refactor tmuxedit to Agent interface with cursor/claude/config implementations

Replace monolithic AgentConfig struct with an Agent interface backed by
baseAgent defaults and separate implementations for cursor (box-drawing
extraction, bulk backspace clearing) and claude (section-scoped extraction
with continuation lines, vim clearing). Simple agents (amp, aider) and
user-defined agents use configAgent with baseAgent defaults.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

16 files changed, 1354 insertions, 755 deletions

diff --git a/docs/tmux.md b/docs/tmux.md
index b6d4b68..ae84ce2 100644
--- a/docs/tmux.md
+++ b/docs/tmux.md
@@ -90,3 +90,7 @@ bind e run-shell -b "hexai-tmux-edit --pane '#{pane_id}'"
 Then press `prefix + e` in any pane running an AI agent. Hexai auto-detects the agent, extracts any existing prompt text, and pre-fills the editor. After saving and closing, the edited text is sent back to the agent's pane.
 
 See the [configuration guide](configuration.md) for customizing popup dimensions and agent patterns, or the [usage guide](usage.md) for the full workflow description.
+
+**Vim mode recommended**: For best results, run both Cursor Agent and Claude Code in vim mode. Claude Code's `C-u` clear relies on readline/vim insert-mode behavior, and Cursor's prompt clearing works most reliably in its default input mode. The popup editor uses `$EDITOR` (or `$HEXAI_EDITOR`), so your normal vim/neovim setup is used for composing prompts.
+
+**Note**: Agent detection and prompt extraction rely on regex patterns matched against each agent's terminal UI (box-drawing characters, prompt symbols, status text). When agents update their TUI layout, these patterns may need adjustment. You can override patterns per-agent in `[[tmux_edit.agents]]` config without code changes -- see the [configuration guide](configuration.md).
diff --git a/internal/appconfig/config.go b/internal/appconfig/config.go
index b21a4de..63b5ea5 100644
--- a/internal/appconfig/config.go
+++ b/internal/appconfig/config.go
@@ -141,15 +141,16 @@ type CustomAction struct {
 // TmuxEditAgentCfg describes an AI agent's detection and interaction patterns
 // for the tmux popup editor (hexai-tmux-edit).
 type TmuxEditAgentCfg struct {
-	Name          string
-	DisplayName   string
-	DetectPattern string
-	PromptPattern string
-	StripPatterns []string
-	ClearFirst    *bool
-	ClearKeys     string
-	NewlineKeys   string
-	SubmitKeys    string
+	Name           string
+	DisplayName    string
+	DetectPattern  string
+	SectionPattern string
+	PromptPattern  string
+	StripPatterns  []string
+	ClearFirst     *bool
+	ClearKeys      string
+	NewlineKeys    string
+	SubmitKeys     string
 }
 
 // Constructor: defaults for App (kept first among functions)
@@ -364,15 +365,16 @@ type sectionTmuxEdit struct {
 
 // sectionTmuxEditAgent defines detection and interaction patterns for one AI agent.
 type sectionTmuxEditAgent struct {
-	Name          string   `toml:"name"`
-	DisplayName   string   `toml:"display_name"`
-	DetectPattern string   `toml:"detect_pattern"`
-	PromptPattern string   `toml:"prompt_pattern"`
-	StripPatterns []string `toml:"strip_patterns"`
-	ClearFirst    *bool    `toml:"clear_first"`
-	ClearKeys     string   `toml:"clear_keys"`
-	NewlineKeys   string   `toml:"newline_keys"`
-	SubmitKeys    string   `toml:"submit_keys"`
+	Name           string   `toml:"name"`
+	DisplayName    string   `toml:"display_name"`
+	DetectPattern  string   `toml:"detect_pattern"`
+	SectionPattern string   `toml:"section_pattern"`
+	PromptPattern  string   `toml:"prompt_pattern"`
+	StripPatterns  []string `toml:"strip_patterns"`
+	ClearFirst     *bool    `toml:"clear_first"`
+	ClearKeys      string   `toml:"clear_keys"`
+	NewlineKeys    string   `toml:"newline_keys"`
+	SubmitKeys     string   `toml:"submit_keys"`
 }
 
 type sectionOpenAI struct {
@@ -724,15 +726,16 @@ func (fc *fileConfig) applyTmuxEdit(out *App) {
 			continue
 		}
 		out.TmuxEditAgents = append(out.TmuxEditAgents, TmuxEditAgentCfg{
-			Name:          strings.TrimSpace(a.Name),
-			DisplayName:   strings.TrimSpace(a.DisplayName),
-			DetectPattern: strings.TrimSpace(a.DetectPattern),
-			PromptPattern: strings.TrimSpace(a.PromptPattern),
-			StripPatterns: a.StripPatterns,
-			ClearFirst:    a.ClearFirst,
-			ClearKeys:     strings.TrimSpace(a.ClearKeys),
-			NewlineKeys:   strings.TrimSpace(a.NewlineKeys),
-			SubmitKeys:    strings.TrimSpace(a.SubmitKeys),
+			Name:           strings.TrimSpace(a.Name),
+			DisplayName:    strings.TrimSpace(a.DisplayName),
+			DetectPattern:  strings.TrimSpace(a.DetectPattern),
+			SectionPattern: strings.TrimSpace(a.SectionPattern),
+			PromptPattern:  strings.TrimSpace(a.PromptPattern),
+			StripPatterns:  a.StripPatterns,
+			ClearFirst:     a.ClearFirst,
+			ClearKeys:      strings.TrimSpace(a.ClearKeys),
+			NewlineKeys:    strings.TrimSpace(a.NewlineKeys),
+			SubmitKeys:     strings.TrimSpace(a.SubmitKeys),
 		})
 	}
 }
diff --git a/internal/tmuxedit/agent.go b/internal/tmuxedit/agent.go
index 7be38ed..313907a 100644
--- a/internal/tmuxedit/agent.go
+++ b/internal/tmuxedit/agent.go
@@ -1,182 +1,121 @@
 // Package tmuxedit implements a tmux popup editor for composing AI agent prompts.
-// agent.go defines agent detection, prompt extraction, and noise stripping.
+// agent.go defines the Agent interface, the baseAgent struct with default
+// implementations, and agent detection/resolution helpers.
 package tmuxedit
 
 import (
 	"regexp"
 	"strings"
-
-	"codeberg.org/snonux/hexai/internal/appconfig"
 )
 
-// AgentConfig describes how to detect and interact with a specific AI agent
-// running in a tmux pane. All behavior is driven by regex patterns so new
-// agents can be added via config without code changes.
-type AgentConfig struct {
-	Name          string   // short key: "claude", "cursor", "amp"
-	DisplayName   string   // human-readable: "Claude Code"
-	DetectPattern string   // regex matched against pane content for auto-detection
-	PromptPattern string   // regex with capture group (1) to extract current prompt text
-	StripPatterns []string // substrings removed from extracted text
-	ClearFirst    bool     // whether to clear existing input before sending
-	ClearKeys     string   // tmux key sequence to clear input (e.g. "C-u")
-	NewlineKeys   string   // tmux key to insert a newline (e.g. "S-Enter")
-	SubmitKeys    string   // tmux key to submit the prompt (e.g. "Enter")
+// Agent defines how to interact with a specific AI agent in a tmux pane.
+// Each implementation encapsulates its own detection, extraction, clearing,
+// and sending logic since agents differ fundamentally in their UI structure.
+type Agent interface {
+	Name() string
+	DisplayName() string
+	Detect(paneContent string) bool
+	ExtractPrompt(paneContent string) string
+	ClearInput(paneID string) error
+	SendText(paneID, text string) error
 }
 
-// builtinAgents returns the default set of agent configurations. Order
-// matters: agents with distinctive UI elements (box-drawing, etc.) are
-// checked first to avoid false positives from model names like "Claude
-// 4.5 Sonnet" appearing in other agents' panes. Overridden/extended by
-// user config in [tmux_edit.agents].
-func builtinAgents() []AgentConfig {
-	return []AgentConfig{
-		{
-			// Cursor Agent uses a distinctive box-drawing │ → prompt │ UI.
-			// Detect by the box structure or "/ commands" footer. Checked
-			// first because cursor panes show model names like "Claude 4.5".
-			// Clear uses End + bulk backspace to delete all existing text.
-			// The *200 suffix sends 200 backspaces via tmux send-keys -N.
-			Name:          "cursor",
-			DisplayName:   "Cursor",
-			DetectPattern: `(│\s*→|/ commands · @ files)`,
-			PromptPattern: `(?m)│\s*→?\s*(.+?)\s*│\s*$`,
-			StripPatterns: []string{"INSERT", "Add a follow-up", "ctrl+c to stop"},
-			ClearFirst:    true,
-			ClearKeys:     "End BSpace*200",
-			NewlineKeys:   "S-Enter",
-			SubmitKeys:    "Enter",
-		},
-		{
-			// Claude Code uses ❯ prompt between ──── horizontal rules.
-			// Detect by the ❯ prompt or explicit "claude code" banner.
-			Name:          "claude",
-			DisplayName:   "Claude Code",
-			DetectPattern: `(❯|claude code|anthropic)`,
-			PromptPattern: `(?m)❯\s*(.+)$`,
-			ClearFirst:    true,
-			ClearKeys:     "C-u",
-			NewlineKeys:   "S-Enter",
-			SubmitKeys:    "Enter",
-		},
-		{
-			Name:          "amp",
-			DisplayName:   "Amp",
-			DetectPattern: `(?i)(amp|sourcegraph)`,
-			PromptPattern: `(?m)>\s*(.+)$`,
-			ClearFirst:    true,
-			ClearKeys:     "C-u",
-			NewlineKeys:   "S-Enter",
-			SubmitKeys:    "Enter",
-		},
-		{
-			Name:          "aider",
-			DisplayName:   "Aider",
-			DetectPattern: `(?i)aider`,
-			PromptPattern: `(?m)>\s*(.+)$`,
-			ClearFirst:    true,
-			ClearKeys:     "C-u",
-			NewlineKeys:   "",
-			SubmitKeys:    "Enter",
-		},
-	}
+// Configurable provides access to a baseAgent's fields for config merging.
+// Agent implementations that embed baseAgent automatically satisfy this.
+type Configurable interface {
+	Base() *baseAgent
 }
 
-// genericAgent returns a fallback agent with no detection or prompt extraction.
-// The user gets a blank editor and text is sent verbatim.
-func genericAgent() AgentConfig {
-	return AgentConfig{
-		Name:        "generic",
-		DisplayName: "Generic",
-		NewlineKeys: "",
-		SubmitKeys:  "Enter",
-	}
+// baseAgent holds configurable fields and provides default implementations
+// of the Agent interface. Specialized agents (cursor, claude) embed baseAgent
+// and override methods where behavior differs from the defaults.
+type baseAgent struct {
+	name          string
+	displayName   string
+	detectPattern string
+	sectionPat    string   // optional regex to delimit the prompt area
+	promptPat     string   // regex with capture group (1) for prompt text
+	stripPatterns []string // substrings removed from extracted text
+	clearFirst    bool     // whether to clear existing input before sending
+	clearKeys     string   // tmux key sequence to clear input
+	newlineKeys   string   // tmux key to insert a newline
+	submitKeys    string   // tmux key to submit the prompt
 }
 
-// resolveAgents merges built-in agent defaults with user-provided overrides
-// from config. Agents are matched by name (case-insensitive); user config
-// wins field-by-field over builtins.
-func resolveAgents(cfgAgents []appconfig.TmuxEditAgentCfg) []AgentConfig {
-	agents := builtinAgents()
-	for _, ca := range cfgAgents {
-		merged := false
-		for i, a := range agents {
-			if !strings.EqualFold(a.Name, ca.Name) {
-				continue
-			}
-			agents[i] = mergeAgentConfig(a, ca)
-			merged = true
-			break
-		}
-		if !merged {
-			agents = append(agents, agentFromConfig(ca))
-		}
-	}
-	return agents
-}
+// Base returns a pointer to the baseAgent for config merging.
+func (b *baseAgent) Base() *baseAgent { return b }
 
-// mergeAgentConfig overrides fields in base with non-zero values from cfg.
-func mergeAgentConfig(base AgentConfig, cfg appconfig.TmuxEditAgentCfg) AgentConfig {
-	if s := strings.TrimSpace(cfg.DisplayName); s != "" {
-		base.DisplayName = s
-	}
-	if s := strings.TrimSpace(cfg.DetectPattern); s != "" {
-		base.DetectPattern = s
-	}
-	if s := strings.TrimSpace(cfg.PromptPattern); s != "" {
-		base.PromptPattern = s
+// Name returns the agent's short identifier (e.g. "claude", "cursor").
+func (b *baseAgent) Name() string { return b.name }
+
+// DisplayName returns the agent's human-readable name.
+func (b *baseAgent) DisplayName() string { return b.displayName }
+
+// Detect checks whether the pane content matches this agent's detection
+// pattern. Returns false if no pattern is set or the regex is invalid.
+func (b *baseAgent) Detect(paneContent string) bool {
+	if b.detectPattern == "" {
+		return false
 	}
-	if len(cfg.StripPatterns) > 0 {
-		base.StripPatterns = cfg.StripPatterns
+	re, err := regexp.Compile(b.detectPattern)
+	if err != nil {
+		return false
 	}
-	if cfg.ClearFirst != nil {
-		base.ClearFirst = *cfg.ClearFirst
+	return re.MatchString(paneContent)
+}
+
+// ExtractPrompt uses the agent's prompt pattern to extract the current prompt
+// text from pane content. If sectionPat is set, extraction is scoped to the
+// last section between two delimiter lines and all matches are joined.
+// Without sectionPat, the last contiguous group of matched lines is used.
+// Returns empty string if no pattern or no match.
+func (b *baseAgent) ExtractPrompt(paneContent string) string {
+	if b.promptPat == "" {
+		return ""
 	}
-	if s := strings.TrimSpace(cfg.ClearKeys); s != "" {
-		base.ClearKeys = s
+	re, err := regexp.Compile(b.promptPat)
+	if err != nil {
+		return ""
 	}
-	if s := strings.TrimSpace(cfg.NewlineKeys); s != "" {
-		base.NewlineKeys = s
+	scoped := b.sectionPat != ""
+	content := scopeToLastSection(paneContent, b.sectionPat)
+	allMatches := matchPromptLines(re, content)
+	if len(allMatches) == 0 {
+		return ""
 	}
-	if s := strings.TrimSpace(cfg.SubmitKeys); s != "" {
-		base.SubmitKeys = s
+	if scoped {
+		return joinAllMatches(allMatches, b.stripPatterns)
 	}
-	return base
+	return joinLastContiguousBlock(allMatches, b.stripPatterns)
 }
 
-// agentFromConfig creates a new AgentConfig from a user config entry.
-func agentFromConfig(cfg appconfig.TmuxEditAgentCfg) AgentConfig {
-	a := AgentConfig{
-		Name:          strings.TrimSpace(cfg.Name),
-		DisplayName:   strings.TrimSpace(cfg.DisplayName),
-		DetectPattern: strings.TrimSpace(cfg.DetectPattern),
-		PromptPattern: strings.TrimSpace(cfg.PromptPattern),
-		StripPatterns: cfg.StripPatterns,
-		ClearKeys:     strings.TrimSpace(cfg.ClearKeys),
-		NewlineKeys:   strings.TrimSpace(cfg.NewlineKeys),
-		SubmitKeys:    strings.TrimSpace(cfg.SubmitKeys),
+// ClearInput clears existing input in the pane using the configured key
+// sequence. Skipped if clearFirst is false or clearKeys is empty.
+func (b *baseAgent) ClearInput(paneID string) error {
+	if !b.clearFirst || b.clearKeys == "" {
+		return nil
 	}
-	if cfg.ClearFirst != nil {
-		a.ClearFirst = *cfg.ClearFirst
+	if err := sendClearSequence(paneID, b.clearKeys); err != nil {
+		return err
 	}
-	if a.DisplayName == "" {
-		a.DisplayName = a.Name
+	sleepAfterClear()
+	return nil
+}
+
+// SendText sends the given text to the target pane line-by-line, using the
+// agent's newline key between lines.
+func (b *baseAgent) SendText(paneID, text string) error {
+	if strings.TrimSpace(text) == "" {
+		return nil
 	}
-	return a
+	return sendLines(paneID, text, b.newlineKeys)
 }
 
-// detectAgent tries each agent's DetectPattern against pane content.
+// detectAgent tries each agent's Detect method against pane content.
 // First match wins. Returns genericAgent() if no agent matches.
-func detectAgent(paneContent string, agents []AgentConfig) AgentConfig {
+func detectAgent(paneContent string, agents []Agent) Agent {
 	for _, a := range agents {
-		if a.DetectPattern == "" {
-			continue
-		}
-		re, err := regexp.Compile(a.DetectPattern)
-		if err != nil {
-			continue
-		}
-		if re.MatchString(paneContent) {
+		if a.Detect(paneContent) {
 			return a
 		}
 	}
@@ -185,80 +124,11 @@ func detectAgent(paneContent string, agents []AgentConfig) AgentConfig {
 
 // findAgentByName returns the agent with the given name (case-insensitive),
 // falling back to genericAgent() if not found.
-func findAgentByName(name string, agents []AgentConfig) AgentConfig {
+func findAgentByName(name string, agents []Agent) Agent {
 	for _, a := range agents {
-		if strings.EqualFold(a.Name, name) {
+		if strings.EqualFold(a.Name(), name) {
 			return a
 		}
 	}
 	return genericAgent()
 }
-
-// extractPrompt uses the agent's PromptPattern to extract the current prompt
-// text from pane content. For multi-line prompts (e.g. cursor's box-drawing
-// │...│ UI) it takes only the last contiguous group of matched lines, which
-// avoids picking up command-review or dialog boxes that use the same border
-// characters. Returns empty string if no pattern or no match.
-func extractPrompt(paneContent string, agent AgentConfig) string {
-	if agent.PromptPattern == "" {
-		return ""
-	}
-	re, err := regexp.Compile(agent.PromptPattern)
-	if err != nil {
-		return ""
-	}
-	allMatches := matchPromptLines(re, paneContent)
-	if len(allMatches) == 0 {
-		return ""
-	}
-	return joinLastContiguousBlock(allMatches, agent.StripPatterns)
-}
-
-// promptMatch holds a regex match result with its line number in the pane.
-type promptMatch struct {
-	lineNum int
-	text    string // capture group 1
-}
-
-// matchPromptLines runs the prompt regex against each pane line, returning
-// matches with their line numbers for contiguity analysis.
-func matchPromptLines(re *regexp.Regexp, paneContent string) []promptMatch {
-	paneLines := strings.Split(paneContent, "\n")
-	var matches []promptMatch
-	for i, line := range paneLines {
-		m := re.FindStringSubmatch(line)
-		if len(m) >= 2 {
-			matches = append(matches, promptMatch{lineNum: i, text: m[1]})
-		}
-	}
-	return matches
-}
-
-// joinLastContiguousBlock takes the last group of matches on consecutive line
-// numbers, strips noise from each, and joins the non-empty results with
-// newlines. This ensures that only the bottom-most box (the input prompt)
-// is captured when multiple box-drawing sections exist in the pane.
-func joinLastContiguousBlock(matches []promptMatch, strips []string) string {
-	last := len(matches) - 1
-	start := last
-	for start > 0 && matches[start].lineNum-matches[start-1].lineNum == 1 {
-		start--
-	}
-	var lines []string
-	for i := start; i <= last; i++ {
-		line := stripNoise(matches[i].text, strips)
-		if line != "" {
-			lines = append(lines, line)
-		}
-	}
-	return strings.Join(lines, "\n")
-}
-
-// stripNoise removes each of the agent's StripPatterns from text and trims
-// whitespace.
-func stripNoise(text string, patterns []string) string {
-	for _, p := range patterns {
-		text = strings.ReplaceAll(text, p, "")
-	}
-	return strings.TrimSpace(text)
-}
diff --git a/internal/tmuxedit/agent_test.go b/internal/tmuxedit/agent_test.go
index 7ad1274..3673d70 100644
--- a/internal/tmuxedit/agent_test.go
+++ b/internal/tmuxedit/agent_test.go
@@ -2,12 +2,8 @@ package tmuxedit
 
 import (
 	"testing"
-
-	"codeberg.org/snonux/hexai/internal/appconfig"
 )
 
-func boolP(b bool) *bool { return &b }
-
 func TestDetectAgent(t *testing.T) {
 	agents := builtinAgents()
 	tests := []struct {
@@ -28,8 +24,8 @@ func TestDetectAgent(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			got := detectAgent(tt.content, agents)
-			if got.Name != tt.want {
-				t.Errorf("detectAgent() = %q, want %q", got.Name, tt.want)
+			if got.Name() != tt.want {
+				t.Errorf("detectAgent() = %q, want %q", got.Name(), tt.want)
 			}
 		})
 	}
@@ -50,260 +46,74 @@ func TestFindAgentByName(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			got := findAgentByName(tt.name, agents)
-			if got.Name != tt.want {
-				t.Errorf("findAgentByName(%q) = %q, want %q", tt.name, got.Name, tt.want)
-			}
-		})
-	}
-}
-
-func TestExtractPrompt(t *testing.T) {
-	tests := []struct {
-		name    string
-		content string
-		agent   AgentConfig
-		want    string
-	}{
-		{
-			name:    "claude prompt",
-			content: "────\n❯ hello world\n────",
-			agent:   builtinAgents()[1], // claude
-			want:    "hello world",
-		},
-		{
-			name:    "cursor prompt with box and arrow",
-			content: "Cursor Agent\n │ → fix the bug                    INSERT │",
-			agent:   builtinAgents()[0], // cursor
-			want:    "fix the bug",
-		},
-		{
-			name:    "cursor prompt without arrow",
-			content: "Cursor Agent\n │ fix the bug              │",
-			agent:   builtinAgents()[0], // cursor
-			want:    "fix the bug",
-		},
-		{
-			name:    "cursor prompt strips follow-up",
-			content: "Cursor\n │ → Add a follow-up            │",
-			agent:   builtinAgents()[0], // cursor
-			want:    "",
-		},
-		{
-			name:    "cursor multi-line prompt",
-			content: " │ → first line of prompt                    │\n │   second line here                        │\n │   third line end                          │",
-			agent:   builtinAgents()[0], // cursor
-			want:    "first line of prompt\nsecond line here\nthird line end",
-		},
-		{
-			name:    "cursor multi-line with noise",
-			content: " │ → fix the bug INSERT                     │\n │   also refactor tests                     │",
-			agent:   builtinAgents()[0], // cursor
-			want:    "fix the bug\nalso refactor tests",
-		},
-		{
-			name: "cursor multi-box takes last box only",
-			content: " ┌──────────────┐\n" +
-				" │ $ git push    │\n" +
-				" └──────────────┘\n" +
-				" ┌──────────────┐\n" +
-				" │ Run command?  │\n" +
-				" │ → Yes (enter) │\n" +
-				" │   No (esc)    │\n" +
-				" └──────────────┘\n" +
-				" ┌──────────────┐\n" +
-				" │ → hello world │\n" +
-				" └──────────────┘\n",
-			agent: builtinAgents()[0], // cursor
-			want:  "hello world",
-		},
-		{
-			name: "cursor multi-box multi-line prompt",
-			content: " ┌──────────────┐\n" +
-				" │ $ git push    │\n" +
-				" └──────────────┘\n" +
-				" ┌──────────────┐\n" +
-				" │ → first line  │\n" +
-				" │   second line │\n" +
-				" │   third line  │\n" +
-				" └──────────────┘\n",
-			agent: builtinAgents()[0], // cursor
-			want:  "first line\nsecond line\nthird line",
-		},
-		{
-			name:    "no pattern",
-			content: "some text",
-			agent:   genericAgent(),
-			want:    "",
-		},
-		{
-			name:    "no match",
-			content: "no prompt here",
-			agent:   builtinAgents()[1], // claude
-			want:    "",
-		},
-		{
-			name:    "invalid regex",
-			content: "> test",
-			agent:   AgentConfig{PromptPattern: "[invalid"},
-			want:    "",
-		},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got := extractPrompt(tt.content, tt.agent)
-			if got != tt.want {
-				t.Errorf("extractPrompt() = %q, want %q", got, tt.want)
+			if got.Name() != tt.want {
+				t.Errorf("findAgentByName(%q) = %q, want %q", tt.name, got.Name(), tt.want)
 			}
 		})
 	}
 }
 
-func TestStripNoise(t *testing.T) {
-	tests := []struct {
-		name     string
-		text     string
-		patterns []string
-		want     string
-	}{
-		{"no patterns", "hello world", nil, "hello world"},
-		{"strip INSERT", "fix the bug INSERT", []string{"INSERT"}, "fix the bug"},
-		{"strip multiple", "INSERT fix the bug Add a follow-up", []string{"INSERT", "Add a follow-up"}, "fix the bug"},
-		{"strip to empty", "INSERT", []string{"INSERT"}, ""},
+func TestDetectAgent_InvalidRegex(t *testing.T) {
+	agents := []Agent{
+		&configAgent{baseAgent{name: "bad", detectPattern: "[invalid"}},
 	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			got := stripNoise(tt.text, tt.patterns)
-			if got != tt.want {
-				t.Errorf("stripNoise() = %q, want %q", got, tt.want)
-			}
-		})
+	got := detectAgent("anything", agents)
+	if got.Name() != "generic" {
+		t.Errorf("expected generic fallback for invalid regex, got %q", got.Name())
 	}
 }
 
-func TestResolveAgents_MergeOverride(t *testing.T) {
-	cfgAgents := []appconfig.TmuxEditAgentCfg{
-		{
-			Name:        "claude",
-			DisplayName: "My Claude",
-			ClearFirst:  boolP(false),
-		},
-	}
-	agents := resolveAgents(cfgAgents)
-	var claude AgentConfig
-	for _, a := range agents {
-		if a.Name == "claude" {
-			claude = a
-			break
-		}
-	}
-	if claude.DisplayName != "My Claude" {
-		t.Errorf("DisplayName = %q, want My Claude", claude.DisplayName)
-	}
-	if claude.ClearFirst {
-		t.Error("ClearFirst should be false after override")
-	}
-	// DetectPattern should be preserved from builtin
-	if claude.DetectPattern == "" {
-		t.Error("DetectPattern should be preserved from builtin")
+func TestGenericAgent(t *testing.T) {
+	g := genericAgent()
+	if g.Name() != "generic" {
+		t.Errorf("Name = %q, want generic", g.Name())
 	}
 }
 
-func TestResolveAgents_MergeAllFields(t *testing.T) {
-	cfgAgents := []appconfig.TmuxEditAgentCfg{
-		{
-			Name:          "claude",
-			DisplayName:   "Custom Claude",
-			DetectPattern: "(?i)custom-claude",
-			PromptPattern: `>\s+(.*)$`,
-			StripPatterns: []string{"NOISE"},
-			ClearFirst:    boolP(true),
-			ClearKeys:     "C-k",
-			NewlineKeys:   "C-Enter",
-			SubmitKeys:    "C-m",
-		},
-	}
-	agents := resolveAgents(cfgAgents)
-	var a AgentConfig
-	for _, ag := range agents {
-		if ag.Name == "claude" {
-			a = ag
-			break
-		}
-	}
-	if a.DetectPattern != "(?i)custom-claude" {
-		t.Errorf("DetectPattern = %q", a.DetectPattern)
-	}
-	if a.PromptPattern != `>\s+(.*)$` {
-		t.Errorf("PromptPattern = %q", a.PromptPattern)
-	}
-	if len(a.StripPatterns) != 1 || a.StripPatterns[0] != "NOISE" {
-		t.Errorf("StripPatterns = %v", a.StripPatterns)
-	}
-	if a.ClearKeys != "C-k" {
-		t.Errorf("ClearKeys = %q", a.ClearKeys)
-	}
-	if a.NewlineKeys != "C-Enter" {
-		t.Errorf("NewlineKeys = %q", a.NewlineKeys)
-	}
-	if a.SubmitKeys != "C-m" {
-		t.Errorf("SubmitKeys = %q", a.SubmitKeys)
+func TestBaseAgent_SendText_Empty(t *testing.T) {
+	b := &baseAgent{newlineKeys: "S-Enter"}
+	err := b.SendText("%1", "")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
 	}
 }
 
-func TestResolveAgents_AddNew(t *testing.T) {
-	cfgAgents := []appconfig.TmuxEditAgentCfg{
-		{
-			Name:          "custom",
-			DisplayName:   "Custom Agent",
-			DetectPattern: "(?i)custom",
-			PromptPattern: `>\s*(.+)$`,
-			ClearFirst:    boolP(true),
-		},
-	}
-	agents := resolveAgents(cfgAgents)
-	found := false
-	for _, a := range agents {
-		if a.Name == "custom" {
-			found = true
-			if a.DisplayName != "Custom Agent" {
-				t.Errorf("DisplayName = %q, want Custom Agent", a.DisplayName)
-			}
-			if !a.ClearFirst {
-				t.Error("ClearFirst should be true")
-			}
-		}
-	}
-	if !found {
-		t.Error("custom agent not found in resolved agents")
+func TestBaseAgent_ClearInput_Disabled(t *testing.T) {
+	b := &baseAgent{clearFirst: false, clearKeys: "C-u"}
+	err := b.ClearInput("%1")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
 	}
 }
 
-func TestAgentFromConfig_DefaultDisplayName(t *testing.T) {
-	cfg := appconfig.TmuxEditAgentCfg{
-		Name: "test",
-	}
-	a := agentFromConfig(cfg)
-	if a.DisplayName != "test" {
-		t.Errorf("DisplayName = %q, want test (defaulted from Name)", a.DisplayName)
+func TestBaseAgent_ExtractPrompt_NoPattern(t *testing.T) {
+	b := &baseAgent{}
+	got := b.ExtractPrompt("some content")
+	if got != "" {
+		t.Errorf("expected empty, got %q", got)
 	}
 }
 
-func TestDetectAgent_InvalidRegex(t *testing.T) {
-	agents := []AgentConfig{
-		{Name: "bad", DetectPattern: "[invalid"},
-	}
-	got := detectAgent("anything", agents)
-	if got.Name != "generic" {
-		t.Errorf("expected generic fallback for invalid regex, got %q", got.Name)
+func TestBaseAgent_ExtractPrompt_InvalidRegex(t *testing.T) {
+	b := &baseAgent{promptPat: "[invalid"}
+	got := b.ExtractPrompt("> test")
+	if got != "" {
+		t.Errorf("expected empty for invalid regex, got %q", got)
 	}
 }
 
-func TestGenericAgent(t *testing.T) {
-	g := genericAgent()
-	if g.Name != "generic" {
-		t.Errorf("Name = %q, want generic", g.Name)
-	}
-	if g.SubmitKeys != "Enter" {
-		t.Errorf("SubmitKeys = %q, want Enter", g.SubmitKeys)
+func TestConfigurable_Interface(t *testing.T) {
+	// Verify that all agent types implement Configurable
+	agents := builtinAgents()
+	for _, a := range agents {
+		c, ok := a.(Configurable)
+		if !ok {
+			t.Errorf("agent %q does not implement Configurable", a.Name())
+			continue
+		}
+		base := c.Base()
+		if base.name != a.Name() {
+			t.Errorf("Base().name = %q, want %q", base.name, a.Name())
+		}
 	}
 }
diff --git a/internal/tmuxedit/agentutil.go b/internal/tmuxedit/agentutil.go
new file mode 100644
index 0000000..924a4a8
--- /dev/null
+++ b/internal/tmuxedit/agentutil.go
@@ -0,0 +1,160 @@
+// Package tmuxedit implements a tmux popup editor for composing AI agent prompts.
+// agentutil.go provides shared helpers for prompt extraction and tmux key sending
+// used by individual agent implementations.
+package tmuxedit
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// promptMatch holds a regex match result with its line number in the pane.
+type promptMatch struct {
+	lineNum int
+	text    string // capture group 1
+}
+
+// matchPromptLines runs the prompt regex against each pane line, returning
+// matches with their line numbers for contiguity analysis.
+func matchPromptLines(re *regexp.Regexp, paneContent string) []promptMatch {
+	paneLines := strings.Split(paneContent, "\n")
+	var matches []promptMatch
+	for i, line := range paneLines {
+		m := re.FindStringSubmatch(line)
+		if len(m) >= 2 {
+			matches = append(matches, promptMatch{lineNum: i, text: m[1]})
+		}
+	}
+	return matches
+}
+
+// joinAllMatches strips noise from all matches and joins the non-empty results
+// with newlines. Used when SectionPattern has already scoped to the prompt area.
+func joinAllMatches(matches []promptMatch, strips []string) string {
+	var lines []string
+	for _, m := range matches {
+		line := stripNoise(m.text, strips)
+		if line != "" {
+			lines = append(lines, line)
+		}
+	}
+	return strings.Join(lines, "\n")
+}
+
+// joinLastContiguousBlock takes the last group of matches on consecutive line
+// numbers, strips noise from each, and joins the non-empty results with
+// newlines. This ensures that only the bottom-most box (the input prompt)
+// is captured when multiple box-drawing sections exist in the pane.
+func joinLastContiguousBlock(matches []promptMatch, strips []string) string {
+	last := len(matches) - 1
+	start := last
+	for start > 0 && matches[start].lineNum-matches[start-1].lineNum == 1 {
+		start--
+	}
+	var lines []string
+	for i := start; i <= last; i++ {
+		line := stripNoise(matches[i].text, strips)
+		if line != "" {
+			lines = append(lines, line)
+		}
+	}
+	return strings.Join(lines, "\n")
+}
+
+// scopeToLastSection extracts the content between the last two lines matching
+// the section delimiter pattern. This isolates the prompt area (e.g. Claude's
+// ─── rules) from previous conversation content. Returns the full content if
+// no pattern is set or fewer than two delimiters are found.
+func scopeToLastSection(paneContent, sectionPattern string) string {
+	if sectionPattern == "" {
+		return paneContent
+	}
+	re, err := regexp.Compile(sectionPattern)
+	if err != nil {
+		return paneContent
+	}
+	lines := strings.Split(paneContent, "\n")
+	var delimLines []int
+	for i, line := range lines {
+		if re.MatchString(line) {
+			delimLines = append(delimLines, i)
+		}
+	}
+	if len(delimLines) < 2 {
+		return paneContent
+	}
+	start := delimLines[len(delimLines)-2] + 1
+	end := delimLines[len(delimLines)-1]
+	if start >= end {
+		return paneContent
+	}
+	return strings.Join(lines[start:end], "\n")
+}
+
+// stripNoise removes each of the agent's StripPatterns from text and trims
+// whitespace.
+func stripNoise(text string, patterns []string) string {
+	for _, p := range patterns {
+		text = strings.ReplaceAll(text, p, "")
+	}
+	return strings.TrimSpace(text)
+}
+
+// sendClearSequence parses a space-separated key sequence and sends each
+// token individually. Tokens with a "*N" suffix (e.g. "BSpace*200") are
+// sent N times using tmux