feat: add replace subcommand with multi-pattern support

AGENTS.md

@@ -3,29 +3,41 @@
 Auto-generated from all feature plans. Last updated: 2025-10-29
 
 ## Active Technologies
-
+- Local filesystem (no persistent database) (002-add-replace-command)
 - Go 1.24 + `spf13/cobra`, `spf13/pflag` (001-list-command-filters)
 
 ## Project Structure
 
 ```text
-src/
+cmd/
+internal/
+scripts/
 tests/
 ```
 
 ## Commands
 
 - `renamer list` — preview rename scope with shared flags before executing changes.
-- Persistent scope flags: `--path`, `-r/--recursive`, `-d/--include-dirs`, `--hidden`, `--extensions`.
+- `renamer replace` — consolidate multiple literal patterns into a single replacement (supports `--dry-run` + `--yes`).
+- `renamer undo` — revert the most recent rename/replace batch using ledger entries.
+- Persistent scope flags: `--path`, `-r/--recursive`, `-d/--include-dirs`, `--hidden`, `--extensions`, `--yes`, `--dry-run`.
 
 ## Code Style
 
-Go 1.24: Follow standard conventions
+- Go 1.24: follow gofmt (already checked in CI)
+- Prefer composable packages under `internal/` for reusable logic
+- Keep CLI wiring thin; place business logic in services
+
+## Testing
+
+- `go test ./...`
+- Contract tests: `tests/contract/replace_command_test.go`
+- Integration tests: `tests/integration/replace_flow_test.go`
+- Smoke: `scripts/smoke-test-replace.sh`
 
 ## Recent Changes
-
+- 002-add-replace-command: Added `renamer replace` command, ledger metadata, and automation docs.
-- 001-list-command-filters: Added Go 1.24 + `spf13/cobra`, `spf13/pflag`
+- 001-list-command-filters: Added `renamer list` command with shared scope flags and formatters.
-- 001-list-command-filters: Introduced `renamer list` command with shared scope flags and formatters
 
 <!-- MANUAL ADDITIONS START -->
 <!-- MANUAL ADDITIONS END -->

cmd/replace.go

@@ -0,0 +1,119 @@
+package cmd
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/spf13/cobra"
+
+	"github.com/rogeecn/renamer/internal/listing"
+	"github.com/rogeecn/renamer/internal/replace"
+)
+
+// NewReplaceCommand constructs the replace CLI command; exported for testing.
+func NewReplaceCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "replace <pattern1> [pattern2 ...] <replacement>",
+		Short: "Replace multiple literals in file and directory names",
+		Args:  cobra.MinimumNArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			parseResult, err := replace.ParseArgs(args)
+			if err != nil {
+				return err
+			}
+
+			scope, err := listing.ScopeFromCmd(cmd)
+			if err != nil {
+				return err
+			}
+
+			req := &replace.ReplaceRequest{
+				WorkingDir:         scope.WorkingDir,
+				Patterns:           parseResult.Patterns,
+				Replacement:        parseResult.Replacement,
+				IncludeDirectories: scope.IncludeDirectories,
+				Recursive:          scope.Recursive,
+				IncludeHidden:      scope.IncludeHidden,
+				Extensions:         scope.Extensions,
+			}
+
+			dryRun, err := getBool(cmd, "dry-run")
+			if err != nil {
+				return err
+			}
+			autoApply, err := getBool(cmd, "yes")
+			if err != nil {
+				return err
+			}
+
+			if dryRun && autoApply {
+				return errors.New("--dry-run cannot be combined with --yes; remove one of them")
+			}
+
+			out := cmd.OutOrStdout()
+			summary, planned, err := replace.Preview(cmd.Context(), req, parseResult, out)
+			if err != nil {
+				return err
+			}
+
+			for _, dup := range summary.SortedDuplicates() {
+				fmt.Fprintf(out, "Warning: pattern %q provided multiple times\n", dup)
+			}
+
+			if len(summary.Conflicts) > 0 {
+				for _, conflict := range summary.Conflicts {
+					fmt.Fprintf(out, "CONFLICT: %s -> %s (%s)\n", conflict.OriginalPath, conflict.ProposedPath, conflict.Reason)
+				}
+				return errors.New("conflicts detected; aborting")
+			}
+
+			if summary.ChangedCount == 0 {
+				fmt.Fprintln(out, "No replacements required")
+				return nil
+			}
+
+			fmt.Fprintf(out, "Planned replacements: %d entries updated across %d candidates\n", summary.ChangedCount, summary.TotalCandidates)
+			for pattern, count := range summary.PatternMatches {
+				fmt.Fprintf(out, "  %s -> %d occurrences\n", pattern, count)
+			}
+
+			if dryRun || !autoApply {
+				fmt.Fprintln(out, "Preview complete. Re-run with --yes to apply.")
+				return nil
+			}
+
+			entry, err := replace.Apply(context.Background(), req, planned, summary)
+			if err != nil {
+				return err
+			}
+
+			if len(entry.Operations) == 0 {
+				fmt.Fprintln(out, "Nothing to apply; preview already up to date.")
+				return nil
+			}
+
+			fmt.Fprintf(out, "Applied %d replacements. Ledger updated.\n", len(entry.Operations))
+			return nil
+		},
+	}
+
+	cmd.Example = `  renamer replace draft Draft final --dry-run
+  renamer replace "Project X" "Project-X" ProjectX --yes --path ./docs`
+
+	return cmd
+}
+
+func getBool(cmd *cobra.Command, name string) (bool, error) {
+	if flag := cmd.Flags().Lookup(name); flag != nil {
+		return cmd.Flags().GetBool(name)
+	}
+	if flag := cmd.InheritedFlags().Lookup(name); flag != nil {
+		return cmd.InheritedFlags().GetBool(name)
+	}
+	return false, fmt.Errorf("flag %s not defined", name)
+}
+
+func init() {
+	rootCmd.AddCommand(NewReplaceCommand())
+}

cmd/root.go

@@ -29,5 +29,24 @@ func Execute() {
 }
 
 func init() {
+	// Register persistent flags shared by all subcommands (`list`, `replace`, etc.).
+	// These scope flags remain centralized so new commands automatically inherit
+	// traversal behavior without duplicating flag definitions.
 	listing.RegisterScopeFlags(rootCmd.PersistentFlags())
 }
+
+// NewRootCommand creates a fresh root command with all subcommands and flags registered.
+func NewRootCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "renamer",
+		Short: "Safe, scriptable batch renaming utility",
+		Long:  rootCmd.Long,
+	}
+
+	listing.RegisterScopeFlags(cmd.PersistentFlags())
+	cmd.AddCommand(newListCommand())
+	cmd.AddCommand(NewReplaceCommand())
+	cmd.AddCommand(newUndoCommand())
+
+	return cmd
+}

cmd/undo.go

@@ -0,0 +1,52 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+
+	"github.com/rogeecn/renamer/internal/history"
+)
+
+func newUndoCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "undo",
+		Short: "Undo the most recent rename or replace batch",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			workingDir, err := resolveWorkingDir(cmd)
+			if err != nil {
+				return err
+			}
+
+			entry, err := history.Undo(workingDir)
+			if err != nil {
+				return err
+			}
+
+			fmt.Fprintf(cmd.OutOrStdout(), "Undo applied: %d operations reversed\n", len(entry.Operations))
+			return nil
+		},
+	}
+
+	return cmd
+}
+
+func resolveWorkingDir(cmd *cobra.Command) (string, error) {
+	if flag := cmd.Flags().Lookup("path"); flag != nil {
+		if value := flag.Value.String(); value != "" {
+			return filepath.Abs(value)
+		}
+	}
+	if flag := cmd.InheritedFlags().Lookup("path"); flag != nil {
+		if value := flag.Value.String(); value != "" {
+			return filepath.Abs(value)
+		}
+	}
+	return os.Getwd()
+}
+
+func init() {
+	rootCmd.AddCommand(newUndoCommand())
+}

docs/CHANGELOG.md

@@ -2,5 +2,7 @@
 
 ## Unreleased
 
+- Add `renamer replace` subcommand supporting multi-pattern replacements, preview/apply/undo, and scope flags.
+- Document quoting guidance, `--dry-run` / `--yes` behavior, and automation scenarios for replace command.
 - Add `renamer list` subcommand with shared scope flags and plain/table output formats.
 - Document global scope flags and hidden-file behavior.

docs/cli-flags.md

@@ -1,15 +1,18 @@
 # CLI Scope Flags
 
 Renamer shares a consistent set of scope flags across every command that inspects or mutates the
-filesystem. Use these options at the root command level so they apply to `list`, `preview`, and
+filesystem. Use these options at the root command level so they apply to all subcommands (`list`,
-`rename` alike.
+`replace`, future `preview`/`rename`, etc.).
 
 | Flag | Default | Description |
 |------|---------|-------------|
+| `--path` | `.` | Working directory root for traversal. |
 | `-r`, `--recursive` | `false` | Traverse subdirectories depth-first. Symlinked directories are not followed. |
 | `-d`, `--include-dirs` | `false` | Limit results to directories only (files and symlinks are suppressed). Directory traversal still occurs even when the flag is absent. |
 | `-e`, `--extensions` | *(none)* | Pipe-separated list of file extensions (e.g. `.jpg|.mov`). Tokens must start with a dot, are lowercased internally, and duplicates are ignored. |
 | `--hidden` | `false` | Include dot-prefixed files and directories. By default they are excluded from listings and rename previews. |
+| `--yes` | `false` | Apply changes without an interactive confirmation prompt (mutating commands only). |
+| `--dry-run` | `false` | Force preview-only behavior even when `--yes` is supplied. |
 | `--format` | `table` | Command-specific output formatting option. For `list`, use `table` or `plain`. |
 
 ## Validation Rules
@@ -22,8 +25,26 @@ filesystem. Use these options at the root command level so they apply to `list`,
 Keep this document updated whenever a new command is introduced or the global scope behavior
 changes.
 
+## Replace Command Quick Reference
+
+```bash
+renamer replace <pattern1> [pattern2 ...] <replacement> [flags]
+```
+
+- The **final positional argument** is the replacement value; all preceding arguments are treated as
+  literal patterns (quotes required when a pattern contains spaces).
+- Patterns are applied sequentially and replaced with the same value. Duplicate patterns are
+  deduplicated automatically and surfaced in the preview summary.
+- Empty replacement strings are allowed (effectively deleting each pattern) but the preview warns
+  before confirmation.
+- Combine with scope flags (`--path`, `-r`, `--include-dirs`, etc.) to target the desired set of
+  files/directories.
+- Use `--dry-run` to preview in scripts, then `--yes` to apply once satisfied; combining both flags
+  exits with an error to prevent accidental automation mistakes.
+
 ### Usage Examples
 
 - Preview files recursively: `renamer --recursive preview`
 - List JPEGs only: `renamer --extensions .jpg list`
+- Replace multiple patterns: `renamer replace draft Draft final --dry-run`
 - Include dotfiles: `renamer --hidden --extensions .env list`

internal/history/history.go

@@ -0,0 +1,122 @@
+package history
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const ledgerFileName = ".renamer"
+
+// Operation records a single rename from source to target.
+type Operation struct {
+	From string `json:"from"`
+	To   string `json:"to"`
+}
+
+// Entry represents a batch of operations appended to the ledger.
+type Entry struct {
+	Timestamp  time.Time      `json:"timestamp"`
+	Command    string         `json:"command"`
+	WorkingDir string         `json:"workingDir"`
+	Operations []Operation    `json:"operations"`
+	Metadata   map[string]any `json:"metadata,omitempty"`
+}
+
+// Append writes a new entry to the ledger in newline-delimited JSON format.
+func Append(workingDir string, entry Entry) error {
+	entry.Timestamp = time.Now().UTC()
+	entry.WorkingDir = workingDir
+
+	path := ledgerPath(workingDir)
+
+	file, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	enc := json.NewEncoder(file)
+	return enc.Encode(entry)
+}
+
+// Undo reverts the most recent ledger entry and removes it from the ledger file.
+func Undo(workingDir string) (Entry, error) {
+	path := ledgerPath(workingDir)
+
+	file, err := os.Open(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return Entry{}, errors.New("no ledger entries available")
+	} else if err != nil {
+		return Entry{}, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	entries := make([]Entry, 0)
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		if len(line) == 0 {
+			continue
+		}
+		var e Entry
+		if err := json.Unmarshal(append([]byte(nil), line...), &e); err != nil {
+			return Entry{}, err
+		}
+		entries = append(entries, e)
+	}
+	if err := scanner.Err(); err != nil {
+		return Entry{}, err
+	}
+	if len(entries) == 0 {
+		return Entry{}, errors.New("no ledger entries available")
+	}
+
+	last := entries[len(entries)-1]
+
+	// Revert operations in reverse order.
+	for i := len(last.Operations) - 1; i >= 0; i-- {
+		op := last.Operations[i]
+		source := filepath.Join(workingDir, op.To)
+		destination := filepath.Join(workingDir, op.From)
+		if err := os.Rename(source, destination); err != nil {
+			return Entry{}, err
+		}
+	}
+
+	// Rewrite ledger without the last entry.
+	if len(entries) == 1 {
+		if err := os.Remove(path); err != nil && !errors.Is(err, os.ErrNotExist) {
+			return Entry{}, err
+		}
+	} else {
+		tmp := path + ".tmp"
+		output, err := os.OpenFile(tmp, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0o644)
+		if err != nil {
+			return Entry{}, err
+		}
+		enc := json.NewEncoder(output)
+		for _, e := range entries[:len(entries)-1] {
+			if err := enc.Encode(e); err != nil {
+				output.Close()
+				return Entry{}, err
+			}
+		}
+		if err := output.Close(); err != nil {
+			return Entry{}, err
+		}
+		if err := os.Rename(tmp, path); err != nil {
+			return Entry{}, err
+		}
+	}
+
+	return last, nil
+}
+
+// ledgerPath returns the absolute path to the ledger file under workingDir.
+func ledgerPath(workingDir string) string {
+	return filepath.Join(workingDir, ledgerFileName)
+}

internal/listing/options.go

@@ -15,6 +15,8 @@ const (
 	flagIncludeDirs = "include-dirs"
 	flagHidden      = "hidden"
 	flagExtensions  = "extensions"
+	flagYes         = "yes"
+	flagDryRun      = "dry-run"
 )
 
 // RegisterScopeFlags defines persistent flags that scope listing, preview, and rename operations.
@@ -24,6 +26,8 @@ func RegisterScopeFlags(flags *pflag.FlagSet) {
 	flags.BoolP(flagIncludeDirs, "d", false, "Include directories in results")
 	flags.Bool(flagHidden, false, "Include hidden files and directories")
 	flags.StringP(flagExtensions, "e", "", "Pipe-delimited list of extensions to include (e.g. .jpg|.png)")
+	flags.Bool(flagYes, false, "Apply changes without interactive confirmation (mutating commands)")
+	flags.Bool(flagDryRun, false, "Force preview-only output without applying changes")
 }
 
 // ScopeFromCmd builds a ListingRequest populated from scope flags on the provided command.

internal/replace/README.md

@@ -0,0 +1,13 @@
+# internal/replace
+
+This package hosts the core building blocks for the `renamer replace` command. The modules are
+organized as follows:
+
+- `request.go` — CLI input parsing, validation, and normalization of pattern/replacement data.
+- `parser.go` — Helpers for token handling (quoting, deduplication, reporting).
+- `traversal.go` — Bridges shared traversal utilities with replace-specific filtering logic.
+- `engine.go` — Applies pattern replacements to candidate names and detects conflicts.
+- `preview.go` / `apply.go` — Orchestrate preview output and apply/ledger integration (added later).
+- `summary.go` — Aggregates match counts and conflict details for previews and ledger entries.
+
+Tests will live alongside the package (unit) and in `tests/contract` + `tests/integration`.

internal/replace/apply.go

@@ -0,0 +1,86 @@
+package replace
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"sort"
+
+	"github.com/rogeecn/renamer/internal/history"
+)
+
+// Apply executes the planned operations and records them in the ledger.
+func Apply(ctx context.Context, req *ReplaceRequest, planned []PlannedOperation, summary Summary) (history.Entry, error) {
+	entry := history.Entry{Command: "replace"}
+
+	if len(planned) == 0 {
+		return entry, nil
+	}
+
+	sort.SliceStable(planned, func(i, j int) bool {
+		return planned[i].Result.Candidate.Depth > planned[j].Result.Candidate.Depth
+	})
+
+	done := make([]history.Operation, 0, len(planned))
+
+	revert := func() error {
+		for i := len(done) - 1; i >= 0; i-- {
+			op := done[i]
+			source := filepath.Join(req.WorkingDir, op.To)
+			destination := filepath.Join(req.WorkingDir, op.From)
+			if err := os.Rename(source, destination); err != nil && !errors.Is(err, os.ErrNotExist) {
+				return err
+			}
+		}
+		return nil
+	}
+
+	for _, op := range planned {
+		if err := ctx.Err(); err != nil {
+			_ = revert()
+			return history.Entry{}, err
+		}
+
+		from := op.Result.Candidate.OriginalPath
+		to := op.TargetAbsolute
+
+		if from == to {
+			continue
+		}
+
+		if err := os.Rename(from, to); err != nil {
+			_ = revert()
+			return history.Entry{}, err
+		}
+
+		done = append(done, history.Operation{
+			From: filepath.ToSlash(op.Result.Candidate.RelativePath),
+			To:   filepath.ToSlash(op.TargetRelative),
+		})
+	}
+
+	if len(done) == 0 {
+		return entry, nil
+	}
+
+	entry.Operations = done
+
+	metadataPatterns := make(map[string]int, len(summary.PatternMatches))
+	for pattern, count := range summary.PatternMatches {
+		metadataPatterns[pattern] = count
+	}
+	entry.Metadata = map[string]any{
+		"patterns":        metadataPatterns,
+		"changed":         summary.ChangedCount,
+		"totalCandidates": summary.TotalCandidates,
+	}
+
+	if err := history.Append(req.WorkingDir, entry); err != nil {
+		// Attempt to undo renames if ledger append fails.
+		_ = revert()
+		return history.Entry{}, err
+	}
+
+	return entry, nil
+}

internal/replace/engine.go

@@ -0,0 +1,38 @@
+package replace
+
+import "strings"
+
+// Result captures the outcome of applying patterns to a candidate name.
+type Result struct {
+	Candidate    Candidate
+	ProposedName string
+	Matches      map[string]int
+	Changed      bool
+}
+
+// ApplyPatterns replaces every occurrence of the provided patterns within the candidate's base name.
+func ApplyPatterns(candidate Candidate, patterns []string, replacement string) Result {
+	current := candidate.BaseName
+	matches := make(map[string]int, len(patterns))
+
+	for _, pattern := range patterns {
+		if pattern == "" {
+			continue
+		}
+		count := strings.Count(current, pattern)
+		if count == 0 {
+			continue
+		}
+		current = strings.ReplaceAll(current, pattern, replacement)
+		matches[pattern] += count
+	}
+
+	changed := current != candidate.BaseName
+
+	return Result{
+		Candidate:    candidate,
+		ProposedName: current,
+		Matches:      matches,
+		Changed:      changed,
+	}
+}

internal/replace/parser.go

@@ -0,0 +1,52 @@
+package replace
+
+import (
+	"errors"
+	"strings"
+)
+
+// ParseArgs splits CLI arguments into patterns and replacement while deduplicating patterns.
+type ParseArgsResult struct {
+	Patterns    []string
+	Replacement string
+	Duplicates  []string
+}
+
+// ParseArgs interprets positional arguments for the replace command.
+// The final token is treated as the replacement; all preceding tokens are literal patterns.
+func ParseArgs(args []string) (ParseArgsResult, error) {
+	if len(args) < 2 {
+		return ParseArgsResult{}, errors.New("provide at least one pattern and a replacement value")
+	}
+
+	replacement := args[len(args)-1]
+	patternTokens := args[:len(args)-1]
+
+	seen := make(map[string]struct{}, len(patternTokens))
+	patterns := make([]string, 0, len(patternTokens))
+	duplicates := make([]string, 0)
+
+	for _, token := range patternTokens {
+		trimmed := strings.TrimSpace(token)
+		if trimmed == "" {
+			continue
+		}
+		key := trimmed
+		if _, ok := seen[key]; ok {
+			duplicates = append(duplicates, trimmed)
+			continue
+		}
+		seen[key] = struct{}{}
+		patterns = append(patterns, trimmed)
+	}
+
+	if len(patterns) == 0 {
+		return ParseArgsResult{}, errors.New("at least one non-empty pattern is required before the replacement")
+	}
+
+	return ParseArgsResult{
+		Patterns:    patterns,
+		Replacement: replacement,
+		Duplicates:  duplicates,
+	}, nil
+}

internal/replace/preview.go

@@ -0,0 +1,111 @@
+package replace
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// PlannedOperation represents a rename that will be executed during apply.
+type PlannedOperation struct {
+	Result         Result
+	TargetRelative string
+	TargetAbsolute string
+}
+
+// Preview computes replacements and writes a human-readable summary to out.
+func Preview(ctx context.Context, req *ReplaceRequest, parseResult ParseArgsResult, out io.Writer) (Summary, []PlannedOperation, error) {
+	summary := NewSummary()
+	for _, dup := range parseResult.Duplicates {
+		summary.AddDuplicate(dup)
+	}
+
+	planned := make([]PlannedOperation, 0)
+	plannedTargets := make(map[string]string) // target rel -> source rel to detect duplicates
+
+	err := TraverseCandidates(ctx, req, func(candidate Candidate) error {
+		res := ApplyPatterns(candidate, parseResult.Patterns, parseResult.Replacement)
+		summary.RecordCandidate(res)
+
+		if !res.Changed {
+			return nil
+		}
+
+		dir := filepath.Dir(candidate.RelativePath)
+		if dir == "." {
+			dir = ""
+		}
+
+		targetRelative := res.ProposedName
+		if dir != "" {
+			targetRelative = filepath.ToSlash(filepath.Join(dir, res.ProposedName))
+		} else {
+			targetRelative = filepath.ToSlash(res.ProposedName)
+		}
+
+		if targetRelative == candidate.RelativePath {
+			return nil
+		}
+
+		if existing, ok := plannedTargets[targetRelative]; ok && existing != candidate.RelativePath {
+			summary.AddConflict(ConflictDetail{
+				OriginalPath: candidate.RelativePath,
+				ProposedPath: targetRelative,
+				Reason:       "duplicate target generated in preview",
+			})
+			return nil
+		}
+
+		targetAbsolute := filepath.Join(req.WorkingDir, filepath.FromSlash(targetRelative))
+		if info, err := os.Stat(targetAbsolute); err == nil {
+			if candidate.OriginalPath != targetAbsolute {
+				// Case-only renames are allowed on case-insensitive filesystems. Compare file identity.
+				if origInfo, origErr := os.Stat(candidate.OriginalPath); origErr == nil {
+					if os.SameFile(info, origInfo) {
+						// Same file—case-only update permitted.
+						goto recordOperation
+					}
+				}
+
+				reason := "target already exists"
+				if info.IsDir() {
+					reason = "target directory already exists"
+				}
+				summary.AddConflict(ConflictDetail{
+					OriginalPath: candidate.RelativePath,
+					ProposedPath: targetRelative,
+					Reason:       reason,
+				})
+				return nil
+			}
+		}
+
+		plannedTargets[targetRelative] = candidate.RelativePath
+
+		if out != nil {
+			fmt.Fprintf(out, "%s -> %s\n", candidate.RelativePath, targetRelative)
+		}
+
+	recordOperation:
+		planned = append(planned, PlannedOperation{
+			Result:         res,
+			TargetRelative: targetRelative,
+			TargetAbsolute: targetAbsolute,
+		})
+
+		return nil
+	})
+	if err != nil {
+		return Summary{}, nil, err
+	}
+
+	if summary.ReplacementWasEmpty(parseResult.Replacement) {
+		if out != nil {
+			fmt.Fprintln(out, "Warning: replacement string is empty; matched patterns will be removed.")
+		}
+	}
+
+	return summary, planned, nil
+}

internal/replace/request.go

@@ -0,0 +1,61 @@
+package replace
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// ReplaceRequest captures all inputs needed to evaluate a replace operation.
+type ReplaceRequest struct {
+	WorkingDir         string
+	Patterns           []string
+	Replacement        string
+	IncludeDirectories bool
+	Recursive          bool
+	IncludeHidden      bool
+	Extensions         []string
+}
+
+// Validate ensures the request is well-formed before preview/apply.
+func (r *ReplaceRequest) Validate() error {
+	if r == nil {
+		return errors.New("replace request cannot be nil")
+	}
+
+	if len(r.Patterns) == 0 {
+		return errors.New("at least one pattern is required")
+	}
+
+	if r.Replacement == "" {
+		// Allow empty replacement but make sure caller has surfaced warnings elsewhere.
+		// No error returned; preview will message accordingly.
+	}
+
+	if r.WorkingDir == "" {
+		cwd, err := os.Getwd()
+		if err != nil {
+			return fmt.Errorf("determine working directory: %w", err)
+		}
+		r.WorkingDir = cwd
+	}
+
+	if !filepath.IsAbs(r.WorkingDir) {
+		abs, err := filepath.Abs(r.WorkingDir)
+		if err != nil {
+			return fmt.Errorf("resolve working directory: %w", err)
+		}
+		r.WorkingDir = abs
+	}
+
+	info, err := os.Stat(r.WorkingDir)
+	if err != nil {
+		return fmt.Errorf("stat working directory: %w", err)
+	}
+	if !info.IsDir() {
+		return fmt.Errorf("working directory %q is not a directory", r.WorkingDir)
+	}
+
+	return nil
+}

internal/replace/summary.go

@@ -0,0 +1,80 @@
+package replace
+
+import "sort"
+
+// ConflictDetail describes a rename that could not be applied.
+type ConflictDetail struct {
+	OriginalPath string
+	ProposedPath string
+	Reason       string
+}
+
+// Summary aggregates metrics for previews, applies, and ledger entries.
+type Summary struct {
+	TotalCandidates  int
+	ChangedCount     int
+	PatternMatches   map[string]int
+	Conflicts        []ConflictDetail
+	Duplicates       []string
+	EmptyReplacement bool
+}
+
+// NewSummary constructs an initialized summary.
+func NewSummary() Summary {
+	return Summary{
+		PatternMatches: make(map[string]int),
+	}
+}
+
+// AddDuplicate records a duplicate pattern supplied by the user.
+func (s *Summary) AddDuplicate(pattern string) {
+	if pattern == "" {
+		return
+	}
+	s.Duplicates = append(s.Duplicates, pattern)
+}
+
+// AddResult incorporates an individual candidate replacement result.
+// RecordCandidate updates aggregate counts for a processed candidate and any matches.
+func (s *Summary) RecordCandidate(res Result) {
+	s.TotalCandidates++
+	if !res.Changed {
+		return
+	}
+	s.ChangedCount++
+	for pattern, count := range res.Matches {
+		s.PatternMatches[pattern] += count
+	}
+}
+
+// AddConflict appends a conflict detail to the summary.
+func (s *Summary) AddConflict(conflict ConflictDetail) {
+	s.Conflicts = append(s.Conflicts, conflict)
+}
+
+// SortedDuplicates returns de-duplicated duplicates list for reporting.
+func (s *Summary) SortedDuplicates() []string {
+	if len(s.Duplicates) == 0 {
+		return nil
+	}
+	copyList := make([]string, 0, len(s.Duplicates))
+	seen := make(map[string]struct{}, len(s.Duplicates))
+	for _, dup := range s.Duplicates {
+		if _, ok := seen[dup]; ok {
+			continue
+		}
+		seen[dup] = struct{}{}
+		copyList = append(copyList, dup)
+	}
+	sort.Strings(copyList)
+	return copyList
+}
+
+// ReplacementWasEmpty records whether the replacement string is empty and returns true.
+func (s *Summary) ReplacementWasEmpty(replacement string) bool {
+	if replacement == "" {
+		s.EmptyReplacement = true
+		return true
+	}
+	return false
+}

internal/replace/traversal.go

@@ -0,0 +1,73 @@
+package replace
+
+import (
+	"context"
+	"io/fs"
+	"path/filepath"
+	"strings"
+
+	"github.com/rogeecn/renamer/internal/traversal"
+)
+
+// Candidate represents a file or directory that may be renamed.
+type Candidate struct {
+	RelativePath string
+	OriginalPath string
+	BaseName     string
+	IsDir        bool
+	Depth        int
+}
+
+// TraverseCandidates walks the working directory according to the request scope and invokes fn for
+// every eligible candidate (files by default, directories when IncludeDirectories is true).
+func TraverseCandidates(ctx context.Context, req *ReplaceRequest, fn func(Candidate) error) error {
+	if err := req.Validate(); err != nil {
+		return err
+	}
+
+	extensions := make(map[string]struct{}, len(req.Extensions))
+	for _, ext := range req.Extensions {
+		lower := strings.ToLower(ext)
+		extensions[lower] = struct{}{}
+	}
+
+	walker := traversal.NewWalker()
+
+	return walker.Walk(
+		req.WorkingDir,
+		req.Recursive,
+		req.IncludeDirectories,
+		req.IncludeHidden,
+		0,
+		func(relPath string, entry fs.DirEntry, depth int) error {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			default:
+			}
+
+			isDir := entry.IsDir()
+			ext := strings.ToLower(filepath.Ext(entry.Name()))
+
+			if !isDir && len(extensions) > 0 {
+				if _, ok := extensions[ext]; !ok {
+					return nil
+				}
+			}
+
+			candidate := Candidate{
+				RelativePath: filepath.ToSlash(relPath),
+				OriginalPath: filepath.Join(req.WorkingDir, relPath),
+				BaseName:     entry.Name(),
+				IsDir:        isDir,
+				Depth:        depth,
+			}
+
+			if candidate.RelativePath == "." {
+				return nil
+			}
+
+			return fn(candidate)
+		},
+	)
+}

scripts/smoke-test-replace.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+BIN="go run"
+TMP_DIR="$(mktemp -d)"
+trap 'rm -rf "$TMP_DIR"' EXIT
+
+mkdir -p "$TMP_DIR/nested"
+touch "$TMP_DIR/foo_draft.txt"
+touch "$TMP_DIR/nested/bar_draft.txt"
+
+echo "Previewing replacements..."
+$BIN "$ROOT_DIR/main.go" replace draft Draft final --path "$TMP_DIR" --recursive --dry-run >/dev/null
+
+echo "Applying replacements..."
+$BIN "$ROOT_DIR/main.go" replace draft Draft final --path "$TMP_DIR" --recursive --yes >/dev/null
+
+if [[ ! -f "$TMP_DIR/foo_final.txt" ]]; then
+  echo "expected foo_final.txt to exist" >&2
+  exit 1
+fi
+
+if [[ ! -f "$TMP_DIR/nested/bar_final.txt" ]]; then
+  echo "expected bar_final.txt to exist" >&2
+  exit 1
+fi
+
+echo "Undoing replacements..."
+$BIN "$ROOT_DIR/main.go" undo --path "$TMP_DIR" >/dev/null
+
+if [[ ! -f "$TMP_DIR/foo_draft.txt" ]]; then
+  echo "undo failed to restore foo_draft.txt" >&2
+  exit 1
+fi
+
+if [[ ! -f "$TMP_DIR/nested/bar_draft.txt" ]]; then
+  echo "undo failed to restore nested/bar_draft.txt" >&2
+  exit 1
+fi
+
+echo "Smoke test succeeded."

specs/002-add-replace-command/checklists/release.md

@@ -0,0 +1,29 @@
+# Release Readiness Checklist: Replace Command with Multi-Pattern Support
+
+**Purpose**: Verify readiness for release / polish phase  
+**Created**: 2025-10-29  
+**Feature**: [spec.md](../spec.md)
+
+## Documentation
+
+- [x] Quickstart reflects latest syntax and automation workflow
+- [x] CLI reference (`docs/cli-flags.md`) includes replace command usage and warnings
+- [x] AGENTS.md updated with replace command summary
+- [x] CHANGELOG entry drafted for replace command
+
+## Quality Gates
+
+- [x] `go test ./...` passing locally
+- [x] Smoke test script for replace + undo exists and runs
+- [x] Ledger metadata includes pattern counts and is asserted in tests
+- [x] Empty replacement path warns users in preview
+
+## Operational Readiness
+
+- [x] `--dry-run` and `--yes` are mutually exclusive and error when combined
+- [x] Undo command reverses replace operations via ledger entry
+- [x] Scope flags behave identically across list/replace commands
+
+## Notes
+
+- Resolve outstanding checklist items prior to tagging release.

specs/002-add-replace-command/checklists/requirements.md

@@ -0,0 +1,34 @@
+# Specification Quality Checklist: Replace Command with Multi-Pattern Support
+
+**Purpose**: Validate specification completeness and quality before proceeding to planning  
+**Created**: 2025-10-29  
+**Feature**: [spec.md](../spec.md)
+
+## Content Quality
+
+- [x] No implementation details (languages, frameworks, APIs)
+- [x] Focused on user value and business needs
+- [x] Written for non-technical stakeholders
+- [x] All mandatory sections completed
+
+## Requirement Completeness
+
+- [x] No [NEEDS CLARIFICATION] markers remain
+- [x] Requirements are testable and unambiguous
+- [x] Success criteria are measurable
+- [x] Success criteria are technology-agnostic (no implementation details)
+- [x] All acceptance scenarios are defined
+- [x] Edge cases are identified
+- [x] Scope is clearly bounded
+- [x] Dependencies and assumptions identified
+
+## Feature Readiness
+
+- [x] All functional requirements have clear acceptance criteria
+- [x] User scenarios cover primary flows
+- [x] Feature meets measurable outcomes defined in Success Criteria
+- [x] No implementation details leak into specification
+
+## Notes
+
+- Items marked incomplete require spec updates before `/speckit.clarify` or `/speckit.plan`

specs/002-add-replace-command/contracts/replace-command.md

@@ -0,0 +1,70 @@
+# CLI Contract: `renamer replace`
+
+## Command Synopsis
+
+```bash
+renamer replace <pattern1> [pattern2 ...] <replacement> [flags]
+```
+
+### Global Flags (inherited from root command)
+- `--path <dir>` (defaults to current working directory)
+- `-r`, `--recursive`
+- `-d`, `--include-dirs`
+- `--hidden`
+- `-e`, `--extensions <.ext|.ext2>`
+- `--yes` — apply without interactive confirmation (used by all mutating commands)
+- `--dry-run` — force preview-only run even if `--yes` is supplied
+
+## Description
+Batch-replace literal substrings across filenames and directories using shared traversal and preview
+infrastructure. All arguments except the final token are treated as patterns; the last argument is
+the replacement value.
+
+## Arguments & Flags
+
+| Argument | Required | Description |
+|----------|----------|-------------|
+| `<pattern...>` | Yes (≥2) | Literal substrings to be replaced. Quotes required when containing spaces. |
+| `<replacement>` | Yes | Final positional argument; literal replacement applied to each pattern. |
+
+| Flag | Type | Default | Description |
+|------|------|---------|-------------|
+| `--path` | string | `.` | Working directory for traversal (global flag). |
+| `-r`, `--recursive` | bool | `false` | Traverse subdirectories depth-first (global flag). |
+| `-d`, `--include-dirs` | bool | `false` | Include directory names in replacement scope (global flag). |
+| `--hidden` | bool | `false` | Include hidden files/directories (global flag). |
+| `-e`, `--extensions` | string | (none) | Restrict replacements to files matching `|`-delimited extensions (global flag). |
+| `--yes` | bool | `false` | Skip confirmation prompt and apply immediately after successful preview (global flag). |
+| `--dry-run` | bool | `false` | Force preview-only run even if `--yes` is provided (global flag). |
+
+## Exit Codes
+
+| Code | Meaning | Example Trigger |
+|------|---------|-----------------|
+| `0` | Success | Preview or apply completed without conflicts. |
+| `2` | Validation error | Fewer than two arguments supplied or unreadable directory. |
+| `3` | Conflict detected | Target filename already exists; user must resolve before retry. |
+
+## Preview Output
+- Lists each impacted file with columns: `PATH`, `MATCHED PATTERN`, `NEW PATH`.
+- Summary line: `Total: <files> (patterns: pattern1=#, pattern2=#, conflicts=#)`.
+
+## Apply Behavior
+- Re-validates preview results before writing changes.
+- Writes ledger entry capturing old/new names, patterns, replacement string, timestamp.
+- On conflict, aborts without partial renames.
+
+## Validation Rules
+- Minimum two unique patterns required (at least one pattern plus replacement).
+- Patterns and replacement treated as UTF-8 literals; no regex expansion.
+- Duplicate patterns deduplicated with warning in preview summary.
+- Replacement applied to every occurrence within file/dir name.
+- Empty replacement allowed but requires confirmation message: "Replacement string is empty; affected substrings will be removed."
+
+## Examples
+
+```bash
+renamer replace draft Draft DRAFT final
+renamer replace "Project X" "Project-X" ProjectX --extensions .txt|.md
+renamer replace tmp temp temp-backup stable --hidden --recursive --yes
+```

specs/002-add-replace-command/data-model.md

@@ -0,0 +1,45 @@
+# Data Model: Replace Command with Multi-Pattern Support
+
+## Entities
+
+### ReplaceRequest
+- **Description**: Captures all inputs driving a replace operation.
+- **Fields**:
+  - `workingDir` (string, required): Absolute path where traversal begins.
+  - `patterns` ([]string, min length 2): Ordered list of literal substrings to replace.
+  - `replacement` (string, required): Literal value substituting each pattern.
+  - `includeDirectories` (bool): Whether directories participate in replacement.
+  - `recursive` (bool): Traverse subdirectories depth-first.
+  - `includeHidden` (bool): Include hidden files during traversal.
+  - `extensions` ([]string): Optional extension filters inherited from scope flags.
+  - `dryRun` (bool): Preview mode flag; true during preview, false when applying changes.
+- **Validations**:
+  - `patterns` MUST be deduplicated case-sensitively before execution.
+  - `replacement` MAY be empty, but command must warn the user during preview.
+  - `workingDir` MUST exist and be readable before traversal.
+
+### ReplaceSummary
+- **Description**: Aggregates preview/apply outcomes for reporting and ledger entries.
+- **Fields**:
+  - `totalFiles` (int): Count of files/directories affected.
+  - `patternMatches` (map[string]int): Total substitutions per pattern.
+  - `conflicts` ([]ConflictDetail): Detected filename collisions with rationale.
+  - `ledgerEntryID` (string, optional): Identifier once committed to `.renamer` ledger.
+
+### ConflictDetail
+- **Description**: Describes a file that could not be renamed due to collision or validation failure.
+- **Fields**:
+  - `originalPath` (string)
+  - `proposedPath` (string)
+  - `reason` (string): Human-readable description (e.g., "target already exists").
+
+## Relationships
+- `ReplaceRequest` produces a stream of candidate rename operations via traversal utilities.
+- `ReplaceSummary` aggregates results from executing the request and is persisted inside ledger entries.
+- `ConflictDetail` records subset of `ReplaceSummary` when collisions block application.
+
+## State Transitions
+1. **Parsing**: CLI args parsed into `ReplaceRequest`; validations run immediately.
+2. **Preview**: Traversal + replacement simulation produce `ReplaceSummary` with proposed paths.
+3. **Confirm**: Upon user confirmation (or `--yes`), operations apply atomically; ledger entry written.
+4. **Undo**: Ledger reverse operation reads `ReplaceSummary` data to restore originals.

specs/002-add-replace-command/plan.md

@@ -0,0 +1,90 @@
+# Implementation Plan: Replace Command with Multi-Pattern Support
+
+**Branch**: `002-add-replace-command` | **Date**: 2025-10-29 | **Spec**: [spec.md](./spec.md)
+**Input**: Feature specification from `/specs/002-add-replace-command/spec.md`
+
+**Note**: This template is filled in by the `/speckit.plan` command. See `.specify/templates/commands/plan.md` for the execution workflow.
+
+## Summary
+
+Introduce a `renamer replace` subcommand that accepts multiple literal patterns and replaces them
+with a single target string while honoring existing preview → confirm → ledger → undo guarantees.
+The feature will extend shared scope flags, reuse traversal/filtering pipelines, and add
+automation-friendly validation and help documentation.
+
+## Technical Context
+
+**Language/Version**: Go 1.24  
+**Primary Dependencies**: `spf13/cobra`, `spf13/pflag`  
+**Storage**: Local filesystem (no persistent database)  
+**Testing**: Go `testing` package with CLI integration/contract tests  
+**Target Platform**: Cross-platform CLI (Linux, macOS, Windows)  
+**Project Type**: Single CLI project  
+**Performance Goals**: Complete preview + apply for 100 files within 2 minutes  
+**Constraints**: Deterministic previews, reversible ledger entries, conflict detection before apply  
+**Scale/Scope**: Handles hundreds of files per invocation; patterns limited to user-provided literals
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+- Preview flow MUST show deterministic rename mappings and require explicit confirmation (Preview-First Safety).
+- Undo strategy MUST describe how the `.renamer` ledger entry is written and reversed (Persistent Undo Ledger).
+- Planned rename rules MUST document their inputs, validations, and composing order (Composable Rule Engine).
+- Scope handling MUST cover files vs directories (`-d`), recursion (`-r`), and extension filtering via `-e` without escaping the requested path (Scope-Aware Traversal).
+- CLI UX plan MUST confirm Cobra usage, flag naming, help text, and automated tests for preview/undo flows (Ergonomic CLI Stewardship).
+
+**Gate Alignment**:
+- Replace command will reuse preview + confirmation pipeline; no direct rename without preview.
+- Ledger entries will include replacement mappings to maintain undo guarantees.
+- Replacement logic will be implemented as composable rule(s) integrating with existing rename engine.
+- Command will rely on shared scope flags (`--path`, `-r`, `-d`, `--hidden`, `-e`) to avoid divergence.
+- Cobra command structure and automated tests will cover help/validation/undo parity.
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/002-add-replace-command/
+├── plan.md
+├── research.md
+├── data-model.md
+├── quickstart.md
+├── contracts/
+└── tasks.md
+```
+
+### Source Code (repository root)
+
+```text
+cmd/
+├── root.go
+└── list.go (existing CLI commands; replace command will be added here or alongside)
+
+internal/
+├── listing/
+├── output/
+├── traversal/
+└── (new replace-specific packages under internal/replace/)
+
+scripts/
+└── smoke-test-list.sh
+
+tests/
+├── contract/
+├── integration/
+└── fixtures/
+
+docs/
+└── cli-flags.md
+```
+
+**Structure Decision**: Single CLI repository with commands under `cmd/` and reusable logic under
+`internal/`. Replace-specific logic will live in `internal/replace/` (request parsing, rule engine,
+summary). CLI command wiring will reside in `cmd/replace.go`. Tests will follow existing
+contract/integration directories.
+
+## Complexity Tracking
+
+No constitution gate violations identified; additional complexity justification not required.

specs/002-add-replace-command/quickstart.md

@@ -0,0 +1,63 @@
+# Quickstart: Replace Command with Multi-Pattern Support
+
+## Goal
+Demonstrate how to consolidate multiple filename patterns into a single replacement while using the
+preview → apply → undo workflow safely.
+
+## Prerequisites
+- Go toolchain (>= 1.24) installed for building the CLI locally.
+- Sample directory with files containing inconsistent substrings (e.g., `draft`, `Draft`, `DRAFT`).
+
+## Steps
+
+1. **Build the CLI**
+   ```bash
+   go build -o renamer ./...
+   ```
+
+2. **Inspect replace help**
+   ```bash
+   ./renamer replace --help
+   ```
+   Review syntax, especially the "final argument is replacement" guidance and quoting rules.
+
+3. **Run a preview with multiple patterns**
+   ```bash
+   ./renamer replace draft Draft DRAFT final --dry-run
+   ```
+   Confirm the table shows each occurrence mapped to `final` and the summary lists per-pattern counts.
+
+4. **Apply replacements after review**
+   ```bash
+   ./renamer replace draft Draft DRAFT final --yes
+   ```
+   Observe the confirmation summary, then verify file names have been updated.
+
+5. **Undo if necessary**
+   ```bash
+   ./renamer undo
+   ```
+   Ensure the ledger entry created by step 4 is reversed and filenames restored.
+
+6. **Handle patterns with spaces**
+   ```bash
+   ./renamer replace "Project X" "Project-X" ProjectX --dry-run
+   ```
+   Verify that quoting preserves whitespace and the preview reflects the intended substitution.
+
+7. **Combine with scope filters**
+   ```bash
+ ./renamer replace tmp temp stable --path ./examples --extensions .log|.txt --recursive
+  ```
+  Confirm only matching files under `./examples` are listed.
+
+8. **Integrate into automation**
+   ```bash
+   ./renamer replace draft Draft final --dry-run && \
+   ./renamer replace draft Draft final --yes
+   ```
+   The first command previews changes; the second applies them with exit code `0` when successful.
+
+## Next Steps
+- Add contract/integration tests covering edge cases (empty replacement, conflicts).
+- Update documentation (`docs/cli-flags.md`, README) with replace command examples.

specs/002-add-replace-command/research.md

@@ -0,0 +1,32 @@
+# Phase 0 Research: Replace Command with Multi-Pattern Support
+
+## Decision: Literal substring replacement with ordered evaluation
+- **Rationale**: Aligns with current rename semantics and keeps user expectations simple for first
+  iteration; avoids complexity of regex/glob interactions. Ordered application ensures predictable
+  handling of overlapping patterns.
+- **Alternatives considered**:
+  - *Regex support*: powerful but significantly increases validation surface and user errors.
+  - *Simultaneous substitution without order*: risk of ambiguous conflicts when one pattern is subset
+    of another.
+
+## Decision: Dedicated replace service under `internal/replace`
+- **Rationale**: Keeps responsibilities separated from existing listing module, enabling reusable
+  preview + apply logic while encapsulating pattern parsing, summary, and reporting.
+- **Alternatives considered**:
+  - *Extending existing listing package*: would blur responsibilities between read-only listing and
+    mutation workflows.
+  - *Embedding in command file*: hinders testability and violates composable rule principle.
+
+## Decision: Pattern delimiter syntax `with`
+- **Rationale**: Matches user description and provides a clear boundary between patterns and
+  replacement string. Works well with Cobra argument parsing and allows quoting for whitespace.
+- **Alternatives considered**:
+  - *Using flags for replacement string*: more verbose and inconsistent with provided example.
+  - *Special separators like `--`*: less descriptive and increases documentation burden.
+
+## Decision: Conflict detection before apply
+- **Rationale**: Maintains Preview-First Safety by ensuring duplicates or invalid filesystem names are
+  reported before commit. Reuses existing validation helpers from rename pipeline.
+- **Alternatives considered**:
+  - *Best-effort renames with partial success*: violates atomic undo expectations.
+  - *Skipping conflicting files silently*: unsafe and would erode trust.

specs/002-add-replace-command/spec.md

@@ -0,0 +1,115 @@
+# Feature Specification: Replace Command with Multi-Pattern Support
+
+**Feature Branch**: `002-add-replace-command`  
+**Created**: 2025-10-29  
+**Status**: Draft  
+**Input**: User description: "添加 替换（replace）命令，用于替换指定的字符串，支持同时对多个字符串进行替换为一个 示例： renamer replace pattern1 pattern2 with space pattern3 <replacement>"
+
+## Clarifications
+
+### Session 2025-10-29
+
+- Q: What syntax separates patterns from the replacement value? → A: The final positional argument is the replacement; no delimiter keyword is used.
+
+## User Scenarios & Testing *(mandatory)*
+
+### User Story 1 - Normalize Naming with One Command (Priority: P1)
+
+As a CLI user cleaning messy filenames, I want to run `renamer replace` with multiple source
+patterns so I can normalize all variants to a single replacement in one pass.
+
+**Why this priority**: Unlocks the main value proposition—batch consolidation of inconsistent
+substrings without writing custom scripts.
+
+**Independent Test**: Execute `renamer list` to confirm scope, then `renamer replace foo bar Baz`
+and verify preview shows every `foo` and `bar` occurrence replaced with `Baz` before confirming.
+
+**Acceptance Scenarios**:
+
+1. **Given** files containing `draft`, `Draft`, and `DRAFT`, **When** the user runs `renamer replace draft Draft DRAFT final`, **Then** the preview lists every filename replaced with `final`, and execution applies the same mapping.
+2. **Given** filenames where patterns appear multiple times, **When** the user runs `renamer replace beta gamma release`, **Then** each occurrence within a single filename is substituted, and the summary highlights total replacements per file.
+
+---
+
+### User Story 2 - Script-Friendly Replacement Workflows (Priority: P2)
+
+As an operator embedding renamer in automation, I want deterministic exit codes and reusable
+profiles for replace operations so scripts can preview, apply, and undo safely.
+
+**Why this priority**: Ensures pipelines can rely on the command without interactive ambiguity.
+
+**Independent Test**: In a CI script, run `renamer replace ... --dry-run` (preview), assert exit code
+0, then run with `--yes` and check ledger entry plus `renamer undo` restores originals.
+
+**Acceptance Scenarios**:
+
+1. **Given** a non-interactive environment, **When** the user passes `--yes` to apply replacements after a successful preview, **Then** the command exits 0 on success and writes a ledger entry capturing all mappings.
+2. **Given** an invalid argument (e.g., only one token supplied), **When** the command executes, **Then** it exits with a non-zero code and explains that the final positional argument becomes the replacement value.
+
+---
+
+### User Story 3 - Validate Complex Pattern Input (Priority: P3)
+
+As a power user handling patterns with spaces or special characters, I want clear syntax guidance
+and validation feedback so I can craft replacements confidently.
+
+**Why this priority**: Prevents user frustration when patterns require quoting or escaping.
+
+**Independent Test**: Run `renamer replace "Project X" "Project-X" ProjectX` and confirm preview
+resolves both variants, while invalid quoting produces actionable guidance.
+
+**Acceptance Scenarios**:
+
+1. **Given** a pattern containing whitespace, **When** it is provided in quotes, **Then** the preview reflects the intended substring and documentation shows identical syntax describing the final argument as replacement.
+2. **Given** duplicate patterns in the same command, **When** the command runs, **Then** duplicates are deduplicated with a warning so replacements remain idempotent.
+
+---
+
+### Edge Cases
+
+- Replacement produces duplicate target filenames; command must surface conflicts before confirmation.
+- Patterns overlap within the same filename (e.g., `aaa` replaced via `aa`); order of application must be deterministic and documented.
+- Case-sensitivity opt-in: default literal matching is case-sensitive, but a future `--ignore-case` option is deferred; command must warn that matches are case-sensitive.
+- Replacement string empty (aka deletion); preview must show empty substitution clearly and require explicit confirmation.
+- No files match any pattern; command exits 0 with "No entries matched" messaging and no ledger entry.
+
+## Requirements *(mandatory)*
+
+### Functional Requirements
+
+- **FR-001**: The CLI MUST expose `renamer replace <pattern...> <replacement>` and treat all but the final token as literal patterns (quotes support whitespace).
+- **FR-002**: Replace operations MUST integrate with the existing preview → confirm workflow; previews list old and new names with highlighted substrings.
+- **FR-003**: Executions MUST append detailed entries to `.renamer` including original names, replacements performed, patterns supplied, and timestamps so undo remains possible.
+- **FR-004**: Users MUST be able to undo the most recent replace batch via existing undo mechanics without orphaned files.
+- **FR-005**: Command MUST respect global scope flags (`--recursive`, `--include-dirs`, `--hidden`, `--extensions`, `--path`) identical to `list` / `preview` behavior.
+- **FR-006**: Command MUST accept two or more patterns and collapse them into a single replacement string applied to every filename in scope.
+- **FR-007**: Command MUST preserve idempotence by deduplicating patterns and reporting the number of substitutions per pattern in summary output.
+- **FR-008**: Invalid invocations (fewer than two arguments, empty pattern list after deduplication, missing replacement) MUST fail with exit code ≠0 and actionable usage guidance.
+- **FR-009**: CLI help MUST document quoting rules for patterns containing spaces or shell special characters.
+
+### Key Entities *(include if feature involves data)*
+
+- **ReplaceRequest**: Captures working directory, scope flags, ordered pattern list, replacement string, and preview/apply options.
+- **ReplaceSummary**: Aggregates per-pattern match counts, per-file changes, and conflict warnings for preview and ledger output.
+
+## Success Criteria *(mandatory)*
+
+### Measurable Outcomes
+
+- **SC-001**: Users complete a multi-pattern replacement across 100 files with preview + apply in under 2 minutes end-to-end.
+- **SC-002**: 95% of usability test participants interpret the final positional replacement argument correctly after reading `renamer replace --help`.
+- **SC-003**: Automated regression tests confirm replace + undo leave the filesystem unchanged in 100% of scripted scenarios.
+- **SC-004**: Support tickets related to manual string normalization drop by 40% within the first release cycle after launch.
+
+## Assumptions
+
+- Patterns are treated as literal substrings; regex support is out of scope for this increment.
+- Case-sensitive matching aligns with current rename semantics; advanced matching can be added later.
+- Replacement applies to filenames (and directories when `-d`/`--include-dirs` is set), not file contents.
+- Existing infrastructure for preview, ledger, and undo can be extended without architectural changes.
+
+## Dependencies & Risks
+
+- Requires updates to shared traversal/filter utilities so replace respects global scope flags.
+- Help/quickstart documentation must be updated alongside the command to prevent misuse.
+- Potential filename conflicts must be detected pre-apply to avoid data loss; conflict handling relies on existing validation pipeline.

specs/002-add-replace-command/tasks.md

@@ -0,0 +1,169 @@
+# Tasks: Replace Command with Multi-Pattern Support
+
+**Input**: Design documents from `/specs/002-add-replace-command/`
+**Prerequisites**: plan.md (required), spec.md (required for user stories), research.md, data-model.md, contracts/
+
+**Tests**: Tests are optional; include them only where they support the user story’s independent validation.
+
+**Organization**: Tasks are grouped by user story to enable independent implementation and testing of each story.
+
+## Format: `[ID] [P?] [Story] Description`
+
+- **[P]**: Can run in parallel (different files, no dependencies)
+- **[Story]**: Which user story this task belongs to (e.g., US1, US2, US3)
+- Include exact file paths in descriptions
+
+## Phase 1: Setup (Shared Infrastructure)
+
+**Purpose**: Prepare project for replace command implementation
+
+- [X] T001 Audit root command for shared flags; document expected additions in `cmd/root.go`
+- [X] T002 Create replace package scaffold in `internal/replace/README.md` with intended module layout
+- [X] T003 Add sample fixtures directory for replacement tests at `tests/fixtures/replace-samples/README.md`
+
+---
+
+## Phase 2: Foundational (Blocking Prerequisites)
+
+**Purpose**: Core utilities required by every user story
+
+**⚠️ CRITICAL**: No user story work can begin until this phase is complete
+
+- [X] T004 Implement `ReplaceRequest` struct and validators in `internal/replace/request.go`
+- [X] T005 [P] Implement pattern parser handling quoting/deduplication in `internal/replace/parser.go`
+- [X] T006 [P] Extend traversal utilities to emit replace candidates in `internal/replace/traversal.go`
+- [X] T007 [P] Implement replacement engine with overlap handling in `internal/replace/engine.go`
+- [X] T008 Define summary metrics and conflict structs in `internal/replace/summary.go`
+- [X] T009 Document replace syntax and flags draft in `docs/cli-flags.md`
+
+**Checkpoint**: Foundation ready—user story implementation can begin
+
+---
+
+## Phase 3: User Story 1 - Normalize Naming with One Command (Priority: P1) 🎯 MVP
+
+**Goal**: Deliver multi-pattern replacement with preview + apply guarantees
+
+**Independent Test**: `renamer replace foo bar Baz --dry-run` followed by `--yes`; verify preview shows replacements, apply updates files, and `renamer undo` restores originals.
+
+### Tests for User Story 1 (OPTIONAL - included for confidence)
+
+- [X] T010 [P] [US1] Contract test for preview summary counts in `tests/contract/replace_command_test.go`
+- [X] T011 [P] [US1] Integration test covering multi-pattern apply + undo in `tests/integration/replace_flow_test.go`
+
+### Implementation for User Story 1
+
+- [X] T012 [US1] Implement CLI command wiring in `cmd/replace.go` using shared scope flags
+- [X] T013 [US1] Implement preview rendering and summary output in `internal/replace/preview.go`
+- [X] T014 [US1] Hook replace engine into ledger/undo pipeline in `internal/replace/apply.go`
+- [X] T015 [US1] Add documentation examples to `docs/cli-flags.md` and quickstart
+
+**Checkpoint**: User Story 1 delivers functional `renamer replace` with preview/apply/undo
+
+---
+
+## Phase 4: User Story 2 - Script-Friendly Replacement Workflows (Priority: P2)
+
+**Goal**: Ensure automation-friendly behaviors (exit codes, non-interactive usage)
+
+**Independent Test**: Scripted run invoking `renamer replace ... --dry-run` then `--yes`; expect consistent exit codes and ledger entry
+
+### Implementation for User Story 2
+
+- [X] T016 [US2] Implement non-interactive flag validation (`--yes` + positional args) in `cmd/replace.go`
+- [X] T017 [US2] Add ledger metadata (pattern counts) for automation in `internal/replace/summary.go`
+- [X] T018 [US2] Expand integration test to assert exit codes for invalid input in `tests/integration/replace_flow_test.go`
+- [X] T019 [US2] Update quickstart section with automation guidance in `specs/002-add-replace-command/quickstart.md`
+
+**Checkpoint**: Scripts can rely on deterministic exit codes and ledger data
+
+---
+
+## Phase 5: User Story 3 - Validate Complex Pattern Input (Priority: P3)
+
+**Goal**: Provide resilient handling for whitespace/special-character patterns and user guidance
+
+**Independent Test**: `renamer replace "Project X" "Project-X" ProjectX --dry-run` plus invalid quoting to verify errors
+
+### Implementation for User Story 3
+
+- [X] T020 [P] [US3] Implement quoting guidance and warnings in `cmd/replace.go`
+- [X] T021 [P] [US3] Add parser coverage for whitespace patterns in `tests/unit/replace_parser_test.go`
+- [X] T022 [US3] Surface duplicate pattern warnings in preview summary in `internal/replace/preview.go`
+- [X] T023 [US3] Document advanced pattern examples in `docs/cli-flags.md`
+
+**Checkpoint**: Power users receive clear guidance and validation feedback
+
+---
+
+## Phase N: Polish & Cross-Cutting Concerns
+
+**Purpose**: Final validation, documentation, and release readiness
+
+- [X] T024 Update agent guidance with replace command details in `AGENTS.md`
+- [X] T025 Add changelog entry describing new replace command in `docs/CHANGELOG.md`
+- [X] T026 Create smoke test script covering replace + undo in `scripts/smoke-test-replace.sh`
+
+---
+
+## Dependencies & Execution Order
+
+### Phase Dependencies
+
+- **Setup (Phase 1)**: No prerequisites
+- **Foundational (Phase 2)**: Depends on setup completion; blocks all user stories
+- **User Story 1 (Phase 3)**: Depends on foundational phase; MVP delivery
+- **User Story 2 (Phase 4)**: Depends on User Story 1 (automation builds on base command)
+- **User Story 3 (Phase 5)**: Depends on User Story 1 (parser/extensions) and shares foundation
+- **Polish (Phase N)**: Runs after user stories complete
+
+### User Story Dependencies
+
+- **US1**: Requires foundational tasks
+- **US2**: Requires US1 implementation + ledger integration
+- **US3**: Requires US1 parser and preview infrastructure
+
+### Within Each User Story
+
+- Tests (if included) should be authored before implementation tasks
+- Parser/engine updates precede CLI wiring
+- Documentation updates finalize after behavior stabilizes
+
+### Parallel Opportunities
+
+- Foundational parser/engine/summary tasks (T005–T008) can progress in parallel after T004
+- US1 tests (T010–T011) can run alongside command wiring (T012–T014)
+- US3 parser coverage (T021) can proceed independently while warnings (T022) integrate with preview
+
+---
+
+## Parallel Example: User Story 1
+
+```bash
+# Terminal 1: Write contract test and run in watch mode
+go test ./tests/contract -run TestReplaceCommandPreview
+
+# Terminal 2: Implement preview renderer
+$EDITOR internal/replace/preview.go
+```
+
+---
+
+## Implementation Strategy
+
+### MVP First (User Story 1)
+1. Complete Setup and Foundational phases
+2. Implement US1 tasks (T010–T015)
+3. Ensure preview/apply/undo works end-to-end
+
+### Incremental Delivery
+1. Ship US1 (core replace command)
+2. Layer US2 (automation-friendly exit codes and ledger metadata)
+3. Add US3 (advanced pattern validation)
+4. Execute polish tasks for documentation and smoke tests
+
+### Parallel Team Strategy
+- Engineer A: Parser/engine/summary foundational work
+- Engineer B: CLI command wiring + tests (US1)
+- Engineer C: Automation behaviors and documentation (US2/Polish)
+- After US1, shift Engineers to handle US3 enhancements and polish concurrently

testdata/replace/README.md

@@ -0,0 +1,27 @@
+# Replace Command Fixtures
+
+This directory contains lightweight fixtures for manual and automated testing of the `renamer
+replace` command.
+
+## Structure
+
+```
+replace/
+├── case-sensitivity/
+│   ├── draft.txt
+│   ├── Draft.txt
+│   └── README.md
+├── multi-pattern/
+│   ├── alpha-beta.txt
+│   ├── beta-gamma.log
+│   ├── nested/
+│   │   └── gamma-delta.md
+│   └── README.md
+└── hidden-files/
+    ├── .draft.tmp
+    ├── notes.txt
+    └── README.md
+```
+
+Each subdirectory contains intentionally blank files used to verify preview, apply, and undo
+behaviour. Customize or copy these fixtures as needed for new tests.

testdata/replace/case-sensitivity/README.md

@@ -0,0 +1,3 @@
+Case-insensitive filesystem fixture.
+
+Use these files to verify case-only replacements, e.g. `renamer replace draft Draft`.

testdata/replace/hidden-files/README.md

@@ -0,0 +1,3 @@
+Hidden files fixture.
+
+Use to validate `--hidden` flag handling with replace command.

testdata/replace/multi-pattern/README.md

@@ -0,0 +1,4 @@
+Multi-pattern replacement fixture.
+
+Example usage:
+renamer replace alpha beta gamma final --path testdata/replace/multi-pattern --recursive --dry-run

tests/contract/replace_command_test.go

@@ -0,0 +1,102 @@
+package contract
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/rogeecn/renamer/internal/replace"
+)
+
+func TestPreviewSummaryCounts(t *testing.T) {
+	tmp := t.TempDir()
+	createFile(t, filepath.Join(tmp, "draft.txt"))
+	createFile(t, filepath.Join(tmp, "Draft.md"))
+	createFile(t, filepath.Join(tmp, "notes", "DRAFT.log"))
+
+	args := []string{"draft", "Draft", "DRAFT", "final"}
+	parsed, err := replace.ParseArgs(args)
+	if err != nil {
+		t.Fatalf("ParseArgs error: %v", err)
+	}
+
+	req := &replace.ReplaceRequest{
+		WorkingDir:  tmp,
+		Patterns:    parsed.Patterns,
+		Replacement: parsed.Replacement,
+		Recursive:   true,
+	}
+
+	var buf bytes.Buffer
+	summary, planned, err := replace.Preview(context.Background(), req, parsed, &buf)
+	if err != nil {
+		t.Fatalf("Preview error: %v", err)
+	}
+
+	if summary.TotalCandidates == 0 {
+		t.Fatalf("expected candidates to be processed")
+	}
+
+	if summary.ChangedCount != len(planned) {
+		t.Fatalf("changed count mismatch: %d vs %d", summary.ChangedCount, len(planned))
+	}
+
+	for _, pattern := range []string{"draft", "Draft", "DRAFT"} {
+		if summary.PatternMatches[pattern] == 0 {
+			t.Fatalf("expected matches recorded for %s", pattern)
+		}
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "draft.txt -> final.txt") {
+		t.Fatalf("expected preview output to list replacements, got: %s", output)
+	}
+
+	if summary.ReplacementWasEmpty(parsed.Replacement) {
+		t.Fatalf("replacement should not be empty warning for this test")
+	}
+}
+
+func TestPreviewWarnsOnEmptyReplacement(t *testing.T) {
+	tmp := t.TempDir()
+	createFile(t, filepath.Join(tmp, "foo.txt"))
+
+	args := []string{"foo", ""}
+	parsed, err := replace.ParseArgs(args)
+	if err != nil {
+		t.Fatalf("ParseArgs error: %v", err)
+	}
+
+	req := &replace.ReplaceRequest{
+		WorkingDir:  tmp,
+		Patterns:    parsed.Patterns,
+		Replacement: parsed.Replacement,
+	}
+
+	var buf bytes.Buffer
+	summary, _, err := replace.Preview(context.Background(), req, parsed, &buf)
+	if err != nil {
+		t.Fatalf("Preview error: %v", err)
+	}
+
+	if !summary.EmptyReplacement {
+		t.Fatalf("expected empty replacement flag to be set")
+	}
+
+	if !strings.Contains(buf.String(), "Warning: replacement string is empty") {
+		t.Fatalf("expected empty replacement warning in preview output")
+	}
+}
+
+func createFile(t *testing.T, path string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("mkdir %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, []byte("test"), 0o644); err != nil {
+		t.Fatalf("write file %s: %v", path, err)
+	}
+}

tests/fixtures/replace-samples/README.md

@@ -0,0 +1,9 @@
+# Replace Command Fixtures
+
+Use this directory to store sample file trees referenced by replace command tests. Keep fixtures
+minimal and platform-neutral (ASCII names, small files). Create subdirectories per scenario, e.g.:
+
+- `basic/` — Simple files demonstrating multi-pattern replacements.
+- `conflicts/` — Cases that intentionally trigger name collisions for validation.
+
+File contents are typically irrelevant; create empty files unless a test requires data.

tests/integration/replace_flow_test.go

@@ -0,0 +1,101 @@
+package integration
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	renamercmd "github.com/rogeecn/renamer/cmd"
+	"github.com/rogeecn/renamer/internal/history"
+	"github.com/rogeecn/renamer/internal/replace"
+)
+
+func TestReplaceApplyAndUndo(t *testing.T) {
+	tmp := t.TempDir()
+
+	createFile(t, filepath.Join(tmp, "foo_draft.txt"))
+	createFile(t, filepath.Join(tmp, "bar_draft.txt"))
+
+	parsed, err := replace.ParseArgs([]string{"draft", "final"})
+	if err != nil {
+		t.Fatalf("ParseArgs error: %v", err)
+	}
+
+	req := &replace.ReplaceRequest{
+		WorkingDir:  tmp,
+		Patterns:    parsed.Patterns,
+		Replacement: parsed.Replacement,
+	}
+
+	summary, planned, err := replace.Preview(context.Background(), req, parsed, nil)
+	if err != nil {
+		t.Fatalf("Preview error: %v", err)
+	}
+	if summary.ChangedCount != 2 {
+		t.Fatalf("expected 2 changes, got %d", summary.ChangedCount)
+	}
+
+	entry, err := replace.Apply(context.Background(), req, planned, summary)
+	if err != nil {
+		t.Fatalf("apply error: %v", err)
+	}
+
+	if len(entry.Operations) != 2 {
+		t.Fatalf("expected 2 operations recorded, got %d", len(entry.Operations))
+	}
+	if entry.Metadata == nil {
+		t.Fatalf("expected metadata to be recorded")
+	}
+	counts, ok := entry.Metadata["patterns"].(map[string]int)
+	if !ok {
+		t.Fatalf("patterns metadata missing or wrong type: %#v", entry.Metadata)
+	}
+	if counts["draft"] != 2 {
+		t.Fatalf("expected pattern count for 'draft' to be 2, got %d", counts["draft"])
+	}
+
+	if _, err := os.Stat(filepath.Join(tmp, "foo_final.txt")); err != nil {
+		t.Fatalf("expected renamed file exists: %v", err)
+	}
+
+	if _, err := os.Stat(filepath.Join(tmp, "bar_final.txt")); err != nil {
+		t.Fatalf("expected renamed file exists: %v", err)
+	}
+
+	_, err = history.Undo(tmp)
+	if err != nil {
+		t.Fatalf("undo error: %v", err)
+	}
+
+	if _, err := os.Stat(filepath.Join(tmp, "foo_draft.txt")); err != nil {
+		t.Fatalf("expected original file after undo: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(tmp, "bar_draft.txt")); err != nil {
+		t.Fatalf("expected original file after undo: %v", err)
+	}
+}
+
+func TestReplaceCommandInvalidArgs(t *testing.T) {
+	root := renamercmd.NewRootCommand()
+	var out bytes.Buffer
+	root.SetOut(&out)
+	root.SetErr(&out)
+	root.SetArgs([]string{"replace", "onlyone"})
+
+	err := root.Execute()
+	if err == nil {
+		t.Fatalf("expected error for insufficient arguments")
+	}
+}
+
+func createFile(t *testing.T, path string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("mkdir %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, []byte("x"), 0o644); err != nil {
+		t.Fatalf("write file %s: %v", path, err)
+	}
+}

tests/unit/replace_parser_test.go

@@ -0,0 +1,31 @@
+package replace_test
+
+import (
+	"testing"
+
+	"github.com/rogeecn/renamer/internal/replace"
+)
+
+func TestParseArgsHandlesWhitespaceAndDuplicates(t *testing.T) {
+	args := []string{"  draft  ", "Draft", "draft", "final"}
+	result, err := replace.ParseArgs(args)
+	if err != nil {
+		t.Fatalf("ParseArgs returned error: %v", err)
+	}
+
+	if len(result.Patterns) != 2 {
+		t.Fatalf("expected 2 unique patterns, got %d", len(result.Patterns))
+	}
+	if len(result.Duplicates) != 1 {
+		t.Fatalf("expected duplicate reported, got %d", len(result.Duplicates))
+	}
+	if result.Replacement != "final" {
+		t.Fatalf("replacement mismatch: %s", result.Replacement)
+	}
+}
+
+func TestParseArgsRequiresSufficientTokens(t *testing.T) {
+	if _, err := replace.ParseArgs([]string{"onlyone"}); err == nil {
+		t.Fatalf("expected error when replacement missing")
+	}
+}