Use built-in agent preset defaults

CHANGELOG.md

@@ -7,6 +7,12 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 ## [Unreleased]
 
 ### Changed
+- Built-in agent presets (`claude`, `codex`, `opencode`) now live in
+  memory and user preset files merge over them by name instead of
+  patterm writing default preset files into `$XDG_CONFIG_HOME`. Add
+  `"disabled": true` in a matching user preset to hide a built-in.
+- Generated MCP config files for agent launches now live under the
+  runtime agent directory instead of `$XDG_CONFIG_HOME/patterm/mcp`.
 - Auto-summarization settings now save as soon as a changed row is
   applied, including cadence/provider/toggle changes and model edits,
   without requiring a separate save step.
@@ -21,6 +27,10 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   using an ellipsized single-line value.
 
 ### Fixed
+- Claude permission prompts are now detected from the rendered pane as
+  well as the recent output tail, so the sidebar marks the pane as
+  waiting for permission even while `Calling patterm...` continues to
+  repaint.
 - Removed the redundant "Back to Settings" row from the
   Agents / Auto-summarization settings screen.
 

SPEC.md

@@ -39,7 +39,7 @@ The tool is one Go process that owns: the TUI, all PTYs, vt-emulated grids, sess
 
 ## 3. Project state layout
 
-Scratchpads (user data) live under `$XDG_DATA_HOME`; presets and config live under `$XDG_CONFIG_HOME`.
+Scratchpads (user data) live under `$XDG_DATA_HOME`; user-authored preset overlays and config live under `$XDG_CONFIG_HOME`.
 
 ```
 $XDG_DATA_HOME/patterm/
@@ -53,12 +53,12 @@ $XDG_DATA_HOME/patterm/
             └── <agent-written>.md
 
 $XDG_CONFIG_HOME/patterm/
-├── config.json                # global settings (theme, default keymap, etc.)
+├── settings.json              # global settings, written only after the user changes settings
 └── presets/
     ├── agents/
-    │   ├── claude.json        # ships as default
+    │   ├── claude.json        # optional overlay for built-in claude
-    │   ├── codex.json         # ships as default
+    │   ├── codex.json         # optional overlay for built-in codex
-    │   ├── opencode.json      # ships as default
+    │   ├── opencode.json      # optional overlay for built-in opencode
     │   └── <user-defined>.json
     └── processes/
         ├── dev.json           # e.g. { "name": "bun run dev", "argv": ["bun", "run", "dev"] }
@@ -66,7 +66,7 @@ $XDG_CONFIG_HOME/patterm/
         └── <user-defined>.json
 ```
 
-Both preset directories are scanned at startup; every file found becomes a palette entry ("Spawn agent: claude", "Run process: bun run dev", …). Presets are project-agnostic in v1 — the same set is available in every project. Per-project overrides can be added later.
+patterm always has built-in agent presets for `claude`, `codex`, and `opencode`. User preset files are scanned at startup and merged into matching built-ins by `name`, or added as standalone custom presets when the name is new. A matching file with `"disabled": true` hides a built-in. Startup does not write default preset files. Presets are project-agnostic in v1 — the same set is available in every project. Per-project overrides can be added later.
 
 Project key = `sha256(realpath(project_dir))[:16]`. Used only as a scratchpad directory name — there is no daemon to look up.
 
@@ -121,7 +121,7 @@ Scratchpads and command-preset trust grants persist across runs. Sessions and ch
 Almost all application functions are driven through a single command palette opened with `Ctrl-K`. The palette is a fuzzy-searchable list of commands, scoped to whatever makes sense for the current focus. Two kinds of entries appear:
 
 - **Built-in commands** — "Switch to session…", "Focus pane…", "Take input control", "Release control to orchestrator", "Open scratchpad…", "Kill child…", "Quit", etc.
-- **Preset commands** — one entry per file under `$XDG_CONFIG_HOME/patterm/presets/`. Agent presets surface as "Spawn agent: codex" / "Spawn agent: claude" / …; process presets surface as "Run process: bun run dev" / "Run process: vitest" / …. The label comes from the preset's `name` field; the action is "launch this preset into a new pane."
+- **Preset commands** — one entry per built-in or user-defined preset. Agent presets surface as "Spawn agent: codex" / "Spawn agent: claude" / …; process presets surface as "Run process: bun run dev" / "Run process: vitest" / …. The label comes from the preset's `name` field; the action is "launch this preset into a new pane."
 
 Selecting a preset either launches it immediately (no required args) or opens a sub-palette for optional args — namely an **initial prompt** (agent presets only), which patterm injects into the spawned PTY's input after the agent is ready (§8). The orchestrator equivalent of this — `spawn_agent` / `spawn_process` MCP tools — uses the exact same machinery: pick a preset by name, optionally supply an initial prompt, patterm handles the rest.
 
@@ -365,11 +365,11 @@ Risks acknowledged: the orchestrator's reading of the prompt is a vision/parsing
 
 ## 10. Presets
 
-Presets are user-editable JSON files that describe how to launch something. patterm itself has no hard-coded agent or process types — every spawnable thing is a preset. Two flavours:
+Presets describe how to launch something. patterm has built-in defaults for common agent CLIs, and user-editable JSON files can override, disable, or add presets. Two flavours:
 
 ### Agent presets
 
-`$XDG_CONFIG_HOME/patterm/presets/agents/<name>.json`. Launches a vendor LLM CLI with MCP wired up and the conversation-protocol addendum injected.
+Built-in agent presets launch vendor LLM CLIs with MCP wired up and the conversation-protocol addendum injected. `$XDG_CONFIG_HOME/patterm/presets/agents/<name>.json` can overlay a built-in by `name` or define a new agent preset.
 
 | Field | Purpose |
 |---|---|
@@ -377,17 +377,18 @@ Presets are user-editable JSON files that describe how to launch something. patt
 | `argv` | Full launch argv (e.g. `["claude"]`, `["codex", "--no-tui-banner"]`) |
 | `env` | Env vars to set (merged over inherited env) |
 | `working_dir` | Defaults to the project root |
+| `disabled` | If `true`, hides a built-in preset with the same `name` |
 | `mcp_injection` | How to point this CLI at patterm's stdio proxy. One of: `{ "kind": "flag", "flag": "--mcp-config", "config_path": "..." }`, `{ "kind": "config_file", "path": "~/.codex/config.toml", "merge_key": "mcp_servers" }`, `{ "kind": "env_var", "var": "MCP_CONFIG_PATH" }` |
 | `ready_signal` | How to detect the TUI is ready (default: 1s idle after launch). Override per-CLI if needed. |
 | `chrome_trim_hints` | Optional regexes / row ranges for stripping vendor chrome in grid reads |
 
-Default presets shipped: `claude`, `codex`, `opencode`. Authoring these is per-vendor research — each CLI has its own MCP config conventions, ready states, and TUI chrome. Users can copy and edit them, or add new ones (e.g. a second `claude` preset that launches with a specific model or system prompt file).
+Built-in presets: `claude`, `codex`, `opencode`. Authoring these is per-vendor research — each CLI has its own MCP config conventions, ready states, idle detection, and TUI chrome. Users can add small overlay files for built-ins, disable built-ins, or add new presets (e.g. a second `claude-sonnet` preset that launches with a specific model or system prompt file).
 
 MCP config flow: at startup, for each agent preset, patterm renders a small JSON pointing at its own `mcp-stdio` proxy subcommand (`patterm mcp-stdio --socket <pid-sock> --identity <token>`) into a per-preset temp file. The launch then uses the preset's `mcp_injection` strategy to hand that path to the CLI. The user's global vendor config is never mutated.
 
 ### Process presets
 
-`$XDG_CONFIG_HOME/patterm/presets/processes/<name>.json`. Launches a raw command in a PTY — no MCP, no addendum, no system prompt.
+`$XDG_CONFIG_HOME/patterm/presets/processes/<name>.json`. Launches a raw command in a PTY — no MCP, no addendum, no system prompt. There are no built-in process presets.
 
 | Field | Purpose |
 |---|---|

TODO.md

@@ -0,0 +1 @@
+- [ ] We should show idle state in the top tab bar as well

internal/app/classifier.go

@@ -50,8 +50,14 @@ func (s *Session) classifyOne(c *Child) {
 	idleMS := c.IdleMS()
 	titleIdleMS := c.TitleIdleMS()
 	title := c.Title()
-	tail := c.tailBytes(classifierTailBytes)
+	tail := stripANSIBytes(nil, c.tailBytes(classifierTailBytes))
-	state, reason := classify(c.idleDetection, exited, exitNonZero, idleMS, titleIdleMS, title, tail)
+	var screen []byte
+	if em := c.Emulator(); em != nil {
+		if txt, err := em.ScreenText(); err == nil {
+			screen = []byte(txt)
+		}
+	}
+	state, reason := classify(c.idleDetection, exited, exitNonZero, idleMS, titleIdleMS, title, tail, screen)
 	if c.setIdleState(state, reason) {
 		s.emitStateChanged(c.ID, state)
 	}

internal/app/idle.go

@@ -118,7 +118,8 @@ func compilePatterns(ps []string) []*regexp.Regexp {
 //   - titleIdleMS: ms since the last OSC title change (0 if no title yet)
 //   - title: current OSC title
 //   - tail: recent output bytes for regex matching
-func classify(cfg *resolvedIdleDetection, exited, exitNonZero bool, idleMS, titleIdleMS int64, title string, tail []byte) (IdleState, string) {
+//   - screen: current rendered screen text for persistent prompt matching
+func classify(cfg *resolvedIdleDetection, exited, exitNonZero bool, idleMS, titleIdleMS int64, title string, tail, screen []byte) (IdleState, string) {
 	if exited {
 		if exitNonZero {
 			return StateError, "process exited non-zero"
@@ -128,14 +129,14 @@ func classify(cfg *resolvedIdleDetection, exited, exitNonZero bool, idleMS, titl
 	if cfg == nil {
 		cfg = &resolvedIdleDetection{strategy: StrategyOutputActivity, idleThresholdMS: defaultIdleThresholdMS}
 	}
-	if len(tail) > 0 {
+	if len(tail) > 0 || len(screen) > 0 {
-		if matchAny(cfg.errorRegexes, tail) {
+		if matchAny(cfg.errorRegexes, tail, screen) {
 			return StateError, "error regex matched"
 		}
-		if matchAny(cfg.permissionRegexes, tail) {
+		if matchAny(cfg.permissionRegexes, tail, screen) {
 			return StatePermission, "permission regex matched"
 		}
-		if matchAny(cfg.thinkingRegexes, tail) {
+		if matchAny(cfg.thinkingRegexes, tail, screen) {
 			return StateThinking, "thinking regex matched"
 		}
 	}
@@ -172,10 +173,12 @@ func baseStateFromIdleMS(idleMS, threshold int64) (IdleState, string) {
 	return StateIdle, "quiet for threshold"
 }
 
-func matchAny(res []*regexp.Regexp, tail []byte) bool {
+func matchAny(res []*regexp.Regexp, texts ...[]byte) bool {
 	for _, re := range res {
-		if re.Match(tail) {
+		for _, text := range texts {
-			return true
+			if len(text) > 0 && re.Match(text) {
+				return true
+			}
 		}
 	}
 	return false

internal/app/idle_test.go

@@ -30,7 +30,7 @@ func TestClassifyOutputActivity(t *testing.T) {
 	}
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
-			got, _ := classify(cfg, false, false, tc.idleMS, 0, "", nil)
+			got, _ := classify(cfg, false, false, tc.idleMS, 0, "", nil, nil)
 			if got != tc.want {
 				t.Fatalf("got %q want %q", got, tc.want)
 			}
@@ -41,18 +41,18 @@ func TestClassifyOutputActivity(t *testing.T) {
 func TestClassifyTitleStability(t *testing.T) {
 	cfg := &resolvedIdleDetection{strategy: StrategyOSCTitleStability, idleThresholdMS: 2000}
 	// Title change recent → working.
-	if got, _ := classify(cfg, false, false, 9999, 500, "step 3", nil); got != StateWorking {
+	if got, _ := classify(cfg, false, false, 9999, 500, "step 3", nil, nil); got != StateWorking {
 		t.Fatalf("recent title change: got %q", got)
 	}
 	// Title stable past threshold → idle.
-	if got, _ := classify(cfg, false, false, 9999, 5000, "step 3", nil); got != StateIdle {
+	if got, _ := classify(cfg, false, false, 9999, 5000, "step 3", nil, nil); got != StateIdle {
 		t.Fatalf("stable title: got %q", got)
 	}
 	// No title yet: fall back to output activity.
-	if got, _ := classify(cfg, false, false, 100, 0, "", nil); got != StateWorking {
+	if got, _ := classify(cfg, false, false, 100, 0, "", nil, nil); got != StateWorking {
 		t.Fatalf("no title yet, recent output: got %q", got)
 	}
-	if got, _ := classify(cfg, false, false, 5000, 0, "", nil); got != StateIdle {
+	if got, _ := classify(cfg, false, false, 5000, 0, "", nil, nil); got != StateIdle {
 		t.Fatalf("no title yet, output idle: got %q", got)
 	}
 }
@@ -67,46 +67,51 @@ func TestClassifyTitleStatus(t *testing.T) {
 			"error":      StateError,
 		},
 	}
-	if got, _ := classify(cfg, false, false, 9999, 500, "Thinking…", nil); got != StateThinking {
+	if got, _ := classify(cfg, false, false, 9999, 500, "Thinking…", nil, nil); got != StateThinking {
 		t.Fatalf("thinking title: got %q", got)
 	}
-	if got, _ := classify(cfg, false, false, 9999, 500, "Waiting for permission", nil); got != StatePermission {
+	if got, _ := classify(cfg, false, false, 9999, 500, "Waiting for permission", nil, nil); got != StatePermission {
 		t.Fatalf("permission title: got %q", got)
 	}
 	// No match in map → fall back to stability.
-	if got, _ := classify(cfg, false, false, 9999, 5000, "ready", nil); got != StateIdle {
+	if got, _ := classify(cfg, false, false, 9999, 5000, "ready", nil, nil); got != StateIdle {
 		t.Fatalf("unmatched title, stable: got %q", got)
 	}
 }
 
 func TestClassifyPromoterRegex(t *testing.T) {
 	cfg := &resolvedIdleDetection{
-		strategy:           StrategyOutputActivity,
+		strategy:          StrategyOutputActivity,
-		idleThresholdMS:    2000,
+		idleThresholdMS:   2000,
-		permissionRegexes:  []*regexp.Regexp{mustCompile(t, `Approve\?`)},
+		permissionRegexes: []*regexp.Regexp{mustCompile(t, `Approve\?`)},
-		errorRegexes:       []*regexp.Regexp{mustCompile(t, `panic:`)},
+		errorRegexes:      []*regexp.Regexp{mustCompile(t, `panic:`)},
-		thinkingRegexes:    []*regexp.Regexp{mustCompile(t, `Thinking`)},
+		thinkingRegexes:   []*regexp.Regexp{mustCompile(t, `Thinking`)},
 	}
 	// Permission promoter beats idle.
-	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("Approve? [y/n]")); got != StatePermission {
+	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("Approve? [y/n]"), nil); got != StatePermission {
 		t.Fatalf("permission promoter: got %q", got)
 	}
 	// Error trumps permission.
-	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("panic: bad\nApprove?")); got != StateError {
+	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("panic: bad\nApprove?"), nil); got != StateError {
 		t.Fatalf("error promoter beats permission: got %q", got)
 	}
 	// Thinking promoter on idle output.
-	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("Thinking…")); got != StateThinking {
+	if got, _ := classify(cfg, false, false, 5000, 0, "", []byte("Thinking…"), nil); got != StateThinking {
 		t.Fatalf("thinking promoter: got %q", got)
 	}
+	// Rendered-screen prompts still promote even when the raw tail no
+	// longer contains the original prompt bytes.
+	if got, _ := classify(cfg, false, false, 100, 0, "", []byte("Calling patterm..."), []byte("Approve? [y/n]")); got != StatePermission {
+		t.Fatalf("screen permission promoter: got %q", got)
+	}
 }
 
 func TestClassifyExitTerminal(t *testing.T) {
 	cfg := &resolvedIdleDetection{strategy: StrategyOutputActivity, idleThresholdMS: 2000}
-	if got, _ := classify(cfg, true, true, 0, 0, "", nil); got != StateError {
+	if got, _ := classify(cfg, true, true, 0, 0, "", nil, nil); got != StateError {
 		t.Fatalf("non-zero exit: got %q", got)
 	}
-	if got, _ := classify(cfg, true, false, 0, 0, "", nil); got != StateIdle {
+	if got, _ := classify(cfg, true, false, 0, 0, "", nil, nil); got != StateIdle {
 		t.Fatalf("clean exit: got %q", got)
 	}
 }

internal/app/launch.go

@@ -261,15 +261,11 @@ func (l *Launcher) LaunchTerminal(argv []string, displayName, parentID, workDir
 }
 
 func (l *Launcher) writeMCPConfig(identity string) (string, error) {
-	dir, err := preset.ConfigDir()
+	dir, err := mcpRuntimeDir(identity)
 	if err != nil {
 		return "", err
 	}
-	dir = filepath.Join(dir, "mcp")
+	path := filepath.Join(dir, "mcp.json")
-	if err := os.MkdirAll(dir, 0o700); err != nil {
-		return "", err
-	}
-	path := filepath.Join(dir, identity+".json")
 	cfg := map[string]any{
 		"mcpServers": map[string]any{
 			"patterm": map[string]any{

internal/app/launch_test.go

@@ -0,0 +1,30 @@
+package app
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestWriteMCPConfigUsesRuntimeDir(t *testing.T) {
+	runtimeDir := t.TempDir()
+	configHome := filepath.Join(t.TempDir(), "config")
+	t.Setenv("XDG_RUNTIME_DIR", runtimeDir)
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+
+	l := &Launcher{bin: "patterm", mcpSocket: "/tmp/patterm.sock"}
+	path, err := l.writeMCPConfig("abc123")
+	if err != nil {
+		t.Fatalf("writeMCPConfig: %v", err)
+	}
+	if !strings.HasPrefix(path, filepath.Join(runtimeDir, "patterm", "agents", "abc123")) {
+		t.Fatalf("path = %q, want under runtime dir", path)
+	}
+	if _, err := os.Stat(path); err != nil {
+		t.Fatalf("config file stat: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(configHome, "patterm")); !os.IsNotExist(err) {
+		t.Fatalf("writeMCPConfig created XDG config dir or unexpected stat error: %v", err)
+	}
+}

internal/harness/scenarios/idle_screen_permission_prompt.json

@@ -0,0 +1,37 @@
+{
+  "name": "idle_screen_permission_prompt",
+  "presets": {
+    "processes": [
+      {
+        "name": "screen-permission",
+        "argv": [
+          "sh",
+          "-lc",
+          "printf '\\033[2J\\033[HCalling patterm...\\n\\nTool use\\n\\nDo you want to proceed?\\n  1. Yes\\n'; i=0; while [ $i -lt 300 ]; do printf '\\033[HCalling patterm... %03d' $i; i=$((i+1)); done; sleep 60"
+        ],
+        "idle_detection": {
+          "strategy": "output_activity",
+          "idle_threshold_ms": 500,
+          "permission_patterns": ["Do you want to proceed\\?"]
+        }
+      }
+    ]
+  },
+  "trust": ["screen-permission"],
+  "steps": [
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": {"kind": "command", "preset": "screen-permission", "name": "screen-permission"},
+      "save_as": "proc"
+    },
+    {
+      "type": "wait_until_mcp",
+      "method": "get_process_status",
+      "params": {"process_id": "{{proc.process_id}}"},
+      "path": "idle_state",
+      "equals": "permission",
+      "timeout_ms": 4000
+    }
+  ]
+}

internal/preset/preset.go

@@ -4,6 +4,7 @@
 package preset
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -35,15 +36,16 @@ type Preset struct {
 	Argv       []string          `json:"argv"`
 	Env        map[string]string `json:"env,omitempty"`
 	WorkingDir string            `json:"working_dir,omitempty"`
+	Disabled   bool              `json:"disabled,omitempty"`
 
 	// Process-only.
 	Shell bool `json:"shell,omitempty"`
 
 	// Agent-only. SPEC §10.
-	MCPInjection     *MCPInjection  `json:"mcp_injection,omitempty"`
+	MCPInjection    *MCPInjection  `json:"mcp_injection,omitempty"`
-	ReadySignal      *ReadySignal   `json:"ready_signal,omitempty"`
+	ReadySignal     *ReadySignal   `json:"ready_signal,omitempty"`
-	ChromeTrimHints  []string       `json:"chrome_trim_hints,omitempty"`
+	ChromeTrimHints []string       `json:"chrome_trim_hints,omitempty"`
-	IdleDetection    *IdleDetection `json:"idle_detection,omitempty"`
+	IdleDetection   *IdleDetection `json:"idle_detection,omitempty"`
 }
 
 // IdleDetection configures steady-state idle classification for an
@@ -119,28 +121,22 @@ type Set struct {
 	Processes []*Preset
 }
 
-// Load scans the standard locations under $XDG_CONFIG_HOME/patterm/
+// Load returns the built-in presets plus user overlays from
-// presets/{agents,processes}/*.json. Unknown files are skipped with a
+// $XDG_CONFIG_HOME/patterm/presets/{agents,processes}/*.json. Startup
-// warning to stderr; the spec is forgiving here.
+// does not write default files; user files only override or extend the
+// in-memory defaults. A user overlay with {"disabled": true} hides a
+// built-in preset of the same name.
 func Load() (Set, error) {
 	base, err := ConfigDir()
 	if err != nil {
 		return Set{}, err
 	}
-	if err := os.MkdirAll(base, 0o700); err != nil {
-		return Set{}, fmt.Errorf("preset: mkdir %s: %w", base, err)
-	}
 
-	// Make sure the default-preset files exist on first run. Idempotent.
+	agents, err := loadWithDefaults(filepath.Join(base, "presets", "agents"), KindAgent, defaultAgentPresets())
-	if err := ensureDefaults(base); err != nil {
-		return Set{}, err
-	}
-
-	agents, err := loadDir(filepath.Join(base, "presets", "agents"), KindAgent)
 	if err != nil {
 		return Set{}, err
 	}
-	procs, err := loadDir(filepath.Join(base, "presets", "processes"), KindCommand)
+	procs, err := loadWithDefaults(filepath.Join(base, "presets", "processes"), KindCommand, nil)
 	if err != nil {
 		return Set{}, err
 	}
@@ -160,51 +156,154 @@ func ConfigDir() (string, error) {
 	return filepath.Join(home, ".config", "patterm"), nil
 }
 
-func loadDir(dir string, kind Kind) ([]*Preset, error) {
+func loadWithDefaults(dir string, kind Kind, defaults []*Preset) ([]*Preset, error) {
-	if err := os.MkdirAll(dir, 0o700); err != nil {
+	byName := make(map[string]*Preset, len(defaults))
-		return nil, fmt.Errorf("preset: mkdir %s: %w", dir, err)
+	for _, p := range defaults {
+		cp := clonePreset(p)
+		cp.Kind = kind
+		byName[cp.Name] = cp
 	}
+
 	entries, err := os.ReadDir(dir)
 	if err != nil {
+		if os.IsNotExist(err) {
+			return sortedPresets(byName), nil
+		}
 		return nil, fmt.Errorf("preset: read %s: %w", dir, err)
 	}
-	var out []*Preset
 	for _, e := range entries {
 		if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") {
 			continue
 		}
 		path := filepath.Join(dir, e.Name())
-		p, err := loadFile(path, kind)
+		p, err := loadFileOverlay(path, kind, byName)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "patterm: preset %s: %v\n", path, err)
 			continue
 		}
+		if p.Disabled {
+			delete(byName, p.Name)
+			continue
+		}
+		byName[p.Name] = p
+	}
+	return sortedPresets(byName), nil
+}
+
+func sortedPresets(byName map[string]*Preset) []*Preset {
+	out := make([]*Preset, 0, len(byName))
+	for _, p := range byName {
 		out = append(out, p)
 	}
 	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
-	return out, nil
+	return out
 }
 
-func loadFile(path string, kind Kind) (*Preset, error) {
+func loadFileOverlay(path string, kind Kind, defaults map[string]*Preset) (*Preset, error) {
 	b, err := os.ReadFile(path)
 	if err != nil {
 		return nil, err
 	}
+	var header struct {
+		Name     string `json:"name"`
+		Disabled bool   `json:"disabled,omitempty"`
+	}
+	if err := json.Unmarshal(b, &header); err != nil {
+		return nil, err
+	}
+	if header.Name == "" {
+		return nil, errors.New("missing 'name'")
+	}
+	if def := defaults[header.Name]; def != nil {
+		p, err := mergePreset(def, b)
+		if err != nil {
+			return nil, err
+		}
+		p.Path = path
+		p.Kind = kind
+		return p, validatePreset(p)
+	}
+	var p Preset
+	if err := json.Unmarshal(b, &p); err != nil {
+		return nil, err
+	}
+	p.Path = path
+	p.Kind = kind
+	return &p, validatePreset(&p)
+}
+
+func validatePreset(p *Preset) error {
+	if p.Name == "" {
+		return errors.New("missing 'name'")
+	}
+	if p.Disabled {
+		return nil
+	}
+	if len(p.Argv) == 0 && !p.Shell {
+		return errors.New("missing 'argv'")
+	}
+	return nil
+}
+
+func mergePreset(def *Preset, overlay []byte) (*Preset, error) {
+	base, err := presetMap(def)
+	if err != nil {
+		return nil, err
+	}
+	var over map[string]any
+	dec := json.NewDecoder(bytes.NewReader(overlay))
+	dec.UseNumber()
+	if err := dec.Decode(&over); err != nil {
+		return nil, err
+	}
+	deepMerge(base, over)
+	b, err := json.Marshal(base)
+	if err != nil {
+		return nil, err
+	}
 	var p Preset
 	if err := json.Unmarshal(b, &p); err != nil {
 		return nil, err
 	}
-	if p.Name == "" {
-		return nil, errors.New("missing 'name'")
-	}
-	if len(p.Argv) == 0 && !p.Shell {
-		return nil, errors.New("missing 'argv'")
-	}
-	p.Path = path
-	p.Kind = kind
 	return &p, nil
 }
 
+func presetMap(p *Preset) (map[string]any, error) {
+	b, err := json.Marshal(p)
+	if err != nil {
+		return nil, err
+	}
+	var m map[string]any
+	dec := json.NewDecoder(bytes.NewReader(b))
+	dec.UseNumber()
+	if err := dec.Decode(&m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+func deepMerge(dst, src map[string]any) {
+	for k, v := range src {
+		if sm, ok := v.(map[string]any); ok {
+			if dm, ok := dst[k].(map[string]any); ok {
+				deepMerge(dm, sm)
+				continue
+			}
+		}
+		dst[k] = v
+	}
+}
+
+func clonePreset(p *Preset) *Preset {
+	if p == nil {
+		return nil
+	}
+	b, _ := json.Marshal(p)
+	var out Preset
+	_ = json.Unmarshal(b, &out)
+	return &out
+}
+
 // ResolvedArgv returns the argv to actually exec, handling the
 // process-preset "shell: true" case (SPEC §10).
 func (p *Preset) ResolvedArgv() []string {
@@ -214,17 +313,9 @@ func (p *Preset) ResolvedArgv() []string {
 	return p.Argv
 }
 
-// ensureDefaults writes default agent presets (claude/codex/opencode)
+func defaultAgentPresets() []*Preset {
-// and a sample process preset on first run. Never overwrites existing
+	bodies := []string{
-// user files.
+		`{
-func ensureDefaults(base string) error {
-	defaults := []struct {
-		rel  string
-		body string
-	}{
-		{
-			"presets/agents/claude.json",
-			`{
   "name": "claude",
   "argv": ["claude"],
   "mcp_injection": { "kind": "flag", "flag": "--mcp-config" },
@@ -249,10 +340,7 @@ func ensureDefaults(base string) error {
   ]
 }
 `,
-		},
+		`{
-		{
-			"presets/agents/codex.json",
-			`{
   "name": "codex",
   "argv": ["codex"],
   "mcp_injection": {
@@ -275,10 +363,7 @@ func ensureDefaults(base string) error {
   ]
 }
 `,
-		},
+		`{
-		{
-			"presets/agents/opencode.json",
-			`{
   "name": "opencode",
   "argv": ["opencode"],
   "mcp_injection": {
@@ -301,19 +386,15 @@ func ensureDefaults(base string) error {
   ]
 }
 `,
-		},
 	}
-	for _, d := range defaults {
+	out := make([]*Preset, 0, len(bodies))
-		full := filepath.Join(base, d.rel)
+	for _, body := range bodies {
-		if _, err := os.Stat(full); err == nil {
+		var p Preset
-			continue
+		if err := json.Unmarshal([]byte(body), &p); err != nil {
-		}
+			panic(err)
-		if err := os.MkdirAll(filepath.Dir(full), 0o700); err != nil {
-			return err
-		}
-		if err := os.WriteFile(full, []byte(d.body), 0o600); err != nil {
-			return err
 		}
+		p.Kind = KindAgent
+		out = append(out, &p)
 	}
-	return nil
+	return out
 }

internal/preset/preset_test.go

@@ -0,0 +1,124 @@
+package preset
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestLoadUsesBuiltInDefaultsWithoutWritingConfig(t *testing.T) {
+	configHome := filepath.Join(t.TempDir(), "config")
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+
+	set, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(configHome, "patterm")); !os.IsNotExist(err) {
+		t.Fatalf("Load created config dir or unexpected stat error: %v", err)
+	}
+	if len(set.Agents) != 3 {
+		t.Fatalf("agents len = %d, want 3", len(set.Agents))
+	}
+	claude := presetByName(set.Agents, "claude")
+	if claude == nil {
+		t.Fatal("missing built-in claude preset")
+	}
+	if claude.IdleDetection == nil || len(claude.IdleDetection.PermissionPatterns) == 0 {
+		t.Fatalf("built-in claude missing permission patterns: %+v", claude.IdleDetection)
+	}
+}
+
+func TestLoadMergesUserOverlayIntoBuiltInPreset(t *testing.T) {
+	configHome := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	dir := filepath.Join(configHome, "patterm", "presets", "agents")
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(dir, "claude.json"), `{
+  "name": "claude",
+  "argv": ["claude", "--model", "sonnet"],
+  "idle_detection": { "idle_threshold_ms": 3500 }
+}`)
+
+	set, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	claude := presetByName(set.Agents, "claude")
+	if claude == nil {
+		t.Fatal("missing claude preset")
+	}
+	if got := claude.Argv; len(got) != 3 || got[0] != "claude" || got[2] != "sonnet" {
+		t.Fatalf("argv = %#v", got)
+	}
+	if claude.IdleDetection.IdleThresholdMS != 3500 {
+		t.Fatalf("idle threshold = %d", claude.IdleDetection.IdleThresholdMS)
+	}
+	if len(claude.IdleDetection.PermissionPatterns) == 0 {
+		t.Fatalf("permission patterns were not inherited: %+v", claude.IdleDetection)
+	}
+	if claude.MCPInjection == nil || claude.MCPInjection.Kind != "flag" {
+		t.Fatalf("mcp injection was not inherited: %+v", claude.MCPInjection)
+	}
+}
+
+func TestLoadCanDisableBuiltInPreset(t *testing.T) {
+	configHome := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	dir := filepath.Join(configHome, "patterm", "presets", "agents")
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(dir, "opencode.json"), `{"name":"opencode","disabled":true}`)
+
+	set, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if presetByName(set.Agents, "opencode") != nil {
+		t.Fatal("opencode preset was not disabled")
+	}
+	if presetByName(set.Agents, "claude") == nil || presetByName(set.Agents, "codex") == nil {
+		t.Fatalf("other built-ins missing: %+v", set.Agents)
+	}
+}
+
+func TestLoadAddsCustomUserPreset(t *testing.T) {
+	configHome := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	dir := filepath.Join(configHome, "patterm", "presets", "processes")
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(dir, "test.json"), `{"name":"test","argv":["go","test","./..."]}`)
+
+	set, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	proc := presetByName(set.Processes, "test")
+	if proc == nil {
+		t.Fatal("missing custom process preset")
+	}
+	if proc.Kind != KindCommand {
+		t.Fatalf("kind = %q", proc.Kind)
+	}
+}
+
+func presetByName(ps []*Preset, name string) *Preset {
+	for _, p := range ps {
+		if p.Name == name {
+			return p
+		}
+	}
+	return nil
+}
+
+func writeFile(t *testing.T, path, body string) {
+	t.Helper()
+	if err := os.WriteFile(path, []byte(body), 0o600); err != nil {
+		t.Fatal(err)
+	}
+}