fix(claude): resolve Sonnet 5.x to adaptive thinking so no forged thinking placeholders are sent

open-sse/providers/capabilities.js

@@ -286,6 +286,7 @@ PROVIDER_CAPABILITIES.cx = PROVIDER_CAPABILITIES.codex;
 export const PATTERN_CAPABILITIES = [
   // ── Claude (4.6+ = adaptive thinking; older/haiku = budget) ──────
   { pattern: "*claude*opus-5*",     caps: { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 } },
+  { pattern: "*claude*sonnet-5*",   caps: { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive", contextWindow: 1000000, maxOutput: 128000 } },
   { pattern: "*claude*opus-4.6*",   caps: { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive" } },
   { pattern: "*claude*opus-4.7*",   caps: { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive" } },
   { pattern: "*claude*opus-4.8*",   caps: { vision: true, reasoning: true, search: true, thinkingFormat: "claude-adaptive" } },

tests/unit/capabilities-sonnet-5-5.test.js

@@ -0,0 +1,21 @@
+import { describe, expect, it } from "vitest";
+
+import { getCapabilitiesForModel } from "../../open-sse/providers/capabilities.js";
+
+// claude-sonnet-5-5 has no exact entry and matched only the generic *claude*sonnet*
+// pattern (claude-budget). That sent thinking.type "enabled" and made the translator
+// forge signed thinking placeholders on every tool_use turn; Sonnet 5.5 answered
+// large Codex conversations with stop_reason "refusal". It must resolve like the
+// rest of the 5.x family: adaptive thinking, 1M context.
+describe("Claude Sonnet 5.5 capabilities", () => {
+  for (const model of ["claude-sonnet-5-5", "claude-sonnet-5.5", "anthropic/claude-sonnet-5-5"]) {
+    it(`${model} resolves to adaptive thinking + 1M context`, () => {
+      expect(getCapabilitiesForModel("claude", model)).toMatchObject({
+        thinkingFormat: "claude-adaptive",
+        contextWindow: 1000000,
+        maxOutput: 128000,
+        reasoning: true,
+      });
+    });
+  }
+});