diff --git a/claude_bottle/backend/docker/backend.py b/claude_bottle/backend/docker/backend.py
index 3f97db3..b848337 100644
--- a/claude_bottle/backend/docker/backend.py
+++ b/claude_bottle/backend/docker/backend.py
@@ -35,6 +35,7 @@ from .pipelock import (
     pipelock_proxy_host_port,
     pipelock_proxy_url,
 )
+from .provision import prompt as _prompt
 
 
 # Where the repo root lives, for `docker build` context. Computed once.
@@ -282,35 +283,8 @@ class DockerBottleBackend(BottleBackend):
             info(f"name conflict; retrying as {container}")
 
     def provision_prompt(self, plan: BottlePlan, target: str) -> str | None:
-        """Copy the prompt file into the container, fix ownership/mode.
-        Returns the in-container path if the agent has a non-empty
-        prompt (drives --append-system-prompt-file), else None. The
-        file is copied either way so the path always exists."""
         assert isinstance(plan, DockerBottlePlan)
-        container = target
-        container_home = os.environ.get("CLAUDE_BOTTLE_CONTAINER_HOME", "/home/node")
-        in_container_prompt_path = f"{container_home}/.claude-bottle-prompt.txt"
-
-        subprocess.run(
-            ["docker", "cp", str(plan.prompt_file), f"{container}:{in_container_prompt_path}"],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-        # `docker cp` preserves host UID; re-own/mode as root so node
-        # can read its own mode-600 prompt regardless of host UID.
-        subprocess.run(
-            ["docker", "exec", "-u", "0", container, "chown", "node:node", in_container_prompt_path],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-        subprocess.run(
-            ["docker", "exec", "-u", "0", container, "chmod", "600", in_container_prompt_path],
-            stdout=subprocess.DEVNULL,
-            check=True,
-        )
-
-        agent = plan.spec.manifest.agents[plan.spec.agent_name]
-        return in_container_prompt_path if agent.prompt else None
+        return _prompt.provision_prompt(plan, target)
 
     def validate_skills(self, skills: list[str]) -> None:
         """Fail loudly if any named skill is missing from the host's
diff --git a/claude_bottle/backend/docker/provision/__init__.py b/claude_bottle/backend/docker/provision/__init__.py
new file mode 100644
index 0000000..2f66425
--- /dev/null
+++ b/claude_bottle/backend/docker/provision/__init__.py
@@ -0,0 +1,8 @@
+"""Per-provisioner modules for the Docker backend.
+
+Each module exports one top-level function:
+    provision_<thing>(plan: DockerBottlePlan, target: str) -> ...
+
+`DockerBottleBackend.provision_*` methods delegate to these. The
+abstract `BottleBackend.provision_*` surface is unchanged; this
+subpackage exists only to keep `backend.py` from being a god-file."""
diff --git a/claude_bottle/backend/docker/provision/prompt.py b/claude_bottle/backend/docker/provision/prompt.py
new file mode 100644
index 0000000..29df62c
--- /dev/null
+++ b/claude_bottle/backend/docker/provision/prompt.py
@@ -0,0 +1,43 @@
+"""Copy the agent prompt into a running Docker bottle.
+
+The prompt file is always copied (so the in-container path always
+exists) but `--append-system-prompt-file` only fires when the agent
+actually has a prompt — the return value signals which case."""
+
+from __future__ import annotations
+
+import os
+import subprocess
+
+from ..bottle_plan import DockerBottlePlan
+
+
+def provision_prompt(plan: DockerBottlePlan, target: str) -> str | None:
+    """Copy the prompt file into the container, fix ownership/mode.
+    Returns the in-container path if the agent has a non-empty
+    prompt (drives --append-system-prompt-file), else None. The
+    file is copied either way so the path always exists."""
+    container = target
+    container_home = os.environ.get("CLAUDE_BOTTLE_CONTAINER_HOME", "/home/node")
+    in_container_prompt_path = f"{container_home}/.claude-bottle-prompt.txt"
+
+    subprocess.run(
+        ["docker", "cp", str(plan.prompt_file), f"{container}:{in_container_prompt_path}"],
+        stdout=subprocess.DEVNULL,
+        check=True,
+    )
+    # `docker cp` preserves host UID; re-own/mode as root so node
+    # can read its own mode-600 prompt regardless of host UID.
+    subprocess.run(
+        ["docker", "exec", "-u", "0", container, "chown", "node:node", in_container_prompt_path],
+        stdout=subprocess.DEVNULL,
+        check=True,
+    )
+    subprocess.run(
+        ["docker", "exec", "-u", "0", container, "chmod", "600", in_container_prompt_path],
+        stdout=subprocess.DEVNULL,
+        check=True,
+    )
+
+    agent = plan.spec.manifest.agents[plan.spec.agent_name]
+    return in_container_prompt_path if agent.prompt else None