diff --git a/src/lib/event-feed.ts b/src/lib/event-feed.ts
index 411ce08..36ddd59 100644
--- a/src/lib/event-feed.ts
+++ b/src/lib/event-feed.ts
@@ -9,6 +9,13 @@ export function decodeEvent(msg: SseMessage): FeedEvent | null {
     const inner = JSON.parse(outer.data) as Record<string, unknown>;
 
     if (outer.type === "inflight") {
+      const operation = inner.operation as string;
+      if (operation === "remove") {
+        const id = typeof inner.id === "string" ? inner.id : undefined;
+        if (id) return { type: "inflight", operation: "remove", id };
+        return null;
+      }
+      if (operation !== "snapshot" && operation !== "upsert" && operation !== "add") return null;
       const requests: InflightRequest[] = Array.isArray(inner.requests)
         ? (inner.requests as InflightRequest[])
         : Array.isArray(inner.request)
@@ -18,7 +25,7 @@ export function decodeEvent(msg: SseMessage): FeedEvent | null {
             : [];
       return {
         type: "inflight",
-        operation: inner.operation as "snapshot" | "add" | "remove",
+        operation: operation === "snapshot" ? "snapshot" : "add",
         requests,
       };
     }
diff --git a/src/lib/inflight-tracker.ts b/src/lib/inflight-tracker.ts
index ad5dbba..63ed038 100644
--- a/src/lib/inflight-tracker.ts
+++ b/src/lib/inflight-tracker.ts
@@ -13,29 +13,25 @@ export interface ModelState {
 }
 
 export type FeedEvent =
-  | { type: "inflight"; operation: "snapshot" | "add" | "remove"; requests: InflightRequest[] }
+  | { type: "inflight"; operation: "snapshot" | "add"; requests: InflightRequest[] }
+  | { type: "inflight"; operation: "remove"; id: string }
   | { type: "modelStatus"; models: ModelState[] };
 
 export type ModelRuntimeState = "stopped" | "loading" | "ready";
 
 export class InflightTracker {
-  private counts = new Map<string, number>();
+  private requests = new Map<string, string>();
   private states = new Map<string, ModelRuntimeState>();
 
   apply(event: FeedEvent): void {
     if (event.type === "inflight") {
       if (event.operation === "snapshot") {
-        const counts = new Map<string, number>();
-        for (const r of event.requests) counts.set(r.model, (counts.get(r.model) ?? 0) + 1);
-        this.counts = counts;
+        this.requests = new Map<string, string>();
+        for (const r of event.requests) if (r.id) this.requests.set(r.id, r.model);
       } else if (event.operation === "add") {
-        for (const r of event.requests) this.counts.set(r.model, (this.counts.get(r.model) ?? 0) + 1);
+        for (const r of event.requests) if (r.id) this.requests.set(r.id, r.model);
       } else if (event.operation === "remove") {
-        for (const r of event.requests) {
-          const c = this.counts.get(r.model) ?? 0;
-          if (c <= 1) this.counts.delete(r.model);
-          else this.counts.set(r.model, c - 1);
-        }
+        this.requests.delete(event.id);
       }
     } else if (event.type === "modelStatus") {
       for (const m of event.models) this.states.set(m.id, normalizeState(m.state));
@@ -43,7 +39,9 @@ export class InflightTracker {
   }
 
   count(modelId: string): number {
-    return this.counts.get(modelId) ?? 0;
+    let n = 0;
+    for (const model of this.requests.values()) if (model === modelId) n++;
+    return n;
   }
 
   state(modelId: string): ModelRuntimeState | undefined {
diff --git a/tests/event-feed.test.ts b/tests/event-feed.test.ts
index 52167bd..2a91006 100644
--- a/tests/event-feed.test.ts
+++ b/tests/event-feed.test.ts
@@ -41,6 +41,32 @@ test("decodeEvent parses an inflight add with a singular request field", () => {
   }
 });
 
+test("decodeEvent parses an inflight upsert as an add", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({
+      type: "inflight",
+      data: JSON.stringify({ operation: "upsert", request: { id: "820", model: "DeepSeek-V4-Flash-0731", elapsed_ms: 103 } }),
+    }),
+  };
+  const ev = decodeEvent(msg);
+  assert.ok(ev && ev.type === "inflight");
+  if (ev && ev.type === "inflight") {
+    assert.equal(ev.operation, "add");
+    assert.equal(ev.requests[0].id, "820");
+    assert.equal(ev.requests[0].elapsed_ms, 103);
+  }
+});
+
+test("decodeEvent parses an inflight remove with a bare id", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({ type: "inflight", data: JSON.stringify({ operation: "remove", id: "817" }) }),
+  };
+  const ev = decodeEvent(msg);
+  assert.deepEqual(ev, { type: "inflight", operation: "remove", id: "817" });
+});
+
 test("decodeEvent parses modelStatus", () => {
   const msg: SseMessage = {
     event: "message",
diff --git a/tests/inflight-tracker.test.ts b/tests/inflight-tracker.test.ts
index 0396cbe..3f4b443 100644
--- a/tests/inflight-tracker.test.ts
+++ b/tests/inflight-tracker.test.ts
@@ -18,17 +18,32 @@ test("snapshot rebuilds counts for all in-flight requests", () => {
   assert.equal(tracker.count("C"), 0);
 });
 
-test("add and remove adjust per-model counts", () => {
+test("add (upsert) is idempotent per request id", () => {
   const tracker = new InflightTracker();
   tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }] });
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }] });
   tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "2" }] });
   assert.equal(tracker.count("A"), 2);
-  tracker.apply({ type: "inflight", operation: "remove", requests: [{ model: "A", id: "1" }] });
+});
+
+test("remove is id-based and decrements the matching request", () => {
+  const tracker = new InflightTracker();
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }, { model: "B", id: "2" }] });
   assert.equal(tracker.count("A"), 1);
-  tracker.apply({ type: "inflight", operation: "remove", requests: [{ model: "A", id: "2" }] });
-  assert.equal(tracker.count("A"), 0);
-  tracker.apply({ type: "inflight", operation: "remove", requests: [{ model: "A", id: "9" }] });
+  assert.equal(tracker.count("B"), 1);
+  tracker.apply({ type: "inflight", operation: "remove", id: "1" });
   assert.equal(tracker.count("A"), 0);
+  assert.equal(tracker.count("B"), 1);
+  tracker.apply({ type: "inflight", operation: "remove", id: "999" });
+  assert.equal(tracker.count("B"), 1);
+});
+
+test("snapshot replaces prior in-flight state", () => {
+  const tracker = new InflightTracker();
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }] });
+  tracker.apply({ type: "inflight", operation: "snapshot", requests: [{ model: "A", id: "2" }] });
+  assert.equal(tracker.count("A"), 1);
+  assert.equal(tracker.count("B"), 0);
 });
 
 test("modelStatus normalizes states", () => {