feat(thinking): return Claude thinking text to OpenAI-format clients

tests/translator/__snapshots__/golden-request.test.js.snap

@@ -119,6 +119,7 @@ exports[`GOLDEN request: OpenAI → Claude > reasoning_effort → adaptive outpu
     },
   ],
   "thinking": {
+    "display": "summarized",
     "type": "adaptive",
   },
 }

tests/translator/openai-thinking-display.test.js

@@ -0,0 +1,83 @@
+// OpenAI-format clients asking for reasoning get Claude's thinking text back.
+//
+// Claude only returns thinking text when the request sets thinking.display to
+// "summarized" — otherwise the redact-thinking beta is sent and every thinking
+// block comes back signature-only. That field has no OpenAI equivalent, so an
+// OpenAI-format client (opencode, DeepSeek Harness, Cherry Studio, ...) could never
+// see its reasoning: reasoning_content stayed empty however high the effort was.
+//
+// The client's intent is read from the pre-translation body:
+// - Chat Completions: setting reasoning_effort is the request for reasoning.
+// - Responses API: reasoning.summary is OpenAI's explicit ask for summaries.
+// Claude-format clients are untouched — they set display themselves.
+import { describe, it, expect } from "vitest";
+import "./registerAll.js";
+import { translateRequest } from "../../open-sse/translator/index.js";
+import { FORMATS } from "../../open-sse/translator/formats.js";
+import { selectAnthropicBeta } from "../../open-sse/providers/shared.js";
+
+const REDACT = "redact-thinking-2026-02-12";
+const MODEL = "claude-opus-5";
+
+function toClaude(sourceFormat, body) {
+  return translateRequest(sourceFormat, FORMATS.CLAUDE, MODEL, body, true, null, "claude");
+}
+
+const chat = (extra = {}) => ({ model: MODEL, messages: [{ role: "user", content: "Is 391 prime?" }], ...extra });
+const responses = (extra = {}) => ({ model: MODEL, input: [{ role: "user", content: "Is 391 prime?" }], ...extra });
+
+describe("Chat Completions clients", () => {
+  it("reasoning_effort asks Claude for summarized thinking and drops redact-thinking", () => {
+    const out = toClaude(FORMATS.OPENAI, chat({ reasoning_effort: "high" }));
+    expect(out.thinking.display).toBe("summarized");
+    expect(selectAnthropicBeta(MODEL, out)).not.toContain(REDACT);
+  });
+
+  it("reasoning_effort none leaves thinking off and keeps redact-thinking", () => {
+    const out = toClaude(FORMATS.OPENAI, chat({ reasoning_effort: "none" }));
+    expect(out.thinking?.display).toBeUndefined();
+    expect(selectAnthropicBeta(MODEL, out)).toContain(REDACT);
+  });
+
+  it("no reasoning_effort changes nothing", () => {
+    const out = toClaude(FORMATS.OPENAI, chat());
+    expect(out.thinking?.display).toBeUndefined();
+    expect(selectAnthropicBeta(MODEL, out)).toContain(REDACT);
+  });
+});
+
+describe("Responses API clients", () => {
+  it("reasoning.summary asks Claude for summarized thinking", () => {
+    const out = toClaude(FORMATS.OPENAI_RESPONSES, responses({ reasoning: { effort: "high", summary: "auto" } }));
+    expect(out.thinking.display).toBe("summarized");
+    expect(selectAnthropicBeta(MODEL, out)).not.toContain(REDACT);
+  });
+
+  it("effort without summary keeps thinking text redacted, as OpenAI would", () => {
+    const out = toClaude(FORMATS.OPENAI_RESPONSES, responses({ reasoning: { effort: "high" } }));
+    expect(out.thinking?.display).toBeUndefined();
+    expect(selectAnthropicBeta(MODEL, out)).toContain(REDACT);
+  });
+});
+
+describe("Claude-format clients are untouched", () => {
+  it("thinking without display stays redacted", () => {
+    const out = toClaude(FORMATS.CLAUDE, {
+      model: MODEL, max_tokens: 4096,
+      thinking: { type: "enabled", budget_tokens: 2048 },
+      messages: [{ role: "user", content: "Is 391 prime?" }],
+    });
+    expect(out.thinking?.display).toBeUndefined();
+    expect(selectAnthropicBeta(MODEL, out)).toContain(REDACT);
+  });
+
+  it("an explicit display is kept as sent", () => {
+    const out = toClaude(FORMATS.CLAUDE, {
+      model: MODEL, max_tokens: 4096,
+      thinking: { type: "enabled", budget_tokens: 2048, display: "omitted" },
+      messages: [{ role: "user", content: "Is 391 prime?" }],
+    });
+    expect(out.thinking.display).toBe("omitted");
+    expect(selectAnthropicBeta(MODEL, out)).toContain(REDACT);
+  });
+});