Merge main into next: resolve conflicts, rewrite Dockerfile for Go 1.23

- Resolve merge conflicts (README.md, TODO.md, go.mod) keeping next's versions
- Rewrite Dockerfile: replace sneak/builder:2022-12-08 (Go 1.19) with
  golang@sha256-pinned (Go 1.23)
- Remove references to deleted vendor.tzst, modcache.tzst, .golangci.yml
- Simplify to standard multi-stage build: test + build + scratch final image
- Keep module path sneak.berlin/go/mfer from next branch

.drone.yml

@@ -1,23 +0,0 @@
-kind: pipeline
-name: test-docker-build
-
-steps:
-- name: test-docker-build
-  image: plugins/docker
-  network_mode: bridge
-  settings:
-    repo: sneak/mfer
-    build_args_from_env: [ DRONE_COMMIT_SHA ]
-    dry_run: true
-    custom_dns: [ 116.202.204.30 ]
-    tags:
-      - ${DRONE_COMMIT_SHA:0:7}
-      - ${DRONE_BRANCH}
-      - latest
-- name: notify
-  image: plugins/slack
-  settings:
-    webhook:
-      from_secret: SLACK_WEBHOOK_URL
-  when:
-    event: pull_request

.gitignore

@@ -3,3 +3,8 @@
 *.tmp
 *.dockerimage
 /vendor
+vendor.tzst
+modcache.tzst
+
+# Stale files
+.drone.yml

Dockerfile

@@ -1,37 +1,11 @@
-################################################################################
-#2345678911234567892123456789312345678941234567895123456789612345678971234567898
-################################################################################
-FROM sneak/builder:2022-12-08 AS builder
-ENV DEBIAN_FRONTEND noninteractive
-WORKDIR /build
-COPY ./Makefile ./.golangci.yml ./go.mod ./go.sum /build/
-COPY ./vendor.tzst /build/vendor.tzst
-COPY ./modcache.tzst /build/modcache.tzst
-COPY ./internal ./internal
-COPY ./bin/gitrev.sh ./bin/gitrev.sh
-COPY ./mfer ./mfer
-COPY ./cmd ./cmd
-ARG GITREV unknown
-ARG DRONE_COMMIT_SHA unknown
+FROM golang@sha256:60deed95d3888cc5e4d9ff8a10c54e5edc008c6ae3fba6187be6fb592e19e8c0 AS builder
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN go test -v --timeout 30s ./...
+RUN cd cmd/mfer && go build -tags urfave_cli_no_docs -o /mfer .
 
-RUN mkdir -p "$(go env GOMODCACHE)" && cd "$(go env GOMODCACHE)" && \
-    zstdmt -d --stdout /build/modcache.tzst | tar xf - && \
-    rm /build/modcache.tzst && cd /build
-RUN \
-    cd mfer && go generate . && cd .. && \
-    GOPACKAGESDEBUG=true golangci-lint run ./... && \
-    mkdir vendor && cd vendor && \
-    zstdmt -d --stdout /build/vendor.tzst | tar xf - && rm /build/vendor.tzst && \
-    cd .. && \
-    make mfer.cmd
-RUN rm -rf /build/vendor && go mod vendor && tar -c . | zstdmt -19 > /src.tzst
-################################################################################
-#2345678911234567892123456789312345678941234567895123456789612345678971234567898
-################################################################################
-## final image
-################################################################################
 FROM scratch
-# we put all the source into the final image for posterity, it's small
-COPY --from=builder /src.tzst /src.tzst
-COPY --from=builder /build/mfer.cmd /mfer
+COPY --from=builder /mfer /mfer
 ENTRYPOINT ["/mfer"]

FORMAT.md

@@ -0,0 +1,142 @@
+# .mf File Format Specification
+
+Version 1.0
+
+## Overview
+
+An `.mf` file is a binary manifest that describes a directory tree of files,
+including their paths, sizes, and cryptographic checksums. It supports
+optional GPG signatures for integrity verification and optional timestamps
+for metadata preservation.
+
+## File Structure
+
+An `.mf` file consists of two parts, concatenated:
+
+1. **Magic bytes** (8 bytes): the ASCII string `ZNAVSRFG`
+2. **Outer message**: a Protocol Buffers serialized `MFFileOuter` message
+
+There is no length prefix or version byte between the magic and the protobuf
+message. The protobuf message extends to the end of the file.
+
+See [`mfer/mf.proto`](mfer/mf.proto) for exact field numbers and types.
+
+## Outer Message (`MFFileOuter`)
+
+The outer message contains:
+
+| Field              | Number | Type              | Description                                      |
+|--------------------|--------|-------------------|--------------------------------------------------|
+| `version`          | 101    | enum              | Must be `VERSION_ONE` (1)                        |
+| `compressionType`  | 102    | enum              | Compression of `innerMessage`; must be `COMPRESSION_ZSTD` (1) |
+| `size`             | 103    | int64             | Uncompressed size of `innerMessage` (corruption detection) |
+| `sha256`           | 104    | bytes             | SHA-256 hash of the **compressed** `innerMessage` (corruption detection) |
+| `uuid`             | 105    | bytes             | Random v4 UUID; must match the inner message UUID |
+| `innerMessage`     | 199    | bytes             | Zstd-compressed serialized `MFFile` message      |
+| `signature`        | 201    | bytes (optional)  | GPG signature (ASCII-armored or binary)          |
+| `signer`           | 202    | bytes (optional)  | Full GPG key ID of the signer                    |
+| `signingPubKey`    | 203    | bytes (optional)  | Full GPG signing public key                      |
+
+### SHA-256 Hash
+
+The `sha256` field (104) covers the **compressed** `innerMessage` bytes.
+This allows verifying data integrity before decompression.
+
+## Compression
+
+The `innerMessage` field is compressed with [Zstandard (zstd)](https://facebook.github.io/zstd/).
+Implementations must enforce a decompression size limit to prevent
+decompression bombs. The reference implementation limits decompressed size to
+256 MB.
+
+## Inner Message (`MFFile`)
+
+After decompressing `innerMessage`, the result is a serialized `MFFile`
+(referred to as the manifest):
+
+| Field       | Number | Type                  | Description                                |
+|-------------|--------|-----------------------|--------------------------------------------|
+| `version`   | 100    | enum                  | Must be `VERSION_ONE` (1)                  |
+| `files`     | 101    | repeated `MFFilePath` | List of files in the manifest              |
+| `uuid`      | 102    | bytes                 | Random v4 UUID; must match outer UUID      |
+| `createdAt` | 201    | Timestamp (optional)  | When the manifest was created              |
+
+## File Entries (`MFFilePath`)
+
+Each file entry contains:
+
+| Field      | Number | Type                      | Description                          |
+|------------|--------|---------------------------|--------------------------------------|
+| `path`     | 1      | string                    | Relative file path (see Path Rules)  |
+| `size`     | 2      | int64                     | File size in bytes                   |
+| `hashes`   | 3      | repeated `MFFileChecksum` | At least one hash required           |
+| `mimeType` | 301    | string (optional)         | MIME type                            |
+| `mtime`    | 302    | Timestamp (optional)      | Modification time                    |
+| `ctime`    | 303    | Timestamp (optional)      | Change time (inode metadata change)  |
+
+Field 304 (`atime`) has been removed from the specification. Access time is
+volatile and non-deterministic; it is not useful for integrity verification.
+
+## Path Rules
+
+All `path` values must satisfy these invariants:
+
+- **UTF-8**: paths must be valid UTF-8
+- **Forward slashes**: use `/` as the path separator (never `\`)
+- **Relative only**: no leading `/`
+- **No parent traversal**: no `..` path segments
+- **No empty segments**: no `//` sequences
+- **No trailing slash**: paths refer to files, not directories
+
+Implementations must validate these invariants when reading and writing
+manifests. Paths that violate these rules must be rejected.
+
+## Hash Format (`MFFileChecksum`)
+
+Each checksum is a single `bytes multiHash` field containing a
+[multihash](https://multiformats.io/multihash/)-encoded value. Multihash is
+self-describing: the encoded bytes include a varint algorithm identifier
+followed by a varint digest length followed by the digest itself.
+
+The 1.0 implementation writes SHA-256 multihashes (`0x12` algorithm code).
+Implementations must be able to verify SHA-256 multihashes at minimum.
+
+## Signature Scheme
+
+Signing is optional. When present, the signature covers a canonical string
+constructed as:
+
+```
+ZNAVSRFG-<UUID>-<SHA256>
+```
+
+Where:
+- `ZNAVSRFG` is the magic bytes string (literal ASCII)
+- `<UUID>` is the hex-encoded UUID from the outer message
+- `<SHA256>` is the hex-encoded SHA-256 hash from the outer message (covering compressed data)
+
+Components are separated by hyphens. The signature is produced by GPG over
+this canonical string and stored in the `signature` field of the outer
+message.
+
+## Deterministic Serialization
+
+By default, manifests are generated deterministically:
+
+- File entries are sorted by `path` in **lexicographic byte order**
+- `createdAt` is omitted unless explicitly requested
+- `atime` is never included (field removed from schema)
+
+This ensures that two independent runs over the same directory tree produce
+byte-identical `.mf` files (assuming file contents and metadata have not
+changed).
+
+## MIME Type
+
+The recommended MIME type for `.mf` files is `application/octet-stream`.
+The `.mf` file extension is the canonical identifier.
+
+## Reference
+
+- Proto definition: [`mfer/mf.proto`](mfer/mf.proto)
+- Reference implementation: [git.eeqj.de/sneak/mfer](https://git.eeqj.de/sneak/mfer)

README.md

@@ -3,54 +3,25 @@
 [mfer](https://git.eeqj.de/sneak/mfer) is a reference implementation library
 and thin wrapper command-line utility written in [Go](https://golang.org)
 and first published in 2022 under the [WTFPL](https://wtfpl.net) (public
-domain) license. It specifies and generates `.mf` manifest files over a
+domain) license.  It specifies and generates `.mf` manifest files over a
 directory tree of files to encapsulate metadata about them (such as
 cryptographic checksums or signatures over same) to aid in archiving,
-downloading, and streaming, or mirroring. The manifest files' data is
+downloading, and streaming, or mirroring.  The manifest files' data is
 serialized with Google's [protobuf serialization
-format](https://developers.google.com/protocol-buffers). The structure of
+format](https://developers.google.com/protocol-buffers).  The structure of
 these files can be found [in the format
 specification](https://git.eeqj.de/sneak/mfer/src/branch/main/mfer/mf.proto)
 which is included in the [project
 repository](https://git.eeqj.de/sneak/mfer).
 
 The current version is pre-1.0 and while the repo was published in 2022,
-there has not yet been any versioned release. [SemVer](https://semver.org)
+there has not yet been any versioned release.  [SemVer](https://semver.org)
 will be used for releases.
 
 This project was started by [@sneak](https://sneak.berlin) to scratch an
 itch in 2022 and is currently a one-person effort, though the goal is for
 this to emerge as a de-facto standard and be incorporated into other
-software. A compatible javascript library is planned.
-
-# Phases
-
-Manifest generation happens in two distinct phases:
-
-## Phase 1: Enumeration
-
-Walking directories and calling `stat()` on files to collect metadata (path, size, mtime, ctime). This builds the list of files to be scanned. Relatively fast as it only reads filesystem metadata, not file contents.
-
-**Progress:** `EnumerateStatus` with `FilesFound` and `BytesFound`
-
-## Phase 2: Scan (ToManifest)
-
-Reading file contents and computing cryptographic hashes for manifest generation. This is the expensive phase that reads all file data from disk.
-
-**Progress:** `ScanStatus` with `TotalFiles`, `ScannedFiles`, `TotalBytes`, `ScannedBytes`, `BytesPerSec`
-
-# Code Conventions
-
-- **Logging:** Never use `fmt.Printf` or write to stdout/stderr directly in normal code. Use the `internal/log` package for all output (`log.Info`, `log.Infof`, `log.Debug`, `log.Debugf`, `log.Progressf`, `log.ProgressDone`).
-- **Filesystem abstraction:** Use `github.com/spf13/afero` for filesystem operations to enable testing and flexibility.
-- **CLI framework:** Use `github.com/urfave/cli/v2` for command-line interface.
-- **Serialization:** Use Protocol Buffers for manifest file format.
-- **Internal packages:** Non-exported implementation details go in `internal/` subdirectories.
-- **Concurrency:** Use `sync.RWMutex` for protecting shared state; prefer channels for progress reporting.
-- **Progress channels:** Use buffered channels (size 1) with non-blocking sends to avoid blocking the main operation if the consumer is slow.
-- **Context support:** Long-running operations should accept `context.Context` for cancellation.
-- **NO_COLOR:** Respect the `NO_COLOR` environment variable for disabling colored output.
-- **Options pattern:** Use `NewWithOptions(opts *Options)` constructor pattern for configurable types.
+software.  A compatible javascript library is planned.
 
 # Build Status
 
@@ -59,18 +30,19 @@ Reading file contents and computing cryptographic hashes for manifest generation
 # Participation
 
 The community is as yet nonexistent so there are no defined policies or
-norms yet. Primary development happens on a privately-run Gitea instance at
+norms yet.  Primary development happens on a privately-run Gitea instance at
 [https://git.eeqj.de/sneak/mfer](https://git.eeqj.de/sneak/mfer) and issues
 are [tracked there](https://git.eeqj.de/sneak/mfer/issues).
 
 Changes must always be formatted with a standard `go fmt`, syntactically
 valid, and must pass the linting defined in the repository (presently only
-the `golangci-lint` defaults), which can be run with a `make lint`. The
+the `golangci-lint` defaults), which can be run with a `make lint`.  The
 `main` branch is protected and all changes must be made via [pull
 requests](https://git.eeqj.de/sneak/mfer/pulls) and pass CI to be merged.
 Any changes submitted to this project must also be
 [WTFPL-licensed](https://wtfpl.net) to be considered.
 
+
 # Problem Statement
 
 Given a plain URL, there is no standard way to safely and programmatically
@@ -148,10 +120,6 @@ The manifest file would do several important things:
   - metadata size should not be used as an excuse to sacrifice utility (such
     as providing checksums over each chunk of a large file)
 
-# Limitations
-
-- **Manifest size:** Manifests must fit entirely in system memory during reading and writing.
-
 # Open Questions
 
 - Should the manifest file include checksums of individual file chunks, or just for the whole assembled file?
@@ -239,15 +207,24 @@ regardless of filesystem format.
 Please email [`sneak@sneak.berlin`](mailto:sneak@sneak.berlin) with your
 desired username for an account on this Gitea instance.
 
+# See Also
+
+## Prior Art: Metalink
+
+* [Metalink - Mozilla Wiki](https://wiki.mozilla.org/Metalink)
+* [Metalink - Wikipedia](https://en.wikipedia.org/wiki/Metalink)
+* [RFC 5854 - The Metalink Download Description Format](https://datatracker.ietf.org/doc/html/rfc5854)
+* [RFC 6249 - Metalink/HTTP: Mirrors and Hashes](https://www.rfc-editor.org/rfc/rfc6249.html)
+
 ## Links
 
-- Repo: [https://git.eeqj.de/sneak/mfer](https://git.eeqj.de/sneak/mfer)
-- Issues: [https://git.eeqj.de/sneak/mfer/issues](https://git.eeqj.de/sneak/mfer/issues)
+* Repo: [https://git.eeqj.de/sneak/mfer](https://git.eeqj.de/sneak/mfer)
+* Issues: [https://git.eeqj.de/sneak/mfer/issues](https://git.eeqj.de/sneak/mfer/issues)
 
 # Authors
 
-- [@sneak <sneak@sneak.berlin>](mailto:sneak@sneak.berlin)
+* [@sneak <sneak@sneak.berlin>](mailto:sneak@sneak.berlin)
 
 # License
 
-- [WTFPL](https://wtfpl.net)
+* [WTFPL](https://wtfpl.net)

internal/checker/checker.go

@@ -1,281 +0,0 @@
-package checker
-
-import (
-	"bytes"
-	"context"
-	"crypto/sha256"
-	"errors"
-	"io"
-	"os"
-	"path/filepath"
-
-	"github.com/multiformats/go-multihash"
-	"github.com/spf13/afero"
-	"sneak.berlin/go/mfer/mfer"
-)
-
-// Result represents the outcome of checking a single file.
-type Result struct {
-	Path    string // Relative path from manifest
-	Status  Status // Verification result status
-	Message string // Human-readable description of the result
-}
-
-// Status represents the verification status of a file.
-type Status int
-
-const (
-	StatusOK           Status = iota // File matches manifest (size and hash verified)
-	StatusMissing                    // File not found on disk
-	StatusSizeMismatch               // File size differs from manifest
-	StatusHashMismatch               // File hash differs from manifest
-	StatusExtra                      // File exists on disk but not in manifest
-	StatusError                      // Error occurred during verification
-)
-
-func (s Status) String() string {
-	switch s {
-	case StatusOK:
-		return "OK"
-	case StatusMissing:
-		return "MISSING"
-	case StatusSizeMismatch:
-		return "SIZE_MISMATCH"
-	case StatusHashMismatch:
-		return "HASH_MISMATCH"
-	case StatusExtra:
-		return "EXTRA"
-	case StatusError:
-		return "ERROR"
-	default:
-		return "UNKNOWN"
-	}
-}
-
-// CheckStatus contains progress information for the check operation.
-type CheckStatus struct {
-	TotalFiles   int64   // Total number of files in manifest
-	CheckedFiles int64   // Number of files checked so far
-	TotalBytes   int64   // Total bytes to verify (sum of all file sizes)
-	CheckedBytes int64   // Bytes verified so far
-	BytesPerSec  float64 // Current throughput rate
-	Failures     int64   // Number of verification failures encountered
-}
-
-// Checker verifies files against a manifest.
-type Checker struct {
-	basePath string
-	files    []*mfer.MFFilePath
-	fs       afero.Fs
-	// manifestPaths is a set of paths in the manifest for quick lookup
-	manifestPaths map[string]struct{}
-}
-
-// NewChecker creates a new Checker for the given manifest, base path, and filesystem.
-// The basePath is the directory relative to which manifest paths are resolved.
-// If fs is nil, the real filesystem (OsFs) is used.
-func NewChecker(manifestPath string, basePath string, fs afero.Fs) (*Checker, error) {
-	if fs == nil {
-		fs = afero.NewOsFs()
-	}
-
-	m, err := mfer.NewManifestFromFile(fs, manifestPath)
-	if err != nil {
-		return nil, err
-	}
-
-	abs, err := filepath.Abs(basePath)
-	if err != nil {
-		return nil, err
-	}
-
-	files := m.Files()
-	manifestPaths := make(map[string]struct{}, len(files))
-	for _, f := range files {
-		manifestPaths[f.Path] = struct{}{}
-	}
-
-	return &Checker{
-		basePath:      abs,
-		files:         files,
-		fs:            fs,
-		manifestPaths: manifestPaths,
-	}, nil
-}
-
-// FileCount returns the number of files in the manifest.
-func (c *Checker) FileCount() int64 {
-	return int64(len(c.files))
-}
-
-// TotalBytes returns the total size of all files in the manifest.
-func (c *Checker) TotalBytes() int64 {
-	var total int64
-	for _, f := range c.files {
-		total += f.Size
-	}
-	return total
-}
-
-// Check verifies all files against the manifest.
-// Results are sent to the results channel as files are checked.
-// Progress updates are sent to the progress channel approximately once per second.
-// Both channels are closed when the method returns.
-func (c *Checker) Check(ctx context.Context, results chan<- Result, progress chan<- CheckStatus) error {
-	if results != nil {
-		defer close(results)
-	}
-	if progress != nil {
-		defer close(progress)
-	}
-
-	totalFiles := int64(len(c.files))
-	totalBytes := c.TotalBytes()
-
-	var checkedFiles int64
-	var checkedBytes int64
-	var failures int64
-
-	for _, entry := range c.files {
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		default:
-		}
-
-		result := c.checkFile(entry, &checkedBytes)
-		if result.Status != StatusOK {
-			failures++
-		}
-		checkedFiles++
-
-		if results != nil {
-			results <- result
-		}
-
-		// Send progress (simplified - every file for now)
-		if progress != nil {
-			sendCheckStatus(progress, CheckStatus{
-				TotalFiles:   totalFiles,
-				CheckedFiles: checkedFiles,
-				TotalBytes:   totalBytes,
-				CheckedBytes: checkedBytes,
-				Failures:     failures,
-			})
-		}
-	}
-
-	return nil
-}
-
-func (c *Checker) checkFile(entry *mfer.MFFilePath, checkedBytes *int64) Result {
-	absPath := filepath.Join(c.basePath, entry.Path)
-
-	// Check if file exists
-	info, err := c.fs.Stat(absPath)
-	if err != nil {
-		if errors.Is(err, afero.ErrFileNotFound) || errors.Is(err, errors.New("file does not exist")) {
-			return Result{Path: entry.Path, Status: StatusMissing, Message: "file not found"}
-		}
-		// Check for "file does not exist" style errors
-		exists, _ := afero.Exists(c.fs, absPath)
-		if !exists {
-			return Result{Path: entry.Path, Status: StatusMissing, Message: "file not found"}
-		}
-		return Result{Path: entry.Path, Status: StatusError, Message: err.Error()}
-	}
-
-	// Check size
-	if info.Size() != entry.Size {
-		*checkedBytes += info.Size()
-		return Result{
-			Path:    entry.Path,
-			Status:  StatusSizeMismatch,
-			Message: "size mismatch",
-		}
-	}
-
-	// Open and hash file
-	f, err := c.fs.Open(absPath)
-	if err != nil {
-		return Result{Path: entry.Path, Status: StatusError, Message: err.Error()}
-	}
-	defer f.Close()
-
-	h := sha256.New()
-	n, err := io.Copy(h, f)
-	if err != nil {
-		return Result{Path: entry.Path, Status: StatusError, Message: err.Error()}
-	}
-	*checkedBytes += n
-
-	// Encode as multihash and compare
-	computed, err := multihash.Encode(h.Sum(nil), multihash.SHA2_256)
-	if err != nil {
-		return Result{Path: entry.Path, Status: StatusError, Message: err.Error()}
-	}
-
-	// Check against all hashes in manifest (at least one must match)
-	for _, hash := range entry.Hashes {
-		if bytes.Equal(computed, hash.MultiHash) {
-			return Result{Path: entry.Path, Status: StatusOK}
-		}
-	}
-
-	return Result{Path: entry.Path, Status: StatusHashMismatch, Message: "hash mismatch"}
-}
-
-// FindExtraFiles walks the filesystem and reports files not in the manifest.
-// Results are sent to the results channel. The channel is closed when done.
-func (c *Checker) FindExtraFiles(ctx context.Context, results chan<- Result) error {
-	if results != nil {
-		defer close(results)
-	}
-
-	return afero.Walk(c.fs, c.basePath, func(path string, info os.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
-
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		default:
-		}
-
-		// Skip directories
-		if info.IsDir() {
-			return nil
-		}
-
-		// Get relative path
-		relPath, err := filepath.Rel(c.basePath, path)
-		if err != nil {
-			return err
-		}
-
-		// Check if path is in manifest
-		if _, exists := c.manifestPaths[relPath]; !exists {
-			if results != nil {
-				results <- Result{
-					Path:    relPath,
-					Status:  StatusExtra,
-					Message: "not in manifest",
-				}
-			}
-		}
-
-		return nil
-	})
-}
-
-// sendCheckStatus sends a status update without blocking.
-func sendCheckStatus(ch chan<- CheckStatus, status CheckStatus) {
-	if ch == nil {
-		return
-	}
-	select {
-	case ch <- status:
-	default:
-	}
-}

internal/cli/check.go

@@ -3,6 +3,7 @@ package cli
 import (
 	"encoding/hex"
 	"fmt"
+	"io"
 	"path/filepath"
 	"strings"
 	"time"
@@ -34,29 +35,32 @@ func findManifest(fs afero.Fs, dir string) (string, error) {
 func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
 	log.Debug("checkManifestOperation()")
 
-	var manifestPath string
-	var err error
+	manifestPath, err := mfa.resolveManifestArg(ctx)
+	if err != nil {
+		return fmt.Errorf("check: %w", err)
+	}
 
-	if ctx.Args().Len() > 0 {
-		arg := ctx.Args().Get(0)
-		// Check if arg is a directory or a file
-		info, statErr := mfa.Fs.Stat(arg)
-		if statErr == nil && info.IsDir() {
-			// It's a directory, look for manifest inside
-			manifestPath, err = findManifest(mfa.Fs, arg)
-			if err != nil {
-				return err
-			}
-		} else {
-			// Treat as a file path
-			manifestPath = arg
+	// URL manifests need to be downloaded to a temp file for the checker
+	if isHTTPURL(manifestPath) {
+		rc, fetchErr := mfa.openManifestReader(manifestPath)
+		if fetchErr != nil {
+			return fmt.Errorf("check: %w", fetchErr)
 		}
-	} else {
-		// No argument, look in current directory
-		manifestPath, err = findManifest(mfa.Fs, ".")
-		if err != nil {
-			return err
+		tmpFile, tmpErr := afero.TempFile(mfa.Fs, "", "mfer-manifest-*.mf")
+		if tmpErr != nil {
+			_ = rc.Close()
+			return fmt.Errorf("check: failed to create temp file: %w", tmpErr)
 		}
+		tmpPath := tmpFile.Name()
+		_, cpErr := io.Copy(tmpFile, rc)
+		_ = rc.Close()
+		_ = tmpFile.Close()
+		if cpErr != nil {
+			_ = mfa.Fs.Remove(tmpPath)
+			return fmt.Errorf("check: failed to download manifest: %w", cpErr)
+		}
+		defer func() { _ = mfa.Fs.Remove(tmpPath) }()
+		manifestPath = tmpPath
 	}
 
 	basePath := ctx.String("base")

internal/cli/export.go

@@ -0,0 +1,72 @@
+package cli
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/urfave/cli/v2"
+	"sneak.berlin/go/mfer/mfer"
+)
+
+// ExportEntry represents a single file entry in the exported JSON output.
+type ExportEntry struct {
+	Path   string   `json:"path"`
+	Size   int64    `json:"size"`
+	Hashes []string `json:"hashes"`
+	Mtime  *string  `json:"mtime,omitempty"`
+	Ctime  *string  `json:"ctime,omitempty"`
+}
+
+func (mfa *CLIApp) exportManifestOperation(ctx *cli.Context) error {
+	pathOrURL, err := mfa.resolveManifestArg(ctx)
+	if err != nil {
+		return fmt.Errorf("export: %w", err)
+	}
+
+	rc, err := mfa.openManifestReader(pathOrURL)
+	if err != nil {
+		return fmt.Errorf("export: %w", err)
+	}
+	defer func() { _ = rc.Close() }()
+
+	manifest, err := mfer.NewManifestFromReader(rc)
+	if err != nil {
+		return fmt.Errorf("export: failed to parse manifest: %w", err)
+	}
+
+	files := manifest.Files()
+	entries := make([]ExportEntry, 0, len(files))
+
+	for _, f := range files {
+		entry := ExportEntry{
+			Path:   f.Path,
+			Size:   f.Size,
+			Hashes: make([]string, 0, len(f.Hashes)),
+		}
+
+		for _, h := range f.Hashes {
+			entry.Hashes = append(entry.Hashes, hex.EncodeToString(h.MultiHash))
+		}
+
+		if f.Mtime != nil {
+			t := time.Unix(f.Mtime.Seconds, int64(f.Mtime.Nanos)).UTC().Format(time.RFC3339Nano)
+			entry.Mtime = &t
+		}
+		if f.Ctime != nil {
+			t := time.Unix(f.Ctime.Seconds, int64(f.Ctime.Nanos)).UTC().Format(time.RFC3339Nano)
+			entry.Ctime = &t
+		}
+
+		entries = append(entries, entry)
+	}
+
+	enc := json.NewEncoder(mfa.Stdout)
+	enc.SetIndent("", "  ")
+	if err := enc.Encode(entries); err != nil {
+		return fmt.Errorf("export: failed to encode JSON: %w", err)
+	}
+
+	return nil
+}

internal/cli/export_test.go

@@ -0,0 +1,137 @@
+package cli
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/mfer/mfer"
+)
+
+// buildTestManifest creates a manifest from in-memory files and returns its bytes.
+func buildTestManifest(t *testing.T, files map[string][]byte) []byte {
+	t.Helper()
+	sourceFs := afero.NewMemMapFs()
+	for path, content := range files {
+		require.NoError(t, sourceFs.MkdirAll("/", 0o755))
+		require.NoError(t, afero.WriteFile(sourceFs, "/"+path, content, 0o644))
+	}
+
+	opts := &mfer.ScannerOptions{Fs: sourceFs}
+	s := mfer.NewScannerWithOptions(opts)
+	require.NoError(t, s.EnumerateFS(sourceFs, "/", nil))
+
+	var buf bytes.Buffer
+	require.NoError(t, s.ToManifest(context.Background(), &buf, nil))
+	return buf.Bytes()
+}
+
+func TestExportManifestOperation(t *testing.T) {
+	testFiles := map[string][]byte{
+		"hello.txt":    []byte("Hello, World!"),
+		"sub/file.txt": []byte("nested content"),
+	}
+	manifestData := buildTestManifest(t, testFiles)
+
+	// Write manifest to memfs
+	fs := afero.NewMemMapFs()
+	require.NoError(t, afero.WriteFile(fs, "/test.mf", manifestData, 0o644))
+
+	var stdout, stderr bytes.Buffer
+	exitCode := RunWithOptions(&RunOptions{
+		Appname: "mfer",
+		Args:    []string{"mfer", "export", "/test.mf"},
+		Stdin:   &bytes.Buffer{},
+		Stdout:  &stdout,
+		Stderr:  &stderr,
+		Fs:      fs,
+	})
+
+	require.Equal(t, 0, exitCode, "stderr: %s", stderr.String())
+
+	var entries []ExportEntry
+	require.NoError(t, json.Unmarshal(stdout.Bytes(), &entries))
+	assert.Len(t, entries, 2)
+
+	// Verify entries have expected fields
+	pathSet := make(map[string]bool)
+	for _, e := range entries {
+		pathSet[e.Path] = true
+		assert.NotEmpty(t, e.Hashes, "entry %s should have hashes", e.Path)
+		assert.Greater(t, e.Size, int64(0), "entry %s should have positive size", e.Path)
+	}
+	assert.True(t, pathSet["hello.txt"])
+	assert.True(t, pathSet["sub/file.txt"])
+}
+
+func TestExportFromHTTPURL(t *testing.T) {
+	testFiles := map[string][]byte{
+		"a.txt": []byte("aaa"),
+	}
+	manifestData := buildTestManifest(t, testFiles)
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/octet-stream")
+		_, _ = w.Write(manifestData)
+	}))
+	defer server.Close()
+
+	var stdout, stderr bytes.Buffer
+	exitCode := RunWithOptions(&RunOptions{
+		Appname: "mfer",
+		Args:    []string{"mfer", "export", server.URL + "/index.mf"},
+		Stdin:   &bytes.Buffer{},
+		Stdout:  &stdout,
+		Stderr:  &stderr,
+		Fs:      afero.NewMemMapFs(),
+	})
+
+	require.Equal(t, 0, exitCode, "stderr: %s", stderr.String())
+
+	var entries []ExportEntry
+	require.NoError(t, json.Unmarshal(stdout.Bytes(), &entries))
+	assert.Len(t, entries, 1)
+	assert.Equal(t, "a.txt", entries[0].Path)
+}
+
+func TestListFromHTTPURL(t *testing.T) {
+	testFiles := map[string][]byte{
+		"one.txt": []byte("1"),
+		"two.txt": []byte("22"),
+	}
+	manifestData := buildTestManifest(t, testFiles)
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write(manifestData)
+	}))
+	defer server.Close()
+
+	var stdout, stderr bytes.Buffer
+	exitCode := RunWithOptions(&RunOptions{
+		Appname: "mfer",
+		Args:    []string{"mfer", "list", server.URL + "/index.mf"},
+		Stdin:   &bytes.Buffer{},
+		Stdout:  &stdout,
+		Stderr:  &stderr,
+		Fs:      afero.NewMemMapFs(),
+	})
+
+	require.Equal(t, 0, exitCode, "stderr: %s", stderr.String())
+	output := stdout.String()
+	assert.Contains(t, output, "one.txt")
+	assert.Contains(t, output, "two.txt")
+}
+
+func TestIsHTTPURL(t *testing.T) {
+	assert.True(t, isHTTPURL("http://example.com/manifest.mf"))
+	assert.True(t, isHTTPURL("https://example.com/manifest.mf"))
+	assert.False(t, isHTTPURL("/local/path.mf"))
+	assert.False(t, isHTTPURL("relative/path.mf"))
+	assert.False(t, isHTTPURL("ftp://example.com/file"))
+}

internal/cli/fetch.go

@@ -67,7 +67,7 @@ func (mfa *CLIApp) fetchManifestOperation(ctx *cli.Context) error {
 	// Compute base URL (directory containing manifest)
 	baseURL, err := url.Parse(manifestURL)
 	if err != nil {
-		return err
+		return fmt.Errorf("fetch: invalid manifest URL: %w", err)
 	}
 	baseURL.Path = path.Dir(baseURL.Path)
 	if !strings.HasSuffix(baseURL.Path, "/") {
@@ -113,7 +113,7 @@ func (mfa *CLIApp) fetchManifestOperation(ctx *cli.Context) error {
 			return fmt.Errorf("invalid path in manifest: %w", err)
 		}
 
-		fileURL := baseURL.String() + f.Path
+		fileURL := baseURL.String() + encodeFilePath(f.Path)
 		log.Infof("fetching %s", f.Path)
 
 		if err := downloadFile(fileURL, localPath, f, progress); err != nil {
@@ -139,6 +139,15 @@ func (mfa *CLIApp) fetchManifestOperation(ctx *cli.Context) error {
 	return nil
 }
 
+// encodeFilePath URL-encodes each segment of a file path while preserving slashes.
+func encodeFilePath(p string) string {
+	segments := strings.Split(p, "/")
+	for i, seg := range segments {
+		segments[i] = url.PathEscape(seg)
+	}
+	return strings.Join(segments, "/")
+}
+
 // sanitizePath validates and sanitizes a file path from the manifest.
 // It prevents path traversal attacks and rejects unsafe paths.
 func sanitizePath(p string) (string, error) {
@@ -258,7 +267,7 @@ func downloadFile(fileURL, localPath string, entry *mfer.MFFilePath, progress ch
 	dir := filepath.Dir(localPath)
 	if dir != "" && dir != "." {
 		if err := os.MkdirAll(dir, 0o755); err != nil {
-			return err
+			return fmt.Errorf("failed to create directory %s: %w", dir, err)
 		}
 	}
 
@@ -278,9 +287,9 @@ func downloadFile(fileURL, localPath string, entry *mfer.MFFilePath, progress ch
 	}
 
 	// Fetch file
-	resp, err := http.Get(fileURL)
+	resp, err := http.Get(fileURL) //nolint:gosec // URL constructed from manifest base
 	if err != nil {
-		return err
+		return fmt.Errorf("HTTP request failed: %w", err)
 	}
 	defer func() { _ = resp.Body.Close() }()
 
@@ -298,7 +307,7 @@ func downloadFile(fileURL, localPath string, entry *mfer.MFFilePath, progress ch
 	// Create temp file
 	out, err := os.Create(tmpPath)
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to create temp file: %w", err)
 	}
 
 	// Set up hash computation

internal/cli/fetch_test.go

@@ -16,6 +16,29 @@ import (
 	"sneak.berlin/go/mfer/mfer"
 )
 
+func TestEncodeFilePath(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"file.txt", "file.txt"},
+		{"dir/file.txt", "dir/file.txt"},
+		{"my file.txt", "my%20file.txt"},
+		{"dir/my file.txt", "dir/my%20file.txt"},
+		{"file#1.txt", "file%231.txt"},
+		{"file?v=1.txt", "file%3Fv=1.txt"},
+		{"path/to/file with spaces.txt", "path/to/file%20with%20spaces.txt"},
+		{"100%done.txt", "100%25done.txt"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			result := encodeFilePath(tt.input)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
 func TestSanitizePath(t *testing.T) {
 	// Valid paths that should be accepted
 	validTests := []struct {

internal/cli/freshen.go

@@ -41,8 +41,8 @@ func (mfa *CLIApp) freshenManifestOperation(ctx *cli.Context) error {
 
 	basePath := ctx.String("base")
 	showProgress := ctx.Bool("progress")
-	includeDotfiles := ctx.Bool("IncludeDotfiles")
-	followSymlinks := ctx.Bool("FollowSymLinks")
+	includeDotfiles := ctx.Bool("include-dotfiles")
+	followSymlinks := ctx.Bool("follow-symlinks")
 
 	// Find manifest file
 	var manifestPath string
@@ -54,7 +54,7 @@ func (mfa *CLIApp) freshenManifestOperation(ctx *cli.Context) error {
 		if statErr == nil && info.IsDir() {
 			manifestPath, err = findManifest(mfa.Fs, arg)
 			if err != nil {
-				return err
+				return fmt.Errorf("freshen: %w", err)
 			}
 		} else {
 			manifestPath = arg
@@ -62,7 +62,7 @@ func (mfa *CLIApp) freshenManifestOperation(ctx *cli.Context) error {
 	} else {
 		manifestPath, err = findManifest(mfa.Fs, ".")
 		if err != nil {
-			return err
+			return fmt.Errorf("freshen: %w", err)
 		}
 	}
 
@@ -93,7 +93,7 @@ func (mfa *CLIApp) freshenManifestOperation(ctx *cli.Context) error {
 
 	absBase, err := filepath.Abs(basePath)
 	if err != nil {
-		return err
+		return fmt.Errorf("freshen: invalid base path: %w", err)
 	}
 
 	err = afero.Walk(mfa.Fs, absBase, func(path string, info fs.FileInfo, walkErr error) error {
@@ -104,7 +104,7 @@ func (mfa *CLIApp) freshenManifestOperation(ctx *cli.Context) error {
 		// Get relative path
 		relPath, err := filepath.Rel(absBase, path)
 		if err != nil {
-			return err
+			return fmt.Errorf("freshen: failed to compute relative path for %s: %w", path, err)
 		}
 
 		// Skip the manifest file itself
@@ -226,6 +226,9 @@ func (mfa *CLIApp) freshenManifestOperation(ctx *cli.Context) error {
 	var hashedBytes int64
 
 	builder := mfer.NewBuilder()
+	if ctx.Bool("include-timestamps") {
+		builder.SetIncludeTimestamps(true)
+	}
 
 	// Set up signing options if sign-key is provided
 	if signKey := ctx.String("sign-key"); signKey != "" {

internal/cli/gen.go

@@ -20,9 +20,16 @@ func (mfa *CLIApp) generateManifestOperation(ctx *cli.Context) error {
 	log.Debug("generateManifestOperation()")
 
 	opts := &mfer.ScannerOptions{
-		IncludeDotfiles: ctx.Bool("IncludeDotfiles"),
-		FollowSymLinks:  ctx.Bool("FollowSymLinks"),
-		Fs:              mfa.Fs,
+		IncludeDotfiles:   ctx.Bool("include-dotfiles"),
+		FollowSymLinks:    ctx.Bool("follow-symlinks"),
+		IncludeTimestamps: ctx.Bool("include-timestamps"),
+		Fs:                mfa.Fs,
+	}
+
+	// Set seed for deterministic UUID if provided
+	if seed := ctx.String("seed"); seed != "" {
+		opts.Seed = seed
+		log.Infof("using deterministic seed for manifest UUID")
 	}
 
 	// Set up signing options if sign-key is provided
@@ -59,7 +66,7 @@ func (mfa *CLIApp) generateManifestOperation(ctx *cli.Context) error {
 	if args.Len() == 0 {
 		// Default to current directory
 		if err := s.EnumeratePath(".", enumProgress); err != nil {
-			return err
+			return fmt.Errorf("generate: failed to enumerate current directory: %w", err)
 		}
 	} else {
 		// Collect and validate all paths first
@@ -68,7 +75,7 @@ func (mfa *CLIApp) generateManifestOperation(ctx *cli.Context) error {
 			inputPath := args.Get(i)
 			ap, err := filepath.Abs(inputPath)
 			if err != nil {
-				return err
+				return fmt.Errorf("generate: invalid path %q: %w", inputPath, err)
 			}
 			// Validate path exists before adding to list
 			if exists, _ := afero.Exists(mfa.Fs, ap); !exists {
@@ -78,7 +85,7 @@ func (mfa *CLIApp) generateManifestOperation(ctx *cli.Context) error {
 			paths = append(paths, ap)
 		}
 		if err := s.EnumeratePaths(enumProgress, paths...); err != nil {
-			return err
+			return fmt.Errorf("generate: failed to enumerate paths: %w", err)
 		}
 	}
 	enumWg.Wait()

internal/cli/list.go

@@ -16,32 +16,20 @@ func (mfa *CLIApp) listManifestOperation(ctx *cli.Context) error {
 	longFormat := ctx.Bool("long")
 	print0 := ctx.Bool("print0")
 
-	// Find manifest file
-	var manifestPath string
-	var err error
-
-	if ctx.Args().Len() > 0 {
-		arg := ctx.Args().Get(0)
-		info, statErr := mfa.Fs.Stat(arg)
-		if statErr == nil && info.IsDir() {
-			manifestPath, err = findManifest(mfa.Fs, arg)
-			if err != nil {
-				return err
-			}
-		} else {
-			manifestPath = arg
-		}
-	} else {
-		manifestPath, err = findManifest(mfa.Fs, ".")
-		if err != nil {
-			return err
-		}
+	pathOrURL, err := mfa.resolveManifestArg(ctx)
+	if err != nil {
+		return fmt.Errorf("list: %w", err)
 	}
 
-	// Load manifest
-	manifest, err := mfer.NewManifestFromFile(mfa.Fs, manifestPath)
+	rc, err := mfa.openManifestReader(pathOrURL)
 	if err != nil {
-		return fmt.Errorf("failed to load manifest: %w", err)
+		return fmt.Errorf("list: %w", err)
+	}
+	defer func() { _ = rc.Close() }()
+
+	manifest, err := mfer.NewManifestFromReader(rc)
+	if err != nil {
+		return fmt.Errorf("list: failed to parse manifest: %w", err)
 	}
 
 	files := manifest.Files()

internal/cli/manifest_loader.go

@@ -0,0 +1,56 @@
+package cli
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/urfave/cli/v2"
+)
+
+// isHTTPURL returns true if the string starts with http:// or https://.
+func isHTTPURL(s string) bool {
+	return strings.HasPrefix(s, "http://") || strings.HasPrefix(s, "https://")
+}
+
+// openManifestReader opens a manifest from a path or URL and returns a ReadCloser.
+// The caller must close the returned reader.
+func (mfa *CLIApp) openManifestReader(pathOrURL string) (io.ReadCloser, error) {
+	if isHTTPURL(pathOrURL) {
+		client := &http.Client{Timeout: 30 * time.Second}
+		resp, err := client.Get(pathOrURL) //nolint:gosec // user-provided URL is intentional
+		if err != nil {
+			return nil, fmt.Errorf("failed to fetch %s: %w", pathOrURL, err)
+		}
+		if resp.StatusCode != http.StatusOK {
+			_ = resp.Body.Close()
+			return nil, fmt.Errorf("failed to fetch %s: HTTP %d", pathOrURL, resp.StatusCode)
+		}
+		return resp.Body, nil
+	}
+	f, err := mfa.Fs.Open(pathOrURL)
+	if err != nil {
+		return nil, err
+	}
+	return f, nil
+}
+
+// resolveManifestArg resolves the manifest path from CLI arguments.
+// HTTP(S) URLs are returned as-is. Directories are searched for index.mf/.index.mf.
+// If no argument is given, the current directory is searched.
+func (mfa *CLIApp) resolveManifestArg(ctx *cli.Context) (string, error) {
+	if ctx.Args().Len() > 0 {
+		arg := ctx.Args().Get(0)
+		if isHTTPURL(arg) {
+			return arg, nil
+		}
+		info, statErr := mfa.Fs.Stat(arg)
+		if statErr == nil && info.IsDir() {
+			return findManifest(mfa.Fs, arg)
+		}
+		return arg, nil
+	}
+	return findManifest(mfa.Fs, ".")
+}

internal/cli/mfer.go

@@ -123,14 +123,15 @@ func (mfa *CLIApp) run(args []string) {
 				},
 				Flags: append(commonFlags(),
 					&cli.BoolFlag{
-						Name:    "FollowSymLinks",
-						Aliases: []string{"follow-symlinks"},
+						Name:    "follow-symlinks",
+						Aliases: []string{"L"},
 						Usage:   "Resolve encountered symlinks",
 					},
 					&cli.BoolFlag{
-						Name:    "IncludeDotfiles",
-						Aliases: []string{"include-dotfiles"},
-						Usage:   "Include dot (hidden) files (excluded by default)",
+						Name:    "include-dotfiles",
+						Aliases: []string{"IncludeDotfiles"},
+
+						Usage: "Include dot (hidden) files (excluded by default)",
 					},
 					&cli.StringFlag{
 						Name:    "output",
@@ -154,6 +155,15 @@ func (mfa *CLIApp) run(args []string) {
 						Usage:   "GPG key ID to sign the manifest with",
 						EnvVars: []string{"MFER_SIGN_KEY"},
 					},
+					&cli.StringFlag{
+						Name:    "seed",
+						Usage:   "Seed value for deterministic manifest UUID",
+						EnvVars: []string{"MFER_SEED"},
+					},
+					&cli.BoolFlag{
+						Name:  "include-timestamps",
+						Usage: "Include createdAt timestamp in manifest (omitted by default for determinism)",
+					},
 				),
 			},
 			{
@@ -206,14 +216,15 @@ func (mfa *CLIApp) run(args []string) {
 						Usage:   "Base directory for resolving relative paths",
 					},
 					&cli.BoolFlag{
-						Name:    "FollowSymLinks",
-						Aliases: []string{"follow-symlinks"},
+						Name:    "follow-symlinks",
+						Aliases: []string{"L"},
 						Usage:   "Resolve encountered symlinks",
 					},
 					&cli.BoolFlag{
-						Name:    "IncludeDotfiles",
-						Aliases: []string{"include-dotfiles"},
-						Usage:   "Include dot (hidden) files (excluded by default)",
+						Name:    "include-dotfiles",
+						Aliases: []string{"IncludeDotfiles"},
+
+						Usage: "Include dot (hidden) files (excluded by default)",
 					},
 					&cli.BoolFlag{
 						Name:    "progress",
@@ -226,8 +237,20 @@ func (mfa *CLIApp) run(args []string) {
 						Usage:   "GPG key ID to sign the manifest with",
 						EnvVars: []string{"MFER_SIGN_KEY"},
 					},
+					&cli.BoolFlag{
+						Name:  "include-timestamps",
+						Usage: "Include createdAt timestamp in manifest (omitted by default for determinism)",
+					},
 				),
 			},
+			{
+				Name:      "export",
+				Usage:     "Export manifest contents as JSON",
+				ArgsUsage: "[manifest file or URL]",
+				Action: func(c *cli.Context) error {
+					return mfa.exportManifestOperation(c)
+				},
+			},
 			{
 				Name:  "version",
 				Usage: "Show version",
@@ -269,7 +292,7 @@ func (mfa *CLIApp) run(args []string) {
 		},
 	}
 
-	mfa.app.HideVersion = true
+	mfa.app.HideVersion = false
 	err := mfa.app.Run(args)
 	if err != nil {
 		mfa.exitCode = 1

internal/scanner/scanner.go

@@ -1,373 +0,0 @@
-package scanner
-
-import (
-	"context"
-	"io"
-	"io/fs"
-	"path"
-	"path/filepath"
-	"strings"
-	"sync"
-	"time"
-
-	"github.com/spf13/afero"
-	"sneak.berlin/go/mfer/mfer"
-)
-
-// Phase 1: Enumeration
-// ---------------------
-// Walking directories and calling stat() on files to collect metadata.
-// Builds the list of files to be scanned. Relatively fast (metadata only).
-
-// EnumerateStatus contains progress information for the enumeration phase.
-type EnumerateStatus struct {
-	FilesFound int64 // Number of files discovered so far
-	BytesFound int64 // Total size of discovered files (from stat)
-}
-
-// Phase 2: Scan (ToManifest)
-// --------------------------
-// Reading file contents and computing hashes for manifest generation.
-// This is the expensive phase that reads all file data.
-
-// ScanStatus contains progress information for the scan phase.
-type ScanStatus struct {
-	TotalFiles   int64   // Total number of files to scan
-	ScannedFiles int64   // Number of files scanned so far
-	TotalBytes   int64   // Total bytes to read (sum of all file sizes)
-	ScannedBytes int64   // Bytes read so far
-	BytesPerSec  float64 // Current throughput rate
-}
-
-// Options configures scanner behavior.
-type Options struct {
-	IgnoreDotfiles bool     // Skip files and directories starting with a dot
-	FollowSymLinks bool     // Resolve symlinks instead of skipping them
-	Fs             afero.Fs // Filesystem to use, defaults to OsFs if nil
-}
-
-// FileEntry represents a file that has been enumerated.
-type FileEntry struct {
-	Path    string    // Relative path (used in manifest)
-	AbsPath string    // Absolute path (used for reading file content)
-	Size    int64     // File size in bytes
-	Mtime   time.Time // Last modification time
-	Ctime   time.Time // Creation time (platform-dependent)
-}
-
-// Scanner accumulates files and generates manifests from them.
-type Scanner struct {
-	mu      sync.RWMutex
-	files   []*FileEntry
-	options *Options
-	fs      afero.Fs
-}
-
-// New creates a new Scanner with default options.
-func New() *Scanner {
-	return NewWithOptions(nil)
-}
-
-// NewWithOptions creates a new Scanner with the given options.
-func NewWithOptions(opts *Options) *Scanner {
-	if opts == nil {
-		opts = &Options{}
-	}
-	fs := opts.Fs
-	if fs == nil {
-		fs = afero.NewOsFs()
-	}
-	return &Scanner{
-		files:   make([]*FileEntry, 0),
-		options: opts,
-		fs:      fs,
-	}
-}
-
-// EnumerateFile adds a single file to the scanner, calling stat() to get metadata.
-func (s *Scanner) EnumerateFile(filePath string) error {
-	abs, err := filepath.Abs(filePath)
-	if err != nil {
-		return err
-	}
-	info, err := s.fs.Stat(abs)
-	if err != nil {
-		return err
-	}
-	// For single files, use the filename as the relative path
-	basePath := filepath.Dir(abs)
-	return s.enumerateFileWithInfo(filepath.Base(abs), basePath, info, nil)
-}
-
-// EnumeratePath walks a directory path and adds all files to the scanner.
-// If progress is non-nil, status updates are sent as files are discovered.
-// The progress channel is closed when the method returns.
-func (s *Scanner) EnumeratePath(inputPath string, progress chan<- EnumerateStatus) error {
-	if progress != nil {
-		defer close(progress)
-	}
-	abs, err := filepath.Abs(inputPath)
-	if err != nil {
-		return err
-	}
-	afs := afero.NewReadOnlyFs(afero.NewBasePathFs(s.fs, abs))
-	return s.enumerateFS(afs, abs, progress)
-}
-
-// EnumeratePaths walks multiple directory paths and adds all files to the scanner.
-// If progress is non-nil, status updates are sent as files are discovered.
-// The progress channel is closed when the method returns.
-func (s *Scanner) EnumeratePaths(progress chan<- EnumerateStatus, inputPaths ...string) error {
-	if progress != nil {
-		defer close(progress)
-	}
-	for _, p := range inputPaths {
-		abs, err := filepath.Abs(p)
-		if err != nil {
-			return err
-		}
-		afs := afero.NewReadOnlyFs(afero.NewBasePathFs(s.fs, abs))
-		if err := s.enumerateFS(afs, abs, progress); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-// EnumerateFS walks an afero filesystem and adds all files to the scanner.
-// If progress is non-nil, status updates are sent as files are discovered.
-// The progress channel is closed when the method returns.
-// basePath is used to compute absolute paths for file reading.
-func (s *Scanner) EnumerateFS(afs afero.Fs, basePath string, progress chan<- EnumerateStatus) error {
-	if progress != nil {
-		defer close(progress)
-	}
-	return s.enumerateFS(afs, basePath, progress)
-}
-
-// enumerateFS is the internal implementation that doesn't close the progress channel.
-func (s *Scanner) enumerateFS(afs afero.Fs, basePath string, progress chan<- EnumerateStatus) error {
-	return afero.Walk(afs, "/", func(p string, info fs.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
-		if s.options.IgnoreDotfiles && pathIsHidden(p) {
-			if info.IsDir() {
-				return filepath.SkipDir
-			}
-			return nil
-		}
-		return s.enumerateFileWithInfo(p, basePath, info, progress)
-	})
-}
-
-// enumerateFileWithInfo adds a file with pre-existing fs.FileInfo.
-func (s *Scanner) enumerateFileWithInfo(filePath string, basePath string, info fs.FileInfo, progress chan<- EnumerateStatus) error {
-	if info.IsDir() {
-		// Manifests contain only files, directories are implied
-		return nil
-	}
-
-	// Clean the path - remove leading slash if present
-	cleanPath := filePath
-	if len(cleanPath) > 0 && cleanPath[0] == '/' {
-		cleanPath = cleanPath[1:]
-	}
-
-	// Compute absolute path for file reading
-	absPath := filepath.Join(basePath, cleanPath)
-
-	entry := &FileEntry{
-		Path:    cleanPath,
-		AbsPath: absPath,
-		Size:    info.Size(),
-		Mtime:   info.ModTime(),
-		// Note: Ctime not available from fs.FileInfo on all platforms
-		// Will need platform-specific code to extract it
-	}
-
-	s.mu.Lock()
-	s.files = append(s.files, entry)
-	filesFound := int64(len(s.files))
-	var bytesFound int64
-	for _, f := range s.files {
-		bytesFound += f.Size
-	}
-	s.mu.Unlock()
-
-	sendEnumerateStatus(progress, EnumerateStatus{
-		FilesFound: filesFound,
-		BytesFound: bytesFound,
-	})
-
-	return nil
-}
-
-// Files returns a copy of all files added to the scanner.
-func (s *Scanner) Files() []*FileEntry {
-	s.mu.RLock()
-	defer s.mu.RUnlock()
-	out := make([]*FileEntry, len(s.files))
-	copy(out, s.files)
-	return out
-}
-
-// FileCount returns the number of files in the scanner.
-func (s *Scanner) FileCount() int64 {
-	s.mu.RLock()
-	defer s.mu.RUnlock()
-	return int64(len(s.files))
-}
-
-// TotalBytes returns the total size of all files in the scanner.
-func (s *Scanner) TotalBytes() int64 {
-	s.mu.RLock()
-	defer s.mu.RUnlock()
-	var total int64
-	for _, f := range s.files {
-		total += f.Size
-	}
-	return total
-}
-
-// ToManifest reads all file contents, computes hashes, and generates a manifest.
-// If progress is non-nil, status updates are sent approximately once per second.
-// The progress channel is closed when the method returns.
-// The manifest is written to the provided io.Writer.
-func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- ScanStatus) error {
-	if progress != nil {
-		defer close(progress)
-	}
-
-	s.mu.RLock()
-	files := make([]*FileEntry, len(s.files))
-	copy(files, s.files)
-	totalFiles := int64(len(files))
-	var totalBytes int64
-	for _, f := range files {
-		totalBytes += f.Size
-	}
-	s.mu.RUnlock()
-
-	builder := mfer.NewBuilder()
-
-	var scannedFiles int64
-	var scannedBytes int64
-	lastProgressTime := time.Now()
-	startTime := time.Now()
-
-	for _, entry := range files {
-		// Check for cancellation
-		select {
-		case <-ctx.Done():
-			return ctx.Err()
-		default:
-		}
-
-		// Open file
-		f, err := s.fs.Open(entry.AbsPath)
-		if err != nil {
-			return err
-		}
-
-		// Add to manifest with progress callback
-		bytesRead, err := builder.AddFile(
-			entry.Path,
-			entry.Size,
-			entry.Mtime,
-			f,
-			func(fileBytes int64) {
-				// Send progress at most once per second
-				now := time.Now()
-				if progress != nil && now.Sub(lastProgressTime) >= time.Second {
-					elapsed := now.Sub(startTime).Seconds()
-					currentBytes := scannedBytes + fileBytes
-					var rate float64
-					if elapsed > 0 {
-						rate = float64(currentBytes) / elapsed
-					}
-					sendScanStatus(progress, ScanStatus{
-						TotalFiles:   totalFiles,
-						ScannedFiles: scannedFiles,
-						TotalBytes:   totalBytes,
-						ScannedBytes: currentBytes,
-						BytesPerSec:  rate,
-					})
-					lastProgressTime = now
-				}
-			},
-		)
-		f.Close()
-
-		if err != nil {
-			return err
-		}
-
-		scannedFiles++
-		scannedBytes += bytesRead
-	}
-
-	// Send final progress
-	if progress != nil {
-		elapsed := time.Since(startTime).Seconds()
-		var rate float64
-		if elapsed > 0 {
-			rate = float64(scannedBytes) / elapsed
-		}
-		sendScanStatus(progress, ScanStatus{
-			TotalFiles:   totalFiles,
-			ScannedFiles: scannedFiles,
-			TotalBytes:   totalBytes,
-			ScannedBytes: scannedBytes,
-			BytesPerSec:  rate,
-		})
-	}
-
-	// Build and write manifest
-	return builder.Build(w)
-}
-
-// pathIsHidden returns true if the path or any of its parent directories
-// start with a dot (hidden files/directories).
-func pathIsHidden(p string) bool {
-	tp := path.Clean(p)
-	if strings.HasPrefix(tp, ".") {
-		return true
-	}
-	for {
-		d, f := path.Split(tp)
-		if strings.HasPrefix(f, ".") {
-			return true
-		}
-		if d == "" {
-			return false
-		}
-		tp = d[0 : len(d)-1] // trim trailing slash from dir
-	}
-}
-
-// sendEnumerateStatus sends a status update without blocking.
-// If the channel is full, the update is dropped.
-func sendEnumerateStatus(ch chan<- EnumerateStatus, status EnumerateStatus) {
-	if ch == nil {
-		return
-	}
-	select {
-	case ch <- status:
-	default:
-		// Channel full, drop this update
-	}
-}
-
-// sendScanStatus sends a status update without blocking.
-// If the channel is full, the update is dropped.
-func sendScanStatus(ch chan<- ScanStatus, status ScanStatus) {
-	if ch == nil {
-		return
-	}
-	select {
-	case ch <- status:
-	default:
-		// Channel full, drop this update
-	}
-}

mfer/builder.go

@@ -5,12 +5,46 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"sort"
+	"strings"
 	"sync"
 	"time"
+	"unicode/utf8"
 
 	"github.com/multiformats/go-multihash"
 )
 
+// ValidatePath checks that a file path conforms to manifest path invariants:
+//   - Must be valid UTF-8
+//   - Must use forward slashes only (no backslashes)
+//   - Must be relative (no leading /)
+//   - Must not contain ".." segments
+//   - Must not contain empty segments (no "//")
+//   - Must not be empty
+func ValidatePath(p string) error {
+	if p == "" {
+		return errors.New("path cannot be empty")
+	}
+	if !utf8.ValidString(p) {
+		return fmt.Errorf("path %q is not valid UTF-8", p)
+	}
+	if strings.ContainsRune(p, '\\') {
+		return fmt.Errorf("path %q contains backslash; use forward slashes only", p)
+	}
+	if strings.HasPrefix(p, "/") {
+		return fmt.Errorf("path %q is absolute; must be relative", p)
+	}
+	for _, seg := range strings.Split(p, "/") {
+		if seg == "" {
+			return fmt.Errorf("path %q contains empty segment", p)
+		}
+		if seg == ".." {
+			return fmt.Errorf("path %q contains '..' segment", p)
+		}
+	}
+	return nil
+}
+
 // RelFilePath represents a relative file path within a manifest.
 type RelFilePath string
 
@@ -51,10 +85,20 @@ type FileHashProgress struct {
 
 // Builder constructs a manifest by adding files one at a time.
 type Builder struct {
-	mu             sync.Mutex
-	files          []*MFFilePath
-	createdAt      time.Time
-	signingOptions *SigningOptions
+	mu                sync.Mutex
+	files             []*MFFilePath
+	createdAt         time.Time
+	includeTimestamps bool
+	signingOptions    *SigningOptions
+	fixedUUID         []byte // if set, use this UUID instead of generating one
+}
+
+// SetSeed derives a deterministic UUID from the given seed string.
+// The seed is hashed once with SHA-256 and the first 16 bytes are used
+// as a fixed UUID for the manifest.
+func (b *Builder) SetSeed(seed string) {
+	hash := sha256.Sum256([]byte(seed))
+	b.fixedUUID = hash[:16]
 }
 
 // NewBuilder creates a new Builder.
@@ -75,6 +119,10 @@ func (b *Builder) AddFile(
 	reader io.Reader,
 	progress chan<- FileHashProgress,
 ) (FileSize, error) {
+	if err := ValidatePath(string(path)); err != nil {
+		return 0, err
+	}
+
 	// Create hash writer
 	h := sha256.New()
 
@@ -147,8 +195,8 @@ func (b *Builder) FileCount() int {
 // This is useful when the hash is already known (e.g., from an existing manifest).
 // Returns an error if path is empty, size is negative, or hash is nil/empty.
 func (b *Builder) AddFileWithHash(path RelFilePath, size FileSize, mtime ModTime, hash Multihash) error {
-	if path == "" {
-		return errors.New("path cannot be empty")
+	if err := ValidatePath(string(path)); err != nil {
+		return fmt.Errorf("add file: %w", err)
 	}
 	if size < 0 {
 		return errors.New("size cannot be negative")
@@ -172,6 +220,14 @@ func (b *Builder) AddFileWithHash(path RelFilePath, size FileSize, mtime ModTime
 	return nil
 }
 
+// SetIncludeTimestamps controls whether the manifest includes a createdAt timestamp.
+// By default timestamps are omitted for deterministic output.
+func (b *Builder) SetIncludeTimestamps(include bool) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	b.includeTimestamps = include
+}
+
 // SetSigningOptions sets the GPG signing options for the manifest.
 // If opts is non-nil, the manifest will be signed when Build() is called.
 func (b *Builder) SetSigningOptions(opts *SigningOptions) {
@@ -185,30 +241,41 @@ func (b *Builder) Build(w io.Writer) error {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
+	// Sort files by path for deterministic output
+	sort.Slice(b.files, func(i, j int) bool {
+		return b.files[i].Path < b.files[j].Path
+	})
+
 	// Create inner manifest
 	inner := &MFFile{
-		Version:   MFFile_VERSION_ONE,
-		CreatedAt: newTimestampFromTime(b.createdAt),
-		Files:     b.files,
+		Version: MFFile_VERSION_ONE,
+		Files:   b.files,
+	}
+	if b.includeTimestamps {
+		inner.CreatedAt = newTimestampFromTime(b.createdAt)
 	}
 
 	// Create a temporary manifest to use existing serialization
 	m := &manifest{
 		pbInner:        inner,
 		signingOptions: b.signingOptions,
+		fixedUUID:      b.fixedUUID,
 	}
 
 	// Generate outer wrapper
 	if err := m.generateOuter(); err != nil {
-		return err
+		return fmt.Errorf("build: generate outer: %w", err)
 	}
 
 	// Generate final output
 	if err := m.generate(); err != nil {
-		return err
+		return fmt.Errorf("build: generate: %w", err)
 	}
 
 	// Write to output
 	_, err := w.Write(m.output.Bytes())
-	return err
+	if err != nil {
+		return fmt.Errorf("build: write output: %w", err)
+	}
+	return nil
 }

mfer/builder_test.go

@@ -92,6 +92,230 @@ func TestBuilderBuild(t *testing.T) {
 	assert.True(t, strings.HasPrefix(buf.String(), MAGIC))
 }
 
+func TestNewTimestampFromTimeExtremeDate(t *testing.T) {
+	// Regression test: newTimestampFromTime used UnixNano() which panics
+	// for dates outside ~1678-2262. Now uses Nanosecond() which is safe.
+	tests := []struct {
+		name string
+		time time.Time
+	}{
+		{"zero time", time.Time{}},
+		{"year 1000", time.Date(1000, 1, 1, 0, 0, 0, 0, time.UTC)},
+		{"year 3000", time.Date(3000, 1, 1, 0, 0, 0, 123456789, time.UTC)},
+		{"unix epoch", time.Unix(0, 0)},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Should not panic
+			ts := newTimestampFromTime(tt.time)
+			assert.Equal(t, tt.time.Unix(), ts.Seconds)
+			assert.Equal(t, int32(tt.time.Nanosecond()), ts.Nanos)
+		})
+	}
+}
+
+func TestBuilderDeterministicOutput(t *testing.T) {
+	buildManifest := func() []byte {
+		b := NewBuilder()
+		// Use a fixed createdAt and UUID so output is reproducible
+		b.createdAt = time.Date(2025, 1, 1, 0, 0, 0, 0, time.UTC)
+		b.fixedUUID = make([]byte, 16) // all zeros
+
+		mtime := ModTime(time.Date(2025, 6, 1, 0, 0, 0, 0, time.UTC))
+
+		// Add files in reverse order to test sorting
+		files := []struct {
+			path    string
+			content string
+		}{
+			{"c/file.txt", "content c"},
+			{"a/file.txt", "content a"},
+			{"b/file.txt", "content b"},
+		}
+		for _, f := range files {
+			r := bytes.NewReader([]byte(f.content))
+			_, err := b.AddFile(RelFilePath(f.path), FileSize(len(f.content)), mtime, r, nil)
+			require.NoError(t, err)
+		}
+
+		var buf bytes.Buffer
+		err := b.Build(&buf)
+		require.NoError(t, err)
+		return buf.Bytes()
+	}
+
+	out1 := buildManifest()
+	out2 := buildManifest()
+	assert.Equal(t, out1, out2, "two builds with same input should produce byte-identical output")
+}
+
+func TestSetSeedDeterministic(t *testing.T) {
+	b1 := NewBuilder()
+	b1.SetSeed("test-seed-value")
+	b2 := NewBuilder()
+	b2.SetSeed("test-seed-value")
+	assert.Equal(t, b1.fixedUUID, b2.fixedUUID, "same seed should produce same UUID")
+	assert.Len(t, b1.fixedUUID, 16, "UUID should be 16 bytes")
+
+	b3 := NewBuilder()
+	b3.SetSeed("different-seed")
+	assert.NotEqual(t, b1.fixedUUID, b3.fixedUUID, "different seeds should produce different UUIDs")
+}
+
+func TestValidatePath(t *testing.T) {
+	valid := []string{
+		"file.txt",
+		"dir/file.txt",
+		"a/b/c/d.txt",
+		"file with spaces.txt",
+		"日本語.txt",
+	}
+	for _, p := range valid {
+		t.Run("valid:"+p, func(t *testing.T) {
+			assert.NoError(t, ValidatePath(p))
+		})
+	}
+
+	invalid := []struct {
+		path string
+		desc string
+	}{
+		{"", "empty"},
+		{"/absolute", "absolute path"},
+		{"has\\backslash", "backslash"},
+		{"has/../traversal", "dot-dot segment"},
+		{"has//double", "empty segment"},
+		{"..", "just dot-dot"},
+		{string([]byte{0xff, 0xfe}), "invalid UTF-8"},
+	}
+	for _, tt := range invalid {
+		t.Run("invalid:"+tt.desc, func(t *testing.T) {
+			assert.Error(t, ValidatePath(tt.path))
+		})
+	}
+}
+
+func TestBuilderAddFileSizeMismatch(t *testing.T) {
+	b := NewBuilder()
+	content := []byte("short")
+	reader := bytes.NewReader(content)
+
+	// Declare wrong size
+	_, err := b.AddFile("test.txt", FileSize(100), ModTime(time.Now()), reader, nil)
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "size mismatch")
+}
+
+func TestBuilderAddFileInvalidPath(t *testing.T) {
+	b := NewBuilder()
+	content := []byte("data")
+	reader := bytes.NewReader(content)
+
+	_, err := b.AddFile("", FileSize(len(content)), ModTime(time.Now()), reader, nil)
+	assert.Error(t, err)
+
+	reader.Reset(content)
+	_, err = b.AddFile("/absolute", FileSize(len(content)), ModTime(time.Now()), reader, nil)
+	assert.Error(t, err)
+}
+
+func TestBuilderAddFileWithProgress(t *testing.T) {
+	b := NewBuilder()
+	content := bytes.Repeat([]byte("x"), 1000)
+	reader := bytes.NewReader(content)
+	progress := make(chan FileHashProgress, 100)
+
+	bytesRead, err := b.AddFile("test.txt", FileSize(len(content)), ModTime(time.Now()), reader, progress)
+	close(progress)
+	require.NoError(t, err)
+	assert.Equal(t, FileSize(1000), bytesRead)
+
+	var updates []FileHashProgress
+	for p := range progress {
+		updates = append(updates, p)
+	}
+	assert.NotEmpty(t, updates)
+	// Last update should show all bytes
+	assert.Equal(t, FileSize(1000), updates[len(updates)-1].BytesRead)
+}
+
+func TestBuilderBuildRoundTrip(t *testing.T) {
+	// Build a manifest, deserialize it, verify all fields survive round-trip
+	b := NewBuilder()
+	now := time.Date(2025, 6, 15, 12, 0, 0, 0, time.UTC)
+
+	files := []struct {
+		path    string
+		content []byte
+	}{
+		{"alpha.txt", []byte("alpha content")},
+		{"beta/gamma.txt", []byte("gamma content")},
+		{"beta/delta.txt", []byte("delta content")},
+	}
+
+	for _, f := range files {
+		reader := bytes.NewReader(f.content)
+		_, err := b.AddFile(RelFilePath(f.path), FileSize(len(f.content)), ModTime(now), reader, nil)
+		require.NoError(t, err)
+	}
+
+	var buf bytes.Buffer
+	require.NoError(t, b.Build(&buf))
+
+	m, err := NewManifestFromReader(&buf)
+	require.NoError(t, err)
+
+	mfiles := m.Files()
+	require.Len(t, mfiles, 3)
+
+	// Verify sorted order
+	assert.Equal(t, "alpha.txt", mfiles[0].Path)
+	assert.Equal(t, "beta/delta.txt", mfiles[1].Path)
+	assert.Equal(t, "beta/gamma.txt", mfiles[2].Path)
+
+	// Verify sizes
+	assert.Equal(t, int64(len("alpha content")), mfiles[0].Size)
+
+	// Verify hashes are present
+	for _, f := range mfiles {
+		require.NotEmpty(t, f.Hashes, "file %s should have hashes", f.Path)
+		assert.NotEmpty(t, f.Hashes[0].MultiHash)
+	}
+}
+
+func TestNewManifestFromReaderInvalidMagic(t *testing.T) {
+	_, err := NewManifestFromReader(bytes.NewReader([]byte("NOT_VALID")))
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "invalid file format")
+}
+
+func TestNewManifestFromReaderEmpty(t *testing.T) {
+	_, err := NewManifestFromReader(bytes.NewReader([]byte{}))
+	assert.Error(t, err)
+}
+
+func TestNewManifestFromReaderTruncated(t *testing.T) {
+	// Just the magic with nothing after
+	_, err := NewManifestFromReader(bytes.NewReader([]byte(MAGIC)))
+	assert.Error(t, err)
+}
+
+func TestManifestString(t *testing.T) {
+	b := NewBuilder()
+	content := []byte("test")
+	reader := bytes.NewReader(content)
+	_, err := b.AddFile("test.txt", FileSize(len(content)), ModTime(time.Now()), reader, nil)
+	require.NoError(t, err)
+
+	var buf bytes.Buffer
+	require.NoError(t, b.Build(&buf))
+
+	m, err := NewManifestFromReader(&buf)
+	require.NoError(t, err)
+	assert.Contains(t, m.String(), "count=1")
+}
+
 func TestBuilderBuildEmpty(t *testing.T) {
 	b := NewBuilder()
 
@@ -102,3 +326,62 @@ func TestBuilderBuildEmpty(t *testing.T) {
 	// Should still produce valid manifest with 0 files
 	assert.True(t, strings.HasPrefix(buf.String(), MAGIC))
 }
+
+func TestBuilderOmitsCreatedAtByDefault(t *testing.T) {
+	b := NewBuilder()
+	content := []byte("hello")
+	_, err := b.AddFile("test.txt", FileSize(len(content)), ModTime(time.Now()), bytes.NewReader(content), nil)
+	require.NoError(t, err)
+
+	var buf bytes.Buffer
+	require.NoError(t, b.Build(&buf))
+
+	m, err := NewManifestFromReader(&buf)
+	require.NoError(t, err)
+	assert.Nil(t, m.pbInner.CreatedAt, "createdAt should be nil by default for deterministic output")
+}
+
+func TestBuilderIncludesCreatedAtWhenRequested(t *testing.T) {
+	b := NewBuilder()
+	b.SetIncludeTimestamps(true)
+	content := []byte("hello")
+	_, err := b.AddFile("test.txt", FileSize(len(content)), ModTime(time.Now()), bytes.NewReader(content), nil)
+	require.NoError(t, err)
+
+	var buf bytes.Buffer
+	require.NoError(t, b.Build(&buf))
+
+	m, err := NewManifestFromReader(&buf)
+	require.NoError(t, err)
+	assert.NotNil(t, m.pbInner.CreatedAt, "createdAt should be set when IncludeTimestamps is true")
+}
+
+func TestBuilderDeterministicFileOrder(t *testing.T) {
+	// Two builds with same files in different order should produce same file ordering.
+	// Note: UUIDs differ per build, so we compare parsed file lists, not raw bytes.
+	buildAndParse := func(order []string) []*MFFilePath {
+		b := NewBuilder()
+		for _, name := range order {
+			content := []byte("content of " + name)
+			_, err := b.AddFile(RelFilePath(name), FileSize(len(content)), ModTime(time.Unix(1000, 0)), bytes.NewReader(content), nil)
+			require.NoError(t, err)
+		}
+		var buf bytes.Buffer
+		require.NoError(t, b.Build(&buf))
+		m, err := NewManifestFromReader(&buf)
+		require.NoError(t, err)
+		return m.Files()
+	}
+
+	files1 := buildAndParse([]string{"b.txt", "a.txt"})
+	files2 := buildAndParse([]string{"a.txt", "b.txt"})
+
+	require.Len(t, files1, 2)
+	require.Len(t, files2, 2)
+	for i := range files1 {
+		assert.Equal(t, files1[i].Path, files2[i].Path)
+		assert.Equal(t, files1[i].Size, files2[i].Size)
+	}
+	assert.Equal(t, "a.txt", files1[0].Path)
+	assert.Equal(t, "b.txt", files1[1].Path)
+}

mfer/checker.go

@@ -70,6 +70,8 @@ type Checker struct {
 	fs       afero.Fs
 	// manifestPaths is a set of paths in the manifest for quick lookup
 	manifestPaths map[RelFilePath]struct{}
+	// manifestRelPath is the relative path of the manifest file from basePath (for exclusion)
+	manifestRelPath RelFilePath
 	// signature info from the manifest
 	signature     []byte
 	signer        []byte
@@ -100,14 +102,25 @@ func NewChecker(manifestPath string, basePath string, fs afero.Fs) (*Checker, er
 		manifestPaths[RelFilePath(f.Path)] = struct{}{}
 	}
 
+	// Compute manifest's relative path from basePath for exclusion in FindExtraFiles
+	absManifest, err := filepath.Abs(manifestPath)
+	if err != nil {
+		return nil, err
+	}
+	manifestRel, err := filepath.Rel(abs, absManifest)
+	if err != nil {
+		manifestRel = ""
+	}
+
 	return &Checker{
-		basePath:      AbsFilePath(abs),
-		files:         files,
-		fs:            fs,
-		manifestPaths: manifestPaths,
-		signature:     m.pbOuter.Signature,
-		signer:        m.pbOuter.Signer,
-		signingPubKey: m.pbOuter.SigningPubKey,
+		basePath:        AbsFilePath(abs),
+		files:           files,
+		fs:              fs,
+		manifestPaths:   manifestPaths,
+		manifestRelPath: RelFilePath(manifestRel),
+		signature:       m.pbOuter.Signature,
+		signer:          m.pbOuter.Signer,
+		signingPubKey:   m.pbOuter.SigningPubKey,
 	}, nil
 }
 
@@ -170,6 +183,7 @@ func (c *Checker) Check(ctx context.Context, results chan<- Result, progress cha
 	var failures FileCount
 
 	startTime := time.Now()
+	lastProgressTime := time.Now()
 
 	for _, entry := range c.files {
 		select {
@@ -188,29 +202,34 @@ func (c *Checker) Check(ctx context.Context, results chan<- Result, progress cha
 			results <- result
 		}
 
-		// Send progress with rate and ETA calculation
+		// Send progress at most once per second (rate-limited)
 		if progress != nil {
-			elapsed := time.Since(startTime)
-			var bytesPerSec float64
-			var eta time.Duration
+			now := time.Now()
+			isLast := checkedFiles == totalFiles
+			if isLast || now.Sub(lastProgressTime) >= time.Second {
+				elapsed := time.Since(startTime)
+				var bytesPerSec float64
+				var eta time.Duration
 
-			if elapsed > 0 && checkedBytes > 0 {
-				bytesPerSec = float64(checkedBytes) / elapsed.Seconds()
-				remainingBytes := totalBytes - checkedBytes
-				if bytesPerSec > 0 {
-					eta = time.Duration(float64(remainingBytes)/bytesPerSec) * time.Second
+				if elapsed > 0 && checkedBytes > 0 {
+					bytesPerSec = float64(checkedBytes) / elapsed.Seconds()
+					remainingBytes := totalBytes - checkedBytes
+					if bytesPerSec > 0 {
+						eta = time.Duration(float64(remainingBytes)/bytesPerSec) * time.Second
+					}
 				}
-			}
 
-			sendCheckStatus(progress, CheckStatus{
-				TotalFiles:   totalFiles,
-				CheckedFiles: checkedFiles,
-				TotalBytes:   totalBytes,
-				CheckedBytes: checkedBytes,
-				BytesPerSec:  bytesPerSec,
-				ETA:          eta,
-				Failures:     failures,
-			})
+				sendCheckStatus(progress, CheckStatus{
+					TotalFiles:   totalFiles,
+					CheckedFiles: checkedFiles,
+					TotalBytes:   totalBytes,
+					CheckedBytes: checkedBytes,
+					BytesPerSec:  bytesPerSec,
+					ETA:          eta,
+					Failures:     failures,
+				})
+				lastProgressTime = now
+			}
 		}
 	}
 
@@ -224,12 +243,7 @@ func (c *Checker) checkFile(entry *MFFilePath, checkedBytes *FileSize) Result {
 	// Check if file exists
 	info, err := c.fs.Stat(absPath)
 	if err != nil {
-		if errors.Is(err, afero.ErrFileNotFound) || errors.Is(err, errors.New("file does not exist")) {
-			return Result{Path: relPath, Status: StatusMissing, Message: "file not found"}
-		}
-		// Check for "file does not exist" style errors
-		exists, _ := afero.Exists(c.fs, absPath)
-		if !exists {
+		if errors.Is(err, os.ErrNotExist) || errors.Is(err, afero.ErrFileNotFound) {
 			return Result{Path: relPath, Status: StatusMissing, Message: "file not found"}
 		}
 		return Result{Path: relPath, Status: StatusError, Message: err.Error()}
@@ -277,12 +291,14 @@ func (c *Checker) checkFile(entry *MFFilePath, checkedBytes *FileSize) Result {
 
 // FindExtraFiles walks the filesystem and reports files not in the manifest.
 // Results are sent to the results channel. The channel is closed when done.
+// Hidden files/directories (starting with .) are skipped, as they are excluded
+// from manifests by default. The manifest file itself is also skipped.
 func (c *Checker) FindExtraFiles(ctx context.Context, results chan<- Result) error {
 	if results != nil {
 		defer close(results)
 	}
 
-	return afero.Walk(c.fs, string(c.basePath), func(path string, info os.FileInfo, err error) error {
+	return afero.Walk(c.fs, string(c.basePath), func(walkPath string, info os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
@@ -293,18 +309,32 @@ func (c *Checker) FindExtraFiles(ctx context.Context, results chan<- Result) err
 		default:
 		}
 
+		// Get relative path
+		rel, err := filepath.Rel(string(c.basePath), walkPath)
+		if err != nil {
+			return err
+		}
+
+		// Skip hidden files and directories (dotfiles)
+		if IsHiddenPath(filepath.ToSlash(rel)) {
+			if info.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
 		// Skip directories
 		if info.IsDir() {
 			return nil
 		}
 
-		// Get relative path
-		rel, err := filepath.Rel(string(c.basePath), path)
-		if err != nil {
-			return err
-		}
 		relPath := RelFilePath(rel)
 
+		// Skip the manifest file itself
+		if relPath == c.manifestRelPath {
+			return nil
+		}
+
 		// Check if path is in manifest
 		if _, exists := c.manifestPaths[relPath]; !exists {
 			if results != nil {

mfer/checker_test.go

@@ -3,6 +3,7 @@ package mfer
 import (
 	"bytes"
 	"context"
+	"fmt"
 	"testing"
 	"time"
 
@@ -305,6 +306,44 @@ func TestFindExtraFiles(t *testing.T) {
 	assert.Equal(t, "not in manifest", extras[0].Message)
 }
 
+func TestFindExtraFilesSkipsManifestAndDotfiles(t *testing.T) {
+	fs := afero.NewMemMapFs()
+	manifestFiles := map[string][]byte{
+		"file1.txt": []byte("in manifest"),
+	}
+	createTestManifest(t, fs, "/data/.index.mf", manifestFiles)
+	createFilesOnDisk(t, fs, "/data", map[string][]byte{
+		"file1.txt": []byte("in manifest"),
+	})
+	// Create dotfile and manifest that should be skipped
+	require.NoError(t, afero.WriteFile(fs, "/data/.hidden", []byte("hidden"), 0o644))
+	require.NoError(t, afero.WriteFile(fs, "/data/.config/settings", []byte("cfg"), 0o644))
+	// Create a real extra file
+	require.NoError(t, fs.MkdirAll("/data", 0o755))
+	require.NoError(t, afero.WriteFile(fs, "/data/extra.txt", []byte("extra"), 0o644))
+
+	chk, err := NewChecker("/data/.index.mf", "/data", fs)
+	require.NoError(t, err)
+
+	results := make(chan Result, 10)
+	err = chk.FindExtraFiles(context.Background(), results)
+	require.NoError(t, err)
+
+	var extras []Result
+	for r := range results {
+		extras = append(extras, r)
+	}
+
+	// Should only report extra.txt, not .hidden, .config/settings, or .index.mf
+	for _, e := range extras {
+		t.Logf("extra: %s", e.Path)
+	}
+	assert.Len(t, extras, 1)
+	if len(extras) > 0 {
+		assert.Equal(t, RelFilePath("extra.txt"), extras[0].Path)
+	}
+}
+
 func TestFindExtraFilesContextCancellation(t *testing.T) {
 	fs := afero.NewMemMapFs()
 	files := map[string][]byte{"file.txt": []byte("data")}
@@ -381,6 +420,94 @@ func TestCheckSubdirectories(t *testing.T) {
 	assert.Equal(t, 3, okCount)
 }
 
+func TestCheckMissingFileDetectedWithoutFallback(t *testing.T) {
+	// Regression test: errors.Is(err, errors.New("...")) never matches because
+	// errors.New creates a new value each time. The fix uses os.ErrNotExist instead.
+	fs := afero.NewMemMapFs()
+	files := map[string][]byte{
+		"exists.txt":  []byte("here"),
+		"missing.txt": []byte("not on disk"),
+	}
+	createTestManifest(t, fs, "/manifest.mf", files)
+	// Only create one file on disk
+	createFilesOnDisk(t, fs, "/data", map[string][]byte{
+		"exists.txt": []byte("here"),
+	})
+
+	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	require.NoError(t, err)
+
+	results := make(chan Result, 10)
+	err = chk.Check(context.Background(), results, nil)
+	require.NoError(t, err)
+
+	statusCounts := map[Status]int{}
+	for r := range results {
+		statusCounts[r.Status]++
+		if r.Status == StatusMissing {
+			assert.Equal(t, RelFilePath("missing.txt"), r.Path)
+		}
+	}
+	assert.Equal(t, 1, statusCounts[StatusOK], "one file should be OK")
+	assert.Equal(t, 1, statusCounts[StatusMissing], "one file should be MISSING")
+	assert.Equal(t, 0, statusCounts[StatusError], "no files should be ERROR")
+}
+
+func TestFindExtraFilesSkipsDotfiles(t *testing.T) {
+	// Regression test for #16: FindExtraFiles should not report dotfiles
+	// or the manifest file itself as extra files.
+	fs := afero.NewMemMapFs()
+	files := map[string][]byte{
+		"file1.txt": []byte("in manifest"),
+	}
+	createTestManifest(t, fs, "/data/.index.mf", files)
+	createFilesOnDisk(t, fs, "/data", files)
+
+	// Add dotfiles and manifest file on disk
+	require.NoError(t, afero.WriteFile(fs, "/data/.hidden", []byte("dotfile"), 0o644))
+	require.NoError(t, fs.MkdirAll("/data/.git", 0o755))
+	require.NoError(t, afero.WriteFile(fs, "/data/.git/config", []byte("git config"), 0o644))
+
+	chk, err := NewChecker("/data/.index.mf", "/data", fs)
+	require.NoError(t, err)
+
+	results := make(chan Result, 10)
+	err = chk.FindExtraFiles(context.Background(), results)
+	require.NoError(t, err)
+
+	var extras []Result
+	for r := range results {
+		extras = append(extras, r)
+	}
+
+	// Should report NO extra files — dotfiles and manifest should be skipped
+	assert.Empty(t, extras, "FindExtraFiles should not report dotfiles or manifest file as extra; got: %v", extras)
+}
+
+func TestFindExtraFilesSkipsManifestFile(t *testing.T) {
+	// The manifest file itself should never be reported as extra
+	fs := afero.NewMemMapFs()
+	files := map[string][]byte{
+		"file1.txt": []byte("content"),
+	}
+	createTestManifest(t, fs, "/data/index.mf", files)
+	createFilesOnDisk(t, fs, "/data", files)
+
+	chk, err := NewChecker("/data/index.mf", "/data", fs)
+	require.NoError(t, err)
+
+	results := make(chan Result, 10)
+	err = chk.FindExtraFiles(context.Background(), results)
+	require.NoError(t, err)
+
+	var extras []Result
+	for r := range results {
+		extras = append(extras, r)
+	}
+
+	assert.Empty(t, extras, "manifest file should not be reported as extra; got: %v", extras)
+}
+
 func TestCheckEmptyManifest(t *testing.T) {
 	fs := afero.NewMemMapFs()
 	// Create manifest with no files
@@ -402,3 +529,40 @@ func TestCheckEmptyManifest(t *testing.T) {
 	}
 	assert.Equal(t, 0, count)
 }
+
+func TestCheckProgressRateLimited(t *testing.T) {
+	// Create many small files - progress should be rate-limited, not one per file.
+	// With rate-limiting to once per second, we should get far fewer progress
+	// updates than files (plus one final update).
+	fs := afero.NewMemMapFs()
+	files := make(map[string][]byte, 100)
+	for i := 0; i < 100; i++ {
+		name := fmt.Sprintf("file%03d.txt", i)
+		files[name] = []byte("content")
+	}
+	createTestManifest(t, fs, "/manifest.mf", files)
+	createFilesOnDisk(t, fs, "/data", files)
+
+	chk, err := NewChecker("/manifest.mf", "/data", fs)
+	require.NoError(t, err)
+
+	results := make(chan Result, 200)
+	progress := make(chan CheckStatus, 200)
+	err = chk.Check(context.Background(), results, progress)
+	require.NoError(t, err)
+
+	// Drain results
+	for range results {
+	}
+
+	// Count progress updates
+	var progressCount int
+	for range progress {
+		progressCount++
+	}
+
+	// Should be far fewer than 100 (rate-limited to once per second)
+	// At minimum we get the final update
+	assert.GreaterOrEqual(t, progressCount, 1, "should get at least the final progress update")
+	assert.Less(t, progressCount, 100, "progress should be rate-limited, not one per file")
+}

mfer/constants.go

@@ -3,4 +3,9 @@ package mfer
 const (
 	Version     = "0.1.0"
 	ReleaseDate = "2025-12-17"
+
+	// MaxDecompressedSize is the maximum allowed size of decompressed manifest
+	// data (256 MB). This prevents decompression bombs from consuming excessive
+	// memory.
+	MaxDecompressedSize int64 = 256 * 1024 * 1024
 )

mfer/deserialize.go

@@ -44,7 +44,7 @@ func (m *manifest) deserializeInner() error {
 	// Verify hash of compressed data before decompression
 	h := sha256.New()
 	if _, err := h.Write(m.pbOuter.InnerMessage); err != nil {
-		return err
+		return fmt.Errorf("deserialize: hash write: %w", err)
 	}
 	sha256Hash := h.Sum(nil)
 	if !bytes.Equal(sha256Hash, m.pbOuter.Sha256) {
@@ -72,13 +72,23 @@ func (m *manifest) deserializeInner() error {
 
 	zr, err := zstd.NewReader(bb)
 	if err != nil {
-		return err
+		return fmt.Errorf("deserialize: zstd reader: %w", err)
 	}
 	defer zr.Close()
 
-	dat, err := io.ReadAll(zr)
+	// Limit decompressed size to prevent decompression bombs.
+	// Use declared size + 1 byte to detect overflow, capped at MaxDecompressedSize.
+	maxSize := MaxDecompressedSize
+	if m.pbOuter.Size > 0 && m.pbOuter.Size < int64(maxSize) {
+		maxSize = int64(m.pbOuter.Size) + 1
+	}
+	limitedReader := io.LimitReader(zr, maxSize)
+	dat, err := io.ReadAll(limitedReader)
 	if err != nil {
-		return err
+		return fmt.Errorf("deserialize: decompress: %w", err)
+	}
+	if int64(len(dat)) >= MaxDecompressedSize {
+		return fmt.Errorf("decompressed data exceeds maximum allowed size of %d bytes", MaxDecompressedSize)
 	}
 
 	isize := len(dat)
@@ -90,7 +100,7 @@ func (m *manifest) deserializeInner() error {
 	// Deserialize inner message
 	m.pbInner = new(MFFile)
 	if err := proto.Unmarshal(dat, m.pbInner); err != nil {
-		return err
+		return fmt.Errorf("deserialize: unmarshal inner: %w", err)
 	}
 
 	// Validate inner UUID

mfer/gpg.go

@@ -20,7 +20,7 @@ type SigningOptions struct {
 // gpgSign creates a detached signature of the data using the specified key.
 // Returns the armored detached signature.
 func gpgSign(data []byte, keyID GPGKeyID) ([]byte, error) {
-	cmd := exec.Command("gpg",
+	cmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--detach-sign",
 		"--armor",
 		"--local-user", string(keyID),
@@ -42,7 +42,7 @@ func gpgSign(data []byte, keyID GPGKeyID) ([]byte, error) {
 // gpgExportPublicKey exports the public key for the specified key ID.
 // Returns the armored public key.
 func gpgExportPublicKey(keyID GPGKeyID) ([]byte, error) {
-	cmd := exec.Command("gpg",
+	cmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--export",
 		"--armor",
 		string(keyID),
@@ -65,7 +65,7 @@ func gpgExportPublicKey(keyID GPGKeyID) ([]byte, error) {
 
 // gpgGetKeyFingerprint gets the full fingerprint for a key ID.
 func gpgGetKeyFingerprint(keyID GPGKeyID) ([]byte, error) {
-	cmd := exec.Command("gpg",
+	cmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--with-colons",
 		"--fingerprint",
 		string(keyID),
@@ -100,7 +100,7 @@ func gpgExtractPubKeyFingerprint(pubKey []byte) (string, error) {
 	if err != nil {
 		return "", fmt.Errorf("failed to create temp dir: %w", err)
 	}
-	defer os.RemoveAll(tmpDir)
+	defer func() { _ = os.RemoveAll(tmpDir) }()
 
 	// Set restrictive permissions
 	if err := os.Chmod(tmpDir, 0o700); err != nil {
@@ -114,7 +114,7 @@ func gpgExtractPubKeyFingerprint(pubKey []byte) (string, error) {
 	}
 
 	// Import the public key into the temporary keyring
-	importCmd := exec.Command("gpg",
+	importCmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--homedir", tmpDir,
 		"--import",
 		pubKeyFile,
@@ -126,7 +126,7 @@ func gpgExtractPubKeyFingerprint(pubKey []byte) (string, error) {
 	}
 
 	// List keys to get fingerprint
-	listCmd := exec.Command("gpg",
+	listCmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--homedir", tmpDir,
 		"--with-colons",
 		"--fingerprint",
@@ -158,7 +158,7 @@ func gpgVerify(data, signature, pubKey []byte) error {
 	if err != nil {
 		return fmt.Errorf("failed to create temp dir: %w", err)
 	}
-	defer os.RemoveAll(tmpDir)
+	defer func() { _ = os.RemoveAll(tmpDir) }()
 
 	// Set restrictive permissions
 	if err := os.Chmod(tmpDir, 0o700); err != nil {
@@ -184,7 +184,7 @@ func gpgVerify(data, signature, pubKey []byte) error {
 	}
 
 	// Import the public key into the temporary keyring
-	importCmd := exec.Command("gpg",
+	importCmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--homedir", tmpDir,
 		"--import",
 		pubKeyFile,
@@ -196,7 +196,7 @@ func gpgVerify(data, signature, pubKey []byte) error {
 	}
 
 	// Verify the signature
-	verifyCmd := exec.Command("gpg",
+	verifyCmd := exec.Command("gpg", "--batch", "--no-tty",
 		"--homedir", tmpDir,
 		"--verify",
 		sigFile,

mfer/gpg_test.go

@@ -34,15 +34,15 @@ func testGPGEnv(t *testing.T) (GPGKeyID, func()) {
 
 	// Save original GNUPGHOME and set new one
 	origGPGHome := os.Getenv("GNUPGHOME")
-	os.Setenv("GNUPGHOME", gpgHome)
+	require.NoError(t, os.Setenv("GNUPGHOME", gpgHome))
 
 	cleanup := func() {
 		if origGPGHome == "" {
-			os.Unsetenv("GNUPGHOME")
+			_ = os.Unsetenv("GNUPGHOME")
 		} else {
-			os.Setenv("GNUPGHOME", origGPGHome)
+			_ = os.Setenv("GNUPGHOME", origGPGHome)
 		}
-		os.RemoveAll(gpgHome)
+		_ = os.RemoveAll(gpgHome)
 	}
 
 	// Generate a test key with no passphrase

mfer/manifest.go

@@ -17,6 +17,7 @@ type manifest struct {
 	pbOuter        *MFFileOuter
 	output         *bytes.Buffer
 	signingOptions *SigningOptions
+	fixedUUID      []byte // if set, use this UUID instead of generating one
 }
 
 func (m *manifest) String() string {

mfer/mf.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
 // 	protoc-gen-go v1.36.11
-// 	protoc        v6.33.0
+// 	protoc        v6.33.4
 // source: mf.proto
 
 package mfer
@@ -329,6 +329,9 @@ func (x *MFFileOuter) GetSigningPubKey() []byte {
 type MFFilePath struct {
 	state protoimpl.MessageState `protogen:"open.v1"`
 	// required attributes:
+	// Path invariants: must be valid UTF-8, use forward slashes only,
+	// be relative (no leading /), contain no ".." segments, and no
+	// empty segments (no "//").
 	Path string `protobuf:"bytes,1,opt,name=path,proto3" json:"path,omitempty"`
 	Size int64  `protobuf:"varint,2,opt,name=size,proto3" json:"size,omitempty"`
 	// gotta have at least one:
@@ -337,7 +340,6 @@ type MFFilePath struct {
 	MimeType      *string    `protobuf:"bytes,301,opt,name=mimeType,proto3,oneof" json:"mimeType,omitempty"`
 	Mtime         *Timestamp `protobuf:"bytes,302,opt,name=mtime,proto3,oneof" json:"mtime,omitempty"`
 	Ctime         *Timestamp `protobuf:"bytes,303,opt,name=ctime,proto3,oneof" json:"ctime,omitempty"`
-	Atime         *Timestamp `protobuf:"bytes,304,opt,name=atime,proto3,oneof" json:"atime,omitempty"`
 	unknownFields protoimpl.UnknownFields
 	sizeCache     protoimpl.SizeCache
 }
@@ -414,13 +416,6 @@ func (x *MFFilePath) GetCtime() *Timestamp {
 	return nil
 }
 
-func (x *MFFilePath) GetAtime() *Timestamp {
-	if x != nil {
-		return x.Atime
-	}
-	return nil
-}
-
 type MFFileChecksum struct {
 	state protoimpl.MessageState `protogen:"open.v1"`
 	// 1.0 golang implementation must write a multihash here
@@ -566,7 +561,7 @@ const file_mf_proto_rawDesc = "" +
 	"\n" +
 	"_signatureB\t\n" +
 	"\a_signerB\x10\n" +
-	"\x0e_signingPubKey\"\xa2\x02\n" +
+	"\x0e_signingPubKey\"\xf0\x01\n" +
 	"\n" +
 	"MFFilePath\x12\x12\n" +
 	"\x04path\x18\x01 \x01(\tR\x04path\x12\x12\n" +
@@ -576,13 +571,10 @@ const file_mf_proto_rawDesc = "" +
 	"\x05mtime\x18\xae\x02 \x01(\v2\n" +
 	".TimestampH\x01R\x05mtime\x88\x01\x01\x12&\n" +
 	"\x05ctime\x18\xaf\x02 \x01(\v2\n" +
-	".TimestampH\x02R\x05ctime\x88\x01\x01\x12&\n" +
-	"\x05atime\x18\xb0\x02 \x01(\v2\n" +
-	".TimestampH\x03R\x05atime\x88\x01\x01B\v\n" +
+	".TimestampH\x02R\x05ctime\x88\x01\x01B\v\n" +
 	"\t_mimeTypeB\b\n" +
 	"\x06_mtimeB\b\n" +
-	"\x06_ctimeB\b\n" +
-	"\x06_atime\".\n" +
+	"\x06_ctime\".\n" +
 	"\x0eMFFileChecksum\x12\x1c\n" +
 	"\tmultiHash\x18\x01 \x01(\fR\tmultiHash\"\xd6\x01\n" +
 	"\x06MFFile\x12)\n" +
@@ -627,15 +619,14 @@ var file_mf_proto_depIdxs = []int32{
 	6, // 2: MFFilePath.hashes:type_name -> MFFileChecksum
 	3, // 3: MFFilePath.mtime:type_name -> Timestamp
 	3, // 4: MFFilePath.ctime:type_name -> Timestamp
-	3, // 5: MFFilePath.atime:type_name -> Timestamp
-	2, // 6: MFFile.version:type_name -> MFFile.Version
-	5, // 7: MFFile.files:type_name -> MFFilePath
-	3, // 8: MFFile.createdAt:type_name -> Timestamp
-	9, // [9:9] is the sub-list for method output_type
-	9, // [9:9] is the sub-list for method input_type
-	9, // [9:9] is the sub-list for extension type_name
-	9, // [9:9] is the sub-list for extension extendee
-	0, // [0:9] is the sub-list for field type_name
+	2, // 5: MFFile.version:type_name -> MFFile.Version
+	5, // 6: MFFile.files:type_name -> MFFilePath
+	3, // 7: MFFile.createdAt:type_name -> Timestamp
+	8, // [8:8] is the sub-list for method output_type
+	8, // [8:8] is the sub-list for method input_type
+	8, // [8:8] is the sub-list for extension type_name
+	8, // [8:8] is the sub-list for extension extendee
+	0, // [0:8] is the sub-list for field type_name
 }
 
 func init() { file_mf_proto_init() }

mfer/mf.proto

@@ -46,6 +46,9 @@ message MFFileOuter {
 
 message MFFilePath {
     // required attributes:
+    // Path invariants: must be valid UTF-8, use forward slashes only,
+    // be relative (no leading /), contain no ".." segments, and no
+    // empty segments (no "//").
     string path = 1;
     int64 size = 2;
 
@@ -56,7 +59,6 @@ message MFFilePath {
     optional string mimeType = 301;
     optional Timestamp mtime = 302;
     optional Timestamp ctime = 303;
-    optional Timestamp atime = 304;
 }
 
 message MFFileChecksum {

mfer/scanner.go

@@ -43,10 +43,12 @@ type ScanStatus struct {
 
 // ScannerOptions configures scanner behavior.
 type ScannerOptions struct {
-	IncludeDotfiles bool            // Include files and directories starting with a dot (default: exclude)
-	FollowSymLinks  bool            // Resolve symlinks instead of skipping them
-	Fs              afero.Fs        // Filesystem to use, defaults to OsFs if nil
-	SigningOptions  *SigningOptions // GPG signing options (nil = no signing)
+	IncludeDotfiles   bool            // Include files and directories starting with a dot (default: exclude)
+	FollowSymLinks    bool            // Resolve symlinks instead of skipping them
+	IncludeTimestamps bool            // Include createdAt timestamp in manifest (default: omit for determinism)
+	Fs                afero.Fs        // Filesystem to use, defaults to OsFs if nil
+	SigningOptions    *SigningOptions // GPG signing options (nil = no signing)
+	Seed              string          // If set, derive a deterministic UUID from this seed
 }
 
 // FileEntry represents a file that has been enumerated.
@@ -273,9 +275,15 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 	s.mu.RUnlock()
 
 	builder := NewBuilder()
+	if s.options.IncludeTimestamps {
+		builder.SetIncludeTimestamps(true)
+	}
 	if s.options.SigningOptions != nil {
 		builder.SetSigningOptions(s.options.SigningOptions)
 	}
+	if s.options.Seed != "" {
+		builder.SetSeed(s.options.Seed)
+	}
 
 	var scannedFiles FileCount
 	var scannedBytes FileSize
@@ -385,6 +393,9 @@ func (s *Scanner) ToManifest(ctx context.Context, w io.Writer, progress chan<- S
 // The path should use forward slashes.
 func IsHiddenPath(p string) bool {
 	tp := path.Clean(p)
+	if tp == "." || tp == "/" {
+		return false
+	}
 	if strings.HasPrefix(tp, ".") {
 		return true
 	}

mfer/scanner_test.go

@@ -352,6 +352,10 @@ func TestIsHiddenPath(t *testing.T) {
 		{"/absolute/.hidden", true},
 		{"./relative", false}, // path.Clean removes leading ./
 		{"a/b/c/.d/e", true},
+		{".", false},          // current directory is not hidden (#14)
+		{"/", false},          // root is not hidden
+		{"./", false},         // current directory with trailing slash
+		{"./file.txt", false}, // file in current directory
 	}
 
 	for _, tt := range tests {

mfer/serialize.go

@@ -16,11 +16,10 @@ import (
 const MAGIC string = "ZNAVSRFG"
 
 func newTimestampFromTime(t time.Time) *Timestamp {
-	out := &Timestamp{
+	return &Timestamp{
 		Seconds: t.Unix(),
-		Nanos:   int32(t.UnixNano() - (t.Unix() * 1000000000)),
+		Nanos:   int32(t.Nanosecond()),
 	}
-	return out
 }
 
 func (m *manifest) generate() error {
@@ -35,12 +34,12 @@ func (m *manifest) generate() error {
 	}
 	dat, err := proto.MarshalOptions{Deterministic: true}.Marshal(m.pbOuter)
 	if err != nil {
-		return err
+		return fmt.Errorf("serialize: marshal outer: %w", err)
 	}
 	m.output = bytes.NewBuffer([]byte(MAGIC))
 	_, err = m.output.Write(dat)
 	if err != nil {
-		return err
+		return fmt.Errorf("serialize: write output: %w", err)
 	}
 	return nil
 }
@@ -50,24 +49,29 @@ func (m *manifest) generateOuter() error {
 		return errors.New("internal error")
 	}
 
-	// Generate UUID and set on inner message
-	manifestUUID := uuid.New()
+	// Use fixed UUID if provided, otherwise generate a new one
+	var manifestUUID uuid.UUID
+	if len(m.fixedUUID) == 16 {
+		copy(manifestUUID[:], m.fixedUUID)
+	} else {
+		manifestUUID = uuid.New()
+	}
 	m.pbInner.Uuid = manifestUUID[:]
 
 	innerData, err := proto.MarshalOptions{Deterministic: true}.Marshal(m.pbInner)
 	if err != nil {
-		return err
+		return fmt.Errorf("serialize: marshal inner: %w", err)
 	}
 
 	// Compress the inner data
 	idc := new(bytes.Buffer)
 	zw, err := zstd.NewWriter(idc, zstd.WithEncoderLevel(zstd.SpeedBestCompression))
 	if err != nil {
-		return err
+		return fmt.Errorf("serialize: create compressor: %w", err)
 	}
 	_, err = zw.Write(innerData)
 	if err != nil {
-		return err
+		return fmt.Errorf("serialize: compress: %w", err)
 	}
 	_ = zw.Close()
 
@@ -76,7 +80,7 @@ func (m *manifest) generateOuter() error {
 	// Hash the compressed data for integrity verification before decompression
 	h := sha256.New()
 	if _, err := h.Write(compressedData); err != nil {
-		return err
+		return fmt.Errorf("serialize: hash write: %w", err)
 	}
 	sha256Hash := h.Sum(nil)
 

mfer/url.go

@@ -27,8 +27,12 @@ func (b BaseURL) JoinPath(path RelFilePath) (FileURL, error) {
 		base.Path += "/"
 	}
 
-	// Parse and encode the relative path
-	ref, err := url.Parse(url.PathEscape(string(path)))
+	// Encode each path segment individually to preserve slashes
+	segments := strings.Split(string(path), "/")
+	for i, seg := range segments {
+		segments[i] = url.PathEscape(seg)
+	}
+	ref, err := url.Parse(strings.Join(segments, "/"))
 	if err != nil {
 		return "", err
 	}

mfer/url_test.go

@@ -0,0 +1,44 @@
+package mfer
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBaseURLJoinPath(t *testing.T) {
+	tests := []struct {
+		base     BaseURL
+		path     RelFilePath
+		expected string
+	}{
+		{"https://example.com/dir/", "file.txt", "https://example.com/dir/file.txt"},
+		{"https://example.com/dir", "file.txt", "https://example.com/dir/file.txt"},
+		{"https://example.com/", "sub/file.txt", "https://example.com/sub/file.txt"},
+		{"https://example.com/dir/", "file with spaces.txt", "https://example.com/dir/file%20with%20spaces.txt"},
+	}
+
+	for _, tt := range tests {
+		t.Run(string(tt.base)+"+"+string(tt.path), func(t *testing.T) {
+			result, err := tt.base.JoinPath(tt.path)
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, string(result))
+		})
+	}
+}
+
+func TestBaseURLString(t *testing.T) {
+	b := BaseURL("https://example.com/")
+	assert.Equal(t, "https://example.com/", b.String())
+}
+
+func TestFileURLString(t *testing.T) {
+	f := FileURL("https://example.com/file.txt")
+	assert.Equal(t, "https://example.com/file.txt", f.String())
+}
+
+func TestManifestURLString(t *testing.T) {
+	m := ManifestURL("https://example.com/index.mf")
+	assert.Equal(t, "https://example.com/index.mf", m.String())
+}