feat(mattermost): add retry logic and timeout handling for DM channel creation (#42398)

Merged via squash.

Prepared head SHA: 3db47be907
Co-authored-by: JonathanJing <17068507+JonathanJing@users.noreply.github.com>
Co-authored-by: mukhtharcm <56378562+mukhtharcm@users.noreply.github.com>
Reviewed-by: @mukhtharcm

CHANGELOG.md

@@ -133,6 +133,7 @@ Docs: https://docs.openclaw.ai
 - macOS/launch at login: stop emitting `KeepAlive` for the desktop app launch agent so OpenClaw no longer relaunches immediately after a manual quit while launch at login remains enabled. (#40213) Thanks @stablegenius49.
 - ACP/gateway startup: use direct Telegram and Discord startup/status helpers instead of routing probes through the plugin runtime, and prepend the selected daemon Node bin dir to service PATH so plugin-local installs can still find `npm` and `pnpm`.
 - ACP/configured bindings: reinitialize configured ACP sessions that are stuck in `error` state instead of reusing the failed runtime.
+- Mattermost/DM send: retry transient direct-channel creation failures for DM deliveries, with configurable backoff and per-request timeout. (#42398) Thanks @JonathanJing.
 
 ## 2026.3.13
 

docs/channels/mattermost.md

@@ -191,6 +191,35 @@ OpenClaw resolves them **user-first**:
 
 If you need deterministic behavior, always use the explicit prefixes (`user:<id>` / `channel:<id>`).
 
+## DM channel retry
+
+When OpenClaw sends to a Mattermost DM target and needs to resolve the direct channel first, it
+retries transient direct-channel creation failures by default.
+
+Use `channels.mattermost.dmChannelRetry` to tune that behavior globally for the Mattermost plugin,
+or `channels.mattermost.accounts.<id>.dmChannelRetry` for one account.
+
+```json5
+{
+  channels: {
+    mattermost: {
+      dmChannelRetry: {
+        maxRetries: 3,
+        initialDelayMs: 1000,
+        maxDelayMs: 10000,
+        timeoutMs: 30000,
+      },
+    },
+  },
+}
+```
+
+Notes:
+
+- This applies only to DM channel creation (`/api/v4/channels/direct`), not every Mattermost API call.
+- Retries apply to transient failures such as rate limits, 5xx responses, and network or timeout errors.
+- 4xx client errors other than `429` are treated as permanent and are not retried.
+
 ## Reactions (message tool)
 
 - Use `message action=react` with `channel=mattermost`.

extensions/mattermost/src/config-schema.ts

@@ -9,6 +9,32 @@ import { z } from "zod";
 import { requireChannelOpenAllowFrom } from "../../shared/config-schema-helpers.js";
 import { buildSecretInputSchema } from "./secret-input.js";
 
+const DmChannelRetrySchema = z
+  .object({
+    /** Maximum number of retry attempts for DM channel creation (default: 3) */
+    maxRetries: z.number().int().min(0).max(10).optional(),
+    /** Initial delay in milliseconds before first retry (default: 1000) */
+    initialDelayMs: z.number().int().min(100).max(60000).optional(),
+    /** Maximum delay in milliseconds between retries (default: 10000) */
+    maxDelayMs: z.number().int().min(1000).max(60000).optional(),
+    /** Timeout for each individual DM channel creation request in milliseconds (default: 30000) */
+    timeoutMs: z.number().int().min(5000).max(120000).optional(),
+  })
+  .strict()
+  .refine(
+    (data) => {
+      if (data.initialDelayMs !== undefined && data.maxDelayMs !== undefined) {
+        return data.initialDelayMs <= data.maxDelayMs;
+      }
+      return true;
+    },
+    {
+      message: "initialDelayMs must be less than or equal to maxDelayMs",
+      path: ["initialDelayMs"],
+    },
+  )
+  .optional();
+
 const MattermostSlashCommandsSchema = z
   .object({
     /** Enable native slash commands. "auto" resolves to false (opt-in). */
@@ -58,6 +84,8 @@ const MattermostAccountSchemaBase = z
         allowedSourceIps: z.array(z.string()).optional(),
       })
       .optional(),
+    /** Retry configuration for DM channel creation */
+    dmChannelRetry: DmChannelRetrySchema,
   })
   .strict();
 

extensions/mattermost/src/mattermost/client.retry.test.ts

@@ -0,0 +1,466 @@
+import { describe, expect, it, vi, beforeEach } from "vitest";
+import { createMattermostClient, createMattermostDirectChannelWithRetry } from "./client.js";
+
+describe("createMattermostDirectChannelWithRetry", () => {
+  const mockFetch = vi.fn();
+
+  beforeEach(() => {
+    vi.resetAllMocks();
+  });
+
+  function createMockClient() {
+    return createMattermostClient({
+      baseUrl: "https://mattermost.example.com",
+      botToken: "test-token",
+      fetchImpl: mockFetch as unknown as typeof fetch,
+    });
+  }
+
+  function createFetchFailedError(params: { message: string; code?: string }): TypeError {
+    const cause = Object.assign(new Error(params.message), {
+      code: params.code,
+    });
+    return Object.assign(new TypeError("fetch failed"), { cause });
+  }
+
+  it("succeeds on first attempt without retries", async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: true,
+      status: 201,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ id: "dm-channel-123" }),
+    } as Response);
+
+    const client = createMockClient();
+    const onRetry = vi.fn();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      onRetry,
+    });
+
+    expect(result.id).toBe("dm-channel-123");
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+    expect(onRetry).not.toHaveBeenCalled();
+  });
+
+  it("retries on 429 rate limit error and succeeds", async () => {
+    mockFetch
+      .mockResolvedValueOnce({
+        ok: false,
+        status: 429,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ message: "Too many requests" }),
+        text: async () => "Too many requests",
+      } as Response)
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-456" }),
+      } as Response);
+
+    const client = createMockClient();
+    const onRetry = vi.fn();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 10,
+      onRetry,
+    });
+
+    expect(result.id).toBe("dm-channel-456");
+    expect(mockFetch).toHaveBeenCalledTimes(2);
+    expect(onRetry).toHaveBeenCalledTimes(1);
+    expect(onRetry).toHaveBeenCalledWith(
+      1,
+      expect.any(Number),
+      expect.objectContaining({ message: expect.stringContaining("429") }),
+    );
+  });
+
+  it("retries on port 443 connection errors (not misclassified as 4xx)", async () => {
+    // This tests that port numbers like :443 don't trigger false 4xx classification
+    mockFetch
+      .mockRejectedValueOnce(new Error("connect ECONNRESET 104.18.32.10:443"))
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-port" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 10,
+    });
+
+    // Should retry and succeed on second attempt (port 443 should NOT be treated as 4xx)
+    expect(mockFetch).toHaveBeenCalledTimes(2);
+    expect(result.id).toBe("dm-channel-port");
+  });
+
+  it("does not retry on 400 even if error message contains '429' text", async () => {
+    // This tests that "429" in error detail doesn't trigger false rate-limit retry
+    // e.g., "Invalid user ID: 4294967295" should NOT be retried
+    mockFetch.mockResolvedValueOnce({
+      ok: false,
+      status: 400,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ message: "Invalid user ID: 4294967295" }),
+      text: async () => "Invalid user ID: 4294967295",
+    } as Response);
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        maxRetries: 3,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow();
+
+    // Should not retry - only called once (400 is a client error, even though message contains "429")
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+  });
+
+  it("retries on 5xx server errors", async () => {
+    mockFetch
+      .mockResolvedValueOnce({
+        ok: false,
+        status: 503,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ message: "Service unavailable" }),
+        text: async () => "Service unavailable",
+      } as Response)
+      .mockResolvedValueOnce({
+        ok: false,
+        status: 502,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ message: "Bad gateway" }),
+        text: async () => "Bad gateway",
+      } as Response)
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-789" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 10,
+    });
+
+    expect(result.id).toBe("dm-channel-789");
+    expect(mockFetch).toHaveBeenCalledTimes(3);
+  });
+
+  it("retries on network errors", async () => {
+    mockFetch
+      .mockRejectedValueOnce(new Error("Network error: connection refused"))
+      .mockRejectedValueOnce(new Error("ECONNRESET"))
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-abc" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 10,
+    });
+
+    expect(result.id).toBe("dm-channel-abc");
+    expect(mockFetch).toHaveBeenCalledTimes(3);
+  });
+
+  it("retries on fetch failed errors when the cause carries a transient code", async () => {
+    mockFetch
+      .mockRejectedValueOnce(
+        createFetchFailedError({
+          message: "connect ECONNREFUSED 127.0.0.1:81",
+          code: "ECONNREFUSED",
+        }),
+      )
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-fetch-failed" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 10,
+    });
+
+    expect(result.id).toBe("dm-channel-fetch-failed");
+    expect(mockFetch).toHaveBeenCalledTimes(2);
+  });
+
+  it("does not retry on 4xx client errors (except 429)", async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: false,
+      status: 400,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ message: "Bad request" }),
+      text: async () => "Bad request",
+    } as Response);
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        maxRetries: 3,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow("400");
+
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not retry on 404 not found", async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: false,
+      status: 404,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ message: "User not found" }),
+      text: async () => "User not found",
+    } as Response);
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        maxRetries: 3,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow("404");
+
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+  });
+
+  it("throws after exhausting all retries", async () => {
+    mockFetch.mockResolvedValue({
+      ok: false,
+      status: 503,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ message: "Service unavailable" }),
+      text: async () => "Service unavailable",
+    } as Response);
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        maxRetries: 2,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow();
+
+    expect(mockFetch).toHaveBeenCalledTimes(3); // initial + 2 retries
+  });
+
+  it("respects custom timeout option and aborts fetch", async () => {
+    let abortSignal: AbortSignal | undefined;
+    let abortListenerCalled = false;
+
+    mockFetch.mockImplementationOnce((url, init) => {
+      abortSignal = init?.signal;
+      if (abortSignal) {
+        abortSignal.addEventListener("abort", () => {
+          abortListenerCalled = true;
+        });
+      }
+      // Return a promise that rejects when aborted, otherwise never resolves
+      return new Promise((_, reject) => {
+        if (abortSignal) {
+          const checkAbort = () => {
+            if (abortSignal?.aborted) {
+              reject(new Error("AbortError"));
+            } else {
+              setTimeout(checkAbort, 10);
+            }
+          };
+          setTimeout(checkAbort, 10);
+        }
+      });
+    });
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        timeoutMs: 50,
+        maxRetries: 0,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow();
+
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+    expect(abortSignal).toBeDefined();
+    expect(abortListenerCalled).toBe(true);
+  });
+
+  it("uses exponential backoff with jitter between retries", async () => {
+    const delays: number[] = [];
+    mockFetch
+      .mockRejectedValueOnce(new Error("Mattermost API 503 Service Unavailable"))
+      .mockRejectedValueOnce(new Error("Mattermost API 503 Service Unavailable"))
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-delay" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 100,
+      maxDelayMs: 1000,
+      onRetry: (attempt, delayMs) => {
+        delays.push(delayMs);
+      },
+    });
+
+    expect(delays).toHaveLength(2);
+    // First retry: exponentialDelay = 100ms, jitter = 0-100ms, total = 100-200ms
+    expect(delays[0]).toBeGreaterThanOrEqual(100);
+    expect(delays[0]).toBeLessThanOrEqual(200);
+    // Second retry: exponentialDelay = 200ms, jitter = 0-200ms, total = 200-400ms
+    expect(delays[1]).toBeGreaterThanOrEqual(200);
+    expect(delays[1]).toBeLessThanOrEqual(400);
+  });
+
+  it("respects maxDelayMs cap", async () => {
+    const delays: number[] = [];
+    mockFetch
+      .mockRejectedValueOnce(new Error("Mattermost API 503"))
+      .mockRejectedValueOnce(new Error("Mattermost API 503"))
+      .mockRejectedValueOnce(new Error("Mattermost API 503"))
+      .mockRejectedValueOnce(new Error("Mattermost API 503"))
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-max" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 4,
+      initialDelayMs: 1000,
+      maxDelayMs: 2500,
+      onRetry: (attempt, delayMs) => {
+        delays.push(delayMs);
+      },
+    });
+
+    expect(delays).toHaveLength(4);
+    // All delays should be capped at maxDelayMs
+    delays.forEach((delay) => {
+      expect(delay).toBeLessThanOrEqual(2500);
+    });
+  });
+
+  it("does not retry on 4xx errors even if message contains retryable keywords", async () => {
+    // This tests the fix for false positives where a 400 error with "timeout" in the message
+    // would incorrectly be retried
+    mockFetch.mockResolvedValueOnce({
+      ok: false,
+      status: 400,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ message: "Request timeout: connection timed out" }),
+      text: async () => "Request timeout: connection timed out",
+    } as Response);
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        maxRetries: 3,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow("400");
+
+    // Should not retry - only called once
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+  });
+
+  it("does not retry on 403 Forbidden even with 'abort' in message", async () => {
+    mockFetch.mockResolvedValueOnce({
+      ok: false,
+      status: 403,
+      headers: new Headers({ "content-type": "application/json" }),
+      json: async () => ({ message: "Request aborted: forbidden" }),
+      text: async () => "Request aborted: forbidden",
+    } as Response);
+
+    const client = createMockClient();
+
+    await expect(
+      createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+        maxRetries: 3,
+        initialDelayMs: 10,
+      }),
+    ).rejects.toThrow("403");
+
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+  });
+
+  it("passes AbortSignal to fetch for timeout support", async () => {
+    let capturedSignal: AbortSignal | undefined;
+    mockFetch.mockImplementationOnce((url, init) => {
+      capturedSignal = init?.signal;
+      return Promise.resolve({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-signal" }),
+      } as Response);
+    });
+
+    const client = createMockClient();
+    await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      timeoutMs: 5000,
+    });
+
+    expect(capturedSignal).toBeDefined();
+    expect(capturedSignal).toBeInstanceOf(AbortSignal);
+  });
+
+  it("retries on 5xx even if error message contains 4xx substring", async () => {
+    // This tests the fix for the ordering bug: 503 with "upstream 404" should be retried
+    mockFetch
+      .mockRejectedValueOnce(new Error("Mattermost API 503: upstream returned 404 Not Found"))
+      .mockResolvedValueOnce({
+        ok: true,
+        status: 201,
+        headers: new Headers({ "content-type": "application/json" }),
+        json: async () => ({ id: "dm-channel-5xx-with-404" }),
+      } as Response);
+
+    const client = createMockClient();
+
+    const result = await createMattermostDirectChannelWithRetry(client, ["user-1", "user-2"], {
+      maxRetries: 3,
+      initialDelayMs: 10,
+    });
+
+    // Should retry and succeed on second attempt
+    expect(mockFetch).toHaveBeenCalledTimes(2);
+    expect(result.id).toBe("dm-channel-5xx-with-404");
+  });
+});

extensions/mattermost/src/mattermost/client.ts

@@ -168,13 +168,270 @@ export async function sendMattermostTyping(
 export async function createMattermostDirectChannel(
   client: MattermostClient,
   userIds: string[],
+  signal?: AbortSignal,
 ): Promise<MattermostChannel> {
   return await client.request<MattermostChannel>("/channels/direct", {
     method: "POST",
     body: JSON.stringify(userIds),
+    signal,
   });
 }
 
+export type CreateDmChannelRetryOptions = {
+  /** Maximum number of retry attempts (default: 3) */
+  maxRetries?: number;
+  /** Initial delay in milliseconds (default: 1000) */
+  initialDelayMs?: number;
+  /** Maximum delay in milliseconds (default: 10000) */
+  maxDelayMs?: number;
+  /** Timeout for each individual request in milliseconds (default: 30000) */
+  timeoutMs?: number;
+  /** Optional logger for retry events */
+  onRetry?: (attempt: number, delayMs: number, error: Error) => void;
+};
+
+const RETRYABLE_NETWORK_ERROR_CODES = new Set([
+  "ECONNRESET",
+  "ECONNREFUSED",
+  "ETIMEDOUT",
+  "ESOCKETTIMEDOUT",
+  "ECONNABORTED",
+  "ENOTFOUND",
+  "EAI_AGAIN",
+  "EHOSTUNREACH",
+  "ENETUNREACH",
+  "EPIPE",
+  "UND_ERR_CONNECT_TIMEOUT",
+  "UND_ERR_DNS_RESOLVE_FAILED",
+  "UND_ERR_CONNECT",
+  "UND_ERR_SOCKET",
+  "UND_ERR_HEADERS_TIMEOUT",
+  "UND_ERR_BODY_TIMEOUT",
+]);
+
+const RETRYABLE_NETWORK_ERROR_NAMES = new Set([
+  "AbortError",
+  "TimeoutError",
+  "ConnectTimeoutError",
+  "HeadersTimeoutError",
+  "BodyTimeoutError",
+]);
+
+const RETRYABLE_NETWORK_MESSAGE_SNIPPETS = [
+  "network error",
+  "timeout",
+  "timed out",
+  "abort",
+  "connection refused",
+  "econnreset",
+  "econnrefused",
+  "etimedout",
+  "enotfound",
+  "socket hang up",
+  "getaddrinfo",
+];
+
+/**
+ * Creates a Mattermost DM channel with exponential backoff retry logic.
+ * Retries on transient errors (429, 5xx, network errors) but not on
+ * client errors (4xx except 429) or permanent failures.
+ */
+export async function createMattermostDirectChannelWithRetry(
+  client: MattermostClient,
+  userIds: string[],
+  options: CreateDmChannelRetryOptions = {},
+): Promise<MattermostChannel> {
+  const {
+    maxRetries = 3,
+    initialDelayMs = 1000,
+    maxDelayMs = 10000,
+    timeoutMs = 30000,
+    onRetry,
+  } = options;
+
+  let lastError: Error | undefined;
+
+  for (let attempt = 0; attempt <= maxRetries; attempt++) {
+    try {
+      // Use AbortController for per-request timeout
+      const controller = new AbortController();
+      const timeoutId = setTimeout(() => controller.abort(), timeoutMs);
+
+      try {
+        const result = await createMattermostDirectChannel(client, userIds, controller.signal);
+        return result;
+      } finally {
+        clearTimeout(timeoutId);
+      }
+    } catch (err) {
+      lastError = err instanceof Error ? err : new Error(String(err));
+
+      // Don't retry on the last attempt
+      if (attempt >= maxRetries) {
+        break;
+      }
+
+      // Check if error is retryable
+      if (!isRetryableError(lastError)) {
+        throw lastError;
+      }
+
+      // Calculate exponential backoff delay with full-jitter
+      // Jitter is proportional to the exponential delay, not a fixed 1000ms
+      // This ensures backoff behaves correctly for small delay configurations
+      const exponentialDelay = initialDelayMs * Math.pow(2, attempt);
+      const jitter = Math.random() * exponentialDelay;
+      const delayMs = Math.min(exponentialDelay + jitter, maxDelayMs);
+
+      if (onRetry) {
+        onRetry(attempt + 1, delayMs, lastError);
+      }
+
+      // Wait before retrying
+      await sleep(delayMs);
+    }
+  }
+
+  throw lastError ?? new Error("Failed to create DM channel after retries");
+}
+
+function isRetryableError(error: Error): boolean {
+  const candidates = collectErrorCandidates(error);
+  const messages = candidates
+    .map((candidate) => readErrorMessage(candidate)?.toLowerCase())
+    .filter((message): message is string => Boolean(message));
+
+  // Retry on 5xx server errors FIRST (before checking 4xx)
+  // Use "mattermost api" prefix to avoid matching port numbers (e.g., :443) or IP octets
+  // This prevents misclassification when a 5xx error detail contains a 4xx substring
+  // e.g., "Mattermost API 503: upstream returned 404"
+  if (messages.some((message) => /mattermost api 5\d{2}\b/.test(message))) {
+    return true;
+  }
+
+  // Check for explicit 429 rate limiting FIRST (before generic "429" text match)
+  // This avoids retrying when error detail contains "429" but it's not the status code
+  if (
+    messages.some(
+      (message) => /mattermost api 429\b/.test(message) || message.includes("too many requests"),
+    )
+  ) {
+    return true;
+  }
+
+  // Check for explicit 4xx status codes - these are client errors and should NOT be retried
+  // (except 429 which is handled above)
+  // Use "mattermost api" prefix to avoid matching port numbers like :443
+  for (const message of messages) {
+    const clientErrorMatch = message.match(/mattermost api (4\d{2})\b/);
+    if (!clientErrorMatch) {
+      continue;
+    }
+    const statusCode = parseInt(clientErrorMatch[1], 10);
+    if (statusCode >= 400 && statusCode < 500) {
+      return false;
+    }
+  }
+
+  // Retry on network/transient errors only if no explicit Mattermost API status code is present
+  // This avoids false positives like:
+  // - "400 Bad Request: connection timed out" (has status code)
+  // - "connect ECONNRESET 104.18.32.10:443" (has port number, not status)
+  const hasMattermostApiStatusCode = messages.some((message) =>
+    /mattermost api \d{3}\b/.test(message),
+  );
+  if (hasMattermostApiStatusCode) {
+    return false;
+  }
+
+  const codes = candidates
+    .map((candidate) => readErrorCode(candidate))
+    .filter((code): code is string => Boolean(code));
+  if (codes.some((code) => RETRYABLE_NETWORK_ERROR_CODES.has(code))) {
+    return true;
+  }
+
+  const names = candidates
+    .map((candidate) => readErrorName(candidate))
+    .filter((name): name is string => Boolean(name));
+  if (names.some((name) => RETRYABLE_NETWORK_ERROR_NAMES.has(name))) {
+    return true;
+  }
+
+  return messages.some((message) =>
+    RETRYABLE_NETWORK_MESSAGE_SNIPPETS.some((pattern) => message.includes(pattern)),
+  );
+}
+
+function collectErrorCandidates(error: unknown): unknown[] {
+  const queue: unknown[] = [error];
+  const seen = new Set<unknown>();
+  const candidates: unknown[] = [];
+
+  while (queue.length > 0) {
+    const current = queue.shift();
+    if (!current || seen.has(current)) {
+      continue;
+    }
+    seen.add(current);
+    candidates.push(current);
+
+    if (typeof current !== "object") {
+      continue;
+    }
+
+    const nested = current as {
+      cause?: unknown;
+      reason?: unknown;
+      errors?: unknown;
+    };
+    queue.push(nested.cause, nested.reason);
+    if (Array.isArray(nested.errors)) {
+      queue.push(...nested.errors);
+    }
+  }
+
+  return candidates;
+}
+
+function readErrorMessage(error: unknown): string | undefined {
+  if (!error || typeof error !== "object") {
+    return undefined;
+  }
+  const message = (error as { message?: unknown }).message;
+  return typeof message === "string" && message.trim() ? message : undefined;
+}
+
+function readErrorName(error: unknown): string | undefined {
+  if (!error || typeof error !== "object") {
+    return undefined;
+  }
+  const name = (error as { name?: unknown }).name;
+  return typeof name === "string" && name.trim() ? name : undefined;
+}
+
+function readErrorCode(error: unknown): string | undefined {
+  if (!error || typeof error !== "object") {
+    return undefined;
+  }
+  const { code, errno } = error as {
+    code?: unknown;
+    errno?: unknown;
+  };
+  const raw = typeof code === "string" && code.trim() ? code : errno;
+  if (typeof raw === "string" && raw.trim()) {
+    return raw.trim().toUpperCase();
+  }
+  if (typeof raw === "number" && Number.isFinite(raw)) {
+    return String(raw);
+  }
+  return undefined;
+}
+
+function sleep(ms: number): Promise<void> {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
 export async function createMattermostPost(
   client: MattermostClient,
   params: {

extensions/mattermost/src/mattermost/send.test.ts

@@ -13,9 +13,11 @@ const mockState = vi.hoisted(() => ({
     accountId: "default",
     botToken: "bot-token",
     baseUrl: "https://mattermost.example.com",
+    config: {},
   })),
   createMattermostClient: vi.fn(),
   createMattermostDirectChannel: vi.fn(),
+  createMattermostDirectChannelWithRetry: vi.fn(),
   createMattermostPost: vi.fn(),
   fetchMattermostChannelByName: vi.fn(),
   fetchMattermostMe: vi.fn(),
@@ -37,6 +39,7 @@ vi.mock("./accounts.js", () => ({
 vi.mock("./client.js", () => ({
   createMattermostClient: mockState.createMattermostClient,
   createMattermostDirectChannel: mockState.createMattermostDirectChannel,
+  createMattermostDirectChannelWithRetry: mockState.createMattermostDirectChannelWithRetry,
   createMattermostPost: mockState.createMattermostPost,
   fetchMattermostChannelByName: mockState.fetchMattermostChannelByName,
   fetchMattermostMe: mockState.fetchMattermostMe,
@@ -77,10 +80,12 @@ describe("sendMessageMattermost", () => {
       accountId: "default",
       botToken: "bot-token",
       baseUrl: "https://mattermost.example.com",
+      config: {},
     });
     mockState.loadOutboundMediaFromUrl.mockReset();
     mockState.createMattermostClient.mockReset();
     mockState.createMattermostDirectChannel.mockReset();
+    mockState.createMattermostDirectChannelWithRetry.mockReset();
     mockState.createMattermostPost.mockReset();
     mockState.fetchMattermostChannelByName.mockReset();
     mockState.fetchMattermostMe.mockReset();
@@ -91,6 +96,7 @@ describe("sendMessageMattermost", () => {
     resetMattermostOpaqueTargetCacheForTests();
     mockState.createMattermostClient.mockReturnValue({});
     mockState.createMattermostPost.mockResolvedValue({ id: "post-1" });
+    mockState.createMattermostDirectChannelWithRetry.mockResolvedValue({ id: "dm-channel-1" });
     mockState.fetchMattermostMe.mockResolvedValue({ id: "bot-user" });
     mockState.fetchMattermostUserTeams.mockResolvedValue([{ id: "team-1" }]);
     mockState.fetchMattermostChannelByName.mockResolvedValue({ id: "town-square" });
@@ -105,6 +111,12 @@ describe("sendMessageMattermost", () => {
         },
       },
     };
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "work",
+      botToken: "provided-token",
+      baseUrl: "https://mattermost.example.com",
+      config: {},
+    });
 
     await sendMessageMattermost("channel:town-square", "hello", {
       cfg: providedCfg as any,
@@ -128,6 +140,12 @@ describe("sendMessageMattermost", () => {
       },
     };
     mockState.loadConfig.mockReturnValueOnce(runtimeCfg);
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "runtime-token",
+      baseUrl: "https://mattermost.example.com",
+      config: {},
+    });
 
     await sendMessageMattermost("channel:town-square", "hello");
 
@@ -146,6 +164,12 @@ describe("sendMessageMattermost", () => {
       contentType: "image/png",
       kind: "image",
     });
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "bot-token",
+      baseUrl: "https://mattermost.example.com",
+      config: {},
+    });
 
     await sendMessageMattermost("channel:town-square", "hello", {
       mediaUrl: "file:///tmp/agent-workspace/photo.png",
@@ -169,6 +193,13 @@ describe("sendMessageMattermost", () => {
   });
 
   it("builds interactive button props when buttons are provided", async () => {
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "bot-token",
+      baseUrl: "https://mattermost.example.com",
+      config: {},
+    });
+
     await sendMessageMattermost("channel:town-square", "Pick a model", {
       buttons: [[{ callback_data: "mdlprov", text: "Browse providers" }]],
     });
@@ -196,8 +227,13 @@ describe("sendMessageMattermost", () => {
 
   it("resolves a bare Mattermost user id as a DM target before upload", async () => {
     const userId = "dthcxgoxhifn3pwh65cut3ud3w";
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "bot-token",
+      baseUrl: "https://mattermost.example.com",
+      config: {},
+    });
     mockState.fetchMattermostUser.mockResolvedValueOnce({ id: userId });
-    mockState.createMattermostDirectChannel.mockResolvedValueOnce({ id: "dm-channel-1" });
     mockState.loadOutboundMediaFromUrl.mockResolvedValueOnce({
       buffer: Buffer.from("media-bytes"),
       fileName: "photo.png",
@@ -211,7 +247,11 @@ describe("sendMessageMattermost", () => {
     });
 
     expect(mockState.fetchMattermostUser).toHaveBeenCalledWith({}, userId);
-    expect(mockState.createMattermostDirectChannel).toHaveBeenCalledWith({}, ["bot-user", userId]);
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledWith(
+      {},
+      ["bot-user", userId],
+      expect.any(Object),
+    );
     expect(mockState.uploadMattermostFile).toHaveBeenCalledWith(
       {},
       expect.objectContaining({
@@ -223,6 +263,12 @@ describe("sendMessageMattermost", () => {
 
   it("falls back to a channel target when bare Mattermost id is not a user", async () => {
     const channelId = "aaaaaaaaaaaaaaaaaaaaaaaaaa";
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "bot-token",
+      baseUrl: "https://mattermost.example.com",
+      config: {},
+    });
     mockState.fetchMattermostUser.mockRejectedValueOnce(
       new Error("Mattermost API 404 Not Found: user not found"),
     );
@@ -239,7 +285,7 @@ describe("sendMessageMattermost", () => {
     });
 
     expect(mockState.fetchMattermostUser).toHaveBeenCalledWith({}, channelId);
-    expect(mockState.createMattermostDirectChannel).not.toHaveBeenCalled();
+    expect(mockState.createMattermostDirectChannelWithRetry).not.toHaveBeenCalled();
     expect(mockState.uploadMattermostFile).toHaveBeenCalledWith(
       {},
       expect.objectContaining({
@@ -337,11 +383,12 @@ describe("parseMattermostTarget", () => {
 // userIdResolutionCache and dmChannelCache are module singletons that survive across tests.
 // Using unique cache keys per test ensures full isolation without needing a cache reset API.
 describe("sendMessageMattermost user-first resolution", () => {
-  function makeAccount(token: string) {
+  function makeAccount(token: string, config = {}) {
     return {
       accountId: "default",
       botToken: token,
       baseUrl: "https://mattermost.example.com",
+      config,
     };
   }
 
@@ -350,6 +397,7 @@ describe("sendMessageMattermost user-first resolution", () => {
     mockState.createMattermostClient.mockReturnValue({});
     mockState.createMattermostPost.mockResolvedValue({ id: "post-id" });
     mockState.createMattermostDirectChannel.mockResolvedValue({ id: "dm-channel-id" });
+    mockState.createMattermostDirectChannelWithRetry.mockResolvedValue({ id: "dm-channel-id" });
     mockState.fetchMattermostMe.mockResolvedValue({ id: "bot-id" });
   });
 
@@ -362,7 +410,7 @@ describe("sendMessageMattermost user-first resolution", () => {
     const res = await sendMessageMattermost(userId, "hello");
 
     expect(mockState.fetchMattermostUser).toHaveBeenCalledTimes(1);
-    expect(mockState.createMattermostDirectChannel).toHaveBeenCalledTimes(1);
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledTimes(1);
     const params = mockState.createMattermostPost.mock.calls[0]?.[1];
     expect(params.channelId).toBe("dm-channel-id");
     expect(res.channelId).toBe("dm-channel-id");
@@ -379,7 +427,7 @@ describe("sendMessageMattermost user-first resolution", () => {
     const res = await sendMessageMattermost(channelId, "hello");
 
     expect(mockState.fetchMattermostUser).toHaveBeenCalledTimes(1);
-    expect(mockState.createMattermostDirectChannel).not.toHaveBeenCalled();
+    expect(mockState.createMattermostDirectChannelWithRetry).not.toHaveBeenCalled();
     const params = mockState.createMattermostPost.mock.calls[0]?.[1];
     expect(params.channelId).toBe(channelId);
     expect(res.channelId).toBe(channelId);
@@ -403,7 +451,7 @@ describe("sendMessageMattermost user-first resolution", () => {
     vi.clearAllMocks();
     mockState.createMattermostClient.mockReturnValue({});
     mockState.createMattermostPost.mockResolvedValue({ id: "post-id-2" });
-    mockState.createMattermostDirectChannel.mockResolvedValue({ id: "dm-channel-id" });
+    mockState.createMattermostDirectChannelWithRetry.mockResolvedValue({ id: "dm-channel-id" });
     mockState.fetchMattermostMe.mockResolvedValue({ id: "bot-id" });
     mockState.resolveMattermostAccount.mockReturnValue(makeAccount(tokenB));
     mockState.fetchMattermostUser.mockResolvedValueOnce({ id: userId });
@@ -417,11 +465,12 @@ describe("sendMessageMattermost user-first resolution", () => {
     // Unique token + id — explicit user: prefix bypasses probe, goes straight to DM
     const userId = "dddddd4444444444dddddd4444"; // 26 chars
     mockState.resolveMattermostAccount.mockReturnValue(makeAccount("token-explicit-user-t4"));
+    mockState.createMattermostDirectChannelWithRetry.mockResolvedValue({ id: "dm-channel-id" });
 
     const res = await sendMessageMattermost(`user:${userId}`, "hello");
 
     expect(mockState.fetchMattermostUser).not.toHaveBeenCalled();
-    expect(mockState.createMattermostDirectChannel).toHaveBeenCalledTimes(1);
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledTimes(1);
     expect(res.channelId).toBe("dm-channel-id");
   });
 
@@ -433,9 +482,101 @@ describe("sendMessageMattermost user-first resolution", () => {
     const res = await sendMessageMattermost(`channel:${chanId}`, "hello");
 
     expect(mockState.fetchMattermostUser).not.toHaveBeenCalled();
-    expect(mockState.createMattermostDirectChannel).not.toHaveBeenCalled();
+    expect(mockState.createMattermostDirectChannelWithRetry).not.toHaveBeenCalled();
     const params = mockState.createMattermostPost.mock.calls[0]?.[1];
     expect(params.channelId).toBe(chanId);
     expect(res.channelId).toBe(chanId);
   });
+
+  it("passes dmRetryOptions from opts to createMattermostDirectChannelWithRetry", async () => {
+    const userId = "ffffff6666666666ffffff6666"; // 26 chars
+    mockState.resolveMattermostAccount.mockReturnValue(makeAccount("token-retry-opts-t6"));
+    mockState.fetchMattermostUser.mockResolvedValueOnce({ id: userId });
+
+    const retryOptions = {
+      maxRetries: 5,
+      initialDelayMs: 500,
+      maxDelayMs: 5000,
+      timeoutMs: 10000,
+    };
+
+    await sendMessageMattermost(`user:${userId}`, "hello", {
+      dmRetryOptions: retryOptions,
+    });
+
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledWith(
+      {},
+      ["bot-id", userId],
+      expect.objectContaining(retryOptions),
+    );
+  });
+
+  it("uses dmChannelRetry from account config when opts.dmRetryOptions not provided", async () => {
+    const userId = "gggggg7777777777gggggg7777"; // 26 chars
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "token-retry-config-t7",
+      baseUrl: "https://mattermost.example.com",
+      config: {
+        dmChannelRetry: {
+          maxRetries: 4,
+          initialDelayMs: 2000,
+          maxDelayMs: 8000,
+          timeoutMs: 15000,
+        },
+      },
+    });
+    mockState.fetchMattermostUser.mockResolvedValueOnce({ id: userId });
+
+    await sendMessageMattermost(`user:${userId}`, "hello");
+
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledWith(
+      {},
+      ["bot-id", userId],
+      expect.objectContaining({
+        maxRetries: 4,
+        initialDelayMs: 2000,
+        maxDelayMs: 8000,
+        timeoutMs: 15000,
+      }),
+    );
+  });
+
+  it("opts.dmRetryOptions overrides provided fields and preserves account defaults", async () => {
+    const userId = "hhhhhh8888888888hhhhhh8888"; // 26 chars
+    mockState.resolveMattermostAccount.mockReturnValue({
+      accountId: "default",
+      botToken: "token-retry-override-t8",
+      baseUrl: "https://mattermost.example.com",
+      config: {
+        dmChannelRetry: {
+          maxRetries: 2,
+          initialDelayMs: 1000,
+        },
+      },
+    });
+    mockState.fetchMattermostUser.mockResolvedValueOnce({ id: userId });
+
+    const overrideOptions = {
+      maxRetries: 7,
+      timeoutMs: 20000,
+    };
+
+    await sendMessageMattermost(`user:${userId}`, "hello", {
+      dmRetryOptions: overrideOptions,
+    });
+
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledWith(
+      {},
+      ["bot-id", userId],
+      expect.objectContaining(overrideOptions),
+    );
+    expect(mockState.createMattermostDirectChannelWithRetry).toHaveBeenCalledWith(
+      {},
+      ["bot-id", userId],
+      expect.objectContaining({
+        initialDelayMs: 1000,
+      }),
+    );
+  });
 });

extensions/mattermost/src/mattermost/send.ts

@@ -3,7 +3,7 @@ import { getMattermostRuntime } from "../runtime.js";
 import { resolveMattermostAccount } from "./accounts.js";
 import {
   createMattermostClient,
-  createMattermostDirectChannel,
+  createMattermostDirectChannelWithRetry,
   createMattermostPost,
   fetchMattermostChannelByName,
   fetchMattermostMe,
@@ -12,6 +12,7 @@ import {
   normalizeMattermostBaseUrl,
   uploadMattermostFile,
   type MattermostUser,
+  type CreateDmChannelRetryOptions,
 } from "./client.js";
 import {
   buildButtonProps,
@@ -32,6 +33,8 @@ export type MattermostSendOpts = {
   props?: Record<string, unknown>;
   buttons?: Array<unknown>;
   attachmentText?: string;
+  /** Retry options for DM channel creation */
+  dmRetryOptions?: CreateDmChannelRetryOptions;
 };
 
 export type MattermostSendResult = {
@@ -182,11 +185,40 @@ async function resolveChannelIdByName(params: {
   throw new Error(`Mattermost channel "#${name}" not found in any team the bot belongs to`);
 }
 
-async function resolveTargetChannelId(params: {
+type ResolveTargetChannelIdParams = {
   target: MattermostTarget;
   baseUrl: string;
   token: string;
-}): Promise<string> {
+  dmRetryOptions?: CreateDmChannelRetryOptions;
+  logger?: { debug?: (msg: string) => void; warn?: (msg: string) => void };
+};
+
+function mergeDmRetryOptions(
+  base?: CreateDmChannelRetryOptions,
+  override?: CreateDmChannelRetryOptions,
+): CreateDmChannelRetryOptions | undefined {
+  const merged: CreateDmChannelRetryOptions = {
+    maxRetries: override?.maxRetries ?? base?.maxRetries,
+    initialDelayMs: override?.initialDelayMs ?? base?.initialDelayMs,
+    maxDelayMs: override?.maxDelayMs ?? base?.maxDelayMs,
+    timeoutMs: override?.timeoutMs ?? base?.timeoutMs,
+    onRetry: override?.onRetry,
+  };
+
+  if (
+    merged.maxRetries === undefined &&
+    merged.initialDelayMs === undefined &&
+    merged.maxDelayMs === undefined &&
+    merged.timeoutMs === undefined &&
+    merged.onRetry === undefined
+  ) {
+    return undefined;
+  }
+
+  return merged;
+}
+
+async function resolveTargetChannelId(params: ResolveTargetChannelIdParams): Promise<string> {
   if (params.target.kind === "channel") {
     return params.target.id;
   }
@@ -214,7 +246,20 @@ async function resolveTargetChannelId(params: {
     baseUrl: params.baseUrl,
     botToken: params.token,
   });
-  const channel = await createMattermostDirectChannel(client, [botUser.id, userId]);
+
+  const channel = await createMattermostDirectChannelWithRetry(client, [botUser.id, userId], {
+    ...params.dmRetryOptions,
+    onRetry: (attempt, delayMs, error) => {
+      // Call user's onRetry if provided
+      params.dmRetryOptions?.onRetry?.(attempt, delayMs, error);
+      // Log if verbose mode is enabled
+      if (params.logger) {
+        params.logger.warn?.(
+          `DM channel creation retry ${attempt} after ${delayMs}ms: ${error.message}`,
+        );
+      }
+    },
+  });
   dmChannelCache.set(dmKey, channel.id);
   return channel.id;
 }
@@ -232,6 +277,7 @@ async function resolveMattermostSendContext(
   opts: MattermostSendOpts = {},
 ): Promise<MattermostSendContext> {
   const core = getCore();
+  const logger = core.logging.getChildLogger({ module: "mattermost" });
   const cfg = opts.cfg ?? core.config.loadConfig();
   const account = resolveMattermostAccount({
     cfg,
@@ -262,10 +308,23 @@ async function resolveMattermostSendContext(
       : opaqueTarget?.kind === "channel"
         ? { kind: "channel" as const, id: opaqueTarget.id }
         : parseMattermostTarget(trimmedTo);
+  // Build retry options from account config, allowing opts to override
+  const accountRetryConfig: CreateDmChannelRetryOptions | undefined = account.config.dmChannelRetry
+    ? {
+        maxRetries: account.config.dmChannelRetry.maxRetries,
+        initialDelayMs: account.config.dmChannelRetry.initialDelayMs,
+        maxDelayMs: account.config.dmChannelRetry.maxDelayMs,
+        timeoutMs: account.config.dmChannelRetry.timeoutMs,
+      }
+    : undefined;
+  const dmRetryOptions = mergeDmRetryOptions(accountRetryConfig, opts.dmRetryOptions);
+
   const channelId = await resolveTargetChannelId({
     target,
     baseUrl,
     token,
+    dmRetryOptions,
+    logger: core.logging.shouldLogVerbose() ? logger : undefined,
   });
 
   return {

extensions/mattermost/src/types.ts

@@ -90,6 +90,17 @@ export type MattermostAccountConfig = {
      */
     allowedSourceIps?: string[];
   };
+  /** Retry configuration for DM channel creation */
+  dmChannelRetry?: {
+    /** Maximum number of retry attempts (default: 3) */
+    maxRetries?: number;
+    /** Initial delay in milliseconds before first retry (default: 1000) */
+    initialDelayMs?: number;
+    /** Maximum delay in milliseconds between retries (default: 10000) */
+    maxDelayMs?: number;
+    /** Timeout for each individual request in milliseconds (default: 30000) */
+    timeoutMs?: number;
+  };
 };
 
 export type MattermostConfig = {