app-server: add v2 filesystem APIs (#14245)

Add a protocol-level filesystem surface to the v2 app-server so Codex
clients can read and write files, inspect directories, and subscribe to
path changes without relying on host-specific helpers.

High-level changes:
- define the new v2 fs/readFile, fs/writeFile, fs/createDirectory,
fs/getMetadata, fs/readDirectory, fs/remove, fs/copy RPCs
- implement the app-server handlers, including absolute-path validation,
base64 file payloads, recursive copy/remove semantics
- document the API, regenerate protocol schemas/types, and add
end-to-end tests for filesystem operations, copy edge cases

Testing plan:
- validate protocol serialization and generated schema output for the
new fs request, response, and notification types
- run app-server integration coverage for file and directory CRUD paths,
metadata/readDirectory responses, copy failure modes, and absolute-path
validation

codex-rs/app-server-protocol/schema/json/v2/FsCopyParams.json

@@ -0,0 +1,38 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "Copy a file or directory tree on the host filesystem.",
+  "properties": {
+    "destinationPath": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute destination path."
+    },
+    "recursive": {
+      "description": "Required for directory copies; ignored for file copies.",
+      "type": "boolean"
+    },
+    "sourcePath": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute source path."
+    }
+  },
+  "required": [
+    "destinationPath",
+    "sourcePath"
+  ],
+  "title": "FsCopyParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsCopyResponse.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "description": "Successful response for `fs/copy`.",
+  "title": "FsCopyResponse",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsCreateDirectoryParams.json

@@ -0,0 +1,32 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "Create a directory on the host filesystem.",
+  "properties": {
+    "path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute directory path to create."
+    },
+    "recursive": {
+      "description": "Whether parent directories should also be created. Defaults to `true`.",
+      "type": [
+        "boolean",
+        "null"
+      ]
+    }
+  },
+  "required": [
+    "path"
+  ],
+  "title": "FsCreateDirectoryParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsCreateDirectoryResponse.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "description": "Successful response for `fs/createDirectory`.",
+  "title": "FsCreateDirectoryResponse",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsGetMetadataParams.json

@@ -0,0 +1,25 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "Request metadata for an absolute path.",
+  "properties": {
+    "path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute path to inspect."
+    }
+  },
+  "required": [
+    "path"
+  ],
+  "title": "FsGetMetadataParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsGetMetadataResponse.json

@@ -0,0 +1,32 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "description": "Metadata returned by `fs/getMetadata`.",
+  "properties": {
+    "createdAtMs": {
+      "description": "File creation time in Unix milliseconds when available, otherwise `0`.",
+      "format": "int64",
+      "type": "integer"
+    },
+    "isDirectory": {
+      "description": "Whether the path currently resolves to a directory.",
+      "type": "boolean"
+    },
+    "isFile": {
+      "description": "Whether the path currently resolves to a regular file.",
+      "type": "boolean"
+    },
+    "modifiedAtMs": {
+      "description": "File modification time in Unix milliseconds when available, otherwise `0`.",
+      "format": "int64",
+      "type": "integer"
+    }
+  },
+  "required": [
+    "createdAtMs",
+    "isDirectory",
+    "isFile",
+    "modifiedAtMs"
+  ],
+  "title": "FsGetMetadataResponse",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsReadDirectoryParams.json

@@ -0,0 +1,25 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "List direct child names for a directory.",
+  "properties": {
+    "path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute directory path to read."
+    }
+  },
+  "required": [
+    "path"
+  ],
+  "title": "FsReadDirectoryParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsReadDirectoryResponse.json

@@ -0,0 +1,43 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "FsReadDirectoryEntry": {
+      "description": "A directory entry returned by `fs/readDirectory`.",
+      "properties": {
+        "fileName": {
+          "description": "Direct child entry name only, not an absolute or relative path.",
+          "type": "string"
+        },
+        "isDirectory": {
+          "description": "Whether this entry resolves to a directory.",
+          "type": "boolean"
+        },
+        "isFile": {
+          "description": "Whether this entry resolves to a regular file.",
+          "type": "boolean"
+        }
+      },
+      "required": [
+        "fileName",
+        "isDirectory",
+        "isFile"
+      ],
+      "type": "object"
+    }
+  },
+  "description": "Directory entries returned by `fs/readDirectory`.",
+  "properties": {
+    "entries": {
+      "description": "Direct child entries in the requested directory.",
+      "items": {
+        "$ref": "#/definitions/FsReadDirectoryEntry"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "entries"
+  ],
+  "title": "FsReadDirectoryResponse",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsReadFileParams.json

@@ -0,0 +1,25 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "Read a file from the host filesystem.",
+  "properties": {
+    "path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute path to read."
+    }
+  },
+  "required": [
+    "path"
+  ],
+  "title": "FsReadFileParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsReadFileResponse.json

@@ -0,0 +1,15 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "description": "Base64-encoded file contents returned by `fs/readFile`.",
+  "properties": {
+    "dataBase64": {
+      "description": "File contents encoded as base64.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "dataBase64"
+  ],
+  "title": "FsReadFileResponse",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsRemoveParams.json

@@ -0,0 +1,39 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "Remove a file or directory tree from the host filesystem.",
+  "properties": {
+    "force": {
+      "description": "Whether missing paths should be ignored. Defaults to `true`.",
+      "type": [
+        "boolean",
+        "null"
+      ]
+    },
+    "path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute path to remove."
+    },
+    "recursive": {
+      "description": "Whether directory removal should recurse. Defaults to `true`.",
+      "type": [
+        "boolean",
+        "null"
+      ]
+    }
+  },
+  "required": [
+    "path"
+  ],
+  "title": "FsRemoveParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsRemoveResponse.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "description": "Successful response for `fs/remove`.",
+  "title": "FsRemoveResponse",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsWriteFileParams.json

@@ -0,0 +1,30 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "definitions": {
+    "AbsolutePathBuf": {
+      "description": "A path that is guaranteed to be absolute and normalized (though it is not guaranteed to be canonicalized or exist on the filesystem).\n\nIMPORTANT: When deserializing an `AbsolutePathBuf`, a base path must be set using [AbsolutePathBufGuard::new]. If no base path is set, the deserialization will fail unless the path being deserialized is already absolute.",
+      "type": "string"
+    }
+  },
+  "description": "Write a file on the host filesystem.",
+  "properties": {
+    "dataBase64": {
+      "description": "File contents encoded as base64.",
+      "type": "string"
+    },
+    "path": {
+      "allOf": [
+        {
+          "$ref": "#/definitions/AbsolutePathBuf"
+        }
+      ],
+      "description": "Absolute path to write."
+    }
+  },
+  "required": [
+    "dataBase64",
+    "path"
+  ],
+  "title": "FsWriteFileParams",
+  "type": "object"
+}

codex-rs/app-server-protocol/schema/json/v2/FsWriteFileResponse.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "description": "Successful response for `fs/writeFile`.",
+  "title": "FsWriteFileResponse",
+  "type": "object"
+}