diff --git a/src/__tests__/db-utils.test.ts b/src/__tests__/db-utils.test.ts
index ca8323f..12b5faa 100644
--- a/src/__tests__/db-utils.test.ts
+++ b/src/__tests__/db-utils.test.ts
@@ -1,11 +1,18 @@
 import { describe, it, expect } from "vitest";
 import { isTransientError } from "../utils/errors.js";
 
+/** Create an Error with a `.code` property (like Node/pg errors) */
+function makeError(opts: { code?: string; message?: string }): Error {
+  const err = new Error(opts.message || "");
+  if (opts.code) (err as Error & { code: string }).code = opts.code;
+  return err;
+}
+
 describe("isTransientError", () => {
   describe("transient error codes", () => {
     for (const code of ["ECONNRESET", "ECONNREFUSED", "EPIPE", "ETIMEDOUT", "CONNECTION_LOST", "57P01", "57P02", "57P03", "08006", "08003", "08001"]) {
       it(`detects code ${code}`, () => {
-        expect(isTransientError({ code })).toBe(true);
+        expect(isTransientError(makeError({ code }))).toBe(true);
       });
     }
   });
@@ -20,7 +27,7 @@ describe("isTransientError", () => {
 
   describe("non-transient errors", () => {
     it("rejects generic error", () => expect(isTransientError(new Error("something broke"))).toBe(false));
-    it("rejects SQL syntax error", () => expect(isTransientError({ code: "42601", message: "syntax error" })).toBe(false));
+    it("rejects SQL syntax error", () => expect(isTransientError(makeError({ code: "42601", message: "syntax error" }))).toBe(false));
   });
 
   describe("null/undefined input", () => {
@@ -29,8 +36,9 @@ describe("isTransientError", () => {
   });
 
   describe("partial error objects", () => {
-    it("handles error with code but no message", () => expect(isTransientError({ code: "ECONNRESET" })).toBe(true));
-    it("handles error with message but no code", () => expect(isTransientError({ message: "connection terminated" })).toBe(true));
-    it("rejects error with unrelated code and no message", () => expect(isTransientError({ code: "UNKNOWN" })).toBe(false));
+    it("handles Error with code but no message", () => expect(isTransientError(makeError({ code: "ECONNRESET" }))).toBe(true));
+    it("handles Error with message but no code", () => expect(isTransientError(new Error("connection terminated"))).toBe(true));
+    it("rejects Error with unrelated code and no message", () => expect(isTransientError(makeError({ code: "UNKNOWN" }))).toBe(false));
+    it("rejects plain object (not an Error instance)", () => expect(isTransientError({ code: "ECONNRESET" })).toBe(false));
   });
 });
diff --git a/src/__tests__/error-type-safety.test.ts b/src/__tests__/error-type-safety.test.ts
new file mode 100644
index 0000000..033473a
--- /dev/null
+++ b/src/__tests__/error-type-safety.test.ts
@@ -0,0 +1,84 @@
+import { describe, it, expect } from "vitest";
+import { isTransientError, errorMessage, errorCode } from "../utils/errors.js";
+
+describe("error type safety — unknown error types", () => {
+  describe("isTransientError with non-Error objects", () => {
+    it("handles string thrown as error", () => {
+      expect(isTransientError("connection refused")).toBe(false);
+    });
+
+    it("handles null thrown as error", () => {
+      expect(isTransientError(null)).toBe(false);
+    });
+
+    it("handles undefined thrown as error", () => {
+      expect(isTransientError(undefined)).toBe(false);
+    });
+
+    it("handles number thrown as error", () => {
+      expect(isTransientError(42)).toBe(false);
+    });
+
+    it("handles plain object with code property", () => {
+      expect(isTransientError({ code: "ECONNRESET" })).toBe(false);
+    });
+
+    it("handles Error with transient code", () => {
+      const err = new Error("connection reset");
+      (err as any).code = "ECONNRESET";
+      expect(isTransientError(err)).toBe(true);
+    });
+
+    it("handles Error with transient message", () => {
+      const err = new Error("Connection terminated unexpectedly");
+      expect(isTransientError(err)).toBe(true);
+    });
+
+    it("handles Error with non-transient message", () => {
+      const err = new Error("syntax error at position 42");
+      expect(isTransientError(err)).toBe(false);
+    });
+  });
+
+  describe("errorMessage", () => {
+    it("extracts message from Error", () => {
+      expect(errorMessage(new Error("test"))).toBe("test");
+    });
+
+    it("returns string directly", () => {
+      expect(errorMessage("raw string error")).toBe("raw string error");
+    });
+
+    it("stringifies null", () => {
+      expect(errorMessage(null)).toBe("null");
+    });
+
+    it("stringifies number", () => {
+      expect(errorMessage(42)).toBe("42");
+    });
+
+    it("stringifies undefined", () => {
+      expect(errorMessage(undefined)).toBe("undefined");
+    });
+  });
+
+  describe("errorCode", () => {
+    it("extracts code from Error with code", () => {
+      const err = new Error("fail");
+      (err as any).code = "ECONNRESET";
+      expect(errorCode(err)).toBe("ECONNRESET");
+    });
+
+    it("returns undefined for Error without code", () => {
+      expect(errorCode(new Error("fail"))).toBeUndefined();
+    });
+
+    it("returns undefined for non-Error", () => {
+      expect(errorCode("string")).toBeUndefined();
+    });
+
+    it("returns undefined for null", () => {
+      expect(errorCode(null)).toBeUndefined();
+    });
+  });
+});
diff --git a/src/__tests__/errors.test.ts b/src/__tests__/errors.test.ts
index 7d42e79..a4fc297 100644
--- a/src/__tests__/errors.test.ts
+++ b/src/__tests__/errors.test.ts
@@ -1,6 +1,13 @@
 import { describe, it, expect } from "vitest";
 import { isTransientError } from "../utils/errors.js";
 
+/** Create an Error with a `.code` property (like Node/pg errors) */
+function makeError(opts: { code?: string; message?: string }): Error {
+  const err = new Error(opts.message || "");
+  if (opts.code) (err as Error & { code: string }).code = opts.code;
+  return err;
+}
+
 describe("isTransientError", () => {
   describe("null/undefined/empty input", () => {
     it("returns false for null", () => {
@@ -11,189 +18,191 @@ describe("isTransientError", () => {
       expect(isTransientError(undefined)).toBe(false);
     });
 
-    it("returns false for empty object", () => {
+    it("returns false for empty object (not an Error)", () => {
       expect(isTransientError({})).toBe(false);
     });
+
+    it("returns false for plain string", () => {
+      expect(isTransientError("ECONNRESET")).toBe(false);
+    });
   });
 
   describe("error codes from TRANSIENT_ERRORS set", () => {
     it("returns true for ECONNRESET", () => {
-      expect(isTransientError({ code: "ECONNRESET" })).toBe(true);
+      expect(isTransientError(makeError({ code: "ECONNRESET" }))).toBe(true);
     });
 
     it("returns true for ECONNREFUSED", () => {
-      expect(isTransientError({ code: "ECONNREFUSED" })).toBe(true);
+      expect(isTransientError(makeError({ code: "ECONNREFUSED" }))).toBe(true);
     });
 
     it("returns true for EPIPE", () => {
-      expect(isTransientError({ code: "EPIPE" })).toBe(true);
+      expect(isTransientError(makeError({ code: "EPIPE" }))).toBe(true);
     });
 
     it("returns true for ETIMEDOUT", () => {
-      expect(isTransientError({ code: "ETIMEDOUT" })).toBe(true);
+      expect(isTransientError(makeError({ code: "ETIMEDOUT" }))).toBe(true);
     });
 
     it("returns true for CONNECTION_LOST", () => {
-      expect(isTransientError({ code: "CONNECTION_LOST" })).toBe(true);
+      expect(isTransientError(makeError({ code: "CONNECTION_LOST" }))).toBe(true);
     });
 
     it("returns true for 57P01 (admin_shutdown)", () => {
-      expect(isTransientError({ code: "57P01" })).toBe(true);
+      expect(isTransientError(makeError({ code: "57P01" }))).toBe(true);
     });
 
     it("returns true for 57P02 (crash_shutdown)", () => {
-      expect(isTransientError({ code: "57P02" })).toBe(true);
+      expect(isTransientError(makeError({ code: "57P02" }))).toBe(true);
     });
 
     it("returns true for 57P03 (cannot_connect_now)", () => {
-      expect(isTransientError({ code: "57P03" })).toBe(true);
+      expect(isTransientError(makeError({ code: "57P03" }))).toBe(true);
     });
 
     it("returns true for 08006 (connection_failure)", () => {
-      expect(isTransientError({ code: "08006" })).toBe(true);
+      expect(isTransientError(makeError({ code: "08006" }))).toBe(true);
     });
 
     it("returns true for 08003 (connection_does_not_exist)", () => {
-      expect(isTransientError({ code: "08003" })).toBe(true);
+      expect(isTransientError(makeError({ code: "08003" }))).toBe(true);
     });
 
     it("returns true for 08001 (sqlclient_unable_to_establish_sqlconnection)", () => {
-      expect(isTransientError({ code: "08001" })).toBe(true);
+      expect(isTransientError(makeError({ code: "08001" }))).toBe(true);
     });
   });
 
   describe("message substring matching", () => {
     it("returns true for 'no available server'", () => {
-      expect(isTransientError({ message: "no available server" })).toBe(true);
+      expect(isTransientError(new Error("no available server"))).toBe(true);
     });
 
     it("returns true for 'connection terminated'", () => {
-      expect(isTransientError({ message: "connection terminated unexpectedly" })).toBe(true);
+      expect(isTransientError(new Error("connection terminated unexpectedly"))).toBe(true);
     });
 
     it("returns true for 'connection refused'", () => {
-      expect(isTransientError({ message: "connection refused by server" })).toBe(true);
+      expect(isTransientError(new Error("connection refused by server"))).toBe(true);
     });
 
     it("returns true for 'server closed the connection'", () => {
-      expect(isTransientError({ message: "server closed the connection unexpectedly" })).toBe(true);
+      expect(isTransientError(new Error("server closed the connection unexpectedly"))).toBe(true);
     });
 
     it("returns true for 'timeout expired'", () => {
-      expect(isTransientError({ message: "timeout expired waiting for connection" })).toBe(true);
+      expect(isTransientError(new Error("timeout expired waiting for connection"))).toBe(true);
     });
   });
 
   describe("case-insensitive message matching", () => {
     it("returns true for 'No Available Server' (mixed case)", () => {
-      expect(isTransientError({ message: "No Available Server" })).toBe(true);
+      expect(isTransientError(new Error("No Available Server"))).toBe(true);
     });
 
     it("returns true for 'CONNECTION TERMINATED' (uppercase)", () => {
-      expect(isTransientError({ message: "CONNECTION TERMINATED" })).toBe(true);
+      expect(isTransientError(new Error("CONNECTION TERMINATED"))).toBe(true);
     });
 
     it("returns true for 'Connection Refused' (title case)", () => {
-      expect(isTransientError({ message: "Connection Refused" })).toBe(true);
+      expect(isTransientError(new Error("Connection Refused"))).toBe(true);
     });
 
     it("returns true for 'SERVER CLOSED THE CONNECTION' (uppercase)", () => {
-      expect(isTransientError({ message: "SERVER CLOSED THE CONNECTION" })).toBe(true);
+      expect(isTransientError(new Error("SERVER CLOSED THE CONNECTION"))).toBe(true);
     });
 
     it("returns true for 'Timeout Expired' (title case)", () => {
-      expect(isTransientError({ message: "Timeout Expired" })).toBe(true);
+      expect(isTransientError(new Error("Timeout Expired"))).toBe(true);
     });
   });
 
   describe("non-transient errors", () => {
     it("returns false for syntax error", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "42601", 
         message: "syntax error at or near SELECT" 
-      })).toBe(false);
+      }))).toBe(false);
     });
 
     it("returns false for unique constraint violation", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "23505", 
         message: "duplicate key value violates unique constraint" 
-      })).toBe(false);
+      }))).toBe(false);
     });
 
     it("returns false for foreign key violation", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "23503", 
         message: "foreign key constraint violation" 
-      })).toBe(false);
+      }))).toBe(false);
     });
 
     it("returns false for not null violation", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "23502", 
         message: "null value in column violates not-null constraint" 
-      })).toBe(false);
+      }))).toBe(false);
     });
 
     it("returns false for permission denied", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "42501", 
         message: "permission denied for table users" 
-      })).toBe(false);
+      }))).toBe(false);
     });
   });
 
   describe("unrelated codes and messages", () => {
     it("returns false for unrelated error code", () => {
-      expect(isTransientError({ code: "UNKNOWN_ERROR" })).toBe(false);
+      expect(isTransientError(makeError({ code: "UNKNOWN_ERROR" }))).toBe(false);
     });
 
     it("returns false for unrelated error message", () => {
-      expect(isTransientError({ message: "Something went wrong" })).toBe(false);
+      expect(isTransientError(new Error("Something went wrong"))).toBe(false);
     });
 
     it("returns false for generic database error", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "P0001", 
         message: "Database operation failed" 
-      })).toBe(false);
+      }))).toBe(false);
     });
 
     it("returns false for application error", () => {
-      expect(isTransientError({ 
-        message: "Invalid user input" 
-      })).toBe(false);
+      expect(isTransientError(new Error("Invalid user input"))).toBe(false);
     });
   });
 
   describe("edge cases", () => {
     it("returns true when both code and message match", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "ECONNRESET", 
         message: "connection terminated" 
-      })).toBe(true);
+      }))).toBe(true);
     });
 
     it("returns true when only code matches", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "ETIMEDOUT", 
         message: "some other message" 
-      })).toBe(true);
+      }))).toBe(true);
     });
 
     it("returns true when only message matches", () => {
-      expect(isTransientError({ 
+      expect(isTransientError(makeError({ 
         code: "SOME_CODE", 
         message: "no available server to connect" 
-      })).toBe(true);
+      }))).toBe(true);
     });
 
     it("returns false for error with only unrelated code", () => {
-      expect(isTransientError({ code: "NOTFOUND" })).toBe(false);
+      expect(isTransientError(makeError({ code: "NOTFOUND" }))).toBe(false);
     });
 
-    it("returns false for error with empty message", () => {
-      expect(isTransientError({ message: "" })).toBe(false);
+    it("returns false for Error with empty message", () => {
+      expect(isTransientError(new Error(""))).toBe(false);
     });
   });
 });
diff --git a/src/index.ts b/src/index.ts
index 30f15ee..134100b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -225,7 +225,7 @@ app.post("/admin/cleanup", authMiddleware, adminAuth, async (_req: Request, res:
   try {
     const results = await cleanupStaleData();
     res.json({ status: "ok", cleaned: results });
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Admin cleanup failed");
     res.status(500).json({ error: "Cleanup failed" });
   }
diff --git a/src/routes/billing.ts b/src/routes/billing.ts
index 233c8a2..2a8bd37 100644
--- a/src/routes/billing.ts
+++ b/src/routes/billing.ts
@@ -66,7 +66,7 @@ async function isDocFastSubscription(subscriptionId: string): Promise<boolean> {
           : (price?.product as Stripe.Product | null)?.id;
       return productId === DOCFAST_PRODUCT_ID;
     });
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err, subscriptionId }, "isDocFastSubscription: failed to retrieve subscription");
     return false;
   }
@@ -134,7 +134,7 @@ router.post("/checkout", checkoutLimiter, async (req: Request, res: Response) =>
     logger.info({ clientIp, sessionId: session.id }, "Checkout session created");
 
     res.json({ url: session.url });
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Checkout error");
     res.status(500).json({ error: "Failed to create checkout session" });
   }
@@ -214,7 +214,7 @@ a { color: #4f9; }
 </div>
 <script src="/copy-helper.js"></script>
 </body></html>`);
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Success page error");
     res.status(500).json({ error: "Failed to retrieve session" });
   }
@@ -237,7 +237,7 @@ router.post("/webhook", async (req: Request, res: Response) => {
   } else {
     try {
       event = getStripe().webhooks.constructEvent(req.body, sig, webhookSecret);
-    } catch (err: any) {
+    } catch (err: unknown) {
       logger.error({ err }, "Webhook signature verification failed");
       res.status(400).json({ error: "Invalid signature" });
       return;
@@ -265,7 +265,7 @@ router.post("/webhook", async (req: Request, res: Response) => {
           logger.info({ sessionId: session.id }, "Ignoring event for different product");
           break;
         }
-      } catch (err: any) {
+      } catch (err: unknown) {
         logger.error({ err, sessionId: session.id }, "Failed to retrieve session line_items");
         break;
       }
diff --git a/src/routes/convert.ts b/src/routes/convert.ts
index 9657420..0e14aa7 100644
--- a/src/routes/convert.ts
+++ b/src/routes/convert.ts
@@ -3,6 +3,7 @@ import { renderPdf, renderUrlPdf } from "../services/browser.js";
 import { markdownToHtml, wrapHtml } from "../services/markdown.js";
 import dns from "node:dns/promises";
 import logger from "../services/logger.js";
+import { errorMessage } from "../utils/errors.js";
 import { isPrivateIP } from "../utils/network.js";
 
 import { sanitizeFilename } from "../utils/sanitize.js";
@@ -122,13 +123,14 @@ convertRouter.post("/html", async (req: Request, res: Response) => {
     res.setHeader("Content-Disposition", `inline; filename="${filename}"`);
     res.setHeader("X-Render-Time", String(durationMs));
     res.send(pdf);
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Convert HTML error");
-    if (err.message === "QUEUE_FULL") {
+    const msg = errorMessage(err);
+    if (msg === "QUEUE_FULL") {
       res.status(503).json({ error: "Server busy — too many concurrent PDF generations. Please try again in a few seconds." });
       return;
     }
-    if (err.message === "PDF_TIMEOUT") {
+    if (msg === "PDF_TIMEOUT") {
       res.status(504).json({ error: "PDF generation timed out." });
       return;
     }
@@ -228,13 +230,14 @@ convertRouter.post("/markdown", async (req: Request, res: Response) => {
     res.setHeader("Content-Disposition", `inline; filename="${filename}"`);
     res.setHeader("X-Render-Time", String(durationMs));
     res.send(pdf);
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Convert MD error");
-    if (err.message === "QUEUE_FULL") {
+    const msg = errorMessage(err);
+    if (msg === "QUEUE_FULL") {
       res.status(503).json({ error: "Server busy — too many concurrent PDF generations. Please try again in a few seconds." });
       return;
     }
-    if (err.message === "PDF_TIMEOUT") {
+    if (msg === "PDF_TIMEOUT") {
       res.status(504).json({ error: "PDF generation timed out." });
       return;
     }
@@ -308,7 +311,7 @@ convertRouter.post("/url", async (req: Request, res: Response) => {
       res.status(415).json({ error: "Unsupported Content-Type. Use application/json." });
       return;
     }
-    const body = req.body as { url?: string; format?: string; landscape?: boolean; margin?: any; printBackground?: boolean; waitUntil?: string; filename?: string; headerTemplate?: string; footerTemplate?: string; displayHeaderFooter?: boolean; scale?: number; pageRanges?: string; preferCSSPageSize?: boolean; width?: string; height?: string };
+    const body = req.body as { url?: string; format?: string; landscape?: boolean; margin?: string | { top?: string; right?: string; bottom?: string; left?: string }; printBackground?: boolean; waitUntil?: string; filename?: string; headerTemplate?: string; footerTemplate?: string; displayHeaderFooter?: boolean; scale?: number; pageRanges?: string; preferCSSPageSize?: boolean; width?: string; height?: string };
 
     if (!body.url) {
       res.status(400).json({ error: "Missing 'url' field" });
@@ -365,13 +368,14 @@ convertRouter.post("/url", async (req: Request, res: Response) => {
     res.setHeader("Content-Disposition", `inline; filename="${filename}"`);
     res.setHeader("X-Render-Time", String(durationMs));
     res.send(pdf);
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Convert URL error");
-    if (err.message === "QUEUE_FULL") {
+    const msg = errorMessage(err);
+    if (msg === "QUEUE_FULL") {
       res.status(503).json({ error: "Server busy — too many concurrent PDF generations. Please try again in a few seconds." });
       return;
     }
-    if (err.message === "PDF_TIMEOUT") {
+    if (msg === "PDF_TIMEOUT") {
       res.status(504).json({ error: "PDF generation timed out." });
       return;
     }
diff --git a/src/routes/demo.ts b/src/routes/demo.ts
index c381925..da7ad63 100644
--- a/src/routes/demo.ts
+++ b/src/routes/demo.ts
@@ -3,6 +3,7 @@ import rateLimit from "express-rate-limit";
 import { renderPdf } from "../services/browser.js";
 import { markdownToHtml, wrapHtml } from "../services/markdown.js";
 import logger from "../services/logger.js";
+import { errorMessage } from "../utils/errors.js";
 import { sanitizeFilename } from "../utils/sanitize.js";
 import { validatePdfOptions } from "../utils/pdf-options.js";
 
@@ -144,10 +145,11 @@ router.post("/html", async (req: Request, res: Response) => {
     res.setHeader("Content-Length", pdf.length);
     res.setHeader("X-Render-Time", String(durationMs));
     res.send(pdf);
-  } catch (err: any) {
-    if (err.message === "QUEUE_FULL") {
+  } catch (err: unknown) {
+    const msg = errorMessage(err);
+    if (msg === "QUEUE_FULL") {
       res.status(503).json({ error: "Server busy. Please try again in a moment." });
-    } else if (err.message === "PDF_TIMEOUT") {
+    } else if (msg === "PDF_TIMEOUT") {
       res.status(504).json({ error: "PDF generation timed out." });
     } else {
       logger.error({ err }, "Demo HTML conversion failed");
@@ -249,10 +251,11 @@ router.post("/markdown", async (req: Request, res: Response) => {
     res.setHeader("Content-Length", pdf.length);
     res.setHeader("X-Render-Time", String(durationMs));
     res.send(pdf);
-  } catch (err: any) {
-    if (err.message === "QUEUE_FULL") {
+  } catch (err: unknown) {
+    const msg = errorMessage(err);
+    if (msg === "QUEUE_FULL") {
       res.status(503).json({ error: "Server busy. Please try again in a moment." });
-    } else if (err.message === "PDF_TIMEOUT") {
+    } else if (msg === "PDF_TIMEOUT") {
       res.status(504).json({ error: "PDF generation timed out." });
     } else {
       logger.error({ err }, "Demo markdown conversion failed");
diff --git a/src/routes/health.ts b/src/routes/health.ts
index 39bfb23..c88ea30 100644
--- a/src/routes/health.ts
+++ b/src/routes/health.ts
@@ -62,7 +62,7 @@ const HEALTH_CHECK_TIMEOUT_MS = 3000;
  */
 healthRouter.get("/", async (_req, res) => {
   const poolStats = getPoolStats();
-  let databaseStatus: any;
+  let databaseStatus: { status: string; version?: string; message?: string };
   let overallStatus = "ok";
   let httpStatus = 200;
 
@@ -91,10 +91,10 @@ healthRouter.get("/", async (_req, res) => {
     );
 
     databaseStatus = await Promise.race([dbCheck(), timeout]);
-  } catch (error: any) {
+  } catch (error: unknown) {
     databaseStatus = {
       status: "error",
-      message: error.message || "Database connection failed"
+      message: error instanceof Error ? error.message : "Database connection failed"
     };
     overallStatus = "degraded";
     httpStatus = 503;
diff --git a/src/routes/templates.ts b/src/routes/templates.ts
index 37a1648..81e61e3 100644
--- a/src/routes/templates.ts
+++ b/src/routes/templates.ts
@@ -172,7 +172,7 @@ templatesRouter.post("/:id/render", async (req: Request, res: Response) => {
     res.setHeader("Content-Type", "application/pdf");
     res.setHeader("Content-Disposition", `inline; filename="${filename}"`);
     res.send(pdf);
-  } catch (err: any) {
+  } catch (err: unknown) {
     logger.error({ err }, "Template render error");
     res.status(500).json({ error: "Template rendering failed" });
   }
diff --git a/src/services/db.ts b/src/services/db.ts
index 6906e5e..500cfa5 100644
--- a/src/services/db.ts
+++ b/src/services/db.ts
@@ -1,7 +1,7 @@
 import pg from "pg";
 
 import logger from "./logger.js";
-import { isTransientError } from "../utils/errors.js";
+import { isTransientError, errorMessage, errorCode } from "../utils/errors.js";
 const { Pool } = pg;
 
 const pool = new Pool({
@@ -35,10 +35,10 @@ export { isTransientError } from "../utils/errors.js";
  */
 export async function queryWithRetry(
   queryText: string,
-  params?: any[],
+  params?: unknown[],
   maxRetries = 3
 ): Promise<pg.QueryResult> {
-  let lastError: any;
+  let lastError: unknown;
   
   for (let attempt = 0; attempt <= maxRetries; attempt++) {
     let client: pg.PoolClient | undefined;
@@ -47,7 +47,7 @@ export async function queryWithRetry(
       const result = await client.query(queryText, params);
       client.release();   // Return healthy connection to pool
       return result;
-    } catch (err: any) {
+    } catch (err: unknown) {
       // Destroy the bad connection so pool doesn't reuse it
       if (client) {
         try { client.release(true); } catch (_) { /* already destroyed */ }
@@ -61,7 +61,7 @@ export async function queryWithRetry(
       
       const delayMs = Math.min(1000 * Math.pow(2, attempt), 5000); // 1s, 2s, 4s (capped at 5s)
       logger.warn(
-        { err: err.message, code: err.code, attempt: attempt + 1, maxRetries, delayMs },
+        { err: errorMessage(err), code: errorCode(err), attempt: attempt + 1, maxRetries, delayMs },
         "Transient DB error, destroying bad connection and retrying..."
       );
       await new Promise(resolve => setTimeout(resolve, delayMs));
@@ -77,7 +77,7 @@ export async function queryWithRetry(
  * fresh connections to the new PgBouncer pod.
  */
 export async function connectWithRetry(maxRetries = 3): Promise<pg.PoolClient> {
-  let lastError: any;
+  let lastError: unknown;
   
   for (let attempt = 0; attempt <= maxRetries; attempt++) {
     try {
@@ -85,7 +85,7 @@ export async function connectWithRetry(maxRetries = 3): Promise<pg.PoolClient> {
       // Validate the connection is actually alive
       try {
         await client.query("SELECT 1");
-      } catch (validationErr: any) {
+      } catch (validationErr: unknown) {
         // Connection is dead — destroy it and retry
         try { client.release(true); } catch (_) {}
         if (!isTransientError(validationErr) || attempt === maxRetries) {
@@ -93,14 +93,14 @@ export async function connectWithRetry(maxRetries = 3): Promise<pg.PoolClient> {
         }
         const delayMs = Math.min(1000 * Math.pow(2, attempt), 5000);
         logger.warn(
-          { err: validationErr.message, code: validationErr.code, attempt: attempt + 1 },
+          { err: errorMessage(validationErr), code: errorCode(validationErr), attempt: attempt + 1 },
           "Connection validation failed, destroying and retrying..."
         );
         await new Promise(resolve => setTimeout(resolve, delayMs));
         continue;
       }
       return client;
-    } catch (err: any) {
+    } catch (err: unknown) {
       lastError = err;
       
       if (!isTransientError(err) || attempt === maxRetries) {
@@ -109,7 +109,7 @@ export async function connectWithRetry(maxRetries = 3): Promise<pg.PoolClient> {
       
       const delayMs = Math.min(1000 * Math.pow(2, attempt), 5000);
       logger.warn(
-        { err: err.message, code: err.code, attempt: attempt + 1, maxRetries, delayMs },
+        { err: errorMessage(err), code: errorCode(err), attempt: attempt + 1, maxRetries, delayMs },
         "Transient DB connect error, retrying..."
       );
       await new Promise(resolve => setTimeout(resolve, delayMs));
diff --git a/src/services/email.ts b/src/services/email.ts
index ad2414d..a426553 100644
--- a/src/services/email.ts
+++ b/src/services/email.ts
@@ -1,4 +1,5 @@
 import nodemailer from "nodemailer";
+import type SMTPTransport from "nodemailer/lib/smtp-transport/index.js";
 import logger from "./logger.js";
 
 const smtpUser = process.env.SMTP_USER;
@@ -8,7 +9,7 @@ const smtpPort = Number(process.env.SMTP_PORT || 25);
 const smtpFrom = process.env.SMTP_FROM || "DocFast <noreply@docfast.dev>";
 const smtpSecure = smtpPort === 465;
 
-const transportConfig: any = {
+const transportConfig: SMTPTransport.Options = {
   host: smtpHost,
   port: smtpPort,
   secure: smtpSecure,
@@ -16,12 +17,9 @@ const transportConfig: any = {
   greetingTimeout: 5000,
   socketTimeout: 10000,
   tls: { rejectUnauthorized: false },
+  ...(smtpUser && smtpPass ? { auth: { user: smtpUser, pass: smtpPass } } : {}),
 };
 
-if (smtpUser && smtpPass) {
-  transportConfig.auth = { user: smtpUser, pass: smtpPass };
-}
-
 const transporter = nodemailer.createTransport(transportConfig);
 
 export async function sendVerificationEmail(email: string, code: string): Promise<boolean> {
diff --git a/src/utils/errors.ts b/src/utils/errors.ts
index b31cb9c..711997c 100644
--- a/src/utils/errors.ts
+++ b/src/utils/errors.ts
@@ -16,10 +16,10 @@ const TRANSIENT_ERRORS = new Set([
 /**
  * Determine if an error is transient (PgBouncer failover, network blip)
  */
-export function isTransientError(err: any): boolean {
-  if (!err) return false;
-  const code = err.code || "";
-  const msg = (err.message || "").toLowerCase();
+export function isTransientError(err: unknown): boolean {
+  if (!(err instanceof Error)) return false;
+  const code = (err as Error & { code?: string }).code || "";
+  const msg = err.message.toLowerCase();
   
   if (TRANSIENT_ERRORS.has(code)) return true;
   if (msg.includes("no available server")) return true;
@@ -30,3 +30,20 @@ export function isTransientError(err: any): boolean {
   
   return false;
 }
+
+/**
+ * Extract message from unknown error (safe for catch blocks).
+ */
+export function errorMessage(err: unknown): string {
+  if (err instanceof Error) return err.message;
+  if (typeof err === "string") return err;
+  return String(err);
+}
+
+/**
+ * Extract error code from unknown error (e.g., PostgreSQL/Node error codes).
+ */
+export function errorCode(err: unknown): string | undefined {
+  if (err instanceof Error && "code" in err) return (err as Error & { code?: string }).code;
+  return undefined;
+}