diff --git a/codex-rs/core/src/tools/router.rs b/codex-rs/core/src/tools/router.rs
index baf39f082af7..c21f732774c8 100644
--- a/codex-rs/core/src/tools/router.rs
+++ b/codex-rs/core/src/tools/router.rs
@@ -344,6 +344,21 @@ impl ToolRouter {
         .await
     }
 
+    /// codex-local H8: some backends (Ollama) flatten `namespace` into the name
+    /// as `ns.tool`. Split only when the literal name misses but the split hits.
+    pub(crate) fn unflatten_tool_name(&self, name: ToolName) -> ToolName {
+        match name.name.split_once('.') {
+            Some((ns, n))
+                if name.is_default_namespace()
+                    && self.registry.tool(&name).is_none()
+                    && self.registry.tool(&ToolName::namespaced(ns, n)).is_some() =>
+            {
+                ToolName::namespaced(ns, n)
+            }
+            _ => name,
+        }
+    }
+
     #[allow(clippy::too_many_arguments)]
     async fn dispatch_tool_call_with_code_mode_result_inner(
         &self,
@@ -361,6 +376,7 @@ impl ToolRouter {
             payload,
             ..
         } = call;
+        let tool_name = self.unflatten_tool_name(tool_name);
 
         // Keep the legacy ToolInvocation.turn field tied to the same request state until handlers migrate.
         let turn = Arc::clone(&step_context.turn);
diff --git a/codex-rs/core/src/tools/router_tests.rs b/codex-rs/core/src/tools/router_tests.rs
index 05a1e2e65a3b..d0b691af800e 100644
--- a/codex-rs/core/src/tools/router_tests.rs
+++ b/codex-rs/core/src/tools/router_tests.rs
@@ -649,3 +649,21 @@ fn namespace_function_names(specs: &[ToolSpec], namespace_name: &str) -> Vec<Str
         })
         .unwrap_or_default()
 }
+
+#[tokio::test]
+async fn unflatten_tool_name_splits_only_registered_dotted_names() {
+    let (_, turn) = make_session_and_context().await;
+    let turn = Arc::new(turn);
+    let step_context = StepContext::for_test(Arc::clone(&turn));
+    let router = test_tool_router(
+        step_context.as_ref(),
+        Vec::new(),
+        Vec::new(),
+        &turn.dynamic_tools,
+    );
+
+    let split = router.unflatten_tool_name(ToolName::plain("functions.exec_command"));
+    assert_eq!(split, ToolName::namespaced("functions", "exec_command"));
+    let unknown = ToolName::plain("nope.exec_command");
+    assert_eq!(router.unflatten_tool_name(unknown.clone()), unknown);
+}
diff --git a/local/FORK_SURFACE.md b/local/FORK_SURFACE.md
index d9096345b486..a4a10c659e1d 100644
--- a/local/FORK_SURFACE.md
+++ b/local/FORK_SURFACE.md
@@ -9,7 +9,7 @@
 | H5 | TODO | TODO | TODO |
 | H6 | TODO | TODO | TODO |
 | H7 | TODO | TODO | TODO |
-| H8 | `codex-rs/core/src/tools/router.rs` | When a call misses the registry and the name contains a dot with no namespace, split it into namespace and name. Works around Ollama flattening the Responses `namespace` field into the name. | TODO |
+| H8 | `codex-rs/core/src/tools/router.rs` | `ToolRouter::unflatten_tool_name` (+1 call in `dispatch_tool_call_with_code_mode_result_inner`): when a call has no/default namespace, its dotted name misses the registry, and the split at the first dot hits, dispatch under the split `(namespace, name)`. Works around Ollama flattening Responses `namespace` into the name (`multi_agent_v1.spawn_agent`). Unconditional: OpenAI names match `^[a-zA-Z0-9_-]+$`, so stock behaviour is unchanged. History keeps the model's original item. 16 upstream lines in router.rs (tests in router_tests.rs). Re-apply: add the method and call it on `tool_name` right after destructuring `call`. | done |
 
 ## H1 re-apply recipe
 
diff --git a/local/fork-surface.toml b/local/fork-surface.toml
index 487098b9083c..85347398e41e 100644
--- a/local/fork-surface.toml
+++ b/local/fork-surface.toml
@@ -1,5 +1,5 @@
 # Upstream paths the fork is allowed to modify.
-allowlist = ["codex-rs/Cargo.toml", "codex-rs/cli/src/main.rs", "codex-rs/cli/build.rs"]
+allowlist = ["codex-rs/Cargo.toml", "codex-rs/cli/src/main.rs", "codex-rs/cli/build.rs", "codex-rs/core/src/tools/router.rs", "codex-rs/core/src/tools/router_tests.rs"]
 generated = ["codex-rs/Cargo.lock"]
 
 [budget]