[Bug] SendMessage tool missing despite documented agent resumption workflow

Bug Description
SendMessage tool referenced in Agent tool description but not available

The Agent tool description states: "To continue a previously spawned agent, use SendMessage with the agent's ID or name as the to field — that resumes it with full context."

Each agent invocation also returns an agentId in its result, explicitly prompting: "use SendMessage with to: '' to continue this agent".

However, SendMessage is not present in the available tool list, not in the deferred tool list, and cannot be found via ToolSearch. Calling it would fail.

Impact: Agents cannot be resumed or continued. Every follow-up requires a full cold-start via a new Agent call, defeating the purpose of the agentId return value and making multi-turn agent
workflows significantly more expensive in tokens.

Expected: SendMessage is available as a tool when an agentId has been returned by a prior Agent call.

Actual: SendMessage is not available. The agentId values returned by agents are unusable.

Environment Info

• Platform: darwin
• Terminal: macOS terminal, platform agnostic
• Version: 2.1.98
• Feedback ID: cf6dfaa0-9142-46b4-a955-72bda66e4ad2

Errors

[{"error":"Error: 429 {\"type\":\"error\",\"error\":{\"type\":\"rate_limit_error\",\"message\":\"This request would exceed your account's rate limit. Please try again later.\"},\"request_id\":\"req_011CaB3Zt2Wx4jcN5zNgJ5AR\"}\n    at generate (/$bunfs/root/src/entrypoints/cli.js:11:52623)\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:50:4943)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-18T10:02:43.744Z"},{"error":"Error: 429 {\"type\":\"error\",\"error\":{\"type\":\"rate_limit_error\",\"message\":\"This request would exceed your account's rate limit. Please try again later.\"},\"request_id\":\"req_011CaB3ZxPCU56zMZSA1sa49\"}\n    at generate (/$bunfs/root/src/entrypoints/cli.js:11:52623)\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:50:4943)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-18T10:02:44.555Z"},{"error":"Error: File does not exist. Note: your current working directory is /Users/diego/Dev/github/tradey.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4367:7632)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-18T12:36:18.525Z"},{"error":"Error: Request was aborted.\n    at makeRequest (/$bunfs/root/src/entrypoints/cli.js:50:3448)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-18T14:11:52.808Z"},{"error":"Error: File does not exist. Note: your current working directory is /Users/diego/Dev/github/tradey.\n    at call (/$bunfs/root/src/entrypoints/cli.js:4367:7632)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-18T14:15:13.081Z"},{"error":"Error: 429 {\"type\":\"error\",\"error\":{\"type\":\"rate_limit_error\",\"message\…

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