diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b360b5f1c0..1515d642805 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,6 +51,7 @@ Docs: https://docs.openclaw.ai
 - Claude CLI/sessions: classify `No conversation found with session ID` as `session_expired` so expired CLI-backed conversations clear the stale binding and recover on the next turn. (#65028) thanks @Ivan-Fn.
 - Context Engine: gracefully fall back to the legacy engine when a third-party context engine plugin fails at resolution time (unregistered id, factory throw, or contract violation), preventing a full gateway outage on every channel. (#66930) Thanks @openperf.
 - Control UI/chat: keep optimistic user message cards visible during active sends by deferring same-session history reloads until the active run ends, including aborted and errored runs. (#66997) Thanks @scotthuang and @vincentkoc.
+- Media/Slack: allow host-local CSV and Markdown uploads only when the fallback buffer actually decodes as text, so real plain-text files work without letting opaque non-text blobs renamed to `.csv` or `.md` slip past the host-read guard. (#67047) Thanks @Unayung.
 
 ## 2026.4.14
 
diff --git a/src/media/web-media.test.ts b/src/media/web-media.test.ts
index d1c78d86740..a320bef04a7 100644
--- a/src/media/web-media.test.ts
+++ b/src/media/web-media.test.ts
@@ -185,6 +185,248 @@ describe("loadWebMedia", () => {
     });
   });
 
+  it("allows host-read CSV files", async () => {
+    const csvFile = path.join(fixtureRoot, "data.csv");
+    await fs.writeFile(csvFile, "name,value\nfoo,1\nbar,2\n", "utf8");
+    const result = await loadWebMedia(csvFile, {
+      maxBytes: 1024 * 1024,
+      localRoots: "any",
+      readFile: async (filePath) => await fs.readFile(filePath),
+      hostReadCapability: true,
+    });
+    expect(result.kind).toBe("document");
+    expect(result.contentType).toBe("text/csv");
+  });
+
+  it("allows host-read Markdown files", async () => {
+    const mdFile = path.join(fixtureRoot, "notes.md");
+    await fs.writeFile(mdFile, "# Title\n\nSome **bold** text.\n", "utf8");
+    const result = await loadWebMedia(mdFile, {
+      maxBytes: 1024 * 1024,
+      localRoots: "any",
+      readFile: async (filePath) => await fs.readFile(filePath),
+      hostReadCapability: true,
+    });
+    expect(result.kind).toBe("document");
+    expect(result.contentType).toBe("text/markdown");
+  });
+
+  it("rejects binary data disguised as a CSV file", async () => {
+    const fakeCsv = path.join(fixtureRoot, "evil.csv");
+    // Write ZIP magic bytes — file-type detects application/zip (not image, not CSV),
+    // so it is rejected by the host-read policy rather than allowed as an image.
+    await fs.writeFile(fakeCsv, Buffer.from([0x50, 0x4b, 0x03, 0x04]));
+    await expect(
+      loadWebMedia(fakeCsv, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      }),
+    ).rejects.toMatchObject({
+      code: "path-not-allowed",
+    });
+  });
+
+  it.each([
+    { label: "CSV", fileName: "opaque.csv" },
+    { label: "Markdown", fileName: "opaque.md" },
+  ])("rejects opaque non-NUL binary data disguised as %s", async ({ fileName }) => {
+    const fakeTextFile = path.join(fixtureRoot, fileName);
+    const opaqueBinary = Buffer.alloc(9000);
+    for (let i = 0; i < opaqueBinary.length; i += 1) {
+      opaqueBinary[i] = (i % 255) + 1;
+    }
+    await fs.writeFile(fakeTextFile, opaqueBinary);
+    await expect(
+      loadWebMedia(fakeTextFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      }),
+    ).rejects.toMatchObject({
+      code: "path-not-allowed",
+    });
+  });
+
+  it.each([
+    { label: "CSV", fileName: "prefix-tail.csv" },
+    { label: "Markdown", fileName: "prefix-tail.md" },
+  ])(
+    "rejects %s files with a text prefix and binary tail after the old sample window",
+    async ({ fileName }) => {
+      const fakeTextFile = path.join(fixtureRoot, fileName);
+      const textPrefix = Buffer.from(`name,value\n${"row,1\n".repeat(1400)}`, "utf8");
+      expect(textPrefix.length).toBeGreaterThan(8192);
+      const binaryTail = Buffer.from([0x00, 0xff, 0x10, 0x80]);
+      await fs.writeFile(fakeTextFile, Buffer.concat([textPrefix, binaryTail]));
+      await expect(
+        loadWebMedia(fakeTextFile, {
+          maxBytes: 1024 * 1024,
+          localRoots: "any",
+          readFile: async (filePath) => await fs.readFile(filePath),
+          hostReadCapability: true,
+        }),
+      ).rejects.toMatchObject({
+        code: "path-not-allowed",
+      });
+    },
+  );
+
+  it.each([
+    {
+      label: "CSV",
+      fileName: "punctuation.csv",
+      contentType: "text/csv",
+      body: ",,,,,,,,,,\n",
+    },
+    {
+      label: "Markdown",
+      fileName: "punctuation.md",
+      contentType: "text/markdown",
+      body: "---\n***\n> > >\n",
+    },
+  ])(
+    "loads valid punctuation-heavy %s files when host-read capability is enabled",
+    async ({ fileName, contentType, body }) => {
+      const textFile = path.join(fixtureRoot, fileName);
+      await fs.writeFile(textFile, Buffer.from(body, "utf8"));
+      const result = await loadWebMedia(textFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      });
+      expect(result.kind).toBe("document");
+      expect(result.contentType).toBe(contentType);
+    },
+  );
+
+  it.each([
+    {
+      label: "CSV",
+      fileName: "legacy.csv",
+      contentType: "text/csv",
+      body: Buffer.from("caf\xe9,ni\xf1o\n", "latin1"),
+    },
+    {
+      label: "Markdown",
+      fileName: "legacy.md",
+      contentType: "text/markdown",
+      body: Buffer.from("R\xe9sum\xe9\nni\xf1o\n", "latin1"),
+    },
+  ])(
+    "loads valid single-byte encoded %s files when host-read capability is enabled",
+    async ({ fileName, contentType, body }) => {
+      const textFile = path.join(fixtureRoot, fileName);
+      await fs.writeFile(textFile, body);
+      const result = await loadWebMedia(textFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      });
+      expect(result.kind).toBe("document");
+      expect(result.contentType).toBe(contentType);
+    },
+  );
+
+  it.each([
+    { label: "CSV", fileName: "nul-padded.csv" },
+    { label: "Markdown", fileName: "nul-padded.md" },
+  ])("rejects NUL-padded binary data disguised as %s", async ({ fileName }) => {
+    const fakeTextFile = path.join(fixtureRoot, fileName);
+    // Alternating 0x00/0xFF — UTF-8 decode fails (0xFF is invalid UTF-8), then
+    // hasSingleByteTextShape rejects because 0x00 bytes are control chars (< 0x20).
+    const nulPadded = Buffer.alloc(9000);
+    for (let i = 0; i < nulPadded.length; i += 1) {
+      nulPadded[i] = i % 2 === 0 ? 0x00 : 0xff;
+    }
+    await fs.writeFile(fakeTextFile, nulPadded);
+    await expect(
+      loadWebMedia(fakeTextFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      }),
+    ).rejects.toMatchObject({
+      code: "path-not-allowed",
+    });
+  });
+
+  it.each([
+    { label: "CSV", fileName: "bom-binary.csv" },
+    { label: "Markdown", fileName: "bom-binary.md" },
+  ])("rejects UTF-16 BOM-prefixed binary data disguised as %s", async ({ fileName }) => {
+    const fakeTextFile = path.join(fixtureRoot, fileName);
+    // UTF-16LE BOM + repeating 0xFF bytes: if UTF-16 decoding were attempted,
+    // every byte pair would produce a printable code point and pass getTextStats.
+    // With UTF-16 decoding removed, falls through to UTF-8 strict decode (throws
+    // on 0xFF), then hasSingleByteTextShape rejects due to high-byte ratio > 30%.
+    const bom = Buffer.from([0xff, 0xfe]);
+    const garbage = Buffer.alloc(9000, 0xff);
+    await fs.writeFile(fakeTextFile, Buffer.concat([bom, garbage]));
+    await expect(
+      loadWebMedia(fakeTextFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      }),
+    ).rejects.toMatchObject({
+      code: "path-not-allowed",
+    });
+  });
+
+  it.each([
+    { label: "CSV", fileName: "alternating-high.csv" },
+    { label: "Markdown", fileName: "alternating-high.md" },
+  ])("rejects alternating ASCII/high-byte data disguised as %s", async ({ fileName }) => {
+    const fakeTextFile = path.join(fixtureRoot, fileName);
+    // Alternating 0x41 ('A') and 0xFF — exactly 50% ASCII, 50% high bytes.
+    // With the old 50% threshold hasSingleByteTextShape would accept this;
+    // the tightened 70%/30% thresholds must reject it.
+    const mixed = Buffer.alloc(9000);
+    for (let i = 0; i < mixed.length; i += 1) {
+      mixed[i] = i % 2 === 0 ? 0x41 : 0xff;
+    }
+    await fs.writeFile(fakeTextFile, mixed);
+    await expect(
+      loadWebMedia(fakeTextFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      }),
+    ).rejects.toMatchObject({
+      code: "path-not-allowed",
+    });
+  });
+
+  it.each([
+    { label: "CSV", fileName: "high-bytes.csv" },
+    { label: "Markdown", fileName: "high-bytes.md" },
+  ])("rejects high-byte opaque data disguised as %s", async ({ fileName }) => {
+    const fakeTextFile = path.join(fixtureRoot, fileName);
+    const opaqueBinary = Buffer.alloc(9000);
+    for (let i = 0; i < opaqueBinary.length; i += 1) {
+      opaqueBinary[i] = 0xa0 + (i % 96);
+    }
+    await fs.writeFile(fakeTextFile, opaqueBinary);
+    await expect(
+      loadWebMedia(fakeTextFile, {
+        maxBytes: 1024 * 1024,
+        localRoots: "any",
+        readFile: async (filePath) => await fs.readFile(filePath),
+        hostReadCapability: true,
+      }),
+    ).rejects.toMatchObject({
+      code: "path-not-allowed",
+    });
+  });
+
   it("rejects traversal-style canvas media paths before filesystem access", async () => {
     await expect(
       loadWebMedia(`${CANVAS_HOST_PATH}/documents/../collection.media/tiny.png`),
diff --git a/src/media/web-media.ts b/src/media/web-media.ts
index 9205d6fb273..bc286026e58 100644
--- a/src/media/web-media.ts
+++ b/src/media/web-media.ts
@@ -24,6 +24,7 @@ import {
   extensionForMime,
   getFileExtension,
   kindFromMime,
+  mimeTypeFromFilePath,
   normalizeMimeType,
 } from "./mime.js";
 
@@ -83,9 +84,95 @@ const HOST_READ_ALLOWED_DOCUMENT_MIMES = new Set([
   "application/vnd.openxmlformats-officedocument.presentationml.presentation",
   "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
   "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+  "text/csv",
+  "text/markdown",
 ]);
+// file-type returns undefined (no magic bytes) for plain-text formats like CSV and
+// Markdown, so host-read needs an explicit "this really decodes as text" fallback.
+const HOST_READ_TEXT_PLAIN_ALIASES = new Set(["text/csv", "text/markdown"]);
 const MB = 1024 * 1024;
 
+function getTextStats(text: string): { printableRatio: number } {
+  if (!text) {
+    return { printableRatio: 0 };
+  }
+  let printable = 0;
+  let control = 0;
+  for (const char of text) {
+    const code = char.codePointAt(0) ?? 0;
+    if (code === 9 || code === 10 || code === 13 || code === 32) {
+      printable += 1;
+      continue;
+    }
+    if (code < 32 || (code >= 0x7f && code <= 0x9f)) {
+      control += 1;
+      continue;
+    }
+    printable += 1;
+  }
+  const total = printable + control;
+  if (total === 0) {
+    return { printableRatio: 0 };
+  }
+  return { printableRatio: printable / total };
+}
+
+function hasSingleByteTextShape(buffer: Buffer): boolean {
+  if (buffer.length === 0) {
+    return true;
+  }
+  let asciiText = 0;
+  let control = 0;
+  for (const byte of buffer) {
+    if (byte === 9 || byte === 10 || byte === 13 || (byte >= 0x20 && byte <= 0x7e)) {
+      asciiText += 1;
+      continue;
+    }
+    if (byte < 0x20 || byte === 0x7f) {
+      control += 1;
+    }
+  }
+  const total = buffer.length;
+  const highBytes = total - asciiText - control;
+  return control === 0 && asciiText / total >= 0.7 && highBytes / total <= 0.3;
+}
+
+function decodeHostReadText(buffer: Buffer): string | undefined {
+  if (buffer.length === 0) {
+    return "";
+  }
+  // UTF-16 decoding is intentionally omitted: TextDecoder("utf-16le/be") never throws on
+  // arbitrary byte pairs, so every byte pair is a valid (if meaningless) Unicode scalar —
+  // an attacker can prepend a BOM and pass getTextStats with printableRatio≈1.0 on pure
+  // binary garbage. The Latin-1 path below already covers the most common non-UTF-8
+  // real-world case (Excel CSV exports with accented chars like é, ñ) while remaining
+  // safe because hasSingleByteTextShape gates on byte shape *before* any decode.
+  try {
+    return new TextDecoder("utf-8", { fatal: true }).decode(buffer);
+  } catch {
+    if (!hasSingleByteTextShape(buffer)) {
+      return undefined;
+    }
+    // WHATWG latin1 decodes common Excel-style single-byte exports via Windows-1252 mapping.
+    return new TextDecoder("latin1").decode(buffer);
+  }
+}
+
+function isValidatedHostReadText(buffer?: Buffer): boolean {
+  if (!buffer) {
+    return false;
+  }
+  if (buffer.length === 0) {
+    return true;
+  }
+  const text = decodeHostReadText(buffer);
+  if (text === undefined) {
+    return false;
+  }
+  const { printableRatio } = getTextStats(text);
+  return printableRatio > 0.95;
+}
+
 function formatMb(bytes: number, digits = 2): string {
   return (bytes / MB).toFixed(digits);
 }
@@ -113,7 +200,23 @@ function assertHostReadMediaAllowed(params: {
   contentType?: string;
   filePath?: string;
   kind: MediaKind | undefined;
+  buffer?: Buffer;
 }): void {
+  const declaredMime = normalizeMimeType(mimeTypeFromFilePath(params.filePath));
+  const normalizedMime = normalizeMimeType(params.contentType);
+  // For extension-declared plain-text aliases such as .csv/.md, trust only the
+  // text validator path. Some opaque blobs can still produce bogus binary MIME
+  // hits (for example BOM-prefixed 0xFF data sniffing as audio/mpeg), and
+  // host-read should reject those instead of returning early on the sniff.
+  if (declaredMime && HOST_READ_TEXT_PLAIN_ALIASES.has(declaredMime)) {
+    if (!params.sniffedContentType && params.buffer && isValidatedHostReadText(params.buffer)) {
+      return;
+    }
+    throw new LocalMediaAccessError(
+      "path-not-allowed",
+      "hostReadCapability permits only validated plain-text CSV/Markdown documents for local reads",
+    );
+  }
   const sniffedKind = kindFromMime(params.sniffedContentType);
   if (sniffedKind === "image" || sniffedKind === "audio" || sniffedKind === "video") {
     return;
@@ -132,7 +235,20 @@ function assertHostReadMediaAllowed(params: {
   ) {
     return;
   }
-  const normalizedMime = normalizeMimeType(params.contentType);
+  // CSV / Markdown exception: file-type v22 returns undefined (not "text/plain") for
+  // plain-text buffers that have no binary magic bytes. Allow these formats when:
+  // - sniffedMime is undefined (no binary signature detected by file-type)
+  // - The extension-derived MIME is text/csv or text/markdown (operator intent)
+  // - The buffer decodes as actual text instead of opaque binary bytes
+  if (
+    !sniffedMime &&
+    normalizedMime &&
+    HOST_READ_TEXT_PLAIN_ALIASES.has(normalizedMime) &&
+    params.buffer &&
+    isValidatedHostReadText(params.buffer)
+  ) {
+    return;
+  }
   if (
     params.kind === "document" &&
     normalizedMime &&
@@ -392,6 +508,7 @@ async function loadWebMediaInternal(
       contentType: mime,
       filePath: mediaUrl,
       kind,
+      buffer: data,
     });
   }
   let fileName = path.basename(mediaUrl) || undefined;