test(desktop): stabilize collaboration mode updates during Runtime Host session churn #2545

Summary

The Desktop E2E test slash suggestions: project gating, collaboration modes, and Deep Research filtering intermittently fails while switching a Session to Plan mode. The Runtime Host Session identity keeps changing throughout the existing bounded poll, so sessions:setCollaborationMode never converges.

This occurred on a PR that only changes activity-card rendering and its E2E coverage. The other E2E shard and all non-E2E CI lanes passed, which points to a timing-sensitive Runtime Host lifecycle race rather than a deterministic regression in that PR.

Observed behavior

Error: page.evaluate: Error: Error invoking remote method 'sessions:setCollaborationMode': DesktopRuntimeHostClientError: Runtime Host Session kept changing during update: dd1f8626-2952-4128-943e-ab8dca42ed8a

• Test: apps/desktop/e2e/composer-skill-invocation.spec.ts:44
• Failing poll: apps/desktop/e2e/composer-skill-invocation.spec.ts:82
• CI evidence: https://github.com/maka-agent/maka-agent/actions/runs/31290267297/job/93186128007
• Affected PR: feat(desktop): keep activity headers reachable #2542

The shard result was 19 passed and 1 failed. The sibling E2E shard passed.

Expected behavior

A collaboration-mode update should either:

• target a stable Runtime Host Session and complete; or
• cross an explicit readiness/reconnect boundary and retry against the canonical replacement Session.

The caller should not exhaust its bounded wait because Session identity continues changing without a stable point.

Investigation scope

• Identify why the Session is repeatedly replaced while this test updates collaboration mode.
• Determine whether the production client needs a canonical reconnect-and-retry contract or the E2E fixture is missing a real readiness boundary.
• Preserve bounded failure behavior; do not hide the race with an unbounded retry or a fixed delay.
• Add a deterministic regression at the layer that owns Session replacement and update routing.

Reproduction

npm run e2e --workspace @maka/desktop -- \
  --grep "slash suggestions: project gating, collaboration modes, and Deep Research filtering" \
  --repeat-each=10

Related

• test(desktop): eliminate Runtime Host drain race in side-chat recovery E2E #2543 reports a different Runtime Host lifecycle race (Runtime Host is draining) in side-chat recovery. The symptoms and call paths differ, but the lifecycle ownership may overlap.