[BUG] Thinking expander still broken on Opus 4.7 in VSCode extension 2.1.121 (regression of #52046)

Preflight Checklist

• [x] I have searched existing issues
• [x] This is a single bug report
• [x] I am using the latest version of Claude Code

What's Wrong?

Thinking blocks render as "Thought for Xs" in the chat panel but cannot be expanded to view content. Clicking the summary line / chevron does nothing. showThinkingSummaries: true is set in ~/.claude/settings.json and confirmed valid JSON.

This is a continuation of the same bug class as #54348, #51131, #49902, #49757, and the supposedly-fixed #52046. Filing fresh because the regression persists past the close date of #52046 — extension has advanced from 2.1.117 (where #52046 was closed) to 2.1.121, and the symptom is unchanged.

What Should Happen?

Clicking the "Thought for Xs" summary expands an inline block showing the thinking content (live during streaming + after completion). Behavior matches Opus 4.6 and the <details> toggle component still present in the webview bundle.

Steps to Reproduce

1. VSCode 1.117.0, Claude Code extension 2.1.121
2. ~/.claude/settings.json contains "showThinkingSummaries": true at top level
3. Confirm model is claude-opus-4-7[1m] via /model
4. Send any prompt that triggers multi-second thinking (e.g. "think hard about X")
5. Wait for response — "Thought for Xs" header renders
6. Click header / chevron → nothing happens

Reproduces on every turn. Restart of VSCode + restart of Claude Code session both attempted, neither helps.

Environment

• Claude Code for VS Code: 2.1.121
• VSCode: 1.117.0 x64 (commit 10c8e557c8b9f9ed0a87f61f1c9a44bde731c409)
• OS: Windows 11 Home 10.0.26200
• Model: claude-opus-4-7[1m]
• Settings: {"showThinkingSummaries": true, "env": {"MAX_THINKING_TOKENS": "10000", ...}}

Is this a regression?

Yes — same bug class as the closed #52046; persists into 2.1.121.

Last Working Version

Pre-2.1.117 (per #52046's reporter), exact prior-working version unknown.

Related issues

• #54348 (open) — same symptom, macOS, identifies model-picker capability metadata as suspected root cause
• #51131 (open) — same symptom on 2.1.104
• #49902 (open) — same symptom on 2.1.112
• #49757 (open) — empty/unexpandable stub
• #52046 (closed 2026-04-26 at 2.1.117) — supposedly fixed, but symptom persists at 2.1.121

Additional Information

Per #54348, suspected root cause is that the extension's model-capability metadata branch covers claude-opus-4-6[1m] but not claude-opus-4-7[1m], so the renderer strips the expand handler. The webview bundle still ships the <details> toggle component (thinkingToggle, areThinkingBlocksExpanded) — only the data wiring is missing.