diff --git a/.gitea/workflows/check.yml b/.gitea/workflows/check.yml
index 5e9dd05..cb2f909 100644
--- a/.gitea/workflows/check.yml
+++ b/.gitea/workflows/check.yml
@@ -1,26 +1,9 @@
-name: Check
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-
+name: check
+on: [push]
 jobs:
-  check:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-
-      - uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
-        with:
-          go-version-file: go.mod
-
-      - name: Install golangci-lint
-        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee # v2.10.1
-
-      - name: Install goimports
-        run: go install golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0 # v0.42.0
-
-      - name: Run make check
-        run: make check
+    check:
+        runs-on: ubuntu-latest
+        steps:
+            # actions/checkout v4.2.2, 2026-02-28
+            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+            - run: docker build .
diff --git a/Dockerfile b/Dockerfile
index dd40645..243bf5b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,11 +1,13 @@
 # Build stage
-FROM golang:1.25-alpine AS builder
+# golang 1.25-alpine, 2026-02-28
+FROM golang@sha256:f6751d823c26342f9506c03797d2527668d095b0a15f1862cddb4d927a7a4ced AS builder
 
-RUN apk add --no-cache git make gcc musl-dev
+RUN apk add --no-cache git make gcc musl-dev binutils-gold
 
-# Install golangci-lint v2
-RUN go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
-RUN go install golang.org/x/tools/cmd/goimports@latest
+# golangci-lint v2.10.1
+RUN go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee
+# goimports v0.42.0
+RUN go install golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0
 
 WORKDIR /src
 COPY go.mod go.sum ./
@@ -20,7 +22,8 @@ RUN make check
 RUN make build
 
 # Runtime stage
-FROM alpine:3.21
+# alpine 3.21, 2026-02-28
+FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709
 
 RUN apk add --no-cache ca-certificates tzdata