diff --git a/tests/timeline-filter.test.ts b/tests/timeline-filter.test.ts
new file mode 100644
index 0000000..8898525
--- /dev/null
+++ b/tests/timeline-filter.test.ts
@@ -0,0 +1,52 @@
+import { describe, expect, it } from "vitest";
+import type { Call } from "../ui/src/api.js";
+import { callLabel, filterTimelineCalls } from "../ui/src/timeline-filter.js";
+
+const call = (overrides: Partial<Call>): Call => ({
+  id: overrides.id ?? "1",
+  method: overrides.method ?? "tools/call",
+  request: overrides.request ?? {},
+  isError: overrides.isError ?? false,
+  startTs: overrides.startTs ?? 1,
+  requestTokens: overrides.requestTokens ?? 0,
+  responseTokens: overrides.responseTokens ?? 0,
+  ...overrides,
+});
+
+describe("filterTimelineCalls", () => {
+  const calls = [
+    call({ id: "1", toolName: "github_search", method: "tools/call" }),
+    call({ id: "2", method: "resources/read", isError: true }),
+    call({ id: "3", toolName: "filesystem_write", method: "tools/call", isError: true }),
+  ];
+
+  it("matches tool or method names case-insensitively", () => {
+    expect(filterTimelineCalls(calls, "GITHUB", false).map((entry) => entry.id)).toEqual(["1"]);
+    expect(filterTimelineCalls(calls, "resources", false).map((entry) => entry.id)).toEqual(["2"]);
+    expect(filterTimelineCalls(calls, "tools/call", false).map((entry) => entry.id)).toEqual([
+      "1",
+      "3",
+    ]);
+    expect(
+      filterTimelineCalls(
+        [call({ id: "4", toolName: "", method: "resources/list" })],
+        "resources",
+        false,
+      ).map((entry) => entry.id),
+    ).toEqual(["4"]);
+  });
+
+  it("can show only errored calls", () => {
+    expect(filterTimelineCalls(calls, "", true).map((entry) => entry.id)).toEqual(["2", "3"]);
+  });
+
+  it("combines search and errors-only filters", () => {
+    expect(filterTimelineCalls(calls, "filesystem", true).map((entry) => entry.id)).toEqual(["3"]);
+  });
+});
+
+describe("callLabel", () => {
+  it("falls back to method for empty tool names", () => {
+    expect(callLabel(call({ toolName: "", method: "tools/call" }))).toBe("tools/call");
+  });
+});
diff --git a/ui/src/api.ts b/ui/src/api.ts
index d7e0fd3..952a287 100644
--- a/ui/src/api.ts
+++ b/ui/src/api.ts
@@ -37,11 +37,13 @@ export interface SessionDetail {
   totalTokens: number;
 }
 
+const readJson = <T>(response: Response): Promise<T> => response.json() as Promise<T>;
+
 export const fetchSessions = (): Promise<SessionInfo[]> =>
-  fetch("/api/sessions").then((r) => r.json());
+  fetch("/api/sessions").then(readJson<SessionInfo[]>);
 
 export const fetchSession = (file: string): Promise<SessionDetail> =>
-  fetch(`/api/session?file=${encodeURIComponent(file)}`).then((r) => r.json());
+  fetch(`/api/session?file=${encodeURIComponent(file)}`).then(readJson<SessionDetail>);
 
 export interface ReplayResponse {
   original: unknown;
@@ -57,7 +59,7 @@ export const postReplay = (
     method: "POST",
     headers: { "content-type": "application/json" },
     body: JSON.stringify({ file, id, startTs }),
-  }).then((r) => r.json());
+  }).then(readJson<ReplayResponse>);
 
 export function subscribeLive(onChange: (file: string) => void): () => void {
   const source = new EventSource("/api/live");
diff --git a/ui/src/app.tsx b/ui/src/app.tsx
index d289ac3..5a89b2a 100644
--- a/ui/src/app.tsx
+++ b/ui/src/app.tsx
@@ -9,6 +9,7 @@ import {
   type SessionInfo,
   subscribeLive,
 } from "./api.js";
+import { callLabel, filterTimelineCalls } from "./timeline-filter.js";
 
 const time = (ts: number) => new Date(ts).toLocaleTimeString();
 const day = (ts: number) => new Date(ts).toLocaleDateString();
@@ -18,6 +19,8 @@ export function App() {
   const [selected, setSelected] = useState<string | null>(null);
   const [detail, setDetail] = useState<SessionDetail | null>(null);
   const [call, setCall] = useState<Call | null>(null);
+  const [timelineQuery, setTimelineQuery] = useState("");
+  const [errorsOnly, setErrorsOnly] = useState(false);
 
   useEffect(() => {
     fetchSessions().then((list) => {
@@ -42,6 +45,10 @@ export function App() {
   }, [selected]);
 
   const errorCount = useMemo(() => detail?.calls.filter((c) => c.isError).length ?? 0, [detail]);
+  const filteredCalls = useMemo(
+    () => (detail ? filterTimelineCalls(detail.calls, timelineQuery, errorsOnly) : []),
+    [detail, errorsOnly, timelineQuery],
+  );
 
   return (
     <div class="layout">
@@ -115,6 +122,23 @@ export function App() {
 
             <div class="section-gap" />
             <h2>Timeline</h2>
+            <div class="timeline-controls">
+              <input
+                aria-label="Filter timeline calls"
+                type="search"
+                placeholder="filter by tool or method"
+                value={timelineQuery}
+                onInput={(event) => setTimelineQuery(event.currentTarget.value)}
+              />
+              <label>
+                <input
+                  type="checkbox"
+                  checked={errorsOnly}
+                  onChange={(event) => setErrorsOnly(event.currentTarget.checked)}
+                />
+                errors only
+              </label>
+            </div>
             <table>
               <thead>
                 <tr>
@@ -125,7 +149,7 @@ export function App() {
                 </tr>
               </thead>
               <tbody>
-                {detail.calls.map((c) => (
+                {filteredCalls.map((c) => (
                   <tr
                     key={`${c.startTs}-${String(c.id)}`}
                     class={`call ${call === c ? "selected" : ""}`}
@@ -133,13 +157,20 @@ export function App() {
                   >
                     <td>
                       <span class={`status ${c.isError ? "err" : c.response ? "" : "pending"}`} />
-                      {c.toolName ?? c.method}
+                      {callLabel(c)}
                     </td>
                     <td class="num">{time(c.startTs)}</td>
                     <td class="num">{c.latencyMs === undefined ? "…" : `${c.latencyMs}ms`}</td>
                     <td class="num">{(c.requestTokens + c.responseTokens).toLocaleString()}</td>
                   </tr>
                 ))}
+                {!filteredCalls.length && (
+                  <tr>
+                    <td class="empty-row" colSpan={4}>
+                      no matching calls
+                    </td>
+                  </tr>
+                )}
               </tbody>
             </table>
           </>
@@ -182,7 +213,7 @@ function CallDetail({ call, file, onClose }: { call: Call; file: string; onClose
       <button type="button" class="close" onClick={onClose}>
         ×
       </button>
-      <h3>{call.toolName ?? call.method}</h3>
+      <h3>{callLabel(call)}</h3>
       <div class="meta">
         {call.isError ? "❌ error" : call.response ? "✓ ok" : "⏳ no response captured"}
         {call.latencyMs !== undefined && ` · ${call.latencyMs}ms`}
diff --git a/ui/src/style.css b/ui/src/style.css
index bbaa2e2..07672ef 100644
--- a/ui/src/style.css
+++ b/ui/src/style.css
@@ -215,6 +215,46 @@ tr.selected td {
   background: var(--warn);
 }
 
+.timeline-controls {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  margin: 0 0 8px;
+}
+
+.timeline-controls input[type="search"] {
+  min-width: 240px;
+  max-width: 360px;
+  flex: 1;
+  background: var(--bg-panel);
+  color: var(--text);
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  padding: 7px 10px;
+  font: inherit;
+}
+
+.timeline-controls input[type="search"]:focus {
+  outline: 1px solid var(--accent-dim);
+  border-color: var(--accent-dim);
+}
+
+.timeline-controls label {
+  display: inline-flex;
+  align-items: center;
+  gap: 6px;
+  color: var(--text-dim);
+  font-size: 12px;
+  white-space: nowrap;
+}
+
+.empty-row {
+  color: var(--text-dim);
+  font-family: var(--sans);
+  text-align: center;
+  padding: 18px 10px;
+}
+
 .detail {
   position: fixed;
   right: 0;
diff --git a/ui/src/timeline-filter.ts b/ui/src/timeline-filter.ts
new file mode 100644
index 0000000..515f4a8
--- /dev/null
+++ b/ui/src/timeline-filter.ts
@@ -0,0 +1,24 @@
+import type { Call } from "./api.js";
+
+const hasText = (value: string | undefined): value is string => Boolean(value?.trim());
+
+export function callLabel(call: Call): string {
+  return hasText(call.toolName) ? call.toolName : call.method;
+}
+
+function callSearchText(call: Call): string {
+  return [call.toolName, call.method].filter(hasText).join(" ").toLowerCase();
+}
+
+export function filterTimelineCalls(calls: Call[], query: string, errorsOnly: boolean): Call[] {
+  const normalizedQuery = query.trim().toLowerCase();
+  return calls.filter((call) => {
+    if (errorsOnly && !call.isError) {
+      return false;
+    }
+    if (!normalizedQuery) {
+      return true;
+    }
+    return callSearchText(call).includes(normalizedQuery);
+  });
+}