[Juliusolsson05]

What

Replaces the dead generic Agent tool card in the feed with a live subagent fleet view: see how many subagents are running at once, and expand any one to watch what it's doing in real time.

Before — an Agent spawn rendered as a static generic tool card (just the name + description, never updating):

⏺ Agent
  ⎿ Sub-agent flow correlation feasibility

After — sibling spawns group under a live header; each row drills in to its tool-call timeline:

⏺ Spawned 4 agents          ◐ 2 running · ✓ 2 done
  ├ ◐ Explore   Render integration points for nested feed     12 tools · 0:42
  └ ✓ Explore   Current active-agent showcase surfaces        25 tools · done

  └ ▾ ◐ Explore  Render integration points…   12 tools · 0:42
        ⏺ Read   Block.tsx
        ⏺ Grep   "tool_use"        18 matches
        ◐ analyzing render model…

How

The data was already on disk, never read. Claude Code writes each subagent's full transcript live to <sessionDir>/subagents/agent-<id>.jsonl, with a sidecar agent-<id>.meta.json carrying { agentType, description, toolUseId }. toolUseId matches the parent Agent tool_use block id exactly — a deterministic join key, no wire/heuristic correlation needed.

• Main process (src/main/subagents/): a per-session polling watcher tails the subagents/ dir, parses appended JSONL incrementally (byte offsets), and derives a SubAgentState per toolUseId (status, tool-call timeline capped at 40, turn count, elapsed, current activity). The dir is derived from the main transcript's file path (sidesteps providerSessionId-timing); parent tool_result blocks flip a subagent running→done. Pushed via a new session:sub-agents IPC channel.
• Renderer: runtime.subAgents folds the push; SubAgentsContext (provided from Feed, threaded via TileLeaf) exposes it to rows. Block.tsx routes Agent tool_use → TaskSubagentRow (live status + expandable SubagentMiniFeed); ConversationRow groups sibling Agent spawns under SubagentGroupHeader.

All disk I/O is main-side — the renderer never reads files. Disk-sourced means it's durable (survives reload), unlike the ephemeral proxy stream.

Scope / safety

• Strictly additive. When no subagents exist (subAgents = {}) the feed renders exactly as before; a lone Agent spawn renders without a group header. No existing contract touched (there was no Agent renderer before — it fell through to the generic ToolUseRow).
• Codex sessions have no subagents/ dir → inert.
• Bounds: tool-call timeline capped (40) with a +N earlier count; mini-feed lazy (only the data we push); watcher scoped per active session.

Design docs

• Spec: docs/superpowers/specs/2026-06-14-subagent-fleet-rendering-design.md
• Plan: docs/superpowers/plans/2026-06-14-subagent-fleet-rendering.md

Verification

• npx tsc -b tsconfig.web.json and tsconfig.node.json: no new errors (only the 4 pre-existing baseline).
• State-builder logic validated against live subagents/ data on disk (correct tool counts, cap/drop, toolUseId linkage, running/done resolution).
• Live in-app acceptance (spawn parallel agents, expand, completion, reload, no-subagent session) is the reviewer's manual step.

🤖 Generated with Claude Code