[DOCS] Critical mismatch between advertised `Explore` agent optimization (Haiku) and actual default behavior (Opus 4.5 inheritance)

Documentation Type

Unclear/confusing documentation

Documentation Location

Comparison of the "Built-in subagents" documentation page against the internal Task tool system prompt and the /model default setting (Opus 4.5).

Section/Topic

The default model configuration and optimization guidelines for the Explore built-in subagent.

Current Documentation

• Developer Documentation: States for the Explore agent: "Model: Haiku (fast, low-latency)" and "A fast, read-only agent optimized for searching and analyzing codebases."
• Internal System Prompt: States for the Task tool: "model: Optional model to use for this agent. If not specified, inherits from parent."
• CLI Configuration: The /model command identifies "Opus 4.5" as the "default (recommended)" model for the main conversation.

What's Wrong or Missing?

There is a significant contradiction between the "low-latency" promise and the system's execution logic.

Because the Task tool inherits the parent model by default, and the parent model defaults to Opus 4.5, the Explore subagent will execute using Opus 4.5 unless the model explicitly overrides it. This creates three major issues:

1. Extreme Cost Inefficiency: Opus 4.5 is the highest-tier model. Using it for codebase exploration (searching, indexing, and reading files) is orders of magnitude more expensive than the "optimized" Haiku behavior mentioned in the docs.
2. High Latency: Users expecting a "fast" agent as per documentation will experience the significantly higher latency of Opus 4.5 reasoning.
3. Logic Gap: The AI is instructed that Explore is optimized for Haiku in the docs, but its system prompt does not reinforce this, leading to a failure to proactively select the most efficient model for the task.

Suggested Improvement

The internal system prompt for the Task tool should be updated to decouple Explore from the parent model's default.

Suggested change to the system prompt:

"For subagent_type: Explore, the agent SHOULD default to model: haiku to maintain the speed and cost-efficiency promised in the documentation. Only use the parent's model (Opus 4.5) if the specific exploration task requires the highest level of reasoning complexity."

Alternatively, if inheritance is preferred for quality, the documentation must be updated to explicitly warn users:

"Warning: While optimized for Haiku, the Explore agent inherits your session's model. If you are using the default Opus 4.5, exploration tasks will incur higher costs and latency."

Impact

High - Prevents users from using a feature

Additional Context

• Observed in Claude Code Version 2.1.4.
• This issue is exacerbated by Opus 4.5 being the new "recommended" default, as it makes the "low-latency" description of the Explore agent technically false under default settings.