Fix OpenClaw for Claude Fable 5 API Change to Avoid Workflow Interruption
Step-by-step guide to patch your OpenClaw setup after Anthropic's Fable 5 update broke legacy configurations, preventing failed API calls.
Practical Summary
When Anthropic updated Claude Fable 5 to require new adaptive-thinking parameters, the OpenClaw tool stopped working. This fix involves running a script or manually patching OpenClaw's distribution files to recognize Fable 5 as an adaptive model, ensuring your AI-assisted coding workflow continues without interruption or forced upgrades.
Why It Matters
API changes can silently break integrated tools, halting developer workflows and incurring hidden costs in debugging time. Knowing how to apply a community fix quickly minimizes downtime and lets you continue using cost-effective models without being forced onto more expensive plans or alternatives.
Understanding the Problem
Anthropic changed the Claude Fable 5 model to require 'adaptive-thinking' parameters (thinking.type: "adaptive" + output_config.effort). OpenClaw, a tool using Claude via API, had its model list hardcoded and didn't recognize Fable 5, causing every Fable 5 request to error out.
Apply the Fable 5 Adaptive-Thinking Hotfix
Navigate to your OpenClaw workspace and run the provided patch script. This script is designed to be safe (idempotent) and will only apply changes if needed.
Command: cd /data/.openclaw/workspace && node scripts/patch-fable5-adaptive-thinking.mjs
If the Script is Missing: Manual Patch Guide
If the script doesn't exist, you need to manually edit two files in OpenClaw's distribution folder. First, locate the files by searching for 'supportsAdaptiveThinking'.
Edit #1: In the file that lists adaptive models (e.g., matching the line for 'sonnet-4-6'), add: || modelId.includes("fable-5") || modelId.includes("fable5")
Edit #2: In the code that handles turning thinking off, change the guard condition to only send the thinking-off parameter if the model does NOT support adaptive thinking. For adaptive models like Fable 5, omit the thinking parameter entirely to avoid conflicts.
Handling a 'MISS' Error and Final Step
If the script reports 'MISS' (anchor not found), OpenClaw may have been updated. Re-check the new distribution files to see if Fable 5 is now natively supported, or re-derive the patch points from the new code structure.