claude --continue ignores ANTHROPIC_DEFAULT_OPUS_MODEL, resumes on 200K instead of configured 1M — wastes tokens on failed context load

Problem

When resuming a session with claude --continue, the CLI restores the model stored at session creation time instead of respecting the current ANTHROPIC_DEFAULT_OPUS_MODEL env var. If the original session was created before configuring claude-opus-4-6[1m], continuing it silently puts the user on the 200K context version.

Reproduction

1. Set ANTHROPIC_DEFAULT_OPUS_MODEL=claude-opus-4-6[1m] in ~/.claude/settings.json env block
2. Open a project that has an older session (created before this env var was set)
3. Run claude --continue → resume full session
4. Hit /model — observe option 5 "Opus 4.6 ✔" is selected (200K), NOT option 1 "Default — Opus 4.6 with 1M context"
5. Try to work → immediately hit "Context limit reached" because you're on 200K

Expected Behavior

--continue should either:

• Upgrade the model to match the current ANTHROPIC_DEFAULT_OPUS_MODEL (preferred)
• Or at minimum warn when the stored session model differs from the configured default

Current Behavior

--continue silently uses the stored claude-opus-4-6 (200K) model, ignoring the user's explicit configuration of claude-opus-4-6[1m] (1M). The user must manually /model → select option 1 after every --continue on older sessions.

Impact

Every --continue on a pre-1M session silently degrades to 200K context. The user configured the env var specifically to prevent this, but --continue bypasses it. This is especially confusing because new sessions correctly use 1M — only resumed sessions break.

Environment

• Claude Code v2.1.152
• macOS 24.6.0
• ANTHROPIC_DEFAULT_OPUS_MODEL=claude-opus-4-6[1m] in ~/.claude/settings.json env block