# Claude Code v2.1.201

> Claude Code v2.1.201, released 3 Jul 2026 (2026-07-03). 2 entries read out of the shipped bundle. Unofficial, and not affiliated with Anthropic.

Web version: https://changelogs.core-directive.com/v/2.1.201

Version 2.1.201 is a same-day hotfix release built approximately 16 hours after 2.1.200 (build timestamp advances from 03:43 UTC to 19:53 UTC on 2026-07-03). The only substantive code change is an addition to an internal model-compatibility list that includes `claude-sonnet-5`. There are no new commands, flags, settings, or user-facing messages in this release.

## Improvements

### claude-sonnet-5 added to model compatibility list

The identifier `"claude-sonnet-5"` was appended to the hardcoded model-name list inside function `ALn` (within the `tw` lazy-init block, line ~162348–162370). `ALn` is the sole gatekeeper for whether the `mid-conversation-system-2026-04-07` API beta header (`BX`) is included in outgoing requests. When `ALn` returns `true` the header is pushed onto the beta-header array and sent to the API; when it returns `false` the header is omitted. The function evaluates candidates in strict priority order: (1) HIPAA mode (`hipaa` runtime flag) → unconditionally `false`; (2) the `CLAUDE_CODE_FORCE_MID_CONVERSATION_SYSTEM` environment variable → forces `true` when set; (3) a per-model capability override read from `ANTHROPIC_CUSTOM_MODEL_OPTION*` environment variables → returns that value if present; (4) the hardcoded model-name list — now including `claude-sonnet-5` alongside `claude-3-*`, `claude-opus-4-0` through `claude-opus-4-7`, `claude-sonnet-4-0`, `claude-sonnet-4-5`, `claude-sonnet-4-6`, and `claude-haiku-4-5` — → returns `false`; (5) model registry capability check (`OF(n, "mid_conv_system")`) or the special case `claude-mythos-5` → returns `true`; (6) provider-based fallback. Because `claude-sonnet-5` carries `mid_conv_system` in its capabilities array in the model registry (line ~113995), path (5) would have returned `true` and activated the beta header absent the explicit suppression; adding `claude-sonnet-5` to the hardcoded list at step (4) overrides that.

Users who configure Claude Code with `claude-sonnet-5` will no longer have the `mid-conversation-system-2026-04-07` beta header sent with their API requests. In concrete terms, mid-conversation system-prompt updates — such as reminder injections from hooks or context-management refreshes — are delivered as `<system-reminder>` text embedded inside user messages rather than as native `role: "system"` API turns. This also eliminates a failure path that would otherwise fire: when the server rejects the beta header with an HTTP 400 containing the header name alongside `"anthropic-beta"`, the phrase `"Unexpected role"` in an input message, or a `"not supported … role … system"` pattern, the code (`zWn`, line ~354273) detects the rejection, strips `BX` from the active header list, sticky-rejects it for the remainder of the session (until the user runs `/clear` or `/compact`), logs a `[mid-conv-system] server rejected role:"system"` warning, fires the `tengu_mid_conv_system_fallback_retry` telemetry event, and retries with the `<system-reminder>` format. By suppressing the header up-front, Claude Code avoids that entire error-detect-strip-retry cycle for `claude-sonnet-5` users.

**Evidence**

`ALn` function in the `tw` lazy-init block (lines ~162348–162370); `BX` beta-header constant definition (line ~122337, `"mid-conversation-system-2026-04-07"`); mid-conv-system rejection handler (lines ~593496–593508); rejection detector `zWn` (lines ~354273–354280); `claude-sonnet-5` model capability definition showing `mid_conv_system` (lines ~113969–113999)

## Notes

All other modifications in this release are mechanical version-string propagation: every embedded copy of the package version (`VERSION: "2.1.200"` → `"2.1.201"`), build timestamp, and Git SHA was updated across the roughly 35 structural and 72 string-only locations where these constants appear inline. No user-facing behavior, commands, or settings changed as a result of those updates.