CC 2.1.128 Release: New Built-in Background Agent, C# Beta Support, and Model Deprecations
Claude Code (CC) 2.1.128 ships with +1406 tokens, focusing on agent prompt restructures, API reference updates, and model deprecations.
New Agent Instructions: Background Jobs & Onboarding
The old background-job behavior system prompt is replaced with built-in background-agent instructions. Key behaviors:
- Progress narration during background execution
- Tool-result restatement after each step
- Delegation of noisy investigation subtasks
- Explicit status signals:
result:,needs input:, orfailed:
New onboarding-guide closing instructions upload the finalized ONBOARDING.md via ShareOnboardingGuide, handle existing-guide and unavailable-tool cases, and return the team share link.
New Tool Description: RemoteTrigger
The RemoteTrigger tool provides a claude.ai remote-trigger API for listing, reading, creating, updating, and running scheduled remote agent routines — without exposing OAuth tokens.
C# Beta Support
The Claude API reference now documents beta C# tool-runner and Managed Agents support via BetaToolRunner and client.Beta.Agents/Sessions/Environments.
Go & Java SDK Updates
- Go: Adds typed model constants, updates adaptive thinking syntax, and documents the beta advisor tool parameter.
- Java: SDK version updated from 2.17.0 to 2.27.0; added beta advisor tool guidance.
Model Catalog Changes
Claude Sonnet 4 and Claude Opus 4 are deprecated. Recommended replacements:
- Opus 4 → Opus 4.7 or Sonnet 4.6
- Older Sonnet models → Sonnet 4.6
The skill guide Building LLM-powered applications with Claude refreshes the current-model table to Opus 4.7, Opus 4.6, Sonnet 4.6, and Haiku 4.5.
Other Notable Changes
- Removed: Session memory update instructions and the structured
summary.mdsession memory template. - Agent thread notes: Instructs agent threads to return reports/summaries/findings directly in the final message instead of writing
.mdfiles. - Edit tool: Hardcodes the Read-output line-number prefix format as "line number + tab" in indentation-preservation guidance.
- ReadFile tool: Always appends the additional read note placeholder at the end of empty-file warnings.
- Claude API SDK references: Added structured refusal stop-details guidance across Python, TypeScript, C#, Go, Java, PHP, Ruby; added programmatic API error type guidance for Java, PHP, Ruby.
- Model migration guide: Adds Opus 4.7 as the recommended target and adds a tuning check to parse tool inputs as JSON instead of matching serialized raw strings.
📖 Read the full source: r/ClaudeAI
👀 See Also
OpenClaw Agent System Broken After Recent Updates
Recent OpenClaw updates have broken core agent functionality, with users reporting that agents can't be reliably created or run. The system previously allowed creating agents, having them appear correctly, running workflows, and using them for real tasks.
ClawbBot Community Discusses Potential Interface Improvements
The ClawbBot community is actively exploring ideas for enhancing its interface, focusing on boosting user experience and functionality. The discussion ignites promising innovations in the realm of AI coding agents.
FFmpeg Developer Accuses OxideAV of AI License Laundering in MagicYUV Issue
An FFmpeg developer has opened an issue on OxideAV's magicyuv repo, challenging the project's licensing and alleging AI-assisted license laundering of GPL code.
The Hidden Cost of AI-Generated Code: Debugging Spaghetti
A Reddit post captures the reality of shipping AI-generated code fast — then spending weeks debugging bloated functions, null state bugs, and cryptic variable names.