Claude Code v2.1.315: subagent effort control, certificate-trust drops#
Published by Alex Sorokoletov
Part of the Claude Code Version Tracker series. | Official Env Vars | Official Changelog
Claude Code v2.1.315, the published build after v2.1.314, adds a variable that sets the effort level subagents run at, a switch that turns the ultrathink keyword off, and stricter certificate trust that drops self-named and looped cross-certificates it cannot verify. Two new variables keep those certificates, and the release carries no changelog entry of its own.
Subagent effort, and an off switch for ultrathink#
CLAUDE_CODE_SUBAGENT_EFFORT sets the effort level subagents run at when nothing else names one, rather than inheriting the session's.[1] It is read when a subagent's own definition leaves effort unset, and it takes a level (low, medium, high, xhigh) or inherit.
CLAUDE_CODE_DISABLE_ULTRATHINK turns the ultrathink keyword off.[1] With it set, the word has no effect when it appears in a prompt.
Stricter certificate trust#
Two new variables control how Claude Code treats certificates it cannot verify, both as escape hatches for behavior that is on by default.
Claude Code drops a certificate that names itself as its own issuer when it cannot confirm the certificate's key signed it and no CA in the list chains to a root that did. CLAUDE_CODE_DISABLE_SELF_NAMED_CERT_DROP=1 keeps every such certificate.
It also drops system-store certificates that certify each other in a loop beside their root. CLAUDE_CODE_DISABLE_LOOPED_CROSS_CERT_DROP keeps those looped cross-certificates, for a private CA that needs one.[1]
Both drops are new in this build. A private-CA or self-signed setup that connected on v2.1.314 can need one of these variables after upgrading.
A policy-blocked host is not dialed again#
CLAUDE_CODE_MCP_NO_REDIAL_AFTER_POLICY_REFUSAL changes how Claude Code reacts when a remote request comes back with a 403 that the request was blocked by policy, with no rule or allowlist entry allowing the host. With the variable set, that host and port are recorded and not dialed again in the session.
New environment variables#
| Variable | What It Does |
|---|---|
CLAUDE_CODE_SUBAGENT_EFFORT | Sets the effort level subagents run at when their own definition names none. Read when a subagent leaves effort unset, it takes a level (low, medium, high, xhigh) or inherit. |
CLAUDE_CODE_DISABLE_ULTRATHINK | Turns the ultrathink keyword off, so the word has no effect in a prompt. |
CLAUDE_CODE_DISABLE_SELF_NAMED_CERT_DROP | Keeps certificates that name themselves as their own issuer, which Claude Code drops by default when it cannot confirm the certificate's key signed it and no CA in the list chains to a root that did. Set it to 1 to keep them. |
CLAUDE_CODE_DISABLE_LOOPED_CROSS_CERT_DROP | Keeps system-store certificates that certify each other in a loop beside their root, which Claude Code otherwise drops. Meant for a private CA that needs the loop. |
CLAUDE_CODE_MCP_NO_REDIAL_AFTER_POLICY_REFUSAL | After a remote request is answered with a 403 that the request was blocked by policy, records the host and port and does not dial it again in the session. |
Settings that arrive before the notes describe them#
v2.1.315 publishes no release note of its own. The v2.1.316 changelog, out the next day, describes the subagent effort level, the ultrathink switch, and the looped cross-certificate control; the self-named certificate drop and the MCP no-redial control appear in neither entry.[1] The weight falls on the certificate handling, which is on by default: upgrading to v2.1.315 can change which certificates Claude Code accepts before any note warns you, so an mTLS or private-CA connection that held on the previous build is worth a check, with the two DISABLE_* variables as the route back.
This analysis is conducted for educational and research purposes under fair use principles. All trademarks and software referenced belong to their respective owners.
Sources#
- Claude Code Official Changelog, v2.1.316 release notes
Related Versions#
- Claude Code v2.1.312: Write reads large files fully before overwriting, skills found after a deeper cd
- Claude Code v2.1.311: sessions past 200K tokens keep going, self-hosted-runner hold flags
- Claude Code v2.1.310: a Monitor tool for background work, retries that drop a rejected beta
- Claude Code v2.1.309: sandbox and permission-boundary fixes, ultrareview workspace trust
- Claude Code v2.1.307: safety-event telemetry, MCP calls stop double-firing
Previous Claude Code analysis: v2.1.314 (October 31, 2026)
All 84 Claude Code analyses: Claude Code Version Tracker · Official Claude Code changelog