feat: add @file autocomplete and context attachment

Type @ in the input to trigger a fuzzy file picker popup. Files are
discovered via git ls-files (with os.ReadDir fallback), scored by
fuzzy match, and displayed in the existing autocomplete popup.

Tab/Enter inserts the selected path; directories keep the popup open
for drilling. On submit, @file tokens are expanded into XML-wrapped
file content before being sent to the agent. No CWD restriction —
supports ~/, ../, and absolute paths.

README.md

@@ -13,4 +13,495 @@
 
 # KIT (Knowledge Inference Tool)
 
-TBD
+A powerful, extensible AI coding agent CLI with multi-provider support, built-in tools, and a rich extension system.
+
+## Features
+
+- **Multi-Provider LLM Support**: Anthropic, OpenAI, Google Gemini, Ollama, Azure OpenAI, AWS Bedrock, OpenRouter, and more
+- **Built-in Core Tools**: bash, read, write, edit, grep, find, ls - no MCP overhead
+- **MCP Integration**: Connect external MCP servers for expanded capabilities
+- **Extension System**: Write custom tools, commands, widgets, and UI modifications in Go
+- **Interactive TUI**: Rich terminal interface powered by Bubble Tea with streaming, syntax highlighting, and custom rendering
+- **Session Management**: Tree-based conversation history with branching support
+- **Non-Interactive Mode**: Script-friendly `--prompt` mode with JSON output
+- **Go SDK**: Embed Kit in your own applications
+
+## Installation
+
+### Using npm (recommended)
+
+```bash
+npm install -g @mark3labs/kit
+```
+
+### Using Go
+
+```bash
+go install github.com/mark3labs/kit/cmd/kit@latest
+```
+
+### Building from source
+
+```bash
+git clone https://github.com/mark3labs/kit.git
+cd kit
+go build -o kit ./cmd/kit
+```
+
+## Quick Start
+
+### Basic Usage
+
+```bash
+# Start interactive session
+kit
+
+# Run a one-off prompt
+kit --prompt "List files in src/"
+
+# Continue the most recent session
+kit --continue
+
+# Use specific model
+kit --model anthropic/claude-sonnet-4-5-20250929
+```
+
+### Non-Interactive Mode
+
+```bash
+# Get JSON output for scripting
+kit --prompt "Explain main.go" --json
+
+# Quiet mode (final response only)
+kit --quiet --prompt "Run tests"
+
+# Ephemeral mode (no session file)
+kit --prompt "Quick question" --no-session
+```
+
+## Configuration
+
+Kit looks for configuration in the following locations (in order of priority):
+
+1. CLI flags
+2. Environment variables (with `KIT_` prefix)
+3. `./.kit.yml` (project-local)
+4. `~/.kit.yml` (global)
+
+### Basic Configuration
+
+Create `~/.kit.yml`:
+
+```yaml
+model: anthropic/claude-sonnet-4-5-20250929
+max-tokens: 4096
+temperature: 0.7
+stream: true
+```
+
+### Environment Variables
+
+```bash
+export ANTHROPIC_API_KEY="sk-..."
+export OPENAI_API_KEY="sk-..."
+export KIT_MODEL="openai/gpt-4o"
+```
+
+### MCP Server Configuration
+
+Add external MCP servers to `.kit.yml`:
+
+```yaml
+mcpServers:
+  filesystem:
+    type: local
+    command: ["npx", "-y", "@modelcontextprotocol/server-filesystem", "/path/to/allowed"]
+    environment:
+      LOG_LEVEL: "info"
+    allowedTools: ["read_file", "write_file"]
+  
+  search:
+    type: remote
+    url: "https://mcp.example.com/search"
+```
+
+## CLI Reference
+
+### Global Flags
+
+```bash
+# Model and provider
+--model, -m              Model to use (provider/model format)
+--provider-api-key       API key for the provider
+--provider-url           Base URL for provider API
+--tls-skip-verify        Skip TLS certificate verification
+
+# Session management
+--session, -s            Open specific JSONL session file
+--continue, -c           Resume most recent session for current directory
+--resume, -r             Interactive session picker
+--no-session             Ephemeral mode, no persistence
+
+# Behavior
+--prompt, -p             Run in non-interactive mode with given prompt
+--quiet                  Suppress all output (only with --prompt)
+--json                   Output response as JSON (only with --prompt)
+--no-exit                Continue to interactive mode after --prompt
+--max-steps              Maximum agent steps (0 for unlimited)
+--stream                 Enable streaming output (default: true)
+--compact                Enable compact output mode
+--auto-compact           Auto-compact conversation near context limit
+
+# Extensions
+--extension, -e          Load additional extension file(s) (repeatable)
+--no-extensions          Disable all extensions
+
+# Generation parameters
+--max-tokens             Maximum tokens in response (default: 4096)
+--temperature            Randomness 0.0-1.0 (default: 0.7)
+--top-p                  Nucleus sampling 0.0-1.0 (default: 0.95)
+--top-k                  Limit top K tokens (default: 40)
+--stop-sequences         Custom stop sequences (comma-separated)
+
+# System
+--config                 Config file path (default: ~/.kit.yml)
+--system-prompt          System prompt text or file path
+--debug                  Enable debug logging
+```
+
+### Commands
+
+```bash
+# Authentication (for OAuth-enabled providers)
+kit auth login           # Start OAuth flow
+kit auth logout          # Remove credentials
+kit auth status          # Check authentication status
+
+# Model database
+kit models               # List available models
+kit models --all         # Show all providers (not just Fantasy-compatible)
+kit update-models        # Update local model database from models.dev
+
+# Extension management
+kit extensions list      # List discovered extensions
+kit extensions validate  # Validate extension files
+kit extensions init      # Generate example extension template
+```
+
+## Extension System
+
+Extensions are Go source files that run via Yaegi interpreter. They can add custom tools, slash commands, widgets, keyboard shortcuts, and intercept lifecycle events.
+
+### Minimal Extension
+
+```go
+//go:build ignore
+
+package main
+
+import "kit/ext"
+
+func Init(api ext.API) {
+    api.OnSessionStart(func(_ ext.SessionStartEvent, ctx ext.Context) {
+        ctx.SetFooter(ext.HeaderFooterConfig{
+            Content: ext.WidgetContent{Text: "Custom Footer"},
+        })
+    })
+}
+```
+
+**Usage:**
+
+```bash
+kit -e examples/extensions/minimal.go
+```
+
+### Extension Capabilities
+
+**Lifecycle Events**: OnSessionStart, OnSessionShutdown, OnAgentStart, OnAgentEnd, OnToolCall, OnToolResult, OnInput, OnMessageStart, OnMessageUpdate, OnMessageEnd, OnModelChange, OnContextPrepare, OnBeforeFork, OnBeforeSessionSwitch, OnBeforeCompact
+
+**Custom Components**:
+- **Tools**: Add new tools the LLM can invoke
+- **Commands**: Register slash commands (e.g., `/mycommand`)
+- **Widgets**: Persistent status displays above/below input
+- **Shortcuts**: Global keyboard shortcuts
+- **Overlays**: Modal dialogs with markdown content
+- **Tool Renderers**: Customize how tool calls display
+- **Editor Interceptors**: Handle key events and wrap rendering
+
+### Extension Examples
+
+See the `examples/extensions/` directory:
+
+- `minimal.go` - Clean UI with custom footer
+- `notify.go` - Desktop notifications
+- `widget-status.go` - Persistent status widgets
+- `custom-editor-demo.go` - Vim-like modal editor
+- `prompt-demo.go` - Interactive prompts (select/confirm/input)
+- `tool-logger.go` - Log all tool calls
+- `overlay-demo.go` - Modal dialogs
+- `plan-mode.go` - Read-only planning mode
+- `subagent-widget.go` - Multi-agent orchestration
+- `auto-commit.go` - Auto-commit on shutdown
+
+### Loading Extensions
+
+**Auto-discovery** (loads automatically):
+- `./.kit/extensions/*.go` (project-local)
+- `~/.config/kit/extensions/*.go` (global)
+
+**Explicit loading**:
+```bash
+kit -e path/to/extension.go
+kit -e ext1.go -e ext2.go  # Multiple extensions
+```
+
+**Disable auto-load**:
+```bash
+kit --no-extensions
+```
+
+## Session Management
+
+Kit uses a tree-based session model that supports branching and forking conversations.
+
+### Session Locations
+
+- Default: `~/.local/share/kit/sessions/<cwd-hash>/<uuid>.jsonl`
+- Each line is a session entry (messages, tool calls, extension data)
+- Supports branching from any message to explore alternate paths
+
+### Session Commands
+
+```bash
+# Resume most recent session for current directory
+kit --continue
+kit -c
+
+# Interactive session picker
+kit --resume
+kit -r
+
+# Open specific session file
+kit --session path/to/session.jsonl
+kit -s path/to/session.jsonl
+
+# Ephemeral mode (no file persistence)
+kit --no-session
+```
+
+## Go SDK
+
+Embed Kit in your Go applications:
+
+```go
+package main
+
+import (
+    "context"
+    "log"
+    
+    kit "github.com/mark3labs/kit/pkg/kit"
+)
+
+func main() {
+    ctx := context.Background()
+    
+    // Create Kit instance with default configuration
+    host, err := kit.New(ctx, nil)
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer host.Close()
+    
+    // Send a prompt
+    response, err := host.Prompt(ctx, "What is 2+2?")
+    if err != nil {
+        log.Fatal(err)
+    }
+    
+    println(response)
+}
+```
+
+### With Options
+
+```go
+host, err := kit.New(ctx, &kit.Options{
+    Model:        "ollama/llama3",
+    SystemPrompt: "You are a helpful bot",
+    ConfigFile:   "/path/to/config.yml",
+    MaxSteps:     10,
+    Streaming:    true,
+    Quiet:        true,
+})
+```
+
+### With Callbacks
+
+```go
+response, err := host.PromptWithCallbacks(
+    ctx,
+    "List files in current directory",
+    func(name, args string) {
+        // Tool call started
+        println("Calling tool:", name)
+    },
+    func(name, args, result string, isError bool) {
+        // Tool call completed
+        if isError {
+            println("Tool failed:", name)
+        }
+    },
+    func(chunk string) {
+        // Streaming text chunk
+        print(chunk)
+    },
+)
+```
+
+### Session Management
+
+```go
+host.Prompt(ctx, "My name is Alice")
+response, _ := host.Prompt(ctx, "What's my name?")
+
+host.SaveSession("./session.json")
+host.LoadSession("./session.json")
+host.ClearSession()
+```
+
+## Advanced Usage
+
+### Subagent Pattern
+
+Spawn Kit as a subprocess for multi-agent orchestration:
+
+```bash
+kit --prompt "Analyze codebase" \
+    --json \
+    --no-session \
+    --no-extensions \
+    --quiet \
+    --model anthropic/claude-haiku-3-5-20241022
+```
+
+Parse the JSON output:
+
+```json
+{
+  "response": "Final assistant response text",
+  "model": "anthropic/claude-haiku-3-5-20241022",
+  "usage": {
+    "input_tokens": 1024,
+    "output_tokens": 512,
+    "total_tokens": 1536
+  },
+  "messages": [...]
+}
+```
+
+### Testing with tmux
+
+Test the TUI non-interactively:
+
+```bash
+# Start Kit in detached tmux session
+tmux new-session -d -s kittest -x 120 -y 40 \
+  "kit -e ext.go --no-session 2>kit.log"
+
+# Wait for startup
+sleep 3
+
+# Capture screen
+tmux capture-pane -t kittest -p
+
+# Send input
+tmux send-keys -t kittest '/command' Enter
+
+# Cleanup
+tmux kill-session -t kittest
+```
+
+## Development
+
+### Build and Test
+
+```bash
+# Build
+go build -o output/kit ./cmd/kit
+
+# Run tests
+go test -race ./...
+
+# Run specific test
+go test -race ./cmd -run TestScriptExecution
+
+# Lint
+go vet ./...
+
+# Format
+go fmt ./...
+```
+
+### Project Structure
+
+```
+cmd/kit/           - CLI entry point
+cmd/               - CLI command implementations
+pkg/kit/           - Go SDK
+internal/agent/    - Agent loop and tool execution
+internal/ui/       - Bubble Tea TUI components
+internal/extensions/ - Yaegi extension system
+internal/core/     - Built-in tools
+internal/tools/    - MCP tool integration
+internal/config/   - Configuration management
+internal/session/  - Session persistence
+internal/models/   - Provider and model management
+examples/extensions/ - Example extension files
+```
+
+## Supported Providers
+
+- **Anthropic** - Claude models (native, prompt caching, OAuth)
+- **OpenAI** - GPT models
+- **Google** - Gemini models
+- **Ollama** - Local models
+- **Azure OpenAI** - Azure-hosted OpenAI
+- **AWS Bedrock** - Bedrock models
+- **Google Vertex** - Claude on Vertex AI
+- **OpenRouter** - Multi-provider router
+- **Vercel AI** - Vercel AI SDK models
+- **Auto-routed** - Any provider from models.dev database
+
+### Model String Format
+
+```bash
+provider/model            # Standard format
+anthropic/claude-sonnet-4-5-20250929
+openai/gpt-4o
+ollama/llama3
+google/gemini-2.0-flash-exp
+```
+
+### Model Aliases
+
+```bash
+claude-opus-latest      → claude-opus-4-20250514
+claude-sonnet-latest    → claude-sonnet-4-5-20250929
+claude-3-5-haiku-latest → claude-3-5-haiku-20241022
+```
+
+## Contributing
+
+Contributions are welcome! Please see [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines.
+
+## License
+
+[Apache 2.0](LICENSE)
+
+## Community
+
+- [Discord](https://discord.gg/RqSS2NQVsY)
+- [GitHub Issues](https://github.com/mark3labs/kit/issues)
+- [Documentation](https://github.com/mark3labs/kit/wiki)

cmd/root.go

@@ -1065,11 +1065,13 @@ func runInteractiveModeBubbleTea(_ context.Context, appInstance *app.App, modelN
 		termHeight = 24
 	}
 
+	cwd, _ := os.Getwd()
 	appModel := ui.NewAppModel(appInstance, ui.AppModelOptions{
 		CompactMode:             viper.GetBool("compact"),
 		ModelName:               modelName,
 		ProviderName:            providerName,
 		LoadingMessage:          loadingMessage,
+		Cwd:                     cwd,
 		Width:                   termWidth,
 		Height:                  termHeight,
 		ServerNames:             serverNames,

internal/ui/file_processor.go

@@ -0,0 +1,129 @@
+package ui
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+// fileTokenPattern matches @file references in user text. Supports:
+//   - @"path with spaces.txt" (quoted)
+//   - @path/to/file.txt      (unquoted, no spaces)
+var fileTokenPattern = regexp.MustCompile(`@"[^"]+"|@[^\s]+`)
+
+// ProcessFileAttachments scans the user's input text for @file references,
+// reads each referenced file, and returns the text with @tokens replaced by
+// XML-wrapped file content. Non-file @ tokens (like email addresses) are left
+// unchanged.
+//
+// Returns the original text unchanged if no valid @file references are found.
+func ProcessFileAttachments(text string, cwd string) string {
+	tokens := fileTokenPattern.FindAllString(text, -1)
+	if len(tokens) == 0 {
+		return text
+	}
+
+	result := text
+	for _, token := range tokens {
+		path := tokenToPath(token)
+		if path == "" {
+			continue
+		}
+
+		absPath, err := resolvePath(path, cwd)
+		if err != nil {
+			// Not a valid file reference — leave the token as-is.
+			// This handles cases like email addresses (@user) gracefully.
+			continue
+		}
+
+		info, err := os.Stat(absPath)
+		if err != nil {
+			continue
+		}
+
+		// Skip directories — we only attach file content.
+		if info.IsDir() {
+			continue
+		}
+
+		// Skip empty files.
+		if info.Size() == 0 {
+			continue
+		}
+
+		content, err := os.ReadFile(absPath)
+		if err != nil {
+			continue
+		}
+
+		// Build the XML-wrapped replacement.
+		wrapped := wrapFileContent(absPath, content)
+		result = strings.Replace(result, token, wrapped, 1)
+	}
+
+	return result
+}
+
+// tokenToPath strips the @ prefix and optional quotes from a token,
+// returning the raw file path. Returns "" for invalid tokens.
+func tokenToPath(token string) string {
+	if !strings.HasPrefix(token, "@") {
+		return ""
+	}
+	path := token[1:]
+
+	// Strip quotes.
+	if strings.HasPrefix(path, `"`) && strings.HasSuffix(path, `"`) {
+		path = path[1 : len(path)-1]
+	}
+
+	// Reject obviously non-file tokens (e.g. bare @ or @-flags).
+	if path == "" || strings.HasPrefix(path, "-") {
+		return ""
+	}
+
+	return path
+}
+
+// resolvePath resolves a potentially relative file path to an absolute path.
+// Supports ~/ expansion and relative paths. No CWD restriction — the user
+// can reference any file they have read access to.
+func resolvePath(path string, cwd string) (string, error) {
+	// Expand ~/
+	if strings.HasPrefix(path, "~/") {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return "", fmt.Errorf("cannot expand ~: %w", err)
+		}
+		path = filepath.Join(home, path[2:])
+	}
+
+	// Resolve relative to cwd.
+	if !filepath.IsAbs(path) {
+		path = filepath.Join(cwd, path)
+	}
+
+	// Clean and resolve symlinks for consistent paths.
+	absPath, err := filepath.Abs(path)
+	if err != nil {
+		return "", fmt.Errorf("invalid path: %w", err)
+	}
+
+	// Resolve symlinks so the displayed path is canonical.
+	resolved, err := filepath.EvalSymlinks(absPath)
+	if err != nil {
+		// EvalSymlinks fails if the file doesn't exist — fall back to
+		// the cleaned absolute path and let the caller's Stat handle it.
+		return absPath, nil
+	}
+
+	return resolved, nil
+}
+
+// wrapFileContent wraps file content in XML tags for LLM consumption.
+func wrapFileContent(absPath string, content []byte) string {
+	return fmt.Sprintf("<file path=\"%s\">\n%s\n</file>", absPath, string(content))
+}

internal/ui/file_suggestions.go

@@ -0,0 +1,389 @@
+package ui
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sort"
+	"strings"
+	"unicode/utf8"
+)
+
+// FileSuggestion represents a single file or directory suggestion for the @
+// autocomplete popup.
+type FileSuggestion struct {
+	// RelPath is the path relative to the search base (e.g. "cmd/kit/main.go").
+	RelPath string
+	// IsDir is true when the entry is a directory.
+	IsDir bool
+	// Score is the fuzzy match score (higher is better).
+	Score int
+}
+
+// maxFileSuggestions is the maximum number of file suggestions returned.
+const maxFileSuggestions = 20
+
+// ExtractAtPrefix checks the current line for an @-file trigger at cursorCol.
+// It returns:
+//   - hasAt: true if a valid @ trigger was found
+//   - prefix: the text after @ (possibly empty) that the user has typed so far
+//   - startIdx: byte offset of the @ character in the line
+//
+// The @ must appear at the start of the line or after whitespace. Quoted paths
+// are supported: @"path with spaces" — the returned prefix strips quotes.
+func ExtractAtPrefix(line string, cursorCol int) (hasAt bool, prefix string, startIdx int) {
+	if cursorCol > len(line) {
+		cursorCol = len(line)
+	}
+
+	// Walk backwards from cursorCol to find the @ character.
+	text := line[:cursorCol]
+
+	// Find the last @ that is preceded by whitespace or is at position 0.
+	atIdx := -1
+	for i := len(text) - 1; i >= 0; i-- {
+		if text[i] == '@' {
+			// Must be at start of line or preceded by whitespace.
+			if i == 0 || text[i-1] == ' ' || text[i-1] == '\t' {
+				atIdx = i
+				break
+			}
+		}
+		// Stop scanning if we hit a space — the @ we want must be in the
+		// current "word".
+		if text[i] == ' ' || text[i] == '\t' {
+			break
+		}
+	}
+
+	if atIdx < 0 {
+		return false, "", 0
+	}
+
+	raw := text[atIdx+1:]
+
+	// Handle quoted paths: @"some path" — strip leading quote.
+	if strings.HasPrefix(raw, `"`) {
+		raw = strings.TrimPrefix(raw, `"`)
+		raw = strings.TrimSuffix(raw, `"`)
+	}
+
+	return true, raw, atIdx
+}
+
+// GetFileSuggestions returns file/directory suggestions matching the given
+// prefix. It tries `git ls-files` first (fast, respects .gitignore), then
+// falls back to a simple directory walk.
+//
+// If prefix contains a path separator the search is scoped to that
+// subdirectory. For example, prefix "cmd/k" searches inside "cmd/" for
+// entries matching "k".
+func GetFileSuggestions(prefix string, cwd string) []FileSuggestion {
+	// Resolve the base directory and filter query from the prefix.
+	baseDir, query := splitPrefixPath(prefix)
+
+	searchDir := cwd
+	if baseDir != "" {
+		candidate := resolveSearchDir(baseDir, cwd)
+		if info, err := os.Stat(candidate); err == nil && info.IsDir() {
+			searchDir = candidate
+		} else {
+			return nil // invalid base directory
+		}
+	}
+
+	files := listFiles(searchDir, cwd)
+	if len(files) == 0 {
+		return nil
+	}
+
+	// Prepend baseDir so results display as "cmd/main.go" not just "main.go".
+	if baseDir != "" {
+		for i := range files {
+			files[i].RelPath = baseDir + files[i].RelPath
+		}
+	}
+
+	return fuzzyFilterFiles(files, prefix, query)
+}
+
+// splitPrefixPath separates a prefix like "cmd/kit/m" into
+// baseDir="cmd/kit/" and query="m". If there is no separator the
+// baseDir is empty and query is the full prefix.
+func splitPrefixPath(prefix string) (baseDir, query string) {
+	// Handle ~ expansion display (we keep it in the prefix for display
+	// but resolve it when actually searching).
+	idx := strings.LastIndex(prefix, "/")
+	if idx < 0 {
+		return "", prefix
+	}
+	return prefix[:idx+1], prefix[idx+1:]
+}
+
+// resolveSearchDir converts a baseDir from the prefix into an absolute path.
+// Supports ~/, ../, and absolute paths.
+func resolveSearchDir(baseDir, cwd string) string {
+	// Expand ~/
+	if strings.HasPrefix(baseDir, "~/") {
+		if home, err := os.UserHomeDir(); err == nil {
+			return filepath.Join(home, baseDir[2:])
+		}
+	}
+
+	// Absolute paths
+	if filepath.IsAbs(baseDir) {
+		return filepath.Clean(baseDir)
+	}
+
+	// Relative to cwd
+	return filepath.Join(cwd, baseDir)
+}
+
+// listFiles returns files and directories within searchDir, relative to that
+// directory. Uses `git ls-files` when inside a git repo for speed and
+// .gitignore awareness, otherwise falls back to os.ReadDir.
+func listFiles(searchDir, cwd string) []FileSuggestion {
+	// Try git ls-files first (fast, respects .gitignore).
+	if files := listFilesGit(searchDir, cwd); files != nil {
+		return files
+	}
+	return listFilesReadDir(searchDir)
+}
+
+// listFilesGit uses `git ls-files` and `git ls-files --others --exclude-standard`
+// to list tracked and untracked-but-not-ignored files.
+func listFilesGit(searchDir, cwd string) []FileSuggestion {
+	// Check if we're in a git repo.
+	check := exec.Command("git", "rev-parse", "--show-toplevel")
+	check.Dir = cwd
+	if err := check.Run(); err != nil {
+		return nil
+	}
+
+	seen := make(map[string]bool)
+	var results []FileSuggestion
+
+	// Tracked files.
+	cmd := exec.Command("git", "ls-files")
+	cmd.Dir = searchDir
+	out, err := cmd.Output()
+	if err == nil {
+		for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
+			if line == "" {
+				continue
+			}
+			// Normalize separators.
+			line = filepath.ToSlash(line)
+			addFileEntries(&results, seen, line, searchDir)
+		}
+	}
+
+	// Untracked, non-ignored files.
+	cmd2 := exec.Command("git", "ls-files", "--others", "--exclude-standard")
+	cmd2.Dir = searchDir
+	out2, err := cmd2.Output()
+	if err == nil {
+		for _, line := range strings.Split(strings.TrimSpace(string(out2)), "\n") {
+			if line == "" {
+				continue
+			}
+			line = filepath.ToSlash(line)
+			addFileEntries(&results, seen, line, searchDir)
+		}
+	}
+
+	if len(results) == 0 {
+		return nil
+	}
+	return results
+}
+
+// addFileEntries adds the file and any intermediate directory entries to
+// results if not already seen. Paths are stored with forward slashes.
+func addFileEntries(results *[]FileSuggestion, seen map[string]bool, relPath string, searchDir string) {
+	// Add intermediate directories as suggestions (first component only).
+	parts := strings.SplitN(relPath, "/", 2)
+	if len(parts) > 1 {
+		dir := parts[0] + "/"
+		if !seen[dir] {
+			seen[dir] = true
+			*results = append(*results, FileSuggestion{RelPath: dir, IsDir: true})
+		}
+	}
+
+	// Add the file itself.
+	if !seen[relPath] {
+		seen[relPath] = true
+		*results = append(*results, FileSuggestion{RelPath: relPath, IsDir: false})
+	}
+}
+
+// listFilesReadDir is the fallback when git is not available. Lists immediate
+// children of dir via os.ReadDir, skipping hidden dirs and common noise.
+func listFilesReadDir(dir string) []FileSuggestion {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil
+	}
+
+	skip := map[string]bool{
+		".git": true, "node_modules": true, ".kit": true,
+		"__pycache__": true, ".venv": true, "vendor": true,
+	}
+
+	var results []FileSuggestion
+	for _, e := range entries {
+		name := e.Name()
+		if skip[name] {
+			continue
+		}
+		// Skip hidden files/dirs (except common config files).
+		if strings.HasPrefix(name, ".") && name != ".env" && name != ".gitignore" {
+			continue
+		}
+		if e.IsDir() {
+			results = append(results, FileSuggestion{RelPath: name + "/", IsDir: true})
+		} else {
+			results = append(results, FileSuggestion{RelPath: name, IsDir: false})
+		}
+	}
+	return results
+}
+
+// fuzzyFilterFiles scores and filters file suggestions against the query,
+// returning the top maxFileSuggestions results sorted by score descending.
+// Directories are boosted slightly so they appear near the top.
+func fuzzyFilterFiles(files []FileSuggestion, fullPrefix, query string) []FileSuggestion {
+	if query == "" && fullPrefix == "" {
+		// No filter — return all (capped).
+		if len(files) > maxFileSuggestions {
+			files = files[:maxFileSuggestions]
+		}
+		return files
+	}
+
+	// When there's a base dir but no query (e.g. "cmd/"), show everything
+	// in that directory.
+	if query == "" {
+		var filtered []FileSuggestion
+		for i := range files {
+			if strings.HasPrefix(files[i].RelPath, fullPrefix) {
+				// Only show direct children of the base directory.
+				rest := files[i].RelPath[len(fullPrefix):]
+				if rest == "" {
+					continue
+				}
+				filtered = append(filtered, files[i])
+			}
+		}
+		if len(filtered) > maxFileSuggestions {
+			filtered = filtered[:maxFileSuggestions]
+		}
+		return filtered
+	}
+
+	var scored []FileSuggestion
+	queryLower := strings.ToLower(query)
+
+	for i := range files {
+		path := files[i].RelPath
+		// When we have a fullPrefix with a dir component, only consider
+		// files under that directory.
+		if fullPrefix != query && !strings.HasPrefix(path, fullPrefix[:len(fullPrefix)-len(query)]) {
+			continue
+		}
+
+		score := scoreFilePath(queryLower, path)
+		if score <= 0 {
+			continue
+		}
+
+		// Boost directories so they appear near the top for navigation.
+		if files[i].IsDir {
+			score += 10
+		}
+
+		files[i].Score = score
+		scored = append(scored, files[i])
+	}
+
+	// Sort by score descending.
+	sort.Slice(scored, func(i, j int) bool {
+		return scored[i].Score > scored[j].Score
+	})
+
+	if len(scored) > maxFileSuggestions {
+		scored = scored[:maxFileSuggestions]
+	}
+	return scored
+}
+
+// scoreFilePath scores a file path against a fuzzy query. Higher is better.
+// Returns 0 if there is no match.
+func scoreFilePath(query, path string) int {
+	pathLower := strings.ToLower(path)
+	baseName := filepath.Base(strings.TrimSuffix(path, "/"))
+	baseNameLower := strings.ToLower(baseName)
+
+	// Exact basename match.
+	if baseNameLower == query {
+		return 1000
+	}
+
+	// Basename starts with query.
+	if strings.HasPrefix(baseNameLower, query) {
+		return 800 - len(baseName) + len(query)
+	}
+
+	// Basename contains query as substring.
+	if strings.Contains(baseNameLower, query) {
+		return 500 - len(baseName) + len(query)
+	}
+
+	// Full path contains query as substring.
+	if strings.Contains(pathLower, query) {
+		return 300 - len(path) + len(query)
+	}
+
+	// Fuzzy character match on basename.
+	if score := fuzzyCharMatch(query, baseNameLower); score > 0 {
+		return score
+	}
+
+	// Fuzzy character match on full path.
+	if score := fuzzyCharMatch(query, pathLower); score > 0 {
+		return score - 50
+	}
+
+	return 0
+}
+
+// fuzzyCharMatch performs character-by-character fuzzy matching. Returns a
+// positive score if all query characters appear in order in the target.
+func fuzzyCharMatch(query, target string) int {
+	if utf8.RuneCountInString(query) > utf8.RuneCountInString(target) {
+		return 0
+	}
+
+	qRunes := []rune(query)
+	tRunes := []rune(target)
+	qi := 0
+	score := 100
+	consecutive := 0
+
+	for ti := 0; ti < len(tRunes) && qi < len(qRunes); ti++ {
+		if tRunes[ti] == qRunes[qi] {
+			qi++
+			consecutive++
+			score += consecutive * 5
+		} else {
+			consecutive = 0
+			score -= 2
+		}
+	}
+
+	if qi < len(qRunes) {
+		return 0
+	}
+	return score
+}

internal/ui/input.go

@@ -43,6 +43,18 @@ type InputComponent struct {
 	argCommand   string         // command prefix for arg mode (e.g. "/bookmark")
 	argSynthCmds []SlashCommand // backing storage for synthetic arg entries
 
+	// File completion state. When the user types @ followed by a partial
+	// file path, the popup shows file/directory suggestions from the cwd.
+	fileMode        bool             // true when showing @file completions
+	filePrefix      string           // current text after @ being matched
+	fileAtStartIdx  int              // byte offset of @ in the textarea value
+	fileSuggestions []FileSuggestion // backing storage for file entries
+	fileSynthCmds   []SlashCommand   // synthetic SlashCommands wrapping file entries
+
+	// cwd is the working directory used for @file path resolution and
+	// autocomplete suggestions. Set by the parent via SetCwd.
+	cwd string
+
 	// appCtrl is used for slash commands that mutate app state.
 	// May be nil in tests; nil-safe.
 	appCtrl AppController
@@ -90,6 +102,12 @@ func NewInputComponent(width int, title string, appCtrl AppController) *InputCom
 	}
 }
 
+// SetCwd sets the working directory used for @file autocomplete suggestions
+// and path resolution. Should be called by the parent after construction.
+func (s *InputComponent) SetCwd(cwd string) {
+	s.cwd = cwd
+}
+
 // Init implements tea.Model. Starts the cursor blink animation.
 func (s *InputComponent) Init() tea.Cmd {
 	return textarea.Blink
@@ -148,19 +166,29 @@ func (s *InputComponent) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 
 			case key.Matches(msg, key.NewBinding(key.WithKeys("tab"))):
 				if s.selected < len(s.filtered) {
-					if s.argMode {
+					if s.fileMode {
+						s.applyFileCompletion(s.selected)
+					} else if s.argMode {
 						s.textarea.SetValue(s.argCommand + " " + s.filtered[s.selected].Command.Name)
+						s.showPopup = false
+						s.selected = 0
 					} else {
 						s.textarea.SetValue(s.filtered[s.selected].Command.Name)
+						s.showPopup = false
+						s.selected = 0
 					}
-					s.showPopup = false
-					s.selected = 0
 					s.textarea.CursorEnd()
 				}
 				return s, nil
 
 			case key.Matches(msg, key.NewBinding(key.WithKeys("enter"))):
 				if s.selected < len(s.filtered) {
+					if s.fileMode {
+						// Apply file completion but don't submit.
+						s.applyFileCompletion(s.selected)
+						s.textarea.CursorEnd()
+						return s, nil
+					}
 					// Populate textarea with selected item and submit on next tick.
 					if s.argMode {
 						s.textarea.SetValue(s.argCommand + " " + s.filtered[s.selected].Command.Name)
@@ -190,7 +218,37 @@ func (s *InputComponent) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		if value != s.lastValue {
 			s.lastValue = value
 			lines := strings.Split(value, "\n")
-			if len(lines) == 1 && strings.HasPrefix(lines[0], "/") {
+			line := lines[len(lines)-1] // current line (last line for multi-line)
+
+			// Check for @file trigger first.
+			cursorCol := len(line) // approximate: cursor is at end after typing
+			if hasAt, prefix, atIdx := ExtractAtPrefix(line, cursorCol); hasAt && s.cwd != "" {
+				suggestions := GetFileSuggestions(prefix, s.cwd)
+				if len(suggestions) > 0 {
+					s.showPopup = true
+					s.fileMode = true
+					s.argMode = false
+					s.filePrefix = prefix
+					s.fileAtStartIdx = atIdx
+					s.fileSuggestions = suggestions
+					s.fileSynthCmds = make([]SlashCommand, len(suggestions))
+					s.filtered = make([]FuzzyMatch, len(suggestions))
+					for i, fs := range suggestions {
+						name := fs.RelPath
+						desc := ""
+						if fs.IsDir {
+							desc = "directory"
+						}
+						s.fileSynthCmds[i] = SlashCommand{Name: name, Description: desc}
+						s.filtered[i] = FuzzyMatch{Command: &s.fileSynthCmds[i], Score: fs.Score}
+					}
+					s.selected = 0
+				} else {
+					s.showPopup = false
+					s.fileMode = false
+				}
+			} else if len(lines) == 1 && strings.HasPrefix(lines[0], "/") {
+				s.fileMode = false
 				if !strings.Contains(lines[0], " ") {
 					// Command name completion.
 					s.showPopup = true
@@ -210,6 +268,7 @@ func (s *InputComponent) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			} else {
 				s.showPopup = false
 				s.argMode = false
+				s.fileMode = false
 			}
 		}
 		return s, cmd
@@ -335,16 +394,32 @@ func (s *InputComponent) renderPopup() string {
 			descStyle = descStyle.Foreground(lipgloss.Color("250"))
 		}
 
-		nameWidth := 15
-		name := nameStyle.Width(nameWidth - 2).Render(sc.Name)
+		if s.fileMode {
+			// File mode: use full width for the path, show description
+			// (e.g. "directory") inline after a gap.
+			maxNameLen := s.width - 24
+			displayName := sc.Name
+			if len(displayName) > maxNameLen && maxNameLen > 3 {
+				displayName = displayName[:maxNameLen-3] + "..."
+			}
+			name := nameStyle.Render(displayName)
+			if sc.Description != "" {
+				items = append(items, indicator+name+"  "+descStyle.Render(sc.Description))
+			} else {
+				items = append(items, indicator+name)
+			}
+		} else {
+			nameWidth := 15
+			name := nameStyle.Width(nameWidth - 2).Render(sc.Name)
 
-		desc := sc.Description
-		maxDescLen := s.width - nameWidth - 14
-		if len(desc) > maxDescLen && maxDescLen > 3 {
-			desc = desc[:maxDescLen-3] + "..."
+			desc := sc.Description
+			maxDescLen := s.width - nameWidth - 14
+			if len(desc) > maxDescLen && maxDescLen > 3 {
+				desc = desc[:maxDescLen-3] + "..."
+			}
+
+			items = append(items, indicator+name+descStyle.Render(desc))
 		}
-
-		items = append(items, indicator+name+descStyle.Render(desc))
 	}
 
 	if startIdx > 0 {
@@ -404,3 +479,56 @@ func (s *InputComponent) findCommandWithComplete(name string) *SlashCommand {
 	}
 	return nil
 }
+
+// applyFileCompletion replaces the @prefix in the textarea with the selected
+// file suggestion. For directories, it keeps the popup open for further
+// drilling. For files, it closes the popup and adds a trailing space.
+func (s *InputComponent) applyFileCompletion(idx int) {
+	if idx >= len(s.fileSuggestions) {
+		return
+	}
+
+	suggestion := s.fileSuggestions[idx]
+	value := s.textarea.Value()
+
+	// Build the replacement text. The @ and everything after it up to the
+	// cursor should be replaced with @<selected path>.
+	// Find the current line's contribution.
+	lines := strings.Split(value, "\n")
+	lastLine := lines[len(lines)-1]
+
+	// Reconstruct: everything before the @ on the last line + @<path>
+	beforeAt := lastLine[:s.fileAtStartIdx]
+	needsQuote := strings.Contains(suggestion.RelPath, " ")
+
+	var replacement string
+	if needsQuote {
+		replacement = `@"` + suggestion.RelPath + `"`
+	} else {
+		replacement = "@" + suggestion.RelPath
+	}
+
+	// For files, add a trailing space. For directories, don't — allow
+	// continued drilling into the directory.
+	if !suggestion.IsDir {
+		replacement += " "
+	}
+
+	newLastLine := beforeAt + replacement
+
+	// Reconstruct the full value with the updated last line.
+	lines[len(lines)-1] = newLastLine
+	newValue := strings.Join(lines, "\n")
+
+	s.textarea.SetValue(newValue)
+	s.textarea.CursorEnd()
+
+	if suggestion.IsDir {
+		// Keep popup open — trigger a refresh for the new directory.
+		s.lastValue = "" // force re-evaluation on next update tick
+	} else {
+		s.showPopup = false
+		s.fileMode = false
+		s.selected = 0
+	}
+}

internal/ui/model.go

@@ -201,6 +201,10 @@ type AppModelOptions struct {
 	// (e.g. GPU fallback info). Displayed at startup when non-empty.
 	LoadingMessage string
 
+	// Cwd is the working directory for @file autocomplete and path resolution.
+	// If empty, @file features are disabled.
+	Cwd string
+
 	// Width is the initial terminal width in columns.
 	Width int
 
@@ -449,6 +453,9 @@ type AppModel struct {
 	// so the model can return to it when the overlay completes.
 	preOverlayState appState
 
+	// cwd is the working directory for @file path resolution.
+	cwd string
+
 	// width and height track the terminal dimensions.
 	width  int
 	height int
@@ -526,6 +533,7 @@ func NewAppModel(appCtrl AppController, opts AppModelOptions) *AppModel {
 		serverNames:    opts.ServerNames,
 		toolNames:      opts.ToolNames,
 		usageTracker:   opts.UsageTracker,
+		cwd:            opts.Cwd,
 		width:          width,
 		height:         height,
 	}
@@ -552,6 +560,11 @@ func NewAppModel(appCtrl AppController, opts AppModelOptions) *AppModel {
 	// Wire up child components now that we have the concrete implementations.
 	m.input = NewInputComponent(width, "Enter your prompt (Type /help for commands, Ctrl+C to quit)", appCtrl)
 
+	// Wire up cwd for @file autocomplete.
+	if ic, ok := m.input.(*InputComponent); ok && opts.Cwd != "" {
+		ic.SetCwd(opts.Cwd)
+	}
+
 	// Merge extension commands into the InputComponent's autocomplete source.
 	if ic, ok := m.input.(*InputComponent); ok && len(opts.ExtensionCommands) > 0 {
 		for _, ec := range opts.ExtensionCommands {
@@ -705,34 +718,31 @@ func (m *AppModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 				}
 			}
 
-			// Emit before-fork event — extensions can cancel the operation.
+			// Emit before-fork event in a goroutine so that extension handlers
+			// can call blocking operations (e.g. ctx.PromptConfirm) without
+			// deadlocking the BubbleTea event loop.
 			if m.emitBeforeFork != nil {
-				if cancelled, reason := m.emitBeforeFork(targetID, msg.IsUser, msg.UserText); cancelled {
-					m.treeSelector = nil
-					m.state = stateInput
-					return m, m.printSystemMessage(reason)
-				}
+				emit := m.emitBeforeFork
+				ctrl := m.appCtrl
+				forkTargetID := targetID
+				forkIsUser := msg.IsUser
+				forkUserText := msg.UserText
+				go func() {
+					cancelled, reason := emit(forkTargetID, forkIsUser, forkUserText)
+					ctrl.SendEvent(beforeForkResultMsg{
+						cancelled: cancelled,
+						reason:    reason,
+						targetID:  forkTargetID,
+						isUser:    forkIsUser,
+						userText:  forkUserText,
+					})
+				}()
+				m.treeSelector = nil
+				m.state = stateInput
+				return m, func() tea.Msg { return nil }
 			}
 
-			_ = ts.Branch(targetID)
-			m.appCtrl.ClearMessages()
-
-			// If it was a user message, populate the input with the text.
-			if msg.IsUser && msg.UserText != "" {
-				if ic, ok := m.input.(*InputComponent); ok {
-					ic.textarea.SetValue(msg.UserText)
-					ic.textarea.CursorEnd()
-				}
-			}
-
-			cmds = append(cmds, m.printSystemMessage(
-				fmt.Sprintf("Navigated to branch point. %s",
-					func() string {
-						if msg.IsUser {
-							return "Edit and resubmit to create a new branch."
-						}
-						return "Continue from this point."
-					}())))
+			cmds = append(cmds, m.performFork(targetID, msg.IsUser, msg.UserText))
 		}
 		m.treeSelector = nil
 		m.state = stateInput
@@ -901,12 +911,20 @@ func (m *AppModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 		}
 
 		// Regular prompt — forward to the app layer.
+		// Preprocess @file references: expand them into XML-wrapped file
+		// content before sending to the agent. The display text (shown in
+		// scrollback) uses the original user text so the UI stays clean.
+		processedText := msg.Text
+		if m.cwd != "" {
+			processedText = ProcessFileAttachments(msg.Text, m.cwd)
+		}
+
 		if m.appCtrl != nil {
 			// Run returns the queue depth: >0 means the prompt was queued
 			// (agent is busy). We update queuedMessages directly here
 			// instead of relying on an event from prog.Send(), which would
 			// deadlock when called synchronously from within Update().
-			if qLen := m.appCtrl.Run(msg.Text); qLen > 0 {
+			if qLen := m.appCtrl.Run(processedText); qLen > 0 {
 				// Queued: anchor the message text above the input with a
 				// "queued" badge. It will be printed to scrollback when
 				// the agent picks it up (on QueueUpdatedEvent).
@@ -1163,6 +1181,24 @@ func (m *AppModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			cmds = append(cmds, m.printSystemMessage(msg.output))
 		}
 
+	case beforeSessionSwitchResultMsg:
+		// Async before-session-switch hook completed. Proceed with the
+		// session reset if the hook did not cancel.
+		if msg.cancelled {
+			cmds = append(cmds, m.printSystemMessage(msg.reason))
+		} else {
+			cmds = append(cmds, m.performNewSession())
+		}
+
+	case beforeForkResultMsg:
+		// Async before-fork hook completed. Proceed with the fork if the
+		// hook did not cancel.
+		if msg.cancelled {
+			cmds = append(cmds, m.printSystemMessage(msg.reason))
+		} else {
+			cmds = append(cmds, m.performFork(msg.targetID, msg.isUser, msg.userText))
+		}
+
 	case app.ExtensionPrintEvent:
 		// Extension output — route through styled renderers when a level is set.
 		switch msg.Level {
@@ -2004,13 +2040,28 @@ func (m *AppModel) handleForkCommand() tea.Cmd {
 
 // handleNewCommand starts a fresh session by resetting the tree leaf.
 func (m *AppModel) handleNewCommand() tea.Cmd {
-	// Emit before-session-switch event — extensions can cancel.
+	// Emit before-session-switch event in a goroutine so that extension
+	// handlers can call blocking operations (e.g. ctx.PromptConfirm) without
+	// deadlocking the BubbleTea event loop.
 	if m.emitBeforeSessionSwitch != nil {
-		if cancelled, reason := m.emitBeforeSessionSwitch("new"); cancelled {
-			return m.printSystemMessage(reason)
-		}
+		emit := m.emitBeforeSessionSwitch
+		ctrl := m.appCtrl
+		go func() {
+			cancelled, reason := emit("new")
+			ctrl.SendEvent(beforeSessionSwitchResultMsg{
+				cancelled: cancelled,
+				reason:    reason,
+			})
+		}()
+		return func() tea.Msg { return nil }
 	}
 
+	return m.performNewSession()
+}
+
+// performNewSession performs the actual session reset. Called either directly
+// (when no before-hook exists) or after the async hook completes.
+func (m *AppModel) performNewSession() tea.Cmd {
 	ts := m.appCtrl.GetTreeSession()
 	if ts == nil {
 		// No tree session — just clear messages.
@@ -2027,6 +2078,35 @@ func (m *AppModel) handleNewCommand() tea.Cmd {
 	return m.printSystemMessage("New branch started. Previous conversation is preserved in the tree.")
 }
 
+// performFork performs the actual tree branch. Called either directly (when no
+// before-hook exists) or after the async before-fork hook completes.
+func (m *AppModel) performFork(targetID string, isUser bool, userText string) tea.Cmd {
+	ts := m.appCtrl.GetTreeSession()
+	if ts == nil {
+		return m.printSystemMessage("No tree session active.")
+	}
+
+	_ = ts.Branch(targetID)
+	m.appCtrl.ClearMessages()
+
+	// If it was a user message, populate the input with the text.
+	if isUser && userText != "" {
+		if ic, ok := m.input.(*InputComponent); ok {
+			ic.textarea.SetValue(userText)
+			ic.textarea.CursorEnd()
+		}
+	}
+
+	return m.printSystemMessage(
+		fmt.Sprintf("Navigated to branch point. %s",
+			func() string {
+				if isUser {
+					return "Edit and resubmit to create a new branch."
+				}
+				return "Continue from this point."
+			}()))
+}
+
 // handleNameCommand sets a display name for the current session.
 func (m *AppModel) handleNameCommand() tea.Cmd {
 	ts := m.appCtrl.GetTreeSession()
@@ -2100,6 +2180,26 @@ type extensionCmdResultMsg struct {
 	err    error
 }
 
+// beforeSessionSwitchResultMsg carries the result of an asynchronously
+// executed before-session-switch hook. The hook runs in a goroutine so that
+// blocking operations like ctx.PromptConfirm() do not deadlock the TUI.
+type beforeSessionSwitchResultMsg struct {
+	cancelled bool
+	reason    string
+}
+
+// beforeForkResultMsg carries the result of an asynchronously executed
+// before-fork hook along with the fork context needed to complete the
+// operation if the hook allows it.
+type beforeForkResultMsg struct {
+	cancelled bool
+	reason    string
+	// Fork context — preserved so the operation can proceed after the hook.
+	targetID string
+	isUser   bool
+	userText string
+}
+
 // updatePromptState handles all messages while the prompt overlay is active.
 // It routes keys to the prompt overlay, detects completion/cancellation, and
 // restores the previous state when done.

pkg/kit/extensions_bridge.go

@@ -1,6 +1,8 @@
 package kit
 
 import (
+	"strings"
+
 	"charm.land/fantasy"
 	"github.com/mark3labs/kit/internal/extensions"
 )
@@ -109,16 +111,16 @@ func (m *Kit) bridgeExtensions(runner *extensions.Runner) {
 			extMsgs := make([]extensions.ContextMessage, len(h.Messages))
 			for i, msg := range h.Messages {
 				// Extract text from content parts.
-				var text string
+				var text strings.Builder
 				for _, part := range msg.Content {
 					if tp, ok := part.(fantasy.TextPart); ok {
-						text += tp.Text
+						text.WriteString(tp.Text)
 					}
 				}
 				extMsgs[i] = extensions.ContextMessage{
 					Index:   i,
 					Role:    string(msg.Role),
-					Content: text,
+					Content: text.String(),
 				}
 			}
 

pkg/kit/kit.go

@@ -321,24 +321,24 @@ func (m *Kit) GetSessionMessages() []extensions.SessionMessage {
 			continue
 		}
 		// Flatten content parts into a single text string.
-		var content string
+		var content strings.Builder
 		for _, p := range msg.Parts {
 			switch pt := p.(type) {
 			case message.TextContent:
-				content += pt.Text
+				content.WriteString(pt.Text)
 			case message.ReasoningContent:
-				content += pt.Thinking
+				content.WriteString(pt.Thinking)
 			case message.ToolCall:
-				content += fmt.Sprintf("[tool_call: %s(%s)]", pt.Name, pt.Input)
+				fmt.Fprintf(&content, "[tool_call: %s(%s)]", pt.Name, pt.Input)
 			case message.ToolResult:
-				content += fmt.Sprintf("[tool_result: %s]", pt.Content)
+				fmt.Fprintf(&content, "[tool_result: %s]", pt.Content)
 			}
 		}
 		msgs = append(msgs, extensions.SessionMessage{
 			ID:        me.ID,
 			ParentID:  me.ParentID,
 			Role:      string(msg.Role),
-			Content:   content,
+			Content:   content.String(),
 			Model:     msg.Model,
 			Provider:  msg.Provider,
 			Timestamp: me.Timestamp.Format("2006-01-02T15:04:05Z07:00"),