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, 17 insertions, 2 deletions

diff --git a/Omni/Agent/Engine.hs b/Omni/Agent/Engine.hs
index 0dc7c50..343ccc3 100644
--- a/Omni/Agent/Engine.hs
+++ b/Omni/Agent/Engine.hs
@@ -799,8 +799,9 @@ executeToolCallsWithTracking engineCfg toolMap tcs initialTestFailures initialEd
               resultValue <- toolExecute tool args
               endTime <- Time.getCurrentTime
               let durationMs = round (Time.diffUTCTime endTime startTime * 1000)
-                  resultText = TE.decodeUtf8 (BL.toStrict (Aeson.encode resultValue))
-                  isTestCall = name == "bash" && ("bild --test" `Text.isInfixOf` argsText || "bild -t" `Text.isInfixOf` argsText)
+                  rawResultText = TE.decodeUtf8 (BL.toStrict (Aeson.encode resultValue))
+                  resultText = truncateToolResult rawResultText
+                  isTestCall = name == "run_bash" && ("bild --test" `Text.isInfixOf` argsText || "bild -t" `Text.isInfixOf` argsText)
                   isTestFailure = isTestCall && isFailureResult resultValue
                   testDelta = if isTestFailure then 1 else 0
                   isEditFailure = name == "edit_file" && isOldStrNotFoundError resultValue
@@ -830,6 +831,20 @@ executeToolCallsWithTracking engineCfg toolMap tcs initialTestFailures initialEd
         _ -> False
     isOldStrNotFoundError _ = False
 
+-- | Maximum characters for any tool result (engine-level safety net)
+maxToolResultChars :: Int
+maxToolResultChars = 10000
+
+-- | Truncate tool result if too long (engine-level safety net)
+truncateToolResult :: Text -> Text
+truncateToolResult t
+  | Text.length t <= maxToolResultChars = t
+  | otherwise =
+      Text.take maxToolResultChars t
+        <> "\n\n[TOOL RESULT TRUNCATED by engine - "
+        <> tshow (Text.length t - maxToolResultChars)
+        <> " chars omitted]"
+
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