diff --git a/proxy.py b/proxy.py
index 72aa099..8f6cb81 100644
--- a/proxy.py
+++ b/proxy.py
@@ -666,6 +666,18 @@ def transform_messages_body(raw: bytes):
     model_before = body.get("model")
     route = {}
 
+    # 1M context window: Claude Code appends a "[1m]" suffix to a model id to ask
+    # the client for the 1M window (it also sends the context-1m beta header; see
+    # the launchers' UC_FORCE_1M / [1m] handling). That suffix is a client-side
+    # convention, not an Anthropic model id, so it must not reach routing (it would
+    # not match a configured route or an orchestrator/worker pick) or the upstream.
+    # Strip it up front so "<id>[1m]" behaves exactly like "<id>" everywhere below;
+    # the 1M window is unaffected because it rides the beta header, left untouched.
+    if isinstance(model_before, str) and model_before.endswith("[1m]"):
+        model_before = model_before[:-len("[1m]")]
+        body["model"] = model_before
+        changed = True
+
     # Orchestrator/Worker: classify tier and remap the model id to the selected
     # orchestrator (heavy) or worker (fast) model. This also captures the dynamic
     # workflow's stock-model background traffic so it follows your pick.
diff --git a/test_proxy.py b/test_proxy.py
index 3df40b0..702f608 100755
--- a/test_proxy.py
+++ b/test_proxy.py
@@ -263,6 +263,21 @@ def main():
         assert up._expand_env("Bearer ${MOCK_KEY}") == "Bearer secret123"
         print("[ok] ${ENV} expansion in route auth")
 
+        # PR #8 companion: Claude Code's [1m] context-window suffix on the model id
+        # is stripped before routing, so "<id>[1m]" still matches "<id>"'s route
+        # (the 1M window itself rides the context-1m beta header, not the id). A
+        # naive exact-match lookup would otherwise miss the route once the launcher
+        # appends [1m] to a 1M-capable Claude pick.
+        _saved_slots = up.UC_SLOT_MAP
+        up.UC_SLOT_MAP = {"claude-big": {"type": "openai_compat", "model": "big-real",
+                                         "upstream": mock + "/v1", "auth": "Bearer ${MOCK_KEY}"}}
+        out_1m, _ = up.transform_messages_body(json.dumps({
+            "model": "claude-big[1m]", "max_tokens": 8,
+            "messages": [{"role": "user", "content": "hi"}]}).encode())
+        assert json.loads(out_1m)["model"] == "big-real", json.loads(out_1m)["model"]
+        up.UC_SLOT_MAP = _saved_slots
+        print("[ok] 1M [1m] window suffix stripped before routing")
+
         # Stock Claude models: the built-in fallback so real Claude stays in
         # /model even with no upstream list. Toggle + override are honored, and
         # every advertised id obeys Claude Code's /^(claude|anthropic)/i rule.