Support initial Codex time context overrides

codex-rs/app-server-protocol/schema/json/ClientRequest.json

@@ -3763,6 +3763,13 @@
             "null"
           ]
         },
+        "currentDate": {
+          "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "cwd": {
           "type": [
             "string",
@@ -3816,6 +3823,13 @@
         },
         "threadId": {
           "type": "string"
+        },
+        "timezone": {
+          "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "required": [
@@ -3938,6 +3952,13 @@
             "null"
           ]
         },
+        "currentDate": {
+          "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "cwd": {
           "type": [
             "string",
@@ -4020,6 +4041,13 @@
             }
           ],
           "description": "Optional client-supplied analytics source classification for this thread."
+        },
+        "timezone": {
+          "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "type": "object"
@@ -4132,6 +4160,13 @@
           ],
           "description": "Override where approval requests are routed for review on this turn and subsequent turns."
         },
+        "currentDate": {
+          "description": "Override the current date shown in the model-visible environment context for this turn and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "cwd": {
           "description": "Override the working directory for this turn and subsequent turns.",
           "type": [
@@ -4208,6 +4243,13 @@
         },
         "threadId": {
           "type": "string"
+        },
+        "timezone": {
+          "description": "Override the timezone shown in the model-visible environment context for this turn and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "required": [

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -16815,6 +16815,13 @@
               "null"
             ]
           },
+          "currentDate": {
+            "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
           "cwd": {
             "type": [
               "string",
@@ -16868,6 +16875,13 @@
           },
           "threadId": {
             "type": "string"
+          },
+          "timezone": {
+            "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+            "type": [
+              "string",
+              "null"
+            ]
           }
         },
         "required": [
@@ -17097,6 +17111,13 @@
               "null"
             ]
           },
+          "currentDate": {
+            "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
           "cwd": {
             "type": [
               "string",
@@ -17179,6 +17200,13 @@
               }
             ],
             "description": "Optional client-supplied analytics source classification for this thread."
+          },
+          "timezone": {
+            "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+            "type": [
+              "string",
+              "null"
+            ]
           }
         },
         "title": "ThreadStartParams",
@@ -17846,6 +17874,13 @@
             ],
             "description": "Override where approval requests are routed for review on this turn and subsequent turns."
           },
+          "currentDate": {
+            "description": "Override the current date shown in the model-visible environment context for this turn and subsequent turns.",
+            "type": [
+              "string",
+              "null"
+            ]
+          },
           "cwd": {
             "description": "Override the working directory for this turn and subsequent turns.",
             "type": [
@@ -17922,6 +17957,13 @@
           },
           "threadId": {
             "type": "string"
+          },
+          "timezone": {
+            "description": "Override the timezone shown in the model-visible environment context for this turn and subsequent turns.",
+            "type": [
+              "string",
+              "null"
+            ]
           }
         },
         "required": [

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.v2.schemas.json

@@ -14639,6 +14639,13 @@
             "null"
           ]
         },
+        "currentDate": {
+          "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "cwd": {
           "type": [
             "string",
@@ -14692,6 +14699,13 @@
         },
         "threadId": {
           "type": "string"
+        },
+        "timezone": {
+          "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "required": [
@@ -14921,6 +14935,13 @@
             "null"
           ]
         },
+        "currentDate": {
+          "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "cwd": {
           "type": [
             "string",
@@ -15003,6 +15024,13 @@
             }
           ],
           "description": "Optional client-supplied analytics source classification for this thread."
+        },
+        "timezone": {
+          "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "title": "ThreadStartParams",
@@ -15670,6 +15698,13 @@
           ],
           "description": "Override where approval requests are routed for review on this turn and subsequent turns."
         },
+        "currentDate": {
+          "description": "Override the current date shown in the model-visible environment context for this turn and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
         "cwd": {
           "description": "Override the working directory for this turn and subsequent turns.",
           "type": [
@@ -15746,6 +15781,13 @@
         },
         "threadId": {
           "type": "string"
+        },
+        "timezone": {
+          "description": "Override the timezone shown in the model-visible environment context for this turn and subsequent turns.",
+          "type": [
+            "string",
+            "null"
+          ]
         }
       },
       "required": [

codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json

@@ -1048,6 +1048,13 @@
         "null"
       ]
     },
+    "currentDate": {
+      "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
     "cwd": {
       "type": [
         "string",
@@ -1101,6 +1108,13 @@
     },
     "threadId": {
       "type": "string"
+    },
+    "timezone": {
+      "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+      "type": [
+        "string",
+        "null"
+      ]
     }
   },
   "required": [

codex-rs/app-server-protocol/schema/json/v2/ThreadStartParams.json

@@ -231,6 +231,13 @@
         "null"
       ]
     },
+    "currentDate": {
+      "description": "Override the current date shown in the model-visible environment context for this thread and subsequent turns.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
     "cwd": {
       "type": [
         "string",
@@ -313,6 +320,13 @@
         }
       ],
       "description": "Optional client-supplied analytics source classification for this thread."
+    },
+    "timezone": {
+      "description": "Override the timezone shown in the model-visible environment context for this thread and subsequent turns.",
+      "type": [
+        "string",
+        "null"
+      ]
     }
   },
   "title": "ThreadStartParams",

codex-rs/app-server-protocol/schema/json/v2/TurnStartParams.json

@@ -522,6 +522,13 @@
       ],
       "description": "Override where approval requests are routed for review on this turn and subsequent turns."
     },
+    "currentDate": {
+      "description": "Override the current date shown in the model-visible environment context for this turn and subsequent turns.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
     "cwd": {
       "description": "Override the working directory for this turn and subsequent turns.",
       "type": [
@@ -598,6 +605,13 @@
     },
     "threadId": {
       "type": "string"
+    },
+    "timezone": {
+      "description": "Override the timezone shown in the model-visible environment context for this turn and subsequent turns.",
+      "type": [
+        "string",
+        "null"
+      ]
     }
   },
   "required": [

codex-rs/app-server-protocol/schema/typescript/v2/ThreadResumeParams.ts

@@ -25,4 +25,12 @@ model?: string | null, modelProvider?: string | null, serviceTier?: string | nul
  * Override where approval requests are routed for review on this thread
  * and subsequent turns.
  */
-approvalsReviewer?: ApprovalsReviewer | null, sandbox?: SandboxMode | null, config?: { [key in string]?: JsonValue } | null, baseInstructions?: string | null, developerInstructions?: string | null, personality?: Personality | null};
+approvalsReviewer?: ApprovalsReviewer | null, sandbox?: SandboxMode | null, config?: { [key in string]?: JsonValue } | null, baseInstructions?: string | null, developerInstructions?: string | null, /**
+ * Override the current date shown in the model-visible environment
+ * context for this thread and subsequent turns.
+ */
+currentDate?: string | null, /**
+ * Override the timezone shown in the model-visible environment context
+ * for this thread and subsequent turns.
+ */
+timezone?: string | null, personality?: Personality | null};

codex-rs/app-server-protocol/schema/typescript/v2/ThreadStartParams.ts

@@ -13,7 +13,15 @@ export type ThreadStartParams = {model?: string | null, modelProvider?: string |
  * Override where approval requests are routed for review on this thread
  * and subsequent turns.
  */
-approvalsReviewer?: ApprovalsReviewer | null, sandbox?: SandboxMode | null, config?: { [key in string]?: JsonValue } | null, serviceName?: string | null, baseInstructions?: string | null, developerInstructions?: string | null, personality?: Personality | null, ephemeral?: boolean | null, sessionStartSource?: ThreadStartSource | null, /**
+approvalsReviewer?: ApprovalsReviewer | null, sandbox?: SandboxMode | null, config?: { [key in string]?: JsonValue } | null, serviceName?: string | null, baseInstructions?: string | null, developerInstructions?: string | null, /**
+ * Override the current date shown in the model-visible environment
+ * context for this thread and subsequent turns.
+ */
+currentDate?: string | null, /**
+ * Override the timezone shown in the model-visible environment context
+ * for this thread and subsequent turns.
+ */
+timezone?: string | null, personality?: Personality | null, ephemeral?: boolean | null, sessionStartSource?: ThreadStartSource | null, /**
  * Optional client-supplied analytics source classification for this thread.
  */
 threadSource?: ThreadSource | null};

codex-rs/app-server-protocol/schema/typescript/v2/TurnStartParams.ts

@@ -14,6 +14,14 @@ export type TurnStartParams = {threadId: string, input: Array<UserInput>, /**
  * Override the working directory for this turn and subsequent turns.
  */
 cwd?: string | null, /**
+ * Override the current date shown in the model-visible environment context
+ * for this turn and subsequent turns.
+ */
+currentDate?: string | null, /**
+ * Override the timezone shown in the model-visible environment context for
+ * this turn and subsequent turns.
+ */
+timezone?: string | null, /**
  * Override the approval policy for this turn and subsequent turns.
  */
 approvalPolicy?: AskForApproval | null, /**

codex-rs/app-server-protocol/src/protocol/v2/tests.rs

@@ -3409,6 +3409,8 @@ fn turn_start_params_preserve_explicit_null_service_tier() {
         responsesapi_client_metadata: None,
         environments: None,
         cwd: None,
+        current_date: None,
+        timezone: None,
         approval_policy: None,
         approvals_reviewer: None,
         sandbox_policy: None,

codex-rs/app-server-protocol/src/protocol/v2/thread.rs

@@ -130,6 +130,14 @@ pub struct ThreadStartParams {
     pub base_instructions: Option<String>,
     #[ts(optional = nullable)]
     pub developer_instructions: Option<String>,
+    /// Override the current date shown in the model-visible environment
+    /// context for this thread and subsequent turns.
+    #[ts(optional = nullable)]
+    pub current_date: Option<String>,
+    /// Override the timezone shown in the model-visible environment context
+    /// for this thread and subsequent turns.
+    #[ts(optional = nullable)]
+    pub timezone: Option<String>,
     #[ts(optional = nullable)]
     pub personality: Option<Personality>,
     #[ts(optional = nullable)]
@@ -285,6 +293,14 @@ pub struct ThreadResumeParams {
     pub base_instructions: Option<String>,
     #[ts(optional = nullable)]
     pub developer_instructions: Option<String>,
+    /// Override the current date shown in the model-visible environment
+    /// context for this thread and subsequent turns.
+    #[ts(optional = nullable)]
+    pub current_date: Option<String>,
+    /// Override the timezone shown in the model-visible environment context
+    /// for this thread and subsequent turns.
+    #[ts(optional = nullable)]
+    pub timezone: Option<String>,
     #[ts(optional = nullable)]
     pub personality: Option<Personality>,
     /// When true, return only thread metadata and live-resume state without

codex-rs/app-server-protocol/src/protocol/v2/turn.rs

@@ -64,6 +64,14 @@ pub struct TurnStartParams {
     /// Override the working directory for this turn and subsequent turns.
     #[ts(optional = nullable)]
     pub cwd: Option<PathBuf>,
+    /// Override the current date shown in the model-visible environment context
+    /// for this turn and subsequent turns.
+    #[ts(optional = nullable)]
+    pub current_date: Option<String>,
+    /// Override the timezone shown in the model-visible environment context for
+    /// this turn and subsequent turns.
+    #[ts(optional = nullable)]
+    pub timezone: Option<String>,
     /// Override the approval policy for this turn and subsequent turns.
     #[experimental(nested)]
     #[ts(optional = nullable)]

codex-rs/app-server/src/message_processor_tracing_tests.rs

@@ -658,6 +658,8 @@ async fn turn_start_jsonrpc_span_parents_core_turn_spans() -> Result<()> {
                     }],
                     responsesapi_client_metadata: None,
                     cwd: None,
+                    current_date: None,
+                    timezone: None,
                     approval_policy: None,
                     sandbox_policy: None,
                     permissions: None,

codex-rs/app-server/src/request_processors/thread_processor.rs

@@ -806,6 +806,8 @@ impl ThreadRequestProcessor {
             service_name,
             base_instructions,
             developer_instructions,
+            current_date,
+            timezone,
             dynamic_tools,
             mock_experimental_field: _mock_experimental_field,
             experimental_raw_events,
@@ -837,6 +839,8 @@ impl ThreadRequestProcessor {
             permissions,
             base_instructions,
             developer_instructions,
+            current_date,
+            timezone,
             personality,
         );
         typesafe_overrides.ephemeral = ephemeral;
@@ -1201,6 +1205,8 @@ impl ThreadRequestProcessor {
         permissions: Option<PermissionProfileSelectionParams>,
         base_instructions: Option<String>,
         developer_instructions: Option<String>,
+        current_date: Option<String>,
+        timezone: Option<String>,
         personality: Option<Personality>,
     ) -> ConfigOverrides {
         let mut overrides = ConfigOverrides {
@@ -1217,6 +1223,8 @@ impl ThreadRequestProcessor {
             main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
             base_instructions,
             developer_instructions,
+            current_date,
+            timezone,
             personality,
             ..Default::default()
         };
@@ -2369,6 +2377,8 @@ impl ThreadRequestProcessor {
             config: mut request_overrides,
             base_instructions,
             developer_instructions,
+            current_date,
+            timezone,
             personality,
             exclude_turns,
             persist_extended_history: _persist_extended_history,
@@ -2403,6 +2413,8 @@ impl ThreadRequestProcessor {
             permissions,
             base_instructions,
             developer_instructions,
+            current_date,
+            timezone,
             personality,
         );
         self.load_and_apply_persisted_resume_metadata(
@@ -3063,6 +3075,8 @@ impl ThreadRequestProcessor {
             permissions,
             base_instructions,
             developer_instructions,
+            /*current_date*/ None,
+            /*timezone*/ None,
             /*personality*/ None,
         );
         typesafe_overrides.ephemeral = ephemeral.then_some(true);

codex-rs/app-server/src/request_processors/thread_processor_tests.rs

@@ -637,6 +637,8 @@ mod thread_processor_behavior_tests {
             config: None,
             base_instructions: None,
             developer_instructions: None,
+            current_date: None,
+            timezone: None,
             personality: None,
             exclude_turns: false,
             persist_extended_history: false,

codex-rs/app-server/src/request_processors/turn_processor.rs

@@ -354,6 +354,8 @@ impl TurnRequestProcessor {
         let turn_has_input = !mapped_items.is_empty();
 
         let has_any_overrides = params.cwd.is_some()
+            || params.current_date.is_some()
+            || params.timezone.is_some()
             || params.approval_policy.is_some()
             || params.approvals_reviewer.is_some()
             || params.sandbox_policy.is_some()
@@ -372,6 +374,8 @@ impl TurnRequestProcessor {
         }
 
         let cwd = params.cwd;
+        let current_date = params.current_date;
+        let timezone = params.timezone;
         let approval_policy = params.approval_policy.map(AskForApproval::to_core);
         let approvals_reviewer = params
             .approvals_reviewer
@@ -429,6 +433,8 @@ impl TurnRequestProcessor {
             thread
                 .validate_turn_context_overrides(CodexThreadTurnContextOverrides {
                     cwd: cwd.clone(),
+                    current_date: current_date.clone(),
+                    timezone: timezone.clone(),
                     approval_policy,
                     approvals_reviewer,
                     sandbox_policy: sandbox_policy.clone(),
@@ -454,6 +460,8 @@ impl TurnRequestProcessor {
                 final_output_json_schema: params.output_schema,
                 responsesapi_client_metadata: params.responsesapi_client_metadata,
                 cwd,
+                current_date,
+                timezone,
                 approval_policy,
                 approvals_reviewer,
                 sandbox_policy,

codex-rs/app-server/tests/suite/v2/skills_list.rs

@@ -592,6 +592,8 @@ async fn skills_changed_notification_is_emitted_after_skill_change() -> Result<(
             service_name: None,
             base_instructions: None,
             developer_instructions: None,
+            current_date: None,
+            timezone: None,
             personality: None,
             ephemeral: None,
             session_start_source: None,

codex-rs/app-server/tests/suite/v2/turn_start.rs

@@ -1890,6 +1890,8 @@ async fn turn_start_updates_sandbox_and_cwd_between_turns_v2() -> Result<()> {
             }],
             responsesapi_client_metadata: None,
             cwd: Some(first_cwd.clone()),
+            current_date: None,
+            timezone: None,
             approval_policy: Some(codex_app_server_protocol::AskForApproval::Never),
             approvals_reviewer: None,
             sandbox_policy: Some(codex_app_server_protocol::SandboxPolicy::WorkspaceWrite {
@@ -1931,6 +1933,8 @@ async fn turn_start_updates_sandbox_and_cwd_between_turns_v2() -> Result<()> {
             }],
             responsesapi_client_metadata: None,
             cwd: Some(second_cwd.clone()),
+            current_date: None,
+            timezone: None,
             approval_policy: Some(codex_app_server_protocol::AskForApproval::Never),
             approvals_reviewer: None,
             sandbox_policy: Some(codex_app_server_protocol::SandboxPolicy::DangerFullAccess),

codex-rs/core/src/codex_thread.rs

@@ -81,6 +81,8 @@ impl ThreadConfigSnapshot {
 #[derive(Clone, Default)]
 pub struct CodexThreadTurnContextOverrides {
     pub cwd: Option<PathBuf>,
+    pub current_date: Option<String>,
+    pub timezone: Option<String>,
     pub approval_policy: Option<AskForApproval>,
     pub approvals_reviewer: Option<ApprovalsReviewer>,
     pub sandbox_policy: Option<SandboxPolicy>,
@@ -240,6 +242,8 @@ impl CodexThread {
     ) -> ConstraintResult<()> {
         let CodexThreadTurnContextOverrides {
             cwd,
+            current_date,
+            timezone,
             approval_policy,
             approvals_reviewer,
             sandbox_policy,
@@ -265,6 +269,8 @@ impl CodexThread {
 
         let updates = SessionSettingsUpdate {
             cwd,
+            current_date,
+            timezone,
             approval_policy,
             approvals_reviewer,
             sandbox_policy,

codex-rs/core/src/config/config_tests.rs

@@ -7043,6 +7043,8 @@ async fn test_precedence_fixture_with_o3_profile() -> std::io::Result<()> {
             experimental_thread_store: ThreadStoreConfig::Local,
             base_instructions: None,
             developer_instructions: None,
+            current_date: None,
+            timezone: None,
             guardian_policy_config: None,
             include_permissions_instructions: true,
             include_apps_instructions: true,
@@ -7463,6 +7465,8 @@ async fn test_precedence_fixture_with_gpt3_profile() -> std::io::Result<()> {
         experimental_thread_store: ThreadStoreConfig::Local,
         base_instructions: None,
         developer_instructions: None,
+        current_date: None,
+        timezone: None,
         guardian_policy_config: None,
         include_permissions_instructions: true,
         include_apps_instructions: true,
@@ -7621,6 +7625,8 @@ async fn test_precedence_fixture_with_zdr_profile() -> std::io::Result<()> {
         experimental_thread_store: ThreadStoreConfig::Local,
         base_instructions: None,
         developer_instructions: None,
+        current_date: None,
+        timezone: None,
         guardian_policy_config: None,
         include_permissions_instructions: true,
         include_apps_instructions: true,
@@ -7764,6 +7770,8 @@ async fn test_precedence_fixture_with_gpt5_profile() -> std::io::Result<()> {
         experimental_thread_store: ThreadStoreConfig::Local,
         base_instructions: None,
         developer_instructions: None,
+        current_date: None,
+        timezone: None,
         guardian_policy_config: None,
         include_permissions_instructions: true,
         include_apps_instructions: true,

codex-rs/core/src/config/mod.rs

@@ -449,6 +449,14 @@ pub struct Config {
     /// Developer instructions override injected as a separate message.
     pub developer_instructions: Option<String>,
 
+    /// Optional current date override shown in the model-visible environment
+    /// context for this session.
+    pub current_date: Option<String>,
+
+    /// Optional timezone override shown in the model-visible environment
+    /// context for this session.
+    pub timezone: Option<String>,
+
     /// Guardian-specific policy config override from requirements.toml or config.toml.
     /// This is inserted into the fixed guardian prompt template under the
     /// `# Policy Configuration` section rather than replacing the whole
@@ -1867,6 +1875,8 @@ pub struct ConfigOverrides {
     pub zsh_path: Option<PathBuf>,
     pub base_instructions: Option<String>,
     pub developer_instructions: Option<String>,
+    pub current_date: Option<String>,
+    pub timezone: Option<String>,
     pub personality: Option<Personality>,
     pub compact_prompt: Option<String>,
     pub include_apply_patch_tool: Option<bool>,
@@ -2142,6 +2152,8 @@ impl Config {
             zsh_path: zsh_path_override,
             base_instructions,
             developer_instructions,
+            current_date,
+            timezone,
             personality,
             compact_prompt,
             include_apply_patch_tool: include_apply_patch_tool_override,
@@ -2999,6 +3011,8 @@ impl Config {
             base_instructions,
             personality,
             developer_instructions,
+            current_date,
+            timezone,
             compact_prompt,
             commit_attribution,
             include_permissions_instructions,

codex-rs/core/src/context_manager/updates.rs

@@ -69,6 +69,21 @@ fn build_permissions_update_item(
     )
 }
 
+fn build_developer_instructions_update_item(
+    previous: Option<&TurnContextItem>,
+    next: &TurnContext,
+) -> Option<String> {
+    let prev = previous?;
+    if prev.developer_instructions == next.developer_instructions {
+        return None;
+    }
+
+    next.developer_instructions
+        .as_deref()
+        .filter(|instructions| !instructions.trim().is_empty())
+        .map(str::to_string)
+}
+
 fn build_collaboration_mode_update_item(
     previous: Option<&TurnContextItem>,
     next: &TurnContext,
@@ -218,6 +233,7 @@ pub(crate) fn build_settings_update_items(
         // Keep model-switch instructions first so model-specific guidance is read before
         // any other context diffs on this turn.
         build_model_instructions_update_item(previous_turn_settings, next),
+        build_developer_instructions_update_item(previous, next),
         build_permissions_update_item(previous, next, exec_policy),
         build_collaboration_mode_update_item(previous, next),
         build_realtime_update_item(previous, previous_turn_settings, next),

codex-rs/core/src/session/handlers.rs

@@ -143,6 +143,8 @@ pub(super) async fn user_input_or_turn_inner(
                 items,
                 SessionSettingsUpdate {
                     cwd: Some(cwd),
+                    current_date: None,
+                    timezone: None,
                     approval_policy: Some(approval_policy),
                     approvals_reviewer,
                     sandbox_policy: Some(sandbox_policy),
@@ -163,6 +165,8 @@ pub(super) async fn user_input_or_turn_inner(
         }
         Op::UserInputWithTurnContext {
             cwd,
+            current_date,
+            timezone,
             approval_policy,
             approvals_reviewer,
             sandbox_policy,
@@ -195,6 +199,8 @@ pub(super) async fn user_input_or_turn_inner(
                 items,
                 SessionSettingsUpdate {
                     cwd,
+                    current_date,
+                    timezone,
                     approval_policy,
                     approvals_reviewer,
                     sandbox_policy,

codex-rs/core/src/session/mod.rs

@@ -620,6 +620,8 @@ impl Codex {
             active_permission_profile: config.permissions.active_permission_profile(),
             windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
             cwd: config.cwd.clone(),
+            current_date: config.current_date.clone(),
+            timezone: config.timezone.clone(),
             codex_home: config.codex_home.clone(),
             thread_name: None,
             environments: environment_selections.to_selections(),

codex-rs/core/src/session/session.rs

@@ -75,6 +75,10 @@ pub(crate) struct SessionConfiguration {
     /// execution sandbox are resolved against this directory **instead** of
     /// the process-wide current working directory.
     pub(super) cwd: AbsolutePathBuf,
+    /// Optional current date override for the model-visible environment context.
+    pub(super) current_date: Option<String>,
+    /// Optional timezone override for the model-visible environment context.
+    pub(super) timezone: Option<String>,
     /// Directory containing all Codex state for this session.
     pub(super) codex_home: AbsolutePathBuf,
     /// Optional user-facing name for the thread, updated during the session.
@@ -199,6 +203,12 @@ impl SessionConfiguration {
         if let Some(approval_policy) = updates.approval_policy {
             next_configuration.approval_policy.set(approval_policy)?;
         }
+        if let Some(current_date) = updates.current_date.clone() {
+            next_configuration.current_date = Some(current_date);
+        }
+        if let Some(timezone) = updates.timezone.clone() {
+            next_configuration.timezone = Some(timezone);
+        }
         if let Some(approvals_reviewer) = updates.approvals_reviewer {
             next_configuration.approvals_reviewer = approvals_reviewer;
         }
@@ -309,6 +319,8 @@ impl SessionConfiguration {
 #[derive(Default, Clone)]
 pub(crate) struct SessionSettingsUpdate {
     pub(crate) cwd: Option<PathBuf>,
+    pub(crate) current_date: Option<String>,
+    pub(crate) timezone: Option<String>,
     pub(crate) approval_policy: Option<AskForApproval>,
     pub(crate) approvals_reviewer: Option<ApprovalsReviewer>,
     pub(crate) sandbox_policy: Option<SandboxPolicy>,

codex-rs/core/src/session/tests.rs

@@ -2581,6 +2581,8 @@ async fn set_rate_limits_retains_previous_credits() {
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: Vec::new(),
@@ -2685,6 +2687,8 @@ async fn set_rate_limits_updates_plan_type_when_present() {
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: Vec::new(),
@@ -3126,6 +3130,41 @@ async fn session_settings_legacy_fast_service_tier_update_uses_priority_request_
     );
 }
 
+#[tokio::test]
+async fn session_configuration_apply_updates_environment_context_overrides() {
+    let session_configuration = make_session_configuration_for_tests().await;
+
+    let updated = session_configuration
+        .apply(&SessionSettingsUpdate {
+            current_date: Some("2026-05-13".to_string()),
+            timezone: Some("America/Los_Angeles".to_string()),
+            ..Default::default()
+        })
+        .expect("time context update should succeed");
+
+    assert_eq!(updated.current_date.as_deref(), Some("2026-05-13"));
+    assert_eq!(updated.timezone.as_deref(), Some("America/Los_Angeles"));
+}
+
+#[tokio::test]
+async fn turn_context_uses_initial_environment_context_overrides() {
+    let (_session, turn_context, _rx) = make_session_and_context_with_auth_and_config_and_rx(
+        CodexAuth::from_api_key("Test API Key"),
+        Vec::new(),
+        |config| {
+            config.current_date = Some("2026-05-13".to_string());
+            config.timezone = Some("America/Los_Angeles".to_string());
+        },
+    )
+    .await;
+
+    assert_eq!(turn_context.current_date.as_deref(), Some("2026-05-13"));
+    assert_eq!(
+        turn_context.timezone.as_deref(),
+        Some("America/Los_Angeles")
+    );
+}
+
 pub(crate) async fn make_session_configuration_for_tests() -> SessionConfiguration {
     let codex_home = tempfile::tempdir().expect("create temp dir");
     let config = build_test_config(codex_home.path()).await;
@@ -3162,6 +3201,8 @@ pub(crate) async fn make_session_configuration_for_tests() -> SessionConfigurati
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: Vec::new(),
@@ -3688,6 +3729,8 @@ async fn session_new_fails_when_zsh_fork_enabled_without_zsh_path() {
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: Vec::new(),
@@ -3797,6 +3840,8 @@ pub(crate) async fn make_session_and_context() -> (Session, TurnContext) {
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: default_environments,
@@ -4026,6 +4071,8 @@ async fn make_session_with_config_and_rx(
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: None,
+        timezone: None,
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: default_environments,
@@ -4129,6 +4176,8 @@ async fn make_session_with_history_source_and_agent_control_and_rx(
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: None,
+        timezone: None,
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: default_environments,
@@ -4776,6 +4825,8 @@ fn op_kind_distinguishes_turn_ops() {
             final_output_json_schema: None,
             responsesapi_client_metadata: None,
             cwd: None,
+            current_date: None,
+            timezone: None,
             approval_policy: None,
             approvals_reviewer: None,
             sandbox_policy: None,
@@ -5516,6 +5567,8 @@ where
         active_permission_profile: config.permissions.active_permission_profile(),
         windows_sandbox_level: WindowsSandboxLevel::from_config(&config),
         cwd: config.cwd.clone(),
+        current_date: None,
+        timezone: None,
         codex_home: config.codex_home.clone(),
         thread_name: None,
         environments: default_environments,
@@ -6004,6 +6057,63 @@ async fn build_settings_update_items_omits_environment_item_when_disabled() {
     );
 }
 
+#[tokio::test]
+async fn build_settings_update_items_emits_developer_item_for_developer_instruction_changes() {
+    let (session, mut previous_context) = make_session_and_context().await;
+    previous_context.developer_instructions = Some("old developer guidance".to_string());
+    let previous_context = Arc::new(previous_context);
+    let mut current_context = previous_context
+        .with_model(
+            previous_context.model_info.slug.clone(),
+            &session.services.models_manager,
+        )
+        .await;
+    current_context.developer_instructions = Some("new developer guidance".to_string());
+
+    let update_items = session
+        .build_settings_update_items(
+            Some(&previous_context.to_turn_context_item()),
+            &current_context,
+        )
+        .await;
+
+    let developer_texts = developer_input_texts(&update_items);
+    assert!(
+        developer_texts
+            .iter()
+            .any(|text| text.contains("new developer guidance")),
+        "expected changed developer instructions to be appended, got {developer_texts:?}"
+    );
+    assert!(
+        !developer_texts
+            .iter()
+            .any(|text| text.contains("old developer guidance")),
+        "did not expect previous developer instructions to be re-appended, got {developer_texts:?}"
+    );
+}
+
+#[tokio::test]
+async fn build_settings_update_items_omits_unchanged_developer_instruction_item() {
+    let (session, mut previous_context) = make_session_and_context().await;
+    previous_context.developer_instructions = Some("stable developer guidance".to_string());
+    let previous_context = Arc::new(previous_context);
+    let current_context = previous_context
+        .with_model(
+            previous_context.model_info.slug.clone(),
+            &session.services.models_manager,
+        )
+        .await;
+
+    let update_items = session
+        .build_settings_update_items(
+            Some(&previous_context.to_turn_context_item()),
+            &current_context,
+        )
+        .await;
+
+    assert!(developer_input_texts(&update_items).is_empty());
+}
+
 #[tokio::test]
 async fn build_settings_update_items_emits_realtime_start_when_session_becomes_live() {
     let (session, previous_context) = make_session_and_context().await;

codex-rs/core/src/session/turn_context.rs

@@ -536,7 +536,15 @@ impl Session {
             session_configuration.windows_sandbox_level,
             network.is_some(),
         ));
-        let (current_date, timezone) = local_time_context();
+        let (local_current_date, local_timezone) = local_time_context();
+        let current_date = session_configuration
+            .current_date
+            .clone()
+            .unwrap_or(local_current_date);
+        let timezone = session_configuration
+            .timezone
+            .clone()
+            .unwrap_or(local_timezone);
         TurnContext {
             sub_id,
             trace_id: current_span_trace_id(),

codex-rs/exec/src/lib.rs

@@ -951,6 +951,8 @@ fn thread_start_params_from_config(config: &Config) -> ThreadStartParams {
         sandbox: sandbox.flatten(),
         permissions,
         config: config_request_overrides_from_config(config),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         ephemeral: Some(config.ephemeral),
         ..ThreadStartParams::default()
     }
@@ -973,6 +975,8 @@ fn thread_resume_params_from_config(config: &Config, thread_id: String) -> Threa
         approvals_reviewer: approvals_reviewer_override_from_config(config),
         sandbox: sandbox.flatten(),
         permissions,
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         config: config_request_overrides_from_config(config),
         ..ThreadResumeParams::default()
     }

codex-rs/protocol/src/protocol.rs

@@ -462,6 +462,14 @@ pub enum Op {
         #[serde(skip_serializing_if = "Option::is_none")]
         cwd: Option<PathBuf>,
 
+        /// Updated current date shown in the model-visible environment context.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        current_date: Option<String>,
+
+        /// Updated timezone shown in the model-visible environment context.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        timezone: Option<String>,
+
         /// Updated command approval policy.
         #[serde(skip_serializing_if = "Option::is_none")]
         approval_policy: Option<AskForApproval>,

codex-rs/tui/src/app_server_session.rs

@@ -1194,6 +1194,8 @@ fn thread_start_params_from_config(
         sandbox,
         permissions,
         config: config_request_overrides_from_config(config),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         ephemeral: Some(config.ephemeral),
         session_start_source,
         thread_source: Some(ThreadSource::User),
@@ -1228,6 +1230,8 @@ fn thread_resume_params_from_config(
         sandbox,
         permissions,
         config: config_request_overrides_from_config(&config),
+        current_date: config.current_date.clone(),
+        timezone: config.timezone.clone(),
         persist_extended_history: false,
         ..ThreadResumeParams::default()
     }