Omni/Agent: make token explosion impossible

Tools.hs:
- run_bash now uses mkSuccess (applies truncation)
- read_file requires line ranges for files >500 lines
- read_file rejects ranges >400 lines

Engine.hs:
- Added engine-level truncateToolResult (10k char cap)
- Fixed test detection: bash -> run_bash

1 files changed, 42 insertions, 15 deletions

diff --git a/Omni/Agent/Tools.hs b/Omni/Agent/Tools.hs
index 0bd394f..5078b11 100644
--- a/Omni/Agent/Tools.hs
+++ b/Omni/Agent/Tools.hs
@@ -214,6 +214,14 @@ instance Aeson.FromJSON ToolResult where
 maxOutputChars :: Int
 maxOutputChars = 8000
 
+-- | Maximum lines per read_file call
+maxReadLinesPerCall :: Int
+maxReadLinesPerCall = 400
+
+-- | Files larger than this require explicit line ranges
+largeFileLineThreshold :: Int
+largeFileLineThreshold = 500
+
 -- | Truncate output if too long, adding a notice
 truncateOutput :: Text -> Text
 truncateOutput output
@@ -296,12 +304,38 @@ executeReadFile v =
         then do
           content <- TextIO.readFile path
           let allLines = Text.lines content
-              startIdx = maybe 0 (\n -> n - 1) (readFileStartLine args)
-              endIdx = maybe (length allLines) identity (readFileEndLine args)
-              selectedLines = take (endIdx - startIdx) (drop startIdx allLines)
-              numberedLines = zipWith formatLine [(startIdx + 1) ..] selectedLines
-              result = Text.unlines numberedLines
-          pure <| mkSuccess result
+              totalLines = length allLines
+              hasRange = isJust (readFileStartLine args) || isJust (readFileEndLine args)
+
+          if not hasRange && totalLines > largeFileLineThreshold
+            then
+              pure
+                <| mkError
+                  ( "File is large ("
+                      <> tshow totalLines
+                      <> " lines). You must provide start_line and end_line, with at most "
+                      <> tshow maxReadLinesPerCall
+                      <> " lines per call."
+                  )
+            else do
+              let startIdx = maybe 0 (\n -> n - 1) (readFileStartLine args)
+                  endIdx = maybe (length allLines) identity (readFileEndLine args)
+                  requestedLines = endIdx - startIdx
+              if requestedLines > maxReadLinesPerCall
+                then
+                  pure
+                    <| mkError
+                      ( "Requested range is too large ("
+                          <> tshow requestedLines
+                          <> " lines). Max "
+                          <> tshow maxReadLinesPerCall
+                          <> " lines per read_file call."
+                      )
+                else do
+                  let selectedLines = take requestedLines (drop startIdx allLines)
+                      numberedLines = zipWith formatLine [(startIdx + 1) ..] selectedLines
+                      result = Text.unlines numberedLines
+                  pure <| mkSuccess result
         else pure <| mkError ("File not found: " <> readFilePath args)
   where
     formatLine :: Int -> Text -> Text
@@ -520,20 +554,13 @@ executeRunBash v =
           (exitCode, stdoutStr, stderrStr) <- Process.readCreateProcessWithExitCode proc ""
           let output = Text.pack stdoutStr <> Text.pack stderrStr
           case exitCode of
-            Exit.ExitSuccess ->
-              pure
-                <| Aeson.toJSON
-                <| ToolResult
-                  { toolResultSuccess = True,
-                    toolResultOutput = output,
-                    toolResultError = Nothing
-                  }
+            Exit.ExitSuccess -> pure <| mkSuccess output
             Exit.ExitFailure code ->
               pure
                 <| Aeson.toJSON
                 <| ToolResult
                   { toolResultSuccess = False,
-                    toolResultOutput = output,
+                    toolResultOutput = truncateOutput output,
                     toolResultError = Just ("Exit code: " <> tshow code)
                   }