{"version":"2.1.269","anchor":"tether-thread-continuation-requests-can-omit-system-prompt","canonical_anchor":"tether-thread-continuation-requests-can-omit-system-prompt","heading":"'Tether' thread-continuation requests can omit system prompt\/tools when continuing, behind two off-by-default flags, with a fingerprint-mismatch circuit breaker","tier":"soon","area":"Internals","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.269\/e\/tether-thread-continuation-requests-can-omit-system-prompt","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.269","markdown":"### 'Tether' thread-continuation requests can omit system prompt\/tools when continuing, behind two off-by-default flags, with a fingerprint-mismatch circuit breaker\n\nContinuing a server-side conversation thread can now skip resending the system prompt and tools list, with a fallback if the server disagrees\n\n**Unclear.** Whether the `tengu_quiet_heron` gate is enabled for any account is unknown; the finding does not say.\n\n**What**\n\nWhen Claude Code continues an existing server-side conversation thread (a 'tether') and the previously sent data still matches, it can now leave out the `system` prompt and\/or the `tools` list from the outgoing request, trusting the server to already have them. This is tracked in telemetry as `omittedSystem`, `omittedTools`, and `omittedBytes`.\n\n- If the server rejects a continuation because its fingerprint of the conversation doesn't match, a circuit breaker trips for that session, logs a warning, and forces Claude Code to send the full system prompt and tools list for the rest of the session.\n\n- Two new tracking flags, `relayHeldStateless` and `classifierHeldStateless`, were added to related telemetry.\n\nThis behavior only runs when a gate called `tengu_quiet_heron` is turned on for an account; nothing is yet known about whether it's on anywhere.\n\n**Why**\n\nSkipping data the server already has can reduce the size of requests when continuing a long-running conversation. The fingerprint-mismatch fallback exists so that if the server and client ever disagree about what's already been sent, Claude Code recovers automatically by sending everything again rather than failing.\n\n- Flag `tengu_quiet_heron`: Not enough to say (read for one account on one subscription tier against v2.1.269; this account: no value returned, anonymous baseline: no value returned, compiled default: off)\n- Flag `tengu_lucid_anchor`: Not enough to say (read for one account on one subscription tier against v2.1.269; this account: no value returned, anonymous baseline: no value returned, compiled default: off)\n- Area: Internals\n- Tier: Nothing to try yet\n- Useful: 3\/5\n- Signal: 3\/5\n- Present in the build but not switched on"}