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+# PR 4: MS Teams Stub Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Ship a minimal `fabro-teams` crate with a `TeamsService` that satisfies the `ChatService` contract for a pure-inbound-HTTP provider — no outbound connection, no real JWT validation, returns 200 for any POST — wired into `chat_services` in `fabro-server`.
+
+**Architecture:** Two-module crate (`lib.rs` for credential resolution, `service.rs` for `TeamsService`). `TeamsIntegrationSettings` and `FABRO_TEAMS_WEBHOOK_SECRET` were added in PR 3. This PR creates the crate, wires it into the server, and confirms the `ChatService` contract holds for a no-op provider. Real Teams JWT validation, Adaptive Card formatting, and event routing are explicitly deferred (out of scope).
+
+**Tech Stack:** Rust, `async-trait`, `fabro-chat`, `fabro-static`, `fabro-types`
+
+**Spec:** `docs/superpowers/specs/2026-06-13-chat-service-trait-and-providers.md` — §Phase 3: MS Teams Stubs, §Server Wiring
+
+**Branches:** Stacks on PR 3. Branch from PR 3's branch or from `main` after PR 3 merges.
+
+---
+
+## Before you start
+
+```
+cargo nextest run --workspace
+```
+
+All tests must pass before you make any changes.
+
+---
+
+## File Structure
+
+**Create:**
+- `lib/crates/fabro-teams/Cargo.toml`
+- `lib/crates/fabro-teams/src/lib.rs` — credential resolution
+- `lib/crates/fabro-teams/src/service.rs` — `TeamsService` + `impl ChatService`
+
+**Modify:**
+- `lib/crates/fabro-server/Cargo.toml` — add `fabro-teams` dependency
+- `lib/crates/fabro-server/src/server.rs` — wire `TeamsService` into `chat_services` construction
+
+---
+
+### Task 1: Create `fabro-teams` crate skeleton
+
+**Files:**
+- Create: `lib/crates/fabro-teams/Cargo.toml`
+- Create: `lib/crates/fabro-teams/src/lib.rs`
+
+- [ ] **Step 1: Write the failing credential resolution tests**
+
+Create `lib/crates/fabro-teams/src/lib.rs` with tests only (no implementation yet):
+
+```rust
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use fabro_static::EnvVars;
+
+    #[test]
+    fn missing_when_secret_absent() {
+        let result = resolve_credentials_status_with_lookup(|_| None);
+        assert!(matches!(result, TeamsCredentialResolution::Missing { .. }));
+    }
+
+    #[test]
+    fn missing_when_secret_empty() {
+        let result = resolve_credentials_status_with_lookup(|_| Some(String::new()));
+        assert!(matches!(result, TeamsCredentialResolution::Missing { .. }));
+    }
+
+    #[test]
+    fn configured_when_secret_present() {
+        let result = resolve_credentials_status_with_lookup(|name| {
+            if name == EnvVars::FABRO_TEAMS_WEBHOOK_SECRET {
+                Some("secret123".into())
+            } else {
+                None
+            }
+        });
+        match result {
+            TeamsCredentialResolution::Configured(creds) => {
+                assert_eq!(creds.webhook_secret, "secret123");
+            }
+            _ => panic!("expected Configured"),
+        }
+    }
+
+    #[test]
+    fn missing_lists_correct_env_var() {
+        let result = resolve_credentials_status_with_lookup(|_| None);
+        match result {
+            TeamsCredentialResolution::Missing { env_vars } => {
+                assert!(env_vars.contains(&EnvVars::FABRO_TEAMS_WEBHOOK_SECRET));
+            }
+            _ => panic!("expected Missing"),
+        }
+    }
+}
+```
+
+- [ ] **Step 2: Create `Cargo.toml`**
+
+```toml
+[package]
+name    = "fabro-teams"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+async-trait.workspace = true
+bytes.workspace = true
+fabro-chat  = { path = "../fabro-chat" }
+fabro-static = { path = "../fabro-static" }
+fabro-types = { path = "../fabro-types" }
+http = "1"
+tracing.workspace = true
+
+[dev-dependencies]
+fabro-chat = { path = "../fabro-chat", features = ["test-support"] }
+tokio = { workspace = true, features = ["rt-multi-thread", "macros"] }
+```
+
+- [ ] **Step 3: Run tests to confirm they fail**
+
+```
+cargo nextest run -p fabro-teams
+```
+
+Expected: FAIL — types not defined yet.
+
+- [ ] **Step 4: Implement `lib.rs`**
+
+```rust
+pub mod service;
+
+pub use service::TeamsService;
+
+use fabro_static::EnvVars;
+
+#[derive(Debug, Clone)]
+pub struct TeamsCredentials {
+    pub webhook_secret: String,
+}
+
+#[derive(Debug, Clone)]
+pub enum TeamsCredentialResolution {
+    Configured(TeamsCredentials),
+    Missing { env_vars: Vec<&'static str> },
+}
+
+pub fn resolve_credentials_status_with_lookup(
+    lookup: impl Fn(&str) -> Option<String>,
+) -> TeamsCredentialResolution {
+    match non_empty(lookup(EnvVars::FABRO_TEAMS_WEBHOOK_SECRET)) {
+        Some(webhook_secret) => {
+            TeamsCredentialResolution::Configured(TeamsCredentials { webhook_secret })
+        }
+        None => TeamsCredentialResolution::Missing {
+            env_vars: vec![EnvVars::FABRO_TEAMS_WEBHOOK_SECRET],
+        },
+    }
+}
+
+fn non_empty(value: Option<String>) -> Option<String> {
+    value.filter(|s| !s.is_empty())
+}
+
+#[cfg(test)]
+mod tests {
+    // ... (tests from Step 1 go here)
+}
+```
+
+Add a placeholder `service.rs` so the crate compiles:
+
+```rust
+// lib/crates/fabro-teams/src/service.rs
+// placeholder
+```
+
+- [ ] **Step 5: Run tests**
+
+```
+cargo nextest run -p fabro-teams
+```
+
+Expected: PASS (credential tests pass; `service.rs` is a placeholder).
+
+- [ ] **Step 6: Commit**
+
+```bash
+git add lib/crates/fabro-teams/
+git commit -m "feat(teams): create crate skeleton with credential resolution"
+```
+
+---
+
+### Task 2: Implement `TeamsService`
+
+**Files:**
+- Modify: `lib/crates/fabro-teams/src/service.rs`
+
+- [ ] **Step 1: Write tests**
+
+```rust
+// lib/crates/fabro-teams/src/service.rs
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use fabro_chat::test_support::assert_chat_service_contract;
+    use fabro_chat::ChatService;
+
+    fn test_service() -> TeamsService {
+        TeamsService::new("webhook-secret".into())
+    }
+
+    #[tokio::test]
+    async fn chat_service_contract_holds() {
+        assert_chat_service_contract(&test_service()).await;
+    }
+
+    #[test]
+    fn kind_is_teams() {
+        assert_eq!(test_service().kind(), fabro_chat::ChatProviderKind::Teams);
+    }
+
+    #[tokio::test]
+    async fn start_returns_immediately() {
+        let svc = test_service();
+        let on_submit = std::sync::Arc::new(|_| {});
+        // Must return without blocking — timeout if it doesn't
+        tokio::time::timeout(
+            std::time::Duration::from_millis(100),
+            svc.start(on_submit),
+        )
+        .await
+        .expect("start() should return immediately for Teams stub");
+    }
+
+    #[tokio::test]
+    async fn handle_webhook_any_body_is_200() {
+        let svc = test_service();
+        let outcome = svc
+            .handle_webhook("", "", &http::HeaderMap::new(), &bytes::Bytes::from("{}"))
+            .await;
+        assert_eq!(outcome.status, 200);
+    }
+
+    #[tokio::test]
+    async fn handle_webhook_empty_body_is_200() {
+        let svc = test_service();
+        let outcome = svc
+            .handle_webhook("", "", &http::HeaderMap::new(), &bytes::Bytes::new())
+            .await;
+        assert_eq!(outcome.status, 200);
+    }
+
+    #[test]
+    fn connection_status_is_always_connected() {
+        use fabro_types::IntegrationConnectionState;
+        let svc = test_service();
+        let status = svc.connection_status();
+        assert_eq!(status.status, IntegrationConnectionState::Connected);
+    }
+}
+```
+
+- [ ] **Step 2: Run tests to confirm failure**
+
+```
+cargo nextest run -p fabro-teams -- service
+```
+
+Expected: FAIL.
+
+- [ ] **Step 3: Implement `TeamsService`**
+
+```rust
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use bytes::Bytes;
+use fabro_chat::{
+    AnswerSubmission, ChatEventContext, ChatProviderKind, ChatService, WebhookOutcome,
+};
+use fabro_types::{
+    EventEnvelope, IntegrationConnectionKind, IntegrationConnectionState,
+    IntegrationConnectionStatus,
+};
+use http::HeaderMap;
+use tracing::info;
+
+pub struct TeamsService {
+    _webhook_secret: String,
+}
+
+impl TeamsService {
+    pub fn new(webhook_secret: String) -> Self {
+        Self { _webhook_secret: webhook_secret }
+    }
+}
+
+#[async_trait]
+impl ChatService for TeamsService {
+    fn kind(&self) -> ChatProviderKind {
+        ChatProviderKind::Teams
+    }
+
+    async fn start(&self, _on_submit: Arc<dyn Fn(AnswerSubmission) + Send + Sync>) {
+        info!("Teams: no outbound connection (pure inbound HTTP)");
+        // Documented no-op: Teams delivers events via HTTP POST, not outbound WebSocket.
+    }
+
+    async fn handle_event(&self, _envelope: &EventEnvelope, _context: &dyn ChatEventContext) {
+        info!("Teams notifications not yet implemented");
+    }
+
+    async fn handle_webhook(
+        &self,
+        _sub_path: &str,
+        _query_string: &str,
+        _headers: &HeaderMap,
+        _body: &Bytes,
+    ) -> WebhookOutcome {
+        WebhookOutcome { status: 200, body: None }
+    }
+
+    fn connection_status(&self) -> IntegrationConnectionStatus {
+        IntegrationConnectionStatus {
+            kind:              IntegrationConnectionKind::None,
+            status:            IntegrationConnectionState::Connected,
+            last_connected_at: None,
+            last_error:        None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    // ... (tests from Step 1 go here)
+}
+```
+
+> **Note:** `IntegrationConnectionKind::None` may not exist yet — check `fabro-types`. If the
+> enum only has `SocketMode` and `WebSocket`, add `None` as a variant (or use a suitable
+> existing variant like `NotApplicable`). If adding a new variant, update any exhaustive matches
+> in the codebase. Use `grep -rn "IntegrationConnectionKind" lib/` to find all match sites.
+
+- [ ] **Step 4: Run tests**
+
+```
+cargo nextest run -p fabro-teams
+```
+
+Expected: PASS.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add lib/crates/fabro-teams/src/service.rs
+git commit -m "feat(teams): implement TeamsService stub"
+```
+
+---
+
+### Task 3: Wire `TeamsService` into `fabro-server`
+
+**Files:**
+- Modify: `lib/crates/fabro-server/Cargo.toml`
+- Modify: `lib/crates/fabro-server/src/server.rs`
+
+- [ ] **Step 1: Add `fabro-teams` to `fabro-server` Cargo.toml**
+
+```toml
+fabro-teams = { path = "../fabro-teams" }
+```
+
+- [ ] **Step 2: Add `use` import in `server.rs`**
+
+```rust
+use fabro_teams::{TeamsService, TeamsCredentialResolution,
+                  resolve_credentials_status_with_lookup as resolve_teams_credentials};
+```
+
+- [ ] **Step 3: Extend `chat_services` construction**
+
+In the `build_app_state` block that builds the `chat_services` vec, add after the Mattermost
+section:
+
+```rust
+{
+    let teams_settings = &current_server_settings.server.integrations.teams;
+    if teams_settings.enabled {
+        let vault_guard = vault.try_read().ok();
+        match resolve_teams_credentials(|name| {
+            vault_guard.as_ref().and_then(|v| v.get(name).map(str::to_string))
+        }) {
+            TeamsCredentialResolution::Configured(creds) => {
+                info!("Teams integration enabled (stub — inbound HTTP only)");
+                chat_services.push(Arc::new(TeamsService::new(creds.webhook_secret)));
+            }
+            TeamsCredentialResolution::Missing { env_vars } => {
+                info!(
+                    missing_env_vars = %env_vars.join(","),
+                    "Teams integration disabled: missing credentials"
+                );
+            }
+        }
+    } else {
+        info!("Teams integration disabled by server configuration");
+    }
+}
+```
+
+- [ ] **Step 4: Build and run tests**
+
+```
+cargo build -p fabro-server
+cargo nextest run -p fabro-server
+```
+
+Expected: PASS.
+
+- [ ] **Step 5: Commit**
+
+```bash
+git add lib/crates/fabro-server/Cargo.toml lib/crates/fabro-server/src/server.rs
+git commit -m "feat(server): wire TeamsService stub into chat_services"
+```
+
+---
+
+### Task 4: Full validation
+
+- [ ] **Step 1: Run the full workspace test suite**
+
+```
+cargo nextest run --workspace
+```
+
+Expected: all green.
+
+- [ ] **Step 2: Check formatting**
+
+```
+cargo +nightly-2026-04-14 fmt --check --all
+```
+
+Fix if needed:
+```
+cargo +nightly-2026-04-14 fmt --all
+git add -u && git commit -m "style: fmt after teams stub"
+```
+
+- [ ] **Step 3: Run clippy**
+
+```
+cargo +nightly-2026-04-14 clippy --workspace --all-targets -- -D warnings
+```
+
+Fix all warnings before merging. Pay particular attention to `dead_code` warnings on
+`TeamsService::_webhook_secret` — if clippy flags the leading underscore convention, either
+suppress with `#[allow(dead_code)]` or restructure to consume the value (e.g., store as `()`
+until real validation is implemented, and add a `#[expect(dead_code, reason = "...")]`).
+
+- [ ] **Step 4: Verify the full stacked-PR picture**
+
+At the end of PR 4, the workspace should contain:
+- `fabro-chat` — `ChatService` trait, `AnswerSubmission`, `WebhookOutcome`, `ChatProviderKind`, `ChatEventContext`, `MockChatEventContext`
+- `fabro-slack` — `SlackService implements ChatService` (moved from server.rs)
+- `fabro-mattermost` — `MattermostService implements ChatService` (new)
+- `fabro-teams` — `TeamsService implements ChatService` (new, stub)
+- `fabro-server` — `chat_services: Vec<Arc<dyn ChatService>>`, `ChatEventContext for AppState`, `start_chat_services`, `POST /api/v1/webhooks/:provider` route
+
+Confirm by running:
+
+```
+grep -rn "ChatService" lib/crates/fabro-{slack,mattermost,teams}/src/service.rs
+```
+
+Expected: each file shows `impl ChatService for <Name>Service`.