diff --git a/frontend/src/app/pages/AgentChat/ChatInput/hooks/useContextFiles.ts b/frontend/src/app/pages/AgentChat/ChatInput/hooks/useContextFiles.ts
index d8d6c06e..28f76581 100644
--- a/frontend/src/app/pages/AgentChat/ChatInput/hooks/useContextFiles.ts
+++ b/frontend/src/app/pages/AgentChat/ChatInput/hooks/useContextFiles.ts
@@ -4,15 +4,16 @@ import { API_BASE, getAuthToken } from '@/shared/config';
 import { ForcedToolGroup } from '../types';
 import { basename } from '../helpers';
 
-// Only auto-shrink a file when it would eat 85%+ of the window on its own. Below
-// that, send it NATIVELY to the model (base64 document block) the way claude.ai /
+// Only auto-shrink a file when it literally won't fit (98%+ of the window on its
+// own). Below that, send it NATIVELY (base64 document block) the way claude.ai /
 // OpenAI / Gemini do — the model reads the PDF server-side, instantly, no separate
 // summarize round-trip. The old 50% trigger was force-summarizing files that fit
 // fine, which is the entire reason our file flow felt 60s-slow vs their instant: we
-// were doing pre-processing work the big providers simply don't do. Leaves ~15% for
-// the conversation; if it grows past the window later, auto-compact handles it.
+// were doing pre-processing work the big providers simply don't do. 98% (not 100%)
+// leaves a sliver for the prompt itself so a barely-fitting file doesn't 4xx; if the
+// conversation later grows past the window, auto-compact handles it.
 function shrinkThreshold(modelCtx: number): number {
-  return Math.floor(modelCtx * 0.85);
+  return Math.floor(modelCtx * 0.98);
 }
 
 export type SendBlock = null | {
diff --git a/frontend/src/app/pages/AgentChat/ChatInput/toolbar/ContextRing.tsx b/frontend/src/app/pages/AgentChat/ChatInput/toolbar/ContextRing.tsx
index 0eea0bda..1274b78e 100644
--- a/frontend/src/app/pages/AgentChat/ChatInput/toolbar/ContextRing.tsx
+++ b/frontend/src/app/pages/AgentChat/ChatInput/toolbar/ContextRing.tsx
@@ -4,6 +4,21 @@ import Tooltip from '@mui/material/Tooltip';
 import { formatTokenCount } from '../helpers';
 
 export const ContextRing: React.FC<{ used: number; limit: number; accentColor: string; trackColor: string }> = ({ used, limit, accentColor, trackColor }) => {
+  // Track the previous fill so a DROP (compaction freed space) can play a brief
+  // "settle" cue: the ring eases down AND flashes once toward the track color,
+  // signaling "we just made room" without a loud banner. A rise just eases up.
+  const prevUsed = React.useRef(used);
+  const [justCompacted, setJustCompacted] = React.useState(false);
+  React.useEffect(() => {
+    if (used < prevUsed.current - 1) {
+      setJustCompacted(true);
+      const t = setTimeout(() => setJustCompacted(false), 700);
+      prevUsed.current = used;
+      return () => clearTimeout(t);
+    }
+    prevUsed.current = used;
+  }, [used]);
+
   if (used === 0) return null;
   const pct = Math.min((used / limit) * 100, 100);
   const size = 20;
@@ -24,6 +39,12 @@ export const ContextRing: React.FC<{ used: number; limit: number; accentColor: s
             strokeDasharray={circumference} strokeDashoffset={dashOffset}
             strokeLinecap="round"
             transform={`rotate(-90 ${size / 2} ${size / 2})`}
+            style={{
+              // 600ms cubic-bezier ease on the fill: a rise glides up, a compaction
+              // glides down. The one-shot opacity dip is the "settle" flash on drop.
+              transition: 'stroke-dashoffset 0.6s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.35s ease',
+              opacity: justCompacted ? 0.35 : 1,
+            }}
           />
         </svg>
       </Box>
diff --git a/frontend/src/app/pages/AgentChat/shell/ContextDrawer.tsx b/frontend/src/app/pages/AgentChat/shell/ContextDrawer.tsx
index a6eeda15..1b49d684 100644
--- a/frontend/src/app/pages/AgentChat/shell/ContextDrawer.tsx
+++ b/frontend/src/app/pages/AgentChat/shell/ContextDrawer.tsx
@@ -53,7 +53,7 @@ export default function ContextDrawer() {
               {Math.round(ctxPct * 100)}%
             </Typography>
             <Typography variant="caption" sx={{ color: c.text.tertiary }}>
-              {(session.tokens?.input || 0).toLocaleString()} / 200K tokens
+              {(session.tokens?.input || 0).toLocaleString()} / {session.context_window ? `${Math.round(session.context_window / 1000)}K` : '200K'} tokens
             </Typography>
           </Box>
           <Box sx={{ p: 1.5, borderRadius: 1, border: `1px solid ${c.border.medium}` }}>
diff --git a/frontend/src/shared/state/agentsSlice.ts b/frontend/src/shared/state/agentsSlice.ts
index 5f104dcf..3bc0bb3e 100644
--- a/frontend/src/shared/state/agentsSlice.ts
+++ b/frontend/src/shared/state/agentsSlice.ts
@@ -744,13 +744,16 @@ const agentsSlice = createSlice({
       const session = state.sessions[action.payload.sessionId];
       if (!session) return;
       session.compacted_through_msg_id = action.payload.throughMsgId;
-      // The next preflight check looks at tokens.input to estimate "history used".
-      // After a compaction the real number is unknown until the next turn round-trips,
-      // but the OLD number is definitely wrong (it counts messages we just dropped).
-      // Zero it so preflight falls back to the char/4 estimate of remaining content,
-      // which is closer than holding the stale pre-compact value.
+      // After compaction the OLD context numbers are wrong (they count messages we
+      // just dropped). Reset EVERY context-derived field so all surfaces that show
+      // it — the toolbar ContextRing, the /context drawer %, the pre-send guard —
+      // reflect the post-compaction state, not just the token count. The real values
+      // refill on the next turn's round-trip; until then zero is closer than stale.
       if (action.payload.throughMsgId) {
         session.tokens = { input: 0, output: session.tokens?.output ?? 0 };
+        session.ctx_used_pct = 0;
+        session.cache_read_pct = 0;
+        session.cache_read_tokens = 0;
       }
     },