fix(claude): preserve signed thinking turns during obfuscation (#8629)

Validated in local merge-train T6 (ungrouped batch 1)

tests/unit/claude-code-obfuscation.test.ts

@@ -0,0 +1,30 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+const { obfuscateInBody } = await import("../../open-sse/services/claudeCodeObfuscation.ts");
+
+test("obfuscateInBody preserves a turn that carries signed thinking", () => {
+  const body = {
+    messages: [
+      {
+        role: "assistant",
+        content: [
+          { type: "thinking", thinking: "private", signature: "signed-by-anthropic" },
+          { type: "text", text: "I used opencode to inspect it." },
+        ],
+      },
+    ],
+  };
+
+  obfuscateInBody(body);
+  assert.equal((body.messages[0].content[1] as { text: string }).text, "I used opencode to inspect it.");
+});
+
+test("obfuscateInBody still obfuscates an unsigned normal text turn", () => {
+  const body = {
+    messages: [{ role: "assistant", content: [{ type: "text", text: "I used opencode." }] }],
+  };
+
+  obfuscateInBody(body);
+  assert.notEqual((body.messages[0].content[0] as { text: string }).text, "I used opencode.");
+});

tests/unit/system-transforms.test.ts

@@ -145,6 +145,25 @@ test("obfuscate_words with empty list is a no-op", () => {
   assert.equal((body.system[0] as { text: string }).text, "opencode");
 });
 
+test("obfuscate_words preserves a message turn with signed thinking", () => {
+  const body = {
+    messages: [
+      {
+        role: "assistant",
+        content: [
+          { type: "thinking", thinking: "private", signature: "signed-by-anthropic" },
+          { type: "text", text: "opencode remains unchanged" },
+        ],
+      },
+    ],
+  };
+  applyTransformPipeline(body, [{ kind: "obfuscate_words", words: ["opencode"] }]);
+  assert.equal(
+    (body.messages[0].content[1] as { text: string }).text,
+    "opencode remains unchanged"
+  );
+});
+
 // ────────────────────────────────────────────────────────────────────────────
 // Pipeline ordering: drop paragraph then obfuscate what survives
 // ────────────────────────────────────────────────────────────────────────────