Tasks: Server-side input queue for auto-resume

coderd/aitasks.go と task_pending_inputs の新しい migration から始め、次に参照されている lifecycle RFC と既存の job-system integration を確認してください。/send が一時停止中の task をどのように処理するか、また workspace の準備完了状態と配信がどのように表現されるかを追跡してください。キューに入れられたメッセージが ID 付きで 202 を返し、自動的な workspace 起動後に配信され、指定どおりに失敗状態を記録すれば完了です。

Repo: coder/coder

Scope: Allow /send to accept messages for paused tasks, queue them, and deliver asynchronously.

Note: Consider ACP (Agent Communication Protocol) impact before implementation. ACP standardization may influence message queue design and delivery mechanism.

Changes:

• Create task_pending_inputs table:
  • id UUID PRIMARY KEY
  • task_id UUID REFERENCES tasks(id)
  • content TEXT NOT NULL
  • status TEXT NOT NULL DEFAULT 'pending'
  • created_at TIMESTAMPTZ NOT NULL
  • delivered_at TIMESTAMPTZ
  • error TEXT
• Modify /send to accept messages for paused tasks
• Return 202 Accepted with message ID for queued messages
• Background worker: trigger workspace start, poll for ready, deliver message, update status
• Handle failures (build fails, delivery fails) with appropriate status updates

Benefits beyond auto-resume (per RFC):

• Solves Terraform env var length limits for long prompts
• Unifies initial prompt + follow-up delivery path
• Enables prompt modification until task starts
• Enables prebuilds for tasks

Files:

• New migration for task_pending_inputs table
• coderd/aitasks.go (modified send handler)
• New background worker or integration with existing job system

Acceptance criteria:

• /send to paused task returns 202 and queues message
• Workspace automatically starts
• Message delivered when workspace ready
• Failure states handled gracefully with status tracking
• Direct API consumers no longer need orchestration logic

Dependencies:

• GA phase complete
• ACP (Agent Communication Protocol) evaluation (does not block, but may influence design)

References:

• PRD: Start/Pause/Resume the Task Workspace
• RFC: Tasks: Start/Pause/Resume Lifecycle: Auto-Resume Option B