feat(runtime): rebuild ACP execution as plugin adapters

apps/desktop/package.json

@@ -33,7 +33,7 @@
     "build:preload": "esbuild src/preload/preload.ts --bundle --platform=node --format=cjs --outfile=dist/preload/preload.cjs --external:electron",
     "build:overlay": "node ../../scripts/build-cursor-overlay.mjs",
     "build:renderer": "vite build && node scripts/check-renderer-entry-output.mjs && node ../../scripts/check-third-party-notices.mjs",
-    "build:workspace-deps": "npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/mcp run build && npm --workspace @maka/runtime run build && npm --workspace @maka/runtime-host run build && npm --workspace @maka/computer-use run build && npm --workspace @maka/ui run build",
+    "build:workspace-deps": "npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/mcp run build && npm --workspace @maka/runtime run build && npm --workspace @maka/acp-executor-plugin run build && npm --workspace @maka/antigravity-acp-plugin run build && npm --workspace @maka/runtime-host run build && npm --workspace @maka/computer-use run build && npm --workspace @maka/ui run build",
     "package:macos-arm64": "electron-builder --config electron-builder.config.mjs --mac dmg zip --arm64 --publish never",
     "package:macos-x64": "electron-builder --config electron-builder.config.mjs --mac dmg zip --x64 --publish never",
     "package:windows-x64": "electron-builder --config electron-builder.config.mjs --win nsis zip --x64 --publish never",

docs/antigravity-acp-plugin-rebuild.md

@@ -0,0 +1,115 @@
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you under the Apache License, Version 2.0 (the
+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing,
+  software distributed under the License is distributed on an
+  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+# Antigravity ACP Plugin rebuild
+
+## Why PR #5224 cannot be carried forward unchanged
+
+PR #5224 predates the Plugin-backed Session executor architecture from #5283. It adds a dedicated
+ACP backend and then threads external-Agent identity, model catalogs, session control, protocol
+operations, Desktop bridges, and Composer state through the Host. The branch changes 139 files and
+adds roughly 7,800 lines relative to its current merge base.
+
+The new architecture already owns those cross-cutting responsibilities generically:
+
+| Concern | PR #5224 implementation | Current `main` authority |
+| --- | --- | --- |
+| Session routing | `AcpAgentBackend` registered in Host execution composition | `executorId` plus `PluginExecutorBackend` |
+| Executor lifetime | ACP-specific Host residency and backend registry logic | Plugin Entry generation, retirement, and executor binding |
+| Transcript | ACP event conversion plus new external-session fields | Generic executor events enter the canonical Session stream |
+| Process and credentials | Runtime Host ACP module | Contributing Plugin; opaque to Maka Runtime |
+| Child/Graph execution | ACP-specific guards | Generic executor propagation from #5283 |
+| Model choice | Provider catalog protocol and ACP-specific Desktop state | Plugin configuration for this rebuild; a generic executor-configuration capability can follow |
+| Permission choices | ACP backend reaches `HostedInteractionBridge` directly | Generic executor permission request bridged by `PluginExecutorBackend` |
+
+Keeping both designs would create two backend authorities, two lifecycle paths, and provider-specific
+state in otherwise generic Session and Desktop code.
+
+## Rebuilt boundary
+
+The rebuild is split into an intermediate runtime and a thin product adapter:
+
+```text
+PluginExecutorService
+  -> ACP Runtime Plugin (`ctx.acp`)
+       -> Antigravity adapter
+       -> future ACP adapter
+```
+
+`@maka/acp-executor-plugin` owns the shared ACP protocol implementation. Its `acp-runtime` profile
+Entry provides `ctx.acp`; external-Agent Entries are mounted below it and call
+`ctx.acp.register(ctx, ...)`, explicitly preserving the consuming Entry identity across independently
+bundled Plugin generations.
+The service wraps every adapter as the generic executor contribution introduced by #5283, so it is
+not a second backend or routing authority.
+
+`@maka/antigravity-acp-plugin` now contains only executable/helper validation, Antigravity environment
+policy, and optional initial model configuration. The shared runtime owns:
+
+- ACP initialize, Session creation, prompt, cancellation, and cleanup;
+- one retained ACP process/Session per Maka conversation;
+- ACP file callbacks with workspace and symlink containment;
+- ACP tool/thought/text projection into generic executor events;
+- ACP permission option identity and settlement;
+- generic initial ACP configuration validation/application;
+- durable history-only detection so a Host/Plugin restart cannot silently fork an existing external
+  conversation into a new ACP Session.
+
+The Antigravity adapter owns:
+
+- the official Antigravity executable and helper paths;
+- the `ANTIGRAVITY_HARNESS_PATH`, proxy-bypass, and browser environment policy;
+- the optional model value passed to the shared initial-configuration mechanism.
+
+The Host owns only executor visibility and binding, Maka Session/run identity, canonical event
+persistence, hosted form admission, and Plugin retirement. No ACP process, credential, or external
+Session identifier crosses the Plugin boundary.
+
+## Deliberately not ported
+
+The rebuild does not carry forward the PR #5224 provider catalog protocol, external-Agent Session
+protocol, renderer hot cache, draft/prewarm Session lease, ACP-specific backend registry branches,
+custom storage fields, CLI transcript branches, model-picker forks, or visual-workaround changes.
+Those components either duplicate #5283 or solve UI/configuration concerns that should be added as a
+generic Plugin executor capability rather than an Antigravity branch.
+
+The installation and authentication surface already merged in #5164 remains the producer of setup
+facts. `HostBuiltinExternalAgentPluginCoordinator` projects the saved executable into system-managed
+Plugin packages and a configured adapter Entry. The projection is content-addressed and idempotent:
+it installs the ACP runtime before the adapter, replaces only a changed package layer, restores the
+same state after Host restart, and removes the adapter before its runtime when the setting is cleared.
+Adapter code never reads RuntimePolicy.
+
+Both production `plugin.mjs` bundles are release dependencies of Runtime Host, so the same path is
+available to Desktop-owned and managed/remote Hosts. The installed ACP service uses an isolated
+Context label and an explicit consumer Context instead of relying on cross-bundle `Service`
+`instanceof` identity.
+
+## Remaining PR 2 work
+
+PR 2 remains one pull request, organized as four reviewable producer-to-consumer sets:
+
+1. Setup facts to active executor: implemented by the system-managed package projection above;
+   readiness projection still needs the bounded provider probe used by Desktop.
+2. Provider catalog to Desktop choice to first prompt: add a generic executor catalog/configuration
+   contract and integrate it into the existing model menu without creating preview Sessions.
+3. ACP updates/interactions to canonical conversation settlement: add generic Agent questions and
+   complete race, unsupported-input, and rendering coverage.
+4. Process continuity facts to task readiness: project history-only/process-loss into generic Session
+   and Desktop readiness and finish controlled official-provider acceptance.

package.json

@@ -18,6 +18,8 @@
     "packages/storage",
     "packages/mcp",
     "packages/runtime",
+    "packages/acp-executor-plugin",
+    "packages/antigravity-acp-plugin",
     "packages/runtime-host",
     "packages/eval",
     "packages/computer-use",
@@ -46,8 +48,8 @@
     "dev:full": "npm run build && npm --workspace @maka/desktop run start",
     "dev:full:peer": "npm run build && npm --workspace @maka/desktop run start:peer",
     "cli:dev": "node packages/cli/dist/dev-cli.js",
-    "build": "npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/mcp run build && npm --workspace @maka/runtime run build && npm --workspace @maka/runtime-host run build && npm --workspace @maka/computer-use run build && npm --workspace @maka/eval run build && npm --workspace maka-agent run build && npm --workspace @maka/ui run build && npm --workspace @maka/desktop run build",
-    "build:test": "npm run clean && npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/mcp run build && npm --workspace @maka/runtime run build && npm --workspace @maka/runtime-host run build && npm --workspace @maka/computer-use run build && npm --workspace @maka/eval run build && npm --workspace maka-agent run build && npm --workspace @maka/ui run build && npm --workspace @maka/desktop run build:test",
+    "build": "npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/mcp run build && npm --workspace @maka/runtime run build && npm --workspace @maka/acp-executor-plugin run build && npm --workspace @maka/antigravity-acp-plugin run build && npm --workspace @maka/runtime-host run build && npm --workspace @maka/computer-use run build && npm --workspace @maka/eval run build && npm --workspace maka-agent run build && npm --workspace @maka/ui run build && npm --workspace @maka/desktop run build",
+    "build:test": "npm run clean && npm --workspace @maka/core run build && npm --workspace @maka/storage run build && npm --workspace @maka/mcp run build && npm --workspace @maka/runtime run build && npm --workspace @maka/acp-executor-plugin run build && npm --workspace @maka/antigravity-acp-plugin run build && npm --workspace @maka/runtime-host run build && npm --workspace @maka/computer-use run build && npm --workspace @maka/eval run build && npm --workspace maka-agent run build && npm --workspace @maka/ui run build && npm --workspace @maka/desktop run build:test",
     "clean": "node scripts/clean-build.mjs",
     "rebuild": "npm run clean && npm run build",
     "check:stale": "node scripts/check-stale-dist.mjs",

packages/acp-executor-plugin/README.md

@@ -0,0 +1,33 @@
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you under the Apache License, Version 2.0 (the
+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing,
+  software distributed under the License is distributed on an
+  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+# ACP Executor Runtime Plugin
+
+This package is the shared ACP transport and lifecycle layer. It provides `ctx.acp` to child Plugin
+Entries. An external Agent package supplies only an `AcpAgentAdapter`; the service turns that adapter
+into the generic executor contribution introduced by #5283.
+
+Installing this package creates the `acp-runtime` profile Entry. Keep adapter Entries below it so the
+service follows normal Plugin Context inheritance. The Host remains unaware of ACP and sees only
+`ctx.executors` registrations.
+
+Adapter packages register with `ctx.acp.register(ctx, adapter, config)`. Passing the adapter Entry's
+Context explicitly is part of the package ABI: production packages are separate self-contained
+bundles, and the shared runtime must register the executor against the consumer's scope rather than
+against its parent Entry.

packages/acp-executor-plugin/maka.composition.yml

@@ -0,0 +1,24 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+- type: insert
+  rootId: profile
+  entry:
+    id: acp-runtime
+    packageId: acp-executor
+    isolate:
+      acp: true

packages/acp-executor-plugin/maka.extension.json

@@ -0,0 +1,13 @@
+{
+  "schemaVersion": 1,
+  "id": "acp-executor",
+  "displayName": "ACP Executor Runtime",
+  "description": "Shared ACP protocol and process runtime for external Agent adapter plugins.",
+  "runtime": {
+    "entry": "dist/plugin.mjs"
+  },
+  "composition": {
+    "patch": "maka.composition.yml",
+    "structuralDependencies": []
+  }
+}

packages/acp-executor-plugin/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "@maka/acp-executor-plugin",
+  "version": "0.1.0",
+  "license": "Apache-2.0",
+  "description": "Shared ACP runtime service for Maka executor adapter plugins.",
+  "type": "module",
+  "private": true,
+  "files": [
+    "dist"
+  ],
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": "./dist/index.js",
+    "./plugin": "./dist/plugin.mjs"
+  },
+  "scripts": {
+    "clean": "node ../../scripts/clean-paths.mjs dist tsconfig.tsbuildinfo",
+    "build": "tsc -p tsconfig.json && esbuild src/index.ts --bundle --platform=node --format=esm --target=node22 --outfile=dist/plugin.mjs",
+    "typecheck": "tsc -p tsconfig.json --noEmit",
+    "test:dist": "node --test \"dist/**/*.test.js\""
+  },
+  "dependencies": {
+    "@agentclientprotocol/sdk": "1.4.0"
+  },
+  "devDependencies": {
+    "@maka/runtime": "0.1.0"
+  }
+}