Mizan codegen substrate: Rust kernel + Rust codegen binary, JS generator deleted

The Mizan codegen substrate moves off JavaScript template-literal emission onto a compiled Rust binary that consumes the same OpenAPI + x-mizan-* IR the JS substrate consumed. Three structural wins fall out of one move: 1. Moat closes. The codegen logic (how `affects` becomes auto-invalidation, how named contexts collapse onto bundled fetches, how the registry-to- Provider mapping is shaped) ships compiled instead of as source bytes in every consumer's node_modules. 2. Pattern F (lines.push append-walls) becomes structurally unauthorable. The emit substrate is askama templates in templates/<target>/*.j2 — actual target-language files with {{ ... }} substitution markers, syntax-highlighted natively, type-checked against the render context structs at compile time. The Rust emit modules build typed render contexts and call .render(); no string-builder surface exists. 3. OpenAPI `default`-bearing fields now emit as non-optional in TS / Python / Rust — the server always populates them, so consumer code reads them without nullable checks. Surfaced by Blazr's typecheck on regeneration. Layout: frontends/mizan-rust/ — Rust port of @mizan/base; #[cfg(feature="pyo3")] exposes PyMizanClient for the Python target. protocol/mizan-codegen/ — codegen binary source + askama templates. protocol/mizan-generate/ — npm-package shim. bin/launcher.mjs dispatches to the platform-appropriate prebuilt binary. Old generator/ JS tree deleted. tests/rust/ — wire-parity drivers. drive_kernel exercises raw client.call() / fetch_context(); drive_emitted exercises the typed crate the codegen emits. tests/afi/afi_codegen_app.py — codegen entrypoint module (imports + registers). backends/mizan-fastapi/.../schema.py — adds outputNullable so the Rust codegen can wrap T | None responses in Option<T>. Verification: - 20 mizan-codegen tests green (IR deserialization, byte-equivalent parity vs JS baseline for stage1/rust/python/react/vue/svelte, structural test for channels). - tests/rust/run_wire_parity.py — 12/12 probes green via the Rust binary driving the FastAPI fixture end-to-end. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-17 18:26:32 -04:00
parent c15c6f3e14
commit 43bcf3f26f
114 changed files with 11090 additions and 2342 deletions
--- a/protocol/mizan-codegen/tests/channels_smoke.rs
+++ b/protocol/mizan-codegen/tests/channels_smoke.rs
@@ -0,0 +1,80 @@
+//! Smoke test for the channels target against a synthetic fixture.
+//! The JS channels.mjs runs types through `openapi-typescript` which the
+//! Rust codegen replaces with direct interface emission; byte-equivalence
+//! against the JS baseline is intentionally not the gate. Instead this
+//! test checks structural properties of the emitted output.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use mizan_codegen::config::{Config, SourceConfig};
+use mizan_codegen::emit::CodegenTarget;
+use mizan_codegen::emit::channels::ChannelsTarget;
+use mizan_codegen::fetch::parse_ir_from_str;
+
+
+fn fixture_config() -> Config {
+    Config {
+        project_id: None,
+        output: PathBuf::from("/tmp"),
+        targets: vec!["channels".to_string()],
+        source: SourceConfig { fastapi: None, django: None },
+        rust_kernel: None,
+        rust_crate_name: None,
+    }
+}
+
+
+#[test]
+fn channels_target_emits_expected_files() {
+    let raw = std::fs::read_to_string(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/channels_schema.json"),
+    ).unwrap();
+    let ir = parse_ir_from_str(&raw).unwrap();
+
+    let files = ChannelsTarget.emit(&ir, &fixture_config());
+    assert_eq!(files.len(), 2, "channels target emits 2 files when channels present");
+
+    let by_path: BTreeMap<PathBuf, &str> =
+        files.iter().map(|f| (f.rel_path.clone(), f.content.as_str())).collect();
+
+    let ts = by_path.get(&PathBuf::from("channels.ts"))
+        .expect("channels.ts emitted");
+    for expected in [
+        "export interface ChatChannelParams",
+        "export interface ChatReactMessage",
+        "export interface ChatDjangoMessage",
+        "export interface NotificationsDjangoMessage",
+        "export const CHANNELS = {",
+        "chat: {",
+        "notifications: {",
+        "hasParams: true",
+        "hasParams: false",
+    ] {
+        assert!(ts.contains(expected), "channels.ts must contain {expected:?}");
+    }
+
+    let hooks = by_path.get(&PathBuf::from("channels.hooks.tsx"))
+        .expect("channels.hooks.tsx emitted");
+    for expected in [
+        "import { useChannel, type ChannelSubscription } from 'mizan/channels'",
+        "export function useChatChannel(params: ChatChannelParams)",
+        "export function useNotificationsChannel()",
+        "ChannelSubscription<ChatChannelParams, ChatDjangoMessage, ChatReactMessage>",
+        "ChannelSubscription<Record<string, never>, NotificationsDjangoMessage, never>",
+    ] {
+        assert!(hooks.contains(expected), "channels.hooks.tsx must contain {expected:?}");
+    }
+}
+
+
+#[test]
+fn channels_target_emits_nothing_when_empty() {
+    // AFI fixture has no channels — target should produce zero files.
+    let raw = std::fs::read_to_string(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/afi_schema.json"),
+    ).unwrap();
+    let ir = parse_ir_from_str(&raw).unwrap();
+    let files = ChannelsTarget.emit(&ir, &fixture_config());
+    assert!(files.is_empty(), "no channels → no files");
+}
--- a/protocol/mizan-codegen/tests/fixtures/afi_schema.json
+++ b/protocol/mizan-codegen/tests/fixtures/afi_schema.json
@@ -0,0 +1,685 @@
+{
+  "openapi": "3.1.0",
+  "info": {
+    "title": "mizan Server Functions",
+    "description": "Auto-generated schema for mizan server functions",
+    "version": "1.0.0"
+  },
+  "paths": {
+    "/mizan/echo": {
+      "post": {
+        "summary": "Echoes the input back.",
+        "operationId": "echo",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/echoInput"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/echoOutput"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": false
+        }
+      }
+    },
+    "/mizan/whoami": {
+      "post": {
+        "summary": "Returns the current user identity.",
+        "operationId": "whoami",
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/whoamiOutput"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": false
+        }
+      }
+    },
+    "/mizan/user_profile": {
+      "post": {
+        "summary": "One half of the user context.",
+        "operationId": "userProfile",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/userProfileInput"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/userProfileOutput"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": "user"
+        }
+      }
+    },
+    "/mizan/user_orders": {
+      "post": {
+        "summary": "Other half of the user context \u2014 same param, proves param elevation.",
+        "operationId": "userOrders",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/userOrdersInput"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/userOrdersOutput"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": "user"
+        }
+      }
+    },
+    "/mizan/update_profile": {
+      "post": {
+        "summary": "Mutation declaring affects on the user context.",
+        "operationId": "updateProfile",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/updateProfileInput"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/updateProfileOutput"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": false
+        }
+      }
+    },
+    "/mizan/find_user": {
+      "post": {
+        "summary": "Optional return \u2014 exercises Pydantic `T | None` schema introspection.",
+        "operationId": "findUser",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/findUserInput"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "anyOf": [
+                    {
+                      "$ref": "#/components/schemas/findUserOutput"
+                    },
+                    {
+                      "type": "null"
+                    }
+                  ],
+                  "title": "Response Finduser"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": false
+        }
+      }
+    },
+    "/mizan/rename_user": {
+      "post": {
+        "summary": "Merge target \u2014 kernel splices return value into the user context.",
+        "operationId": "renameUser",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/renameUserInput"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "description": "Successful Response",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/renameUserOutput"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "Validation Error",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/HTTPValidationError"
+                }
+              }
+            }
+          }
+        },
+        "x-mizan": {
+          "transport": "http",
+          "isContext": false
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "HTTPValidationError": {
+        "properties": {
+          "detail": {
+            "items": {
+              "$ref": "#/components/schemas/ValidationError"
+            },
+            "type": "array",
+            "title": "Detail"
+          }
+        },
+        "type": "object",
+        "title": "HTTPValidationError"
+      },
+      "OrderOutput": {
+        "properties": {
+          "id": {
+            "type": "integer",
+            "title": "Id"
+          },
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          },
+          "total": {
+            "type": "integer",
+            "title": "Total"
+          }
+        },
+        "type": "object",
+        "required": [
+          "id",
+          "user_id",
+          "total"
+        ],
+        "title": "OrderOutput"
+      },
+      "ValidationError": {
+        "properties": {
+          "loc": {
+            "items": {
+              "anyOf": [
+                {
+                  "type": "string"
+                },
+                {
+                  "type": "integer"
+                }
+              ]
+            },
+            "type": "array",
+            "title": "Location"
+          },
+          "msg": {
+            "type": "string",
+            "title": "Message"
+          },
+          "type": {
+            "type": "string",
+            "title": "Error Type"
+          },
+          "input": {
+            "title": "Input"
+          },
+          "ctx": {
+            "type": "object",
+            "title": "Context"
+          }
+        },
+        "type": "object",
+        "required": [
+          "loc",
+          "msg",
+          "type"
+        ],
+        "title": "ValidationError"
+      },
+      "echoInput": {
+        "properties": {
+          "text": {
+            "type": "string",
+            "title": "Text"
+          }
+        },
+        "type": "object",
+        "required": [
+          "text"
+        ],
+        "title": "echoInput"
+      },
+      "echoOutput": {
+        "properties": {
+          "message": {
+            "type": "string",
+            "title": "Message"
+          }
+        },
+        "type": "object",
+        "required": [
+          "message"
+        ],
+        "title": "echoOutput"
+      },
+      "findUserInput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id"
+        ],
+        "title": "findUserInput"
+      },
+      "findUserOutput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          },
+          "name": {
+            "type": "string",
+            "title": "Name"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id",
+          "name"
+        ],
+        "title": "findUserOutput"
+      },
+      "renameUserInput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          },
+          "name": {
+            "type": "string",
+            "title": "Name"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id",
+          "name"
+        ],
+        "title": "renameUserInput"
+      },
+      "renameUserOutput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          },
+          "name": {
+            "type": "string",
+            "title": "Name"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id",
+          "name"
+        ],
+        "title": "renameUserOutput"
+      },
+      "updateProfileInput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          },
+          "name": {
+            "type": "string",
+            "title": "Name"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id",
+          "name"
+        ],
+        "title": "updateProfileInput"
+      },
+      "updateProfileOutput": {
+        "properties": {
+          "ok": {
+            "type": "boolean",
+            "title": "Ok"
+          }
+        },
+        "type": "object",
+        "required": [
+          "ok"
+        ],
+        "title": "updateProfileOutput"
+      },
+      "userOrdersInput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id"
+        ],
+        "title": "userOrdersInput"
+      },
+      "userOrdersOutput": {
+        "items": {
+          "$ref": "#/components/schemas/OrderOutput"
+        },
+        "type": "array",
+        "title": "userOrdersOutput"
+      },
+      "userProfileInput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id"
+        ],
+        "title": "userProfileInput"
+      },
+      "userProfileOutput": {
+        "properties": {
+          "user_id": {
+            "type": "integer",
+            "title": "User Id"
+          },
+          "name": {
+            "type": "string",
+            "title": "Name"
+          }
+        },
+        "type": "object",
+        "required": [
+          "user_id",
+          "name"
+        ],
+        "title": "userProfileOutput"
+      },
+      "whoamiOutput": {
+        "properties": {
+          "email": {
+            "type": "string",
+            "title": "Email"
+          },
+          "authenticated": {
+            "type": "boolean",
+            "title": "Authenticated"
+          }
+        },
+        "type": "object",
+        "required": [
+          "email",
+          "authenticated"
+        ],
+        "title": "whoamiOutput"
+      }
+    }
+  },
+  "x-mizan-functions": [
+    {
+      "name": "echo",
+      "camelName": "echo",
+      "hasInput": true,
+      "inputType": "echoInput",
+      "outputType": "echoOutput",
+      "outputNullable": false,
+      "transport": "http",
+      "isContext": false,
+      "isForm": false,
+      "formName": null,
+      "formRole": null
+    },
+    {
+      "name": "whoami",
+      "camelName": "whoami",
+      "hasInput": false,
+      "inputType": null,
+      "outputType": "whoamiOutput",
+      "outputNullable": false,
+      "transport": "http",
+      "isContext": false,
+      "isForm": false,
+      "formName": null,
+      "formRole": null
+    },
+    {
+      "name": "user_profile",
+      "camelName": "userProfile",
+      "hasInput": true,
+      "inputType": "userProfileInput",
+      "outputType": "userProfileOutput",
+      "outputNullable": false,
+      "transport": "http",
+      "isContext": "user",
+      "isForm": false,
+      "formName": null,
+      "formRole": null
+    },
+    {
+      "name": "user_orders",
+      "camelName": "userOrders",
+      "hasInput": true,
+      "inputType": "userOrdersInput",
+      "outputType": "userOrdersOutput",
+      "outputNullable": false,
+      "transport": "http",
+      "isContext": "user",
+      "isForm": false,
+      "formName": null,
+      "formRole": null
+    },
+    {
+      "name": "update_profile",
+      "camelName": "updateProfile",
+      "hasInput": true,
+      "inputType": "updateProfileInput",
+      "outputType": "updateProfileOutput",
+      "outputNullable": false,
+      "transport": "http",
+      "isContext": false,
+      "isForm": false,
+      "formName": null,
+      "formRole": null,
+      "affects": [
+        {
+          "type": "context",
+          "name": "user"
+        }
+      ]
+    },
+    {
+      "name": "find_user",
+      "camelName": "findUser",
+      "hasInput": true,
+      "inputType": "findUserInput",
+      "outputType": "findUserOutput",
+      "outputNullable": true,
+      "transport": "http",
+      "isContext": false,
+      "isForm": false,
+      "formName": null,
+      "formRole": null
+    },
+    {
+      "name": "rename_user",
+      "camelName": "renameUser",
+      "hasInput": true,
+      "inputType": "renameUserInput",
+      "outputType": "renameUserOutput",
+      "outputNullable": false,
+      "transport": "http",
+      "isContext": false,
+      "isForm": false,
+      "formName": null,
+      "formRole": null,
+      "merge": [
+        "user"
+      ]
+    }
+  ],
+  "x-mizan-contexts": {
+    "user": {
+      "functions": [
+        "user_profile",
+        "user_orders"
+      ],
+      "params": {
+        "user_id": {
+          "type": "integer",
+          "sharedBy": [
+            "user_profile",
+            "user_orders"
+          ],
+          "required": true
+        }
+      }
+    }
+  }
+}
--- a/protocol/mizan-codegen/tests/fixtures/channels_schema.json
+++ b/protocol/mizan-codegen/tests/fixtures/channels_schema.json
@@ -0,0 +1,55 @@
+{
+  "x-mizan-channels": [
+    {
+      "name": "chat",
+      "pascalName": "Chat",
+      "hasParams": true,
+      "hasReactMessage": true,
+      "hasDjangoMessage": true,
+      "paramsType": "ChatChannelParams",
+      "reactMessageType": "ChatReactMessage",
+      "djangoMessageType": "ChatDjangoMessage"
+    },
+    {
+      "name": "notifications",
+      "pascalName": "Notifications",
+      "hasParams": false,
+      "hasReactMessage": false,
+      "hasDjangoMessage": true,
+      "djangoMessageType": "NotificationsDjangoMessage"
+    }
+  ],
+  "components": {
+    "schemas": {
+      "ChatChannelParams": {
+        "type": "object",
+        "properties": {
+          "room_id": { "type": "string" }
+        },
+        "required": ["room_id"]
+      },
+      "ChatReactMessage": {
+        "type": "object",
+        "properties": {
+          "text": { "type": "string" }
+        },
+        "required": ["text"]
+      },
+      "ChatDjangoMessage": {
+        "type": "object",
+        "properties": {
+          "text": { "type": "string" },
+          "from_user": { "type": "string" }
+        },
+        "required": ["text", "from_user"]
+      },
+      "NotificationsDjangoMessage": {
+        "type": "object",
+        "properties": {
+          "body": { "type": "string" }
+        },
+        "required": ["body"]
+      }
+    }
+  }
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_python/init.py
+++ b/protocol/mizan-codegen/tests/fixtures/js_python/init.py
@@ -0,0 +1,4 @@
+# AUTO-GENERATED by mizan — do not edit
+
+from .client import MizanClient  # noqa: F401
+from .types import *  # noqa: F401, F403
--- a/protocol/mizan-codegen/tests/fixtures/js_python/client.py
+++ b/protocol/mizan-codegen/tests/fixtures/js_python/client.py
@@ -0,0 +1,67 @@
+# AUTO-GENERATED by mizan — do not edit
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import Any
+
+# Built from frontends/mizan-rust with `maturin develop --features pyo3`.
+from mizan_rust import PyMizanClient, PyContextSubscription
+
+from .types import *  # noqa: F401, F403
+from .types import BaseModel  # re-import for the synthesized ContextData classes
+
+
+class MizanClient:
+    """Typed Python facade over the PyO3 mizan-rust kernel."""
+
+    def __init__(self, base_url: str, *, session: bool = False,
+                 csrf_cookie_name: str = "csrftoken",
+                 csrf_header_name: str = "X-CSRFToken") -> None:
+        self._inner = PyMizanClient(
+            base_url,
+            session=session,
+            csrf_cookie_name=csrf_cookie_name,
+            csrf_header_name=csrf_header_name,
+        )
+
+    def fetch_user_context(self, user_id: int) -> "UserContextData":
+        raw = self._inner.fetch_context("user", {"user_id": user_id})
+        return UserContextData(**raw)
+    def subscribe_user_context(self, user_id: int,
+                                       callback: Callable[[dict[str, Any]], None]) -> PyContextSubscription:
+        return self._inner.subscribe_context("user", {"user_id": user_id}, callback)
+
+    def call_echo(self, args: EchoInput) -> EchoOutput:
+        raw = self._inner.call("echo", args.model_dump())
+        return EchoOutput(**raw)
+
+    def call_whoami(self) -> WhoamiOutput:
+        raw = self._inner.call("whoami", {})
+        return WhoamiOutput(**raw)
+
+    def call_update_profile(self, args: UpdateProfileInput) -> UpdateProfileOutput:
+        raw = self._inner.call("update_profile", args.model_dump())
+        return UpdateProfileOutput(**raw)
+
+    def call_find_user(self, args: FindUserInput) -> FindUserOutput | None:
+        raw = self._inner.call("find_user", args.model_dump())
+        return FindUserOutput(**raw) if raw is not None else None
+
+    def call_rename_user(self, args: RenameUserInput) -> RenameUserOutput:
+        raw = self._inner.call("rename_user", args.model_dump())
+        return RenameUserOutput(**raw)
+
+    def invalidate(self, context: str) -> None:
+        self._inner.invalidate(context)
+
+    def invalidate_scoped(self, context: str, params: dict[str, Any]) -> None:
+        self._inner.invalidate_scoped(context, params)
+
+
+# ── Context data shapes (per-context bundle) ──────────────────────────────
+
+class UserContextData(BaseModel):
+    """Bundled return of fetch_user_context."""
+    user_profile: UserProfileOutput
+    user_orders: UserOrdersOutput
--- a/protocol/mizan-codegen/tests/fixtures/js_python/types.py
+++ b/protocol/mizan-codegen/tests/fixtures/js_python/types.py
@@ -0,0 +1,66 @@
+# AUTO-GENERATED by mizan — do not edit
+
+from __future__ import annotations
+
+from typing import Any, Literal
+
+from pydantic import BaseModel
+
+class HTTPValidationError(BaseModel):
+    detail: list[ValidationError] | None = None
+
+class OrderOutput(BaseModel):
+    id: int
+    user_id: int
+    total: int
+
+class ValidationError(BaseModel):
+    loc: list[Any]
+    msg: str
+    r#type: str
+    input: Any | None = None
+    ctx: dict[str, Any] | None = None
+
+class EchoInput(BaseModel):
+    text: str
+
+class EchoOutput(BaseModel):
+    message: str
+
+class FindUserInput(BaseModel):
+    user_id: int
+
+class FindUserOutput(BaseModel):
+    user_id: int
+    name: str
+
+class RenameUserInput(BaseModel):
+    user_id: int
+    name: str
+
+class RenameUserOutput(BaseModel):
+    user_id: int
+    name: str
+
+class UpdateProfileInput(BaseModel):
+    user_id: int
+    name: str
+
+class UpdateProfileOutput(BaseModel):
+    ok: bool
+
+class UserOrdersInput(BaseModel):
+    user_id: int
+
+UserOrdersOutput = list[OrderOutput]
+
+class UserProfileInput(BaseModel):
+    user_id: int
+
+class UserProfileOutput(BaseModel):
+    user_id: int
+    name: str
+
+class WhoamiOutput(BaseModel):
+    email: str
+    authenticated: bool
--- a/protocol/mizan-codegen/tests/fixtures/js_react/react.tsx
+++ b/protocol/mizan-codegen/tests/fixtures/js_react/react.tsx
@@ -0,0 +1,157 @@
+'use client'
+
+// AUTO-GENERATED by mizan — do not edit
+
+import {
+    createContext,
+    useCallback,
+    useContext,
+    useEffect,
+    useRef,
+    useState,
+    useSyncExternalStore,
+    type ReactNode,
+} from 'react'
+import {
+    configure,
+    initSession,
+    mizanCall,
+    mizanFetch,
+    MizanError,
+    registerContext,
+    type ContextState,
+} from '@mizan/base'
+
+import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callWhoami, callFindUser, callRenameUser, type userProfileOutput, type userOrdersOutput } from './index'
+
+// Internal — runs inside a Provider, registers with the kernel exactly once.
+function useContextSubscription<T>(
+    name: string,
+    params: Record<string, any>,
+    fetchFn: () => Promise<T>,
+    initialData?: T,
+): ContextState<T> {
+    const ref = useRef<ReturnType<typeof registerContext> | null>(null)
+    if (!ref.current) {
+        ref.current = registerContext(name, params, fetchFn, initialData)
+    }
+    const handle = ref.current
+
+    useEffect(() => {
+        if (handle.getState().status === 'idle') handle.refetch()
+        return () => handle.unregister()
+    }, [handle])
+
+    return useSyncExternalStore(handle.subscribe, handle.getState, handle.getState)
+}
+
+// Internal — wraps an imperative call() with isPending / error state.
+interface MutationHook<TArgs, TResult> {
+    mutate: (args: TArgs) => Promise<TResult>
+    isPending: boolean
+    error: Error | null
+}
+
+function useMutation<TArgs, TResult>(
+    callFn: (args: TArgs) => Promise<TResult>,
+): MutationHook<TArgs, TResult> {
+    const [isPending, setIsPending] = useState(false)
+    const [error, setError] = useState<Error | null>(null)
+
+    const mutate = useCallback(async (args: TArgs) => {
+        setIsPending(true)
+        setError(null)
+        try {
+            return await callFn(args)
+        } catch (e) {
+            setError(e as Error)
+            throw e
+        } finally {
+            setIsPending(false)
+        }
+    }, [callFn])
+
+    return { mutate, isPending, error }
+}
+
+// ── User Context ──
+
+const UserCtx = createContext<ContextState<UserContextData> | null>(null)
+
+export function UserContext({ children, ...params }: UserContextParams & { children: ReactNode }) {
+    const state = useContextSubscription('user', params, () => fetchUserContext(params))
+    return <UserCtx.Provider value={state}>{children}</UserCtx.Provider>
+}
+
+export function useUserContext(): ContextState<UserContextData> {
+    const ctx = useContext(UserCtx)
+    if (!ctx) throw new Error('useUserContext requires <UserContext>')
+    return ctx
+}
+
+export function useUserProfile(): userProfileOutput | null {
+    return useUserContext().data?.user_profile ?? null
+}
+
+export function useUserOrders(): userOrdersOutput | null {
+    return useUserContext().data?.user_orders ?? null
+}
+
+export function useUpdateProfile() {
+    return useMutation<Parameters<typeof callUpdateProfile>[0], Awaited<ReturnType<typeof callUpdateProfile>>>(callUpdateProfile)
+}
+
+export function useEcho() {
+    return useMutation<Parameters<typeof callEcho>[0], Awaited<ReturnType<typeof callEcho>>>(callEcho)
+}
+
+export function useWhoami() {
+    return useMutation<void, Awaited<ReturnType<typeof callWhoami>>>(() => callWhoami() as any)
+}
+
+export function useFindUser() {
+    return useMutation<Parameters<typeof callFindUser>[0], Awaited<ReturnType<typeof callFindUser>>>(callFindUser)
+}
+
+export function useRenameUser() {
+    return useMutation<Parameters<typeof callRenameUser>[0], Awaited<ReturnType<typeof callRenameUser>>>(callRenameUser)
+}
+
+// ── MizanContext root provider ──
+
+export interface MizanContextProps {
+    /** Base URL for protocol endpoints. Defaults to "/api/mizan". */
+    baseUrl?: string
+    /** Set to `false` for backends without a `/session/` endpoint (e.g. FastAPI). */
+    session?: boolean
+    children: ReactNode
+}
+
+/**
+ * Root provider — calls configure() once and mounts the global context (if defined).
+ * Must wrap any component using Mizan-generated hooks.
+ */
+export function MizanContext({ baseUrl, session, children }: MizanContextProps) {
+    const configured = useRef(false)
+    if (!configured.current) {
+        const opts: Parameters<typeof configure>[0] = {}
+        if (baseUrl !== undefined) opts.baseUrl = baseUrl
+        if (session !== undefined) opts.session = session
+        if (Object.keys(opts).length > 0) configure(opts)
+        configured.current = true
+    }
+    return <>{children}</>
+}
+
+// ── Imperative escape hatch ──
+
+/**
+ * Returns the imperative kernel API. For test harnesses or rare cases where
+ * a typed generated hook does not fit. Most app code should use the typed hooks.
+ */
+export function useMizan() {
+    return { call: mizanCall, fetch: mizanFetch }
+}
+
+export type { ContextState } from '@mizan/base'
+export { configure, initSession, MizanError } from '@mizan/base'
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/Cargo.toml
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "fixture_client"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+mizan-rust = { path = "../../../frontends/mizan-rust" }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tokio = { version = "1", features = ["rt", "macros"] }
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/contexts/mod.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/contexts/mod.rs
@@ -0,0 +1,3 @@
+// AUTO-GENERATED by mizan — do not edit
+
+pub mod user;
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/contexts/user.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/contexts/user.rs
@@ -0,0 +1,29 @@
+// AUTO-GENERATED by mizan — do not edit
+
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+use mizan_rust::{MizanClient, MizanError};
+
+use crate::types::{UserProfileOutput, UserOrdersOutput};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UserContextData {
+    pub user_profile: UserProfileOutput,
+    pub user_orders: UserOrdersOutput,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UserContextParams {
+    pub user_id: i64,
+}
+
+pub async fn fetch_user_context(
+    client: &MizanClient,
+    params: &UserContextParams,
+) -> Result<UserContextData, MizanError> {
+    let params_value = serde_json::to_value(params).unwrap_or(Value::Object(Default::default()));
+    let raw = client.fetch_context("user", &params_value).await?;
+    serde_json::from_value(raw)
+        .map_err(|e| MizanError::transport(format!("decode user context: {e}")))
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/echo.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/echo.rs
@@ -0,0 +1,14 @@
+// AUTO-GENERATED by mizan — do not edit
+
+use serde_json::Value;
+
+use mizan_rust::{MizanClient, MizanError};
+
+use crate::types::{EchoOutput, EchoInput};
+
+pub async fn call_echo(client: &MizanClient, args: &EchoInput) -> Result<EchoOutput, MizanError> {
+    let args_value = serde_json::to_value(args).unwrap_or(Value::Object(Default::default()));
+    let raw = client.call("echo", args_value).await?;
+    serde_json::from_value(raw)
+        .map_err(|e| MizanError::transport(format!("decode echo result: {e}")))
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/find_user.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/find_user.rs
@@ -0,0 +1,14 @@
+// AUTO-GENERATED by mizan — do not edit
+
+use serde_json::Value;
+
+use mizan_rust::{MizanClient, MizanError};
+
+use crate::types::{FindUserOutput, FindUserInput};
+
+pub async fn call_find_user(client: &MizanClient, args: &FindUserInput) -> Result<Option<FindUserOutput>, MizanError> {
+    let args_value = serde_json::to_value(args).unwrap_or(Value::Object(Default::default()));
+    let raw = client.call("find_user", args_value).await?;
+    serde_json::from_value(raw)
+        .map_err(|e| MizanError::transport(format!("decode find_user result: {e}")))
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/mod.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/mod.rs
@@ -0,0 +1,6 @@
+// AUTO-GENERATED by mizan — do not edit
+
+pub mod echo;
+pub mod find_user;
+pub mod rename_user;
+pub mod whoami;
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/rename_user.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/rename_user.rs
@@ -0,0 +1,14 @@
+// AUTO-GENERATED by mizan — do not edit
+
+use serde_json::Value;
+
+use mizan_rust::{MizanClient, MizanError};
+
+use crate::types::{RenameUserOutput, RenameUserInput};
+
+pub async fn call_rename_user(client: &MizanClient, args: &RenameUserInput) -> Result<RenameUserOutput, MizanError> {
+    let args_value = serde_json::to_value(args).unwrap_or(Value::Object(Default::default()));
+    let raw = client.call("rename_user", args_value).await?;
+    serde_json::from_value(raw)
+        .map_err(|e| MizanError::transport(format!("decode rename_user result: {e}")))
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/whoami.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/functions/whoami.rs
@@ -0,0 +1,14 @@
+// AUTO-GENERATED by mizan — do not edit
+
+use serde_json::Value;
+
+use mizan_rust::{MizanClient, MizanError};
+
+use crate::types::{WhoamiOutput};
+
+pub async fn call_whoami(client: &MizanClient) -> Result<WhoamiOutput, MizanError> {
+    let args_value = Value::Object(Default::default());
+    let raw = client.call("whoami", args_value).await?;
+    serde_json::from_value(raw)
+        .map_err(|e| MizanError::transport(format!("decode whoami result: {e}")))
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/lib.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/lib.rs
@@ -0,0 +1,8 @@
+// AUTO-GENERATED by mizan — do not edit
+
+pub mod types;
+pub mod contexts;
+pub mod mutations;
+pub mod functions;
+
+pub use mizan_rust::{MizanClient, MizanConfig, MizanError};
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/mutations/mod.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/mutations/mod.rs
@@ -0,0 +1,3 @@
+// AUTO-GENERATED by mizan — do not edit
+
+pub mod update_profile;
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/mutations/update_profile.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/mutations/update_profile.rs
@@ -0,0 +1,14 @@
+// AUTO-GENERATED by mizan — do not edit
+
+use serde_json::Value;
+
+use mizan_rust::{MizanClient, MizanError};
+
+use crate::types::{UpdateProfileOutput, UpdateProfileInput};
+
+pub async fn call_update_profile(client: &MizanClient, args: &UpdateProfileInput) -> Result<UpdateProfileOutput, MizanError> {
+    let args_value = serde_json::to_value(args).unwrap_or(Value::Object(Default::default()));
+    let raw = client.call("update_profile", args_value).await?;
+    serde_json::from_value(raw)
+        .map_err(|e| MizanError::transport(format!("decode update_profile result: {e}")))
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_rust/src/types.rs
+++ b/protocol/mizan-codegen/tests/fixtures/js_rust/src/types.rs
@@ -0,0 +1,98 @@
+// AUTO-GENERATED by mizan — do not edit
+
+#![allow(non_camel_case_types)]
+
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct HTTPValidationError {
+    pub detail: Option<Vec<ValidationError>>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OrderOutput {
+    pub id: i64,
+    pub user_id: i64,
+    pub total: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ValidationError {
+    pub loc: Vec<serde_json::Value>,
+    pub msg: String,
+    #[serde(rename = "type")]
+    pub r#type: String,
+    pub input: Option<serde_json::Value>,
+    pub ctx: Option<serde_json::Value>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EchoInput {
+    pub text: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct EchoOutput {
+    pub message: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct FindUserInput {
+    pub user_id: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct FindUserOutput {
+    pub user_id: i64,
+    pub name: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RenameUserInput {
+    pub user_id: i64,
+    pub name: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RenameUserOutput {
+    pub user_id: i64,
+    pub name: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UpdateProfileInput {
+    pub user_id: i64,
+    pub name: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UpdateProfileOutput {
+    pub ok: bool,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UserOrdersInput {
+    pub user_id: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct UserOrdersOutput(pub Vec<OrderOutput>);
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UserProfileInput {
+    pub user_id: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct UserProfileOutput {
+    pub user_id: i64,
+    pub name: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct WhoamiOutput {
+    pub email: String,
+    pub authenticated: bool,
+}
+
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/contexts/user.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/contexts/user.ts
@@ -0,0 +1,18 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanFetch } from '@mizan/base'
+
+import type { userProfileOutput, userOrdersOutput } from '../types'
+
+export interface UserContextData {
+    user_profile: userProfileOutput
+    user_orders: userOrdersOutput
+}
+
+export interface UserContextParams {
+    user_id: number
+}
+
+export function fetchUserContext(params: UserContextParams): Promise<UserContextData> {
+    return mizanFetch('user', params)
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/echo.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/echo.ts
@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { echoInput, echoOutput } from '../types'
+
+export function callEcho(args: echoInput): Promise<echoOutput> {
+    return mizanCall('echo', args)
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/findUser.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/findUser.ts
@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { findUserInput, findUserOutput } from '../types'
+
+export function callFindUser(args: findUserInput): Promise<findUserOutput> {
+    return mizanCall('find_user', args)
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/renameUser.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/renameUser.ts
@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { renameUserInput, renameUserOutput } from '../types'
+
+export function callRenameUser(args: renameUserInput): Promise<renameUserOutput> {
+    return mizanCall('rename_user', args)
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/whoami.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/functions/whoami.ts
@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { whoamiOutput } from '../types'
+
+export function callWhoami(): Promise<whoamiOutput> {
+    return mizanCall('whoami', {})
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/index.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/index.ts
@@ -0,0 +1,11 @@
+// AUTO-GENERATED by mizan — do not edit
+
+export * from './types'
+
+export { fetchUserContext, type UserContextData, type UserContextParams } from './contexts/user'
+
+export { callEcho } from './functions/echo'
+export { callWhoami } from './functions/whoami'
+export { callUpdateProfile } from './mutations/updateProfile'
+export { callFindUser } from './functions/findUser'
+export { callRenameUser } from './functions/renameUser'
--- a/protocol/mizan-codegen/tests/fixtures/js_stage1/mutations/updateProfile.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_stage1/mutations/updateProfile.ts
@@ -0,0 +1,9 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { mizanCall } from '@mizan/base'
+
+import type { updateProfileInput, updateProfileOutput } from '../types'
+
+export function callUpdateProfile(args: updateProfileInput): Promise<updateProfileOutput> {
+    return mizanCall('update_profile', args)
+}
--- a/protocol/mizan-codegen/tests/fixtures/js_svelte/svelte.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_svelte/svelte.ts
@@ -0,0 +1,29 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { readable, type Readable } from 'svelte/store'
+import { registerContext, type ContextState } from '@mizan/base'
+
+import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callWhoami, callFindUser, callRenameUser } from '../index'
+
+export function createUserContext(params: UserContextParams) {
+    const store = readable<ContextState<UserContextData>>(
+        { data: null, status: 'idle', error: null },
+        (set) => {
+            const handle = registerContext('user', params, () => fetchUserContext(params))
+            const unsub = handle.subscribe(() => set(handle.getState()))
+            handle.refetch()
+            return () => { unsub(); handle.unregister() }
+        },
+    )
+
+    return store
+}
+
+export { callUpdateProfile } from '../index'
+export { callEcho } from '../index'
+export { callWhoami } from '../index'
+export { callFindUser } from '../index'
+export { callRenameUser } from '../index'
+
+export type { ContextState } from '@mizan/base'
+export { configure, initSession, MizanError } from '@mizan/base'
--- a/protocol/mizan-codegen/tests/fixtures/js_vue/vue.ts
+++ b/protocol/mizan-codegen/tests/fixtures/js_vue/vue.ts
@@ -0,0 +1,96 @@
+// AUTO-GENERATED by mizan — do not edit
+
+import { ref, computed, onMounted, onUnmounted, onServerPrefetch, type ComputedRef } from 'vue'
+import { registerContext, type ContextState } from '@mizan/base'
+
+import { fetchUserContext, type UserContextData, type UserContextParams, callUpdateProfile, callEcho, callWhoami, callFindUser, callRenameUser } from '../index'
+
+export function useUserContext(params: UserContextParams) {
+    const state = ref<ContextState<UserContextData>>({ data: null, status: 'idle', error: null })
+    let handle: ReturnType<typeof registerContext> | null = null
+
+    onMounted(() => {
+        handle = registerContext('user', params, () => fetchUserContext(params))
+        handle.subscribe(() => { state.value = handle!.getState() })
+        handle.refetch()
+    })
+
+    onServerPrefetch(async () => {
+        handle = registerContext('user', params, () => fetchUserContext(params))
+        await handle.refetch()
+        state.value = handle.getState()
+    })
+
+    onUnmounted(() => { handle?.unregister() })
+
+    return {
+        state,
+        userProfile: computed(() => state.value.data?.user_profile ?? null) as ComputedRef<userProfileOutput | null>,
+        userOrders: computed(() => state.value.data?.user_orders ?? null) as ComputedRef<userOrdersOutput | null>,
+        loading: computed(() => state.value.status === 'loading'),
+        error: computed(() => state.value.error),
+    }
+}
+
+export function useUpdateProfile() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callUpdateProfile>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callUpdateProfile(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useEcho() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callEcho>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callEcho(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useWhoami() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate() {
+        isPending.value = true; error.value = null
+        try { return await callWhoami() }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useFindUser() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callFindUser>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callFindUser(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export function useRenameUser() {
+    const isPending = ref(false)
+    const error = ref<Error | null>(null)
+    async function mutate(args: Parameters<typeof callRenameUser>[0]) {
+        isPending.value = true; error.value = null
+        try { return await callRenameUser(args) }
+        catch (e) { error.value = e as Error; throw e }
+        finally { isPending.value = false }
+    }
+    return { mutate, isPending, error }
+}
+
+export type { ContextState } from '@mizan/base'
+export { configure, initSession, MizanError } from '@mizan/base'
--- a/protocol/mizan-codegen/tests/ir_deserialization.rs
+++ b/protocol/mizan-codegen/tests/ir_deserialization.rs
@@ -0,0 +1,103 @@
+//! IR deserialization tests against the AFI fixture schema.
+//!
+//! The fixture is captured from the FastAPI backend's `build_schema()`
+//! against `tests/afi/fixture.py`. Each test exercises a different facet
+//! of the IR — function set, per-function field decoding, context-param
+//! elevation, and components.schemas presence — to confirm the typed
+//! Rust structs match the JSON shape the backends emit.
+
+use std::path::PathBuf;
+
+use mizan_codegen::fetch::parse_ir_from_str;
+use mizan_codegen::ir::{AffectKind, IsContext, Transport};
+
+
+fn load_fixture() -> mizan_codegen::ir::MizanIR {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/afi_schema.json");
+    let raw = std::fs::read_to_string(&path)
+        .unwrap_or_else(|e| panic!("read {}: {e}", path.display()));
+    parse_ir_from_str(&raw).unwrap_or_else(|e| panic!("parse IR: {e}"))
+}
+
+
+#[test]
+fn afi_fixture_deserializes_function_set() {
+    let ir = load_fixture();
+    let names: Vec<&str> = ir.functions.iter().map(|f| f.name.as_str()).collect();
+
+    // Seven fixture functions per tests/afi/fixture.py.
+    assert_eq!(ir.functions.len(), 7, "expected 7 functions, got {}: {names:?}", ir.functions.len());
+
+    for expected in [
+        "echo", "whoami",
+        "user_profile", "user_orders",
+        "update_profile", "find_user", "rename_user",
+    ] {
+        assert!(names.contains(&expected), "missing function {expected:?} in {names:?}");
+    }
+}
+
+
+#[test]
+fn afi_fixture_function_field_decode() {
+    let ir = load_fixture();
+    let echo = ir.functions.iter().find(|f| f.name == "echo").unwrap();
+    assert_eq!(echo.camel_name, "echo");
+    assert!(echo.has_input);
+    assert_eq!(echo.input_type.as_deref(), Some("echoInput"));
+    assert_eq!(echo.output_type, "echoOutput");
+    assert!(!echo.output_nullable);
+    assert_eq!(echo.transport, Transport::Http);
+    assert_eq!(echo.is_context, IsContext::No);
+
+    let whoami = ir.functions.iter().find(|f| f.name == "whoami").unwrap();
+    assert!(!whoami.has_input);
+
+    // `find_user` returns `ProfileOutput | None` — outputNullable must be true.
+    let find_user = ir.functions.iter().find(|f| f.name == "find_user").unwrap();
+    assert!(find_user.output_nullable, "find_user must be outputNullable");
+
+    // Context-typed function picks up the context name.
+    let user_profile = ir.functions.iter().find(|f| f.name == "user_profile").unwrap();
+    assert_eq!(user_profile.is_context.as_str(), Some("user"));
+
+    // Mutation with `affects="user"` lands in `affects` as a context target.
+    let update_profile = ir.functions.iter().find(|f| f.name == "update_profile").unwrap();
+    assert_eq!(update_profile.affects.len(), 1);
+    assert_eq!(update_profile.affects[0].kind, AffectKind::Context);
+    assert_eq!(update_profile.affects[0].name, "user");
+}
+
+
+#[test]
+fn afi_fixture_context_param_elevation() {
+    let ir = load_fixture();
+    let user = ir.contexts.get("user").expect("user context group");
+
+    // Both context functions share `user_id` as a required param.
+    let user_id = user.params.get("user_id").expect("user_id param");
+    assert_eq!(user_id.ty, "integer");
+    assert!(user_id.required, "user_id is required (declared by every fn in the group)");
+    assert!(user_id.shared_by.contains(&"user_profile".to_string()));
+    assert!(user_id.shared_by.contains(&"user_orders".to_string()));
+}
+
+
+#[test]
+fn afi_fixture_components_schemas_present() {
+    let ir = load_fixture();
+    // Each fixture function pairs with an *Input/Output schema in components.
+    for expected in [
+        "echoInput", "echoOutput",
+        "whoamiOutput",
+        "userProfileInput", "userProfileOutput",
+        "updateProfileInput", "updateProfileOutput",
+        "findUserInput", "findUserOutput",
+    ] {
+        assert!(
+            ir.components.schemas.contains_key(expected),
+            "missing schema {expected:?}",
+        );
+    }
+}
--- a/protocol/mizan-codegen/tests/python_parity.rs
+++ b/protocol/mizan-codegen/tests/python_parity.rs
@@ -0,0 +1,75 @@
+//! Byte-equivalence test for the Python target against the JS baseline.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use mizan_codegen::config::{Config, SourceConfig};
+use mizan_codegen::emit::{CodegenTarget, EmittedFile};
+use mizan_codegen::emit::python::PythonClient;
+use mizan_codegen::fetch::parse_ir_from_str;
+
+
+fn load_ir() -> mizan_codegen::ir::MizanIR {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/afi_schema.json");
+    parse_ir_from_str(&std::fs::read_to_string(&path).unwrap()).unwrap()
+}
+
+
+fn fixture_config() -> Config {
+    Config {
+        project_id: None,
+        output: PathBuf::from("/tmp"),
+        targets: vec!["python".to_string()],
+        source: SourceConfig { fastapi: None, django: None },
+        rust_kernel: None,
+        rust_crate_name: None,
+    }
+}
+
+
+fn read_baseline(rel: &str) -> String {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/js_python")
+        .join(rel);
+    std::fs::read_to_string(&path)
+        .unwrap_or_else(|e| panic!("read baseline {}: {e}", path.display()))
+}
+
+
+fn emit_index(files: &[EmittedFile]) -> BTreeMap<PathBuf, &str> {
+    files.iter().map(|f| (f.rel_path.clone(), f.content.as_str())).collect()
+}
+
+
+fn assert_byte_equal(rel: &str, files: &BTreeMap<PathBuf, &str>) {
+    let actual = files
+        .get(&PathBuf::from(rel))
+        .unwrap_or_else(|| panic!("Python target did not produce {rel}"));
+    let expected = read_baseline(rel);
+    if *actual != expected {
+        for (lineno, (a, b)) in actual.lines().zip(expected.lines()).enumerate() {
+            if a != b {
+                panic!(
+                    "{rel} diverges at line {}:\n  expected: {b:?}\n  actual:   {a:?}",
+                    lineno + 1,
+                );
+            }
+        }
+        panic!(
+            "{rel} diverges in length: actual={} expected={}",
+            actual.len(), expected.len(),
+        );
+    }
+}
+
+
+#[test]
+fn python_target_all_files_match_baseline() {
+    let ir = load_ir();
+    let files = PythonClient.emit(&ir, &fixture_config());
+    let index = emit_index(&files);
+
+    for rel in ["types.py", "client.py", "__init__.py"] {
+        assert_byte_equal(rel, &index);
+    }
+}
--- a/protocol/mizan-codegen/tests/react_parity.rs
+++ b/protocol/mizan-codegen/tests/react_parity.rs
@@ -0,0 +1,54 @@
+//! Byte-equivalence test for the React target against the JS baseline.
+
+use std::path::PathBuf;
+
+use mizan_codegen::config::{Config, SourceConfig};
+use mizan_codegen::emit::CodegenTarget;
+use mizan_codegen::emit::react::ReactAdapter;
+use mizan_codegen::fetch::parse_ir_from_str;
+
+
+fn load_ir() -> mizan_codegen::ir::MizanIR {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/afi_schema.json");
+    parse_ir_from_str(&std::fs::read_to_string(&path).unwrap()).unwrap()
+}
+
+
+fn fixture_config() -> Config {
+    Config {
+        project_id: None,
+        output: PathBuf::from("/tmp"),
+        targets: vec!["react".to_string()],
+        source: SourceConfig { fastapi: None, django: None },
+        rust_kernel: None,
+        rust_crate_name: None,
+    }
+}
+
+
+#[test]
+fn react_target_byte_match() {
+    let ir = load_ir();
+    let files = ReactAdapter.emit(&ir, &fixture_config());
+    assert_eq!(files.len(), 1);
+    let actual = &files[0].content;
+
+    let expected_path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/js_react/react.tsx");
+    let expected = std::fs::read_to_string(&expected_path).unwrap();
+
+    if *actual != expected {
+        for (lineno, (a, b)) in actual.lines().zip(expected.lines()).enumerate() {
+            if a != b {
+                panic!(
+                    "react.tsx diverges at line {}:\n  expected: {b:?}\n  actual:   {a:?}",
+                    lineno + 1,
+                );
+            }
+        }
+        panic!(
+            "react.tsx diverges in length: actual={} expected={}",
+            actual.len(), expected.len(),
+        );
+    }
+}
--- a/protocol/mizan-codegen/tests/rust_parity.rs
+++ b/protocol/mizan-codegen/tests/rust_parity.rs
@@ -0,0 +1,96 @@
+//! Byte-equivalence between the Rust target and the JS rust.mjs baseline
+//! against the AFI fixture. The downstream forcing function is the wire-
+//! parity drivers under `tests/rust/`; this test catches divergence
+//! earlier in the cycle without needing to spin a FastAPI fixture up.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use mizan_codegen::config::{Config, RustKernelSpec, SourceConfig};
+use mizan_codegen::emit::{CodegenTarget, EmittedFile};
+use mizan_codegen::emit::rust::RustCrate;
+use mizan_codegen::fetch::parse_ir_from_str;
+
+
+fn load_ir() -> mizan_codegen::ir::MizanIR {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/afi_schema.json");
+    parse_ir_from_str(&std::fs::read_to_string(&path).unwrap()).unwrap()
+}
+
+
+fn fixture_config() -> Config {
+    Config {
+        project_id: None,
+        output: PathBuf::from("/tmp"),
+        targets: vec!["rust".to_string()],
+        source: SourceConfig { fastapi: None, django: None },
+        rust_kernel: Some(RustKernelSpec::Path {
+            path: "../../../frontends/mizan-rust".to_string(),
+        }),
+        rust_crate_name: Some("fixture_client".to_string()),
+    }
+}
+
+
+fn read_baseline(rel: &str) -> String {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/js_rust")
+        .join(rel);
+    std::fs::read_to_string(&path)
+        .unwrap_or_else(|e| panic!("read baseline {}: {e}", path.display()))
+}
+
+
+fn emit_index(files: &[EmittedFile]) -> BTreeMap<PathBuf, &str> {
+    files.iter().map(|f| (f.rel_path.clone(), f.content.as_str())).collect()
+}
+
+
+fn assert_byte_equal(rel: &str, files: &BTreeMap<PathBuf, &str>) {
+    let actual = files
+        .get(&PathBuf::from(rel))
+        .unwrap_or_else(|| panic!("Rust target did not produce {rel}"));
+    let expected = read_baseline(rel);
+    if *actual != expected {
+        for (lineno, (a, b)) in actual.lines().zip(expected.lines()).enumerate() {
+            if a != b {
+                panic!(
+                    "{rel} diverges at line {}:\n  expected: {b:?}\n  actual:   {a:?}",
+                    lineno + 1,
+                );
+            }
+        }
+        panic!(
+            "{rel} diverges in length: actual={} expected={}\n--- actual (last 200) ---\n{}\n--- expected (last 200) ---\n{}",
+            actual.len(), expected.len(),
+            &actual[actual.len().saturating_sub(200)..],
+            &expected[expected.len().saturating_sub(200)..],
+        );
+    }
+}
+
+
+#[test]
+fn rust_target_all_files_match_baseline() {
+    let ir = load_ir();
+    let files = RustCrate.emit(&ir, &fixture_config());
+    let index = emit_index(&files);
+
+    for rel in [
+        "Cargo.toml",
+        "src/lib.rs",
+        "src/types.rs",
+        "src/contexts/user.rs",
+        "src/contexts/mod.rs",
+        "src/functions/echo.rs",
+        "src/functions/whoami.rs",
+        "src/functions/find_user.rs",
+        "src/functions/rename_user.rs",
+        "src/functions/mod.rs",
+        "src/mutations/update_profile.rs",
+        "src/mutations/mod.rs",
+    ] {
+        assert_byte_equal(rel, &index);
+    }
+}
--- a/protocol/mizan-codegen/tests/stage1_parity.rs
+++ b/protocol/mizan-codegen/tests/stage1_parity.rs
@@ -0,0 +1,143 @@
+//! Byte-equivalence tests for the deterministic Stage 1 files (contexts,
+//! mutations, functions, index). Baseline output captured from the JS
+//! codegen at `protocol/mizan-generate/generator/lib/stage1.mjs` against
+//! the AFI fixture schema (`tests/fixtures/afi_schema.json`).
+//!
+//! `types.ts` is NOT byte-checked here — the JS codegen routes type
+//! emission through openapi-typescript while the Rust substrate emits
+//! Pydantic schemas directly. Equivalence for types.ts is structural
+//! (named exports present and importable), checked in a separate test.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use mizan_codegen::config::{Config, SourceConfig};
+use mizan_codegen::emit::{CodegenTarget, EmittedFile};
+use mizan_codegen::emit::stage1::Stage1;
+use mizan_codegen::fetch::parse_ir_from_str;
+
+
+fn load_ir() -> mizan_codegen::ir::MizanIR {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/afi_schema.json");
+    let raw = std::fs::read_to_string(&path).unwrap();
+    parse_ir_from_str(&raw).unwrap()
+}
+
+
+fn synthetic_config() -> Config {
+    Config {
+        project_id: None,
+        output: PathBuf::from("/tmp"),
+        targets: vec!["stage1".to_string()],
+        source: SourceConfig { fastapi: None, django: None },
+        rust_kernel: None,
+        rust_crate_name: None,
+    }
+}
+
+
+fn emit_index(files: &[EmittedFile]) -> BTreeMap<PathBuf, &str> {
+    files.iter().map(|f| (f.rel_path.clone(), f.content.as_str())).collect()
+}
+
+
+fn read_baseline(rel: &str) -> String {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests/fixtures/js_stage1")
+        .join(rel);
+    std::fs::read_to_string(&path)
+        .unwrap_or_else(|e| panic!("read baseline {}: {e}", path.display()))
+}
+
+
+fn assert_byte_equal(rel: &str, files: &BTreeMap<PathBuf, &str>) {
+    let actual = files
+        .get(&PathBuf::from(rel))
+        .unwrap_or_else(|| panic!("emitter did not produce {rel}"));
+    let expected = read_baseline(rel);
+    if *actual != expected {
+        // Surface a diff-friendly failure message — first divergent line wins.
+        for (lineno, (a, b)) in actual.lines().zip(expected.lines()).enumerate() {
+            if a != b {
+                panic!(
+                    "{rel} diverges at line {}:\n  expected: {b:?}\n  actual:   {a:?}",
+                    lineno + 1,
+                );
+            }
+        }
+        panic!(
+            "{rel} diverges in length: actual={} expected={}",
+            actual.len(), expected.len(),
+        );
+    }
+}
+
+
+#[test]
+fn stage1_contexts_user_byte_match() {
+    let ir = load_ir();
+    let files = Stage1.emit(&ir, &synthetic_config());
+    let index = emit_index(&files);
+    assert_byte_equal("contexts/user.ts", &index);
+}
+
+
+#[test]
+fn stage1_function_files_byte_match() {
+    let ir = load_ir();
+    let files = Stage1.emit(&ir, &synthetic_config());
+    let index = emit_index(&files);
+    for rel in ["functions/echo.ts", "functions/whoami.ts",
+                "functions/findUser.ts", "functions/renameUser.ts"] {
+        assert_byte_equal(rel, &index);
+    }
+}
+
+
+#[test]
+fn stage1_mutation_files_byte_match() {
+    let ir = load_ir();
+    let files = Stage1.emit(&ir, &synthetic_config());
+    let index = emit_index(&files);
+    assert_byte_equal("mutations/updateProfile.ts", &index);
+}
+
+
+#[test]
+fn stage1_index_byte_match() {
+    let ir = load_ir();
+    let files = Stage1.emit(&ir, &synthetic_config());
+    let index = emit_index(&files);
+    assert_byte_equal("index.ts", &index);
+}
+
+
+#[test]
+fn stage1_types_exports_expected_names() {
+    let ir = load_ir();
+    let files = Stage1.emit(&ir, &synthetic_config());
+    let index = emit_index(&files);
+    let types = index
+        .get(&PathBuf::from("types.ts"))
+        .expect("types.ts must be emitted");
+
+    // Every Pydantic schema named in the IR must surface as a top-level
+    // exported type or interface so Stage 2 adapters can import by name.
+    for expected in [
+        "echoInput", "echoOutput",
+        "whoamiOutput",
+        "userProfileInput", "userProfileOutput",
+        "userOrdersInput",
+        "updateProfileInput", "updateProfileOutput",
+        "findUserInput", "findUserOutput",
+        "renameUserInput", "renameUserOutput",
+    ] {
+        let needle_interface = format!("export interface {expected} ");
+        let needle_type = format!("export type {expected} =");
+        assert!(
+            types.contains(&needle_interface) || types.contains(&needle_type),
+            "types.ts must export {expected:?} (interface or type)",
+        );
+    }
+}
--- a/protocol/mizan-codegen/tests/vue_svelte_parity.rs
+++ b/protocol/mizan-codegen/tests/vue_svelte_parity.rs
@@ -0,0 +1,66 @@
+//! Byte-equivalence tests for Vue + Svelte targets against JS baselines.
+
+use std::path::PathBuf;
+
+use mizan_codegen::config::{Config, SourceConfig};
+use mizan_codegen::emit::CodegenTarget;
+use mizan_codegen::emit::svelte::SvelteAdapter;
+use mizan_codegen::emit::vue::VueAdapter;
+use mizan_codegen::fetch::parse_ir_from_str;
+
+
+fn load_ir() -> mizan_codegen::ir::MizanIR {
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("tests/fixtures/afi_schema.json");
+    parse_ir_from_str(&std::fs::read_to_string(&path).unwrap()).unwrap()
+}
+
+
+fn fixture_config(target: &str) -> Config {
+    Config {
+        project_id: None,
+        output: PathBuf::from("/tmp"),
+        targets: vec![target.to_string()],
+        source: SourceConfig { fastapi: None, django: None },
+        rust_kernel: None,
+        rust_crate_name: None,
+    }
+}
+
+
+fn assert_byte_equal(actual: &str, baseline_path: &str, label: &str) {
+    let baseline = std::fs::read_to_string(
+        PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(baseline_path),
+    ).unwrap();
+    if actual != baseline {
+        for (lineno, (a, b)) in actual.lines().zip(baseline.lines()).enumerate() {
+            if a != b {
+                panic!(
+                    "{label} diverges at line {}:\n  expected: {b:?}\n  actual:   {a:?}",
+                    lineno + 1,
+                );
+            }
+        }
+        panic!(
+            "{label} diverges in length: actual={} expected={}",
+            actual.len(), baseline.len(),
+        );
+    }
+}
+
+
+#[test]
+fn vue_target_byte_match() {
+    let ir = load_ir();
+    let files = VueAdapter.emit(&ir, &fixture_config("vue"));
+    assert_eq!(files.len(), 1);
+    assert_byte_equal(&files[0].content, "tests/fixtures/js_vue/vue.ts", "vue.ts");
+}
+
+
+#[test]
+fn svelte_target_byte_match() {
+    let ir = load_ir();
+    let files = SvelteAdapter.emit(&ir, &fixture_config("svelte"));
+    assert_eq!(files.len(), 1);
+    assert_byte_equal(&files[0].content, "tests/fixtures/js_svelte/svelte.ts", "svelte.ts");
+}