57,7 +57,7 @@ export default class DeadfishLanguageEngine implements LanguageEngine<DFRS> {
         if (OP_CHARS.includes(char as DF_OP)) {
           ast.push({
             instr: char as DF_OP,
-            location: { line: lIdx + 1, char: cIdx + 1 },
+            location: { line: lIdx, char: cIdx },
           });
         }
       });
diff --git a/ui/code-editor/monaco-utils.ts b/ui/code-editor/monaco-utils.ts
index 3b11f7d..12f02ab 100644
--- a/ui/code-editor/monaco-utils.ts
+++ b/ui/code-editor/monaco-utils.ts
@@ -21,11 +21,12 @@ export const createHighlightRange = (
   monacoInstance: MonacoInstance,
   highlights: DocumentRange
 ): MonacoDecoration => {
-  const lineNum = highlights.line;
-  const startChar = highlights.charRange?.start || 0;
-  const endChar = highlights.charRange?.end || 1000;
+  const location = get1IndexedLocation(highlights);
+  const lineNum = location.line;
+  const startChar = location.charRange?.start || 0;
+  const endChar = location.charRange?.end || 1e5;
   const range = new monacoInstance.Range(lineNum, startChar, lineNum, endChar);
-  const isWholeLine = !highlights.charRange;
+  const isWholeLine = !location.charRange;
   return { range, options: { isWholeLine, inlineClassName: "code-highlight" } };
 };
 
@@ -39,3 +40,20 @@ export const createBreakpointRange = (
   const className = "breakpoint-glyph " + (hint ? "hint" : "solid");
   return { range, options: { glyphMarginClassName: className } };
 };
+
+/**
+ * Convert a DocumentRange to use 1-indexed values. Used since language engines
+ * use 0-indexed ranges but Monaco requires 1-indexed ranges.
+ * @param range DocumentRange to convert to 1-indexed
+ * @returns DocumentRange that uses 1-indexed values
+ */
+const get1IndexedLocation = (range: DocumentRange): DocumentRange => {
+  const lineNum = range.line + 1;
+  const charRange = range.charRange
+    ? {
+        start: range.charRange.start ? range.charRange.start + 1 : undefined,
+        end: range.charRange.end ? range.charRange.end + 1 : undefined,
+      }
+    : undefined;
+  return { line: lineNum, charRange };
+};
diff --git a/ui/code-editor/use-editor-breakpoints.ts b/ui/code-editor/use-editor-breakpoints.ts
index 95b8c07..0cf70c3 100644
--- a/ui/code-editor/use-editor-breakpoints.ts
+++ b/ui/code-editor/use-editor-breakpoints.ts
@@ -51,7 +51,9 @@ export const useEditorBreakpoints = ({
 
       // Update breakpoints to parent
       const bpLineNumStrs = Object.keys(breakpoints.current);
-      const bpLineNums = bpLineNumStrs.map((numStr) => parseInt(numStr, 10));
+      const bpLineNums = bpLineNumStrs.map(
+        (numStr) => parseInt(numStr, 10) - 1
+      );
       onUpdateBreakpoints(bpLineNums);
     });
     return () => disposer.dispose();