Claude Code System Prompts v2.1.139: Claude Platform on AWS Docs, Summarization Security, PowerShell Tooling

Claude Code system prompts v2.1.139 (+2,248 tokens) is out, bringing a cluster of updates around the new Claude Platform on AWS offering, security hardening in summarization prompts, and a substantial PowerShell tool reference.

Claude Platform on AWS — New Reference Documentation

Reference docs for using the Claude Developer Platform through AWS infrastructure are now included. This covers AnthropicAWS clients, required region and workspace configuration, SigV4 authentication, and short-term API keys. The Building LLM-powered applications with Claude skill now treats Claude Platform on AWS as Anthropic-operated with same-day API parity and full Managed Agents support, while Bedrock, Vertex, and Foundry remain Claude API + tool use only. The Model migration guide adds a section noting that Claude Platform on AWS uses bare first-party model IDs, with the full rename table and breaking-change sections applying verbatim (distinct from Bedrock). Live documentation sources now include WebFetch URLs for the platform and its required IAM actions.

Security-Instructions Preservation in Summarization

Multiple prompts now enforce preservation of security-relevant instructions across compactions:

• Conversation summarization — The agent prompt now requires noting security-relevant instructions or constraints (sensitive files, forbidden operations, credential handling rules) and preserving them verbatim in the summary.
• Recent Message Summarization — Same preservation requirement added.
• Partial compaction instructions — Now also carries security instructions across partial compactions.

PowerShell Tool Reference Table

The PowerShell tool description now includes a substantial reference table mapping Unix commands to PowerShell equivalents. Key entries:

• head → Get-Content -Head
• tail → Get-Content -Tail
• which → Get-Command
• touch → New-Item -ItemType File
• wc → Measure-Object -Line -Word -Character
• mkdir -p → New-Item -ItemType Directory -Force
• rm -rf → Remove-Item -Recurse -Force
• ln -s → New-Item -ItemType SymbolicLink -Target
• chmod → Set-ItemProperty -Path -Name Attributes -Value Normal
• 2>/dev/null → 2>&$null / -ErrorAction Ignore
• inline VAR=x → $env:VAR = 'x'
• bash control flow → PowerShell equivalents

It also clarifies that -ErrorAction SilentlyContinue still causes exit code 1 unless promoted to terminating and caught.

Other Prompt/Skill Changes

• Auto mode system prompt: Drops the "Auto Mode Active" header and reframes destructive-action guidance generically.
• Harness instructions: Removes note that automatic context compaction triggers on long conversations.
• Memory instructions: Replaces 3-4 word titles with short kebab-case slugs, nests type under a metadata block, and introduces [[their-name]] cross-links between related memories.
• Output style system reminder: Lets an output style supply its own per-turn reminder text, falling back to default.
• Task tools & TodoWrite reminders: Removed instructions telling Claude to never mention the reminder to the user.
• Dynamic pacing & self-pacing loop execution: Reordered so the brief confirmation (task ran, monitor as wake signal, fallback delay choice) is written as text before the schedule-wakeup call ends the turn.
• /insights report output: Removes trailing additional-message block from the shareable report.