[feat] persist dynamic tools in session rollout file (#10130)

Add dynamic tools to rollout file for persistence & read from rollout on
resume. Ran a real example and spotted the following in the rollout
file:
```
{"timestamp":"2026-01-29T01:27:57.468Z","type":"session_meta","payload":{"id":"019c075d-3f0b-77e3-894e-c1c159b04b1e","timestamp":"2026-01-29T01:27:57.451Z","...."dynamic_tools":[{"name":"demo_tool","description":"Demo dynamic tool","inputSchema":{"additionalProperties":false,"properties":{"city":{"type":"string"}},"required":["city"],"type":"object"}}],"git":{"commit_hash":"ebc573f15c01b8af158e060cfedd401f043e9dfa","branch":"dev/cc/dynamic-tools","repository_url":"https://github.com/openai/codex.git"}}}
```

codex-rs/app-server/tests/common/rollout.rs

@@ -81,6 +81,7 @@ pub fn create_fake_rollout_with_source(
         source,
         model_provider: model_provider.map(str::to_string),
         base_instructions: None,
+        dynamic_tools: None,
     };
     let payload = serde_json::to_value(SessionMetaLine {
         meta,
@@ -159,6 +160,7 @@ pub fn create_fake_rollout_with_text_elements(
         source: SessionSource::Cli,
         model_provider: model_provider.map(str::to_string),
         base_instructions: None,
+        dynamic_tools: None,
     };
     let payload = serde_json::to_value(SessionMetaLine {
         meta,

codex-rs/core/src/codex.rs

@@ -324,6 +324,12 @@ impl Codex {
             .clone()
             .or_else(|| conversation_history.get_base_instructions().map(|s| s.text))
             .unwrap_or_else(|| model_info.get_model_instructions(config.model_personality));
+        // Respect explicit thread-start tools; fall back to persisted tools when resuming a thread.
+        let dynamic_tools = if dynamic_tools.is_empty() {
+            conversation_history.get_dynamic_tools().unwrap_or_default()
+        } else {
+            dynamic_tools
+        };
 
         // TODO (aibrahim): Consolidate config.model and config.model_reasoning_effort into config.collaboration_mode
         // to avoid extracting these fields separately and constructing CollaborationMode here.
@@ -715,6 +721,7 @@ impl Session {
                         BaseInstructions {
                             text: session_configuration.base_instructions.clone(),
                         },
+                        session_configuration.dynamic_tools.clone(),
                     ),
                 )
             }

codex-rs/core/src/rollout/metadata.rs

@@ -303,6 +303,7 @@ mod tests {
             source: SessionSource::default(),
             model_provider: Some("openai".to_string()),
             base_instructions: None,
+            dynamic_tools: None,
         };
         let session_meta_line = SessionMetaLine {
             meta: session_meta,

codex-rs/core/src/rollout/recorder.rs

@@ -7,6 +7,7 @@ use std::path::Path;
 use std::path::PathBuf;
 
 use codex_protocol::ThreadId;
+use codex_protocol::dynamic_tools::DynamicToolSpec;
 use codex_protocol::models::BaseInstructions;
 use serde_json::Value;
 use time::OffsetDateTime;
@@ -68,6 +69,7 @@ pub enum RolloutRecorderParams {
         forked_from_id: Option<ThreadId>,
         source: SessionSource,
         base_instructions: BaseInstructions,
+        dynamic_tools: Vec<DynamicToolSpec>,
     },
     Resume {
         path: PathBuf,
@@ -91,12 +93,14 @@ impl RolloutRecorderParams {
         forked_from_id: Option<ThreadId>,
         source: SessionSource,
         base_instructions: BaseInstructions,
+        dynamic_tools: Vec<DynamicToolSpec>,
     ) -> Self {
         Self::Create {
             conversation_id,
             forked_from_id,
             source,
             base_instructions,
+            dynamic_tools,
         }
     }
 
@@ -259,6 +263,7 @@ impl RolloutRecorder {
                 forked_from_id,
                 source,
                 base_instructions,
+                dynamic_tools,
             } => {
                 let LogFileInfo {
                     file,
@@ -288,6 +293,11 @@ impl RolloutRecorder {
                         source,
                         model_provider: Some(config.model_provider_id.clone()),
                         base_instructions: Some(base_instructions),
+                        dynamic_tools: if dynamic_tools.is_empty() {
+                            None
+                        } else {
+                            Some(dynamic_tools)
+                        },
                     }),
                 )
             }

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

@@ -873,6 +873,7 @@ async fn test_updated_at_uses_file_mtime() -> Result<()> {
                 source: SessionSource::VSCode,
                 model_provider: Some("test-provider".into()),
                 base_instructions: None,
+                dynamic_tools: None,
             },
             git: None,
         }),

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

@@ -93,6 +93,7 @@ async fn backfill_scans_existing_rollouts() -> Result<()> {
                     source: SessionSource::default(),
                     model_provider: None,
                     base_instructions: None,
+                    dynamic_tools: None,
                 },
                 git: None,
             };

codex-rs/protocol/src/protocol.rs

@@ -20,6 +20,7 @@ use crate::config_types::WindowsSandboxLevel;
 use crate::custom_prompts::CustomPrompt;
 use crate::dynamic_tools::DynamicToolCallRequest;
 use crate::dynamic_tools::DynamicToolResponse;
+use crate::dynamic_tools::DynamicToolSpec;
 use crate::items::TurnItem;
 use crate::message_history::HistoryEntry;
 use crate::models::BaseInstructions;
@@ -1513,6 +1514,22 @@ impl InitialHistory {
             }),
         }
     }
+
+    pub fn get_dynamic_tools(&self) -> Option<Vec<DynamicToolSpec>> {
+        match self {
+            InitialHistory::New => None,
+            InitialHistory::Resumed(resumed) => {
+                resumed.history.iter().find_map(|item| match item {
+                    RolloutItem::SessionMeta(meta_line) => meta_line.meta.dynamic_tools.clone(),
+                    _ => None,
+                })
+            }
+            InitialHistory::Forked(items) => items.iter().find_map(|item| match item {
+                RolloutItem::SessionMeta(meta_line) => meta_line.meta.dynamic_tools.clone(),
+                _ => None,
+            }),
+        }
+    }
 }
 
 fn session_cwd_from_items(items: &[RolloutItem]) -> Option<PathBuf> {
@@ -1599,6 +1616,8 @@ pub struct SessionMeta {
     /// but may be missing for older sessions. If not present, fall back to rendering the base_instructions
     /// from ModelsManager.
     pub base_instructions: Option<BaseInstructions>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub dynamic_tools: Option<Vec<DynamicToolSpec>>,
 }
 
 impl Default for SessionMeta {
@@ -1613,6 +1632,7 @@ impl Default for SessionMeta {
             source: SessionSource::default(),
             model_provider: None,
             base_instructions: None,
+            dynamic_tools: None,
         }
     }
 }