feat(spawn): default to the running agent; herdr-first management, no nohup

Six agents (claude, codex, pi, cursor, opencode, copilot). claude keeps
its native --bg/agents management. Everything else spawns interactively
inside herdr when its server is up (list/read/send/attach); otherwise a
transient systemd --user unit gives status/logs/stop. Research confirmed
none of the five non-claude CLIs has a native background job manager.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

skills/in-progress/spawn/SKILL.md

@@ -1,19 +1,19 @@
 ---
 name: spawn
-description: Hand the current conversation off to a fresh background agent — claude or codex — that picks up the work immediately.
+description: Hand the current conversation off to a fresh background agent that picks up the work immediately.
-argument-hint: "[claude|codex] What will the next session be used for?"
+argument-hint: "[agent] What will the next session be used for?"
 disable-model-invocation: true
 ---
 
 Write a handoff summary of the current conversation so a fresh agent can continue the work, then spawn the agent with it via the bundled [spawn.sh](spawn.sh) — run it, never read it:
 
 ```bash
-bash <this skill's base directory>/spawn.sh <claude|codex> "<descriptive session name>" - <<'PROMPT'
+bash <this skill's base directory>/spawn.sh <agent> "<descriptive session name>" - <<'PROMPT'
 <handoff summary>
 PROMPT
 ```
 
-Spawn `claude` unless the user named `codex`. The agent starts in the current working directory; the script prints how the user monitors the session — relay that.
+`<agent>` is one of `claude | codex | pi | cursor | opencode | copilot`. Spawn the agent you are running as, unless the user named another. The agent starts in the current working directory; the script prints how the user monitors and manages the session — relay that.
 
 The handoff summary:
 

skills/in-progress/spawn/spawn.sh

@@ -1,11 +1,17 @@
 #!/usr/bin/env bash
-# spawn.sh <claude|codex> <name> [prompt|-]
+# spawn.sh <agent> <name> [prompt|-]
 # Launches a background agent session seeded with the prompt.
 # Prompt is read from stdin when the third argument is omitted or '-'.
+#
+# claude has native managed background jobs (claude --bg / claude agents).
+# Every other agent is spawned interactively inside herdr when its server is
+# running (list/read/send/attach management); otherwise as a supervised
+# one-shot under the user's systemd session (status/logs/stop management).
 set -euo pipefail
 
 usage() {
-  echo "usage: spawn.sh <claude|codex> <name> [prompt|-]   (prompt read from stdin when omitted or '-')" >&2
+  echo "usage: spawn.sh <claude|codex|pi|cursor|opencode|copilot> <name> [prompt|-]" >&2
+  echo "       prompt is read from stdin when omitted or '-'" >&2
   exit 2
 }
 
@@ -19,24 +25,67 @@ if [ "$prompt" = "-" ]; then
 fi
 [ -n "$prompt" ] || { echo "spawn.sh: empty prompt" >&2; exit 2; }
 
-case "$agent" in
+if [ "$agent" = "claude" ]; then
-claude)
   claude --bg --name "$name" "$prompt"
   echo "Spawned claude session '$name'. Manage it with: claude agents"
-  ;;
+  exit 0
-codex)
+fi
+
+# Interactive invocation, seeded with the prompt — used inside herdr panes.
+case "$agent" in
+codex) interactive=(codex "$prompt") ;;
+pi) interactive=(pi "$prompt") ;;
+cursor) interactive=(cursor-agent "$prompt") ;;
+opencode) interactive=(opencode --prompt "$prompt") ;;
+copilot) interactive=(copilot -i "$prompt") ;;
+*) usage ;;
+esac
+
+if herdr agent list >/dev/null 2>&1; then
+  herdr agent start "$name" --cwd "$PWD" --no-focus -- "${interactive[@]}"
+  echo "Spawned $agent session '$name' in herdr."
+  echo "  list:   herdr agent list"
+  echo "  read:   herdr agent read '$name'"
+  echo "  steer:  herdr agent send '$name' '<text>'"
+  echo "  attach: herdr agent attach '$name'"
+  exit 0
+fi
+
+command -v systemd-run >/dev/null 2>&1 || {
+  echo "spawn.sh: no herdr server running and systemd-run unavailable — launch herdr and retry" >&2
+  exit 1
+}
+
+# Non-interactive one-shot — flags keep the run from blocking on approvals.
+case "$agent" in
+codex) oneshot=(codex exec --sandbox workspace-write --skip-git-repo-check "$prompt") ;;
+pi) oneshot=(pi -p "$prompt") ;;
+cursor) oneshot=(cursor-agent -p --force --output-format text "$prompt") ;;
+opencode) oneshot=(opencode run --title "$name" "$prompt") ;;
+copilot) oneshot=(copilot -p "$prompt" --allow-all-tools) ;;
+esac
+
+# The systemd user manager doesn't inherit this shell's PATH; resolve the
+# binary now and pass PATH through for any children it spawns.
+bin="$(command -v "${oneshot[0]}")" || {
+  echo "spawn.sh: ${oneshot[0]} is not installed" >&2
+  exit 1
+}
+oneshot[0]="$bin"
+
 slug="$(printf '%s' "$name" | tr '[:upper:] ' '[:lower:]-' | tr -cd 'a-z0-9-')"
-  dir="${TMPDIR:-/tmp}/codex-spawns"
+unit="spawn-${slug:-session}-$(date +%H%M%S)"
-  mkdir -p "$dir"
+systemd-run --user --unit "$unit" --working-directory="$PWD" \
-  base="$dir/${slug:-session}-$(date +%Y%m%d-%H%M%S)"
+  --setenv=PATH="$PATH" --setenv=HOME="$HOME" "${oneshot[@]}" >/dev/null 2>&1
-  nohup codex exec --sandbox workspace-write --cd "$PWD" \
+
-    -o "$base.last.md" - <<<"$prompt" >"$base.log" 2>&1 &
+echo "Spawned $agent session '$name' as user unit $unit (no herdr server running)."
-  echo "Spawned codex session '$name' (pid $!)."
+echo "  status: systemctl --user status $unit"
-  echo "  log:          $base.log"
+echo "  logs:   journalctl --user -u $unit -f"
-  echo "  final answer: $base.last.md"
+echo "  stop:   systemctl --user stop $unit"
-  echo "  follow with:  tail -f $base.log"
+case "$agent" in
-  ;;
+codex) echo "  resume: codex exec resume <session id from logs>" ;;
-*)
+pi) echo "  resume: pi -c   (from this directory)" ;;
-  usage
+cursor) echo "  resume: cursor-agent resume" ;;
-  ;;
+opencode) echo "  resume: opencode run -c   (or: opencode session list)" ;;
+copilot) echo "  resume: copilot --resume" ;;
 esac