diff --git a/codex-rs/app-server-protocol/schema/json/ClientRequest.json b/codex-rs/app-server-protocol/schema/json/ClientRequest.json
index ee68faf001aa..788e52e82be0 100644
--- a/codex-rs/app-server-protocol/schema/json/ClientRequest.json
+++ b/codex-rs/app-server-protocol/schema/json/ClientRequest.json
@@ -984,6 +984,26 @@
           ],
           "title": "InputImageFunctionCallOutputContentItem",
           "type": "object"
+        },
+        {
+          "properties": {
+            "encrypted_content": {
+              "type": "string"
+            },
+            "type": {
+              "enum": [
+                "encrypted_content"
+              ],
+              "title": "EncryptedContentFunctionCallOutputContentItemType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "encrypted_content",
+            "type"
+          ],
+          "title": "EncryptedContentFunctionCallOutputContentItem",
+          "type": "object"
         }
       ]
     },
diff --git a/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json b/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json
index 3db4a87ef24b..f6e5a46c95de 100644
--- a/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json
+++ b/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json
@@ -9242,6 +9242,26 @@
             ],
             "title": "InputImageFunctionCallOutputContentItem",
             "type": "object"
+          },
+          {
+            "properties": {
+              "encrypted_content": {
+                "type": "string"
+              },
+              "type": {
+                "enum": [
+                  "encrypted_content"
+                ],
+                "title": "EncryptedContentFunctionCallOutputContentItemType",
+                "type": "string"
+              }
+            },
+            "required": [
+              "encrypted_content",
+              "type"
+            ],
+            "title": "EncryptedContentFunctionCallOutputContentItem",
+            "type": "object"
           }
         ]
       },
diff --git a/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json b/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json
index 7b62d6d4bf86..c4e93338a1f3 100644
--- a/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json
+++ b/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json
@@ -5631,6 +5631,26 @@
           ],
           "title": "InputImageFunctionCallOutputContentItem",
           "type": "object"
+        },
+        {
+          "properties": {
+            "encrypted_content": {
+              "type": "string"
+            },
+            "type": {
+              "enum": [
+                "encrypted_content"
+              ],
+              "title": "EncryptedContentFunctionCallOutputContentItemType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "encrypted_content",
+            "type"
+          ],
+          "title": "EncryptedContentFunctionCallOutputContentItem",
+          "type": "object"
         }
       ]
     },
diff --git a/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json b/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json
index 74420ea57e05..e69b342282c3 100644
--- a/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json
+++ b/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json
@@ -140,6 +140,26 @@
           ],
           "title": "InputImageFunctionCallOutputContentItem",
           "type": "object"
+        },
+        {
+          "properties": {
+            "encrypted_content": {
+              "type": "string"
+            },
+            "type": {
+              "enum": [
+                "encrypted_content"
+              ],
+              "title": "EncryptedContentFunctionCallOutputContentItemType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "encrypted_content",
+            "type"
+          ],
+          "title": "EncryptedContentFunctionCallOutputContentItem",
+          "type": "object"
         }
       ]
     },
diff --git a/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json b/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json
index 027989479a97..d4bdeda0ed3b 100644
--- a/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json
+++ b/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json
@@ -199,6 +199,26 @@
           ],
           "title": "InputImageFunctionCallOutputContentItem",
           "type": "object"
+        },
+        {
+          "properties": {
+            "encrypted_content": {
+              "type": "string"
+            },
+            "type": {
+              "enum": [
+                "encrypted_content"
+              ],
+              "title": "EncryptedContentFunctionCallOutputContentItemType",
+              "type": "string"
+            }
+          },
+          "required": [
+            "encrypted_content",
+            "type"
+          ],
+          "title": "EncryptedContentFunctionCallOutputContentItem",
+          "type": "object"
         }
       ]
     },
diff --git a/codex-rs/app-server-protocol/schema/typescript/FunctionCallOutputContentItem.ts b/codex-rs/app-server-protocol/schema/typescript/FunctionCallOutputContentItem.ts
index fb2996f1e54a..cd18908145a0 100644
--- a/codex-rs/app-server-protocol/schema/typescript/FunctionCallOutputContentItem.ts
+++ b/codex-rs/app-server-protocol/schema/typescript/FunctionCallOutputContentItem.ts
@@ -7,4 +7,4 @@ import type { ImageDetail } from "./ImageDetail";
  * Responses API compatible content items that can be returned by a tool call.
  * This is a subset of ContentItem with the types we support as function call outputs.
  */
-export type FunctionCallOutputContentItem = { "type": "input_text", text: string, } | { "type": "input_image", image_url: string, detail?: ImageDetail, };
+export type FunctionCallOutputContentItem = { "type": "input_text", text: string, } | { "type": "input_image", image_url: string, detail?: ImageDetail, } | { "type": "encrypted_content", encrypted_content: string, };
diff --git a/codex-rs/core/src/context_manager/history.rs b/codex-rs/core/src/context_manager/history.rs
index cfd929738206..6a0553548860 100644
--- a/codex-rs/core/src/context_manager/history.rs
+++ b/codex-rs/core/src/context_manager/history.rs
@@ -504,6 +504,10 @@ fn estimate_reasoning_length(encoded_len: usize) -> usize {
         .saturating_sub(650)
 }
 
+fn estimate_encrypted_function_output_length(encoded_len: usize) -> usize {
+    encoded_len.saturating_mul(9).div_ceil(16)
+}
+
 fn estimate_item_token_count(item: &ResponseItem) -> i64 {
     let model_visible_bytes = estimate_response_item_model_visible_bytes(item);
     approx_tokens_from_byte_count_i64(model_visible_bytes)
@@ -547,16 +551,18 @@ pub(crate) fn estimate_response_item_model_visible_bytes(item: &ResponseItem) ->
             let raw = serde_json::to_string(item)
                 .map(|serialized| i64::try_from(serialized.len()).unwrap_or(i64::MAX))
                 .unwrap_or_default();
-            let (payload_bytes, replacement_bytes) = image_data_url_estimate_adjustment(item);
-            if payload_bytes == 0 || replacement_bytes == 0 {
-                raw
-            } else {
-                // Replace raw base64 payload bytes with a per-image estimate.
-                // We intentionally preserve the data URL prefix and JSON
-                // wrapper bytes already included in `raw`.
-                raw.saturating_sub(payload_bytes)
-                    .saturating_add(replacement_bytes)
-            }
+            let (image_payload_bytes, image_replacement_bytes) =
+                image_data_url_estimate_adjustment(item);
+            let (encrypted_payload_bytes, encrypted_replacement_bytes) =
+                encrypted_function_output_estimate_adjustment(item);
+            // Replace raw base64 payload bytes with a per-image estimate.
+            // We intentionally preserve the data URL prefix and JSON
+            // wrapper bytes already included in `raw`.
+            let raw = raw
+                .saturating_sub(image_payload_bytes)
+                .saturating_add(image_replacement_bytes);
+            raw.saturating_sub(encrypted_payload_bytes)
+                .saturating_add(encrypted_replacement_bytes)
         }
     }
 }
@@ -678,6 +684,31 @@ fn image_data_url_estimate_adjustment(item: &ResponseItem) -> (i64, i64) {
     (payload_bytes, replacement_bytes)
 }
 
+fn encrypted_function_output_estimate_adjustment(item: &ResponseItem) -> (i64, i64) {
+    let ResponseItem::FunctionCallOutput { output, .. } = item else {
+        return (0, 0);
+    };
+    let FunctionCallOutputBody::ContentItems(items) = &output.body else {
+        return (0, 0);
+    };
+
+    items.iter().fold((0i64, 0i64), |acc, item| {
+        let FunctionCallOutputContentItem::EncryptedContent { encrypted_content } = item else {
+            return acc;
+        };
+        let payload_bytes = acc
+            .0
+            .saturating_add(i64::try_from(encrypted_content.len()).unwrap_or(i64::MAX));
+        let replacement_bytes = acc.1.saturating_add(
+            i64::try_from(estimate_encrypted_function_output_length(
+                encrypted_content.len(),
+            ))
+            .unwrap_or(i64::MAX),
+        );
+        (payload_bytes, replacement_bytes)
+    })
+}
+
 fn is_model_generated_item(item: &ResponseItem) -> bool {
     match item {
         ResponseItem::Message { role, .. } => role == "assistant",
diff --git a/codex-rs/core/src/context_manager/history_tests.rs b/codex-rs/core/src/context_manager/history_tests.rs
index 8ba5d56e32be..f63ae6ec1f14 100644
--- a/codex-rs/core/src/context_manager/history_tests.rs
+++ b/codex-rs/core/src/context_manager/history_tests.rs
@@ -1754,6 +1754,26 @@ fn non_base64_image_urls_are_unchanged() {
     );
 }
 
+#[test]
+fn encrypted_function_output_uses_plaintext_byte_estimate() {
+    let encrypted_content = "A".repeat(1_868);
+    let item = ResponseItem::FunctionCallOutput {
+        call_id: "call-encrypted".to_string(),
+        output: FunctionCallOutputPayload::from_content_items(vec![
+            FunctionCallOutputContentItem::EncryptedContent {
+                encrypted_content: encrypted_content.clone(),
+            },
+        ]),
+    };
+
+    let raw_len = serde_json::to_string(&item).unwrap().len() as i64;
+    let estimated = estimate_response_item_model_visible_bytes(&item);
+    let expected = raw_len - encrypted_content.len() as i64
+        + estimate_encrypted_function_output_length(encrypted_content.len()) as i64;
+
+    assert_eq!(estimated, expected);
+}
+
 #[test]
 fn data_url_without_base64_marker_is_unchanged() {
     let item = ResponseItem::Message {
diff --git a/codex-rs/protocol/src/models.rs b/codex-rs/protocol/src/models.rs
index d1d2abe75572..2927cb1cd135 100644
--- a/codex-rs/protocol/src/models.rs
+++ b/codex-rs/protocol/src/models.rs
@@ -1314,6 +1314,9 @@ pub enum FunctionCallOutputContentItem {
         #[ts(optional)]
         detail: Option<ImageDetail>,
     },
+    EncryptedContent {
+        encrypted_content: String,
+    },
 }
 
 /// Converts structured function-call output content into plain text for
@@ -1337,7 +1340,8 @@ pub fn function_call_output_content_items_to_text(
                 Some(text.as_str())
             }
             FunctionCallOutputContentItem::InputText { .. }
-            | FunctionCallOutputContentItem::InputImage { .. } => None,
+            | FunctionCallOutputContentItem::InputImage { .. }
+            | FunctionCallOutputContentItem::EncryptedContent { .. } => None,
         })
         .collect::<Vec<_>>();
 
@@ -2063,6 +2067,9 @@ mod tests {
                 image_url: "data:image/png;base64,AAA".to_string(),
                 detail: Some(DEFAULT_IMAGE_DETAIL),
             },
+            FunctionCallOutputContentItem::EncryptedContent {
+                encrypted_content: "enc_opaque".to_string(),
+            },
         ];
 
         let text = function_call_output_content_items_to_text(&content_items);
@@ -2270,6 +2277,35 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn serializes_encrypted_function_output_content_as_array() -> Result<()> {
+        let item = ResponseInputItem::FunctionCallOutput {
+            call_id: "call1".into(),
+            output: FunctionCallOutputPayload::from_content_items(vec![
+                FunctionCallOutputContentItem::EncryptedContent {
+                    encrypted_content: "enc_opaque".into(),
+                },
+            ]),
+        };
+
+        let json = serde_json::to_value(&item)?;
+        assert_eq!(
+            json,
+            serde_json::json!({
+                "type": "function_call_output",
+                "call_id": "call1",
+                "output": [
+                    {
+                        "type": "encrypted_content",
+                        "encrypted_content": "enc_opaque",
+                    }
+                ],
+            })
+        );
+
+        Ok(())
+    }
+
     #[test]
     fn preserves_existing_image_data_urls() -> Result<()> {
         let call_tool_result = CallToolResult {
@@ -2394,6 +2430,30 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn deserializes_encrypted_array_payload_into_items() -> Result<()> {
+        let json = r#"[
+            {"type": "encrypted_content", "encrypted_content": "enc_opaque"}
+        ]"#;
+
+        let payload: FunctionCallOutputPayload = serde_json::from_str(json)?;
+        let expected_items = vec![FunctionCallOutputContentItem::EncryptedContent {
+            encrypted_content: "enc_opaque".into(),
+        }];
+
+        assert_eq!(payload.success, None);
+        assert_eq!(
+            payload.body,
+            FunctionCallOutputBody::ContentItems(expected_items.clone())
+        );
+        assert_eq!(
+            serde_json::to_string(&payload)?,
+            serde_json::to_string(&expected_items)?
+        );
+
+        Ok(())
+    }
+
     #[test]
     fn deserializes_compaction_alias() -> Result<()> {
         let json = r#"{"type":"compaction_summary","encrypted_content":"abc"}"#;
diff --git a/codex-rs/tools/src/tool_output.rs b/codex-rs/tools/src/tool_output.rs
index 64a8164da36c..b61bb80de866 100644
--- a/codex-rs/tools/src/tool_output.rs
+++ b/codex-rs/tools/src/tool_output.rs
@@ -209,7 +209,8 @@ fn content_items_to_code_mode_result(items: &[FunctionCallOutputContentItem]) ->
                     Some(image_url.clone())
                 }
                 FunctionCallOutputContentItem::InputText { .. }
-                | FunctionCallOutputContentItem::InputImage { .. } => None,
+                | FunctionCallOutputContentItem::InputImage { .. }
+                | FunctionCallOutputContentItem::EncryptedContent { .. } => None,
             })
             .collect::<Vec<_>>()
             .join("\n"),
diff --git a/codex-rs/utils/output-truncation/src/lib.rs b/codex-rs/utils/output-truncation/src/lib.rs
index 24b1630da134..52cd741b7d09 100644
--- a/codex-rs/utils/output-truncation/src/lib.rs
+++ b/codex-rs/utils/output-truncation/src/lib.rs
@@ -34,7 +34,8 @@ pub fn formatted_truncate_text_content_items_with_policy(
         .iter()
         .filter_map(|item| match item {
             FunctionCallOutputContentItem::InputText { text } => Some(text.as_str()),
-            FunctionCallOutputContentItem::InputImage { .. } => None,
+            FunctionCallOutputContentItem::InputImage { .. }
+            | FunctionCallOutputContentItem::EncryptedContent { .. } => None,
         })
         .collect::<Vec<_>>();
 
@@ -64,6 +65,11 @@ pub fn formatted_truncate_text_content_items_with_policy(
                 detail: *detail,
             })
         }
+        FunctionCallOutputContentItem::EncryptedContent { encrypted_content } => {
+            Some(FunctionCallOutputContentItem::EncryptedContent {
+                encrypted_content: encrypted_content.clone(),
+            })
+        }
         FunctionCallOutputContentItem::InputText { .. } => None,
     }));
 
@@ -117,6 +123,11 @@ pub fn truncate_function_output_items_with_policy(
                     detail: *detail,
                 });
             }
+            FunctionCallOutputContentItem::EncryptedContent { encrypted_content } => {
+                out.push(FunctionCallOutputContentItem::EncryptedContent {
+                    encrypted_content: encrypted_content.clone(),
+                });
+            }
         }
     }
 
diff --git a/codex-rs/utils/output-truncation/src/truncate_tests.rs b/codex-rs/utils/output-truncation/src/truncate_tests.rs
index 74acb15ca3d2..baf26a058ece 100644
--- a/codex-rs/utils/output-truncation/src/truncate_tests.rs
+++ b/codex-rs/utils/output-truncation/src/truncate_tests.rs
@@ -251,6 +251,60 @@ fn formatted_truncate_text_content_items_with_policy_merges_text_and_appends_ima
     assert_eq!(original_token_count, Some(4));
 }
 
+#[test]
+fn formatted_truncate_text_content_items_with_policy_preserves_encrypted_content() {
+    let items = vec![
+        FunctionCallOutputContentItem::InputText {
+            text: "abcdefgh".to_string(),
+        },
+        FunctionCallOutputContentItem::EncryptedContent {
+            encrypted_content: "enc_opaque".to_string(),
+        },
+    ];
+
+    let (output, original_token_count) =
+        formatted_truncate_text_content_items_with_policy(&items, TruncationPolicy::Bytes(2));
+
+    assert_eq!(
+        output,
+        vec![
+            FunctionCallOutputContentItem::InputText {
+                text: "Total output lines: 1\n\na…6 chars truncated…h".to_string(),
+            },
+            FunctionCallOutputContentItem::EncryptedContent {
+                encrypted_content: "enc_opaque".to_string(),
+            },
+        ]
+    );
+    assert_eq!(original_token_count, Some(2));
+}
+
+#[test]
+fn truncate_function_output_items_with_policy_preserves_encrypted_content() {
+    let items = vec![
+        FunctionCallOutputContentItem::InputText {
+            text: "abcdefgh".to_string(),
+        },
+        FunctionCallOutputContentItem::EncryptedContent {
+            encrypted_content: "enc_opaque".to_string(),
+        },
+    ];
+
+    let output = truncate_function_output_items_with_policy(&items, TruncationPolicy::Bytes(2));
+
+    assert_eq!(
+        output,
+        vec![
+            FunctionCallOutputContentItem::InputText {
+                text: "a…6 chars truncated…h".to_string(),
+            },
+            FunctionCallOutputContentItem::EncryptedContent {
+                encrypted_content: "enc_opaque".to_string(),
+            },
+        ]
+    );
+}
+
 #[test]
 fn formatted_truncate_text_content_items_with_policy_merges_all_text_for_token_budget() {
     let items = vec![