diff --git a/codex-rs/core/src/tools/handlers/multi_agents/spawn.rs b/codex-rs/core/src/tools/handlers/multi_agents/spawn.rs
index 432b490a59..8fc7786e5f 100644
--- a/codex-rs/core/src/tools/handlers/multi_agents/spawn.rs
+++ b/codex-rs/core/src/tools/handlers/multi_agents/spawn.rs
@@ -1,4 +1,5 @@
 use super::*;
+use crate::agent::control::SpawnAgentForkMode;
 use crate::agent::control::SpawnAgentOptions;
 use crate::agent::control::render_input_preview;
 use crate::agent::role::DEFAULT_ROLE_NAME;
@@ -115,6 +116,7 @@ impl ToolHandler for Handler {
                     )?),
                     SpawnAgentOptions {
                         fork_parent_spawn_call_id: args.fork_context.then(|| call_id.clone()),
+                        fork_mode: args.fork_context.then_some(SpawnAgentForkMode::FullHistory),
                     },
                 )
                 .await;
diff --git a/codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs b/codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs
index 849bd606f8..3efeda3480 100644
--- a/codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs
+++ b/codex-rs/core/src/tools/handlers/multi_agents_v2/spawn.rs
@@ -1,4 +1,5 @@
 use super::*;
+use crate::agent::control::SpawnAgentForkMode;
 use crate::agent::control::SpawnAgentOptions;
 use crate::agent::control::render_input_preview;
 use crate::agent::next_thread_spawn_depth;
@@ -139,6 +140,7 @@ impl ToolHandler for Handler {
                     Some(spawn_source.clone()),
                     SpawnAgentOptions {
                         fork_parent_spawn_call_id: args.fork_context.then(|| call_id.clone()),
+                        fork_mode: args.fork_context.then_some(SpawnAgentForkMode::FullHistory),
                     },
                 )
                 .await;