feat(integrations): provider-agnostic layer — Composio + Merge behind one trait

CLAUDE.md

@@ -76,6 +76,7 @@ Need specific knowledge? Load on demand:
 - Updater, analytics, Sentry, env vars, CI → `knowledge-base/production-infra.md`
 - Supabase auth, Google SSO, Keychain → `knowledge-base/auth.md`
 - Translating UI strings, namespaces, ui/ labels prop pattern, `t()` rules → `knowledge-base/i18n.md`
+- Provider-agnostic integrations layer (Composio + Merge behind one trait) → `knowledge-base/integrations-providers.md`
 
 Design work? Skills: `/critique` before, `/polish` after. Else `/clarify` (copy), `/distill` (overloaded screen), `/animate` (micro-interactions), `/audit` (a11y).
 

Cargo.toml

@@ -14,6 +14,8 @@ members = [
     "engine/houston-agents-conversations",
     "engine/houston-file-watcher",
     "engine/houston-composio",
+    "engine/houston-integrations",
+    "engine/houston-merge",
     "engine/houston-cli-bundle",
     "engine/houston-claude-installer",
     "engine/houston-engine-core",
@@ -46,6 +48,8 @@ houston-ui-events = { version = "0.4.12", path = "engine/houston-ui-events" }
 houston-agents-conversations = { version = "0.4.12", path = "engine/houston-agents-conversations" }
 houston-file-watcher = { version = "0.4.12", path = "engine/houston-file-watcher" }
 houston-composio = { version = "0.4.12", path = "engine/houston-composio" }
+houston-integrations = { version = "0.4.12", path = "engine/houston-integrations" }
+houston-merge = { version = "0.4.12", path = "engine/houston-merge" }
 houston-cli-bundle = { version = "0.4.12", path = "engine/houston-cli-bundle" }
 houston-claude-installer = { version = "0.4.12", path = "engine/houston-claude-installer" }
 houston-engine-core = { version = "0.4.12", path = "engine/houston-engine-core" }

app/src-tauri/src/houston_prompt/mod.rs

@@ -4,24 +4,32 @@
 //! These strings are the product layer. The engine is prompt-agnostic: it
 //! assembles per-agent context from disk, while this module defines how the
 //! Houston desktop agent behaves and speaks.
+//!
+//! Integrations-provider guidance (Composio CLI usage / Merge MCP usage)
+//! no longer lives here — it moved into the engine alongside each provider
+//! crate (`houston_composio::COMPOSIO_GUIDANCE`, `houston_merge::MERGE_GUIDANCE`).
+//! The engine appends the active provider's guidance at session-spawn time so
+//! the agent sees the right instructions for whichever provider the user is
+//! currently using, without restarting the engine on a runtime picker switch.
 
 mod base;
-mod integrations;
 mod onboarding;
 mod routines;
 mod skills_memory;
 
 pub use base::HOUSTON_SYSTEM_PROMPT;
-pub use integrations::COMPOSIO_GUIDANCE;
 pub use onboarding::ONBOARDING_GUIDANCE;
 pub use routines::ROUTINES_GUIDANCE;
 pub use skills_memory::SELF_IMPROVEMENT_GUIDANCE;
 
 /// Build the composite system prompt the engine uses as its fallback.
-/// Order: base identity, skills/memory guidance, routines guidance, Composio guidance.
+/// Order: base identity, skills/memory guidance, routines guidance.
+/// The active integrations provider's operational guidance is appended by
+/// the engine at session-spawn time (see
+/// `houston_engine_server::compose_app_system_prompt`).
 pub fn system_prompt() -> String {
     format!(
-        "{HOUSTON_SYSTEM_PROMPT}\n\n---\n\n{SELF_IMPROVEMENT_GUIDANCE}\n\n---\n\n{ROUTINES_GUIDANCE}{COMPOSIO_GUIDANCE}"
+        "{HOUSTON_SYSTEM_PROMPT}\n\n---\n\n{SELF_IMPROVEMENT_GUIDANCE}\n\n---\n\n{ROUTINES_GUIDANCE}"
     )
 }
 

app/src/components/composio-auth-dialog.tsx

@@ -3,18 +3,31 @@ import {
   Dialog, DialogContent, DialogHeader, DialogTitle, DialogDescription,
 } from "@houston-ai/core";
 import { Loader2, ExternalLink } from "lucide-react";
-import type { ComposioAuthState } from "../hooks/use-composio-auth";
+
+/**
+ * Structural shape shared by every provider's sign-in hook
+ * (`useComposioAuth`, `useIntegrationsAuth`). Lets one dialog component
+ * render the in-progress UI regardless of which provider is active.
+ */
+interface AuthStateShape {
+  open: boolean;
+  phase: "idle" | "waiting" | "error";
+  loginUrl: string | null;
+  error: string | null;
+}
 
 interface ComposioAuthDialogProps {
-  state: ComposioAuthState;
+  state: AuthStateShape;
   onClose: () => void;
   onReopenBrowser: () => void;
 }
 
 /**
- * Sign-in dialog for Composio. Always shows the login URL as a
- * clickable button as soon as `state.loginUrl` is set, so the user
- * can always manually open it even if the auto-open failed.
+ * Sign-in dialog used for both Composio and Merge flows — the shape is
+ * identical so one component renders the in-progress UI regardless of
+ * which provider is active. Always shows the login URL as a clickable
+ * button as soon as `state.loginUrl` is set, so the user can always
+ * manually open it even if the auto-open failed.
  */
 export function ComposioAuthDialog({
   state,