chore: enable parallel tc (#7589)

codex-rs/core/src/codex.rs

@@ -2174,21 +2174,11 @@ async fn run_turn(
         .get_model_family()
         .supports_parallel_tool_calls;
 
-    // TODO(jif) revert once testing phase is done.
-    let parallel_tool_calls = model_supports_parallel && sess.enabled(Feature::ParallelToolCalls);
-    let mut base_instructions = turn_context.base_instructions.clone();
-    if parallel_tool_calls {
-        static INSTRUCTIONS: &str = include_str!("../templates/parallel/instructions.md");
-        let family = turn_context.client.get_model_family();
-        let mut new_instructions = base_instructions.unwrap_or(family.base_instructions);
-        new_instructions.push_str(INSTRUCTIONS);
-        base_instructions = Some(new_instructions);
-    }
     let prompt = Prompt {
         input,
         tools: router.specs(),
-        parallel_tool_calls,
+        parallel_tool_calls: model_supports_parallel && sess.enabled(Feature::ParallelToolCalls),
-        base_instructions_override: base_instructions,
+        base_instructions_override: turn_context.base_instructions.clone(),
         output_schema: turn_context.final_output_json_schema.clone(),
     };
 

codex-rs/core/src/features.rs

@@ -268,6 +268,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::Stable,
         default_enabled: true,
     },
+    FeatureSpec {
+        id: Feature::ParallelToolCalls,
+        key: "parallel",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
     FeatureSpec {
         id: Feature::ViewImageTool,
         key: "view_image_tool",

codex-rs/core/src/openai_models/model_family.rs

@@ -259,7 +259,7 @@ pub fn find_family_for_model(slug: &str) -> ModelFamily {
             base_instructions: GPT_5_1_CODEX_MAX_INSTRUCTIONS.to_string(),
             apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
             shell_type: ConfigShellToolType::ShellCommand,
-            supports_parallel_tool_calls: true,
+            supports_parallel_tool_calls: false,
             support_verbosity: false,
             truncation_policy: TruncationPolicy::Tokens(10_000),
             context_window: Some(CONTEXT_WINDOW_272K),
@@ -275,7 +275,7 @@ pub fn find_family_for_model(slug: &str) -> ModelFamily {
             base_instructions: GPT_5_CODEX_INSTRUCTIONS.to_string(),
             apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
             shell_type: ConfigShellToolType::ShellCommand,
-            supports_parallel_tool_calls: true,
+            supports_parallel_tool_calls: false,
             support_verbosity: false,
             truncation_policy: TruncationPolicy::Tokens(10_000),
             context_window: Some(CONTEXT_WINDOW_272K),

codex-rs/core/templates/parallel/instructions.md

@@ -1,13 +0,0 @@
-
-## Exploration and reading files
-
-- **Think first.** Before any tool call, decide ALL files/resources you will need.
-- **Batch everything.** If you need multiple files (even from different places), read them together.
-- **multi_tool_use.parallel** Use `multi_tool_use.parallel` to parallelize tool calls and only this.
-- **Only make sequential calls if you truly cannot know the next file without seeing a result first.**
-- **Workflow:** (a) plan all needed reads → (b) issue one parallel batch → (c) analyze results → (d) repeat if new, unpredictable reads arise.
-
-**Additional notes**:
-* Always maximize parallelism. Never read files one-by-one unless logically unavoidable.
-* This concern every read/list/search operations including, but not only, `cat`, `rg`, `sed`, `ls`, `git show`, `nl`, `wc`, ...
-* Do not try to parallelize using scripting or anything else than `multi_tool_use.parallel`.