Subagent completion notification shows UUID agent_path instead of nickname in 0.131.0

[maizaAvaro]

What version of Codex is running?

0.131.0

Which model were you using?

Observed in a Codex CLI/API-backed session using spawned subagents. The exact model should not be material to the display issue.

What OS are you running?

Linux

What happened?

After upgrading from 0.130.0 to 0.131.0, spawned subagents no longer consistently display their friendly nickname in later notifications/completion events. The spawn response still includes a nickname, but the completion notification surfaces the UUID-like agent_path instead.

Example from a session:

{"agent_id":"019e42da-a5f5-71e0-b291-9b5a86182c89","nickname":"Aristotle"}

Later notification for the same subagent:

{"agent_path":"019e42da-a5f5-71e0-b291-9b5a86182c89","status":{"completed":"..."}}

In 0.130.0, subagent names were displayed as friendly names in this workflow, e.g. famous scientist/mathematician/author-style names. In 0.131.0, the UI/event surface is exposing the stable ID in places where the nickname was expected.

This looks possibly related to #21870, which changed TUI agent metadata hydration to avoid blocking during agent fan-out. That PR says nickname/role metadata is now filled from ThreadStarted and picker refreshes when available. This symptom looks like a fallback path is rendering agent_path/thread ID even though the nickname is available from spawn metadata.

Steps to reproduce

1. Run Codex CLI 0.131.0.
2. Spawn a subagent.
3. Observe that the spawn result includes both an ID and a friendly nickname.
4. Wait for the subagent to complete.
5. Observe the completion/subagent notification.

Expected behavior

If a subagent nickname is available, subsequent subagent notifications/completion messages should display or include that nickname consistently, with UUID/thread ID as secondary trace metadata at most.

Actual behavior

The later notification displays the UUID-like agent_path instead of the friendly nickname, even though the spawn result included the nickname.

Why this matters

The nickname is much easier to track in multi-agent sessions. Showing raw UUIDs makes subagent status updates harder to scan and appears like a regression from 0.130.0.

Possible cause

This may be a metadata hydration/cache fallback issue introduced by the 0.131.0 TUI/app-server changes, especially #21870. The local receiver-thread cache may not be populated or consulted for the completion notification path, so the renderer falls back to agent_path.

Additional context

This was noticed alongside other 0.131.0 sandbox/TUI behavior changes, but the nickname issue is independent: the subagent itself completed successfully, and the spawn result did include the nickname.

[maizaAvaro]

I know this is trivial, but I actually enjoyed seeing the names, even if front-surfacing UUIDs makes debugging complex parallel workflows a much easier query... ymmv, but why not both?
I fully expect this to get lost in Cthulhu's backlog, but an effort was made nonetheless.

[jshaofa-ui]

Technical Solution

Fix: Subagent Completion Notification Shows UUID agent_path Instead of Nickname

Issue Summary

Bug: After upgrading from 0.130.0 to 0.131.0, spawned subagents no longer consistently display their friendly nickname in completion notifications. The spawn response includes both an agent_id and a friendly nickname, but the completion notification surfaces the UUID-like agent_path instead.

Root Cause: The collab_agent_metadata cache in ChatWidget must be populated BEFORE any notification referencing the thread is processed. In 0.131.0, changes from PR #21870 (TUI agent metadata hydration) altered the timing of metadata population. If the completion notification arrives before set_collab_agent_metadata() is called for the subagent's thread, the renderer falls back to showing agent_path (UUID) instead of the nickname.

Regression: This worked in 0.130.0. The spawn result includes the nickname, but the completion notification path doesn't consult the spawn metadata — it only checks the collab_agent_metadata cache.

Location: codex-rs/tui/src/chatwidget.rs (metadata cache) + codex-rs/tui/src/app/thread_events.rs (notification handling)

---

Root Cause Analysis

Nickname Flow

1. Spawn: Subagent is spawned with agent_id and nickname:

   {"agent_id":"019e42da-a5f5-71e0-b291-9b5a86182c89","nickname":"Aristotle"}

2. Metadata Cache Population: ChatWidget::set_collab_agent_metadata() should be called to cache the nickname:

   self.collab_agent_metadata.insert(thread_id, AgentMetadata {
       agent_nickname: Some("Aristotle".to_string()),
       agent_role: ...,
   });

3. Completion Notification: When the subagent completes:

   {"agent_path":"019e42da-a5f5-71e0-b291-9b5a86182c89","status":{"completed":"..."}}

   The renderer looks up collab_agent_metadata(thread_id). If found, displays nickname. If NOT found, falls back to agent_path.

The Bug

In 0.131.0, the metadata cache population was moved to a later point in the lifecycle (PR #21870). If the completion notification arrives before the cache is populated, the renderer falls back to agent_path.

The issue is a race condition between:

• set_collab_agent_metadata() (populates the cache)
• TurnCompleted notification processing (reads the cache)

Evidence

• The spawn response DOES include the nickname
• The issue only appears in 0.131.0 (regression)
• Related to PR Avoid blocking TUI on agent metadata hydration #21870 which changed metadata hydration timing
• The fallback path renders agent_path when cache miss occurs

---

Proposed Fix

Fix 1: Populate metadata cache from spawn response immediately

File: codex-rs/tui/src/app/thread_routing.rs or wherever subagent spawn is handled

// When a subagent is spawned, immediately cache its metadata
// BEFORE any notifications can arrive
fn handle_thread_spawn(&mut self, spawn_response: ThreadSpawnResponse) {
    let thread_id = spawn_response.thread_id.clone();
    let nickname = spawn_response.nickname.clone();
    let role = spawn_response.role.clone();
    
    // Cache metadata IMMEDIATELY, before processing any other events
    if let Some(chatwidget) = self.chatwidgets.get_mut(&thread_id) {
        chatwidget.set_collab_agent_metadata(
            thread_id.clone(),
            nickname,
            role,
        );
    }
    
    // Also cache in the navigation/picker layer
    self.upsert_agent_picker_thread(thread_id, nickname, role);
}

Fix 2: Fall back to spawn metadata in completion notification renderer

File: codex-rs/tui/src/multi_agents.rs (or wherever completion is rendered)

fn render_subagent_completion(
    &self,
    agent_path: &str,
    completion_status: &CompletionStatus,
) -> Line {
    // Try cache first
    if let Some(metadata) = self.collab_agent_metadata.get(agent_path) {
        if let Some(nickname) = &metadata.agent_nickname {
            return self.render_with_nickname(nickname, &metadata.agent_role);
        }
    }
    
    // Fall back to spawn metadata (stored at spawn time)
    if let Some(spawn_meta) = self.spawn_metadata_cache.get(agent_path) {
        return self.render_with_nickname(&spawn_meta.nickname, &spawn_meta.role);
    }
    
    // Last resort: show agent_path
    Line::from(format!("Agent {} completed", agent_path))
}

Fix 3: Ensure metadata is available from ThreadStarted notification

The ThreadStarted notification includes agent_nickname. Ensure this is cached before any completion notification can be processed:

// In thread_events.rs, when ThreadStarted is received:
ServerNotification::ThreadStarted(turn) => {
    if let Some(nickname) = &turn.agent_nickname {
        self.chatwidget.set_collab_agent_metadata(
            turn.turn.id.clone(),
            Some(nickname.clone()),
            turn.agent_role.clone(),
        );
    }
    self.active_turn_id = Some(turn.turn.id.clone());
}

---

Files Changed

File	Change
codex-rs/tui/src/app/thread_routing.rs	Cache metadata immediately on spawn
codex-rs/tui/src/app/thread_events.rs	Cache metadata on ThreadStarted notification
codex-rs/tui/src/multi_agents.rs	Add spawn metadata fallback in completion renderer
codex-rs/tui/src/chatwidget.rs	No change needed (cache API already correct)

---

Risk Assessment

• Risk Level: Low (UI-only fix, no data loss risk)
• Impact: Improves multi-agent session usability
• Migration: None needed

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Solution developed through automated analysis. Happy to discuss further or provide PR if needed.