diff --git a/docs/design/companion-process-manager.md b/docs/design/companion-process-manager.md
index 732ebd72..015c2721 100644
--- a/docs/design/companion-process-manager.md
+++ b/docs/design/companion-process-manager.md
@@ -664,8 +664,8 @@ No per-companion logic in Arbiter.
 
 ## 20. Implementation Tasks
 
-- [ ] Add companion config settings in `gunicorn/config.py`.
-- [ ] Add config validation for `companion_workers`.
+- [x] Add companion config settings in `gunicorn/config.py`.
+- [x] Add config validation for `companion_workers`.
 - [ ] Add `CompanionConfig` and config hash generation.
 - [ ] Add public process states.
 - [ ] Add `CompanionProcess` runtime state.
diff --git a/gunicorn/companion/__init__.py b/gunicorn/companion/__init__.py
new file mode 100644
index 00000000..9487cda3
--- /dev/null
+++ b/gunicorn/companion/__init__.py
@@ -0,0 +1,10 @@
+#
+# This file is part of gunicorn released under the MIT license.
+# See the NOTICE for more information.
+
+"""Companion process manager.
+
+Gunicorn manages one extra child, the Companion Manager, which manages all
+configured non-HTTP companion processes (RQ workers, scheduler, socket.io,
+custom daemons). See ``docs/design/companion-process-manager.md``.
+"""
diff --git a/gunicorn/companion/process.py b/gunicorn/companion/process.py
new file mode 100644
index 00000000..336701c6
--- /dev/null
+++ b/gunicorn/companion/process.py
@@ -0,0 +1,85 @@
+#
+# This file is part of gunicorn released under the MIT license.
+# See the NOTICE for more information.
+
+
+import hashlib
+import json
+
+# Public states, mimicking ``supervisorctl status``. The manager never
+# exposes EXITED/FATAL/UNKNOWN; an exited companion is either STOPPED (manual)
+# or BACKOFF (waiting to restart).
+STOPPED = "STOPPED"
+STARTING = "STARTING"
+RUNNING = "RUNNING"
+BACKOFF = "BACKOFF"
+STOPPING = "STOPPING"
+
+PUBLIC_STATES = (STOPPED, STARTING, RUNNING, BACKOFF, STOPPING)
+
+
+class CompanionConfig:
+    """Validated, normalized config for a single companion.
+
+    Built from one entry of ``companion_workers`` with global defaults already
+    applied. ``config_hash`` is a stable digest of every field; the manager
+    restarts a companion whenever its hash changes on reread.
+    """
+
+    def __init__(
+        self,
+        name,
+        target,
+        cwd=None,
+        env=None,
+        stop_signal="SIGTERM",
+        stop_timeout=60,
+        reload_timeout=60,
+        stdout=None,
+        stderr=None,
+        startsecs=1,
+    ):
+        self.name = name
+        self.target = target
+        self.cwd = cwd
+        self.env = dict(env or {})
+        self.stop_signal = stop_signal
+        self.stop_timeout = stop_timeout
+        self.reload_timeout = reload_timeout
+        self.stdout = stdout
+        self.stderr = stderr
+        self.startsecs = startsecs
+
+    def to_dict(self):
+        return {
+            "name": self.name,
+            "target": self.target,
+            "cwd": self.cwd,
+            "env": self.env,
+            "stop_signal": self.stop_signal,
+            "stop_timeout": self.stop_timeout,
+            "reload_timeout": self.reload_timeout,
+            "stdout": self.stdout,
+            "stderr": self.stderr,
+            "startsecs": self.startsecs,
+        }
+
+    @property
+    def config_hash(self):
+        # Sort keys so dict ordering never changes the digest. A callable
+        # target has no stable repr across runs, so use its qualified name.
+        data = self.to_dict()
+        data["target"] = self._target_key(self.target)
+        blob = json.dumps(data, sort_keys=True, default=str)
+        return hashlib.sha256(blob.encode("utf-8")).hexdigest()
+
+    @staticmethod
+    def _target_key(target):
+        if callable(target):
+            mod = getattr(target, "__module__", "")
+            qual = getattr(target, "__qualname__", repr(target))
+            return "%s:%s" % (mod, qual)
+        return str(target)
+
+    def __repr__(self):
+        return "<CompanionConfig %s>" % self.name