diff --git a/webapp/src/App.tsx b/webapp/src/App.tsx
index d7583b4..a6e019c 100644
--- a/webapp/src/App.tsx
+++ b/webapp/src/App.tsx
@@ -14,6 +14,7 @@ export default function App() {
   const [buckets, setBuckets] = useState<TimelineBucket[]>([])
   const [range, setRange] = useState<TimeRange | null>(null)
   const [filter, setFilter] = useState('')
+  const [filterError, setFilterError] = useState<string | null>(null)
 
   useEffect(() => {
     let cancelled = false
@@ -22,16 +23,19 @@ export default function App() {
       try {
         const [nextStats, nextBuckets, nextLogs] = await Promise.all([
           fetchStats(),
-          fetchTimeline({ startMs: range?.startMs, endMs: range?.endMs }),
-          fetchLogs({ startMs: range?.startMs, endMs: range?.endMs, limit: 1000 }),
+          fetchTimeline({ startMs: range?.startMs, endMs: range?.endMs, filter: filter || undefined }),
+          fetchLogs({ startMs: range?.startMs, endMs: range?.endMs, limit: 1000, filter: filter || undefined }),
         ])
         if (!cancelled) {
           setStats(nextStats)
           setBuckets(nextBuckets)
           setLogs(nextLogs)
+          setFilterError(null)
+        }
+      } catch (err) {
+        if (!cancelled) {
+          setFilterError(err instanceof Error ? err.message : String(err))
         }
-      } catch {
-        // engine not reachable yet; retry on next tick
       }
     }
 
@@ -41,17 +45,15 @@ export default function App() {
       cancelled = true
       clearInterval(id)
     }
-  }, [range])
-
-  const visibleLogs = filter ? logs.filter((l) => l.text.includes(filter)) : logs
+  }, [range, filter])
 
   return (
     <div className="flex h-screen w-screen overflow-hidden">
       <NavMenu stats={stats} />
       <div className="flex min-w-0 flex-1 flex-col">
-        <FilterBar value={filter} onChange={setFilter} />
+        <FilterBar value={filter} onChange={setFilter} error={filterError} />
         <LogTimeline buckets={buckets} range={range} onSelectRange={setRange} />
-        <LogPreview logs={visibleLogs} />
+        <LogPreview logs={logs} />
         <ComingSoon title="Metrics" />
         <ComingSoon title="Dashboards" />
       </div>
diff --git a/webapp/src/components/FilterBar.tsx b/webapp/src/components/FilterBar.tsx
index 920a403..43c266d 100644
--- a/webapp/src/components/FilterBar.tsx
+++ b/webapp/src/components/FilterBar.tsx
@@ -1,32 +1,46 @@
 import { useState } from 'react'
 
 /**
- * Placeholder for the syntax-aware pest-parsed filter language described in the
- * README. For now this only does a plain substring match, applied client-side.
+ * Input for the syntax-aware pest-parsed filter language described in the
+ * README (regex + metric comparisons combined with `and`/`or`). The raw
+ * filter string is sent to the server (`GET /api/logs` / `GET /api/timeline`
+ * `filter` param) and evaluated there; this component just manages the
+ * draft text and surfaces any parse error the server reports back.
  */
-export function FilterBar({ value, onChange }: { value: string; onChange: (value: string) => void }) {
+export function FilterBar({
+  value,
+  onChange,
+  error,
+}: {
+  value: string
+  onChange: (value: string) => void
+  error?: string | null
+}) {
   const [draft, setDraft] = useState(value)
 
   return (
     <form
-      className="flex items-center gap-2 border-b border-neutral-800 px-3 py-2"
+      className="flex flex-col gap-1 border-b border-neutral-800 px-3 py-2"
       onSubmit={(e) => {
         e.preventDefault()
         onChange(draft)
       }}
     >
-      <input
-        className="flex-1 rounded border border-neutral-700 bg-neutral-900 px-2 py-1 text-sm text-neutral-100 placeholder:text-neutral-500 focus:border-neutral-500 focus:outline-none"
-        placeholder='regex("error") and sequence<5 or timestamp>12:00'
-        value={draft}
-        onChange={(e) => setDraft(e.target.value)}
-      />
-      <button
-        type="submit"
-        className="rounded border border-neutral-700 px-3 py-1 text-sm text-neutral-300 hover:bg-neutral-800"
-      >
-        Filter
-      </button>
+      <div className="flex items-center gap-2">
+        <input
+          className="flex-1 rounded border border-neutral-700 bg-neutral-900 px-2 py-1 text-sm text-neutral-100 placeholder:text-neutral-500 focus:border-neutral-500 focus:outline-none"
+          placeholder='regex("error") and sequence<5 or timestamp>12:00'
+          value={draft}
+          onChange={(e) => setDraft(e.target.value)}
+        />
+        <button
+          type="submit"
+          className="rounded border border-neutral-700 px-3 py-1 text-sm text-neutral-300 hover:bg-neutral-800"
+        >
+          Filter
+        </button>
+      </div>
+      {error && <p className="text-xs text-red-500">{error}</p>}
     </form>
   )
 }
diff --git a/webapp/src/lib/api.ts b/webapp/src/lib/api.ts
index bc44d95..eddaf5f 100644
--- a/webapp/src/lib/api.ts
+++ b/webapp/src/lib/api.ts
@@ -46,7 +46,16 @@ export interface Stats {
 async function getJson<T>(path: string): Promise<T> {
   const res = await fetch(path)
   if (!res.ok) {
-    throw new Error(`${path} failed: ${res.status}`)
+    let message = `${path} failed: ${res.status}`
+    try {
+      const body: unknown = await res.json()
+      if (body && typeof body === 'object' && 'error' in body && typeof (body as { error: unknown }).error === 'string') {
+        message = (body as { error: string }).error
+      }
+    } catch {
+      // body wasn't JSON (or had no `error` field) — fall back to the generic message
+    }
+    throw new Error(message)
   }
   return res.json() as Promise<T>
 }
@@ -56,12 +65,14 @@ export function fetchLogs(params: {
   startMs?: number
   endMs?: number
   limit?: number
+  filter?: string
 }): Promise<LogEntry[]> {
   const search = new URLSearchParams()
   if (params.sinceSequence !== undefined) search.set('since_sequence', String(params.sinceSequence))
   if (params.startMs !== undefined) search.set('start_ms', String(params.startMs))
   if (params.endMs !== undefined) search.set('end_ms', String(params.endMs))
   if (params.limit !== undefined) search.set('limit', String(params.limit))
+  if (params.filter) search.set('filter', params.filter)
   return getJson(`/api/logs?${search.toString()}`)
 }
 
@@ -69,11 +80,13 @@ export function fetchTimeline(params: {
   startMs?: number
   endMs?: number
   bucketMs?: number
+  filter?: string
 }): Promise<TimelineBucket[]> {
   const search = new URLSearchParams()
   if (params.startMs !== undefined) search.set('start_ms', String(params.startMs))
   if (params.endMs !== undefined) search.set('end_ms', String(params.endMs))
   if (params.bucketMs !== undefined) search.set('bucket_ms', String(params.bucketMs))
+  if (params.filter) search.set('filter', params.filter)
   return getJson(`/api/timeline?${search.toString()}`)
 }