diff --git a/src/ucode/agents/claude.py b/src/ucode/agents/claude.py
index 2f79f7d..73204f5 100644
--- a/src/ucode/agents/claude.py
+++ b/src/ucode/agents/claude.py
@@ -106,6 +106,13 @@ def render_overlay(
         "ANTHROPIC_BASE_URL": base_url,
         "ANTHROPIC_CUSTOM_HEADERS": custom_headers,
         "CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS": "1",
+        # Suppress Claude Code's client-side `thinking.type=enabled` field.
+        # The Databricks AI Gateway rejects it for adaptive-only models (Opus 4.7
+        # family) which require `thinking.type=adaptive` + `output_config.effort`.
+        # Claude Code's model detection doesn't recognize the `databricks-` prefix
+        # on gateway model ids, so it sends the legacy shape and the request 400s.
+        # The gateway still applies adaptive reasoning server-side where required.
+        "CLAUDE_CODE_DISABLE_THINKING": "1",
         "CLAUDE_CODE_API_KEY_HELPER_TTL_MS": "900000",
     }
     if claude_models:
diff --git a/tests/test_agent_claude.py b/tests/test_agent_claude.py
index 07d337b..d311b28 100644
--- a/tests/test_agent_claude.py
+++ b/tests/test_agent_claude.py
@@ -37,6 +37,18 @@ def test_disables_experimental_betas(self):
         overlay, _ = claude.render_overlay(WS, "s4")
         assert overlay["env"]["CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS"] == "1"
 
+    def test_disables_thinking(self):
+        # Claude Code's `thinking.type=enabled` field is rejected by the
+        # Databricks AI Gateway for adaptive-only models (Opus 4.7 family).
+        # The gateway applies adaptive reasoning server-side regardless, so
+        # ucode disables Claude Code's client-side thinking unconditionally.
+        overlay, _ = claude.render_overlay(WS, "s4")
+        assert overlay["env"]["CLAUDE_CODE_DISABLE_THINKING"] == "1"
+
+    def test_disable_thinking_is_managed(self):
+        _, keys = claude.render_overlay(WS, "s4")
+        assert ["env", "CLAUDE_CODE_DISABLE_THINKING"] in keys
+
     def test_sets_api_key_helper(self):
         overlay, _ = claude.render_overlay(WS, "s4")
         assert "apiKeyHelper" in overlay