diff --git a/cmd_chat/operator/__main__.py b/cmd_chat/operator/__main__.py
index b4b35e9..1ecf18e 100644
--- a/cmd_chat/operator/__main__.py
+++ b/cmd_chat/operator/__main__.py
@@ -37,6 +37,12 @@ def _add_conn_args(p: argparse.ArgumentParser) -> None:
     p.add_argument("--trigger", default=None,
                    help="extra phrase that marks a message 'addressed' to us "
                         "(the operator name / @name always count)")
+    p.add_argument("--depth", type=int, default=1,
+                   help="recursion depth budget (levels of nested operators)")
+    p.add_argument("--fanout", type=int, default=2,
+                   help="recursion fan-out budget (children per level)")
+    p.add_argument("--cost", type=float, default=5.0,
+                   help="soft cost ceiling (USD) carried to children")
 
 
 def _build_parser() -> argparse.ArgumentParser:
@@ -81,6 +87,24 @@ def _build_parser() -> argparse.ArgumentParser:
     gt.add_argument("--out", default=None, help="write to this local path (else stdout)")
     gt.add_argument("--session", default=None)
 
+    sp = sub.add_parser("spawn", help="spawn a nested Claude operator (budgeted)")
+    sp.add_argument("objective", help="what the nested operator should achieve")
+    sp.add_argument("--room-host", required=True)
+    sp.add_argument("--room-port", type=int, required=True)
+    sp.add_argument("--room-name", default="operator")
+    sp.add_argument("--stop", action="append", default=None,
+                    help="a stop condition (repeatable)")
+    sp.add_argument("--target", choices=["host"], default="host")
+    sp.add_argument("--config-dir", default=None,
+                    help="isolated CLAUDE_CONFIG_DIR for the child")
+    sp.add_argument("--allow-creds", action="store_true",
+                    help="carry our credentials to the child (default: off)")
+    sp.add_argument("--skip-permissions", action="store_true",
+                    help="run the child unattended (--dangerously-skip-permissions)")
+    sp.add_argument("--go", action="store_true",
+                    help="actually launch (default is a dry-run plan)")
+    sp.add_argument("--session", default=None)
+
     ky = sub.add_parser("keys", help="inject keystrokes into the room's shared PTY")
     ky.add_argument("keys", nargs="*",
                     help="tokens: literal text, named keys (enter, ctrl-c, esc, "
@@ -96,10 +120,12 @@ def _build_parser() -> argparse.ArgumentParser:
 # ── daemon ───────────────────────────────────────────────────────────────
 def _run_serve(args) -> int:
     from .bridge import OperatorBridge  # heavy imports only on the daemon path
+    from .bootstrap import Budget
+    budget = Budget(depth=args.depth, fanout=args.fanout, cost_usd=args.cost)
     bridge = OperatorBridge(
         args.host, args.port, name=args.user, password=args.password,
         insecure=args.insecure, no_tls=args.no_tls,
-        session=args.session, trigger=args.trigger)
+        session=args.session, trigger=args.trigger, budget=budget)
     try:
         bridge.run()
     except KeyboardInterrupt:
@@ -139,6 +165,8 @@ def _run_up(args) -> int:
         cmd += ["--session", args.session]
     if args.trigger:
         cmd += ["--trigger", args.trigger]
+    cmd += ["--depth", str(args.depth), "--fanout", str(args.fanout),
+            "--cost", str(args.cost)]
 
     log = open(sess.log_path, "a")  # noqa: SIM115 — handed to the child
     proc = subprocess.Popen(cmd, stdout=log, stderr=log, stdin=subprocess.DEVNULL,
@@ -267,6 +295,18 @@ def _run_get(args) -> int:
     return 0
 
 
+def _run_spawn(args) -> int:
+    resp = _client_request(args, {
+        "op": "spawn", "objective": args.objective,
+        "room": {"host": args.room_host, "port": args.room_port,
+                 "name": args.room_name},
+        "stop": args.stop, "target": args.target,
+        "config_dir": args.config_dir, "allow_creds": args.allow_creds,
+        "skip_permissions": args.skip_permissions, "dry_run": not args.go})
+    print(json.dumps(resp, indent=2))
+    return 0 if resp.get("ok") else 1
+
+
 def _run_keys(args) -> int:
     from . import sandbox as sbx
     if args.help_keys:
@@ -309,6 +349,8 @@ def main(argv: list[str] | None = None) -> int:
         return _run_get(args)
     if verb == "keys":
         return _run_keys(args)
+    if verb == "spawn":
+        return _run_spawn(args)
     if verb in ("roster", "status", "down"):
         return _run_simple(args, verb)
     return 2
diff --git a/cmd_chat/operator/bootstrap.py b/cmd_chat/operator/bootstrap.py
new file mode 100644
index 0000000..4ee0074
--- /dev/null
+++ b/cmd_chat/operator/bootstrap.py
@@ -0,0 +1,215 @@
+"""Bootstrap + recursive-spawn primitives for the operator bridge (Phase 5).
+
+Goal: from inside one room (or a sandbox/VM the operator owns), stand up a
+*nested* Claude Code session that runs the `hh-operator` skill against another
+room — a tree of operators. Doing that safely needs four things, all here:
+
+1. **Detect** the target system (OS / arch / package manager / what's already
+   installed) so install is a decision, not a guess.
+2. **Install** Claude Code via a *known* package name (npm `@anthropic-ai/
+   claude-code`) or an explicitly-configured installer — never a guessed URL.
+3. **Authenticate** by carrying the parent's own credentials into the child —
+   but **gated off by default**: a child auths itself unless the operator
+   explicitly opts in (`allow_creds`). We never exfiltrate creds to a system we
+   don't own, and never enable this implicitly.
+4. **Budget** the recursion: hard **depth** and **fan-out** caps plus a soft
+   **cost** ceiling, decremented on every descent, refusing at zero. This is the
+   guardrail that stops a runaway tree.
+
+This module is pure/decision-making: it builds argv, plans, and budgets. It does
+not itself run network installs or launch detached Claude sessions — the bridge
+does that behind explicit flags, so unit tests can exercise all the logic with
+no side effects.
+"""
+
+from __future__ import annotations
+
+import os
+import platform
+import shutil
+from dataclasses import dataclass, replace
+from pathlib import Path
+
+# Documented install package — NOT a guessed URL. Override the whole install
+# command with $HH_CLAUDE_INSTALL when a site has its own channel.
+CLAUDE_NPM_PACKAGE = "@anthropic-ai/claude-code"
+
+
+class BudgetExhausted(RuntimeError):
+    """A spawn was refused because a recursion budget hit zero."""
+
+
+@dataclass(frozen=True)
+class Budget:
+    """Hard caps on a recursion tree.
+
+    - ``depth``  — how many more levels may be spawned below here (0 = leaf).
+    - ``fanout`` — how many children *this* node may still spawn.
+    - ``cost_usd`` — soft ceiling carried down and surfaced to the child as a
+      directive (Claude Code has no native $ cap, so this is advisory; depth and
+      fanout are the hard stops).
+    """
+    depth: int = 1
+    fanout: int = 2
+    cost_usd: float = 5.0
+
+    def can_spawn(self) -> bool:
+        return self.depth > 0 and self.fanout > 0
+
+    def descend(self) -> "Budget":
+        """Consume one child slot at this level and return the budget the child
+        inherits (one level shallower, its own fresh fanout). Raises when this
+        node can't spawn any more."""
+        if self.depth <= 0:
+            raise BudgetExhausted("depth budget exhausted — cannot nest deeper")
+        if self.fanout <= 0:
+            raise BudgetExhausted("fan-out budget exhausted at this level")
+        # The child gets depth-1 and the same fanout/cost to share among its own
+        # children; *this* node records one fewer remaining child via `spent`.
+        return Budget(depth=self.depth - 1, fanout=self.fanout, cost_usd=self.cost_usd)
+
+    def spent(self) -> "Budget":
+        """Return this node's budget after using one of its child slots."""
+        return replace(self, fanout=self.fanout - 1)
+
+    def as_dict(self) -> dict:
+        return {"depth": self.depth, "fanout": self.fanout, "cost_usd": self.cost_usd}
+
+
+# ── detection ───────────────────────────────────────────────────────────────
+def _distro_id() -> str:
+    try:
+        for line in Path("/etc/os-release").read_text().splitlines():
+            if line.startswith("ID="):
+                return line.split("=", 1)[1].strip().strip('"')
+    except OSError:
+        pass
+    return ""
+
+
+def _pkg_manager() -> str | None:
+    for mgr in ("apt-get", "dnf", "yum", "apk", "pacman", "brew"):
+        if shutil.which(mgr):
+            return mgr
+    return None
+
+
+def detect_system() -> dict:
+    """Snapshot what the bootstrap needs to decide install strategy. Pure read —
+    no mutation, safe to call anywhere (including inside a sandbox via exec)."""
+    return {
+        "os": platform.system().lower(),          # linux / darwin
+        "arch": platform.machine(),               # x86_64 / aarch64 …
+        "distro": _distro_id(),                    # ubuntu / debian / alpine …
+        "pkg_manager": _pkg_manager(),
+        "has_node": shutil.which("node") is not None,
+        "has_npm": shutil.which("npm") is not None,
+        "claude": shutil.which("claude"),          # path or None
+    }
+
+
+def claude_present() -> bool:
+    return shutil.which("claude") is not None
+
+
+def install_plan(sysinfo: dict | None = None) -> list[list[str]]:
+    """Ordered candidate commands to get the `claude` CLI onto the system.
+
+    Honours $HH_CLAUDE_INSTALL (a full shell command) first so a site can pin
+    its own channel. Otherwise prefers the documented npm package; if npm is
+    missing, prefix the distro's node install. We never fabricate a download
+    URL — if none of these apply the caller surfaces "install claude manually"."""
+    override = os.environ.get("HH_CLAUDE_INSTALL")
+    if override:
+        return [["sh", "-c", override]]
+    info = sysinfo or detect_system()
+    plans: list[list[str]] = []
+    if info.get("has_npm"):
+        plans.append(["npm", "install", "-g", CLAUDE_NPM_PACKAGE])
+    else:
+        mgr = info.get("pkg_manager")
+        node_install = {
+            "apt-get": ["apt-get", "install", "-y", "nodejs", "npm"],
+            "dnf": ["dnf", "install", "-y", "nodejs", "npm"],
+            "yum": ["yum", "install", "-y", "nodejs", "npm"],
+            "apk": ["apk", "add", "nodejs", "npm"],
+            "pacman": ["pacman", "-Sy", "--noconfirm", "nodejs", "npm"],
+            "brew": ["brew", "install", "node"],
+        }.get(mgr)
+        if node_install:
+            plans.append(node_install)
+            plans.append(["npm", "install", "-g", CLAUDE_NPM_PACKAGE])
+    return plans
+
+
+# ── credentials (gated) ─────────────────────────────────────────────────────
+def creds_source() -> Path | None:
+    """The parent session's own OAuth/API credentials file, if present."""
+    p = Path.home() / ".claude" / ".credentials.json"
+    return p if p.exists() else None
+
+
+def plan_creds(dest_home: str | os.PathLike, *, allow: bool) -> dict:
+    """Decide whether to carry credentials into a child's config dir.
+
+    Default (``allow=False``) → carry nothing; the child must authenticate
+    itself (`claude` interactive login or its own $ANTHROPIC_API_KEY). Only when
+    the operator *explicitly* opts in do we stage a copy of our own creds — and
+    only into a path we were handed. This function plans; the bridge performs the
+    copy so the side effect stays behind one audited flag."""
+    if not allow:
+        return {"staged": False, "reason": "creds gating on — child authenticates itself"}
+    src = creds_source()
+    if src is None:
+        return {"staged": False, "reason": "no parent credentials to carry"}
+    dest = Path(dest_home) / ".claude" / ".credentials.json"
+    return {"staged": True, "src": str(src), "dest": str(dest)}
+
+
+# ── directive + run argv ────────────────────────────────────────────────────
+def compose_directive(objective: str, room: dict, budget: Budget,
+                      stop: list[str] | None = None) -> str:
+    """The prompt the nested Claude runs under `claude -p`. Tells it to use the
+    hh-operator skill, where to join, what to achieve, when to stop, and the
+    recursion budget it inherits (so it self-limits its own spawns)."""
+    host, port = room.get("host", "?"), room.get("port", "?")
+    name = room.get("name", "operator")
+    stop = stop or ["objective met", "owner says stop/leave", "idle past remit"]
+    lines = [
+        "Use the hh-operator skill. You are an autonomous operator joining a "
+        "hack-house room.",
+        f"Join: `hh-bridge up {host} {port} {name}` "
+        f"(password via room config; add --no-tls for plain ws).",
+        f"Objective: {objective}",
+        "Stop conditions (leave with `hh-bridge down` when any is met): "
+        + "; ".join(stop) + ".",
+        f"Recursion budget you inherit: depth={budget.depth}, "
+        f"fanout={budget.fanout}, cost≈${budget.cost_usd:.2f}. "
+        "You may spawn at most `fanout` child operators and only while depth>0; "
+        "pass each child a decremented budget. Stay within the cost ceiling.",
+        "Drive sandboxes only after the owner grants you. Never touch a system "
+        "you weren't asked to.",
+    ]
+    return "\n".join(lines)
+
+
+def build_run_argv(directive: str, *, skip_permissions: bool = False,
+                   config_dir: str | None = None,
+                   claude_bin: str = "claude") -> list[str]:
+    """argv to launch a headless nested Claude session. `skip_permissions` maps
+    to Claude Code's unattended flag (only for trusted, sandboxed autonomy);
+    `config_dir` points the child at an isolated $CLAUDE_CONFIG_DIR so its creds
+    and state don't collide with the parent."""
+    argv = [claude_bin, "-p", directive]
+    if skip_permissions:
+        argv.append("--dangerously-skip-permissions")
+    return argv
+
+
+def child_env(config_dir: str | None = None) -> dict:
+    """Environment for the child process. Isolates its config dir when given so
+    a nested session's auth/state is its own."""
+    env = dict(os.environ)
+    if config_dir:
+        env["CLAUDE_CONFIG_DIR"] = str(config_dir)
+    return env
diff --git a/cmd_chat/operator/bridge.py b/cmd_chat/operator/bridge.py
index 224b0ad..7b8533d 100644
--- a/cmd_chat/operator/bridge.py
+++ b/cmd_chat/operator/bridge.py
@@ -25,6 +25,7 @@ import time
 import websockets
 
 from ..client.client import Client
+from . import bootstrap as boot
 from . import sandbox as sbx
 from .session import Session
 
@@ -39,12 +40,14 @@ class OperatorBridge(Client):
     def __init__(self, server: str, port: int, name: str,
                  password: str | None = None, insecure: bool = False,
                  no_tls: bool = False, session: str | None = None,
-                 trigger: str | None = None):
+                 trigger: str | None = None, budget: boot.Budget | None = None):
         super().__init__(server, port, username=name, password=password,
                          insecure=insecure, no_tls=no_tls)
         self.name = name
         self.trigger = (trigger or "").strip()
         self.session = Session(session or name)
+        # Recursion budget this operator may spend spawning nested operators.
+        self.budget = budget or boot.Budget()
 
         # Inbox: monotonically-seq'd events + an async condition to wake waiters.
         self.events: list[dict] = []
@@ -302,6 +305,8 @@ class OperatorBridge(Client):
             return await self._op_get(req)
         if op == "keys":
             return await self._op_keys(req)
+        if op == "spawn":
+            return await self._op_spawn(req)
         if op == "down":
             asyncio.get_running_loop().call_soon(self._begin_shutdown)
             return {"ok": True, "stopping": True}
@@ -469,6 +474,87 @@ class OperatorBridge(Client):
         await self._emit("keys", bytes=len(data))
         return {"ok": True, "bytes": len(data)}
 
+    # ── recursive spawn (Phase 5) ────────────────────────────────────────
+    async def _op_spawn(self, req: dict) -> dict:
+        """Stand up a nested Claude Code operator against another room.
+
+        Guardrails, in order:
+        - **budget** — refuse unless this node may still spawn (depth>0 &
+          fanout>0); the child inherits a decremented budget, we record one spent
+          slot. This is the hard stop against a runaway tree.
+        - **creds gating** — we carry our own credentials to the child *only* when
+          `allow_creds` is explicitly set; otherwise the child authenticates
+          itself. Never implicit, never to a system we don't own.
+        - **dry_run** — default returns the full plan (argv, budget, creds
+          decision) and launches nothing, so a tree can be inspected before it's
+          grown.
+
+        `target` is "host" (Popen detached here) — sandbox/VM placement is the
+        operator's to run via `exec` using the returned plan."""
+        objective = str(req.get("objective", "")).strip()
+        if not objective:
+            return {"ok": False, "error": "spawn needs an objective"}
+        room = req.get("room") or {}
+        if not room.get("host") or not room.get("port"):
+            return {"ok": False, "error": "spawn needs room {host, port, name}"}
+
+        if not self.budget.can_spawn():
+            return {"ok": False, "error": "recursion budget exhausted "
+                    f"(depth={self.budget.depth}, fanout={self.budget.fanout})"}
+        try:
+            child_budget = self.budget.descend()
+        except boot.BudgetExhausted as e:
+            return {"ok": False, "error": str(e)}
+
+        allow_creds = bool(req.get("allow_creds", False))
+        dry_run = bool(req.get("dry_run", True))
+        skip_perms = bool(req.get("skip_permissions", False))
+        config_dir = req.get("config_dir")
+
+        stop = req.get("stop") or None
+        directive = boot.compose_directive(objective, room, child_budget, stop=stop)
+        argv = boot.build_run_argv(directive, skip_permissions=skip_perms,
+                                   config_dir=config_dir)
+        creds = boot.plan_creds(config_dir or "~", allow=allow_creds)
+        plan = {"argv": argv, "budget": child_budget.as_dict(), "creds": creds,
+                "target": req.get("target", "host"),
+                "claude_present": boot.claude_present()}
+
+        if dry_run:
+            return {"ok": True, "dry_run": True, "plan": plan}
+
+        if not boot.claude_present():
+            return {"ok": False, "error": "claude CLI not installed",
+                    "install_plan": boot.install_plan(), "plan": plan}
+
+        # Carry creds only behind the explicit gate.
+        if creds.get("staged"):
+            try:
+                dest = boot.Path(creds["dest"])
+                dest.parent.mkdir(parents=True, exist_ok=True)
+                dest.write_bytes(boot.Path(creds["src"]).read_bytes())
+                dest.chmod(0o600)
+            except OSError as e:
+                return {"ok": False, "error": f"creds staging failed: {e}"}
+
+        # Launch detached so the child outlives this daemon; logs to the session.
+        import subprocess
+        try:
+            logf = open(self.session.dir / f"spawn-{self.seq + 1}.log", "a")  # noqa: SIM115
+            proc = subprocess.Popen(
+                argv, env=boot.child_env(config_dir),
+                stdout=logf, stderr=logf, stdin=subprocess.DEVNULL,
+                start_new_session=True, close_fds=True)
+        except OSError as e:
+            return {"ok": False, "error": f"spawn launch failed: {e}"}
+
+        self.budget = self.budget.spent()  # consume one child slot here
+        await self._emit("spawn", objective=objective, pid=proc.pid,
+                         budget=child_budget.as_dict(),
+                         creds_staged=creds.get("staged", False))
+        return {"ok": True, "pid": proc.pid, "plan": plan,
+                "remaining": self.budget.as_dict()}
+
     def _begin_shutdown(self) -> None:
         self._stop.set()
         self.running = False
diff --git a/tests/test_operator_bridge.py b/tests/test_operator_bridge.py
index 131ae8c..aa4cc6d 100644
--- a/tests/test_operator_bridge.py
+++ b/tests/test_operator_bridge.py
@@ -15,6 +15,7 @@ from cryptography.fernet import Fernet
 
 from cmd_chat.operator.bridge import OperatorBridge
 from cmd_chat.operator import sandbox as sbx
+from cmd_chat.operator import bootstrap as boot
 
 
 def _bridge(name="oracle", trigger=None):
@@ -272,3 +273,93 @@ def test_exec_requires_target():
         r = await b._op_exec({"cmd": ""})
         assert r["ok"] is False and "empty" in r["error"]
     asyncio.run(go())
+
+
+# ── Phase 5: recursion budget guardrails ──────────────────────────────────
+def test_budget_descend_and_exhaust():
+    b = boot.Budget(depth=2, fanout=2, cost_usd=5.0)
+    assert b.can_spawn()
+    child = b.descend()                       # one level down for the child
+    assert child.depth == 1 and child.fanout == 2
+    spent = b.spent()                         # this node used one child slot
+    assert spent.fanout == 1 and spent.depth == 2
+    # depth floor: a leaf cannot nest
+    leaf = boot.Budget(depth=0, fanout=2)
+    assert not leaf.can_spawn()
+    try:
+        leaf.descend()
+        assert False, "expected BudgetExhausted"
+    except boot.BudgetExhausted:
+        pass
+    # fan-out floor
+    spread = boot.Budget(depth=3, fanout=0)
+    assert not spread.can_spawn()
+
+
+def test_install_plan_prefers_npm_and_honors_override(monkeypatch=None):
+    plan = boot.install_plan({"has_npm": True, "pkg_manager": "apt-get"})
+    assert plan and plan[0] == ["npm", "install", "-g", boot.CLAUDE_NPM_PACKAGE]
+    # no npm → distro node install then npm global
+    plan = boot.install_plan({"has_npm": False, "pkg_manager": "apk"})
+    assert ["apk", "add", "nodejs", "npm"] in plan
+    # explicit override wins and is the only command
+    import os
+    os.environ["HH_CLAUDE_INSTALL"] = "echo custom-install"
+    try:
+        plan = boot.install_plan({"has_npm": True})
+        assert plan == [["sh", "-c", "echo custom-install"]]
+    finally:
+        del os.environ["HH_CLAUDE_INSTALL"]
+
+
+def test_compose_directive_carries_objective_stop_budget():
+    d = boot.compose_directive(
+        "map the room and report", {"host": "h", "port": 9, "name": "scout"},
+        boot.Budget(depth=1, fanout=2, cost_usd=3.0), stop=["task done"])
+    assert "hh-operator skill" in d
+    assert "map the room and report" in d
+    assert "task done" in d
+    assert "depth=1" in d and "fanout=2" in d
+
+
+def test_plan_creds_gated_off_by_default():
+    off = boot.plan_creds("/tmp/child", allow=False)
+    assert off["staged"] is False and "gating on" in off["reason"]
+
+
+def test_build_run_argv_flags():
+    argv = boot.build_run_argv("do x", skip_permissions=True)
+    assert argv[:3] == ["claude", "-p", "do x"]
+    assert "--dangerously-skip-permissions" in argv
+    argv = boot.build_run_argv("do x")
+    assert "--dangerously-skip-permissions" not in argv
+
+
+# ── spawn op: gating + dry-run ────────────────────────────────────────────
+def test_spawn_dry_run_returns_plan_without_launch():
+    async def go():
+        b = _bridge("oracle")
+        b.budget = boot.Budget(depth=1, fanout=1, cost_usd=2.0)
+        r = await b._op_spawn({"objective": "scout the room",
+                               "room": {"host": "h", "port": 7, "name": "kid"},
+                               "dry_run": True})
+        assert r["ok"] and r["dry_run"] is True
+        assert r["plan"]["budget"] == {"depth": 0, "fanout": 1, "cost_usd": 2.0}
+        assert r["plan"]["creds"]["staged"] is False     # gated off
+        # dry-run must not consume the budget
+        assert b.budget.fanout == 1
+        # no spawn event emitted on a dry run
+        assert [e for e in b.events if e["kind"] == "spawn"] == []
+    asyncio.run(go())
+
+
+def test_spawn_refuses_without_objective_or_room_or_budget():
+    async def go():
+        b = _bridge("oracle")
+        assert (await b._op_spawn({"objective": ""}))["ok"] is False
+        assert (await b._op_spawn({"objective": "x"}))["ok"] is False  # no room
+        b.budget = boot.Budget(depth=0, fanout=0)
+        r = await b._op_spawn({"objective": "x",
+                               "room": {"host": "h", "port": 7}})
+        assert r["ok"] is False and "budget exhausted" in r["error"]
+    asyncio.run(go())