Source Intelligence
Follow Discord

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

← All releases Home ←olderv2.1.172 v2.1.174newer→

Claude Code v2.1.173

3 entries read diff v2.1.172 → v2.1.173 Markdown

This release improves the clarity of safety-refusal messages by making them context-aware: requests blocked for cybersecurity or biology topics continue to name those topics, while all other blocks now show a calmer, less alarming message. It also adds detection support for a new "Fable" model and explicitly disables sandboxing on Windows.

Find
Pick an entry · j / k steps through
2 entries

Improvementsopen

Context-aware safety refusal messages#

What

When a model declines a request due to safety measures, the error message is now tailored to the actual reason rather than defaulting to a generic cyber/bio warning for every refusal.

Details
  • Refusals specifically triggered by cybersecurity or biology content still display the existing message naming those topic areas.
  • All other refusals now show: "This model has measures that flagged something in this session. This sometimes happens with safe, normal conversations." followed by a note that these measures help bring Mythos-level capability in other areas.
  • The model-switching notification (shown when Claude auto-falls back to a different model) also uses this same category check, so users who triggered a fallback for non-cyber/bio reasons no longer see an unexplained reference to cybersecurity or biology topics.
  • Refusal telemetry now records non-cyber/non-bio categories as "other" rather than passing through raw category strings, which normalizes internal analytics.
Evidence

New generic refusal string (search for "This model has measures that flagged something in this session"); category classifier introduced (search for H === "cyber" || H === "bio"); updated fallback-switch messages reference the same classifier

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

Fable model support#

What

Added detection for a model whose name contains "fable" (case-insensitive), with adjusted response-suffix handling when that model is active.

Details
  • A new helper function identifies when the active model is "fable" by checking H.toLowerCase().includes("fable").
  • When a fable model is in use, the [1m] model-suffix token is stripped from responses rather than appended, matching how the model reports itself to the API.
  • This is internal plumbing that enables correct behavior for a new model; no user-facing command or flag change is required.
Evidence

New fable detector (search for "fable"); response-suffix logic updated (the g7 model-name formatter gains a new early-return branch for fable+[1m])

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

1 entry

Bug Fixesopen

#

  • Sandboxing is now correctly reported as unsupported on Windows. The platform support check for the sandbox subsystem returns false immediately when running on Windows, preventing any attempt to initialise or check sandboxing on a platform where it does not work. (search for if (s$() === "windows") return !1 inside the sandbox platform check)
Verbatim
Official · Anthropic

Anthropic’s official release notes

Published verbatim by Anthropic for v2.1.173. Text is unmodified from the upstream changelog. Everything else on this page came out of the bundle instead, which is why the two lists don't match.

  • Fixed Fable 5 model names with a [1m] suffix not being normalized — Fable 5 includes 1M context by default, so the suffix is now stripped automatically
  • Fixed a spurious "sandbox dependencies missing" startup warning on Windows when sandbox was enabled in settings
Read it on GitHub →
System prompt

No change to the system prompt since v2.1.172.

Claude Code, interactive mode

Read the prompts for this release →