diff --git a/cc-ci-plan/launch-upgrader.py b/cc-ci-plan/launch-upgrader.py
index c4f50ca..9ccf109 100644
--- a/cc-ci-plan/launch-upgrader.py
+++ b/cc-ci-plan/launch-upgrader.py
@@ -14,10 +14,11 @@ Usage:
   launch-upgrader.py attach   tmux attach to the session
 
 Env:
-  LOOP_BACKEND     claude (default) | opencode   — also accepts UPGRADER_BACKEND
-  LOOP_MODEL       model flag (overrides UPGRADER_MODEL)
-  UPGRADER_MODEL   sonnet (default for claude) | provider/model for opencode, e.g.
-                   opencode-go/glm-5.2 (OpenCode Go subscription) or tinfoil/deepseek-v4-pro
+  LOOP_BACKEND     opencode (default) | claude   — also accepts UPGRADER_BACKEND
+  LOOP_MODEL       model flag (overrides UPGRADER_MODEL); default tracks backend —
+                   opencode→opencode-go/glm-5.2, claude→sonnet
+  UPGRADER_MODEL   provider/model for opencode, e.g. opencode-go/glm-5.2 (OpenCode Go
+                   subscription) or tinfoil/deepseek-v4-pro; sonnet etc. for claude
   UPGRADER_ARGS    extra args passed to /upgrade-all (e.g. "n8n ghost", "--dry-run")
 
   claude backend:
@@ -37,8 +38,12 @@ WORKDIR = os.environ.get("UPGRADER_DIR",     "/srv/cc-ci")
 LOG_DIR = os.environ.get("LOG_DIR",          "/srv/cc-ci/.cc-ci-logs")
 
 # LOOP_BACKEND / LOOP_MODEL take precedence (unified control from the operator).
-BACKEND = os.environ.get("LOOP_BACKEND", os.environ.get("UPGRADER_BACKEND", "claude"))
-MODEL   = os.environ.get("LOOP_MODEL",   os.environ.get("UPGRADER_MODEL",   "sonnet"))
+# Default backend+model is the OpenCode Go subscription on glm-5.2; override either via env.
+# The model default tracks the backend so an explicit `LOOP_BACKEND=claude` (without a model)
+# still gets a sensible claude model rather than a glm id.
+BACKEND = os.environ.get("LOOP_BACKEND", os.environ.get("UPGRADER_BACKEND", "opencode"))
+_DEFAULT_MODEL = "opencode-go/glm-5.2" if BACKEND == "opencode" else "sonnet"
+MODEL   = os.environ.get("LOOP_MODEL",   os.environ.get("UPGRADER_MODEL",   _DEFAULT_MODEL))
 
 CLAUDE_BIN     = os.environ.get("CLAUDE_BIN",   "claude")
 CLAUDE_FLAGS   = os.environ.get("CLAUDE_FLAGS", "--dangerously-skip-permissions")