diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3161d793c79..0b5167ac306 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,7 @@ Docs: https://docs.openclaw.ai
 - Telegram: preserve replied-to bot messages, captions, and media metadata in group reply chains so follow-up replies understand what the user is reacting to. (#82863)
 - Providers/Together: update PI runtime packages to 0.74.1 and emit Together-style `reasoning.enabled`/`max_tokens` controls for reasoning-capable OpenAI-completions models.
 - Agents/diagnostics: split slow embedded-run `attempt-dispatch` startup summaries into workspace, prompt, runtime-plan, and final dispatch subspans so traces identify the delayed setup phase. Fixes #82782. (#82783) Thanks @galiniliev.
+- Agents/Codex: flatten nested tool-result middleware blocks into bounded text so successful message sends are no longer replaced with `Tool output unavailable due to post-processing error`. Fixes #82912. Thanks @joeykrug.
 - CLI/media: accept HTTP(S) URLs in `openclaw infer image describe --file`, fetching remote images through the guarded media path instead of treating URLs as local files. Fixes #82837. (#82854) Thanks @neeravmakwana.
 - Agents/subagents: keep session-backed parent runs active when the child wait call times out before the child session has actually settled, so late subagent completions are reconciled instead of being lost. Fixes #82787. Thanks @ramitrkar-hash.
 - Control UI: advertise shared Gateway protocol constants in browser connect frames, fixing protocol mismatch handshakes after protocol constant drift. Fixes #82882. Thanks @galiniliev.
diff --git a/extensions/codex/src/app-server/dynamic-tools.test.ts b/extensions/codex/src/app-server/dynamic-tools.test.ts
index 3abf0ef9e33..2bec50df6e3 100644
--- a/extensions/codex/src/app-server/dynamic-tools.test.ts
+++ b/extensions/codex/src/app-server/dynamic-tools.test.ts
@@ -495,6 +495,43 @@ describe("createCodexDynamicToolBridge", () => {
     expectContextFields(callArg(handler, 0, 1, "middleware context"), { runtime: "codex" });
   });
 
+  it("preserves nested toolResult content after no-op middleware", async () => {
+    const registry = createEmptyPluginRegistry();
+    const handler = vi.fn(async () => undefined);
+    registry.agentToolResultMiddlewares.push({
+      pluginId: "tokenjuice",
+      pluginName: "Tokenjuice",
+      rawHandler: handler,
+      handler,
+      runtimes: ["codex"],
+      source: "test",
+    });
+    setActivePluginRegistry(registry);
+
+    const bridge = createBridgeWithToolResult("message", {
+      content: [
+        {
+          type: "toolResult",
+          toolUseId: "call-1",
+          content: [{ type: "text", text: "message sent: msg_123" }],
+        } as never,
+      ],
+      details: { messageId: "msg_123" },
+    });
+
+    const result = await bridge.handleToolCall({
+      threadId: "thread-1",
+      turnId: "turn-1",
+      callId: "call-1",
+      namespace: null,
+      tool: "message",
+      arguments: { text: "hello" },
+    });
+
+    expect(result).toEqual(expectInputText("message sent: msg_123"));
+    expect(handler).toHaveBeenCalledTimes(1);
+  });
+
   it("passes raw tool failure state into agent tool result middleware", async () => {
     const registry = createEmptyPluginRegistry();
     const handler = vi.fn(async (_event: { isError?: boolean }) => undefined);
diff --git a/src/agents/harness/tool-result-middleware.test.ts b/src/agents/harness/tool-result-middleware.test.ts
index c0698ebed1a..7a61eba62d9 100644
--- a/src/agents/harness/tool-result-middleware.test.ts
+++ b/src/agents/harness/tool-result-middleware.test.ts
@@ -167,6 +167,291 @@ describe("createAgentToolResultMiddlewareRunner", () => {
     });
   });
 
+  it("sanitizes incoming details before failing closed on uncoercible content", async () => {
+    const details: Record<string, unknown> = {
+      ok: true,
+      callback: () => 1,
+    };
+    details.self = details;
+    let observedDetails: unknown;
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [
+      (event) => {
+        observedDetails = event.result.details;
+        return undefined;
+      },
+    ]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "message",
+      args: {},
+      result: {
+        content: [{ type: "unknown", payload: "raw" } as never],
+        details,
+      },
+    });
+
+    expect(result.details).toEqual({ status: "error", middlewareError: true });
+    expect(observedDetails).toEqual({ ok: true });
+  });
+
+  it("coerces incoming nested toolResult content before middleware validation", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "message",
+      args: {},
+      result: {
+        content: [
+          {
+            type: "toolResult",
+            toolUseId: "call-1",
+            content: [
+              { type: "text", text: "sent message id msg_123" },
+              { type: "text", text: "status delivered" },
+            ],
+          } as never,
+        ],
+        details: { status: "sent", messageId: "msg_123" },
+      },
+    });
+
+    expect(result.content).toEqual([
+      {
+        type: "text",
+        text: "sent message id msg_123\nstatus delivered",
+      },
+    ]);
+    expect(result.details).toEqual({ status: "sent", messageId: "msg_123" });
+  });
+
+  it("coerces nested tool_result blocks returned by middleware", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [
+      () => ({
+        result: {
+          content: [
+            {
+              type: "tool_result",
+              content: {
+                message: "message delivered",
+                id: "msg_456",
+              },
+            } as never,
+          ],
+          details: { status: "sent" },
+        },
+      }),
+    ]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "message",
+      args: {},
+      result: { content: [{ type: "text", text: "raw" }], details: {} },
+    });
+
+    expect(result.content).toEqual([{ type: "text", text: "message delivered" }]);
+    expect(result.details).toEqual({ status: "sent" });
+  });
+
+  it("does not coerce tool/function call blocks as middleware results", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [
+      () => ({
+        result: {
+          content: [
+            {
+              type: "function",
+              name: "send_message",
+              arguments: { text: "raw" },
+            } as never,
+          ],
+          details: {},
+        },
+      }),
+    ]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "message",
+      args: {},
+      result: { content: [{ type: "text", text: "raw" }], details: {} },
+    });
+
+    expect(result.details).toEqual({ status: "error", middlewareError: true });
+  });
+
+  it("bounds nested toolResult content before flattening", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "message",
+      args: {},
+      result: {
+        content: [
+          {
+            type: "toolResult",
+            toolUseId: "call-1",
+            content: [
+              ...Array.from({ length: 200 }, () => ({
+                type: "text",
+                text: "x".repeat(600),
+              })),
+              { type: "text", text: "late chunk" },
+            ],
+          } as never,
+        ],
+        details: {},
+      },
+    });
+
+    const content = result.content[0];
+    if (content?.type !== "text") {
+      throw new Error("expected flattened text content");
+    }
+    expect(content.text.length).toBeLessThanOrEqual(100_000);
+    expect(content.text).not.toContain("late chunk");
+  });
+
+  it("preserves nested image toolResult content without stringifying data", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "vision",
+      args: {},
+      result: {
+        content: [
+          {
+            type: "toolResult",
+            toolUseId: "call-1",
+            content: [{ type: "image", mimeType: "image/png", data: "base64-image" }],
+          } as never,
+        ],
+        details: {},
+      },
+    });
+
+    expect(result.content).toEqual([
+      { type: "image", mimeType: "image/png", data: "base64-image" },
+    ]);
+  });
+
+  it("preserves mixed nested text and image toolResult content", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "screenshot",
+      args: {},
+      result: {
+        content: [
+          {
+            type: "toolResult",
+            toolUseId: "call-1",
+            content: [
+              { type: "text", text: "captured screenshot" },
+              { type: "image", mimeType: "image/png", data: "base64-image" },
+            ],
+          } as never,
+        ],
+        details: {},
+      },
+    });
+
+    expect(result.content).toEqual([
+      { type: "text", text: "captured screenshot" },
+      { type: "image", mimeType: "image/png", data: "base64-image" },
+    ]);
+  });
+
+  it("preserves images from deeper nested toolResult content", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "screenshot",
+      args: {},
+      result: {
+        content: [
+          {
+            type: "toolResult",
+            toolUseId: "call-1",
+            content: [
+              {
+                type: "tool_result",
+                content: [
+                  { type: "text", text: "captured screenshot" },
+                  { type: "image", mimeType: "image/png", data: "base64-image" },
+                ],
+              },
+            ],
+          } as never,
+        ],
+        details: {},
+      },
+    });
+
+    expect(result.content).toEqual([
+      { type: "text", text: "captured screenshot" },
+      { type: "image", mimeType: "image/png", data: "base64-image" },
+    ]);
+  });
+
+  it("preserves interleaved nested text and image order", async () => {
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "screenshot",
+      args: {},
+      result: {
+        content: [
+          {
+            type: "toolResult",
+            toolUseId: "call-1",
+            content: [
+              { type: "text", text: "first caption" },
+              { type: "image", mimeType: "image/png", data: "image-one" },
+              { type: "text", text: "second caption" },
+              { type: "image", mimeType: "image/png", data: "image-two" },
+            ],
+          } as never,
+        ],
+        details: {},
+      },
+    });
+
+    expect(result.content).toEqual([
+      { type: "text", text: "first caption" },
+      { type: "image", mimeType: "image/png", data: "image-one" },
+      { type: "text", text: "second caption" },
+      { type: "image", mimeType: "image/png", data: "image-two" },
+    ]);
+  });
+
+  it("fails closed instead of recursing forever on cyclic nested content", async () => {
+    const nested: Record<string, unknown> = {
+      type: "toolResult",
+      content: [],
+    };
+    nested.content = [nested];
+    const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
+
+    const result = await runner.applyToolResultMiddleware({
+      toolCallId: "call-1",
+      toolName: "message",
+      args: {},
+      result: {
+        content: [nested as never],
+        details: {},
+      },
+    });
+
+    expect(result.details).toEqual({ status: "error", middlewareError: true });
+  });
+
   it("sanitizes incoming function/symbol/bigint values in details", async () => {
     const runner = createAgentToolResultMiddlewareRunner({ runtime: "codex" }, [() => undefined]);
 
diff --git a/src/agents/harness/tool-result-middleware.ts b/src/agents/harness/tool-result-middleware.ts
index 8a5febf3ae3..d464dced603 100644
--- a/src/agents/harness/tool-result-middleware.ts
+++ b/src/agents/harness/tool-result-middleware.ts
@@ -12,9 +12,14 @@ const log = createSubsystemLogger("agents/harness");
 const MAX_MIDDLEWARE_CONTENT_BLOCKS = 200;
 const MAX_MIDDLEWARE_TEXT_CHARS = 100_000;
 const MAX_MIDDLEWARE_IMAGE_DATA_CHARS = 5_000_000;
+const MAX_MIDDLEWARE_CONTENT_DEPTH = 20;
 const MAX_MIDDLEWARE_DETAILS_BYTES = 100_000;
 const MAX_MIDDLEWARE_DETAILS_DEPTH = 20;
 const MAX_MIDDLEWARE_DETAILS_KEYS = 1_000;
+const NESTED_TOOL_RESULT_BLOCK_TYPES = new Set(["toolresult", "tool_result"]);
+
+type MiddlewareContentBlock = OpenClawAgentToolResult["content"][number];
+type MiddlewareContentCoerceState = { depth: number; seen: Set<object> };
 
 function isRecord(value: unknown): value is Record<string, unknown> {
   return value !== null && typeof value === "object" && !Array.isArray(value);
@@ -105,6 +110,230 @@ function isValidMiddlewareToolResult(value: unknown): value is OpenClawAgentTool
   );
 }
 
+function createMiddlewareContentCoerceState(): MiddlewareContentCoerceState {
+  return { depth: 0, seen: new Set<object>() };
+}
+
+function descendMiddlewareContentCoerceState(
+  value: unknown,
+  state: MiddlewareContentCoerceState,
+): MiddlewareContentCoerceState | undefined {
+  if (state.depth >= MAX_MIDDLEWARE_CONTENT_DEPTH) {
+    return undefined;
+  }
+  if (value !== null && typeof value === "object") {
+    if (state.seen.has(value)) {
+      return undefined;
+    }
+    const seen = new Set(state.seen);
+    seen.add(value);
+    return { depth: state.depth + 1, seen };
+  }
+  return { depth: state.depth + 1, seen: state.seen };
+}
+
+function stringifyMiddlewareTextPayload(value: unknown): string | undefined {
+  const seen = new WeakSet<object>();
+  try {
+    return JSON.stringify(value, (_key, val) => {
+      if (typeof val === "bigint") {
+        return val.toString();
+      }
+      if (typeof val === "function" || typeof val === "symbol" || val === undefined) {
+        return undefined;
+      }
+      if (val !== null && typeof val === "object") {
+        if (seen.has(val)) {
+          return undefined;
+        }
+        seen.add(val);
+      }
+      return val;
+    });
+  } catch {
+    return undefined;
+  }
+}
+
+function coerceMiddlewareText(
+  value: unknown,
+  state: MiddlewareContentCoerceState = createMiddlewareContentCoerceState(),
+): string | undefined {
+  if (typeof value === "string") {
+    return value;
+  }
+  if (typeof value === "number" || typeof value === "boolean" || typeof value === "bigint") {
+    return String(value);
+  }
+  if (!isRecord(value)) {
+    return undefined;
+  }
+  const nextState = descendMiddlewareContentCoerceState(value, state);
+  if (!nextState) {
+    return undefined;
+  }
+  for (const key of ["text", "output", "result", "message"]) {
+    const text = coerceMiddlewareText(value[key], nextState);
+    if (text !== undefined) {
+      return text;
+    }
+  }
+  const content = value.content;
+  if (Array.isArray(content)) {
+    const chunks = coerceMiddlewareContentArray(content, nextState)
+      .filter(
+        (block): block is Extract<MiddlewareContentBlock, { type: "text" }> =>
+          block.type === "text",
+      )
+      .map((block) => block.text)
+      .filter((text) => text.length > 0);
+    return chunks.length > 0 ? chunks.join("\n") : undefined;
+  }
+  return stringifyMiddlewareTextPayload(value);
+}
+
+function appendMiddlewareContentBlock(
+  blocks: MiddlewareContentBlock[],
+  block: MiddlewareContentBlock,
+): void {
+  if (blocks.length >= MAX_MIDDLEWARE_CONTENT_BLOCKS) {
+    return;
+  }
+  if (block.type !== "text") {
+    blocks.push(block);
+    return;
+  }
+  if (!block.text) {
+    return;
+  }
+  const previous = blocks.at(-1);
+  if (previous?.type !== "text") {
+    blocks.push({
+      type: "text",
+      text: truncateUtf16Safe(block.text, MAX_MIDDLEWARE_TEXT_CHARS),
+    });
+    return;
+  }
+  const remainingChars = MAX_MIDDLEWARE_TEXT_CHARS - previous.text.length - 1;
+  if (remainingChars <= 0) {
+    return;
+  }
+  previous.text = `${previous.text}\n${truncateUtf16Safe(block.text, remainingChars)}`;
+}
+
+function coerceMiddlewareContentArray(
+  content: unknown[],
+  state: MiddlewareContentCoerceState,
+): MiddlewareContentBlock[] {
+  const blocks: MiddlewareContentBlock[] = [];
+  let inspectedBlocks = 0;
+  for (const entry of content) {
+    inspectedBlocks += 1;
+    if (
+      inspectedBlocks > MAX_MIDDLEWARE_CONTENT_BLOCKS ||
+      blocks.length >= MAX_MIDDLEWARE_CONTENT_BLOCKS
+    ) {
+      break;
+    }
+    const coercedBlocks = coerceMiddlewareContentBlocks(entry, state);
+    if (coercedBlocks.length > 0) {
+      for (const block of coercedBlocks) {
+        appendMiddlewareContentBlock(blocks, block);
+        if (blocks.length >= MAX_MIDDLEWARE_CONTENT_BLOCKS) {
+          break;
+        }
+      }
+      continue;
+    }
+    const text = coerceMiddlewareText(entry, state);
+    if (text) {
+      appendMiddlewareContentBlock(blocks, {
+        type: "text",
+        text: truncateUtf16Safe(text, MAX_MIDDLEWARE_TEXT_CHARS),
+      });
+    }
+  }
+  return blocks;
+}
+
+function coerceMiddlewareContentBlocks(
+  value: unknown,
+  state: MiddlewareContentCoerceState = createMiddlewareContentCoerceState(),
+): MiddlewareContentBlock[] {
+  if (isValidMiddlewareContentBlock(value)) {
+    return [value as MiddlewareContentBlock];
+  }
+  if (!isRecord(value) || typeof value.type !== "string") {
+    return [];
+  }
+  const normalizedType = value.type.toLowerCase();
+  if (!NESTED_TOOL_RESULT_BLOCK_TYPES.has(normalizedType)) {
+    return [];
+  }
+  const content = value.content;
+  if (Array.isArray(content) && content.length > 0) {
+    const nextState = descendMiddlewareContentCoerceState(value, state);
+    return nextState ? coerceMiddlewareContentArray(content, nextState) : [];
+  }
+  const text = coerceMiddlewareText(content, state) ?? coerceMiddlewareText(value, state);
+  if (!text) {
+    return [];
+  }
+  return [
+    {
+      type: "text",
+      text: truncateUtf16Safe(text, MAX_MIDDLEWARE_TEXT_CHARS),
+    },
+  ];
+}
+
+function coerceMiddlewareToolResult(
+  value: unknown,
+  options: { sanitizeDetails?: boolean } = {},
+): OpenClawAgentToolResult | undefined {
+  if (isValidMiddlewareToolResult(value)) {
+    return value;
+  }
+  if (!isRecord(value) || !Array.isArray(value.content)) {
+    return undefined;
+  }
+  const content: OpenClawAgentToolResult["content"] = [];
+  const state = createMiddlewareContentCoerceState();
+  let inspectedBlocks = 0;
+  for (const block of value.content) {
+    inspectedBlocks += 1;
+    if (inspectedBlocks > MAX_MIDDLEWARE_CONTENT_BLOCKS) {
+      break;
+    }
+    for (const coerced of coerceMiddlewareContentBlocks(block, state)) {
+      content.push(coerced);
+      if (content.length >= MAX_MIDDLEWARE_CONTENT_BLOCKS) {
+        break;
+      }
+    }
+    if (content.length >= MAX_MIDDLEWARE_CONTENT_BLOCKS) {
+      break;
+    }
+  }
+  if (content.length === 0) {
+    return undefined;
+  }
+  const details = isValidMiddlewareDetails(value.details)
+    ? value.details
+    : options.sanitizeDetails === true
+      ? sanitizeMiddlewareDetailsValue(value.details)
+      : undefined;
+  if (details === undefined && !isValidMiddlewareDetails(value.details)) {
+    return undefined;
+  }
+  const result = {
+    ...value,
+    content,
+    details,
+  };
+  return isValidMiddlewareToolResult(result) ? result : undefined;
+}
+
 /**
  * Coerce an arbitrary value into a JSON-safe shape that satisfies
  * `isValidMiddlewareDetails`. Round-trips through `JSON.stringify` with a
@@ -150,6 +379,10 @@ function sanitizeMiddlewareDetailsValue(value: unknown): unknown {
  * subsequent middleware-side mutations are still validated strictly.
  */
 function sanitizeToolResultForMiddleware(result: OpenClawAgentToolResult): OpenClawAgentToolResult {
+  const coerced = coerceMiddlewareToolResult(result, { sanitizeDetails: true });
+  if (coerced) {
+    return coerced;
+  }
   if (result.details === undefined || result.details === null) {
     return result;
   }
@@ -214,8 +447,9 @@ export function createAgentToolResultMiddlewareRunner(
           // Validate the current object after every handler so in-place writes
           // cannot bypass the same shape and size bounds as returned results.
           const candidate = next?.result ?? current;
-          if (isValidMiddlewareToolResult(candidate)) {
-            current = candidate;
+          const coercedCandidate = coerceMiddlewareToolResult(candidate);
+          if (coercedCandidate) {
+            current = coercedCandidate;
           } else {
             log.warn(
               `[${ctx.runtime}] discarded invalid tool result middleware output for ${truncateUtf16Safe(