feat: config aliases (#18140)

Rename `no_memories_if_mcp_or_web_search` →
`disable_on_external_context` with backward compatibility

While doing so, we add a key alias system on our layer merging system.
What we try to avoid is a case where a company managed config use an old
name while the user has a new name in it's local config (which would
make the deserialization fail)

codex-rs/core/config.schema.json

@@ -863,6 +863,10 @@
           "description": "Model used for memory consolidation.",
           "type": "string"
         },
+        "disable_on_external_context": {
+          "description": "When `true`, external context sources mark the thread `memory_mode` as `\"polluted\"`.",
+          "type": "boolean"
+        },
         "extract_model": {
           "description": "Model used for thread summarisation.",
           "type": "string"
@@ -900,10 +904,6 @@
           "format": "int64",
           "type": "integer"
         },
-        "no_memories_if_mcp_or_web_search": {
-          "description": "When `true`, web searches and MCP tool calls mark the thread `memory_mode` as `\"polluted\"`.",
-          "type": "boolean"
-        },
         "use_memories": {
           "description": "When `false`, skip injecting memory usage instructions into developer prompts.",
           "type": "boolean"

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

@@ -221,7 +221,7 @@ persistence = "none"
 
     let memories = r#"
 [memories]
-no_memories_if_mcp_or_web_search = true
+disable_on_external_context = true
 generate_memories = false
 use_memories = false
 max_raw_memories_for_consolidation = 512
@@ -236,7 +236,7 @@ consolidation_model = "gpt-5"
         toml::from_str::<ConfigToml>(memories).expect("TOML deserialization should succeed");
     assert_eq!(
         Some(MemoriesToml {
-            no_memories_if_mcp_or_web_search: Some(true),
+            disable_on_external_context: Some(true),
             generate_memories: Some(false),
             use_memories: Some(false),
             max_raw_memories_for_consolidation: Some(512),
@@ -260,7 +260,7 @@ consolidation_model = "gpt-5"
     assert_eq!(
         config.memories,
         MemoriesConfig {
-            no_memories_if_mcp_or_web_search: true,
+            disable_on_external_context: true,
             generate_memories: false,
             use_memories: false,
             max_raw_memories_for_consolidation: 512,
@@ -272,6 +272,18 @@ consolidation_model = "gpt-5"
             consolidation_model: Some("gpt-5".to_string()),
         }
     );
+
+    let legacy_memories_cfg =
+        toml::from_str::<ConfigToml>("[memories]\nno_memories_if_mcp_or_web_search = true\n")
+            .expect("legacy memories TOML should deserialize");
+    assert!(
+        MemoriesConfig::from(
+            legacy_memories_cfg
+                .memories
+                .expect("legacy memories config")
+        )
+        .disable_on_external_context
+    );
 }
 
 #[test]

codex-rs/core/src/mcp_tool_call.rs

@@ -541,11 +541,7 @@ async fn augment_mcp_tool_request_meta_with_sandbox_state(
 }
 
 async fn maybe_mark_thread_memory_mode_polluted(sess: &Session, turn_context: &TurnContext) {
-    if !turn_context
-        .config
-        .memories
-        .no_memories_if_mcp_or_web_search
-    {
+    if !turn_context.config.memories.disable_on_external_context {
         return;
     }
     state_db::mark_thread_memory_mode_polluted(

codex-rs/core/src/stream_events_utils.rs

@@ -154,10 +154,7 @@ pub(crate) async fn mark_thread_memory_mode_polluted_if_external_context(
     turn_context: &TurnContext,
     item: &ResponseItem,
 ) {
-    if !turn_context
-        .config
-        .memories
-        .no_memories_if_mcp_or_web_search
+    if !turn_context.config.memories.disable_on_external_context
         || !response_item_may_include_external_context(item)
     {
         return;

codex-rs/core/tests/suite/memories.rs

@@ -314,7 +314,7 @@ async fn web_search_pollution_moves_selected_thread_into_removed_phase2_inputs()
             .enable(Feature::MemoryTool)
             .expect("test config should allow feature update");
         config.memories.max_raw_memories_for_consolidation = 1;
-        config.memories.no_memories_if_mcp_or_web_search = true;
+        config.memories.disable_on_external_context = true;
     });
     let initial = initial_builder.build(&server).await?;
     mount_sse_once(
@@ -386,7 +386,7 @@ async fn web_search_pollution_moves_selected_thread_into_removed_phase2_inputs()
             .enable(Feature::MemoryTool)
             .expect("test config should allow feature update");
         config.memories.max_raw_memories_for_consolidation = 1;
-        config.memories.no_memories_if_mcp_or_web_search = true;
+        config.memories.disable_on_external_context = true;
     });
     let resumed = resumed_builder
         .resume(&server, home.clone(), rollout_path.clone())

codex-rs/core/tests/suite/sqlite_state.rs

@@ -297,7 +297,7 @@ async fn web_search_marks_thread_memory_mode_polluted_when_configured() -> Resul
             .features
             .enable(Feature::Sqlite)
             .expect("test config should allow feature update");
-        config.memories.no_memories_if_mcp_or_web_search = true;
+        config.memories.disable_on_external_context = true;
     });
     let test = builder.build(&server).await?;
     let db = test.codex.state_db().expect("state db enabled");
@@ -355,7 +355,7 @@ async fn mcp_call_marks_thread_memory_mode_polluted_when_configured() -> Result<
             .features
             .enable(Feature::Sqlite)
             .expect("test config should allow feature update");
-        config.memories.no_memories_if_mcp_or_web_search = true;
+        config.memories.disable_on_external_context = true;
 
         let mut servers = config.mcp_servers.get().clone();
         servers.insert(