Claude Code v2.1.283 Introduces Strict Model Controls, Prompt Auditing, and Gateway Optimization

What changed#

Model Management and Access Control

• Introduced availableModelsMatch managed setting with an "exact" option. When set, availableModels entries restrict usage to the precise model version named, blocking automatic upgrades to new releases until they are explicitly listed.
• Added deniedModels managed setting to block specific models, taking precedence over availableModels rules.

Gateway and Routing Enhancements

• Added x-claude-code-prompt-id to gateway hint headers, enabling LLM gateways to group requests originating from a single user prompt. Opt in via environment variable CLAUDE_CODE_GATEWAY_HINT_HEADERS=1.
• Added opt-in load_test_mode block to the Claude apps gateway configuration. This mode builds and signs requests without sending them upstream, returning canned replies to facilitate load testing of deployments.
• Added mantle as an upstream provider in the Claude apps gateway to support Amazon Bedrock’s Mantle endpoint.

Observability and Auditing

• Enabled MCP tool, WebFetch, and WebSearch outputs in the tool.output OpenTelemetry span event when OTEL_LOG_TOOL_CONTENT=1 is set.
• Added /doctor prompt-audit (alias /checkup prompt-audit) to audit CLAUDE.md files, skills, agents, and commands for prompting patterns written for older models.

User Interface and Diagnostics

• Added click-to-expand functionality for truncated messages from other sessions when viewing in fullscreen mode.
• Included path in --plugin-dir load-failure entries within the stream-json system/init plugin_errors output, identifying the directory that failed to load.

Bug Fixes

• SDK Session Stability: Resolved issues where SDK sessions lost deferred tool calls, finished tool results upon early turn termination, and result.usage data on non-streaming fallbacks. Also fixed loss of tool results when a held approval prompt occurred after a worker restart.
• MCP Lifecycle: Fixed MCP progress notifications being discarded when long-running tool calls moved to the background; background tasks now display the latest progress. Corrected behavior where stdio MCP servers remained running after a session ended during startup. Addressed cases where a brief HTTP 404 from a stateless remote MCP server rendered the server unusable for the session duration despite appearing connected.
• MCP Authentication: Fixed opaque SDK errors when signing in to MCP servers with no valid URL; /mcp now suppresses the Authenticate option for such servers.
• Metrics and Usage: Fixed the weekly Fable limit not displaying in /usage or VS Code usage meters when telemetry was disabled.
• Model Picker Accuracy: Fixed /model accepting Sonnet 4.6 or Sonnet 5 identifiers with [1m] or date suffixes when the plain ID was previously refused. Corrected the /model picker to respect ANTHROPIC_DEFAULT_HAIKU_MODEL instead of showing a hardcoded Haiku version and price.
• Workflows and Caching: Fixed dynamic workflows initiated during a model fallback from running every agent on the fallback model; they now retry the configured model. Resolved DISABLE_PROMPT_CACHING_HAIKU having no effect when Haiku was the session’s primary model.
• Plugin CLI Corrections:
  • claude plugin validate now rejects plugin or marketplace names that cannot be installed, including those defined in marketplace.json. It also validates that outputStyles, themes, monitors, and lspServers paths exist and remain within the plugin directory.
  • claude plugin details now correctly reports MCP server counts for plugins declaring servers in plugin.json.
  • claude plugin marketplace remove now lists the installed plugins uninstalled with the marketplace.
  • claude plugin uninstall now correctly handles plugins with IDs differing only by case, preserving options and secrets when the named plugin lacks an enabledPlugins entry at the scope.
  • Plugins declaring no version now restore to the installed version rather than the source’s newest commit when cached files are missing.
  • Resolved “cache-miss” loading failures for user-installed plugins and marketplaces after moving home or config directories, such as in bind-mounted devcontainers.
  • Fixed installed_plugins.json recovering from records under invalid plugin IDs instead of failing to load.

Why it matters#

The introduction of availableModelsMatch: "exact" and deniedModels provides granular control over model access, preventing unintended upgrades to new model versions in production environments. This is critical for teams managing cost and compliance across changing model capabilities.

The prompt-audit command directly addresses technical debt in agent configurations by identifying prompts optimized for older models, helping developers maintain compatibility and performance as underlying models evolve. Similarly, the expansion of OpenTelemetry observability with tool content logs under OTEL_LOG_TOOL_CONTENT=1 enables deeper debugging of MCP and web fetching operations.

Stability improvements in SDK session recovery and MCP lifecycle management reduce friction in automated workflows. Fixing deferred tool call retention, background task progress reporting, and stdio server cleanup ensures that long-running or interrupted tasks behave predictably. The load_test_mode feature allows safe validation of gateway configurations without impacting upstream API quotas.

Plugin CLI fixes resolve edge cases that could lead to silent misconfigurations, invalid state persistence, or unexpected restoration behaviors, particularly in containerized development environments where directory paths may shift.

What to do next#

• Upgrade to Claude Code v2.1.283 to access model management controls and stability fixes.
• Set CLAUDE_CODE_GATEWAY_HINT_HEADERS=1 to enable request grouping in LLM gateways.
• Configure availableModelsMatch with "exact" and define deniedModels in managed settings to enforce strict model selection policies.
• Run /doctor prompt-audit to review CLAUDE.md, skills, agents, and commands for legacy prompting patterns.
• For provider-agnostic prompt structure and evaluation, see Prompt Engineering Basics.
• Enable OTEL_LOG_TOOL_CONTENT=1 to capture MCP, WebFetch, and WebSearch outputs in OpenTelemetry spans.
• Validate plugin configurations using claude plugin validate to ensure paths and marketplace definitions are correct.
• If using devcontainers or custom directory mounts, verify that user-installed plugins and marketloads load correctly without cache-miss errors.
• Review gateway configuration to determine if load_test_mode supports your deployment testing needs.

Settings that expose tool content to telemetry or change model access can affect privacy, governance, and cost. Validate the relevant retention policy, approval boundary, and managed configuration in a non-production environment before enabling them broadly.

Sources#

• Official Claude Code v2.1.283 release notes