diff --git a/crates/convergio-server/tests/e2e_task_transition_syncs_agent.rs b/crates/convergio-server/tests/e2e_task_transition_syncs_agent.rs
new file mode 100644
index 0000000..b7eaf6d
--- /dev/null
+++ b/crates/convergio-server/tests/e2e_task_transition_syncs_agent.rs
@@ -0,0 +1,178 @@
+//! HTTP-level verification of P2-1: task transition auto-populates
+//! `agents.current_task_id`.
+//!
+//! Acceptance criteria (from task a1f47c57):
+//! - `POST /v1/tasks/:id/transition` with `target=in_progress` and
+//!   `agent_id` → subsequent `GET /v1/agent-registry/agents/:id`
+//!   shows `current_task_id` pointing at the task and `status=working`.
+//! - Submitting the task clears `current_task_id` and flips the agent
+//!   back to `idle`.
+//! - Unregistered agents do not cause errors.
+//! - A second claim on the same agent overwrites the first pointer.
+
+mod common;
+
+use serde_json::{json, Value};
+
+async fn register_agent(client: &reqwest::Client, base: &str, id: &str) {
+    client
+        .post(format!("{base}/v1/agent-registry/agents"))
+        .json(&json!({
+            "id": id,
+            "kind": "claude-code",
+            "capabilities": [],
+            "metadata": {}
+        }))
+        .send()
+        .await
+        .unwrap()
+        .error_for_status()
+        .unwrap();
+}
+
+async fn make_task(client: &reqwest::Client, base: &str) -> String {
+    let plan: Value = client
+        .post(format!("{base}/v1/plans"))
+        .json(&json!({"title": "test plan"}))
+        .send()
+        .await
+        .unwrap()
+        .json()
+        .await
+        .unwrap();
+    let plan_id = plan["id"].as_str().unwrap();
+    let task: Value = client
+        .post(format!("{base}/v1/plans/{plan_id}/tasks"))
+        .json(&json!({"title": "task", "wave": 1, "sequence": 1}))
+        .send()
+        .await
+        .unwrap()
+        .json()
+        .await
+        .unwrap();
+    task["id"].as_str().unwrap().to_string()
+}
+
+#[tokio::test]
+async fn claim_sets_current_task_id_and_working_status() {
+    let (base, _pool, _dir) = common::boot().await;
+    let client = reqwest::Client::new();
+    register_agent(&client, &base, "agent-x").await;
+    let task_id = make_task(&client, &base).await;
+
+    client
+        .post(format!("{base}/v1/tasks/{task_id}/transition"))
+        .json(&json!({"target": "in_progress", "agent_id": "agent-x"}))
+        .send()
+        .await
+        .unwrap()
+        .error_for_status()
+        .unwrap();
+
+    let agent: Value = client
+        .get(format!("{base}/v1/agent-registry/agents/agent-x"))
+        .send()
+        .await
+        .unwrap()
+        .json()
+        .await
+        .unwrap();
+
+    assert_eq!(agent["status"], "working");
+    assert_eq!(agent["current_task_id"], task_id.as_str());
+}
+
+#[tokio::test]
+async fn submit_clears_current_task_id_and_marks_idle() {
+    let (base, _pool, _dir) = common::boot().await;
+    let client = reqwest::Client::new();
+    register_agent(&client, &base, "agent-y").await;
+    let task_id = make_task(&client, &base).await;
+
+    client
+        .post(format!("{base}/v1/tasks/{task_id}/transition"))
+        .json(&json!({"target": "in_progress", "agent_id": "agent-y"}))
+        .send()
+        .await
+        .unwrap()
+        .error_for_status()
+        .unwrap();
+
+    client
+        .post(format!("{base}/v1/tasks/{task_id}/transition"))
+        .json(&json!({"target": "submitted", "agent_id": "agent-y"}))
+        .send()
+        .await
+        .unwrap()
+        .error_for_status()
+        .unwrap();
+
+    let agent: Value = client
+        .get(format!("{base}/v1/agent-registry/agents/agent-y"))
+        .send()
+        .await
+        .unwrap()
+        .json()
+        .await
+        .unwrap();
+
+    assert_eq!(agent["status"], "idle");
+    assert_eq!(agent["current_task_id"], Value::Null);
+}
+
+#[tokio::test]
+async fn unregistered_agent_transition_does_not_error() {
+    let (base, _pool, _dir) = common::boot().await;
+    let client = reqwest::Client::new();
+    let task_id = make_task(&client, &base).await;
+
+    let resp = client
+        .post(format!("{base}/v1/tasks/{task_id}/transition"))
+        .json(&json!({"target": "in_progress", "agent_id": "ghost-agent"}))
+        .send()
+        .await
+        .unwrap();
+
+    assert!(
+        resp.status().is_success(),
+        "unregistered agent must not cause 5xx"
+    );
+}
+
+#[tokio::test]
+async fn second_claim_overwrites_current_task_pointer() {
+    let (base, _pool, _dir) = common::boot().await;
+    let client = reqwest::Client::new();
+    register_agent(&client, &base, "agent-z").await;
+    let task_a = make_task(&client, &base).await;
+    let task_b = make_task(&client, &base).await;
+
+    client
+        .post(format!("{base}/v1/tasks/{task_a}/transition"))
+        .json(&json!({"target": "in_progress", "agent_id": "agent-z"}))
+        .send()
+        .await
+        .unwrap()
+        .error_for_status()
+        .unwrap();
+    client
+        .post(format!("{base}/v1/tasks/{task_b}/transition"))
+        .json(&json!({"target": "in_progress", "agent_id": "agent-z"}))
+        .send()
+        .await
+        .unwrap()
+        .error_for_status()
+        .unwrap();
+
+    let agent: Value = client
+        .get(format!("{base}/v1/agent-registry/agents/agent-z"))
+        .send()
+        .await
+        .unwrap()
+        .json()
+        .await
+        .unwrap();
+
+    assert_eq!(agent["current_task_id"], task_b.as_str());
+    assert_eq!(agent["status"], "working");
+}