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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.

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Claude Code v2.1.104

2 entries read diff v2.1.101 → v2.1.104 Markdown

This is a focused reliability release that adds byte-level stream idle timeout detection to catch stalled API connections more quickly. It also includes a minor refinement to the internal system prompt heading for clarity.

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2 entries

Improvementsopen

Byte-level stream idle timeout detection#

What

API streaming responses are now monitored at the byte level for idle connections, catching stalled streams that the existing chunk-level timeout might miss.

Details
  • A new StreamIdleTimeoutError class and TransformStream wrapper monitor the raw byte stream from the API. If no bytes arrive within the timeout window, the stream is aborted and retried.
  • The timeout is controlled by the existing CLAUDE_STREAM_IDLE_TIMEOUT_MS environment variable (default: 90 seconds, minimum: 15 seconds).
  • This is layered on top of the pre-existing chunk-level idle timeout, providing defense-in-depth: the byte-level check catches low-level TCP stalls, while the chunk-level check handles higher-level protocol issues.
  • Error reporting is now more granular — when a stream times out after receiving partial data, the error message distinguishes "Stream idle timeout - partial response received" from "Stream idle timeout - no chunks received", which should improve diagnostics.
  • Only applies to first-party and Anthropic AWS streaming connections (SSE text/event-stream responses).
Usage
# Override the default 90s idle timeout (minimum 15s)
CLAUDE_STREAM_IDLE_TIMEOUT_MS=60000 claude
Evidence

New StreamIdleTimeoutError class (search for "stream idle: no bytes for") and TransformStream wrapper in fetch middleware (search for "Streaming idle timeout (byte-level)")

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

Refined system prompt for text output guidelines#

What

The internal system prompt section heading "Communication style" was renamed to "Text output (does not apply to tool calls)" to clarify that the communication guidelines apply only to text output shown to the user.

Details
  • The body of the prompt is unchanged — the same guidance about brief updates, no narration, and clear communication still applies.
  • The heading clarification may result in slightly improved model behavior when making tool calls, as the model has a clearer signal that the style guidelines do not constrain tool call formatting.
  • This prompt is only active for Opus 4.6 sessions with the quiet_salted_ember flag enabled.
Evidence

Heading change from "# Communication style" to "# Text output (does not apply to tool calls)" (search for "Text output (does not apply to tool calls)")

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.

Verbatim
No official entry

Not individually listed upstream

v2.1.104 does not have its own entry in Anthropic’s official changelog, because prerelease builds are often folded into a neighbouring release. Browse the full changelog for the closest official notes. Everything else on this page came out of the bundle instead, which is why the two lists don't match.

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System prompt

The system prompt was not captured for this release, so this page cannot say whether it moved.

Which releases were captured →