diff --git a/apps/desktop/renderer-architecture.json b/apps/desktop/renderer-architecture.json
index b71da97554..6c76a0ebad 100644
--- a/apps/desktop/renderer-architecture.json
+++ b/apps/desktop/renderer-architecture.json
@@ -71,6 +71,7 @@
     "src/renderer/locales/onboarding-copy.ts",
     "src/renderer/locales/permission-center-copy.ts",
     "src/renderer/locales/plan-mode-copy.ts",
+    "src/renderer/locales/session-collaboration-copy.ts",
     "src/renderer/locales/settings-bot-copy.ts",
     "src/renderer/locales/settings-daily-review-copy.ts",
     "src/renderer/locales/settings-data-copy.ts",
@@ -113,6 +114,7 @@
     "src/renderer/remote-project-directory-dialog.tsx",
     "src/renderer/scroll-motion-policy.ts",
     "src/renderer/session-catalog-state.ts",
+    "src/renderer/session-collaboration-dialog.tsx",
     "src/renderer/session-copy-attempt.ts",
     "src/renderer/session-error-presentation.ts",
     "src/renderer/session-event-health.ts",
@@ -121,6 +123,7 @@
     "src/renderer/session-read-state.ts",
     "src/renderer/session-status-presentation.ts",
     "src/renderer/session-trace-refresh.ts",
+    "src/renderer/session-turn-request-composer.tsx",
     "src/renderer/session-workspace-actions.ts",
     "src/renderer/session-workspace-errors.ts",
     "src/renderer/settings/about-settings-page.tsx",
@@ -234,6 +237,7 @@
     "src/renderer/use-new-task-choice.ts",
     "src/renderer/use-onboarding-snapshot.ts",
     "src/renderer/use-project-context.ts",
+    "src/renderer/use-session-collaboration-dialog.ts",
     "src/renderer/use-session-setting-intent.ts",
     "src/renderer/use-settings-modal.ts",
     "src/renderer/use-shell-appearance.ts",
@@ -583,7 +587,7 @@
           "react": 1
         },
         "importSpecifiers": 39,
-        "nonTriviaTokens": 3829
+        "nonTriviaTokens": 3877
       },
       "src/renderer/app-shell-overlays.tsx": {
         "importDeclarations": 14,
@@ -861,7 +865,7 @@
         "nonTriviaTokens": 1425
       },
       "src/renderer/app-shell.tsx": {
-        "importDeclarations": 103,
+        "importDeclarations": 107,
         "bridgePaths": {
           "window.maka.app.installUpdate": 1,
           "window.maka.app.retryUpdateDownload": 1,
@@ -928,6 +932,7 @@
           "useOnboardingSnapshot": 1,
           "usePlanModeState": 1,
           "useRef": 25,
+          "useSessionCollaborationDialog": 1,
           "useSessionEventHealthPolling": 1,
           "useSessionNavigationReads": 1,
           "useSessionSettingIntent": 2,
@@ -994,6 +999,7 @@
           "./live-content-seed": 1,
           "./live-turn-reconciler": 1,
           "./locales/conversation-copy": 1,
+          "./locales/session-collaboration-copy": 1,
           "./locales/shell-copy": 1,
           "./locales/shell-remaining-copy.js": 1,
           "./model-connection-errors": 1,
@@ -1002,6 +1008,8 @@
           "./pending-session-view": 1,
           "./plan-mode-panel": 1,
           "./scroll-motion-policy": 1,
+          "./session-collaboration-dialog": 1,
+          "./session-turn-request-composer.js": 1,
           "./session-workspace-errors": 1,
           "./settings/provider-brand-marks": 1,
           "./settings/provider-display": 1,
@@ -1018,6 +1026,7 @@
           "./use-new-task-choice": 1,
           "./use-onboarding-snapshot": 1,
           "./use-project-context": 1,
+          "./use-session-collaboration-dialog": 1,
           "./use-session-setting-intent": 1,
           "./use-settings-modal": 1,
           "./use-shell-appearance": 1,
@@ -1054,8 +1063,8 @@
           "@maka/ui/icons": 1,
           "react": 1
         },
-        "importSpecifiers": 183,
-        "nonTriviaTokens": 15553
+        "importSpecifiers": 187,
+        "nonTriviaTokens": 15912
       },
       "src/renderer/use-app-shell-composer-quotes.ts": {
         "importDeclarations": 3,
@@ -1851,6 +1860,17 @@
           "@maka/core/ui-locale": 1
         }
       },
+      "src/renderer/locales/session-collaboration-copy.ts": {
+        "bridgePaths": {},
+        "environmentCapabilities": {},
+        "hookCalls": {},
+        "lifecycleMethods": {},
+        "unresolvedDependencies": 0,
+        "actionFactories": [],
+        "dependencyPaths": {
+          "@maka/core/ui-locale": 1
+        }
+      },
       "src/renderer/locales/settings-bot-copy.ts": {
         "bridgePaths": {},
         "environmentCapabilities": {},
@@ -2439,6 +2459,42 @@
           "react": 1
         }
       },
+      "src/renderer/session-collaboration-dialog.tsx": {
+        "bridgePaths": {
+          "window.maka.localRuntimeHostRemoteAccess.getSnapshot": 2,
+          "window.maka.sessionCollaboration.decideTurnRequest": 1,
+          "window.maka.sessionCollaboration.getAccess": 1,
+          "window.maka.sessionCollaboration.getTurnRequests": 1,
+          "window.maka.sessionCollaboration.importInvitation": 1,
+          "window.maka.sessionCollaboration.prepareInvitation": 1,
+          "window.maka.sessionCollaboration.revokeGrant": 1,
+          "window.maka.sessionCollaboration.revokePrincipal": 1
+        },
+        "environmentCapabilities": {
+          "navigator.clipboard.writeText": 1,
+          "window.clearTimeout": 1,
+          "window.setTimeout": 1
+        },
+        "hookCalls": {
+          "useEffect": 1,
+          "useState": 8,
+          "useToast": 2,
+          "useUiLocale": 2
+        },
+        "lifecycleMethods": {},
+        "unresolvedDependencies": 0,
+        "actionFactories": [],
+        "dependencyPaths": {
+          "./locales/session-collaboration-copy.js": 1,
+          "./session-turn-request-composer.js": 1,
+          "@astryxdesign/core": 1,
+          "@astryxdesign/core/Dialog": 1,
+          "@astryxdesign/core/Layout": 1,
+          "@maka/runtime-host/protocol": 1,
+          "@maka/ui": 1,
+          "react": 1
+        }
+      },
       "src/renderer/session-copy-attempt.ts": {
         "bridgePaths": {},
         "environmentCapabilities": {
@@ -2545,6 +2601,33 @@
           "@maka/core/events": 1
         }
       },
+      "src/renderer/session-turn-request-composer.tsx": {
+        "bridgePaths": {
+          "window.maka.sessionCollaboration.acknowledgeTurnRequest": 1,
+          "window.maka.sessionCollaboration.getTurnRequests": 2,
+          "window.maka.sessionCollaboration.requestTurn": 1
+        },
+        "environmentCapabilities": {
+          "window.clearTimeout": 1,
+          "window.setTimeout": 1
+        },
+        "hookCalls": {
+          "useEffect": 1,
+          "useRef": 2,
+          "useState": 6,
+          "useToast": 1,
+          "useUiLocale": 1
+        },
+        "lifecycleMethods": {},
+        "unresolvedDependencies": 0,
+        "actionFactories": [],
+        "dependencyPaths": {
+          "./locales/session-collaboration-copy.js": 1,
+          "@maka/runtime-host/protocol": 1,
+          "@maka/ui": 1,
+          "react": 1
+        }
+      },
       "src/renderer/session-workspace-actions.ts": {
         "bridgePaths": {
           "window.maka.sessions.queryCancelledMessages": 1
@@ -3877,7 +3960,7 @@
         "hookCalls": {
           "useEffect": 1,
           "useMountedRef": 1,
-          "useState": 9,
+          "useState": 10,
           "useToast": 1,
           "useUiLocale": 1
         },
@@ -3886,7 +3969,9 @@
         "actionFactories": [],
         "dependencyPaths": {
           "../../preload/bridge-contract.js": 1,
+          "../locales/session-collaboration-copy.js": 1,
           "../locales/settings-projects-copy.js": 1,
+          "../session-collaboration-dialog.js": 1,
           "./password-input.js": 1,
           "./runtime-host-connection-code-dialog.js": 1,
           "./runtime-host-management-dialog.js": 1,
@@ -4928,6 +5013,19 @@
           "react": 1
         }
       },
+      "src/renderer/use-session-collaboration-dialog.ts": {
+        "bridgePaths": {},
+        "environmentCapabilities": {},
+        "hookCalls": {
+          "useState": 1
+        },
+        "lifecycleMethods": {},
+        "unresolvedDependencies": 0,
+        "actionFactories": [],
+        "dependencyPaths": {
+          "react": 1
+        }
+      },
       "src/renderer/use-session-setting-intent.ts": {
         "bridgePaths": {},
         "environmentCapabilities": {},
@@ -5263,7 +5361,8 @@
         "unresolvedDependencies": 0,
         "actionFactories": [],
         "dependencyPaths": {
-          "../preload/bridge-contract.js": 1
+          "../preload/bridge-contract.js": 1,
+          "../shared/runtime-host-identity.js": 1
         }
       },
       "src/renderer/workhub-coordination-port.ts": {
diff --git a/apps/desktop/scripts/check-renderer-architecture.mjs b/apps/desktop/scripts/check-renderer-architecture.mjs
index 548c3128af..68fe532f16 100644
--- a/apps/desktop/scripts/check-renderer-architecture.mjs
+++ b/apps/desktop/scripts/check-renderer-architecture.mjs
@@ -18,8 +18,9 @@
  */
 
 import { execFileSync } from 'node:child_process';
-import { existsSync, readFileSync, readdirSync, writeFileSync } from 'node:fs';
+import { existsSync, mkdtempSync, readFileSync, readdirSync, rmSync, writeFileSync } from 'node:fs';
 import { builtinModules } from 'node:module';
+import { tmpdir } from 'node:os';
 import { dirname, join, relative, resolve, sep } from 'node:path';
 import { fileURLToPath, pathToFileURL } from 'node:url';
 import { parse } from '@babel/parser';
@@ -2516,6 +2517,46 @@ export function checkRendererArchitecture({
   return violations.sort();
 }
 
+// The monotonic-debt ratchet must measure debt against what the base commit's
+// source tree *actually* contained, not against the numbers its ledger happened
+// to record. A ledger that under-reports its own tree (for example, one
+// generated on a branch that predated files already merged into main) would
+// otherwise make a faithful baseline correction look like brand-new debt and
+// wedge the ledger permanently. We materialize the base tree and re-derive its
+// debt, keeping the base ledger only as the source of policy fields (hook
+// transitions, growth directories, root-debt key set, ownership).
+function deriveBaseTreeConfig(repoRoot, desktopRoot, base, baseCommittedConfig) {
+  const scratch = mkdtempSync(join(tmpdir(), 'renderer-arch-base-'));
+  const worktreePath = join(scratch, 'tree');
+  try {
+    execFileSync('git', ['worktree', 'add', '--detach', worktreePath, base], {
+      cwd: repoRoot,
+      encoding: 'utf8',
+      stdio: ['ignore', 'pipe', 'pipe'],
+    });
+    const baseDesktopRoot = resolve(worktreePath, relative(repoRoot, desktopRoot));
+    return generateArchitectureConfig(baseDesktopRoot, baseCommittedConfig);
+  } finally {
+    try {
+      execFileSync('git', ['worktree', 'remove', '--force', worktreePath], {
+        cwd: repoRoot,
+        stdio: 'ignore',
+      });
+    } catch {
+      try {
+        execFileSync('git', ['worktree', 'prune'], { cwd: repoRoot, stdio: 'ignore' });
+      } catch {
+        // Ignore prune failures; the scratch removal below is the real cleanup.
+      }
+    }
+    try {
+      rmSync(scratch, { recursive: true, force: true });
+    } catch {
+      // Best-effort cleanup of the scratch directory.
+    }
+  }
+}
+
 function loadBaseConfig(repoRoot, desktopRoot, base) {
   if (!base) return { baseConfig: undefined, introducedLedger: false };
   const relativeConfig = normalizePath(relative(repoRoot, join(desktopRoot, 'renderer-architecture.json')));
@@ -2557,13 +2598,30 @@ function loadBaseConfig(repoRoot, desktopRoot, base) {
     throw new Error(`base ledger is missing at ${base}:${relativeConfig}`);
   }
 
+  let baseCommittedConfig;
   try {
-    return { baseConfig: JSON.parse(source), introducedLedger: false };
+    baseCommittedConfig = JSON.parse(source);
   } catch (error) {
     throw new Error(
       `base ledger is invalid JSON at ${base}:${relativeConfig}: ${error instanceof Error ? error.message : String(error)}`,
     );
   }
+
+  try {
+    return {
+      baseConfig: deriveBaseTreeConfig(repoRoot, desktopRoot, base, baseCommittedConfig),
+      introducedLedger: false,
+    };
+  } catch (error) {
+    // If the base tree cannot be materialized or analyzed (e.g. git worktree is
+    // unavailable), fall back to the committed base ledger so the ratchet still
+    // runs. This restores the pre-fix behavior rather than crashing the check.
+    console.warn(
+      `Renderer architecture check: could not derive base tree debt at ${base}; ` +
+        `falling back to the committed base ledger. (${error instanceof Error ? error.message : String(error)})`,
+    );
+    return { baseConfig: baseCommittedConfig, introducedLedger: false };
+  }
 }
 
 function parseCliArguments(args) {