ops(crosscheck): add reproducible Slack app manifest

docs/crosscheck-slack.md

@@ -149,10 +149,27 @@ The listener logs only its nonsecret key ID.
 
 ## Credentials and app permissions
 
-The Slack app must have Socket Mode enabled.
-Its app-level token needs `connections:write`.
-Its bot token needs `app_mentions:read`, `chat:write`, `channels:history`, and `reactions:write`.
-Subscribe the app to `app_mention`, install it to the workspace, and invite it only to approved channels.
+The repository-owned Slack app manifest is in `ops/slack-crosscheck`.
+It enables Socket Mode, subscribes only to `app_mention`, and requests only `app_mentions:read`, `chat:write`, and `reactions:write` for the bot.
+Create or update the app through the official Slack CLI from that directory:
+
+```sh
+cd ops/slack-crosscheck
+$HOME/.slack/bin/slack manifest validate
+$HOME/.slack/bin/slack app install --team <team-id> --environment deployed
+```
+
+The app-level token is created in the app's Basic Information settings with only `connections:write`.
+No Request URL is configured.
+Install the app to the workspace and invite it only to the exact channels in `channel_allowlist`.
+
+Store credentials without putting values in shell history by running each command and entering the value only at the Keychain prompt:
+
+```sh
+security add-generic-password -U -a "$USER" -s firstmate-crosscheck-slack-app -w
+security add-generic-password -U -a "$USER" -s firstmate-crosscheck-slack-bot -w
+security add-generic-password -U -a "$USER" -s firstmate-crosscheck-github-read -w
+```
 
 The GitHub credential must be a read-only GitHub App installation token or fine-grained credential limited to the repositories in `repo_allowlist`.
 It needs pull request metadata and repository contents read access.

ops/slack-crosscheck/.slack/.gitignore

@@ -0,0 +1,4 @@
+/apps.json
+/apps.dev.json
+/cache/
+/config.json

ops/slack-crosscheck/.slack/hooks.json

@@ -0,0 +1,5 @@
+{
+  "hooks": {
+    "get-manifest": "./get-manifest.sh"
+  }
+}

ops/slack-crosscheck/get-manifest.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env sh
+set -eu
+
+SCRIPT_DIR=$(CDPATH='' cd -- "$(dirname -- "$0")" && pwd)
+exec /bin/cat "$SCRIPT_DIR/manifest.json"

ops/slack-crosscheck/manifest.json

@@ -0,0 +1,35 @@
+{
+  "_metadata": {
+    "major_version": 1
+  },
+  "display_information": {
+    "name": "Crosscheck",
+    "description": "Internal exact-head pull request reviews"
+  },
+  "features": {
+    "bot_user": {
+      "display_name": "Crosscheck",
+      "always_online": false
+    }
+  },
+  "oauth_config": {
+    "scopes": {
+      "bot": [
+        "app_mentions:read",
+        "chat:write",
+        "reactions:write"
+      ]
+    }
+  },
+  "settings": {
+    "event_subscriptions": {
+      "bot_events": [
+        "app_mention"
+      ]
+    },
+    "org_deploy_enabled": false,
+    "socket_mode_enabled": true,
+    "is_hosted": false,
+    "token_rotation_enabled": false
+  }
+}

tests/fm-crosscheck-slack.test.sh

@@ -583,6 +583,33 @@ json.dump(value, open(sys.argv[2], "w"))' "$CONFIG_MAIN" "$bad"
   pass "selftest validates config shape and refuses malformed configs by name"
 }
 
+test_slack_app_manifest_is_minimal_and_socket_only() {
+  app_dir="$ROOT/ops/slack-crosscheck"
+  output=$("$app_dir/get-manifest.sh" --source="$app_dir" 2>&1) \
+    || fail "Slack manifest hook failed: $output"
+  APP_MANIFEST_JSON="$output" "$PYTHON" - <<'PYTEST' \
+    || fail "Slack app manifest contract failed"
+import json
+import os
+
+manifest = json.loads(os.environ["APP_MANIFEST_JSON"])
+assert manifest["settings"] == {
+    "event_subscriptions": {"bot_events": ["app_mention"]},
+    "org_deploy_enabled": False,
+    "socket_mode_enabled": True,
+    "is_hosted": False,
+    "token_rotation_enabled": False,
+}
+assert manifest["oauth_config"]["scopes"]["bot"] == [
+    "app_mentions:read",
+    "chat:write",
+    "reactions:write",
+]
+assert "request_url" not in json.dumps(manifest).lower()
+PYTEST
+  pass "Slack app manifest is outbound-only and least-privileged"
+}
+
 test_missing_token_env_refuses_start() {
   output=$(perl -e 'alarm 60; exec @ARGV' -- \
     env -u FM_TEST_SLACK_APP_TOKEN -u FM_TEST_SLACK_BOT_TOKEN -u FM_TEST_GITHUB_READ_TOKEN \
@@ -1389,6 +1416,7 @@ test_tokens_never_reach_logs_or_ledgers() {
 UNITS=(
   test_pr_link_extraction
   test_selftest_validates_config_shape
+  test_slack_app_manifest_is_minimal_and_socket_only
   test_missing_token_env_refuses_start
   test_attestation_cli_derives_and_signs_author_identity
   test_mention_without_link_gets_usage_reply