G1: Goose AMW proxy + PreToolUse permit hook + fallback idempotency (SEL-484)

integrations/goose-agent-middleware/LICENSE

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integrations/goose-agent-middleware/README.md

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+# Goose + Agent Middleware
+
+Runs Agent Middleware (AMW) as a normal Goose **StreamableHttp MCP extension**
+that proxies the official `@modelcontextprotocol/server-filesystem` server
+(`read_text_file`, `write_file`), plus a Goose **PreToolUse deny hook**.
+
+Every proxied call goes through permit -> idempotency -> invoke -> receipt.
+
+## Pieces
+
+| Piece | What it does |
+|---|---|
+| `goose-amw-proxy` | StreamableHttp MCP server (protocol 2026-07-28 and older). Verifies the caller, enforces permits, dedupes writes, signs receipts. |
+| `goose-amw-hook` | Goose `PreToolUse` hook. A call with no permit is blocked **before it runs**; Goose shows `Tool call denied by policy hook ...: AMW permit denied: <reason>`. |
+| `plugin/amw-permit/hooks/hooks.json` | Template plugin that wires the hook to `amw__*` tools. |
+
+The proxy enforces the same permit rules server-side, so a client without the
+hook is still refused.
+
+## Permit policy
+
+```json
+{"rules": [
+  {"id": "write-allowed", "tool": "write_file", "folder": "/path/to/allowed"},
+  {"id": "read-sandbox", "tool": "read_text_file", "folder": "/path/to/sandbox"}
+]}
+```
+
+A call is allowed only if a rule names the tool and the resolved `path` is
+inside the rule's folder (`..` and symlinks are resolved first). Anything else
+is denied with a reason.
+
+## Idempotency key
+
+AMW keys a write by **verified caller identity + tool name + canonical
+argument hash + `agent-session-id`**.
+
+Goose (protocol 2026-07-28) sends `_meta["agent-tool-call-request-id"]`, but
+that id is the model's tool-call id: when a call fails and the model retries,
+Goose sends a **new** id (recorded in `tests/fixtures/g1_gate_calls.jsonl`).
+AMW therefore logs it on receipts and in the ledger but never uses it as the
+key. A **write without `agent-session-id`** (for example an older protocol with
+no `_meta`) is refused with a clear reason and a `refuse` receipt, because it
+cannot be deduplicated safely. Reads do not need a session id.
+
+The caller is verified from the `Authorization: Bearer` header against
+`AMW_CALLERS` (a JSON map of `sha256(token)` to caller id). Unverified calls
+are refused.
+
+## Replay window
+
+`AMW_IDEMPOTENCY_WINDOW_SECONDS` (default **600**, must be > 0).
+
+* A completed write repeated with the same key **inside** the window is not
+  run again; AMW returns the stored result and issues a `replayed` receipt.
+* The same write made **after** the window runs normally, so deliberate
+  identical writes later in a session are not swallowed.
+* A write whose outcome is unknown (`failed_unknown`: the call was
+  dispatched and the response was lost, or AMW crashed mid-call) is **never
+  re-run automatically**, inside or outside the window. Retries are refused
+  with a reason until an operator resolves the entry.
+* A definite upstream error (`failed`, no effect) may be retried.
+
+Choose a window longer than your client's retry horizon and shorter than the
+interval at which you write identical content on purpose.
+
+## Receipts
+
+Each decision (allow, deny, replay, refuse) appends an Ed25519-signed receipt
+to `$AMW_STATE_DIR/receipts.jsonl`: `tool`, `args_hash`, `decision`,
+`outcome`, `issued_at`, plus caller, session, key and the logged request id.
+The signature covers the canonical JSON of `body`; the public key is written
+to `receipt_public_key.b64`.
+
+## Goose setup
+
+```yaml
+extensions:
+  amw:
+    type: streamable_http
+    name: amw
+    uri: http://127.0.0.1:8791/mcp
+    headers:
+      Authorization: Bearer ${AMW_TOKEN}
+    timeout: 120
+    enabled: true
+```
+
+Install `plugin/amw-permit` into `.agents/plugins/` (project) or the Goose
+plugins directory, replacing the paths in its `hooks.json`.
+
+## Tests
+
+`pytest` needs no external data. `tests/fixtures/g1_gate_calls.jsonl` is the
+real call log recorded by AMW during the G1 gate session.
+`tests/e2e/fault_proxy.py` is a test-only launcher that injects one fault into
+the shipped proxy to record the cut-stream and unknown-outcome sessions; it
+is not part of the package.

integrations/goose-agent-middleware/plugin/amw-permit/hooks/hooks.json

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+{
+  "hooks": {
+    "PreToolUse": [
+      {
+        "matcher": "^amw__",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "goose-amw-hook --policy /path/to/policy.json --state-dir /path/to/state",
+            "on_failure": "block",
+            "timeout": 10
+          }
+        ]
+      }
+    ]
+  }
+}

integrations/goose-agent-middleware/pyproject.toml

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+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "goose-agent-middleware"
+version = "0.1.0"
+description = "Agent Middleware as a Goose StreamableHttp MCP extension: permits, PreToolUse deny hook, idempotent writes, signed receipts"
+readme = "README.md"
+license = "Apache-2.0"
+requires-python = ">=3.11"
+dependencies = [
+    "amw-sdk>=0.4.0",
+    "mcp>=2.3.0,<3",
+    "cryptography>=50.0.0",
+]
+
+[project.optional-dependencies]
+dev = ["pytest", "ruff"]
+
+[project.scripts]
+goose-amw-proxy = "goose_amw.proxy:main"
+goose-amw-hook = "goose_amw.hook:main"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/goose_amw"]
+
+[tool.ruff]
+line-length = 100
+
+[tool.pytest.ini_options]
+pythonpath = ["src", "../../sdk/python/src"]
+
+[tool.uv.sources]
+amw-sdk = { path = "../../sdk/python", editable = true }

integrations/goose-agent-middleware/src/goose_amw/__init__.py

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+"""Agent Middleware for Goose: a governed StreamableHttp MCP proxy."""
+
+__all__ = ["canonical", "ledger", "permits", "receipts"]

integrations/goose-agent-middleware/src/goose_amw/canonical.py

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+"""Canonical JSON and argument hashing."""
+
+from __future__ import annotations
+
+import hashlib
+from typing import Any
+
+from b2a_sdk.receipt_verifier import canonical_json
+
+
+def sha256_hex(text: str) -> str:
+    return hashlib.sha256(text.encode("utf-8")).hexdigest()
+
+
+def args_hash(arguments: dict[str, Any] | None) -> str:
+    return "sha256:" + sha256_hex(canonical_json(arguments or {}))
+
+
+def idempotency_key(
+    *, caller: str, tool: str, arguments: dict[str, Any] | None, session_id: str
+) -> str:
+    """Fallback key: verified caller + tool + canonical argument hash + agent-session-id.
+
+    ``agent-tool-call-request-id`` is deliberately NOT an input: the G1 gate showed
+    Goose issues a new id when the model retries a failed call.
+    """
+    material = {
+        "caller": caller,
+        "tool": tool,
+        "args_hash": args_hash(arguments),
+        "session_id": session_id,
+    }
+    return "amw-fb-" + sha256_hex(canonical_json(material))
+
+
+__all__ = ["args_hash", "canonical_json", "idempotency_key", "sha256_hex"]