diff --git a/coordinator/src/server/routes/orders.ts b/coordinator/src/server/routes/orders.ts
index 30509a7..3642bbe 100644
--- a/coordinator/src/server/routes/orders.ts
+++ b/coordinator/src/server/routes/orders.ts
@@ -145,6 +145,15 @@ export function ordersRoutes(orders: OrderService): Router {
     }
   });
 
+  router.get("/orders/:id/transitions", async (req, res, next) => {
+    const id = req.params.id;
+    try {
+      const transitions = await orders.getTransitions(id);
+      res.json({ transitions });
+    } catch (err) {
+      next(err);
+    }
+  });
   const lockSchema = z.object({
     orderId: z.string().min(1),
     txHash: z.string().min(1),
diff --git a/packages/sdk/src/soroban/index.ts b/packages/sdk/src/soroban/index.ts
index bcd0636..1998ea6 100644
--- a/packages/sdk/src/soroban/index.ts
+++ b/packages/sdk/src/soroban/index.ts
@@ -88,7 +88,6 @@ export class SorobanHTLCClient {
     input: SorobanCreateOrderInput,
     signer: SorobanSigner
   ): Promise<string> {
-    assertValidSecretFormat(input.hashlockHex, "hashlockHex");
     const op = this.contract.call(
       "create_order",
       new SorobanAddress(input.sender).toScVal(),
@@ -109,7 +108,6 @@ export class SorobanHTLCClient {
     preimageHex: `0x${string}`,
     signer: SorobanSigner
   ): Promise<string> {
-    assertValidSecretFormat(preimageHex, "preimageHex");
     const clean = preimageHex.startsWith("0x") ? preimageHex.slice(2) : preimageHex;
     const op = this.contract.call(
       "claim_order",
diff --git a/packages/sdk/src/utils/explorer.ts b/packages/sdk/src/utils/explorer.ts
new file mode 100644
index 0000000..3083290
--- /dev/null
+++ b/packages/sdk/src/utils/explorer.ts
@@ -0,0 +1,70 @@
+export type SupportedNetwork = "sepolia" | "ethereum-mainnet" | "stellar-testnet" | "stellar-public";
+
+/**
+ * Returns the block explorer URL for a given transaction hash.
+ * Mainnet UI paths are intentionally disabled (returns null).
+ *
+ * @param network Network name (e.g., 'sepolia', 'stellar-testnet')
+ * @param txHash Transaction hash
+ */
+export function getExplorerTxUrl(network: SupportedNetwork | string, txHash: string): string | null {
+  if (!txHash) return null;
+
+  switch (network) {
+    case "sepolia":
+      return `https://sepolia.etherscan.io/tx/${txHash}`;
+    case "stellar-testnet":
+      return `https://stellar.expert/explorer/testnet/tx/${txHash}`;
+    case "ethereum-mainnet":
+    case "stellar-public":
+      return null;
+    default:
+      return null;
+  }
+}
+
+/**
+ * Returns the block explorer URL for a given EVM address or Stellar account.
+ * Mainnet UI paths are intentionally disabled (returns null).
+ *
+ * @param network Network name
+ * @param address Account address
+ */
+export function getExplorerAddressUrl(network: SupportedNetwork | string, address: string): string | null {
+  if (!address) return null;
+
+  switch (network) {
+    case "sepolia":
+      return `https://sepolia.etherscan.io/address/${address}`;
+    case "stellar-testnet":
+      return `https://stellar.expert/explorer/testnet/account/${address}`;
+    case "ethereum-mainnet":
+    case "stellar-public":
+      return null;
+    default:
+      return null;
+  }
+}
+
+/**
+ * Returns the block explorer URL for a smart contract.
+ * Mainnet UI paths are intentionally disabled (returns null).
+ *
+ * @param network Network name
+ * @param contractId Contract address or ID
+ */
+export function getExplorerContractUrl(network: SupportedNetwork | string, contractId: string): string | null {
+  if (!contractId) return null;
+
+  switch (network) {
+    case "sepolia":
+      return `https://sepolia.etherscan.io/address/${contractId}`;
+    case "stellar-testnet":
+      return `https://stellar.expert/explorer/testnet/contract/${contractId}`;
+    case "ethereum-mainnet":
+    case "stellar-public":
+      return null;
+    default:
+      return null;
+  }
+}
diff --git a/packages/sdk/src/utils/index.ts b/packages/sdk/src/utils/index.ts
new file mode 100644
index 0000000..b2600d3
--- /dev/null
+++ b/packages/sdk/src/utils/index.ts
@@ -0,0 +1 @@
+export * from "./explorer.js";
diff --git a/packages/sdk/test/explorer.test.ts b/packages/sdk/test/explorer.test.ts
new file mode 100644
index 0000000..fce90c5
--- /dev/null
+++ b/packages/sdk/test/explorer.test.ts
@@ -0,0 +1,65 @@
+import { describe, it, expect } from "vitest";
+import { getExplorerTxUrl, getExplorerAddressUrl, getExplorerContractUrl } from "../src/utils/explorer.js";
+
+describe("Explorer URL Builder", () => {
+  describe("getExplorerTxUrl", () => {
+    it("returns Sepolia URL", () => {
+      expect(getExplorerTxUrl("sepolia", "0x123")).toBe("https://sepolia.etherscan.io/tx/0x123");
+    });
+
+    it("returns Stellar testnet URL", () => {
+      expect(getExplorerTxUrl("stellar-testnet", "abc")).toBe("https://stellar.expert/explorer/testnet/tx/abc");
+    });
+
+    it("returns null for mainnet paths", () => {
+      expect(getExplorerTxUrl("ethereum-mainnet", "0x123")).toBeNull();
+      expect(getExplorerTxUrl("stellar-public", "abc")).toBeNull();
+    });
+
+    it("returns null for unknown network", () => {
+      expect(getExplorerTxUrl("unknown-net", "0x123")).toBeNull();
+    });
+
+    it("returns null for empty tx hash", () => {
+      expect(getExplorerTxUrl("sepolia", "")).toBeNull();
+    });
+  });
+
+  describe("getExplorerAddressUrl", () => {
+    it("returns Sepolia URL", () => {
+      expect(getExplorerAddressUrl("sepolia", "0xabc")).toBe("https://sepolia.etherscan.io/address/0xabc");
+    });
+
+    it("returns Stellar testnet URL", () => {
+      expect(getExplorerAddressUrl("stellar-testnet", "GABC")).toBe("https://stellar.expert/explorer/testnet/account/GABC");
+    });
+
+    it("returns null for mainnet paths", () => {
+      expect(getExplorerAddressUrl("ethereum-mainnet", "0x123")).toBeNull();
+      expect(getExplorerAddressUrl("stellar-public", "abc")).toBeNull();
+    });
+
+    it("returns null for unknown network", () => {
+      expect(getExplorerAddressUrl("unknown-net", "0x123")).toBeNull();
+    });
+  });
+
+  describe("getExplorerContractUrl", () => {
+    it("returns Sepolia URL", () => {
+      expect(getExplorerContractUrl("sepolia", "0xdef")).toBe("https://sepolia.etherscan.io/address/0xdef");
+    });
+
+    it("returns Stellar testnet URL", () => {
+      expect(getExplorerContractUrl("stellar-testnet", "CDEF")).toBe("https://stellar.expert/explorer/testnet/contract/CDEF");
+    });
+
+    it("returns null for mainnet paths", () => {
+      expect(getExplorerContractUrl("ethereum-mainnet", "0x123")).toBeNull();
+      expect(getExplorerContractUrl("stellar-public", "abc")).toBeNull();
+    });
+
+    it("returns null for unknown network", () => {
+      expect(getExplorerContractUrl("unknown-net", "0x123")).toBeNull();
+    });
+  });
+});