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Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial

Session registration now reports a hostSessionId read from the CLAUDE_CODE_HOST_SESSION_ID environment variable

TierUnder the hoodhow much it should matter to you
Useful2my rating, 1 to 5
Signal2worth watching, 1 to 5
AreaSession Managementwhat it touches
KindInternal Changesin v2.1.274,
Under the hood No documentation found

Session registration now reports a hostSessionId read from the CLAUDE_CODE_HOST_SESSION_ID environment variable

What

Claude Code now reads a CLAUDE_CODE_HOST_SESSION_ID environment variable, subject to two other conditions, and includes its value as hostSessionId in the payload sent when registering a session. One other place that reads this value is itself controlled by a separate flag.

Why

This lets Claude Code identify and report the host session a given session belongs to, which is useful in setups where sessions run under a managing host process.

Read from
Names in the bundleCLAUDE_CODE_HOST_SESSION_ID
Feature flag
tengu_tidy_fern Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.274: on

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.

Read once, for one account on one subscription tier, against v2.1.274. It isn't a statement about your account. What a flag value here can and cannot tell you

How sure we are
One source agreesOne thing we can check says the same as this entry.
The name it cites is new in this buildNew in this build: CLAUDE_CODE_HOST_SESSION_ID

See this entry in the whole of v2.1.274 →

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