diff --git a/CLAUDE.md b/CLAUDE.md
index 298da6b..4933bb0 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -219,22 +219,14 @@ for SSE out of the box. 2 integration tests in `cortex-gateway/tests/streaming.r
   incremental delivery (time spread between first and last chunk)
 - `test_streaming_done_terminator` — verifies `data: [DONE]` is forwarded
 
-### Phase 3: Poller + live `/v1/models`
+### Phase 3: Poller + live `/v1/models` ✅
 
-**Goal:** The background poller refreshes node state from real (or mock)
-mistral.rs instances. `GET /v1/models` returns live, aggregated data.
-
-**Files to change:**
-- `cortex-gateway/src/poller.rs` — already implemented but needs testing
-- `cortex-gateway/src/handlers.rs` — the `list_models` handler reads
-  from `CortexState`; verify it reflects poller updates
-- `tests/` — test that:
-  1. Mock backend serves `/v1/models` with 2 models (1 loaded, 1 unloaded)
-  2. After poller runs, `GET /v1/models` on cortex returns both with
-     correct status and node attribution
-
-**Done when:** Poller test passes. The router in Phase 1 now routes
-based on live-polled state instead of seed data.
+Completed. Extracted `poll_once()` from `poll_loop()` for testability.
+4 tests in `cortex-gateway/tests/poller.rs`:
+- `test_poller_discovers_models` — 2 models (loaded + unloaded) discovered with correct status
+- `test_poller_updates_gateway_models_endpoint` — `/v1/models` reflects polled state with node attribution
+- `test_poller_marks_unreachable_node_unhealthy` — unreachable node flipped to unhealthy
+- `test_poller_removes_stale_models` — model removed from upstream is pruned from state
 
 ### Phase 4: Eviction
 
diff --git a/crates/cortex-gateway/src/poller.rs b/crates/cortex-gateway/src/poller.rs
index 60b5666..27a047c 100644
--- a/crates/cortex-gateway/src/poller.rs
+++ b/crates/cortex-gateway/src/poller.rs
@@ -12,13 +12,18 @@ const POLL_INTERVAL: Duration = Duration::from_secs(10);
 /// Runs forever, polling all nodes on a fixed interval.
 pub async fn poll_loop(fleet: Arc<CortexState>) {
     loop {
-        for nc in &fleet.node_configs {
-            poll_node(&fleet, &nc.name, &nc.endpoint).await;
-        }
+        poll_once(&fleet).await;
         tokio::time::sleep(POLL_INTERVAL).await;
     }
 }
 
+/// Poll all nodes once. Used by `poll_loop` and available for testing.
+pub async fn poll_once(fleet: &CortexState) {
+    for nc in &fleet.node_configs {
+        poll_node(fleet, &nc.name, &nc.endpoint).await;
+    }
+}
+
 async fn poll_node(fleet: &CortexState, name: &str, endpoint: &str) {
     let url = format!("{endpoint}/v1/models");
 
diff --git a/crates/cortex-gateway/tests/common/mod.rs b/crates/cortex-gateway/tests/common/mod.rs
index 05be7f2..db60fff 100644
--- a/crates/cortex-gateway/tests/common/mod.rs
+++ b/crates/cortex-gateway/tests/common/mod.rs
@@ -130,10 +130,38 @@ pub async fn spawn_streaming_mock_backend(chunk_count: usize, chunk_delay: Durat
     format!("http://{addr}")
 }
 
+/// Spawns a mock backend with a custom `/v1/models` response.
+pub async fn spawn_mock_backend_with_models(models_response: Value) -> String {
+    let app = Router::new()
+        .route("/v1/chat/completions", post(mock_chat_completions))
+        .route(
+            "/v1/models",
+            get(move || {
+                let resp = models_response.clone();
+                async move { Json(resp) }
+            }),
+        );
+
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr = listener.local_addr().unwrap();
+    tokio::spawn(async move {
+        axum::serve(listener, app).await.unwrap();
+    });
+
+    format!("http://{addr}")
+}
+
 /// Spawns the cortex gateway with a single node pointing at `mock_url`.
 /// The node is pre-seeded as healthy with one loaded model ("test-model").
 /// Returns the gateway's base URL.
 pub async fn spawn_gateway(mock_url: &str) -> String {
+    let (_, url) = spawn_gateway_with_state(mock_url).await;
+    url
+}
+
+/// Like `spawn_gateway` but also returns the shared `CortexState` so tests
+/// can call `poll_once` or inspect state directly.
+pub async fn spawn_gateway_with_state(mock_url: &str) -> (Arc<CortexState>, String) {
     let config = GatewayConfig {
         gateway: GatewaySettings {
             listen: "127.0.0.1:0".into(),
@@ -170,7 +198,7 @@ pub async fn spawn_gateway(mock_url: &str) -> String {
         );
     }
 
-    let app = cortex_gateway::build_app(fleet);
+    let app = cortex_gateway::build_app(Arc::clone(&fleet));
 
     let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
     let addr = listener.local_addr().unwrap();
@@ -178,5 +206,5 @@ pub async fn spawn_gateway(mock_url: &str) -> String {
         axum::serve(listener, app).await.unwrap();
     });
 
-    format!("http://{addr}")
+    (fleet, format!("http://{addr}"))
 }
diff --git a/crates/cortex-gateway/tests/poller.rs b/crates/cortex-gateway/tests/poller.rs
new file mode 100644
index 0000000..1fd741b
--- /dev/null
+++ b/crates/cortex-gateway/tests/poller.rs
@@ -0,0 +1,271 @@
+mod common;
+
+use cortex_core::config::{
+    EvictionSettings, EvictionStrategy, GatewayConfig, GatewaySettings, NodeConfig,
+};
+use cortex_core::node::ModelStatus;
+use cortex_gateway::state::CortexState;
+use serde_json::json;
+use std::sync::Arc;
+
+#[tokio::test]
+async fn test_poller_discovers_models() {
+    // Mock backend reports 2 models: one loaded, one unloaded.
+    let mock_url = common::spawn_mock_backend_with_models(json!({
+        "object": "list",
+        "data": [
+            { "id": "model-a", "object": "model", "status": "loaded" },
+            { "id": "model-b", "object": "model", "status": "unloaded" }
+        ]
+    }))
+    .await;
+
+    let config = GatewayConfig {
+        gateway: GatewaySettings {
+            listen: "127.0.0.1:0".into(),
+            metrics_listen: "127.0.0.1:0".into(),
+        },
+        eviction: EvictionSettings {
+            strategy: EvictionStrategy::Lru,
+            defrag_after_cycles: 0,
+        },
+        nodes: vec![NodeConfig {
+            name: "test-node".into(),
+            endpoint: mock_url,
+            vram_mb: 24000,
+            pinned: vec![],
+        }],
+    };
+
+    let fleet = Arc::new(CortexState::from_config(&config));
+
+    // Before polling: node is unhealthy, no models.
+    {
+        let nodes = fleet.nodes.read().await;
+        let node = nodes.get("test-node").unwrap();
+        assert!(!node.healthy);
+        assert!(node.models.is_empty());
+    }
+
+    // Poll once.
+    cortex_gateway::poller::poll_once(&fleet).await;
+
+    // After polling: node is healthy, both models discovered with correct status.
+    {
+        let nodes = fleet.nodes.read().await;
+        let node = nodes.get("test-node").unwrap();
+        assert!(node.healthy);
+        assert_eq!(node.models.len(), 2);
+
+        let model_a = node.models.get("model-a").expect("model-a should exist");
+        assert_eq!(model_a.status, ModelStatus::Loaded);
+
+        let model_b = node.models.get("model-b").expect("model-b should exist");
+        assert_eq!(model_b.status, ModelStatus::Unloaded);
+
+        assert!(node.last_poll.is_some());
+    }
+}
+
+#[tokio::test]
+async fn test_poller_updates_gateway_models_endpoint() {
+    // Mock backend with 2 models.
+    let mock_url = common::spawn_mock_backend_with_models(json!({
+        "object": "list",
+        "data": [
+            { "id": "model-x", "object": "model", "status": "loaded" },
+            { "id": "model-y", "object": "model", "status": "loaded" }
+        ]
+    }))
+    .await;
+
+    let config = GatewayConfig {
+        gateway: GatewaySettings {
+            listen: "127.0.0.1:0".into(),
+            metrics_listen: "127.0.0.1:0".into(),
+        },
+        eviction: EvictionSettings {
+            strategy: EvictionStrategy::Lru,
+            defrag_after_cycles: 0,
+        },
+        nodes: vec![NodeConfig {
+            name: "poll-node".into(),
+            endpoint: mock_url,
+            vram_mb: 24000,
+            pinned: vec![],
+        }],
+    };
+
+    let fleet = Arc::new(CortexState::from_config(&config));
+
+    // Poll to discover models and mark node healthy.
+    cortex_gateway::poller::poll_once(&fleet).await;
+
+    // Start gateway with the polled state.
+    let app = cortex_gateway::build_app(Arc::clone(&fleet));
+    let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr = listener.local_addr().unwrap();
+    tokio::spawn(async move {
+        axum::serve(listener, app).await.unwrap();
+    });
+
+    // Query /v1/models on the gateway.
+    let client = reqwest::Client::new();
+    let resp = client
+        .get(format!("http://{addr}/v1/models"))
+        .send()
+        .await
+        .expect("request should succeed");
+
+    assert_eq!(resp.status(), 200);
+
+    let body: serde_json::Value = resp.json().await.unwrap();
+    let data = body["data"].as_array().expect("data should be an array");
+    assert_eq!(data.len(), 2);
+
+    let ids: Vec<&str> = data.iter().filter_map(|m| m["id"].as_str()).collect();
+    assert!(ids.contains(&"model-x"));
+    assert!(ids.contains(&"model-y"));
+
+    // Verify node attribution in locations.
+    for model in data {
+        let locations = model["locations"].as_array().expect("locations array");
+        assert_eq!(locations.len(), 1);
+        assert_eq!(locations[0]["node"], "poll-node");
+    }
+}
+
+#[tokio::test]
+async fn test_poller_marks_unreachable_node_unhealthy() {
+    let config = GatewayConfig {
+        gateway: GatewaySettings {
+            listen: "127.0.0.1:0".into(),
+            metrics_listen: "127.0.0.1:0".into(),
+        },
+        eviction: EvictionSettings {
+            strategy: EvictionStrategy::Lru,
+            defrag_after_cycles: 0,
+        },
+        nodes: vec![NodeConfig {
+            name: "dead-node".into(),
+            endpoint: "http://127.0.0.1:1".into(), // unreachable
+            vram_mb: 24000,
+            pinned: vec![],
+        }],
+    };
+
+    let fleet = Arc::new(CortexState::from_config(&config));
+
+    // Manually mark healthy to verify poller flips it.
+    {
+        let mut nodes = fleet.nodes.write().await;
+        nodes.get_mut("dead-node").unwrap().healthy = true;
+    }
+
+    cortex_gateway::poller::poll_once(&fleet).await;
+
+    let nodes = fleet.nodes.read().await;
+    assert!(!nodes.get("dead-node").unwrap().healthy);
+}
+
+#[tokio::test]
+async fn test_poller_removes_stale_models() {
+    // Start with a mock that reports 2 models.
+    let mock_url = common::spawn_mock_backend_with_models(json!({
+        "object": "list",
+        "data": [
+            { "id": "keep-me", "object": "model", "status": "loaded" },
+            { "id": "drop-me", "object": "model", "status": "loaded" }
+        ]
+    }))
+    .await;
+
+    let config = GatewayConfig {
+        gateway: GatewaySettings {
+            listen: "127.0.0.1:0".into(),
+            metrics_listen: "127.0.0.1:0".into(),
+        },
+        eviction: EvictionSettings {
+            strategy: EvictionStrategy::Lru,
+            defrag_after_cycles: 0,
+        },
+        nodes: vec![NodeConfig {
+            name: "test-node".into(),
+            endpoint: mock_url,
+            vram_mb: 24000,
+            pinned: vec![],
+        }],
+    };
+
+    let fleet = Arc::new(CortexState::from_config(&config));
+    cortex_gateway::poller::poll_once(&fleet).await;
+
+    // Verify both models exist.
+    {
+        let nodes = fleet.nodes.read().await;
+        assert_eq!(nodes.get("test-node").unwrap().models.len(), 2);
+    }
+
+    // Now spin up a new mock that only reports one model, and re-point the node.
+    let new_mock_url = common::spawn_mock_backend_with_models(json!({
+        "object": "list",
+        "data": [
+            { "id": "keep-me", "object": "model", "status": "loaded" }
+        ]
+    }))
+    .await;
+
+    // Update the node endpoint to point at the new mock.
+    // We can't change node_configs (they're immutable), so instead we'll
+    // create a new fleet with the updated endpoint and poll that.
+    let config2 = GatewayConfig {
+        gateway: GatewaySettings {
+            listen: "127.0.0.1:0".into(),
+            metrics_listen: "127.0.0.1:0".into(),
+        },
+        eviction: EvictionSettings {
+            strategy: EvictionStrategy::Lru,
+            defrag_after_cycles: 0,
+        },
+        nodes: vec![NodeConfig {
+            name: "test-node".into(),
+            endpoint: new_mock_url,
+            vram_mb: 24000,
+            pinned: vec![],
+        }],
+    };
+
+    let fleet2 = Arc::new(CortexState::from_config(&config2));
+
+    // Seed the stale model so we can verify it gets removed.
+    {
+        let mut nodes = fleet2.nodes.write().await;
+        let node = nodes.get_mut("test-node").unwrap();
+        node.models.insert(
+            "keep-me".into(),
+            cortex_core::node::ModelEntry {
+                id: "keep-me".into(),
+                status: ModelStatus::Loaded,
+                last_accessed: None,
+                vram_estimate_mb: None,
+            },
+        );
+        node.models.insert(
+            "drop-me".into(),
+            cortex_core::node::ModelEntry {
+                id: "drop-me".into(),
+                status: ModelStatus::Loaded,
+                last_accessed: None,
+                vram_estimate_mb: None,
+            },
+        );
+    }
+
+    cortex_gateway::poller::poll_once(&fleet2).await;
+
+    let nodes = fleet2.nodes.read().await;
+    let node = nodes.get("test-node").unwrap();
+    assert_eq!(node.models.len(), 1);
+    assert!(node.models.contains_key("keep-me"));
+    assert!(!node.models.contains_key("drop-me"));
+}