Merge commit 'refs/codex/unblock/master-current' into HEAD

# Conflicts:
#	docs/event-producer-consumer.md
#	examples/acp-agent/tests/snapshots/bash-spill/session.jsonl
#	examples/acp-agent/tests/snapshots/escalation-approved/session.jsonl
#	examples/acp-agent/tests/snapshots/escalation-rejected/session.jsonl
#	examples/acp-agent/tests/snapshots/fs-escalation-approved/session.jsonl
#	examples/acp-agent/tests/snapshots/hook-cc-pretool-ask/session.jsonl
#	packages/context/workspace-context/tests/workspace-context.spec.ts
#	packages/core/agent/src/index.ts
#	packages/support/invariants/tests/invariants.spec.ts
#	packages/ui/acp/src/index.ts
#	packages/ui/tui/tests/harness.ts
#	packages/ui/tui/tests/tui.spec.ts

packages/core/agent/src/llm-target.ts

@@ -0,0 +1,66 @@
+/**
+ * Agent-scoped provider/model target snapshot shared by interactive front doors.
+ * @module @deepseek-ai/dsh-agent/llm-target
+ */
+
+import type { Context } from 'cordis'
+import type { LlmCallConfig } from '@deepseek-ai/dsh-llm'
+
+/** Complete provider/model route selected for one live agent. */
+export interface AgentLlmTarget {
+  /** Registered provider route. */
+  provider: string
+  /** Provider-owned model id. */
+  model: string
+}
+
+/** Mutable selection plus the target captured for the current step. */
+export interface AgentLlmTargetRef {
+  /** Target selected for the next step that enters prompt assembly. */
+  current: AgentLlmTarget | undefined
+  /** Target captured when the current step entered prompt assembly. */
+  assembled: AgentLlmTarget | undefined
+}
+
+/**
+ * Couple one mutable target to agent-scoped prompt assembly and request routing.
+ * Prompt assembly snapshots the selected pair before delegating, then applies
+ * both prompt variables and request config to that snapshot so a concurrent
+ * switch takes effect on a later step instead of splitting the two surfaces.
+ *
+ * @param agentCtx - The target agent's scoped context.
+ * @param target - Mutable selection owned by the calling front door.
+ * @returns Disposer for both scoped waterfall listeners.
+ */
+export function installAgentLlmTarget(agentCtx: Context, target: AgentLlmTargetRef): () => void {
+  const disposeAssembly = agentCtx.on('system-prompt/assemble', async (_assembly, _context, next) => {
+    const selected = target.current
+    const assembled = await next()
+    target.assembled = selected
+    if (selected === undefined) return assembled
+    return {
+      ...assembled,
+      variables: {
+        ...assembled.variables,
+        provider: selected.provider,
+        model: selected.model,
+      },
+    }
+  })
+  const disposeRequest = agentCtx.on(
+    'agent/request',
+    async (_agent, _turn, _step, _config, _signal, next): Promise<LlmCallConfig> => {
+      const resolved = await next()
+      const selected = target.assembled
+      return selected === undefined ? resolved : {
+        ...resolved,
+        provider: selected.provider,
+        model: selected.model,
+      }
+    },
+  )
+  return () => {
+    disposeAssembly()
+    disposeRequest()
+  }
+}