fix(cloud-agent): hide no-op preparation rows so 'Environment prepared' shows only on cold starts

[eshurakov]

Problem

"Environment prepared" appeared beneath every message in both the web and mobile cloud-agent chat UIs, not just on cold starts.

Root cause

ensureWrapper runs on every message delivery and unconditionally emits the preparation progress markers sandbox_provision (cloudflare-agent-sandbox.ts:529) and sandbox_boot (:639), even when reusing a warm sandbox/wrapper. The first onProgress call creates an attempt_started snapshot (preparation-progress.ts:77), and executeDirectly always finalizes the recorder as completed on success (CloudAgentSession.ts:3229). So every message produced a completed attempt, which the UI rendered as "Environment prepared" (PreparationRow.tsx / PreparationDrawer.tsx on web; PreparationGroup on mobile).

Fix

Surface the indicator only for genuine cold starts by hiding no-op completed attempts at the UI layer (the option chosen for this change):

• A completed attempt whose steps are only the always-on synthetic markers (sandbox_provision, sandbox_boot) is treated as a warm-reuse no-op and hidden.
• A real cold start always records at least one substantive step (cloning, workspace_setup, kilo_session, kilo_server, …), so it stays visible.
• Running and failed attempts are never hidden, so live cold-start progress and failures remain visible.

Shared SDK

• apps/web/src/lib/cloud-agent-sdk/preparation-attempts.ts — new isNoOpCompletedPreparationAttempt() + SYNTHETIC_PREPARATION_STEPS (single source of truth for both apps).
• apps/web/src/lib/cloud-agent-sdk/preparation-attempts.test.ts — canonical tests.
• apps/web/src/lib/cloud-agent-sdk/index.ts — exports the predicate.
• apps/web/src/components/cloud-agent-next/preparation-summary.ts — replaced the local copy with a re-export so existing web import sites are unchanged.

Web

• apps/web/src/components/cloud-agent-next/CloudChatPage.tsx — preparationByMessageId skips no-op completed attempts, so neither StaticMessages nor DynamicMessages render the row.

Mobile

• apps/mobile/src/components/agents/session-transcript.ts — mergeSessionTranscript filters no-op completed attempts before grouping; this is the single chokepoint for both inline and orphaned attempts.
• apps/mobile/vitest.config.ts — added the cloud-agent-sdk/preparation-attempts alias, matching the existing context-usage/cli-model/message-id/remote-model-order pattern (vitest does not honor the cloud-agent-sdk/* tsconfig path; Metro does, so runtime is unaffected).
• apps/mobile/src/components/agents/session-transcript.test.ts — existing fixtures upgraded to realistic cold-start shapes (a cloning step so they remain visible); added a warm-reuse no-op test and a running-attempt-stays-visible test.

Verification

• Mobile: pnpm test — 137 files / 927 tests pass. pnpm lint and pnpm typecheck clean for changed files (pre-existing unrelated errors elsewhere).
• Web: pnpm run lint clean (0 errors). Web Jest (pnpm test) could not run in this environment — its global setup requires PostgreSQL. tsgo --noEmit exceeded the sandbox time budget (large app, no errors emitted before timeout). The web change is a behavior-preserving refactor (predicate moved to the SDK and re-exported), so please run pnpm test/pnpm typecheck locally to confirm.
• pnpm format:changed and git diff --check clean.

Known limitation

A warm-reuse attempt briefly shows "Preparing environment" while running before it completes and gets hidden. If that flicker is noticeable, the durable fix is to gate onProgress to genuine cold work in ensureWrapper (backend option).

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Re-reviewed the shared isNoOpCompletedPreparationAttempt predicate and its wiring into the web and mobile chat UIs at the current HEAD (0adffc4); the logic remains correct, well-tested, and consistently applied across both platforms with no evidence of runtime errors, logic bugs, or breaking API changes.

Files Reviewed (8 files)

• apps/web/src/lib/cloud-agent-sdk/preparation-attempts.ts
• apps/web/src/lib/cloud-agent-sdk/preparation-attempts.test.ts
• apps/web/src/lib/cloud-agent-sdk/index.ts
• apps/web/src/components/cloud-agent-next/preparation-summary.ts
• apps/web/src/components/cloud-agent-next/CloudChatPage.tsx
• apps/mobile/src/components/agents/session-transcript.ts
• apps/mobile/src/components/agents/session-transcript.test.ts
• apps/mobile/vitest.config.ts

Previous Review Summary (commit ce75931)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit ce75931)

Status: No Issues Found | Recommendation: Merge

Executive Summary

Reviewed the shared isNoOpCompletedPreparationAttempt predicate and its wiring into the web and mobile chat UIs; the logic is correct, well-tested, and consistently applied across both platforms with no evidence of runtime errors, logic bugs, or breaking API changes in the actual PR diff (verified against the true merge-base to exclude unrelated base-branch drift).

Files Reviewed (8 files)

• apps/web/src/lib/cloud-agent-sdk/preparation-attempts.ts
• apps/web/src/lib/cloud-agent-sdk/preparation-attempts.test.ts
• apps/web/src/lib/cloud-agent-sdk/index.ts
• apps/web/src/components/cloud-agent-next/preparation-summary.ts
• apps/web/src/components/cloud-agent-next/CloudChatPage.tsx
• apps/mobile/src/components/agents/session-transcript.ts
• apps/mobile/src/components/agents/session-transcript.test.ts
• apps/mobile/vitest.config.ts

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_{Reviewed by claude-sonnet-5 · Input: 30 · Output: 4.2K · Cached: 615.3K}

_{Review guidance: REVIEW.md from base branch main}