diff --git a/README.md b/README.md
index e473f3f..1216335 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,11 @@
 Official TypeScript and Python SDKs for the **Hashlock Markets** developer API — non-custodial
 cross-chain atomic swaps (**BTC ↔ EVM / TRON**) over sealed RFQ + HTLC.
 
+> ⚠️ **Sandbox / testnet preview (0.x).** The SDK defaults to the public sandbox
+> (`api-dev.hashlock.markets`) and targets **testnets only** — pre-mainnet, pre-external-audit. The API
+> surface may still change before the stable `1.0` release, which will accompany mainnet. Don't use with
+> mainnet funds.
+
 - **Non-custodial.** Settlement endpoints return *unsigned* transactions. You sign with your own key or
   HSM; the server never holds your keys.
 - **Native, no bridge.** Real BTC ↔ real EVM/TRON assets, settled directly via HTLC — no wrapped tokens,
diff --git a/python/README.md b/python/README.md
index 58ef781..ede3b83 100644
--- a/python/README.md
+++ b/python/README.md
@@ -3,6 +3,9 @@
 Python SDK for the [Hashlock Markets](https://github.com/Hashlock-Tech/hashlock-sdk) developer API —
 non-custodial cross-chain atomic swaps (BTC ↔ EVM/TRON). Python 3.9+, built on `httpx`.
 
+> ⚠️ **Sandbox / testnet preview (0.x)** — defaults to `api-dev.hashlock.markets`, testnets only,
+> pre-mainnet. The API may change before the stable `1.0`. Not for mainnet funds.
+
 ```bash
 pip install hashlock-sdk          # add [ws] for the maker WebSocket feed: hashlock-sdk[ws]
 ```
diff --git a/python/hashlock/__init__.py b/python/hashlock/__init__.py
index 8b22809..b468c4b 100644
--- a/python/hashlock/__init__.py
+++ b/python/hashlock/__init__.py
@@ -5,4 +5,4 @@
 from .webhooks import verify_webhook
 
 __all__ = ["HashlockClient", "HashlockError", "new_secret", "sha256_hex", "verify_webhook"]
-__version__ = "1.0.0"
+__version__ = "0.4.0"
diff --git a/python/pyproject.toml b/python/pyproject.toml
index 198c334..3d026ca 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -4,12 +4,21 @@ build-backend = "hatchling.build"
 
 [project]
 name = "hashlock-sdk"
-version = "1.0.0"
+version = "0.4.0"
 description = "Python SDK for the Hashlock Markets developer API — non-custodial cross-chain atomic swaps (BTC <-> EVM/TRON) over sealed RFQ + HTLC."
 readme = "README.md"
 license = { text = "MIT" }
 requires-python = ">=3.9"
 keywords = ["hashlock", "atomic-swap", "htlc", "bitcoin", "cross-chain", "otc", "defi"]
+classifiers = [
+  "Development Status :: 4 - Beta",
+  "License :: OSI Approved :: MIT License",
+  "Intended Audience :: Developers",
+  "Intended Audience :: Financial and Insurance Industry",
+  "Programming Language :: Python :: 3",
+  "Topic :: Software Development :: Libraries :: Python Modules",
+  "Topic :: Office/Business :: Financial",
+]
 dependencies = ["httpx>=0.24"]
 
 [project.optional-dependencies]
diff --git a/typescript/README.md b/typescript/README.md
index cce31e5..8dd7781 100644
--- a/typescript/README.md
+++ b/typescript/README.md
@@ -4,6 +4,9 @@ TypeScript SDK for the [Hashlock Markets](https://github.com/Hashlock-Tech/hashl
 non-custodial cross-chain atomic swaps (BTC ↔ EVM/TRON). Runs on Node 18+, browsers, and edge runtimes
 (native `fetch` / `WebSocket`, zero runtime dependencies).
 
+> ⚠️ **Sandbox / testnet preview (0.x)** — defaults to `api-dev.hashlock.markets`, testnets only,
+> pre-mainnet. The API may change before the stable `1.0`. Not for mainnet funds.
+
 ```bash
 npm i @hashlock-tech/sdk
 ```
diff --git a/typescript/package.json b/typescript/package.json
index 4d1fe2c..05c3f6e 100644
--- a/typescript/package.json
+++ b/typescript/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@hashlock-tech/sdk",
-  "version": "1.0.0",
+  "version": "0.4.0",
   "description": "TypeScript SDK for the Hashlock Markets developer API — non-custodial cross-chain atomic swaps (BTC ↔ EVM/TRON) over sealed RFQ + HTLC.",
   "license": "MIT",
   "type": "module",