diff --git a/data/scripts/o b/data/scripts/o
index 2239dda..f2caa11 100755
--- a/data/scripts/o
+++ b/data/scripts/o
@@ -125,6 +125,17 @@ resolve_path() {
 
 # ── Context requirements for specific commands ──────────────────
 
+# Resolve session and agent from positional args or env vars.
+# Usage: resolve_context "$@"  →  returns (s, a) by modifying caller's vars.
+# Pass "$@" from the calling command; it shifts positional args.
+resolve_context() {
+    local _s _a
+    _s="${1:-${session:-}}"
+    [[ -n "$1" ]] && shift
+    _a="${1:-${agent:-}}"
+    echo "$_s|$_a"
+}
+
 require_session() {
     local s="${session:-}"
     if [[ -z "$s" ]]; then
@@ -240,16 +251,32 @@ cmd_ctl() {
         echo "  commands: stop, compact, kill, clear, model <m>, backend <b>, cwd <d>" >&2
         exit 1
     fi
-    local path
-    path=$(agent_path) || exit 1
-    echo "$*" | ollie-9p write "$path/ctl"
+    local ctx s a
+    ctx=$(resolve_context "$@") || exit 1
+    s="${ctx%%|*}"
+    a="${ctx##*|}"
+    shift; shift
+    if [[ -z "$s" || -z "$a" ]]; then
+        echo "error: session and agent are required" >&2
+        echo "  usage: o ctl <command> [args...]" >&2
+        echo "  or:    export session=<name> agent=<name>" >&2
+        exit 1
+    fi
+    echo "$*" | ollie-9p write "session/$s/agent/$a/ctl"
 }
 
 cmd_prompt() {
-    local s a path
-    s=$(require_session) || exit 1
-    a=$(require_agent "$s") || exit 1
-    path="session/$s/agent/$a"
+    local ctx s a
+    ctx=$(resolve_context "$@") || exit 1
+    s="${ctx%%|*}"
+    a="${ctx##*|}"
+    if [[ -z "$s" || -z "$a" ]]; then
+        echo "error: session and agent are required" >&2
+        echo "  usage: o prompt <session> <agent>" >&2
+        echo "  or:    export session=<name> agent=<name>" >&2
+        exit 1
+    fi
+    local path="session/$s/agent/$a"
     
     echo "[$s/$a]"
     echo "Type . on a blank line to send, Ctrl+D to exit."
@@ -335,9 +362,17 @@ cmd_prompt() {
 }
 
 cmd_tail() {
-    local path
-    path=$(agent_path) || exit 1
-    exec ollie-9p read "$path/chat"
+    local ctx s a
+    ctx=$(resolve_context "$@") || exit 1
+    s="${ctx%%|*}"
+    a="${ctx##*|}"
+    if [[ -z "$s" || -z "$a" ]]; then
+        echo "error: session and agent are required" >&2
+        echo "  usage: o tail <session> <agent>" >&2
+        echo "  or:    export session=<name> agent=<name>" >&2
+        exit 1
+    fi
+    exec ollie-9p read "session/$s/agent/$a/chat"
 }
 
 cmd_env() {
@@ -356,14 +391,27 @@ cmd_env() {
 }
 
 cmd_stop() {
-    local path
-    path=$(agent_path) || exit 1
-    echo "stop" | ollie-9p write "$path/ctl"
+    local ctx s a
+    ctx=$(resolve_context "$@") || exit 1
+    s="${ctx%%|*}"
+    a="${ctx##*|}"
+    if [[ -z "$s" || -z "$a" ]]; then
+        echo "error: session and agent are required" >&2
+        echo "  usage: o stop <session> <agent>" >&2
+        echo "  or:    export session=<name> agent=<name>" >&2
+        exit 1
+    fi
+    echo "stop" | ollie-9p write "session/$s/agent/$a/ctl"
 }
 
 cmd_kill() {
-    local s
-    s=$(require_session) || exit 1
+    local s="${1:-${session:-}}"
+    if [[ -z "$s" ]]; then
+        echo "error: no session set" >&2
+        echo "  usage: o kill <session>" >&2
+        echo "  or:    export session=<name>" >&2
+        exit 1
+    fi
     echo "kill" | ollie-9p write "session/$s/ctl"
 }
 
@@ -382,9 +430,10 @@ cmd_tui() {
     fi
 
     # Accept optional positional args: o tui [session] [agent]
-    s="${1:-${session:-}}"
-    if [[ -n "$1" ]]; then shift; fi
-    a="${1:-${agent:-}}"
+    local ctx
+    ctx=$(resolve_context "$@")
+    s="${ctx%%|*}"
+    a="${ctx##*|}"
 
     if [[ -z "$s" ]]; then
         echo "error: no session set" >&2