Delegated Context Editing (Anthropic)

Delegated Context Editing is a Claude-only context-management feature. Unlike OmniRoute’s local compression engines (Caveman, RTK, LLMLingua, stacked pipelines) — which rewrite the request body before it leaves the proxy — Context Editing asks the provider to clear stale tool-use / tool-result blocks from its own running context window. OmniRoute only attaches a body parameter (context_management.edits[]); Claude does the actual clearing against its own tokenizer.

This is a delegated capability by nature: other providers reject the parameter, so OmniRoute scopes it strictly to Claude and Claude-Code-compatible relays.

Source of truth: open-sse/config/contextEditing.ts (strategy ids, body injection, telemetry extraction), open-sse/executors/base.ts (injection gate + 400-fallback), and open-sse/services/compression/types.ts (config shape + default).

What clear_tool_uses does

OmniRoute injects a single edit into the outbound Anthropic Messages body:

{
  "context_management": {
    "edits": [
      {
        "type": "clear_tool_uses_20250919",
        "trigger": { "type": "input_tokens", "value": 100000 },
        "keep": { "type": "tool_uses", "value": 3 }
      }
    ]
  }
}

• type: "clear_tool_uses_20250919" — the dated Anthropic strategy id (CLEAR_TOOL_USES_STRATEGY).
• trigger.value: 100000 — once the request’s input tokens exceed this threshold, Claude begins clearing old tool-use/result pairs (CONTEXT_EDITING_DEFAULT_TRIGGER_TOKENS, Anthropic’s default).
• keep.value: 3 — the N most recent tool-use/result pairs are kept untouched (CONTEXT_EDITING_DEFAULT_KEEP_TOOL_USES).

The beta is advertised via the anthropic-beta: context-management-2025-06-27 header, which OmniRoute already emits on Claude requests.

Injection is performed by applyContextEditingToBody() and is idempotent: if a clear_tool_uses edit already exists on the body (added by a previous call or supplied by the client), the body is left as-is. If a clear_thinking_20251015 edit is also present, OmniRoute stable-sorts the clear_thinking edit to the front, because Anthropic requires clear_thinking to precede clear_tool_uses in the edits[] array.

The per-combo enable toggle

Context Editing is off by default and opt-in. The toggle is a single boolean carried in the compression config:

• Setting key: contextEditing.enabled (camelCase — not context_editing / context-editing).
• Type: ContextEditingConfig { enabled: boolean } in open-sse/services/compression/types.ts.
• Default: DEFAULT_CONTEXT_EDITING_CONFIG = { enabled: false }.
• Zod schema: contextEditingConfigSchema in src/shared/validation/compressionConfigSchemas.ts.
• Storage: persisted with the rest of the compression settings (normalized in src/lib/db/compression.ts).

In the dashboard the toggle lives in the compression hub (src/app/(dashboard)/dashboard/context/combos/CompressionHub.tsx) and writes { contextEditing: { enabled: … } } back through saveSettings(). Because it rides on the compression-settings object, it composes with the per-combo compression profile rather than being a fully independent surface — the config carries only the on/off flag; all thresholds (trigger, keep) are the constants documented above.

Claude-only gating

Injection only happens for genuine Claude or Claude-Code-compatible relays. The gate in open-sse/executors/base.ts is:

if (
  (this.provider === "claude" || isClaudeCodeCompatible(this.provider)) &&
  contextEditing?.enabled &&
  !contextEditingDisabled
) {
  applyContextEditingToBody(transformedBody, { enabled: true });
}

• this.provider === "claude" — real Anthropic key/OAuth.
• isClaudeCodeCompatible(this.provider) — relays whose provider id starts with the anthropic-compatible-cc- prefix (they advertise Claude Code compatibility, so they are the relays most likely to accept the beta). See open-sse/services/provider.ts.

Deliberately excluded:

• claude-web — a browser relay with a create_conversation_params request shape that never sees context_management.
• Generic anthropic-compatible-* relays (without the -cc- prefix) — third-party endpoints with uncertain beta support.

Non-Claude providers never receive the context_management parameter even when the toggle is on.

The 400-fallback / relay coverage

A Claude-compatible relay may advertise the beta but still reject the context_management parameter with an HTTP 400. To degrade gracefully instead of failing the request, the executor strips the parameter and retries the same URL once:

if (
  response.status === HTTP_STATUS.BAD_REQUEST &&
  contextEditing?.enabled &&
  !contextEditingDisabled &&
  transformedBody?.context_management !== undefined
) {
  const errText = await response
    .clone()
    .text()
    .catch(() => "");
  if (/context[_-]management|context editing/i.test(errText)) {
    contextEditingDisabled = true;
    delete transformedBody.context_management;
    let retryBody = JSON.stringify(transformedBody);
    if (isClaudeCodeCompatible(this.provider) || this.provider === "claude") {
      retryBody = await signRequestBody(retryBody);
    }
    response = await fetch(url, { ...fetchOptions, body: retryBody });
  }
}

Behavior:

1. Fires only on a 400 while context editing is enabled and the body actually carries context_management.
2. The 400 body is read via a clone() so the original response stays intact for the non-matching path.
3. The error text must match /context[_-]management|context editing/i — an unrelated 400 (e.g. max_tokens must be >= 1) does not trigger the fallback; the original error propagates.
4. On a match it sets contextEditingDisabled = true (which suppresses re-injection if a fresh transformedBody is later built for a retry/fallback URL), deletes context_management, re-signs the body for Claude / Claude-Code-compatible relays (signRequestBody), and retries the same URL once.

Genuine Claude carries the beta in ANTHROPIC_BETA_BASE and does not hit this fallback path.

applied_edits telemetry

After a Claude response, OmniRoute records how much context the provider actually cleared. This is not streamed — it is extracted from the non-streaming response body, best-effort, and never affects the response (telemetry failures are swallowed).

• Extraction: extractContextEditingTelemetry(responseBody) in open-sse/config/contextEditing.ts. It probes applied_edits in three locations (defensive over the response shape):
  • context_management.applied_edits
  • usage.context_management.applied_edits
  • usage.applied_edits
• Per-edit fields read from each entry: cleared_input_tokens and cleared_tool_uses (snake_case, Anthropic-native), with clearedInputTokens / clearedToolUses camelCase fallbacks.
• Returns null when no applied_edits array is found or nothing was actually cleared.

The receipt shape is ContextEditingTelemetry { editCount, clearedInputTokens, clearedToolUses }. Recording happens in open-sse/handlers/chatCore.ts (gated to provider === "claude") via recordContextEditingTelemetry() (src/lib/db/compressionAnalytics.ts), which writes a compression analytics row tagged:

• mode: "context-editing"
• engine: "context-editing"
• tokens_saved / original_tokens = the cleared input-token count
• request_id suffixed with ::context-editing

So delegated clearing shows up in compression analytics alongside the local engines, under the context-editing engine label, and is distinguishable from RTK/Caveman/LLMLingua savings.

Relationship to the local compression engines

Aspect	Local engines (Caveman / RTK / LLMLingua / stacked)	Delegated Context Editing
Where it runs	In OmniRoute, before the request leaves the proxy	In the provider (Claude), server-side
What it edits	Prompt / context / tool-result text	Old tool-use / tool-result blocks
Provider scope	All providers	claude + anthropic-compatible-cc-* only
Toggle	Compression mode settings	contextEditing.enabled
Failure mode	Fail-open (original text)	400-fallback: strip param, retry once
Savings telemetry	engine: <engine id>	engine: "context-editing"

The two are complementary: local engines compress the bytes OmniRoute sends; Context Editing lets Claude prune the running context across turns. They can be enabled together.

See Also

• COMPRESSION_ENGINES.md — engine registry and the local compression engines
• RTK_COMPRESSION.md — command/tool-output compression
• ../frameworks/MCP-SERVER.md — MCP description compression and tool-cardinality reduction
• Source: open-sse/config/contextEditing.ts, open-sse/executors/base.ts, open-sse/services/compression/types.ts, src/lib/db/compressionAnalytics.ts

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