Cloud/subscription sessions (mobile + web) still don't display thinking - re-file of #52376, wrongly closed as duplicate

Summary

Claude Code cloud sessions (claude.ai/code, accessed via the mobile app or a browser) never display extended-thinking / reasoning content, regardless of the showThinkingSummaries setting. This is a server-side behavior, distinct from the local-session bugs tracked elsewhere, and the original report of this specific issue (#52376) was auto-closed as a duplicate of issues that don't actually cover it, then auto-locked before that could be corrected.

Background

• #52376 (closed as duplicate, then locked) originally reported that Claude Code sends a redact-thinking-2026-02-12 anthropic-beta header by default, and that even when showThinkingSummaries is enabled, subscription-authenticated sessions get back a thinking block with an empty thinking field (just a signature, used for token accounting). The same request structure returns real summarized text for API-key-authenticated sessions.
• The auto-dedup bot closed #52376 as a duplicate of #49268 and #48065. Both of those are about local/API-key sessions where showThinkingSummaries / thinking.display isn't honored due to a client-side harness bug. This issue is about the server intentionally redacting thinking for subscription auth — a different mechanism, and as far as I can tell still unresolved for cloud sessions specifically.
• Because #52376 was auto-locked 7 days after closing, it can no longer be reopened or commented on. Filing a new issue and referencing the old one is what the lock bot itself recommends.

Current behavior

• Open a cloud session at claude.ai/code, via the mobile app or a browser.
• No thinking/reasoning content is ever shown, and there is no setting anywhere in the mobile app or web client to enable it.
• This holds even though local sessions (terminal, API-key auth) can show thinking via showThinkingSummaries: true + Ctrl+O.

Requested behavior

Honor thinking.display: "summarized" for subscription/cloud sessions the same way it's honored for API-key sessions, and surface a UI toggle for it in the mobile app and web client — mirroring the existing showThinkingSummaries setting used locally.

Use case

Understanding why the model made a decision matters for debugging AI-generated code, post-session review/audit, and learning how the model approaches a problem — that need doesn't disappear just because someone is on a subscription plan, or on their phone instead of a terminal.

References

• Originally reported in #52376 (auto-closed as duplicate 2026-04-27, auto-locked 2026-05-07 — no longer reopenable)
• Distinct from #49268 and #48065, which track local/API-key session bugs where the setting exists client-side but isn't honored