diff --git a/apps/server/src/usage/UsageService.test.ts b/apps/server/src/usage/UsageService.test.ts
index cb9270a7ed3b9570ef3b075b54e0126332e08bb2..393437fcc37b1b7c6a8a84e422827b5769f0eb2b 100644
--- a/apps/server/src/usage/UsageService.test.ts
+++ b/apps/server/src/usage/UsageService.test.ts
@@ -996,6 +996,34 @@ describe("UsageService", () => {
       }).pipe(Effect.scoped),
   );
 
+  it.live.skipIf(HostProcess.Platform.defaultValue() === "win32" || process.getuid?.() === 0)(
+    "reports unreadable transcripts as partial and recovers once they can be read",
+    () =>
+      Effect.gen(function* () {
+        const { transcript, settings, home } = yield* setup;
+        const unreadable = NodePath.join(NodePath.dirname(transcript), "other.jsonl");
+        yield* Effect.promise(async () => {
+          await NodeFSP.writeFile(transcript, claudeLine(1, 5));
+          await NodeFSP.writeFile(unreadable, claudeLine(2, 7));
+          await NodeFSP.chmod(unreadable, 0);
+        });
+        yield* Effect.gen(function* () {
+          const service = yield* UsageService.make;
+          const partial = yield* service.readSummary(WINDOW);
+          assert.strictEqual(totalOutputTokens(partial), 5);
+          assert.strictEqual(partial.sources[0]?.status, "partial");
+
+          yield* Effect.promise(() => NodeFSP.chmod(unreadable, 0o600));
+          const healthy = yield* service.readSummary(WINDOW);
+          assert.strictEqual(totalOutputTokens(healthy), 12);
+          assert.strictEqual(healthy.sources[0]?.status, "ok");
+          assert.isNull(healthy.sources[0]?.message);
+        }).pipe(
+          Effect.provide(layerService({ prefix: "usage-service-unreadable", home, settings })),
+        );
+      }).pipe(Effect.scoped),
+  );
+
   it.live("reprices unchanged transcripts when custom prices are added, edited, or removed", () =>
     Effect.gen(function* () {
       const { transcript, settings, home } = yield* setup;
diff --git a/apps/server/src/usage/UsageService.ts b/apps/server/src/usage/UsageService.ts
index 3b496d8f4498b34ff9c3c7f94e438fec231dc346..2259c1d9f7730f98ce8fb4cd5664fe4bd75608fb 100644
--- a/apps/server/src/usage/UsageService.ts
+++ b/apps/server/src/usage/UsageService.ts
@@ -519,6 +519,7 @@ export const make = Effect.gen(function* () {
     format: TranscriptUsageFormat<unknown>,
   ): Effect.Effect<{
     readonly records: readonly UsageRecord[];
+    readonly failed?: true;
     readonly update?: { readonly entry: CachedFile; readonly replaces: CachedFile | undefined };
   }> =>
     Effect.gen(function* () {
@@ -554,6 +555,7 @@ export const make = Effect.gen(function* () {
       if (parsed === null)
         return {
           records: cached?.provider === provider ? [...cached.records, ...cached.tailRecords] : [],
+          failed: true,
         };
 
       // Stored already de-duplicated within the file, which is 99% of all
@@ -600,7 +602,7 @@ export const make = Effect.gen(function* () {
       .exists(dir)
       .pipe(Effect.catchCause(() => Effect.succeed(false)));
     if (!exists) return { provider, dir, volumeId, files: null } satisfies ScannedDir;
-    const files = yield* Effect.promise(() =>
+    const { files, failedPaths } = yield* Effect.promise(() =>
       listTranscriptFiles(dir, windowStartMs, fileName === undefined ? undefined : { fileName }),
     );
     // A cold parse waits on disk reads, so a few files in flight read
@@ -629,7 +631,20 @@ export const make = Effect.gen(function* () {
       }
       return { path, records };
     });
-    return { provider, dir, volumeId, files: parsedFiles } satisfies ScannedDir;
+    // Unread files keep their cached usage, but the total may be short.
+    const unread = failedPaths + read.filter((file) => file.failed).length;
+    return {
+      provider,
+      dir,
+      volumeId,
+      files: parsedFiles,
+      ...(unread > 0
+        ? {
+            status: "partial",
+            message: `${unread} transcript path(s) could not be read; usage may be incomplete.`,
+          }
+        : {}),
+    } satisfies ScannedDir;
   });
 
   const collectDirs = Effect.fn("UsageService.collectDirs")(function* (
diff --git a/apps/server/src/usage/usageTranscriptReader.ts b/apps/server/src/usage/usageTranscriptReader.ts
index 16684e3a85abd5476bf4f125f81fe7aa3115e7e5..dbf0fd7aeb35f80718071ee8fecfc611f9daaba2 100644
--- a/apps/server/src/usage/usageTranscriptReader.ts
+++ b/apps/server/src/usage/usageTranscriptReader.ts
@@ -109,9 +109,9 @@ function fnv1a(buffer: Buffer): number {
 /**
  * Lists `.jsonl` transcripts under `root` last modified at or after `sinceMs`.
  *
- * Errors on individual entries are swallowed: session files rotate and get
- * removed while the walk is in flight, and a partial listing is far better than
- * failing the page.
+ * Unreadable directories and files are counted in `failedPaths` rather than
+ * failing the page, so the source can report incomplete usage. Files that
+ * vanish between `readdir` and `stat` are ordinary rotation and not counted.
  *
  * `fileName` restricts the walk to a single basename (Grok's `updates.jsonl`).
  * Grok sessions also ship multi-megabyte `chat_history` and `events` logs that
@@ -126,14 +126,16 @@ export async function listTranscriptFiles(
   root: string,
   sinceMs: number,
   options?: { readonly fileName?: string },
-): Promise<readonly TranscriptFile[]> {
+): Promise<{ readonly files: readonly TranscriptFile[]; readonly failedPaths: number }> {
   const fileName = options?.fileName;
   const candidates: string[] = [];
+  let failedPaths = 0;
   const walk = async (dir: string): Promise<void> => {
     let entries;
     try {
       entries = await NodeFSP.readdir(dir, { withFileTypes: true });
     } catch {
+      failedPaths += 1;
       return;
     }
     for (const entry of entries) {
@@ -156,15 +158,17 @@ export async function listTranscriptFiles(
         if (stats.mtimeMs >= sinceMs) {
           found[index] = { path, size: stats.size, mtimeMs: stats.mtimeMs };
         }
-      } catch {
-        // Vanished between readdir and stat.
+      } catch (error) {
+        if (!(error instanceof Error && "code" in error && error.code === "ENOENT")) {
+          failedPaths += 1;
+        }
       }
     }
   };
   await Promise.all(
     Array.from({ length: Math.min(STAT_CONCURRENCY, candidates.length) }, statQueued),
   );
-  return found.filter((file) => file !== undefined);
+  return { files: found.filter((file) => file !== undefined), failedPaths };
 }
 
 /**