Claude Code 2.1.273-2.1.278: what changed
Catch-up fiche for Claude Code 2.1.273-2.1.278: AGENTS.md, claude.ai skill sync, auto-mode classifier default, and the 2.1.276 gateway hotfix. Thin release notes only.
Since the 2.1.271-2.1.272 fiche (Sep 15), Claude Code shipped 2.1.273 through 2.1.278. Operator standouts only: 2.1.278 defaults auto mode to a server-side classifier (no classifier-overhead charge where the server runs checks; opt-out CLAUDE_CODE_AUTO_MODE_SERVER=0; /status row); 2.1.277 reads AGENTS.md when there is no CLAUDE.md; 2.1.275 syncs claude.ai skills/plugins into the terminal and adds send-now; 2.1.276 hotfixes the gateway advisor_20260301 400. Thin radar catch-up - not a rehash of 271/272.
2.1.278 - server-side auto classifier
For Claude API and Enterprise users, and on Bedrock, Vertex, Foundry, and gateways, auto mode now defaults to the server-side classifier. Where the server performs the checks as part of the session’s model requests, classifier overhead is not charged. Platform or region rollout may still fall back to billed local classifier requests.
Opt out with CLAUDE_CODE_AUTO_MODE_SERVER=0 (shell or env settings) on Bedrock, Vertex, Foundry, and gateways. Docs: the variable is not read on a direct Anthropic API connection. Setting it forces Claude Code’s own (billed) classifier and suppresses the ineligibility notice.
Check with /status: the Auto mode server row reads Enabled while server checks decide actions, Disabled after fallback. When the server’s checks can’t reach the session, Claude Code holds the first checked action and shows the “this session isn’t eligible” notice - Enter continues on billed local classifier; Esc/Ctrl+C cancels the held action. Pro / Max / Team plans never see the notice.
Canonical docs: Auto mode classifier billing. Note: 2.1.273 temporarily defaulted Bedrock/Vertex/Foundry auto mode to the local classifier (CLAUDE_CODE_AUTO_MODE_SERVER=1 to opt in). 2.1.278 is the operator truth now - teach 278 only.
2.1.277 - AGENTS.md
In a project with no CLAUDE.md, Claude Code reads AGENTS.md instead. Toggle under Project instructions in /config. Not yet on Bedrock, Vertex, or Foundry. Deeper sharing how-to: How should I share AGENTS.md / CLAUDE.md? (planned) (planned).
2.1.275 + 2.1.276 - sync, send-now, gateway hotfix
2.1.275 sync: skills and plugins enabled on your signed-in claude.ai account sync into terminal sessions. Opt out with syncClaudeAiSkills: false or syncClaudeAiPlugins: false. How-to: How do I sync claude.ai skills/plugins into Claude Code? (planned) (planned).
2.1.275 send-now: ctrl+enter (or ctrl+x ctrl+s) interrupts the current turn and sends all queued messages at once. Sent/queued messages show gray until the model receives them.
2.1.276: fixes every request failing with 400 … Input tag 'advisor_20260301' when ANTHROPIC_BASE_URL points at a proxy or gateway (2.1.275 regression). Gateway operators: skip 275; upgrade to ≥ 2.1.276.
2.1.274 / 2.1.273 - one-liners
- 2.1.274: visible warning when memory usage is critical (with free/restart steps);
CLAUDE_CODE_MCP_STARTUP_WAIT_MSbounds how long the first non-interactive turn waits for connecting MCP servers (0= don’t wait). - 2.1.273: optional gateway hint headers via
CLAUDE_CODE_GATEWAY_HINT_HEADERS=1; MCP disconnect mid-session notifies and points at/mcpafter reconnection gives up.
Dense fix lists in 273-277 stay in the CHANGELOG - not expanded here.
Upgrade readout
| Operator | Action |
|---|---|
| Auto-mode / Bedrock-Vertex-Foundry / gateway | Update to ≥ 2.1.278; check /status - Auto mode server; set CLAUDE_CODE_AUTO_MODE_SERVER=0 only if the gateway can’t pass safeguards fields |
| Gateway stuck on 2.1.275 | Jump to ≥ 2.1.276 if seeing advisor_20260301 |
| Multi-agent / no CLAUDE.md repos | Try AGENTS.md (see planned B above) |
| Signed-in terminal | Expect claude.ai skill/plugin sync unless opted out (see planned B) |
For Sep 15 standouts (Remote fast, omitClaudeMd, per-command allowed_domains, --accept-command), use the prior fiche - not repeated here.
Sources (checked 2026-09-19)
- Claude Code CHANGELOG.md - 2.1.273-2.1.278 bullets only
- Auto mode classifier billing - 278 default, opt-out,
/status, fallback notice - CF radar
/workspace/claude-for/radar/2026-09-19.md- N intake; P0 interrupt No - Live prior: /guides/claude-code-2-1-271-272-2026-09-15