# Claude Code v2.1.68 > Claude Code v2.1.68, released 4 Mar 2026 (2026-03-04). 5 entries read out of the shipped bundle. Unofficial, and not affiliated with Anthropic. Web version: https://changelogs.core-directive.com/v/2.1.68 This release re-enables the "ultrathink" keyword as a way to boost reasoning effort to high for the current turn, complete with a new rainbow shimmer visual effect. It also adds a `CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP` environment variable to let users opt out of automatic model remapping to Opus 4.6, and introduces a redesigned server-controlled effort selection dialog. ## Changes ### Ultrathink keyword re-enabled as effort boost **What** Typing "ultrathink" in a message now sets reasoning effort to "high" for that turn. In the previous version, ultrathink was deprecated and showed a dismissive message — it now has real functionality again. **Usage** `ultrathink about the architecture of this codebase and suggest improvements` **Details** - When "ultrathink" appears anywhere in your message, effort is automatically set to high for that turn - A notification briefly displays: "Effort set to high for this turn" - The word "ultrathink" is rendered with a rainbow color shimmer effect in the terminal (cycling through red, orange, yellow, green, blue, indigo, and violet) - Controlled by the `tengu_turtle_carbon` feature flag (defaults to enabled) - Replaces the old "Ultrathink no longer does anything. Thinking budget is now max by default." deprecation message **Evidence** Ultrathink effort injection (search for `"ultrathink_effort"`) — `rqY()` at line ~290076 checks `jd()` (`"tengu_turtle_carbon"`) and `Vf7()` (`/\bultrathink\b/i`) - Flag `tengu_turtle_carbon`: On for this account, and not off by default (read for one account on one subscription tier against v2.1.68; this account: on, anonymous baseline: on, compiled default: no gate table built for this version) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release. ### Legacy model remap opt-out **What** Users who were automatically migrated from legacy Opus models to Opus 4.6 can now opt out by setting an environment variable. **Usage** `export CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP=1` **Details** - When your model is auto-remapped to Opus 4.6, the notification now reads: "Model updated to Opus 4.6 · Set CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP=1 to opt out" - The notification displays for 8 seconds (up from 3) when the opt-out message is shown, giving you time to read the instructions - Setting the environment variable to `1` disables the automatic model remapping entirely - The remap behavior is also gated by the `tengu_grey_wool` feature flag (defaults to enabled) **Evidence** Model remap opt-out (search for `"CLAUDE_CODE_DISABLE_LEGACY_MODEL_REMAP"`) — `gy1()` at line ~535228 ### Effort selection dialog redesigned The effort callout dialog for Opus 4.6 users has been redesigned with server-configurable content and a simplified option set. **Details** - Dialog title and description are now fetched from the server (via `tengu_grey_step2` feature flag) instead of being hardcoded - Options are simplified to three clear choices: - "Use medium effort (recommended)" - "Use high effort" - "Use low effort" (new — previously only medium and high were offered) - Removed verbose per-option descriptions and the "(current)" suffix labeling - Uses a separate dismiss state (`effortCalloutV2Dismissed`) so users who dismissed the old dialog may see the new one **Evidence** Server-controlled effort dialog (search for `"tengu_grey_step2"`) — `zb6()` at line ~162660, dialog at `ohq()` line ~588325 - Flag `tengu_grey_step2`: Not enough to say (read for one account on one subscription tier against v2.1.68; this account: no value returned, anonymous baseline: no value returned, compiled default: no gate table built for this version) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release. ### Removed silent medium-effort auto-migration The automatic migration that silently set Opus 4.6 effort to "medium" has been removed. **Details** - Previously, on startup, the app would set `opus46EffortMediumMigrationTimestamp` and briefly flash "Opus 4.6 effort updated to medium" - This silent migration has been completely removed — effort is no longer changed behind the scenes - Default effort for Opus 4.6 is now determined by feature flags (`tengu_quartz_falcon`, `tengu_grey_step2`) rather than a one-time migration **Evidence** Removed migration function (search for `"opus46EffortMediumMigrationTimestamp"` — present in v2.1.67, absent in v2.1.68) - Flag `tengu_grey_step2`: Not enough to say (read for one account on one subscription tier against v2.1.68; this account: no value returned, anonymous baseline: no value returned, compiled default: no gate table built for this version) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release. ### Server-controlled effort dialog [Gradual Rollout] **What** The redesigned effort dialog described above is gated behind the `tengu_grey_step2` feature flag, which defaults to `{ enabled: false }`. **Status** Feature-flagged (disabled by default, server-controlled rollout) **Details** - The `tengu_grey_step2` flag controls whether the dialog appears and provides its title and description text - A separate `tengu_quartz_falcon` flag also influences the default effort level for Opus 4.6 - First-party users who previously dismissed the old effort dialog won't see the new one until `tengu_grey_step2` is enabled server-side - API users (`By()` or `wb6()`) can also be enrolled via the same flag **Evidence** Dialog visibility (search for `"effortCalloutV2Dismissed"`) — `zIq()` at line ~588370 checks `zb6().enabled` - Flag `tengu_grey_step2`: Not enough to say (read for one account on one subscription tier against v2.1.68; this account: no value returned, anonymous baseline: no value returned, compiled default: no gate table built for this version) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.