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diff --git a/Omni/Log/Terminal.hs b/Omni/Log/Terminal.hs
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+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+
+-- | Terminal detection and output mode selection
+module Omni.Log.Terminal
+  ( TerminalInfo (..),
+    OutputMode (..),
+    detectTerminal,
+    truncateToWidth,
+  )
+where
+
+import Alpha
+import qualified Control.Exception as Exception
+import qualified Data.Text as Text
+import qualified System.Console.ANSI as ANSI
+import qualified System.Environment as Env
+
+data OutputMode
+  = MultiLine -- Wide terminals (≥80 cols) - reserved lines per namespace
+  | SingleLine -- Narrow terminals (<80 cols) - rotating single line
+  deriving (Eq, Show)
+
+data TerminalInfo = TerminalInfo
+  { tiWidth :: Int,
+    tiHeight :: Int,
+    tiMode :: OutputMode,
+    tiSupportsANSI :: Bool
+  }
+  deriving (Eq, Show)
+
+detectTerminal :: IO TerminalInfo
+detectTerminal = do
+  term <- Env.lookupEnv "TERM"
+  area <- Env.lookupEnv "AREA"
+  noColor <- Env.lookupEnv "NO_COLOR"
+
+  -- Check if we support ANSI
+  let supportsANSI = case (term, area, noColor) of
+        (_, _, Just _) -> False -- NO_COLOR set
+        (Just "dumb", _, _) -> False
+        (_, Just "Live", _) -> False -- production logs
+        (Nothing, _, _) -> False
+        _ -> True
+
+  -- Get terminal size, catching exceptions from stdin issues
+  -- When NO_COLOR is set or ANSI is not supported, skip terminal size detection
+  -- to avoid outputting escape codes
+  mSize <-
+    if supportsANSI
+      then Exception.catch ANSI.getTerminalSize <| \(_ :: Exception.IOException) -> pure Nothing
+      else pure Nothing -- Skip if no ANSI support
+  let (width, height) = case mSize of
+        Just (h, w) -> (w, h)
+        Nothing -> (80, 24) -- sensible default
+
+  -- Determine mode based on ANSI support
+  let mode
+        | not supportsANSI = SingleLine -- Fallback to single line for dumb terminals
+        | otherwise = MultiLine
+
+  pure
+    TerminalInfo
+      { tiWidth = width,
+        tiHeight = height,
+        tiMode = mode,
+        tiSupportsANSI = supportsANSI
+      }
+
+-- | Truncate text to fit width with ellipsis
+truncateToWidth :: Int -> Text -> Text
+truncateToWidth maxWidth text
+  | Text.length text <= maxWidth = text
+  | maxWidth <= 3 = Text.take maxWidth text
+  | otherwise = Text.take (maxWidth - 3) text <> "..."