fix(fleet): resolve-then-validate symlink guard + framework helper resolution (#1380) (#1383)

Co-authored-by: code-be-01 <[email protected]>

packages/mosaic/src/fleet/comms-onboarding.ts

@@ -9,8 +9,9 @@
 import { createHash } from 'node:crypto';
 import { existsSync } from 'node:fs';
 import { homedir, hostname } from 'node:os';
-import { join } from 'node:path';
+import { join, resolve } from 'node:path';
 import { readRegularFileSecure } from './secure-file.js';
+import { resolveBrainHome } from './brain-home.js';
 import {
   parseFleetRosterV1,
   resolveInstalledFleetRosterPath,
@@ -260,7 +261,13 @@ context and have an authorized operator relaunch only this exact roster member w
 
 function validateAgentSendHelper(path: string, mosaicHome: string): string | undefined {
   try {
-    readRegularFileSecure(path, { root: mosaicHome, executable: true });
+    readRegularFileSecure(path, {
+      root: mosaicHome,
+      executable: true,
+      // The helper tree may live under the framework config home while this
+      // caller's mosaicHome is the brain; both are framework-owned roots.
+      symlinkTargetRoots: [resolveBrainHome(mosaicHome)],
+    });
     return undefined;
   } catch (error) {
     const reason = error instanceof Error ? error.message : String(error);
@@ -268,8 +275,48 @@ function validateAgentSendHelper(path: string, mosaicHome: string): string | und
   }
 }
 
+/**
+ * Framework install homes probed for tools/tmux/agent-send.sh (stack#1380 M2).
+ * The helper ships with the FRAMEWORK install, which on split-home layouts is
+ * the config home — not the brain (~/.mosaic carries fleet state, no tools).
+ */
+function frameworkHelperHomes(mosaicHome: string): string[] {
+  const homes = [resolve(mosaicHome)];
+  const envHome = process.env['MOSAIC_HOME'];
+  if (envHome && envHome.trim() !== '' && resolve(envHome) !== resolve(mosaicHome)) {
+    homes.push(resolve(envHome));
+  }
+  const configDefault = join(homedir(), '.config', 'mosaic');
+  if (resolve(configDefault) !== resolve(mosaicHome)) homes.push(configDefault);
+  return homes;
+}
+
+function resolveAgentSendHelper(mosaicHome: string): { path: string; error?: string } {
+  const homes = frameworkHelperHomes(mosaicHome);
+  for (const home of homes) {
+    const helper = join(home, 'tools', 'tmux', 'agent-send.sh');
+    if (!existsSync(helper)) continue;
+    const error = validateAgentSendHelper(helper, home);
+    if (!error) return { path: helper };
+    // Present but unsafe: surface that verdict instead of silently probing on.
+    return { path: helper, error };
+  }
+  return {
+    path: join(resolve(mosaicHome), 'tools', 'tmux', 'agent-send.sh'),
+    error:
+      `fleet helper agent-send.sh was not found under any framework install home ` +
+      `(${homes.map((h) => join(h, 'tools', 'tmux', 'agent-send.sh')).join('; ')}). ` +
+      `Verify the framework install for this host (the helper ships with the framework ` +
+      `config home; the brain home carries fleet state, not tools) and have an authorized ` +
+      `operator restore it if missing.`,
+  };
+}
+
 function helperFailureGuidance(reason: string): string {
-  return `${reason}. Run \`mosaic update --repair-tools\` to restore the supported current-version helper and TOOLS contract, then retry exact-member composition; no active context or session was rewritten.`;
+  // stack#1380 M5a: `mosaic update --repair-tools` is a forbidden remedy on the
+  // affected estate (and wrong for a layout/missing-helper failure). Name the
+  // actual recovery shape instead.
+  return `${reason}. Verify the framework install provides tools/tmux/agent-send.sh under the framework config home and that the roster resolves (split-home layouts symlink the roster into the brain); contact the operator if it persists; no active context or session was rewritten.`;
 }
 
 export function resolveFleetIdentity(
@@ -278,9 +325,15 @@ export function resolveFleetIdentity(
   localHost: string = shortHostname(),
 ): FleetIdentityResult {
   if (!requestedName) return { ok: true };
-  const agentSendPath = join(mosaicHome, 'tools', 'tmux', 'agent-send.sh');
-  const helperError = validateAgentSendHelper(agentSendPath, mosaicHome);
-  if (helperError) return { ok: false, error: helperFailureGuidance(helperError) };
+  const helper = resolveAgentSendHelper(mosaicHome);
+  if (helper.error) return { ok: false, error: helperFailureGuidance(helper.error) };
+  const agentSendPath = helper.path;
+
+  // Split-home layouts unify the roster by symlinking
+  // <configHome>/fleet/roster.yaml -> <brain>/fleet/roster.yaml. The secure
+  // read resolves that framework-created symlink when the brain is a
+  // sanctioned target root (stack#1380 M1).
+  const rosterSymlinkRoots = [resolveBrainHome(mosaicHome)];
 
   let rosterPath: string;
   try {
@@ -301,7 +354,10 @@ export function resolveFleetIdentity(
   let roster: FleetRoster;
   try {
     roster = parseFleetRosterV1(
-      readRegularFileSecure(rosterPath, { root: mosaicHome }).content.toString('utf8'),
+      readRegularFileSecure(rosterPath, {
+        root: mosaicHome,
+        symlinkTargetRoots: rosterSymlinkRoots,
+      }).content.toString('utf8'),
       rosterPath.endsWith('.json') ? 'json' : 'yaml',
     );
   } catch (error) {
@@ -399,7 +455,9 @@ function boundedContractDigest(
 }
 
 function replacementGuidance(): string {
-  return `Run \`mosaic update --repair-tools\` to make a digest-qualified backup and restore the supported current-version TOOLS contract, then have an authorized operator explicitly relaunch the exact roster member. The active context was not rewritten.`;
+  // stack#1380 M5a: never recommend the forbidden --repair-tools remedy from
+  // error text; name the operator-verified recovery shape instead.
+  return `Verify the installed TOOLS contract against the framework source with an authorized operator (the installed file must byte-match the supported current version) and have the operator explicitly relaunch the exact roster member. The active context was not rewritten.`;
 }
 
 /** Detect preserved installed TOOLS.md drift without changing it. */