fixed session resume launching with global extensions. resumed subagents launch with subagent-specific tools. also fixed freezing upon resume

pi-extension/subagents/session.ts

@@ -79,6 +79,70 @@ export function seedSubagentSessionFile(params: {
   writeFileSync(params.childSessionFile, lines.join("\n") + "\n", "utf8");
 }
 
+/**
+ * A snapshot of everything needed to reconstruct a subagent's sandbox when its
+ * session is later resumed via `subagent_message({ sessionId })`.
+ *
+ * Written next to the session file as `<sessionFile>.loadout.json` at spawn
+ * time. Resume replays this exact snapshot so the reincarnated process gets the
+ * same `--no-extensions` + `--tools` restriction, model, identity, spawn
+ * whitelist, cwd, and config dir it originally ran with — instead of falling
+ * back to pi's default (all global extensions + full toolset). Storing the
+ * resolved loadout (rather than re-deriving from the agent `.md` by name) keeps
+ * resume faithful even if the agent definition is later edited, moved, or
+ * deleted.
+ */
+export interface SubagentLoadout {
+  /** Agent profile name (for PI_SUBAGENT_AGENT); null for agentless spawns. */
+  agent: string | null;
+  /** The `--tools` allowlist string, or null when the spawn was unrestricted. */
+  toolAllowlist: string | null;
+  /** Model id (without thinking suffix), or null to use the session default. */
+  model: string | null;
+  /** Thinking level appended to the model as `model:level`, or null. */
+  thinking: string | null;
+  /** How the identity text was applied: append/replace, or null. */
+  systemPromptMode: "append" | "replace" | null;
+  /** The system-prompt/identity text, only when it lived in the system prompt. */
+  identity: string | null;
+  /** Agents this subagent was allowed to spawn (for PI_SUBAGENT_ALLOWED). */
+  spawnable: string[] | null;
+  /** Whether the agent auto-exits (informational; resume forces autonomous). */
+  autoExit: boolean;
+  /** Working directory the subagent ran in, or null. */
+  cwd: string | null;
+  /** PI_CODING_AGENT_DIR the subagent resolved config/extensions from, or null. */
+  agentDir: string | null;
+}
+
+/** Path of the loadout sidecar written next to a subagent session file. */
+export function loadoutSidecarPath(sessionFile: string): string {
+  return `${sessionFile}.loadout.json`;
+}
+
+/** Persist a subagent's resolved sandbox loadout beside its session file. */
+export function writeSubagentLoadout(sessionFile: string, loadout: SubagentLoadout): void {
+  try {
+    writeFileSync(loadoutSidecarPath(sessionFile), JSON.stringify(loadout), "utf8");
+  } catch {
+    // Best-effort: a missing snapshot only means resume will refuse, never that
+    // it launches unrestricted.
+  }
+}
+
+/** Read a subagent's loadout snapshot, or null if absent/unparseable. */
+export function readSubagentLoadout(sessionFile: string): SubagentLoadout | null {
+  try {
+    const p = loadoutSidecarPath(sessionFile);
+    if (!existsSync(p)) return null;
+    const parsed = JSON.parse(readFileSync(p, "utf8"));
+    if (!parsed || typeof parsed !== "object") return null;
+    return parsed as SubagentLoadout;
+  } catch {
+    return null;
+  }
+}
+
 function readEntries(sessionFile: string): SessionEntry[] {
   const raw = readFileSync(sessionFile, "utf8");
   return raw