diff --git a/.github/workflows/humanode-build.yml b/.github/workflows/humanode-build.yml
new file mode 100644
index 0000000..70afd3d
--- /dev/null
+++ b/.github/workflows/humanode-build.yml
@@ -0,0 +1,39 @@
+# Humanode's build of safe-cli: upstream's tests on Ganache, as upstream's ci.yml runs them, then the wheel owners
+# install, with a SHA-256 manifest. Runs on every pull request and on main.
+name: humanode-build
+on:
+  pull_request:
+  push:
+    branches: [main]
+    tags: ["humanode-*"]
+  workflow_dispatch:
+permissions:
+  contents: read
+jobs:
+  build:
+    runs-on: ubuntu-24.04
+    steps:
+      # Upstream's own test setup (safe-cli .github/workflows/ci.yml): a local Ganache chain, and the actions pinned to
+      # the same commits upstream pins.
+      - name: Create Ganache network
+        run: docker network create ganache
+      - name: Run Ganache
+        run: docker run --detach --publish 8545:8545 --network ganache -e DOCKER=true trufflesuite/ganache:latest --defaultBalanceEther 10000 --gasLimit 10000000 -a 30 --chain.chainId 1337 --chain.networkId 1337 -d
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1, as upstream pins it
+      - uses: astral-sh/setup-uv@18d369b23da25a81e9458561248e1aafff6a70fa # v10.3.1, as upstream pins it
+        with:
+          python-version: "3.13"
+      - name: Install exactly the locked dependencies
+        run: uv sync --group dev --all-extras --frozen
+      - name: Upstream tests
+        run: uv run pytest -rxXs
+      - name: Build the wheel
+        run: uv build --wheel
+      - name: Manifest
+        run: |
+          sha256sum dist/*.whl > dist/SHA256SUMS
+          echo "commit $GITHUB_SHA" >> dist/SHA256SUMS
+      - uses: actions/upload-artifact@v4
+        with:
+          name: safe-cli-${{ github.ref_name }}
+          path: dist/
diff --git a/src/safe_cli/gas_price.py b/src/safe_cli/gas_price.py
index b3bf6c0..4e96c33 100644
--- a/src/safe_cli/gas_price.py
+++ b/src/safe_cli/gas_price.py
@@ -18,6 +18,11 @@
 
 LEGACY_GAS_PRICE_FLAG = "--legacy-gas-price"
 
+# Humanode's build: on these chains --legacy-gas-price is on by default (SAFE_CLI_LEGACY_GAS=0 turns it off). Humanode
+# charges a fixed fee per gas, which eth_gasPrice reports, while eth_feeHistory forecasts 0.875 x that fee after a
+# quiet block, so EIP-1559 fees taken from fee history are refused.
+LEGACY_GAS_DEFAULT_CHAIN_IDS = {5234}
+
 
 def parse_gwei(value: str) -> int:
     """
@@ -64,7 +69,10 @@ def legacy_gas_price(w3: Web3) -> int | None:
     fixed = os.environ.get("SAFE_CLI_LEGACY_GAS_PRICE", "")
     if fixed:
         return parse_gwei(fixed)
-    if os.environ.get("SAFE_CLI_LEGACY_GAS", "") == "1":
+    setting = os.environ.get("SAFE_CLI_LEGACY_GAS", "")
+    if setting == "1" or (
+        setting != "0" and w3.eth.chain_id in LEGACY_GAS_DEFAULT_CHAIN_IDS
+    ):
         return w3.eth.gas_price
     return None
 
diff --git a/tests/test_gas_price.py b/tests/test_gas_price.py
index ab794d7..83472b7 100644
--- a/tests/test_gas_price.py
+++ b/tests/test_gas_price.py
@@ -41,6 +41,7 @@ def test_take_flag_rejects_bad_price(self):
     def test_legacy_gas_price(self):
         w3 = mock.Mock()
         w3.eth.gas_price = 123
+        w3.eth.chain_id = 1
         with mock.patch.dict(os.environ, {}, clear=True):
             self.assertIsNone(legacy_gas_price(w3))
         with mock.patch.dict(os.environ, {"SAFE_CLI_LEGACY_GAS": "1"}, clear=True):
@@ -51,3 +52,15 @@ def test_legacy_gas_price(self):
             clear=True,
         ):
             self.assertEqual(legacy_gas_price(w3), 2 * 10**9)
+
+    def test_default_on_humanode(self):
+        w3 = mock.Mock()
+        w3.eth.gas_price = 715_000 * 10**9
+        w3.eth.chain_id = 5234
+        with mock.patch.dict(os.environ, {}, clear=True):
+            self.assertEqual(legacy_gas_price(w3), 715_000 * 10**9)
+        with mock.patch.dict(os.environ, {"SAFE_CLI_LEGACY_GAS": "0"}, clear=True):
+            self.assertIsNone(legacy_gas_price(w3))
+        w3.eth.chain_id = 1
+        with mock.patch.dict(os.environ, {}, clear=True):
+            self.assertIsNone(legacy_gas_price(w3))