diff --git a/packages/cli/src/lib/response-cache.ts b/packages/cli/src/lib/response-cache.ts
index 6019c1e62..2ada16ce9 100644
--- a/packages/cli/src/lib/response-cache.ts
+++ b/packages/cli/src/lib/response-cache.ts
@@ -45,16 +45,21 @@ const log = logger.withTag("response-cache");
 /**
  * TTL tier classification for URLs.
  *
- * - `immutable`: data that never changes once created (events, traces)
- * - `stable`: data that changes infrequently (orgs, projects, teams)
- * - `volatile`: data that changes often (issue lists, log lists)
+ * - `stable`: data that changes infrequently (orgs, projects, teams,
+ *   organization event details, trace-item details)
+ * - `volatile`: data that changes often (issues and their events, project
+ *   event details, full traces, log and span queries)
  * - `no-cache`: never cache (polling endpoints like autofix state)
+ *
+ * No tier treats a response as immutable. Event payloads embed mutable
+ * fields (`nextEventID`, user reports, release data), `latest`/`oldest`/
+ * `recommended` resolve to different events over time, and traces gain
+ * spans as they arrive (getsentry/sentry#128818).
  */
-type TtlTier = "immutable" | "stable" | "volatile" | "no-cache";
+type TtlTier = "stable" | "volatile" | "no-cache";
 
 /** Fallback TTL durations by tier (milliseconds). `no-cache` uses 0 as a sentinel. */
 const FALLBACK_TTL_MS: Record<TtlTier, number> = {
-  immutable: 24 * 60 * 60 * 1000, // 24 hours — events and traces never change
   stable: 5 * 60 * 1000, // 5 minutes
   volatile: 60 * 1000, // 60 seconds
   "no-cache": 0,
@@ -63,30 +68,35 @@ const FALLBACK_TTL_MS: Record<TtlTier, number> = {
 /**
  * URL patterns grouped by TTL tier.
  *
- * Checked in tier priority order (no-cache → immutable → volatile).
+ * Checked in tier priority order (no-cache → volatile).
  * "stable" has no patterns — it is the default fallback when nothing else matches.
+ *
+ * TODO: Classify by generated operation metadata from `@sentry/api` instead
+ * of URL regexes, once it ships per-operation metadata
+ * (getsentry/sentry-api-schema#81) and a route-keyed operation map
+ * (getsentry/sentry-api-schema#102).
  */
 const URL_TIER_REGEXPS: Readonly<Record<TtlTier, readonly RegExp[]>> = {
   // Polling endpoints where state changes rapidly
   "no-cache": [/\/(?:autofix|root-cause)\//],
-  // Specific resources by ID (events, traces, span details) — never change once created
-  immutable: [
-    /\/events\/[^/?]+\/?(?:\?|$)/,
+  volatile: [
+    // Issue endpoints: lists, detail views, and issue events such as
+    // `/issues/{id}/events/latest/`
+    /\/issues\//,
+    /[?&]dataset=(?:logs|spans)/,
+    /\/trace-logs\//,
+    // Full traces gain spans as they arrive
     /\/trace\/[0-9a-f]{32}\//,
-    /\/trace-items\/[0-9a-f]+\//,
+    // Project event details embed `nextEventID`/`previousEventID` and user
+    // reports, and reprocessing can change them for the same ID
+    /\/projects\/[^/]+\/[^/]+\/events\/[^/?]+\/?(?:\?|$)/,
   ],
-  // Issue endpoints (lists AND detail views), dataset queries, trace-logs
-  volatile: [/\/issues\//, /[?&]dataset=(?:logs|spans)/, /\/trace-logs\//],
   // Default fallback — no patterns needed
   stable: [],
 };
 
 /** Tier check order — stable is the default and has no patterns to check. */
-const TIER_CHECK_ORDER: readonly TtlTier[] = [
-  "no-cache",
-  "immutable",
-  "volatile",
-];
+const TIER_CHECK_ORDER: readonly TtlTier[] = ["no-cache", "volatile"];
 
 /**
  * Classify a URL into a TTL tier for fallback caching.
@@ -189,7 +199,6 @@ type CacheEntry = {
 const POLICY_OPTIONS: CachePolicy.Options = {
   shared: false,
   cacheHeuristic: 0.1,
-  immutableMinTimeToLive: FALLBACK_TTL_MS.immutable,
 };
 
 /** Maximum number of cache files to retain */
diff --git a/packages/cli/test/lib/response-cache.property.test.ts b/packages/cli/test/lib/response-cache.property.test.ts
index 6f605c63c..c649b35a4 100644
--- a/packages/cli/test/lib/response-cache.property.test.ts
+++ b/packages/cli/test/lib/response-cache.property.test.ts
@@ -164,32 +164,44 @@ describe("property: classifyUrl", () => {
     fcAssert(
       property(sentryUrlArb, (url) => {
         const tier = classifyUrl(url);
-        expect(["immutable", "stable", "volatile", "no-cache"]).toContain(tier);
+        expect(["stable", "volatile", "no-cache"]).toContain(tier);
       }),
       { numRuns: DEFAULT_NUM_RUNS },
     );
   });
 
-  test("event detail URLs are immutable", () => {
+  test("organization event and trace-item details are stable", () => {
+    const urls = [
+      "https://us.sentry.io/api/0/organizations/myorg/events/myproject:abc123/",
+      "https://sentry.io/api/0/organizations/org/events/42:deadbeef/?field=title",
+      "https://us.sentry.io/api/0/projects/org/proj/trace-items/a1b2c3d4e5f67890/?trace_id=abc&item_type=spans",
+    ];
+    for (const url of urls) {
+      expect(classifyUrl(url)).toBe("stable");
+    }
+  });
+
+  test("project event details are volatile", () => {
     const urls = [
       "https://us.sentry.io/api/0/projects/myorg/myproject/events/abc123/",
       "https://sentry.io/api/0/projects/org/proj/events/deadbeef/?full=true",
     ];
     for (const url of urls) {
-      expect(classifyUrl(url)).toBe("immutable");
+      expect(classifyUrl(url)).toBe("volatile");
     }
   });
 
-  test("trace URLs with 32-char hex IDs are immutable", () => {
-    const traceId = "a".repeat(32);
-    const url = `https://us.sentry.io/api/0/organizations/myorg/trace/${traceId}/`;
-    expect(classifyUrl(url)).toBe("immutable");
+  test("issue events are volatile, including latest/oldest/recommended", () => {
+    for (const eventId of ["latest", "oldest", "recommended", "deadbeef"]) {
+      const url = `https://us.sentry.io/api/0/organizations/org/issues/123/events/${eventId}/`;
+      expect(classifyUrl(url)).toBe("volatile");
+    }
   });
 
-  test("trace-items (span detail) URLs are immutable", () => {
-    const url =
-      "https://us.sentry.io/api/0/projects/org/proj/trace-items/a1b2c3d4e5f67890/?trace_id=abc&item_type=spans";
-    expect(classifyUrl(url)).toBe("immutable");
+  test("full trace URLs with 32-char hex IDs are volatile", () => {
+    const traceId = "a".repeat(32);
+    const url = `https://us.sentry.io/api/0/organizations/myorg/trace/${traceId}/?limit=100`;
+    expect(classifyUrl(url)).toBe("volatile");
   });
 
   test("issue URLs are volatile (lists and detail views)", () => {
diff --git a/packages/cli/test/lib/response-cache.test.ts b/packages/cli/test/lib/response-cache.test.ts
index 24c0a8369..23022c861 100644
--- a/packages/cli/test/lib/response-cache.test.ts
+++ b/packages/cli/test/lib/response-cache.test.ts
@@ -7,7 +7,7 @@
 
 import { readdir } from "node:fs/promises";
 import { join } from "node:path";
-import { afterEach, beforeEach, describe, expect, test } from "vitest";
+import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 import { setAuthToken } from "../../src/lib/db/auth.js";
 import {
   buildCacheKey,
@@ -452,6 +452,67 @@ describe("no-cache tier", () => {
   });
 });
 
+// ---------------------------------------------------------------------------
+// Fallback TTL tiers
+// ---------------------------------------------------------------------------
+
+describe("fallback TTL tiers", () => {
+  const MINUTE = 60 * 1000;
+
+  beforeEach(() => {
+    vi.useFakeTimers({ toFake: ["Date"] });
+    vi.setSystemTime(new Date("2026-01-01T00:00:00Z"));
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  async function isCachedAfter(url: string, elapsedMs: number) {
+    await storeCachedResponse(TEST_METHOD, url, {}, mockResponse(TEST_BODY));
+    vi.setSystemTime(Date.now() + elapsedMs);
+    return (await getCachedResponse(TEST_METHOD, url, {})) !== undefined;
+  }
+
+  test("organization event details are reused for up to 5 minutes", async () => {
+    const url =
+      "https://us.sentry.io/api/0/organizations/myorg/events/proj:abc123/";
+    expect(await isCachedAfter(url, 4 * MINUTE)).toBe(true);
+    vi.setSystemTime(Date.now() + 2 * MINUTE);
+    expect(await getCachedResponse(TEST_METHOD, url, {})).toBeUndefined();
+  });
+
+  test("an issue's latest event expires after 60 seconds", async () => {
+    const url =
+      "https://us.sentry.io/api/0/organizations/myorg/issues/123/events/latest/";
+    expect(await isCachedAfter(url, 2 * MINUTE)).toBe(false);
+  });
+
+  test("project event details expire after 60 seconds", async () => {
+    const url =
+      "https://us.sentry.io/api/0/projects/myorg/myproject/events/abc123/";
+    expect(await isCachedAfter(url, 2 * MINUTE)).toBe(false);
+  });
+
+  test("full traces expire after 60 seconds", async () => {
+    const url = `https://us.sentry.io/api/0/organizations/myorg/trace/${"a".repeat(32)}/`;
+    expect(await isCachedAfter(url, 2 * MINUTE)).toBe(false);
+  });
+
+  test("server max-age still wins over the fallback tier", async () => {
+    const url =
+      "https://us.sentry.io/api/0/organizations/myorg/issues/123/events/latest/";
+    await storeCachedResponse(
+      TEST_METHOD,
+      url,
+      {},
+      mockResponse(TEST_BODY, 200, { "cache-control": "private, max-age=300" }),
+    );
+    vi.setSystemTime(Date.now() + 4 * MINUTE);
+    expect(await getCachedResponse(TEST_METHOD, url, {})).toBeDefined();
+  });
+});
+
 // ---------------------------------------------------------------------------
 // File structure
 // ---------------------------------------------------------------------------