Monitor: Agent SDK v0.2.70 upgrade (zero breaking changes)

[Number531]

Context

Upgraded @anthropic-ai/claude-agent-sdk from ^0.2.44 to ^0.2.70 on 2026-03-06. Full analysis in docs/pending-updates/0.2.47-0.2.70-update.md.

What Changed (key features)

• v0.2.51: Memory leak fix (unbounded UUID tracking in long sessions)
• v0.2.51: task_progress events for background agent progress
• v0.2.53: listSessions() API
• v0.2.59: getSessionMessages() with pagination
• v0.2.63: supportedAgents() method; MCP unprefixed tool name fix
• v0.2.69: agent_id/agent_type guaranteed on all hook events; MCP disconnect fix
• v0.2.70: AgentToolInput.subagent_type optional; HTTP MCP 406 fix

What to Monitor

Potential Regressions

• Hook dispatch: Verify SubagentStart/SubagentStop still fire for all 29+ subagents during memo generation
• agent_type values: Confirm string values match existing classifyAgent() patterns in hookSSEBridge.js (25 includes-checks)
• Gate checks: Confirm GATE_CHECK_CONFIGS key matching via agent_id?.includes(type) || agent_type?.includes(type) still works (sdkHooks.js:1203)
• MCP tool availability: Verify domain-scoped MCP tools still register and resolve correctly (especially with unprefixed name fix in v0.2.63)
• SSE event stream: Confirm frontend receives subagent_start, subagent_stop, document_ready, code_execution_* events
• Token costs: Monitor for unexpected increases — upstream Issue #192 (Bash UUID cache bust) may affect caching

Known Upstream Issues (open on anthropics/claude-agent-sdk-typescript)

• #192 — Random UUID in Bash tool description busts input cache
• #188 — 1-hour cache TTL default instead of 5-minute
• #25 — maxThinkingTokens still breaks hooks (unchanged)
• #14 — defer_loading still blocked on upstream

Breaking Change Warning

system:init and result events currently emit 'Task' as the Agent tool name (reverted in v0.2.69). The next minor release will change this to 'Agent' — must audit string matching before upgrading past v0.2.x.

Files Modified

• package.json — ^0.2.44 → ^0.2.70
• src/hooks/sdkHooks.js — added v0.2.69+ comments on agent_id/agent_type guarantees
• src/utils/hookSSEBridge.js — updated NOTE block re: agent field guarantees, agentRegistry fallback context

Validation Plan

1. Run existing test suite (npm test)
2. Run a small memo generation (1-2 documents) and verify:
   • All subagents spawn and complete
   • Gate checks pass
   • SSE events reach frontend
   • No memory growth anomalies
3. Run a full 29-subagent memo and compare token usage against pre-upgrade baseline

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

[Number531]

Update: Upgrade reverted — SDK pinned to v0.2.51

The v0.2.70 upgrade has been reverted. Subagent delegation via the Agent/Task tool is broken in query() mode starting from v0.2.63+ (upstream anthropics/claude-agent-sdk-typescript#210).

• Reversion commit: 7f16be3
• Pinned version: 0.2.51 (exact, no caret)
• Tracking issue: Agent SDK: Subagent delegation broken in query() mode — pinned to v0.2.51 pending upstream fix #32
• Upstream comment: #210 comment

Anthropic engineer responded that it should be fixed on CLI > 2.1.63, but we confirmed the issue persists on v0.2.70 (CLI v2.1.70). Our reproduction posted upstream.

This issue's validation checklist is now moot — re-open and re-execute when #32 is resolved.