[BUG] `/context` command fails after resuming session due to thinking block requirement

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When using the /context command after resuming a CC session, the command fails with an HTTP 400 error about missing thinking blocks.

The issue appears to be that thinking blocks are not being preserved when the session is exited and resumed.

What Should Happen?

The /context command should work normally after resuming a session, just as it does in a fresh session.

Error Messages/Logs

This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason:
Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.3.content.0.type: Expected `thinking` or `redacted_thinking`, but found `text`. When `thinking` is enabled, a final `assistant` message must start with a thinking block. We recommend you include thinking blocks from previous turns. To avoid this requirement, disable `thinking`. Please consult our documentation at https://docs.claude.com/en/docs/build-with-claude/extended-thinking"},"request_id":"req_011CWE2kYf1cFV8iUGL4kA7Q"}
    at W9.generate (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:460:11051)
    at jT.makeStatusError (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:807:2195)
    at jT.makeRequest (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:807:5420)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
· Incubating…FPB (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:957:4682)
    at async myA (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:2106:95)
    at async fZ5 (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:2106:2329)
    at async Promise.all (index 6)
    at async NH0 (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:2106:2970)
    at async Object.call (file:///usr/lib/node_modules/@anthropic-ai/claude-code/cli.js:3639:454)

Steps to Reproduce

1. Start a new CC session
2. Send a first message and wait for the response
3. Run /context command works
4. Exit the session
5. Resume the session
6. Run /context command fails

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.72

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_