Method ensureChildActive

packages/runtime/src/runtime-kernel.ts:2898–2952

(
    activeKey: string,
    sessionId: string,
    header: SessionHeader,
    systemPrompt: string,
    tools: readonly MakaTool[],
    execution: PendingExecutionClaim,
  )

  }

  private async ensureChildActive(
    activeKey: string,
    sessionId: string,
    header: SessionHeader,
    systemPrompt: string,
    tools: readonly MakaTool[],
    execution: PendingExecutionClaim,
  ): Promise<BackendGeneration> {
    await this.clearBackendQuarantineForActivation(sessionId, execution);
    let existing = this.childActive.get(activeKey);
    if (existing) {
      existing.cachedHeader = header;
      return existing;
    }
    await this.waitForBackendDisposal(sessionId);
    existing = this.childActive.get(activeKey);
    if (existing) {
      existing.cachedHeader = header;
      return existing;
    }
    const entry = await this.shareBackendActivation(`child:${activeKey}`, async () => {
      const current = this.childActive.get(activeKey);
      if (current) return current;
      const backend = await this.deps.backends.build(header.backend, {
        sessionId,
        workspaceRoot: header.workspaceRoot,
        header,
        store: this.deps.store,
        abortSignal: execution.abortController.signal,
        appendMessage: async () => {},
        systemPrompt,
        tools,
        ...this.buildBackendRecorderHooks({
          resolveActive: () => this.childActive.get(activeKey),
          sessionId,
        }),
        // A child-only ledger cannot claim coverage of the parent session prefix.
        allowMidTurnHistoryCompaction: false,
      });
      await this.rejectCancelledBackendActivation(
        backend,
        header,
        { kind: 'child', activeKey },
        execution,
      );
      const generation = this.createBackendGeneration(sessionId, backend, header, {
        kind: 'child',
        activeKey,
      });
      this.childActive.set(activeKey, generation);
      return generation;
    });
    entry.cachedHeader = header;
    return entry;
  }

  private async reserveParentRun(
    sessionId: string,