diff --git a/src/commands/explore.ts b/src/commands/explore.ts
index 6e401e8f3..b0610951c 100644
--- a/src/commands/explore.ts
+++ b/src/commands/explore.ts
@@ -42,6 +42,7 @@ import {
   getReplayRequestFields,
   isSupportedReplayField,
   listSupportedReplayFields,
+  normalizeVariadicFlag,
   parseReplayEnvironmentFilter,
 } from "../lib/replay-search.js";
 import { resolveOrgOptionalProjectFromArg } from "../lib/resolve-target.js";
@@ -375,10 +376,8 @@ function appendFlagHints(
   if (flags.limit !== DEFAULT_LIMIT) {
     parts.push(`--limit ${flags.limit}`);
   }
-  if (flags.environment && flags.environment.length > 0) {
-    for (const environment of flags.environment) {
-      parts.push(`-e "${environment}"`);
-    }
+  for (const environment of normalizeVariadicFlag(flags.environment)) {
+    parts.push(`-e "${environment}"`);
   }
   appendPeriodHint(parts, flags.period, DEFAULT_PERIOD);
   return parts.length > 0 ? `${base} ${parts.join(" ")}` : base;
@@ -710,11 +709,15 @@ export const exploreCommand = buildListCommand("explore", {
     );
 
     let dataset = flags.dataset;
-    const userSuppliedFields = flags.field && flags.field.length > 0;
-    let fieldList = [...defaultFieldsForDataset(dataset)];
-    if (userSuppliedFields) {
-      fieldList = flags.field;
-    }
+    // A single `-F` flag arrives from the parser as a bare string rather than a
+    // one-element array. Normalize once so every downstream consumer (fieldList,
+    // hintFlags, contextKey) sees an array — a leftover string makes the later
+    // `.filter`/`.join` calls throw a TypeError (CLI-28C).
+    const fields = normalizeVariadicFlag(flags.field);
+    const userSuppliedFields = fields.length > 0;
+    let fieldList = userSuppliedFields
+      ? [...fields]
+      : [...defaultFieldsForDataset(dataset)];
     const timeRange = flags.period;
     const environment = parseReplayEnvironmentFilter(flags.environment);
 
@@ -806,7 +809,7 @@ export const exploreCommand = buildListCommand("explore", {
     const hasMore = !!nextCursor;
 
     const baseTarget = project ? `${org}/${project}` : `${org}/`;
-    const hintFlags = { ...flags, dataset };
+    const hintFlags = { ...flags, dataset, field: fields };
     const nav = paginationHint({
       hasPrev,
       hasMore,
diff --git a/src/commands/replay/list.ts b/src/commands/replay/list.ts
index 22ff2aba4..7b3a7cb13 100644
--- a/src/commands/replay/list.ts
+++ b/src/commands/replay/list.ts
@@ -42,6 +42,7 @@ import {
 import { withProgress } from "../../lib/polling.js";
 import {
   getReplayUserLabel,
+  normalizeVariadicFlag,
   parseReplayEnvironmentFilter,
 } from "../../lib/replay-search.js";
 import { resolveOrgOptionalProjectFromArg } from "../../lib/resolve-target.js";
@@ -182,10 +183,8 @@ function appendReplayFlags(
   const parts: string[] = [];
   appendQueryHint(parts, flags.query);
   appendSortHint(parts, flags.sort, DEFAULT_SORT);
-  if (flags.environment && flags.environment.length > 0) {
-    for (const environment of flags.environment) {
-      parts.push(`-e "${environment}"`);
-    }
+  for (const environment of normalizeVariadicFlag(flags.environment)) {
+    parts.push(`-e "${environment}"`);
   }
   appendPeriodHint(parts, flags.period, DEFAULT_PERIOD);
   return parts.length > 0 ? `${base} ${parts.join(" ")}` : base;
diff --git a/src/lib/replay-search.ts b/src/lib/replay-search.ts
index 53b01305c..100df2f81 100644
--- a/src/lib/replay-search.ts
+++ b/src/lib/replay-search.ts
@@ -43,16 +43,31 @@ export const DEFAULT_REPLAY_EXPLORE_FIELDS = [
   "user.email",
 ] as const;
 
+/**
+ * Coerce a variadic CLI flag value into an array.
+ *
+ * Stricli's variadic parser yields a bare `string` for a single occurrence of
+ * a flag and a `string[]` for multiple, even though the flag is declared
+ * variadic. Callers must normalize before spreading or iterating, otherwise a
+ * single value is treated as an array of characters (CLI-28C).
+ */
+export function normalizeVariadicFlag(
+  value: readonly string[] | string | undefined
+): string[] {
+  if (value === undefined) {
+    return [];
+  }
+  return Array.isArray(value) ? [...value] : [value as string];
+}
+
 /** Parse repeatable and comma-separated replay environment filters. */
 export function parseReplayEnvironmentFilter(
-  values: readonly string[] | undefined
+  values: readonly string[] | string | undefined
 ): string[] | undefined {
-  const parsed = values
-    ? [...values]
-        .flatMap((value) => value.split(","))
-        .map((value) => value.trim())
-        .filter(Boolean)
-    : [];
+  const parsed = normalizeVariadicFlag(values)
+    .flatMap((value) => value.split(","))
+    .map((value) => value.trim())
+    .filter(Boolean);
 
   return parsed.length > 0 ? parsed : undefined;
 }
diff --git a/test/commands/explore.test.ts b/test/commands/explore.test.ts
index 5109f6f81..fdee8ab6d 100644
--- a/test/commands/explore.test.ts
+++ b/test/commands/explore.test.ts
@@ -321,6 +321,28 @@ describe("sentry explore", () => {
       );
     });
 
+    test("coerces a single -F flag (string) into an array without crashing", async () => {
+      // Stricli's variadic parser emits a bare string for a single `-F`, not a
+      // one-element array. The command must normalize it before the query and
+      // the pagination-hint path both use array methods on it (CLI-28C).
+      resolveTargetSpy.mockResolvedValue({ org: "test-org" });
+      const { context } = createContext();
+
+      await func.call(
+        context,
+        {
+          ...DEFAULT_FLAGS,
+          field: "transaction" as unknown as string[],
+        },
+        "test-org/"
+      );
+
+      expect(queryEventsSpy).toHaveBeenCalledWith(
+        "test-org",
+        expect.objectContaining({ fields: ["transaction"] })
+      );
+    });
+
     test("passes custom dataset", async () => {
       resolveTargetSpy.mockResolvedValue({ org: "test-org" });
       const { context } = createContext();
diff --git a/test/lib/replay-search.test.ts b/test/lib/replay-search.test.ts
index 743f39515..55b1a1eb0 100644
--- a/test/lib/replay-search.test.ts
+++ b/test/lib/replay-search.test.ts
@@ -2,6 +2,8 @@ import { describe, expect, test } from "vitest";
 import {
   getReplayRequestFields,
   isSupportedReplayField,
+  normalizeVariadicFlag,
+  parseReplayEnvironmentFilter,
 } from "../../src/lib/replay-search.js";
 
 describe("getReplayRequestFields", () => {
@@ -38,3 +40,38 @@ describe("isSupportedReplayField", () => {
     expect(isSupportedReplayField("replay_type")).toBe(false);
   });
 });
+
+describe("normalizeVariadicFlag", () => {
+  test("wraps a single string value into an array", () => {
+    // A single `-e` flag arrives from the parser as a bare string, not a
+    // one-element array (CLI-28C).
+    expect(normalizeVariadicFlag("production")).toEqual(["production"]);
+  });
+
+  test("passes an array through and returns [] for undefined", () => {
+    expect(normalizeVariadicFlag(["a", "b"])).toEqual(["a", "b"]);
+    expect(normalizeVariadicFlag(undefined)).toEqual([]);
+  });
+});
+
+describe("parseReplayEnvironmentFilter", () => {
+  test("treats a single -e value as one environment, not per-character", () => {
+    // Regression: a bare string must not be spread into characters.
+    expect(
+      parseReplayEnvironmentFilter("production" as unknown as string[])
+    ).toEqual(["production"]);
+  });
+
+  test("splits comma-separated and repeated values", () => {
+    expect(parseReplayEnvironmentFilter(["prod,staging", "dev"])).toEqual([
+      "prod",
+      "staging",
+      "dev",
+    ]);
+  });
+
+  test("returns undefined when empty", () => {
+    expect(parseReplayEnvironmentFilter(undefined)).toBeUndefined();
+    expect(parseReplayEnvironmentFilter([])).toBeUndefined();
+  });
+});