Bug

When agent A spawns a cross-agent sub-agent targeting agent B (via sessions_spawn(agentId: "B")), the sub-agent runs under the correct session namespace (agent:B:subagent:<uuid>) but inherits agent A's workspace and persona files instead of agent B's.

Root Cause

Two code paths interact:

1. resolveSpawnedWorkspaceInheritance uses the requester's session key

src/agents/spawned-context.ts:59-74 extracts the agent ID from requesterSessionKey (the caller), not the target agent. For cross-agent spawns this resolves the wrong workspace.

2. Caller's ctx.workspaceDir is passed as explicitWorkspaceDir

src/agents/subagent-spawn.ts:540-554 passes toolSpawnMetadata.workspaceDir (derived from ctx.workspaceDir, the caller's workspace) as explicitWorkspaceDir. This short-circuits the resolution function via its if (explicit) return explicit path before the target agent ID is ever considered.

3. Spawned metadata overrides session-key-based fallback

src/commands/agent.ts:549-551 uses normalizedSpawned.workspaceDir ?? resolveAgentWorkspaceDir(cfg, sessionAgentId). Since spawned metadata always carries the (wrong) workspace, the correct fallback never fires.

Reproduction

1. Configure two agents (pm and ops) with distinct workspaces and identity files
2. Add subagents.allowAgents: ["ops"] to PM's agent config
3. From PM, spawn: sessions_spawn(agentId: "ops", task: "Read IDENTITY.md from your workspace")
4. The sub-agent reads PM's IDENTITY.md instead of Ops'

Expected

Sub-agent should use target agent's workspace (workspace-ops) and persona files.

Actual

Sub-agent uses caller's workspace (workspace-pm) and persona files.

Related

• FEATURE: Per-agent subagents.workspace config #29372 (per-agent subagents.workspace config) — related but different scenario (default sub-agents, not cross-agent)

Files Involved