Preserve a small task brief across usage-limited account/provider switches

[sudoax0n]

Problem / use case

When one account hits its usage limit, I want to switch to another account or provider in the same T3 conversation and continue with the important decisions and progress intact.

The current portable handoff is fast and small, which is useful. However, it selects whole saved history items within a budget rather than generating a semantic summary. An important constraint or decision from the middle of a long task can therefore be absent from the incoming agent's initial context. The history remains retrievable, but the agent has to recognize which information is missing and fetch it.

Once the outgoing account is already limited, asking that account to write a handoff or compact first is not a reliable recovery step.

Proposed behavior

Offer an opt-in, thread-scoped task brief that is saved and refreshed at meaningful milestones while work is still running. Keep it small and carry it alongside the existing portable handoff when switching accounts/providers.

The brief should retain:

• The current goal and important user constraints.
• Decisions already made and why.
• Completed work, relevant files/artifacts, and checks actually performed.
• Partial or interrupted work, unresolved issues, and the next step.
• References to the supporting messages/activity, plus the last update point so stale state is visible.

On takeover, give the incoming agent the latest brief and instructions to retrieve missing or newer details with t3_thread_read and inspect the current workspace before continuing edits. If no brief exists, the incoming provider should be able to reconstruct one from saved history without requiring a successful response from the limited account.

This should also work for manual switching; automatic fallback is a separate choice. An optional HANDOFF.md export could be useful, but writing a file into the user's repository should not be required.

Smallest useful scope / acceptance criteria

1. A user can enable and inspect a bounded task brief for a thread, including its update point and source references.
2. After account A becomes usage-limited, continuing on account/provider B includes the saved brief without calling A again.
3. Earlier recorded constraints and decisions remain available even when their original messages fall outside the selected transcript items.
4. Partial work and unverified checks are identified accurately; a stale brief is reconciled with newer activity and current files.
5. Existing native resume is used where supported. Portable recovery preserves the current request and does not automatically replay earlier commands or require loading the entire transcript upfront.

Evidence / current behavior

Inspected installation: T3 Code Nightly 0.0.46-nightly.20261010.2922 on Windows. Read-only inspection of one saved handoff found 14 selected history items and 88 omitted items, with approximately 14 KB of formatted context. This illustrates the bounded selection; it is not evidence that a particular decision was lost or that a usage-limit recovery was reproduced.

The portable handoff documentation describes selected intact history, retrieval of omitted items, and the default 16,000-token allowance with conservative byte accounting. The selection implementation prioritizes recent user/assistant items and the first user item, then fills backward within the budget.

Related proposals / tradeoffs

• Option to automatically hand off to a fallback provider when hitting usage limits #15846 proposes automatic fallback when usage limits are hit. This request concerns the task state carried during a switch, including a manual switch.
• Auto-fork thread with distilled context on rate-limit / quota cutoff #15128 proposes distillation and a fresh-thread fork after a quota cutoff. This request focuses on a brief maintained before the cutoff and continued in the existing thread.
• feat(threads): summarize recoverable progress after a failed turn #15982 proposes a user-requested recovery summary after a failed turn. The brief could share that work while also covering proactive account-switch continuity.
• [Bug]: Switching compatible Codex accounts with shared CODEX_HOME uses portable handoff instead of native thread resume #16613 concerns native Codex resume across compatible account instances; that remains preferable when available.

Refreshing a brief can consume model tokens, so updates should be bounded, opt-in, and concentrated at milestones rather than performed on every message. Source references and update points are important because the brief may be incomplete or stale. I am proposing the behavior rather than a specific storage or summarization implementation.