diff --git a/hermes_cli/pty_bridge.py b/hermes_cli/pty_bridge.py
index 9a8a73bad..66fdb4ac7 100644
--- a/hermes_cli/pty_bridge.py
+++ b/hermes_cli/pty_bridge.py
@@ -108,9 +108,14 @@ class PtyBridge:
                     "(or pip install -e '.[pty]')."
                 )
             raise PtyUnavailableError("Pseudo-terminals are unavailable.")
-        # Let caller-supplied env fully override inheritance; if they pass
-        # None we inherit the server's env (same semantics as subprocess).
-        spawn_env = os.environ.copy() if env is None else env
+        # PTY-hosted programs expect TERM to describe the terminal type.
+        # CI often runs without TERM in the parent process, which makes
+        # simple terminal probes like `tput cols` fail before winsize reads.
+        # Preserve explicit caller overrides, but backfill a sensible default
+        # when TERM is missing or blank.
+        spawn_env = (os.environ.copy() if env is None else env.copy())
+        if not spawn_env.get("TERM"):
+            spawn_env["TERM"] = "xterm-256color"
         proc = ptyprocess.PtyProcess.spawn(  # type: ignore[union-attr]
             list(argv),
             cwd=cwd,