diff --git a/server/src/http/gateway/mcp.rs b/server/src/http/gateway/mcp.rs
index 06ad1f2f..840fdf4f 100644
--- a/server/src/http/gateway/mcp.rs
+++ b/server/src/http/gateway/mcp.rs
@@ -350,7 +350,25 @@ pub async fn gateway_mcp_post_handler(
                     Some(project) => {
                         proxy_and_respond_for_project(&state, project, &bytes, rpc.id).await
                     }
-                    None => proxy_and_respond(&state, &bytes, rpc.id).await,
+                    None if is_create_tool(tool_name) => {
+                        // Story 1225 AC 3: with >1 project registered, a
+                        // create call omitting `project` is ambiguous — fail
+                        // loudly instead of silently filing into whichever
+                        // project happens to be active.
+                        let project_count = state.projects.read().await.len();
+                        if project_count > 1 {
+                            to_json_response(JsonRpcResponse::error(
+                                rpc.id,
+                                -32602,
+                                format!(
+                                    "'{tool_name}' requires an explicit `project` argument when more than one project is registered (see list_projects) — the active project is not used implicitly for creates."
+                                ),
+                            ))
+                        } else {
+                            proxy_and_respond_with_resolved_project(&state, &bytes, rpc.id).await
+                        }
+                    }
+                    None => proxy_and_respond_with_resolved_project(&state, &bytes, rpc.id).await,
                 }
             }
         }
@@ -376,6 +394,50 @@ async fn proxy_and_respond(state: &GatewayState, bytes: &[u8], id: Option<Value>
     }
 }
 
+/// Returns `true` for tool names that create a new work item or resource
+/// (`create_bug`, `create_story`, `create_worktree`, ...), used to gate
+/// implicit active-project routing behind an explicit `project` argument
+/// when the destination is ambiguous (story 1225 AC 3).
+fn is_create_tool(tool_name: &str) -> bool {
+    tool_name.starts_with("create_")
+}
+
+/// Proxy a request to the active project and, on success, annotate the
+/// response with which project actually handled it (story 1225 AC 3) — so a
+/// caller who omitted `project` can see whether their call landed where they
+/// expected instead of silently trusting `active_project`.
+async fn proxy_and_respond_with_resolved_project(
+    state: &GatewayState,
+    bytes: &[u8],
+    id: Option<Value>,
+) -> Response {
+    let active = state.active_project.read().await.clone();
+    match state.proxy_active_mcp(bytes).await {
+        Ok(resp_body) => Response::builder()
+            .status(StatusCode::OK)
+            .header("Content-Type", "application/json")
+            .body(Body::from(annotate_resolved_project(&resp_body, &active))),
+        Err(e) => to_json_response(JsonRpcResponse::error(
+            id,
+            -32603,
+            format!("proxy error: {e}"),
+        )),
+    }
+}
+
+/// Insert a `resolved_project` field into a JSON-RPC `result` object,
+/// leaving the bytes unchanged if they don't parse as JSON or `result` isn't
+/// an object (e.g. an error response, which has no `result` at all).
+fn annotate_resolved_project(bytes: &[u8], project: &str) -> Vec<u8> {
+    let Ok(mut value) = serde_json::from_slice::<Value>(bytes) else {
+        return bytes.to_vec();
+    };
+    if let Some(result) = value.get_mut("result").and_then(|r| r.as_object_mut()) {
+        result.insert("resolved_project".to_string(), json!(project));
+    }
+    serde_json::to_vec(&value).unwrap_or_else(|_| bytes.to_vec())
+}
+
 /// Proxy a request to an explicitly named project (story 1208 AC 1) rather
 /// than whatever project is currently active, so a single ops/LLM session
 /// can address any registered project per-call without a prior
@@ -1310,6 +1372,7 @@ async fn handle_pipeline_get(state: &GatewayState, id: Option<Value>) -> JsonRpc
 mod tests {
     use super::*;
     use crate::service::gateway::config::{GatewayConfig, ProjectEntry};
+    use poem::EndpointExt as _;
     use std::collections::BTreeMap;
     use std::sync::Arc;
 
@@ -1688,4 +1751,232 @@ mod tests {
         inject_project_arg_schema(&mut tools);
         assert_eq!(tools[0], json!({"name": "no_schema"}));
     }
+
+    // ── project arg is honored end-to-end, not silently misrouted (story 1225) ─
+
+    /// Register a fake sled connection for `name` whose background task
+    /// answers every `mcp_request` with a canned response naming itself, so
+    /// tests can assert *which* project actually handled a routed call.
+    async fn spawn_fake_sled(name: &str) -> gateway::SledConnection {
+        let (tx, mut rx) =
+            tokio::sync::mpsc::unbounded_channel::<crate::sled_uplink::UplinkEnvelope>();
+        let in_flight: Arc<
+            tokio::sync::Mutex<
+                std::collections::HashMap<String, tokio::sync::oneshot::Sender<Value>>,
+            >,
+        > = Arc::new(tokio::sync::Mutex::new(std::collections::HashMap::new()));
+        let in_flight_task = Arc::clone(&in_flight);
+        let label = name.to_string();
+        tokio::spawn(async move {
+            while let Some(env) = rx.recv().await {
+                if let Some(sender) = in_flight_task.lock().await.remove(&env.req_id) {
+                    let _ = sender.send(json!({
+                        "jsonrpc": "2.0",
+                        "id": 1,
+                        "result": { "content": [{ "type": "text", "text": format!("handled_by:{label}") }] }
+                    }));
+                }
+            }
+        });
+        gateway::SledConnection {
+            tx,
+            last_heartbeat_ms: Arc::new(std::sync::atomic::AtomicI64::new(
+                chrono::Utc::now().timestamp_millis(),
+            )),
+            in_flight,
+        }
+    }
+
+    async fn make_two_project_state(dir: &std::path::Path) -> Arc<GatewayState> {
+        let mut projects = BTreeMap::new();
+        projects.insert("alpha".to_string(), ProjectEntry::with_url("http://a:3001"));
+        projects.insert("beta".to_string(), ProjectEntry::with_url("http://b:3002"));
+        let config = GatewayConfig {
+            projects,
+            sled_tokens: BTreeMap::new(),
+            release_channels: BTreeMap::new(),
+        };
+        let state = Arc::new(GatewayState::new(config, dir.to_path_buf(), 3000).unwrap());
+        assert_eq!(*state.active_project.read().await, "alpha");
+        state
+            .register_sled_connection("alpha".to_string(), spawn_fake_sled("alpha").await)
+            .await;
+        state
+            .register_sled_connection("beta".to_string(), spawn_fake_sled("beta").await)
+            .await;
+        state
+    }
+
+    #[tokio::test]
+    async fn create_tool_with_explicit_project_lands_in_non_active_project() {
+        let dir = tempfile::tempdir().unwrap();
+        let state = make_two_project_state(dir.path()).await;
+        let app = poem::Route::new()
+            .at("/mcp", poem::post(gateway_mcp_post_handler))
+            .data(state);
+        let cli = poem::test::TestClient::new(app);
+
+        let rpc_body = serde_json::to_vec(&json!({
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "tools/call",
+            "params": {
+                "name": "create_bug",
+                "arguments": { "project": "beta", "title": "x", "description": "y" }
+            }
+        }))
+        .unwrap();
+        let resp = cli
+            .post("/mcp")
+            .header("content-type", "application/json")
+            .body(rpc_body)
+            .send()
+            .await;
+        let parsed: Value = resp.0.into_body().into_json().await.unwrap();
+        assert_eq!(
+            parsed["result"]["content"][0]["text"], "handled_by:beta",
+            "explicit project=beta must land in beta even though alpha is active: {parsed}"
+        );
+    }
+
+    #[tokio::test]
+    async fn read_tool_with_explicit_project_reads_from_non_active_project() {
+        let dir = tempfile::tempdir().unwrap();
+        let state = make_two_project_state(dir.path()).await;
+        let app = poem::Route::new()
+            .at("/mcp", poem::post(gateway_mcp_post_handler))
+            .data(state);
+        let cli = poem::test::TestClient::new(app);
+
+        let rpc_body = serde_json::to_vec(&json!({
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "tools/call",
+            "params": {
+                "name": "get_pipeline_status",
+                "arguments": { "project": "beta" }
+            }
+        }))
+        .unwrap();
+        let resp = cli
+            .post("/mcp")
+            .header("content-type", "application/json")
+            .body(rpc_body)
+            .send()
+            .await;
+        let parsed: Value = resp.0.into_body().into_json().await.unwrap();
+        assert_eq!(
+            parsed["result"]["content"][0]["text"], "handled_by:beta",
+            "explicit project=beta must read from beta even though alpha is active: {parsed}"
+        );
+    }
+
+    #[tokio::test]
+    async fn create_tool_without_project_errors_when_multiple_projects_registered() {
+        let dir = tempfile::tempdir().unwrap();
+        let state = make_two_project_state(dir.path()).await;
+        let app = poem::Route::new()
+            .at("/mcp", poem::post(gateway_mcp_post_handler))
+            .data(state);
+        let cli = poem::test::TestClient::new(app);
+
+        let rpc_body = serde_json::to_vec(&json!({
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "tools/call",
+            "params": {
+                "name": "create_bug",
+                "arguments": { "title": "x", "description": "y" }
+            }
+        }))
+        .unwrap();
+        let resp = cli
+            .post("/mcp")
+            .header("content-type", "application/json")
+            .body(rpc_body)
+            .send()
+            .await;
+        let parsed: Value = resp.0.into_body().into_json().await.unwrap();
+        assert!(
+            parsed["error"]["message"]
+                .as_str()
+                .unwrap()
+                .contains("requires an explicit `project`"),
+            "create call omitting `project` with >1 project registered must error, not \
+             silently file into the active project: {parsed}"
+        );
+    }
+
+    #[tokio::test]
+    async fn read_tool_without_project_annotates_resolved_project() {
+        let dir = tempfile::tempdir().unwrap();
+        let state = make_two_project_state(dir.path()).await;
+        let app = poem::Route::new()
+            .at("/mcp", poem::post(gateway_mcp_post_handler))
+            .data(state);
+        let cli = poem::test::TestClient::new(app);
+
+        let rpc_body = serde_json::to_vec(&json!({
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "tools/call",
+            "params": {
+                "name": "get_pipeline_status",
+                "arguments": {}
+            }
+        }))
+        .unwrap();
+        let resp = cli
+            .post("/mcp")
+            .header("content-type", "application/json")
+            .body(rpc_body)
+            .send()
+            .await;
+        let parsed: Value = resp.0.into_body().into_json().await.unwrap();
+        assert_eq!(
+            parsed["result"]["content"][0]["text"], "handled_by:alpha",
+            "sanity: implicit routing hit the active project: {parsed}"
+        );
+        assert_eq!(
+            parsed["result"]["resolved_project"], "alpha",
+            "omitting `project` must echo which project was actually resolved: {parsed}"
+        );
+    }
+
+    #[test]
+    fn annotate_resolved_project_inserts_field_into_result_object() {
+        let bytes = serde_json::to_vec(&json!({
+            "jsonrpc": "2.0",
+            "id": 1,
+            "result": { "content": [{ "type": "text", "text": "ok" }] }
+        }))
+        .unwrap();
+        let annotated = annotate_resolved_project(&bytes, "alpha");
+        let parsed: Value = serde_json::from_slice(&annotated).unwrap();
+        assert_eq!(parsed["result"]["resolved_project"], "alpha");
+        assert_eq!(parsed["result"]["content"][0]["text"], "ok");
+    }
+
+    #[test]
+    fn annotate_resolved_project_leaves_error_response_untouched() {
+        let bytes = serde_json::to_vec(&json!({
+            "jsonrpc": "2.0",
+            "id": 1,
+            "error": { "code": -32603, "message": "boom" }
+        }))
+        .unwrap();
+        let annotated = annotate_resolved_project(&bytes, "alpha");
+        let parsed: Value = serde_json::from_slice(&annotated).unwrap();
+        assert_eq!(parsed["error"]["message"], "boom");
+        assert!(parsed.get("result").is_none());
+    }
+
+    #[test]
+    fn is_create_tool_matches_create_prefixed_names_only() {
+        assert!(is_create_tool("create_bug"));
+        assert!(is_create_tool("create_story"));
+        assert!(is_create_tool("create_worktree"));
+        assert!(!is_create_tool("get_pipeline_status"));
+        assert!(!is_create_tool("show"));
+    }
 }