diff --git a/.github/workflows/release.yaml b/.github/workflows/release.yaml
index 4043e4a5dd..4722e45e76 100644
--- a/.github/workflows/release.yaml
+++ b/.github/workflows/release.yaml
@@ -20,6 +20,37 @@ jobs:
         run: |
           git fetch --depth 1 https://github.com/router-for-me/models.git main
           git show FETCH_HEAD:models.json > internal/registry/models/models.json
+      - name: Strip Claude entries from antigravity catalog (ampeco Patch 4)
+        # Antigravity's published catalog advertises Claude models served by
+        # Google's cloudcode-pa.googleapis.com. With those entries present, an
+        # antigravity OAuth becomes eligible alongside the Anthropic OAuth pool
+        # for `claude-*` selector picks. Session-affinity then pins entire
+        # Claude Code sessions (parent + sub-agents) to the antigravity OAuth
+        # whenever the parent request was a Gemini call, exhausting
+        # Antigravity's small Sonnet quota within hours. Strip them post-refresh
+        # so the antigravity OAuth is Gemini-only.
+        run: |
+          python3 - <<'PY'
+          import json
+          p = "internal/registry/models/models.json"
+          with open(p) as f:
+              d = json.load(f)
+          if "antigravity" in d:
+              before = len(d["antigravity"])
+              d["antigravity"] = [
+                  m for m in d["antigravity"]
+                  if not (
+                      m.get("id", "").startswith("claude-")
+                      or m.get("type", "") == "claude"
+                      or m.get("owned_by", "") == "anthropic"
+                  )
+              ]
+              after = len(d["antigravity"])
+              print(f"antigravity catalog: {before} -> {after} entries ({before - after} claude stripped)")
+          with open(p, "w") as f:
+              json.dump(d, f, indent=2)
+              f.write("\n")
+          PY
       - run: git fetch --force --tags
       - uses: actions/setup-go@v4
         with:
diff --git a/README.md b/README.md
index 9d6ce7d505..df9e32d00e 100644
--- a/README.md
+++ b/README.md
@@ -24,11 +24,20 @@ Remove `cache_control` from `messages[].content[]`, `system[]`, `tools[]`, and m
 
 When the credential's API key starts with `sk-ant-oat01-`, route via `Authorization: Bearer …` instead of `x-api-key`. Real `sk-ant-api03-*` API keys keep the existing `x-api-key` routing.
 
+### Patch 4 — strip Claude entries from the `antigravity` model catalog
+
+`internal/registry/models/models.json` and `.github/workflows/release.yaml` (post-refresh step).
+
+Antigravity's published catalog includes `claude-opus-4-6-thinking` and `claude-sonnet-4-6` because Google's AI Code Assist tier resells Claude models via `cloudcode-pa.googleapis.com`. With those entries present, an antigravity OAuth becomes eligible alongside the Anthropic OAuth pool when the selector picks for `claude-*` routes. Session-affinity then pins entire Claude Code sessions (parent + sub-agents) to the antigravity OAuth whenever the parent request was a Gemini call, exhausting Antigravity's small Sonnet quota within hours.
+
+Strip every entry whose `id` starts with `claude-`, whose `type` is `claude`, or whose `owned_by` is `anthropic` from the `antigravity` array. Applied both to the in-tree `models.json` (so `go test ./...` and local dev see the patched shape) and to the release workflow's post-refresh step (so upstream catalog refreshes during tagged builds re-apply the strip automatically). After the patch the antigravity OAuth is Gemini-only and Claude requests fall through to the Anthropic OAuth pool.
+
 ## Tests
 
 ```bash
 go test ./internal/translator/openai/claude/...                                                     # Patches 1 + 2
 go test ./internal/runtime/executor/ -run 'OAuthAccessTokenUsesBearerAuth|ApiKeyStillUsesXApiKey'   # Patch 3
+go test ./internal/registry/...                                                                     # Patch 4 (catalog integrity)
 ```
 
 ## Rebase
diff --git a/internal/registry/models/models.json b/internal/registry/models/models.json
index fa56bb42a2..1d374e1f27 100644
--- a/internal/registry/models/models.json
+++ b/internal/registry/models/models.json
@@ -1874,40 +1874,6 @@
     }
   ],
   "antigravity": [
-    {
-      "id": "claude-opus-4-6-thinking",
-      "object": "model",
-      "owned_by": "antigravity",
-      "type": "antigravity",
-      "display_name": "Claude Opus 4.6 (Thinking)",
-      "name": "claude-opus-4-6-thinking",
-      "description": "Claude Opus 4.6 (Thinking)",
-      "context_length": 200000,
-      "max_completion_tokens": 64000,
-      "thinking": {
-        "min": 1024,
-        "max": 64000,
-        "zero_allowed": true,
-        "dynamic_allowed": true
-      }
-    },
-    {
-      "id": "claude-sonnet-4-6",
-      "object": "model",
-      "owned_by": "antigravity",
-      "type": "antigravity",
-      "display_name": "Claude Sonnet 4.6 (Thinking)",
-      "name": "claude-sonnet-4-6",
-      "description": "Claude Sonnet 4.6 (Thinking)",
-      "context_length": 200000,
-      "max_completion_tokens": 64000,
-      "thinking": {
-        "min": 1024,
-        "max": 64000,
-        "zero_allowed": true,
-        "dynamic_allowed": true
-      }
-    },
     {
       "id": "gemini-3-flash",
       "object": "model",