feat(web): steer follow-ups by default

[mkantautas]

What Changed

Follow-up behavior defaults to Steer instead of Queue. The user guide's "Send while the agent is working" section now describes Steer first and Queue as the option.

Why

A message typed while Claude Code works goes to Claude, which reads it after its current tool call. Nothing waits in a separate queue and nothing needs a second click. T3 Code's Steer does the same for Claude: sendTurn during a running turn puts the message straight into the live SDK loop (ClaudeAdapter.ts, "A sendTurn while a real turn is running is a steer"). Queue adds a dashed bubble with Send now, holds while an approval or question is open, and a message Stop returned or a failed send restored waits for Send now.

#12100 is triaged as a bug, and #12119 makes Queue wait for the end of the turn. After that lands, a message sent under the default waits for the whole turn, while under Claude Code it would be read after the next tool call. Queue stays one setting away, and mod+Enter still does the opposite for one message.

Client settings save as a full snapshot, so a client that saved queue keeps it. The new default reaches new installs and clients that have not saved settings since the option shipped.

UI Changes

No layout change. The Follow-up behavior select opens on Steer, and its reset button now appears when Queue is picked.

Checklist

• This PR is small and focused
• I explained what changed and why

Verified with vp test run src/settings.test.ts in packages/contracts (146 passed), vp test run src/components/settings src/hooks/useSettings in apps/web (474 passed), vp lint and vp fmt --check on the changed files, and the contracts typecheck.

Summary by CodeRabbit

• New Features
  • During an active turn, new messages are sent to the agent immediately by default and join the work in progress.
  • Choose Queue in Follow-up behavior to hold messages until the agent’s next tool call or the end of the turn. If a message is already waiting to send, new messages queue behind it.
  • This setting applies to the current client; messages already queued keep their place.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR changes the default handling of follow-up messages during active agent turns from queuing them to sending them immediately, affecting new or otherwise unset client settings. The change is small and preserves the Queue option, but product-default changes require human review.

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📝 Walkthrough

Walkthrough

The default followUpBehavior changes from "queue" to "steer". The settings test and composer documentation reflect this change. Both options remain accepted.

Changes

Follow-up behavior

Layer / File(s)	Summary
Default and documented behavior packages/contracts/src/settings.ts, packages/contracts/src/settings.test.ts, docs/user/composer.md	The settings schema now defaults to "steer". The test and composer documentation describe immediate steering as the default. The "queue" and "steer" options remain accepted.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~4 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to b149d

New users receive the Steer default, while users who selected Queue retain it. No merge-blocking issue is established.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 80e0c

New and unsaved clients will send follow-ups into a running agent turn by default. Saved Queue preferences and input validation remain intact, but the behavior of a direct follow-up while an approval is pending needs confirmation.

Retained concerns

• Medium · security · inferred: The new default routes running-turn follow-ups around the queue’s explicit approval and question hold. Whether the receiving turn preserves that boundary for direct submissions is unverified; this is an ordering concern, not a verified approval bypass.

Security review details

Security Blast Radius

• inferred — Exposure is limited to clients using the decoded default while sending follow-ups to their running agent thread; clients with an explicit Queue setting retain queued delivery.

Trust Boundaries and Controls

• observed — The queue treats pending approvals and questions as delivery blockers. The inspected direct client path has input validation and local reentrancy guards, but those checks do not establish how the receiving turn handles a pending approval.

Resilience and Maintainability Implications

• inferred — Direct-send draft restoration does not by itself establish duplicate suppression if a turn-start request reached the server before a failure was reported. No resulting duplicate or security impact is verified.

Hardening Proposals

• proposed — Confirm receiving-turn behavior for direct follow-ups during approvals and after ambiguous turn-start failures; if it does not preserve the intended ordering, enforce that condition at the turn boundary.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: Steer is now the default follow-up behavior.
Description check	✅ Passed	The description explains what changed, why it changed, the UI impact, compatibility behavior, and verification steps. It is mostly complete, but it does not include the before/after screenshots reques…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @docs/user/composer.md:
- Around line 37-46: Update the running-turn message behavior description in the
composer documentation to clarify that immediate sending is not unconditional:
when a queued message is sending or will send automatically, it goes first and
the new message follows.

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• packages/contracts/src/settings.test.ts
• packages/contracts/src/settings.ts

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[juliusmarminge]

Note

This comment is posted by Julius' dot

Closing for missing product-direction approval. #12100 approves repairing Queue so it waits for the current turn to end; it does not approve changing the default to Steer. Please agree on that default change with maintainers in an Ideas discussion before requesting reconsideration.