Opus 4.6 on Bedrock excluded from 1M context window

Description

Claude Code CLI v2.1.77 does not enable the 1M context window for Opus 4.6 when running on AWS Bedrock, even though:

• The v2.1.75 changelog states 1M context is available for Opus 4.6
• The general eligibility function (onq()) recognizes opus-4-6 as 1M-eligible
• The CLAUDE_CODE_EXTRA_BODY env var correctly passes the anthropic_beta: ["context-1m-2025-08-07"] header

Root Cause (from binary analysis)

The CLI's context window resolver (oY()) has 4 code paths:

1. [1m] in model ID → 1M
2. Provider max_input_tokens metadata → use value
3. Beta header context-1m-2025-08-07 + eligible model → 1M
4. Fallback → 200K

On Bedrock, a separate function (Liq()) handles eligibility and grants 1M only to Sonnet 4.6, not Opus. This overrides the general eligibility check. Additionally, Bedrock's list-foundation-models metadata lacks max_input_tokens, so path 2 falls through, and no [1m] model variant exists on Bedrock, so path 1 doesn't apply either.

Steps to Reproduce

1. Configure Claude Code CLI to use Opus 4.6 on Bedrock (us.anthropic.claude-opus-4-6-v1)
2. Set CLAUDE_CODE_EXTRA_BODY='{"anthropic_beta":["context-1m-2025-08-07"]}'
3. Restart CLI
4. Run /context — shows 200K limit

Expected Behavior

/context should report ~1M token limit for Opus 4.6 on Bedrock, matching the behavior for Sonnet 4.6 on Bedrock and Opus 4.6 on the Anthropic API.

Environment

• CLI version: 2.1.77
• Model: us.anthropic.claude-opus-4-6-v1 (Bedrock cross-region inference profile)
• Provider: AWS Bedrock
• Platform: macOS (Darwin, arm64)