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/tools/src/invariant.ts

@@ -0,0 +1,69 @@
+/** Package-owned tool-pipeline invariants. @module @deepseek-ai/dsh-tools/invariant */
+
+import type { Context } from 'cordis'
+import type { InvariantFailure, InvariantInstaller } from '@deepseek-ai/dsh-invariants'
+import type { ToolExecution, ToolExecutionResult } from './index.ts'
+
+const PACKAGE_NAME = '@deepseek-ai/dsh-tools'
+
+/** Cordis companion plugin name. */
+export const name = 'tools-invariant'
+/** Service required before the companion can reserve package ownership. */
+export const inject = ['invariants']
+
+type ToolStage = 'pre' | 'execute' | 'post'
+
+/** Validate the immutable final execution/result snapshot. */
+function validateResult(
+  exec: Readonly<ToolExecution>,
+  result: Readonly<ToolExecutionResult>,
+  fail: InvariantFailure,
+): void {
+  if (!Object.isFrozen(exec)) fail('tools/result execution must be frozen before publication')
+  if (!Object.isFrozen(result) || !Object.isFrozen(result.content)) {
+    fail('tools/result outcome and content must be frozen before publication')
+  }
+  if (exec.name.length === 0 || String(exec.callId).length === 0) {
+    fail('tools/result execution must carry non-empty name and callId')
+  }
+}
+
+/** Install monotonic pipeline and final-snapshot checks. */
+const install: InvariantInstaller = (ctx, fail) => {
+  const stages = new WeakMap<object, ToolStage>()
+  ctx.on('internal/dispatch', (_mode, eventName, args) => {
+    if (eventName === 'tools/pre-execute') {
+      const exec = args[0] as ToolExecution
+      if (stages.has(exec)) fail('tools/pre-execute repeated for one execution')
+      stages.set(exec, 'pre')
+      return
+    }
+    if (eventName === 'tools/execute') {
+      const exec = args[0] as ToolExecution
+      if (stages.get(exec) !== 'pre') fail('tools/execute must follow tools/pre-execute')
+      stages.set(exec, 'execute')
+      return
+    }
+    if (eventName === 'tools/post-execute') {
+      const exec = args[0] as ToolExecution
+      const previous = stages.get(exec)
+      if (previous !== 'pre' && previous !== 'execute') {
+        fail('tools/post-execute must follow tools/pre-execute or tools/execute')
+      }
+      stages.set(exec, 'post')
+      return
+    }
+    if (eventName !== 'tools/result') return
+    const [exec, result] = args as [Readonly<ToolExecution>, Readonly<ToolExecutionResult>]
+    validateResult(exec, result, fail)
+    stages.delete(exec)
+  }, { global: true })
+}
+
+/**
+ * Register the tools invariant companion.
+ * @param ctx - Cordis context carrying the invariant service.
+ * @returns the installed registration's disposer after setup succeeds.
+ */
+export const apply = (ctx: Context): Promise<() => void> =>
+  Promise.resolve(ctx.invariants.register(PACKAGE_NAME, install))