diff --git a/blockrun_llm/solana_client.py b/blockrun_llm/solana_client.py
index cd53c13..25d0628 100644
--- a/blockrun_llm/solana_client.py
+++ b/blockrun_llm/solana_client.py
@@ -365,10 +365,18 @@ def __init__(
                 "Solana payment requires the x402 SDK. "
                 "Install with: pip install blockrun-llm[solana]"
             )
-        key = private_key or os.environ.get("SOLANA_WALLET_KEY")
+        from .solana_wallet import load_solana_wallet
+
+        key = (
+            private_key
+            or os.environ.get("SOLANA_WALLET_KEY")
+            or load_solana_wallet()  # disk: newest ~/.*/solana-wallet.json, else ~/.blockrun/.solana-session
+        )
         if not key:
             raise ValueError(
-                "Private key required. Pass private_key or set SOLANA_WALLET_KEY env var."
+                "Private key required. Pass private_key, set SOLANA_WALLET_KEY, "
+                "or have a Solana wallet on disk "
+                "(~/.<provider>/solana-wallet.json or ~/.blockrun/.solana-session)."
             )
         self._private_key = key
         validate_api_url(api_url)
@@ -398,7 +406,15 @@ def __init__(
 
         # Initialize x402 SDK client for Solana payment signing.
         self._x402_client = x402ClientSync()
-        signer = _create_signer(self._private_key)
+        try:
+            signer = _create_signer(self._private_key)
+        except Exception as e:
+            # Parity with the Base client, which validates the resolved key up
+            # front: turn a malformed key (incl. one auto-loaded from disk) into
+            # a clean error instead of a raw base58/solders exception.
+            raise ValueError(
+                "Invalid Solana private key (expected a base58-encoded keypair " "or 32-byte seed)."
+            ) from e
         _register_svm_with_headers(self._x402_client, signer, resolved_url, resolved_headers)
         # x402ClientSync is NOT thread-safe: concurrent payment signing on one
         # shared client races on nonce/authorization state. This lock serializes
@@ -1871,10 +1887,18 @@ def __init__(
                 "Solana payment requires the x402 SDK. "
                 "Install with: pip install blockrun-llm[solana]"
             )
-        key = private_key or os.environ.get("SOLANA_WALLET_KEY")
+        from .solana_wallet import load_solana_wallet
+
+        key = (
+            private_key
+            or os.environ.get("SOLANA_WALLET_KEY")
+            or load_solana_wallet()  # disk: newest ~/.*/solana-wallet.json, else ~/.blockrun/.solana-session
+        )
         if not key:
             raise ValueError(
-                "Private key required. Pass private_key or set SOLANA_WALLET_KEY env var."
+                "Private key required. Pass private_key, set SOLANA_WALLET_KEY, "
+                "or have a Solana wallet on disk "
+                "(~/.<provider>/solana-wallet.json or ~/.blockrun/.solana-session)."
             )
         self._private_key = key
         validate_api_url(api_url)
@@ -1903,7 +1927,15 @@ def __init__(
         from x402 import x402Client  # local import to keep optional dep clean
 
         self._x402_client = x402Client()
-        signer = _create_signer(self._private_key)
+        try:
+            signer = _create_signer(self._private_key)
+        except Exception as e:
+            # Parity with the Base client, which validates the resolved key up
+            # front: turn a malformed key (incl. one auto-loaded from disk) into
+            # a clean error instead of a raw base58/solders exception.
+            raise ValueError(
+                "Invalid Solana private key (expected a base58-encoded keypair " "or 32-byte seed)."
+            ) from e
         _register_svm_with_headers(self._x402_client, signer, resolved_url, resolved_headers)
         # Lazily created on first sign (avoids binding asyncio.Lock to a loop at
         # construction time). Serializes the async signing critical section so a
diff --git a/blockrun_llm/solana_wallet.py b/blockrun_llm/solana_wallet.py
index d055f93..ee6322a 100644
--- a/blockrun_llm/solana_wallet.py
+++ b/blockrun_llm/solana_wallet.py
@@ -201,7 +201,10 @@ def load_solana_wallet() -> Optional[str]:
 
     # Legacy session file
     if SOLANA_WALLET_FILE.exists():
-        key = SOLANA_WALLET_FILE.read_text().strip()
+        try:
+            key = SOLANA_WALLET_FILE.read_text().strip()
+        except OSError:
+            return None  # unreadable (bad perms/ownership) → treat as "no wallet"
         if key:
             return key
     return None
diff --git a/tests/unit/test_solana_client.py b/tests/unit/test_solana_client.py
index e2d0b7e..c427c63 100644
--- a/tests/unit/test_solana_client.py
+++ b/tests/unit/test_solana_client.py
@@ -2,7 +2,7 @@
 
 import pytest
 import os
-from blockrun_llm.solana_client import SolanaLLMClient
+from blockrun_llm.solana_client import SolanaLLMClient, AsyncSolanaLLMClient
 
 TEST_BS58_KEY = (
     "433C7KFcM4y1ZEVdZYSH7wheSNAM384UcbgXEyD5FV7Q2HsQ1BwjEDx4GbBZUqPkZTVhFPyLyuZnzK8wCeAkU7wG"
@@ -20,12 +20,41 @@ def test_init_from_env(self):
         assert client is not None
         del os.environ["SOLANA_WALLET_KEY"]
 
-    def test_raises_without_key(self):
-        saved = os.environ.pop("SOLANA_WALLET_KEY", None)
+    def test_raises_without_key(self, monkeypatch):
+        # No env var AND no wallet session on disk → must still raise. Patch the
+        # session loader so the test is deterministic regardless of whether the
+        # machine running it happens to have ~/.blockrun/.solana-session.
+        monkeypatch.delenv("SOLANA_WALLET_KEY", raising=False)
+        monkeypatch.setattr("blockrun_llm.solana_wallet.load_solana_wallet", lambda: None)
         with pytest.raises(ValueError, match="[Pp]rivate key required"):
             SolanaLLMClient()
-        if saved:
-            os.environ["SOLANA_WALLET_KEY"] = saved
+
+    def test_init_from_session_file(self, monkeypatch):
+        # No env var, but a wallet session exists on disk → auto-load it (parity
+        # with the Base LLMClient, which already falls back to load_wallet()).
+        monkeypatch.delenv("SOLANA_WALLET_KEY", raising=False)
+        monkeypatch.setattr("blockrun_llm.solana_wallet.load_solana_wallet", lambda: TEST_BS58_KEY)
+        client = SolanaLLMClient()
+        assert client is not None
+
+    @pytest.mark.asyncio
+    async def test_async_init_from_session_file(self, monkeypatch):
+        # Same disk fallback on the async client (identical code path).
+        monkeypatch.delenv("SOLANA_WALLET_KEY", raising=False)
+        monkeypatch.setattr("blockrun_llm.solana_wallet.load_solana_wallet", lambda: TEST_BS58_KEY)
+        client = AsyncSolanaLLMClient()
+        assert client is not None
+        await client.close()
+
+    def test_raises_on_invalid_key(self, monkeypatch):
+        # A malformed key (here from the disk fallback) must surface a clean
+        # ValueError, not a raw base58/solders exception. Parity with Base.
+        monkeypatch.delenv("SOLANA_WALLET_KEY", raising=False)
+        monkeypatch.setattr(
+            "blockrun_llm.solana_wallet.load_solana_wallet", lambda: "not-a-valid-key"
+        )
+        with pytest.raises(ValueError, match="[Ii]nvalid Solana private key"):
+            SolanaLLMClient()
 
     def test_default_api_url(self):
         client = SolanaLLMClient(private_key=TEST_BS58_KEY)