diff --git a/open-sse/services/codexVerbosity.ts b/open-sse/services/codexVerbosity.ts
index 8b530038c6..96cc441faa 100644
--- a/open-sse/services/codexVerbosity.ts
+++ b/open-sse/services/codexVerbosity.ts
@@ -9,9 +9,8 @@
  *
  * This helper runs on the translated path (before the allowlist) and folds whichever
  * shape arrived into a single, validated `text:{verbosity}`. `text` is then added to
- * the allowlist so the hint survives. Non-verbosity `text` keys (e.g. a stray
- * `text.format`) are intentionally dropped — they were already stripped by the
- * pre-existing allowlist, so this preserves the status quo while adding verbosity.
+ * the allowlist so the hint survives. Other Responses `text` keys, such as
+ * `text.format` for structured output, are preserved.
  *
  * Ref: OpenAI GPT-5 docs (text.verbosity), Azure Foundry reasoning guide.
  */
@@ -33,8 +32,8 @@ function normalizeLevel(value: unknown): string | undefined {
 /**
  * Mutates `body` in place: resolves verbosity from `text.verbosity` (Responses) or
  * the top-level `verbosity` (Chat Completions, which takes precedence when both are
- * present), drops the Chat-only top-level field, and collapses `text` to
- * `{verbosity}` when valid or removes it otherwise.
+ * present), drops the Chat-only top-level field, and preserves any other existing
+ * Responses `text` configuration.
  */
 export function normalizeCodexVerbosity(body: Record<string, unknown>): void {
   const textRecord = asRecord(body.text);
@@ -45,8 +44,15 @@ export function normalizeCodexVerbosity(body: Record<string, unknown>): void {
 
   delete body.verbosity;
 
+  const nextText = textRecord ? { ...textRecord } : {};
   if (verbosity) {
-    body.text = { verbosity };
+    nextText.verbosity = verbosity;
+  } else {
+    delete nextText.verbosity;
+  }
+
+  if (Object.keys(nextText).length > 0) {
+    body.text = nextText;
   } else {
     delete body.text;
   }
diff --git a/open-sse/translator/request/openai-responses/toResponses.ts b/open-sse/translator/request/openai-responses/toResponses.ts
index 5cb12419f5..d52608496f 100644
--- a/open-sse/translator/request/openai-responses/toResponses.ts
+++ b/open-sse/translator/request/openai-responses/toResponses.ts
@@ -17,6 +17,28 @@ import {
   normalizeResponsesReasoningEffort,
 } from "./helpers.ts";
 
+// Chat Completions `response_format: { type: "json_schema" }` → Responses API `text.format`.
+// Merges into any existing `result.text` (e.g. verbosity) so structured-output schemas from
+// Chat clients survive the translation to the Responses/Codex upstream (#5933).
+function mapChatResponseFormatToResponsesText(body: JsonRecord, result: JsonRecord): void {
+  const responseFormat = toRecord(body.response_format);
+  if (responseFormat.type !== "json_schema") return;
+
+  const jsonSchema = toRecord(responseFormat.json_schema);
+  if (jsonSchema.schema === undefined) return;
+
+  const existingText = toRecord(result.text);
+  const format: JsonRecord = {
+    type: "json_schema",
+    name: toString(jsonSchema.name, "codex_output_schema"),
+    schema: jsonSchema.schema,
+  };
+  if (jsonSchema.description !== undefined) format.description = jsonSchema.description;
+  if (jsonSchema.strict !== undefined) format.strict = jsonSchema.strict;
+
+  result.text = { ...existingText, format };
+}
+
 export function openaiToOpenAIResponsesRequest(
   model: unknown,
   body: unknown,
@@ -301,6 +323,7 @@ export function openaiToOpenAIResponsesRequest(
     result.max_output_tokens = root.max_tokens;
   }
   if (root.top_p !== undefined) result.top_p = root.top_p;
+  mapChatResponseFormatToResponsesText(root, result);
   // GPT-5 verbosity: Chat Completions `verbosity` → Responses `text.verbosity`.
   const chatVerbosity = normalizeVerbosity(root.verbosity);
   if (chatVerbosity) {
diff --git a/tests/unit/codex-verbosity.test.ts b/tests/unit/codex-verbosity.test.ts
index b23814c04d..7869f5aea9 100644
--- a/tests/unit/codex-verbosity.test.ts
+++ b/tests/unit/codex-verbosity.test.ts
@@ -37,10 +37,19 @@ test("invalid verbosity is dropped and text removed", () => {
   assert.equal(body.verbosity, undefined);
 });
 
-test("no verbosity + stray non-verbosity text → text removed (status quo)", () => {
-  const body: Record<string, unknown> = { text: { format: { type: "json" } }, input: [] };
+test("no verbosity + Responses text.format is preserved", () => {
+  const format = { type: "json_schema", name: "schema", schema: { type: "object" } };
+  const body: Record<string, unknown> = { text: { format }, input: [] };
   normalizeCodexVerbosity(body);
-  assert.equal(body.text, undefined);
+  assert.deepEqual(body.text, { format });
+});
+
+test("verbosity is merged with existing Responses text.format", () => {
+  const format = { type: "json_schema", name: "schema", schema: { type: "object" } };
+  const body: Record<string, unknown> = { verbosity: "low", text: { format }, input: [] };
+  normalizeCodexVerbosity(body);
+  assert.deepEqual(body.text, { format, verbosity: "low" });
+  assert.equal(body.verbosity, undefined);
 });
 
 test("verbosity is normalized case-insensitively", () => {
diff --git a/tests/unit/translator-openai-responses-req.test.ts b/tests/unit/translator-openai-responses-req.test.ts
index 705ff6c38f..87e5c97f43 100644
--- a/tests/unit/translator-openai-responses-req.test.ts
+++ b/tests/unit/translator-openai-responses-req.test.ts
@@ -393,6 +393,81 @@ test("Chat -> Responses converts messages, tool calls, tool outputs, tools and p
   assert.equal((result as any).top_p, 0.9);
 });
 
+test("Chat -> Responses converts json_schema response_format to text.format", () => {
+  const schema = {
+    type: "object",
+    additionalProperties: false,
+    properties: { answer: { type: "string" } },
+    required: ["answer"],
+  };
+
+  const result = openaiToOpenAIResponsesRequest(
+    "gpt-5.2-codex",
+    {
+      messages: [{ role: "user", content: "Return the answer as JSON" }],
+      response_format: {
+        type: "json_schema",
+        json_schema: {
+          name: "answer_schema",
+          description: "A structured answer",
+          strict: true,
+          schema,
+        },
+      },
+    },
+    false,
+    null
+  ) as any;
+
+  assert.deepEqual(result.text, {
+    format: {
+      type: "json_schema",
+      name: "answer_schema",
+      description: "A structured answer",
+      strict: true,
+      schema,
+    },
+  });
+  assert.equal(result.response_format, undefined);
+});
+
+test("Chat -> Responses uses response_format over nonstandard chat text.format", () => {
+  const result = openaiToOpenAIResponsesRequest(
+    "gpt-5.2-codex",
+    {
+      messages: [{ role: "user", content: "Return JSON" }],
+      text: {
+        format: { type: "json_schema", name: "nonstandard", schema: { type: "object" } },
+        verbosity: "low",
+      },
+      response_format: {
+        type: "json_schema",
+        json_schema: { name: "chat", schema: { type: "object", properties: {} } },
+      },
+    },
+    false,
+    null
+  ) as any;
+
+  assert.deepEqual(result.text, {
+    format: { type: "json_schema", name: "chat", schema: { type: "object", properties: {} } },
+  });
+});
+
+test("Chat -> Responses ignores nonstandard chat text.format without response_format", () => {
+  const result = openaiToOpenAIResponsesRequest(
+    "gpt-5.2-codex",
+    {
+      messages: [{ role: "user", content: "Return JSON" }],
+      text: { format: { type: "json_schema", name: "nonstandard", schema: { type: "object" } } },
+    },
+    false,
+    null
+  ) as any;
+
+  assert.equal(result.text, undefined);
+});
+
 test("Responses round-trip preserves store and previous_response_id when opt-in is enabled", () => {
   const credentials = {
     providerSpecificData: {