feat(pi): add Pi (pi.dev) as a sixth CLI run mode (#206)

SessionMode gains 'pi', a first-class backend alongside Claude Code,
OpenCode, Codex, Gemini and Antigravity: its own PTY, tmux session, rose
tab identity, welcome button, run-mode entry, cron agentType, Docker and
remote-SSH command defaults, and clone-repo Brain option.

Pi is a different shape of CLI from the other four, and three decisions
follow from that:

- It has NO permission prompts and no sandbox, so there is no
  --dangerously-skip-permissions analog and none was invented. The
  privilege-shaped knob is the tri-state approveProjectTrust, which makes
  pi load and EXECUTE repo-local .pi/extensions TypeScript and install
  missing project packages. clampExternalCliBypassForOwner() therefore
  puts pi in the MATERIALIZE branch: a non-granted multi-user owner gets
  --no-approve even when no config was sent, because pi's own default is
  a prompt the session user could answer themselves. That helper had zero
  test coverage; it now has coverage for all four CLIs.
- Only the PI_ prefix joins the env allowlist. Pi's ~34 provider key vars
  share no prefix and ALLOWED_ENV_PREFIXES is one global list with no mode
  context, so admitting them would widen the allowlist for every mode at
  once. Auth goes through pi's /login or the server's own environment.
  --api-key is deliberately never wired: it would put a provider secret on
  the spawn command line.
- pi stays OUT of isAltScreenStripMode(). Its default TUI renders into the
  main screen with terminal-owned scrollback, and its 0.84.0 fullscreen
  mode is runtime-switchable via /settings; that flip was measured to put
  the pane into the alt screen, which the strip would have corrupted.

pi-cli-resolver.ts additionally sanity-probes `pi --version` and requires
semver-shaped output, because `pi` is a short generic name a stray binary
can shadow; GET /api/pi/status surfaces path and version so a
misresolution is diagnosable rather than presenting as a broken mode.

Docker installs pi in its own --ignore-scripts step so that flag cannot
affect the other four CLIs, and seeds its credentials per-file rather than
whole-dir (~/.pi/agent also holds sessions, extensions and package trees).

Verified end to end against pi 0.84.1 on an isolated instance: resolver
search-dir fallback, flag construction, piConfig persistence across a full
server restart, the trust prompt and its --no-approve suppression, the
rose Run button on the default daylight-blue skin (the nested skin block
eats per-mode gradients unless the rule lives inside it), and the buffer
local-echo policy, which pi tolerates where codex did not.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/tmux-manager.ts

@@ -45,6 +45,7 @@ import {
   type EffortLevel,
   type GeminiConfig,
   type AntigravityConfig,
+  type PiConfig,
   type SessionRemote,
   type SessionDocker,
   type DockerCommandMode,
@@ -78,6 +79,7 @@ import {
   resolveCodexDir,
   resolveGeminiDir,
   resolveAntigravityDir,
+  resolvePiDir,
   resolveLocalShell,
   loginShellArgs,
 } from './utils/index.js';
@@ -735,6 +737,63 @@ function buildAntigravityCommand(config?: AntigravityConfig): string {
   return parts.join(' ');
 }
 
+/** Pi's `--thinking` levels. Runtime allowlist — defense in depth beyond the Zod enum. */
+const PI_THINKING_LEVELS = new Set(['off', 'minimal', 'low', 'medium', 'high', 'xhigh', 'max']);
+
+/**
+ * Build the Pi CLI (pi.dev) command with appropriate flags.
+ *
+ * Pi has NO permission prompts and no `--dangerously-skip-permissions` analog, so
+ * there is deliberately nothing bypass-shaped here. The privileged knob is the
+ * TRI-STATE `approveProjectTrust`: `true` -> `--approve` (trust repo-local `.pi/`
+ * config, which means loading and EXECUTING repository TypeScript and installing
+ * missing project packages), `false` -> `--no-approve` (force-deny, used by the
+ * multi-user clamp so the trust prompt never appears), absent -> pi's own
+ * `defaultProjectTrust`.
+ *
+ * `--api-key` is deliberately NEVER wired: it would put a provider secret on the
+ * spawn command line (visible in `ps` and tmux state), which is exactly what the
+ * socket-scoped `tmux setenv` discipline exists to prevent.
+ *
+ * Like the sibling builders, every user value is regex-allowlisted and silently
+ * DROPPED on failure — the result is interpolated into a `bash -c "..."` string.
+ */
+function buildPiCommand(config?: PiConfig): string {
+  const parts = ['pi'];
+
+  if (config?.approveProjectTrust === true) {
+    parts.push('--approve');
+  } else if (config?.approveProjectTrust === false) {
+    parts.push('--no-approve');
+  }
+
+  if (config?.model) {
+    // `:` for a thinking suffix (`sonnet:high`), `/` for `provider/id` (`openai/gpt-4o`).
+    const safeModel = /^[a-zA-Z0-9._\-/:]+$/.test(config.model) ? config.model : undefined;
+    if (safeModel) parts.push('--model', safeModel);
+  }
+
+  if (config?.provider) {
+    const safeProvider = /^[a-z0-9-]+$/.test(config.provider) ? config.provider : undefined;
+    if (safeProvider) parts.push('--provider', safeProvider);
+  }
+
+  if (config?.thinking && PI_THINKING_LEVELS.has(config.thinking)) {
+    parts.push('--thinking', config.thinking);
+  }
+
+  // --session and -c conflict; a valid explicit session id wins.
+  const safeSessionId =
+    config?.resumeSessionId && /^[a-zA-Z0-9._-]+$/.test(config.resumeSessionId) ? config.resumeSessionId : undefined;
+  if (safeSessionId) {
+    parts.push('--session', safeSessionId);
+  } else if (config?.continueSession) {
+    parts.push('-c');
+  }
+
+  return parts.join(' ');
+}
+
 /**
  * Build the spawn command for any session mode.
  * Shared by createSession() and respawnPane() to avoid duplication.
@@ -777,6 +836,7 @@ export function buildSpawnCommand(options: {
   codexConfig?: CodexConfig;
   geminiConfig?: GeminiConfig;
   antigravityConfig?: AntigravityConfig;
+  piConfig?: PiConfig;
   resumeSessionId?: string;
   effort?: EffortLevel;
   /** Codeman session name, passed to claude as `--name` (version-gated, sanitized; local spawns only). */
@@ -823,6 +883,9 @@ export function buildSpawnCommand(options: {
   if (options.mode === 'antigravity') {
     return buildAntigravityCommand(options.antigravityConfig);
   }
+  if (options.mode === 'pi') {
+    return buildPiCommand(options.piConfig);
+  }
   // #208: NOT the literal '$SHELL'. This string is embedded in the `bash -c "…"`
   // argument of the respawn-pane line, which execSync runs through `/bin/sh -c`,
   // so a `$SHELL` here is expanded by the SERVER process's shell against the
@@ -1036,6 +1099,8 @@ function appendResumeFlag(modeCommand: string, mode: SessionMode, resumeId: stri
       return `${modeCommand} resume ${resumeId}`;
     case 'antigravity':
       return `${modeCommand} --conversation ${resumeId}`;
+    case 'pi':
+      return `${modeCommand} --session ${resumeId}`;
     default:
       return modeCommand; // shell / opencode: no resume
   }
@@ -1604,10 +1669,10 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     const exports = [
       'export LANG=en_US.UTF-8',
       'export LC_ALL=en_US.UTF-8',
-      mode === 'codex' || mode === 'gemini' || mode === 'antigravity'
+      mode === 'codex' || mode === 'gemini' || mode === 'antigravity' || mode === 'pi'
         ? 'export COLORTERM=truecolor'
         : 'unset COLORTERM',
-      ...(mode === 'codex' || mode === 'gemini' || mode === 'antigravity' ? ['unset NO_COLOR'] : []),
+      ...(mode === 'codex' || mode === 'gemini' || mode === 'antigravity' || mode === 'pi' ? ['unset NO_COLOR'] : []),
       // Stamp each Codex pane with a unique originator so the response-viewer
       // can locate THIS pane's rollout exactly — codex writes the value into
       // session_meta.originator of every rollout it creates. Without it,
@@ -1698,6 +1763,10 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       const dir = resolveAntigravityDir();
       return { pathExport: dir ? `export PATH="${dir}:$PATH" && ` : '', dir };
     }
+    if (mode === 'pi') {
+      const dir = resolvePiDir();
+      return { pathExport: dir ? `export PATH="${dir}:$PATH" && ` : '', dir };
+    }
     return { pathExport: '', dir: null };
   }
 
@@ -1746,6 +1815,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       codexConfig,
       geminiConfig,
       antigravityConfig,
+      piConfig,
       resumeSessionId,
       envOverrides,
       effort,
@@ -1802,6 +1872,11 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
         'Antigravity CLI not found. Install with: curl -fsSL https://antigravity.google/cli/install.sh | bash'
       );
     }
+    if (mode === 'pi' && !cliDir) {
+      throw new Error(
+        'Pi CLI not found. Install with: npm install -g --ignore-scripts @earendil-works/pi-coding-agent'
+      );
+    }
 
     const envExportsStr = this.buildEnvExports(sessionId, muxName, mode).join(' && ');
 
@@ -1815,6 +1890,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       codexConfig,
       geminiConfig,
       antigravityConfig,
+      piConfig,
       resumeSessionId,
       effort,
       sessionName: name,
@@ -2039,6 +2115,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       codexConfig,
       geminiConfig,
       antigravityConfig,
+      piConfig,
       resumeSessionId,
       envOverrides,
       effort,
@@ -2078,6 +2155,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       codexConfig,
       geminiConfig,
       antigravityConfig,
+      piConfig,
       resumeSessionId,
       effort,
       sessionName: name,