cc-thinkfix

Transparent proxy that fixes Anthropic thinking blocks so Claude Code + LiteLLM just work.

The Problem

When Claude Code has a multi-turn conversation using thinking mode, it sends back thinking and redacted_thinking blocks in the message history. Most OpenAI-compatible endpoints (including LiteLLM's Anthropic adapter) choke on these blocks or silently drop them, breaking reasoning model round-trips.

The Solution

cc-thinkfix sits between Claude Code and your upstream Anthropic endpoint and:

1. Strips redacted_thinking blocks — they're opaque and can't be used anyway
2. Converts thinking blocks to <thinking>...</thinking> text — preserves reasoning context as plain text that any model can read
3. Passes everything else through unchanged — no protocol translation, no SSE re-parsing

Responses flow back untouched. Claude Code natively handles Anthropic-format responses including thinking blocks, so no reverse transformation is needed.

Install

npm install -g cc-thinkfix

Requires Node 20+.

Usage

With Claude Code CLI (recommended)

# Just prefix your normal claude command:
cc-thinkfix claude

# Pass any claude arguments:
cc-thinkfix claude --model deepseek-v4-pro
cc-thinkfix claude -p "explain quantum computing"

No config changes needed. cc-thinkfix auto-detects your upstream from ~/.claude/settings.json or ANTHROPIC_BASE_URL environment variable.

Standalone proxy mode

cc-thinkfix serve --port 3456

Then point any Anthropic client at http://127.0.0.1:3456.

How it detects the upstream

1. Reads ~/.claude/settings.json → env.ANTHROPIC_BASE_URL + env.ANTHROPIC_API_KEY
2. Falls back to ANTHROPIC_BASE_URL + ANTHROPIC_API_KEY environment variables
3. Exits with an error if neither is found

What happens to thinking blocks

| Anthropic Block | Transformation | Why | |---|---|---| | thinking | → text block: <thinking>original content</thinking> | Preserves reasoning context as readable text | | redacted_thinking | Removed entirely | It's encrypted/opaque — can't be forwarded | | thinking request param | Passed through unchanged | Enables thinking mode for current turn |

Dev

npm install
npm run build       # tsc → dist/
npm run dev         # tsc --watch

License

MIT