Evidence record / claude-code
A dated record of one change, kept so the writing that cites it can be checked. Compiled from the sources listed below by the research run, not written for reading. The judgment lives in the issues that cite it, below.
2026-08-17-claude-code-subagent-forking-is-on-by-default-a-forked-subagent-inherits-the-full
Subagent forking is on by default: a forked subagent inherits the full conversation and prompt cache.
"Subagent forking is now on by default: a subagent_type: "fork" subagent inherits the full conversation and prompt cache, and non-teammate agent spawns in interactive sessions now run in the background by default." Two related economics changes landed alongside it. v2.1.229: "Improved workflow fan-outs to stagger same-prefix sibling agents so subsequent agents read the cached prompt prefix instead of re-paying it (CLAUDE_CODE_WORKFLOW_PREFIX_STAGGER_MS=0 disables)" -- a fan-out of N agents previously paid the prefix N times because they raced before any of them had written the cache. v2.1.224 removed the 200-subagent-per-session spawn cap entirely: "long-running sessions no longer refuse new agents (concurrency and depth limits still apply)." v2.1.221 also cut auto-mode cost by "reusing the cached conversation prefix across decisions" for permission checks.
Channel: tagged-release. Ancestry: Closed source; npm publish record is the release proof. registry time[] gives 2.1.232 = 2026-08-13T21:30:53Z, plain non-prerelease semver, per-version manifest resolves HTTP 200, published under dist-tag latest. Not in stable (2.1.226). No prerelease tag exists for this -- it went straight to the default-on state in a stable release.
Operator consequence: Test this if you orchestrate subagents, because the default changed underneath you in two ways at once. A forked subagent now sees the entire parent conversation -- that is the point, and it is also a context-scoping change: work you had isolated in a subagent by virtue of it starting clean is no longer isolated unless you spawn a non-fork type. Separately, agent spawns now background by default in interactive sessions, so a workflow that assumed a blocking spawn will return control earlier than it used to. The cache-prefix staggering is a straightforward win to leave on; measure your fan-out cost before and after if you run large ones, since re-paying the prefix N times was the previous behaviour.
Receipt
Finding metadata
Run: 2026-08-17-weekly-digest-2026-08-10_2026-08-17-frontier-v0
Finding ID: 2026-08-17-claude-code-subagent-forking-is-on-by-default-a-forked-subagent-inherits-the-full
Source links
Primary links, including exact changelog lines when available.
Versioned source: run artifact