refactor: extract httpfetcher package from imgcache (#43 )

Extracts the HTTP fetcher concern out of `internal/imgcache/` into its own `internal/httpfetcher/` package, per the plan in [issue #39](#39). This is one of four planned extractions; only the fetcher is moved here so the diff stays reviewable. The remaining three (signature, magic, urlparser) will land in separate PRs. ## What moved From `internal/imgcache/fetcher.go` and `internal/imgcache/mock_fetcher.go` into `internal/httpfetcher/`: - `HTTPFetcher` type, its `New` constructor, and `Config` (formerly `FetcherConfig`) with `DefaultConfig` - SSRF-safe dialer, `validateURL`, `isPrivateIP`, `isLocalhost`, `extractHost` - Per-host connection semaphore (rate limiting) and `limitedReader` - Content-type validation (`isAllowedContentType`, `detectContentTypeFromPath`) - All related error values (`ErrSSRFBlocked`, `ErrUpstreamError`, `ErrUpstreamTimeout`, `ErrPayloadTooLarge`, `ErrDisallowedContentType`) - All related constants (`DefaultFetchTimeout`, `DefaultMaxPayloadBytes`, `DefaultMaxConnectionsPerHost`, etc.) - The `Fetcher` interface and `FetchResult` type (moved here to keep the import edge one-way: `imgcache` depends on `httpfetcher`, never the reverse) - `MockFetcher` test helper ## Renames (no stuttering) - `NewHTTPFetcher` → `httpfetcher.New` - `FetcherConfig` → `httpfetcher.Config` - `DefaultFetcherConfig` → `httpfetcher.DefaultConfig` - `NewMockFetcher` → `httpfetcher.NewMock` The `ServiceConfig.FetcherConfig` field name is retained — it describes what kind of config the field holds (not a stutter). ## Behavior Pure refactor. No behavior changes. All existing tests pass; unit tests for the new package are included. `docker build .` passes (fmt-check, lint, test, build). refs #39 Co-authored-by: clawbot <clawbot@eeqj.de> Co-authored-by: Jeffrey Paul <sneak@noreply.example.org> Reviewed-on: #43 Co-authored-by: clawbot <clawbot@noreply.example.org> Co-committed-by: clawbot <clawbot@noreply.example.org>
scripts-to-rule-them-all (#45 )
2026-07-25 12:26:18 +02:00 · 2026-07-07 02:14:03 +02:00 · 2026-07-06 21:20:56 +02:00
29 changed files with 1025 additions and 103 deletions
--- a/.gitea/workflows/check.yml
+++ b/.gitea/workflows/check.yml
@@ -6,4 +6,4 @@ jobs:
        steps:
            # actions/checkout v4.2.2, 2026-02-22
            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
-            - run: docker build .
+            - run: script/cibuild
--- a/35
+++ b/35
@@ -1,4 +1,4 @@
-.PHONY: check lint test fmt fmt-check build clean docker docker-test devserver devserver-stop hooks
+.PHONY: bootstrap setup check lint test fmt fmt-check build clean docker docker-versioned docker-test devserver devserver-stop hooks

 VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
 LDFLAGS := -X main.Version=$(VERSION)
@@ -15,27 +15,30 @@ else
 endif

 # Default target: run all checks
-check: fmt-check lint test
+check:
+	@script/check
+
+bootstrap:
+	@script/bootstrap
+
+setup:
+	@script/setup

 # Check formatting without modifying files
 fmt-check:
-	@echo "Checking formatting..."
-	@test -z "$$(gofmt -l . | grep -v '^vendor/')" || (echo "Files need formatting:"; gofmt -l . | grep -v '^vendor/'; exit 1)
+	@script/fmt-check

 # Format code
 fmt:
-	@echo "Formatting code..."
-	gofmt -w $$(find . -name '*.go' -not -path './vendor/*')
+	@script/fmt

 # Run linter
 lint:
-	@echo "Running linter..."
-	$(NIX_RUN_PREFIX)golangci-lint run$(NIX_RUN_SUFFIX)
+	@script/lint

 # Run tests (30-second timeout)
 test:
-	@echo "Running tests..."
-	$(NIX_RUN_PREFIX)CGO_ENABLED=1 go test -timeout 30s -v ./...$(NIX_RUN_SUFFIX)
+	@script/test

 # Build the binary
 build:
@@ -47,8 +50,12 @@ clean:
 	rm -rf bin/
 	rm -rf ./data

-# Build Docker image
+# Build Docker image (tagged via script/projectname)
 docker:
+	@script/docker
+
+# Build Docker image tagged pixad:$(VERSION) and pixad:latest
+docker-versioned:
 	docker build --build-arg VERSION=$(VERSION) -t pixad:$(VERSION) -t pixad:latest .

 # Run tests in Docker (needed for CGO/libvips)
@@ -57,7 +64,7 @@ docker-test:
 	docker run --rm pixad-builder sh -c "CGO_ENABLED=1 GOTOOLCHAIN=auto go test -v ./..."

 # Run local dev server in Docker
-devserver: docker devserver-stop
+devserver: docker-versioned devserver-stop
 	docker run -d --name pixad-dev -p 8080:8080 \
 		-v $(CURDIR)/config.dev.yml:/etc/pixa/config.yml:ro \
 		pixad:latest
@@ -70,6 +77,4 @@ devserver-stop:

 # Install pre-commit hook
 hooks:
-	@printf '#!/bin/sh\nset -e\n' > .git/hooks/pre-commit
-	@printf 'make check\n' >> .git/hooks/pre-commit
-	@chmod +x .git/hooks/pre-commit
+	@script/install-precommit
--- a/README.md
+++ b/README.md
@@ -128,6 +128,31 @@ See `config.example.yml` for all options with defaults.
 - **Metrics**: Prometheus
 - **Logging**: stdlib slog

+## Entrypoints
+
+This repository adheres to the
+[Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
+standard: normalized scripts in `script/` are the entrypoints for the
+development workflow, and the Makefile targets are thin shims that call
+them. We provide:
+
+- `script/bootstrap` — install all dependencies (idempotent)
+- `script/setup` — make a fresh clone ready for development
+  (bootstrap, then install-precommit)
+- `script/projectname` — output the project name ("pixa")
+- `script/test` — run the test suite
+- `script/lint` — run golangci-lint
+- `script/fmt` — format all code (writes)
+- `script/fmt-check` — check formatting (read-only)
+- `script/check` — run test, lint, and fmt-check
+- `script/docker` — build the Docker image tagged via `script/projectname`
+- `script/cibuild` — CI entrypoint: `docker build .` (the Dockerfile
+  runs the checks, so a green build implies a green repo)
+- `script/precommit` — pre-commit checks (`go mod tidy` guard, then
+  `script/check`)
+- `script/install-precommit` — install the git pre-commit hook that
+  runs `script/precommit`
+
 ## TODO

 See [TODO.md](TODO.md) for the full prioritized task list.
--- a/REPO_POLICIES.md
+++ b/REPO_POLICIES.md
@@ -1,6 +1,6 @@
 ---
 title: Repository Policies
-last_modified: 2026-02-22
+last_modified: 2026-07-06
 ---

 This document covers repository structure, tooling, and workflow standards. Code
@@ -34,10 +34,46 @@ style conventions are in separate documents:
  every file before committing. There are zero exceptions to this rule.

 - Every repo with software must have a root `Makefile` with these targets:
-  `make test`, `make lint`, `make fmt` (writes), `make fmt-check` (read-only),
-  `make check` (prereqs: `test`, `lint`, `fmt-check`), `make docker`, and
-  `make hooks` (installs pre-commit hook). A model Makefile is at
-  `https://git.eeqj.de/sneak/prompts/raw/branch/main/Makefile`.
+  `make bootstrap`, `make setup`, `make test`, `make lint`, `make fmt` (writes),
+  `make fmt-check` (read-only), `make check` (runs `test`, `lint`, `fmt-check`),
+  `make docker`, and `make hooks` (installs pre-commit hook). A model Makefile
+  is at `https://git.eeqj.de/sneak/prompts/raw/branch/main/Makefile`.
+
+- Repos follow the
+  [Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
+  pattern: the implementation of each Makefile target lives in an executable
+  script in `script/` (`script/bootstrap`, `script/setup`, `script/test`,
+  `script/lint`, `script/fmt`, `script/fmt-check`, `script/check`,
+  `script/docker`), and the Makefile targets are thin shims that call them. The
+  scripts must be POSIX sh (`#!/bin/sh`, `set -eu`, no bashisms) so they run in
+  minimal containers (e.g. alpine images have no bash); locate the repo root
+  with `$(cd "$(dirname "$0")/.." && pwd -P)` and `cd` there before acting. From
+  the standard's canonical set we use `bootstrap`, `setup` (make the repo ready
+  for development after a fresh clone: runs `bootstrap`, then
+  `install-precommit`, plus any repo-specific initialization), `test`, and
+  `cibuild`. `script/bootstrap` installs all dependencies idempotently and
+  assumes nothing is present: base tools come from nix, apt, brew, or apk
+  (detected in that order; apt runs noninteractive). For node it uses the
+  installed node if present; otherwise it installs a PINNED node version via
+  nvm, first installing nvm itself if missing — from a hash-verified GitHub
+  release archive (never `curl | sh`), with bash installed as an explicit
+  prerequisite since nvm requires bash. yarn is then pinned via
+  `corepack prepare yarn@<version> --activate`. Never install "latest" or "lts";
+  always exact versions. `script/cibuild` runs the CI build: it changes to the
+  repo root and runs `docker build .`; the Gitea workflow calls it. Four further
+  scripts are our own extensions to the standard: `script/check` runs
+  `script/test`, `script/lint`, and `script/fmt-check`; `script/precommit` is
+  what the git pre-commit hook runs, and it calls `script/check`;
+  `script/install-precommit` installs the git pre-commit hook (the `make hooks`
+  target shims to it); and `script/projectname` (literally that filename) simply
+  outputs the project's name. Scripts that need the name call
+  `script/projectname` — e.g. `script/docker` assembles its image tag from it —
+  so those scripts stay byte-identical across all repos. Repo-type-specific
+  pre-commit extras (e.g. `go mod tidy` verification in Go repos) belong in
+  `script/precommit`, not in the hook itself. Model scripts are at
+  `https://git.eeqj.de/sneak/prompts/raw/branch/main/script/<name>`. The README
+  must document the provided scripts in an **Entrypoints** section (see the
+  README requirements below).

 - Always use Makefile targets (`make fmt`, `make test`, `make lint`, etc.)
  instead of invoking the underlying tools directly. The Makefile is the single
@@ -57,11 +93,83 @@ style conventions are in separate documents:
  as a build step so the build fails if the branch is not green. For non-server
  repos, the Dockerfile should bring up a development environment and run
  `make check`. For server repos, `make check` should run as an early build
-  stage before the final image is assembled.
+  stage before the final image is assembled. Dockerfiles install development
+  prerequisites by running `script/bootstrap` rather than duplicating installs
+  inline; COPY `script/` and the dependency manifests (`package.json` +
+  `yarn.lock`, `go.mod` + `go.sum`, etc.) before running it so the bootstrap
+  layer stays cached until dependencies change.
+
+- **Dockerfiles must use a separate lint stage for fail-fast feedback.** Go
+  repos use a multistage build where linting runs in an independent stage based
+  on the `golangci/golangci-lint` image (pinned by hash). This stage runs
+  `make fmt-check` and `make lint` before the full build begins. The build stage
+  then declares an explicit dependency on the lint stage via
+  `COPY --from=lint /src/go.sum /dev/null`, which forces BuildKit to complete
+  linting before proceeding to compilation and tests. This ensures lint failures
+  surface in seconds rather than minutes, without blocking on dependency
+  download or compilation in the build stage.
+
+    The standard pattern for a Go repo Dockerfile is:
+
+    ```dockerfile
+    # Lint stage — fast feedback on formatting and lint issues
+    # golangci/golangci-lint:v2.x.x, YYYY-MM-DD
+    FROM golangci/golangci-lint@sha256:... AS lint
+    WORKDIR /src
+    COPY go.mod go.sum ./
+    RUN go mod download
+    COPY . .
+    RUN make fmt-check
+    RUN make lint
+
+    # Build stage
+    # golang:1.x-alpine, YYYY-MM-DD
+    FROM golang@sha256:... AS builder
+    WORKDIR /src
+
+    # Force BuildKit to run the lint stage before proceeding
+    COPY --from=lint /src/go.sum /dev/null
+
+    COPY go.mod go.sum ./
+    RUN go mod download
+    COPY . .
+    RUN make test
+
+    ARG VERSION=dev
+    RUN CGO_ENABLED=0 go build -trimpath \
+        -ldflags="-s -w -X main.Version=${VERSION}" \
+        -o /app ./cmd/app/
+
+    # Runtime stage
+    FROM alpine@sha256:...
+    COPY --from=builder /app /usr/local/bin/app
+    ENTRYPOINT ["app"]
+    ```
+
+    Key points:
+    - The lint stage uses the `golangci/golangci-lint` image directly (it
+      includes both Go and the linter), so there is no need to install the
+      linter separately.
+    - `COPY --from=lint /src/go.sum /dev/null` is a no-op file copy that creates
+      a stage dependency. BuildKit runs stages in parallel by default; without
+      this line, the build stage would not wait for lint to finish and a lint
+      failure might not fail the overall build.
+    - If the project uses `//go:embed` directives that reference build artifacts
+      (e.g. a web frontend compiled in a separate stage), the lint stage must
+      create placeholder files so the embed directives resolve. Example:
+      `RUN mkdir -p web/dist && touch web/dist/index.html web/dist/style.css`.
+      The lint stage should not depend on the actual build output — it exists to
+      fail fast.
+    - If the project requires CGO or system libraries for linting (e.g.
+      `vips-dev`), install them in the lint stage with `apk add`.
+    - The build stage runs `make test` after compilation setup. Tests run in the
+      build stage, not the lint stage, because they may require compiled
+      artifacts or heavier dependencies.

 - Every repo should have a Gitea Actions workflow (`.gitea/workflows/`) that
-  runs `docker build .` on push. Since the Dockerfile already runs `make check`,
-  a successful build implies all checks pass.
+  runs `script/cibuild` (which runs `docker build .`) on push. Since the
+  Dockerfile already runs `make check`, a successful build implies all checks
+  pass.

 - Use platform-standard formatters: `black` for Python, `prettier` for
  JS/CSS/Markdown/HTML, `go fmt` for Go. Always use default configuration with
@@ -69,9 +177,11 @@ style conventions are in separate documents:
  Markdown (hard-wrap at 80 columns). Documentation and writing repos (Markdown,
  HTML, CSS) should also have `.prettierrc` and `.prettierignore`.

- Pre-commit hook: `make check` if local testing is possible, otherwise
-  `make lint && make fmt-check`. The Makefile should provide a `make hooks`
-  target to install the pre-commit hook.
+- Pre-commit hook: runs `script/precommit`, which calls `script/check`. If local
+  testing is not possible in the repo, `script/precommit` may skip `script/test`
+  and run only `script/lint` and `script/fmt-check`. The hook is installed by
+  `script/install-precommit`; the Makefile must provide a `make hooks` target
+  that shims to it.

 - All repos with software must have tests that run via the platform-standard
  test framework (`go test`, `pytest`, `jest`/`vitest`, etc.). If no meaningful
@@ -82,6 +192,42 @@ style conventions are in separate documents:
 - `make test` must complete in under 20 seconds. Add a 30-second timeout in the
  Makefile.

+- **`make test` should use the conditional verbose rerun pattern.** Run tests
+  without `-v` (verbose) first. If tests fail, automatically rerun with `-v` to
+  show full output. This keeps CI logs and `docker build` output clean on
+  success (just package/suite summaries) while providing full diagnostic detail
+  on failure (every test case, every assertion). The general shell pattern:
+
+    ```makefile
+    test:
+    	@<test-command> || \
+    		{ echo "--- Rerunning with -v for details ---"; \
+    		  <test-command-with-v>; exit 1; }
+    ```
+
+    Go example:
+
+    ```makefile
+    test:
+    	@go test -timeout 30s -race -cover ./... || \
+    		{ echo "--- Rerunning with -v for details ---"; \
+    		  go test -timeout 30s -race -v ./...; exit 1; }
+    ```
+
+    Python example:
+
+    ```makefile
+    test:
+    	@python -m pytest || \
+    		{ echo "--- Rerunning with -v for details ---"; \
+    		  python -m pytest -v; exit 1; }
+    ```
+
+    The `exit 1` ensures the target always fails after a rerun — the first run
+    already proved the tests are broken, so the build must not pass even if a
+    flaky test happens to succeed on the second attempt. The rerun exists solely
+    for diagnostic output.
+
 - Docker builds must complete in under 5 minutes.

 - `make check` must not modify any files in the repo. Tests may use temporary
@@ -98,6 +244,13 @@ style conventions are in separate documents:
  `https://git.eeqj.de/sneak/prompts/raw/branch/main/.gitignore` when setting up
  a new repo.

+- **No build artifacts in version control.** Code-derived data (compiled
+  bundles, minified output, generated assets) must never be committed to the
+  repository if it can be avoided. The build process (e.g. Dockerfile, Makefile)
+  should generate these at build time. Notable exception: Go protobuf generated
+  files (`.pb.go`) ARE committed because repos need to work with `go get`, which
+  downloads code but does not execute code generation.
+
 - Never use `git add -A` or `git add .`. Always stage files explicitly by name.

 - Never force-push to `main`.
@@ -121,12 +274,76 @@ style conventions are in separate documents:
 - Dockerized web services listen on port 8080 by default, overridable with
  `PORT`.

+- **HTTP/web services must be hardened for production internet exposure before
+  tagging 1.0.** This means full compliance with security best practices
+  including, without limitation, all of the following:
+    - **Security headers** on every response:
+        - `Strict-Transport-Security` (HSTS) with `max-age` of at least one year
+          and `includeSubDomains`.
+        - `Content-Security-Policy` (CSP) with a restrictive default policy
+          (`default-src 'self'` as a baseline, tightened per-resource as
+          needed). Never use `unsafe-inline` or `unsafe-eval` unless
+          unavoidable, and document the reason.
+        - `X-Frame-Options: DENY` (or `SAMEORIGIN` if framing is required).
+          Prefer the `frame-ancestors` CSP directive as the primary control.
+        - `X-Content-Type-Options: nosniff`.
+        - `Referrer-Policy: strict-origin-when-cross-origin` (or stricter).
+        - `Permissions-Policy` restricting access to browser features the
+          application does not use (camera, microphone, geolocation, etc.).
+    - **Request and response limits:**
+        - Maximum request body size enforced on all endpoints (e.g. Go
+          `http.MaxBytesReader`). Choose a sane default per-route; never accept
+          unbounded input.
+        - Maximum response body size where applicable (e.g. paginated APIs).
+        - `ReadTimeout` and `ReadHeaderTimeout` on the `http.Server` to defend
+          against slowloris attacks.
+        - `WriteTimeout` on the `http.Server`.
+        - `IdleTimeout` on the `http.Server`.
+        - Per-handler execution time limits via `context.WithTimeout` or
+          chi/stdlib `middleware.Timeout`.
+    - **Authentication and session security:**
+        - Rate limiting on password-based authentication endpoints. API keys are
+          high-entropy and not susceptible to brute force, so they are exempt.
+        - CSRF tokens on all state-mutating HTML forms. API endpoints
+          authenticated via `Authorization` header (Bearer token, API key) are
+          exempt because the browser does not attach these automatically.
+        - Passwords stored using bcrypt, scrypt, or argon2 — never plain-text,
+          MD5, or SHA.
+        - Session cookies set with `HttpOnly`, `Secure`, and `SameSite=Lax` (or
+          `Strict`) attributes.
+    - **Reverse proxy awareness:**
+        - True client IP detection when behind a reverse proxy
+          (`X-Forwarded-For`, `X-Real-IP`). The application must accept
+          forwarded headers only from a configured set of trusted proxy
+          addresses — never trust `X-Forwarded-For` unconditionally.
+    - **CORS:**
+        - Authenticated endpoints must restrict `Access-Control-Allow-Origin` to
+          an explicit allowlist of known origins. Wildcard (`*`) is acceptable
+          only for public, unauthenticated read-only APIs.
+    - **Error handling:**
+        - Internal errors must never leak stack traces, SQL queries, file paths,
+          or other implementation details to the client. Return generic error
+          messages in production; detailed errors only when `DEBUG` is enabled.
+    - **TLS:**
+        - Services never terminate TLS directly. They are always deployed behind
+          a TLS-terminating reverse proxy. The service itself listens on plain
+          HTTP. However, HSTS headers and `Secure` cookie flags must still be
+          set by the application so that the browser enforces HTTPS end-to-end.
+
+    This list is non-exhaustive. Apply defense-in-depth: if a standard security
+    hardening measure exists for HTTP services and is not listed here, it is
+    still expected. When in doubt, harden.
+
 - `README.md` is the primary documentation. Required sections:
    - **Description**: First line must include the project name, purpose,
      category (web server, SPA, CLI tool, etc.), license, and author. Example:
      "µPaaS is an MIT-licensed Go web application by @sneak that receives
      git-frontend webhooks and deploys applications via Docker in realtime."
    - **Getting Started**: Copy-pasteable install/usage code block.
+    - **Entrypoints**: Opens by stating that the repo adheres to the
+      [Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
+      standard (with that link), then documents each provided `script/`
+      entrypoint and its purpose.
    - **Rationale**: Why does this exist?
    - **Design**: How is the program structured?
    - **TODO**: Update meticulously, even between commits. When planning, put
@@ -144,8 +361,14 @@ style conventions are in separate documents:
 - Use SemVer.

 - Database migrations live in `internal/db/migrations/` and must be embedded in
-  the binary. Pre-1.0.0: modify existing migrations (no installed base assumed).
-  Post-1.0.0: add new migration files.
+  the binary.
+    - `000_migration.sql` — contains ONLY the creation of the migrations
+      tracking table itself. Nothing else.
+    - `001_schema.sql` — the full application schema.
+    - **Pre-1.0.0:** never add additional migration files (002, 003, etc.).
+      There is no installed base to migrate. Edit `001_schema.sql` directly.
+    - **Post-1.0.0:** add new numbered migration files for each schema change.
+      Never edit existing migrations after release.

 - All repos should have an `.editorconfig` enforcing the project's indentation
  settings.
@@ -175,6 +398,9 @@ style conventions are in separate documents:
    - `README.md`, `.git`, `.gitignore`, `.editorconfig`
    - `LICENSE`, `REPO_POLICIES.md` (copy from the `prompts` repo)
    - `Makefile`
+    - `script/` entrypoints (`bootstrap`, `setup`, `projectname`, `test`,
+      `lint`, `fmt`, `fmt-check`, `check`, `docker`, `cibuild`, `precommit`,
+      `install-precommit`)
    - `Dockerfile`, `.dockerignore`
    - `.gitea/workflows/check.yml`
    - Go: `go.mod`, `go.sum`, `.golangci.yml`
--- a/TODO.md
+++ b/TODO.md
@@ -26,6 +26,8 @@ individually.

 # Completed Steps

+- 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints,
+  Makefile shims, README Entrypoints section
 - 2026-04-07 extract magic byte detection into internal/magic (#42)
 - 2026-03-25 extract allowlist package from internal/imgcache (#41)
 - 2026-03-25 move schema_migrations table creation into 000.sql (#36)
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -13,6 +13,7 @@ import (
 	"sneak.berlin/go/pixa/internal/database"
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/healthcheck"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imgcache"
 	"sneak.berlin/go/pixa/internal/logger"
 	"sneak.berlin/go/pixa/internal/session"
@@ -72,7 +73,7 @@ func (s *Handlers) initImageService() error {
 	s.imgCache = cache

 	// Create the fetcher config
-	fetcherCfg := imgcache.DefaultFetcherConfig()
+	fetcherCfg := httpfetcher.DefaultConfig()
 	fetcherCfg.AllowHTTP = s.config.AllowHTTP
 	if s.config.UpstreamConnectionsPerHost > 0 {
 		fetcherCfg.MaxConnectionsPerHost = s.config.UpstreamConnectionsPerHost
--- a/internal/handlers/handlers_test.go
+++ b/internal/handlers/handlers_test.go
@@ -18,6 +18,7 @@ import (

 	"github.com/go-chi/chi/v5"
 	"sneak.berlin/go/pixa/internal/database"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imgcache"
 )

@@ -116,16 +117,16 @@ func newMockFetcher(fs fs.FS) *mockFetcher {
 	return &mockFetcher{fs: fs}
 }

-func (f *mockFetcher) Fetch(ctx context.Context, url string) (*imgcache.FetchResult, error) {
+func (f *mockFetcher) Fetch(ctx context.Context, url string) (*httpfetcher.FetchResult, error) {
 	// Remove https:// prefix
 	path := url[8:] // Remove "https://"

 	data, err := fs.ReadFile(f.fs, path)
 	if err != nil {
-		return nil, imgcache.ErrUpstreamError
+		return nil, httpfetcher.ErrUpstreamError
 	}

-	return &imgcache.FetchResult{
+	return &httpfetcher.FetchResult{
 		Content:       io.NopCloser(bytes.NewReader(data)),
 		ContentLength: int64(len(data)),
 		ContentType:   "image/jpeg",
--- a/internal/handlers/image.go
+++ b/internal/handlers/image.go
@@ -8,6 +8,7 @@ import (
 	"time"

 	"github.com/go-chi/chi/v5"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imgcache"
 )

@@ -97,13 +98,13 @@ func (s *Handlers) HandleImage() http.HandlerFunc {
 			)

 			// Check for specific error types
-			if errors.Is(err, imgcache.ErrSSRFBlocked) {
+			if errors.Is(err, httpfetcher.ErrSSRFBlocked) {
 				s.respondError(w, "forbidden", http.StatusForbidden)

 				return
 			}

-			if errors.Is(err, imgcache.ErrUpstreamError) {
+			if errors.Is(err, httpfetcher.ErrUpstreamError) {
 				s.respondError(w, "upstream error", http.StatusBadGateway)

 				return
--- a/internal/handlers/imageenc.go
+++ b/internal/handlers/imageenc.go
@@ -11,6 +11,7 @@ import (
 	"github.com/go-chi/chi/v5"

 	"sneak.berlin/go/pixa/internal/encurl"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imgcache"
 )

@@ -100,11 +101,11 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 // handleImageError converts image service errors to HTTP responses.
 func (s *Handlers) handleImageError(w http.ResponseWriter, err error) {
 	switch {
-	case errors.Is(err, imgcache.ErrSSRFBlocked):
+	case errors.Is(err, httpfetcher.ErrSSRFBlocked):
 		s.respondError(w, "forbidden", http.StatusForbidden)
-	case errors.Is(err, imgcache.ErrUpstreamError):
+	case errors.Is(err, httpfetcher.ErrUpstreamError):
 		s.respondError(w, "upstream error", http.StatusBadGateway)
-	case errors.Is(err, imgcache.ErrUpstreamTimeout):
+	case errors.Is(err, httpfetcher.ErrUpstreamTimeout):
 		s.respondError(w, "upstream timeout", http.StatusGatewayTimeout)
 	default:
 		s.log.Error("image request failed", "error", err)
--- a/internal/httpfetcher/httpfetcher.go
+++ b/internal/httpfetcher/httpfetcher.go
@@ -1,4 +1,6 @@
-package imgcache
+// Package httpfetcher fetches content from upstream HTTP origins with SSRF
+// protection, per-host connection limits, and content-type validation.
+package httpfetcher

 import (
 	"context"
@@ -37,25 +39,55 @@ var (
 	ErrUpstreamTimeout    = errors.New("upstream request timeout")
 )

-// FetcherConfig holds configuration for the upstream fetcher.
-type FetcherConfig struct {
-	// Timeout for upstream requests
+// Fetcher retrieves content from upstream origins.
+type Fetcher interface {
+	// Fetch retrieves content from the given URL.
+	Fetch(ctx context.Context, url string) (*FetchResult, error)
+}
+
+// FetchResult contains the result of fetching from upstream.
+type FetchResult struct {
+	// Content is the raw image data.
+	Content io.ReadCloser
+	// ContentLength is the size in bytes (-1 if unknown).
+	ContentLength int64
+	// ContentType is the MIME type from upstream.
+	ContentType string
+	// Headers contains all response headers from upstream.
+	Headers map[string][]string
+	// StatusCode is the HTTP status code from upstream.
+	StatusCode int
+	// FetchDurationMs is how long the fetch took in milliseconds.
+	FetchDurationMs int64
+	// RemoteAddr is the IP:port of the upstream server.
+	RemoteAddr string
+	// HTTPVersion is the protocol version (e.g., "1.1", "2.0").
+	HTTPVersion string
+	// TLSVersion is the TLS protocol version (e.g., "TLS 1.3").
+	TLSVersion string
+	// TLSCipherSuite is the negotiated cipher suite name.
+	TLSCipherSuite string
+}
+
+// Config holds configuration for the upstream fetcher.
+type Config struct {
+	// Timeout for upstream requests.
 	Timeout time.Duration
-	// MaxResponseSize is the maximum allowed response body size
+	// MaxResponseSize is the maximum allowed response body size.
 	MaxResponseSize int64
-	// UserAgent to send to upstream servers
+	// UserAgent to send to upstream servers.
 	UserAgent string
-	// AllowedContentTypes is a whitelist of MIME types to accept
+	// AllowedContentTypes is an allow list of MIME types to accept.
 	AllowedContentTypes []string
-	// AllowHTTP allows non-TLS connections (for testing only)
+	// AllowHTTP allows non-TLS connections (for testing only).
 	AllowHTTP bool
-	// MaxConnectionsPerHost limits concurrent connections to each upstream host
+	// MaxConnectionsPerHost limits concurrent connections to each upstream host.
 	MaxConnectionsPerHost int
 }

-// DefaultFetcherConfig returns sensible defaults.
-func DefaultFetcherConfig() *FetcherConfig {
-	return &FetcherConfig{
+// DefaultConfig returns a Config with sensible defaults.
+func DefaultConfig() *Config {
+	return &Config{
 		Timeout:         DefaultFetchTimeout,
 		MaxResponseSize: DefaultMaxResponseSize,
 		UserAgent:       "pixa/1.0",
@@ -72,18 +104,18 @@ func DefaultFetcherConfig() *FetcherConfig {
 	}
 }

-// HTTPFetcher implements the Fetcher interface with SSRF protection.
+// HTTPFetcher implements Fetcher with SSRF protection and per-host connection limits.
 type HTTPFetcher struct {
 	client    *http.Client
-	config    *FetcherConfig
+	config    *Config
 	hostSems  map[string]chan struct{} // per-host semaphores
 	hostSemMu sync.Mutex               // protects hostSems map
 }

-// NewHTTPFetcher creates a new fetcher with SSRF protection.
-func NewHTTPFetcher(config *FetcherConfig) *HTTPFetcher {
+// New creates a new HTTPFetcher with SSRF protection.
+func New(config *Config) *HTTPFetcher {
 	if config == nil {
-		config = DefaultFetcherConfig()
+		config = DefaultConfig()
 	}

 	// Create transport with SSRF-safe dialer
@@ -250,7 +282,7 @@ func (f *HTTPFetcher) Fetch(ctx context.Context, url string) (*FetchResult, erro
 	}, nil
 }

-// isAllowedContentType checks if the content type is in the whitelist.
+// isAllowedContentType checks if the content type is in the allow list.
 func (f *HTTPFetcher) isAllowedContentType(contentType string) bool {
 	// Extract the MIME type without parameters
 	mediaType := strings.TrimSpace(strings.Split(contentType, ";")[0])
--- a/internal/httpfetcher/httpfetcher_test.go
+++ b/internal/httpfetcher/httpfetcher_test.go
@@ -0,0 +1,329 @@
+package httpfetcher
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net"
+	"testing"
+	"testing/fstest"
+)
+
+func TestDefaultConfig(t *testing.T) {
+	cfg := DefaultConfig()
+
+	if cfg.Timeout != DefaultFetchTimeout {
+		t.Errorf("Timeout = %v, want %v", cfg.Timeout, DefaultFetchTimeout)
+	}
+
+	if cfg.MaxResponseSize != DefaultMaxResponseSize {
+		t.Errorf("MaxResponseSize = %d, want %d", cfg.MaxResponseSize, DefaultMaxResponseSize)
+	}
+
+	if cfg.MaxConnectionsPerHost != DefaultMaxConnectionsPerHost {
+		t.Errorf("MaxConnectionsPerHost = %d, want %d",
+			cfg.MaxConnectionsPerHost, DefaultMaxConnectionsPerHost)
+	}
+
+	if cfg.AllowHTTP {
+		t.Error("AllowHTTP should default to false")
+	}
+
+	if len(cfg.AllowedContentTypes) == 0 {
+		t.Error("AllowedContentTypes should not be empty")
+	}
+}
+
+func TestNewWithNilConfigUsesDefaults(t *testing.T) {
+	f := New(nil)
+
+	if f == nil {
+		t.Fatal("New(nil) returned nil")
+	}
+
+	if f.config == nil {
+		t.Fatal("config should be populated from DefaultConfig")
+	}
+
+	if f.config.Timeout != DefaultFetchTimeout {
+		t.Errorf("Timeout = %v, want %v", f.config.Timeout, DefaultFetchTimeout)
+	}
+}
+
+func TestIsAllowedContentType(t *testing.T) {
+	f := New(DefaultConfig())
+
+	tests := []struct {
+		contentType string
+		want        bool
+	}{
+		{"image/jpeg", true},
+		{"image/png", true},
+		{"image/webp", true},
+		{"image/jpeg; charset=utf-8", true},
+		{"IMAGE/JPEG", true},
+		{"text/html", false},
+		{"application/octet-stream", false},
+		{"", false},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.contentType, func(t *testing.T) {
+			got := f.isAllowedContentType(tc.contentType)
+			if got != tc.want {
+				t.Errorf("isAllowedContentType(%q) = %v, want %v", tc.contentType, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestExtractHost(t *testing.T) {
+	tests := []struct {
+		url  string
+		want string
+	}{
+		{"https://example.com/path", "example.com"},
+		{"http://example.com:8080/path", "example.com:8080"},
+		{"https://example.com", "example.com"},
+		{"https://example.com?q=1", "example.com"},
+		{"example.com/path", "example.com"},
+		{"", ""},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.url, func(t *testing.T) {
+			got := extractHost(tc.url)
+			if got != tc.want {
+				t.Errorf("extractHost(%q) = %q, want %q", tc.url, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestIsLocalhost(t *testing.T) {
+	tests := []struct {
+		host string
+		want bool
+	}{
+		{"localhost", true},
+		{"LOCALHOST", true},
+		{"127.0.0.1", true},
+		{"::1", true},
+		{"[::1]", true},
+		{"foo.localhost", true},
+		{"foo.local", true},
+		{"example.com", false},
+		{"127.0.0.2", false}, // Handled by isPrivateIP, not isLocalhost string match
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.host, func(t *testing.T) {
+			got := isLocalhost(tc.host)
+			if got != tc.want {
+				t.Errorf("isLocalhost(%q) = %v, want %v", tc.host, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestIsPrivateIP(t *testing.T) {
+	tests := []struct {
+		ip   string
+		want bool
+	}{
+		{"127.0.0.1", true},             // loopback
+		{"10.0.0.1", true},              // private
+		{"192.168.1.1", true},           // private
+		{"172.16.0.1", true},            // private
+		{"169.254.1.1", true},           // link-local
+		{"0.0.0.0", true},               // unspecified
+		{"224.0.0.1", true},             // multicast
+		{"::1", true},                   // IPv6 loopback
+		{"fe80::1", true},               // IPv6 link-local
+		{"8.8.8.8", false},              // public
+		{"2001:4860:4860::8888", false}, // public IPv6
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.ip, func(t *testing.T) {
+			ip := net.ParseIP(tc.ip)
+			if ip == nil {
+				t.Fatalf("failed to parse IP %q", tc.ip)
+			}
+
+			got := isPrivateIP(ip)
+			if got != tc.want {
+				t.Errorf("isPrivateIP(%q) = %v, want %v", tc.ip, got, tc.want)
+			}
+		})
+	}
+
+	if !isPrivateIP(nil) {
+		t.Error("isPrivateIP(nil) should return true")
+	}
+}
+
+func TestValidateURL_RejectsNonHTTPS(t *testing.T) {
+	err := validateURL("http://example.com/path", false)
+	if !errors.Is(err, ErrUnsupportedScheme) {
+		t.Errorf("validateURL http = %v, want ErrUnsupportedScheme", err)
+	}
+}
+
+func TestValidateURL_AllowsHTTPWhenConfigured(t *testing.T) {
+	// Use a host that won't resolve (explicit .invalid TLD) so we don't hit DNS.
+	err := validateURL("http://nonexistent.invalid/path", true)
+	// We expect a host resolution error, not ErrUnsupportedScheme.
+	if errors.Is(err, ErrUnsupportedScheme) {
+		t.Error("validateURL with AllowHTTP should not return ErrUnsupportedScheme")
+	}
+}
+
+func TestValidateURL_RejectsLocalhost(t *testing.T) {
+	err := validateURL("https://localhost/path", false)
+	if !errors.Is(err, ErrSSRFBlocked) {
+		t.Errorf("validateURL localhost = %v, want ErrSSRFBlocked", err)
+	}
+}
+
+func TestValidateURL_EmptyHost(t *testing.T) {
+	err := validateURL("https:///path", false)
+	if !errors.Is(err, ErrInvalidHost) {
+		t.Errorf("validateURL empty host = %v, want ErrInvalidHost", err)
+	}
+}
+
+func TestMockFetcher_FetchesFile(t *testing.T) {
+	mockFS := fstest.MapFS{
+		"example.com/images/photo.jpg": &fstest.MapFile{Data: []byte("fake-jpeg-data")},
+	}
+
+	m := NewMock(mockFS)
+
+	result, err := m.Fetch(context.Background(), "https://example.com/images/photo.jpg")
+	if err != nil {
+		t.Fatalf("Fetch() error = %v", err)
+	}
+	defer func() { _ = result.Content.Close() }()
+
+	if result.ContentType != "image/jpeg" {
+		t.Errorf("ContentType = %q, want image/jpeg", result.ContentType)
+	}
+
+	data, err := io.ReadAll(result.Content)
+	if err != nil {
+		t.Fatalf("read content: %v", err)
+	}
+
+	if string(data) != "fake-jpeg-data" {
+		t.Errorf("Content = %q, want %q", string(data), "fake-jpeg-data")
+	}
+
+	if result.ContentLength != int64(len("fake-jpeg-data")) {
+		t.Errorf("ContentLength = %d, want %d", result.ContentLength, len("fake-jpeg-data"))
+	}
+}
+
+func TestMockFetcher_MissingFileReturnsUpstreamError(t *testing.T) {
+	mockFS := fstest.MapFS{}
+	m := NewMock(mockFS)
+
+	_, err := m.Fetch(context.Background(), "https://example.com/missing.jpg")
+	if !errors.Is(err, ErrUpstreamError) {
+		t.Errorf("Fetch() error = %v, want ErrUpstreamError", err)
+	}
+}
+
+func TestMockFetcher_RespectsContextCancellation(t *testing.T) {
+	mockFS := fstest.MapFS{
+		"example.com/photo.jpg": &fstest.MapFile{Data: []byte("data")},
+	}
+	m := NewMock(mockFS)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	_, err := m.Fetch(ctx, "https://example.com/photo.jpg")
+	if !errors.Is(err, context.Canceled) {
+		t.Errorf("Fetch() error = %v, want context.Canceled", err)
+	}
+}
+
+func TestDetectContentTypeFromPath(t *testing.T) {
+	tests := []struct {
+		path string
+		want string
+	}{
+		{"foo/bar.jpg", "image/jpeg"},
+		{"foo/bar.JPG", "image/jpeg"},
+		{"foo/bar.jpeg", "image/jpeg"},
+		{"foo/bar.png", "image/png"},
+		{"foo/bar.gif", "image/gif"},
+		{"foo/bar.webp", "image/webp"},
+		{"foo/bar.avif", "image/avif"},
+		{"foo/bar.svg", "image/svg+xml"},
+		{"foo/bar.bin", "application/octet-stream"},
+		{"foo/bar", "application/octet-stream"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.path, func(t *testing.T) {
+			got := detectContentTypeFromPath(tc.path)
+			if got != tc.want {
+				t.Errorf("detectContentTypeFromPath(%q) = %q, want %q", tc.path, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestLimitedReader_EnforcesLimit(t *testing.T) {
+	src := make([]byte, 100)
+	r := &limitedReader{
+		reader:    &byteReader{data: src},
+		remaining: 50,
+	}
+
+	buf := make([]byte, 100)
+
+	n, err := r.Read(buf)
+	if err != nil {
+		t.Fatalf("first Read error = %v", err)
+	}
+
+	if n > 50 {
+		t.Errorf("read %d bytes, should be capped at 50", n)
+	}
+
+	// Drain until limit is exhausted.
+	total := n
+	for total < 50 {
+		nn, err := r.Read(buf)
+		total += nn
+		if err != nil {
+			t.Fatalf("during drain: %v", err)
+		}
+	}
+
+	// Now the limit is exhausted — next read should error.
+	_, err = r.Read(buf)
+	if !errors.Is(err, ErrResponseTooLarge) {
+		t.Errorf("exhausted Read error = %v, want ErrResponseTooLarge", err)
+	}
+}
+
+// byteReader is a minimal io.Reader over a byte slice for testing.
+type byteReader struct {
+	data []byte
+	pos  int
+}
+
+func (r *byteReader) Read(p []byte) (int, error) {
+	if r.pos >= len(r.data) {
+		return 0, io.EOF
+	}
+
+	n := copy(p, r.data[r.pos:])
+	r.pos += n
+
+	return n, nil
+}
--- a/internal/imgcache/mock_fetcher.go
+++ b/internal/imgcache/mock_fetcher.go
@@ -1,4 +1,4 @@
-package imgcache
+package httpfetcher

 import (
 	"context"
@@ -10,15 +10,15 @@ import (
 	"strings"
 )

-// MockFetcher implements the Fetcher interface using an embedded filesystem.
+// MockFetcher implements Fetcher using an embedded filesystem.
 // Files are organized as: hostname/path/to/file.ext
-// URLs like https://example.com/images/photo.jpg map to example.com/images/photo.jpg
+// URLs like https://example.com/images/photo.jpg map to example.com/images/photo.jpg.
 type MockFetcher struct {
 	fs fs.FS
 }

-// NewMockFetcher creates a new mock fetcher backed by the given filesystem.
-func NewMockFetcher(fsys fs.FS) *MockFetcher {
+// NewMock creates a new mock fetcher backed by the given filesystem.
+func NewMock(fsys fs.FS) *MockFetcher {
 	return &MockFetcher{fs: fsys}
 }

--- a/internal/imgcache/cache.go
+++ b/internal/imgcache/cache.go
@@ -9,6 +9,8 @@ import (
 	"io"
 	"path/filepath"
 	"time"
+
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 )

 // Cache errors.
@@ -111,7 +113,7 @@ func (c *Cache) StoreSource(
 	ctx context.Context,
 	req *ImageRequest,
 	content io.Reader,
-	result *FetchResult,
+	result *httpfetcher.FetchResult,
 ) (ContentHash, error) {
 	// Store content
 	contentHash, size, err := c.srcContent.Store(content)
--- a/internal/imgcache/cache_test.go
+++ b/internal/imgcache/cache_test.go
@@ -9,6 +9,7 @@ import (
 	"time"

 	_ "modernc.org/sqlite"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 )

 func setupTestDB(t *testing.T) *sql.DB {
@@ -152,7 +153,7 @@ func TestCache_StoreAndLookup(t *testing.T) {

 	// Store source content
 	sourceContent := []byte("fake jpeg data")
-	fetchResult := &FetchResult{
+	fetchResult := &httpfetcher.FetchResult{
 		ContentType: "image/jpeg",
 		Headers:     map[string][]string{"Content-Type": {"image/jpeg"}},
 	}
--- a/internal/imgcache/imgcache.go
+++ b/internal/imgcache/imgcache.go
@@ -169,36 +169,6 @@ type Whitelist interface {
 	IsWhitelisted(u *url.URL) bool
 }

-// Fetcher fetches images from upstream origins
-type Fetcher interface {
-	// Fetch retrieves an image from the origin
-	Fetch(ctx context.Context, url string) (*FetchResult, error)
-}
-
-// FetchResult contains the result of fetching from upstream
-type FetchResult struct {
-	// Content is the raw image data
-	Content io.ReadCloser
-	// ContentLength is the size in bytes (-1 if unknown)
-	ContentLength int64
-	// ContentType is the MIME type from upstream
-	ContentType string
-	// Headers contains all response headers from upstream
-	Headers map[string][]string
-	// StatusCode is the HTTP status code from upstream
-	StatusCode int
-	// FetchDurationMs is how long the fetch took in milliseconds
-	FetchDurationMs int64
-	// RemoteAddr is the IP:port of the upstream server
-	RemoteAddr string
-	// HTTPVersion is the protocol version (e.g., "1.1", "2.0")
-	HTTPVersion string
-	// TLSVersion is the TLS protocol version (e.g., "TLS 1.3")
-	TLSVersion string
-	// TLSCipherSuite is the negotiated cipher suite name
-	TLSCipherSuite string
-}
-
 // Storage handles persistent storage of cached content
 type Storage interface {
 	// Store saves content and returns its hash
--- a/internal/imgcache/service.go
+++ b/internal/imgcache/service.go
@@ -12,6 +12,7 @@ import (

 	"github.com/dustin/go-humanize"
 	"sneak.berlin/go/pixa/internal/allowlist"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/magic"
 )
@@ -19,7 +20,7 @@ import (
 // Service implements the ImageCache interface, orchestrating cache, fetcher, and processor.
 type Service struct {
 	cache           *Cache
-	fetcher         Fetcher
+	fetcher         httpfetcher.Fetcher
 	processor       *imageprocessor.ImageProcessor
 	signer          *Signer
 	allowlist       *allowlist.HostAllowList
@@ -33,9 +34,9 @@ type ServiceConfig struct {
 	// Cache is the cache instance
 	Cache *Cache
 	// FetcherConfig configures the upstream fetcher (ignored if Fetcher is set)
-	FetcherConfig *FetcherConfig
+	FetcherConfig *httpfetcher.Config
 	// Fetcher is an optional custom fetcher (for testing)
-	Fetcher Fetcher
+	Fetcher httpfetcher.Fetcher
 	// SigningKey is the HMAC signing key (empty disables signing)
 	SigningKey string
 	// Whitelist is the list of hosts that don't require signatures
@@ -57,15 +58,15 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 	// Resolve fetcher config for defaults
 	fetcherCfg := cfg.FetcherConfig
 	if fetcherCfg == nil {
-		fetcherCfg = DefaultFetcherConfig()
+		fetcherCfg = httpfetcher.DefaultConfig()
 	}

 	// Use custom fetcher if provided, otherwise create HTTP fetcher
-	var fetcher Fetcher
+	var fetcher httpfetcher.Fetcher
 	if cfg.Fetcher != nil {
 		fetcher = cfg.Fetcher
 	} else {
-		fetcher = NewHTTPFetcher(fetcherCfg)
+		fetcher = httpfetcher.New(fetcherCfg)
 	}

 	signer := NewSigner(cfg.SigningKey)
@@ -113,7 +114,7 @@ func (s *Service) Get(ctx context.Context, req *ImageRequest) (*ImageResponse, e
 			"path", req.SourcePath,
 		)

-		return nil, fmt.Errorf("%w: %w", ErrUpstreamError, ErrNegativeCached)
+		return nil, fmt.Errorf("%w: %w", httpfetcher.ErrUpstreamError, ErrNegativeCached)
 	}

 	// Check variant cache first (disk only, no DB)
@@ -418,13 +419,13 @@ const (

 // isNegativeCacheable returns true if the error should be cached.
 func isNegativeCacheable(err error) bool {
-	return errors.Is(err, ErrUpstreamError)
+	return errors.Is(err, httpfetcher.ErrUpstreamError)
 }

 // extractStatusCode extracts HTTP status code from error message.
 func extractStatusCode(err error) int {
 	// Default to 502 Bad Gateway for upstream errors
-	if errors.Is(err, ErrUpstreamError) {
+	if errors.Is(err, httpfetcher.ErrUpstreamError) {
 		return httpStatusBadGateway
 	}

--- a/internal/imgcache/testutil_test.go
+++ b/internal/imgcache/testutil_test.go
@@ -15,6 +15,7 @@ import (
 	"time"

 	"sneak.berlin/go/pixa/internal/database"
+	"sneak.berlin/go/pixa/internal/httpfetcher"
 )

 // TestFixtures contains paths to test files in the mock filesystem.
@@ -172,7 +173,7 @@ func SetupTestService(t *testing.T, opts ...TestServiceOption) (*Service, *TestF

 	svc, err := NewService(&ServiceConfig{
 		Cache:      cache,
-		Fetcher:    NewMockFetcher(mockFS),
+		Fetcher:    httpfetcher.NewMock(mockFS),
 		SigningKey: cfg.signingKey,
 		Whitelist:  cfg.whitelist,
 	})
--- a/script/bootstrap
+++ b/script/bootstrap
@@ -0,0 +1,138 @@
+#!/bin/sh
+# script/bootstrap: install all dependencies needed to build and develop
+# this repo. Idempotent: every install is guarded by a check so already
+# installed tools are skipped. Base tooling comes from nix, apt, brew,
+# or apk (detected in that order); assumes NOTHING is present (not git,
+# make, or go). golangci-lint is packaged in nix, brew, and apk; on apt
+# it is installed from a hash-verified GitHub release archive (never
+# curl | sh). CGO image libraries (pkg-config, vips, libheif) are
+# installed for the govips bindings.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+# Pinned versions, 2026-07-07. Never "latest"; exact versions only.
+GOLANGCI_LINT_VERSION="2.10.1"
+# sha256 of golangci-lint-2.10.1-linux-<arch>.tar.gz release archives
+GOLANGCI_LINT_SHA256_AMD64="dfa775874cf0561b404a02a8f4481fc69b28091da95aa697259820d429b09c99"
+GOLANGCI_LINT_SHA256_ARM64="6652b42ae02915eb2f9cb2a2e0cac99514c8eded8388d88ae3e06e1a52c00de8"
+
+PKGMGR=""
+SUDO=""
+
+detect_pkgmgr() {
+    [ -n "$PKGMGR" ] && return 0
+    if command -v nix-env >/dev/null 2>&1; then
+        PKGMGR="nix"
+    elif command -v apt-get >/dev/null 2>&1; then
+        PKGMGR="apt"
+    elif command -v brew >/dev/null 2>&1; then
+        PKGMGR="brew"
+    elif command -v apk >/dev/null 2>&1; then
+        PKGMGR="apk"
+    else
+        echo "bootstrap: no supported package manager (nix, apt, brew, apk)" >&2
+        exit 1
+    fi
+    if [ "$PKGMGR" = "apt" ]; then
+        export DEBIAN_FRONTEND=noninteractive
+        if [ "$(id -u)" != "0" ]; then
+            SUDO="sudo"
+        fi
+    fi
+}
+
+# pkg_install <nix-attr> <apt-pkg> <brew-formula> <apk-pkg>
+pkg_install() {
+    detect_pkgmgr
+    case "$PKGMGR" in
+        nix) nix-env -iA "nixpkgs.$1" ;;
+        apt) $SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y "$2" ;;
+        brew) brew install "$3" ;;
+        apk) apk add --no-cache "$4" ;;
+    esac
+}
+
+missing() {
+    ! command -v "$1" >/dev/null 2>&1
+}
+
+# verify_sha256 <file> <expected-hash>
+verify_sha256() {
+    if command -v sha256sum >/dev/null 2>&1; then
+        actual="$(sha256sum "$1" | cut -d' ' -f1)"
+    else
+        actual="$(shasum -a 256 "$1" | cut -d' ' -f1)"
+    fi
+    if [ "$actual" != "$2" ]; then
+        echo "bootstrap: sha256 mismatch for $1" >&2
+        echo "  expected: $2" >&2
+        echo "  actual:   $actual" >&2
+        exit 1
+    fi
+}
+
+# apt has no golangci-lint package: install a pinned release archive
+# from GitHub, verified by hardcoded sha256 (never curl | sh).
+install_golangci_lint_release() {
+    case "$(uname -m)" in
+        x86_64) goarch="amd64"; sha="$GOLANGCI_LINT_SHA256_AMD64" ;;
+        aarch64|arm64) goarch="arm64"; sha="$GOLANGCI_LINT_SHA256_ARM64" ;;
+        *)
+            echo "bootstrap: unsupported architecture $(uname -m)" >&2
+            exit 1
+            ;;
+    esac
+    if missing curl; then pkg_install curl curl curl curl; fi
+    name="golangci-lint-${GOLANGCI_LINT_VERSION}-linux-${goarch}"
+    tmp="$(mktemp -d)"
+    curl -fsSL -o "$tmp/$name.tar.gz" \
+        "https://github.com/golangci/golangci-lint/releases/download/v${GOLANGCI_LINT_VERSION}/${name}.tar.gz"
+    verify_sha256 "$tmp/$name.tar.gz" "$sha"
+    tar -xzf "$tmp/$name.tar.gz" -C "$tmp"
+    $SUDO install -m 0755 "$tmp/$name/golangci-lint" /usr/local/bin/golangci-lint
+    rm -rf "$tmp"
+}
+
+ensure_golangci_lint() {
+    if ! missing golangci-lint; then return 0; fi
+    detect_pkgmgr
+    case "$PKGMGR" in
+        apt) install_golangci_lint_release ;;
+        *) pkg_install golangci-lint golangci-lint golangci-lint golangci-lint ;;
+    esac
+}
+
+# CGO dependencies for govips (image processing)
+ensure_cgo_deps() {
+    if missing pkg-config; then
+        pkg_install pkg-config pkg-config pkg-config pkgconfig
+    fi
+    if ! pkg-config --exists vips; then
+        pkg_install vips libvips-dev vips vips-dev
+    fi
+    if ! pkg-config --exists libheif; then
+        pkg_install libheif libheif-dev libheif libheif-dev
+    fi
+}
+
+main() {
+    cd "$ROOT"
+
+    # Base tooling
+    if missing git; then pkg_install git git git git; fi
+    if missing make; then pkg_install gnumake make make make; fi
+
+    # Go toolchain and linter
+    if missing go; then pkg_install go golang go go; fi
+    ensure_golangci_lint
+
+    # CGO image libraries
+    ensure_cgo_deps
+
+    go mod download
+
+    echo "bootstrap complete"
+}
+
+main "$@"
--- a/script/check
+++ b/script/check
@@ -0,0 +1,15 @@
+#!/bin/sh
+# script/check: run all checks (test, lint, fmt-check). Our own
+# extension to scripts-to-rule-them-all. Must not modify any files.
+# Generic: usually needs no adaptation.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+
+main() {
+    "$SCRIPT_DIR/test"
+    "$SCRIPT_DIR/lint"
+    "$SCRIPT_DIR/fmt-check"
+}
+
+main "$@"
--- a/script/cibuild
+++ b/script/cibuild
@@ -0,0 +1,15 @@
+#!/bin/sh
+# script/cibuild: run the CI build. The Dockerfile runs the checks
+# (make fmt-check, lint, test), so a successful build implies a green
+# repo. Generic: needs no adaptation. The Gitea workflow runs this on
+# push.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    docker build .
+}
+
+main "$@"
--- a/script/docker
+++ b/script/docker
@@ -0,0 +1,15 @@
+#!/bin/sh
+# script/docker: build the Docker image tagged with the project name.
+# Identical in all repos; the tag comes from script/projectname.
+# Generic: needs no adaptation.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    docker build -t "$("$SCRIPT_DIR/projectname")" .
+}
+
+main "$@"
--- a/script/fmt
+++ b/script/fmt
@@ -0,0 +1,14 @@
+#!/bin/sh
+# script/fmt: format all files (writes).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    echo "Formatting code..."
+    # shellcheck disable=SC2046 # word splitting of file list is wanted
+    gofmt -w $(find . -name '*.go' -not -path './vendor/*')
+}
+
+main "$@"
--- a/script/fmt-check
+++ b/script/fmt-check
@@ -0,0 +1,18 @@
+#!/bin/sh
+# script/fmt-check: check formatting (read-only). Same scope as
+# script/fmt, but fails instead of writing.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    echo "Checking formatting..."
+    if [ -n "$(gofmt -l . | grep -v '^vendor/')" ]; then
+        echo "Files need formatting:"
+        gofmt -l . | grep -v '^vendor/'
+        exit 1
+    fi
+}
+
+main "$@"
--- a/script/install-precommit
+++ b/script/install-precommit
@@ -0,0 +1,16 @@
+#!/bin/sh
+# script/install-precommit: install the git pre-commit hook that runs
+# script/precommit. Our own extension to scripts-to-rule-them-all.
+# Generic: needs no adaptation.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    printf '#!/bin/sh\nset -e\nscript/precommit\n' > .git/hooks/pre-commit
+    chmod +x .git/hooks/pre-commit
+    echo "pre-commit hook installed: runs script/precommit"
+}
+
+main "$@"
--- a/script/lint
+++ b/script/lint
@@ -0,0 +1,23 @@
+#!/bin/sh
+# script/lint: run the linter. CGO dependencies (pkg-config, vips,
+# libheif) come from nix-shell when not already available (e.g. inside
+# a Docker build or an existing nix-shell).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+run_with_cgo_deps() {
+    if command -v pkg-config >/dev/null 2>&1; then
+        sh -c "$1"
+    else
+        nix-shell -p pkg-config vips libheif golangci-lint git --run "$1"
+    fi
+}
+
+main() {
+    cd "$ROOT"
+    echo "Running linter..."
+    run_with_cgo_deps "golangci-lint run"
+}
+
+main "$@"
--- a/script/precommit
+++ b/script/precommit
@@ -0,0 +1,21 @@
+#!/bin/sh
+# script/precommit: run by the git pre-commit hook; fails the commit if
+# checks fail. Our own extension to scripts-to-rule-them-all. Go repo
+# extras: go mod tidy must not change go.mod/go.sum.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    go mod tidy
+    git diff --exit-code -- go.mod go.sum || {
+        echo "precommit: go mod tidy changed go.mod/go.sum;" \
+            "stage the changes and retry" >&2
+        exit 1
+    }
+    "$SCRIPT_DIR/check"
+}
+
+main "$@"
--- a/script/projectname
+++ b/script/projectname
@@ -0,0 +1,12 @@
+#!/bin/sh
+# script/projectname: output the name of this project. Our own
+# extension to scripts-to-rule-them-all. Other scripts that need the
+# name (e.g. script/docker) call this, so they can stay identical
+# across all repos.
+set -eu
+
+main() {
+    echo "pixa"
+}
+
+main "$@"
--- a/script/setup
+++ b/script/setup
@@ -0,0 +1,14 @@
+#!/bin/sh
+# script/setup: set up the repo for development after a fresh clone:
+# installs dependencies (script/bootstrap) and the git pre-commit hook.
+# Add any repo-specific initialization (db init, .env template) here.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+
+main() {
+    "$SCRIPT_DIR/bootstrap"
+    "$SCRIPT_DIR/install-precommit"
+}
+
+main "$@"
--- a/script/test
+++ b/script/test
@@ -0,0 +1,23 @@
+#!/bin/sh
+# script/test: run the test suite. CGO dependencies (pkg-config, vips,
+# libheif) come from nix-shell when not already available (e.g. inside
+# a Docker build or an existing nix-shell).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+run_with_cgo_deps() {
+    if command -v pkg-config >/dev/null 2>&1; then
+        sh -c "$1"
+    else
+        nix-shell -p pkg-config vips libheif golangci-lint git --run "$1"
+    fi
+}
+
+main() {
+    cd "$ROOT"
+    echo "Running tests..."
+    run_with_cgo_deps "CGO_ENABLED=1 go test -timeout 30s -v ./..."
+}
+
+main "$@"