Advisor tool returns advisor_tool_result_error "unavailable" on Claude Max (OAuth), Claude Code 2.1.301

Environment: Claude Code 2.1.301 (installed via npm under nvm), Linux, Claude Max plan, OAuth login (no ANTHROPIC_API_KEY / AUTH_TOKEN set).
Configured advisor: "opus" (shown as Opus 5.5 after /advisor opus).

Behavior

The model issues a server_tool_use block named "advisor", and the server returns an advisor_tool_result containing advisor_tool_result_error with error_code: "unavailable". The request itself succeeds (end_turn) and the model continues without advice. 100% reproducible, including from a neutral directory.

Repro

# from ~
claude -p --model claude-sonnet-4-6 --advisor opus --output-format stream-json --verbose "Before answering, consult the advisor: JSON or SQLite for a small file-sync CLI's state file? Two sentences."

Request IDs (all return the same error)

• req_011Cg4axRd54dsgJUWCYCND7 — Sonnet 4.6 main, normal config
• req_011Cg4bXtQYqxFuUeLjwxD1T — Sonnet 4.6 main, minimal config (only credentials + advisorModel, via CLAUDE_CONFIG_DIR)
• req_011Cg4bhR3HsmGo58krP9ADa — Haiku 4.5 main + Opus advisor

Ruled out

Outdated version (upgraded from 2.1.282), provider/env overrides (no Bedrock/Vertex/Foundry vars, no base URL), project and global context (identical failure with a minimal config), main model (Sonnet 4.6 and Haiku 4.5 both fail), advisor model (--advisor sonnet also fails). Tests were run within about 15 minutes of each other on 2026-10-15; I'll add a later retry result if it differs.

Other observation

The stream's rate_limit_event shows overageStatus: "rejected" with overageDisabledReason: "out_of_credits". Unknown if that's related.

Questions

Is the advisor enabled for Max accounts? If so, what does "unavailable" indicate for this account, and is there anything I need to enable?