tweak(edit): separate edit tool error message with clearer guidance to avoid llm doom editing loop

packages/opencode/src/tool/edit.ts

@@ -595,6 +595,8 @@ export function replace(content: string, oldString: string, newString: string, r
     throw new Error("oldString and newString must be different")
   }
 
+  let notFound = true
+
   for (const replacer of [
     SimpleReplacer,
     LineTrimmedReplacer,
@@ -609,6 +611,7 @@ export function replace(content: string, oldString: string, newString: string, r
     for (const search of replacer(content, oldString)) {
       const index = content.indexOf(search)
       if (index === -1) continue
+      notFound = false
       if (replaceAll) {
         return content.replaceAll(search, newString)
       }
@@ -617,5 +620,9 @@ export function replace(content: string, oldString: string, newString: string, r
       return content.substring(0, index) + newString + content.substring(index + search.length)
     }
   }
-  throw new Error("oldString not found in content or was found multiple times")
+
+  if (notFound) {
+    throw new Error("oldString not found in content")
+  }
+  throw new Error("oldString found multiple times and requires more code context to uniquely identify the intended match")
 }

packages/opencode/src/tool/edit.txt

@@ -5,5 +5,6 @@ Usage:
 - When editing text from Read tool output, ensure you preserve the exact indentation (tabs/spaces) as it appears AFTER the line number prefix. The line number prefix format is: spaces + line number + tab. Everything after that tab is the actual file content to match. Never include any part of the line number prefix in the oldString or newString.
 - ALWAYS prefer editing existing files in the codebase. NEVER write new files unless explicitly required.
 - Only use emojis if the user explicitly requests it. Avoid adding emojis to files unless asked.
-- The edit will FAIL if `oldString` is not unique in the file. Either provide a larger string with more surrounding context to make it unique or use `replaceAll` to change every instance of `oldString`. 
+- The edit will FAIL if `oldString` is not found in the file with an error "oldString not found in content".
+- The edit will FAIL if `oldString` is found multiple times in the file with an error "oldString found multiple times and requires more code context to uniquely identify the intended match". Either provide a larger string with more surrounding context to make it unique or use `replaceAll` to change every instance of `oldString`. 
 - Use `replaceAll` for replacing and renaming strings across the file. This parameter is useful if you want to rename a variable for instance.