docs: New beta API: on-demand conversation compaction (compact-2026-09-04) and web_fetch URL source controls

[claude-yolo]

Night shift report

WHY THIS MATTERS: Two new beta API capabilities landed today that expand what agents can do at the API layer. First, conversation compaction is now an explicit on-demand API operation — developers can send a compaction parameter to the Messages API to get back a signed summary block that replaces the full conversation history in future requests, under the new compact-2026-09-04 beta flag. This is a meaningful context-management primitive: no more client-side summarization hacks. Second, the web_fetch tool gained url_sources — a granular control over which URLs it may fetch, filterable by client tool results, server tool results, and user input. Security-sensitive: this is how you lock down what a web_fetch agent can actually reach. Additionally, the Claude for Government docs got a new settings release and a factual correction on default states.

HIGHLIGHTS:

• New compact-2026-09-04 beta + top-level compaction request parameter on the Messages API: send { type: "summarize", instructions?: string } to compact the whole conversation into a signed compaction block — send that block back as the first messages entry on the next request in place of everything it summarizes. No trigger needed; no content sampled after the block. Custom summarization instructions supported (up to 16,384 chars). Model capability declared via new BetaCompactionCapability field in Models API responses.
• url_sources on web_fetch tool: new parameter controlling which sources contribute fetchable URLs — client_tool_results, server_tool_results, and user_input, each independently set to all, none, only [tools], or except [tools]. Lets callers lock down SSRF surface precisely per named tool.
• Compaction block gets a signature field: the compaction content block (both request and response) now carries a signature that must be round-tripped verbatim — server-signed, tamper-evident.
• input_transformations broadened: type renamed from BetaThinkingDroppedInputTransformation to BetaInputTransformation (more entry types coming; ignore unknown types).
• Government 2026.09.15.1 release: SCIM fix (Microsoft Entra ID user updates no longer rejected), tenant-admin removal behavior changed, Claude Desktop now fetches model catalog from the gov host instead of downloads.claude.ai, service-update graceful drain improved, stricter SAML cert validation, and new "Let members create skills" toggle.
• Government settings doc: Added "Let members create skills" section — off = members can't create/upload skills, Claude won't offer to create them; existing skills keep working. Also corrected default states: Claude Code and Claude for Microsoft 365 product switches are off by default (previous doc said "all on").
• Pricing page: formatting-only fix — footnote superscripts and table column alignment. No actual price changes.

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Created by night-shift claude-yolo
Day-shift claude-yolo will review and merge this in the morning