Composition Execution Budgets in DocsFab

Look up how provider-turn, time, response-byte, and cumulative-token budgets combine for a composition execution attempt.

Optional host-owned ceilings are DOCSFAB_COMPOSITION_EXECUTION_MAX_PROVIDER_TURNS (default 512), DOCSFAB_COMPOSITION_EXECUTION_TIMEOUT_MS (default 3600000), and DOCSFAB_COMPOSITION_EXECUTION_MAX_RESPONSE_BYTES (default 4194304). The effective value is the minimum of the host setting, candidate proposal, installed composition, and package ceiling. These are experiment settings, not provider facts.

A raised host default does not override a narrower installed composition. The GPT-6 Sol and two Anthropic Claude records on the NVIDIA Inference Hub route seal 1,800,000 ms and 512 provider turns. Other installed compositions seal 300,000 ms and 128 turns. The 3,600,000 ms host default therefore does not grant these compositions 1-hour attempts. DOCSFAB_COMPOSITION_EXECUTION_TIMEOUT_MS bounds one workflow step attempt, not the job. A hosted run is separately bounded by the dispatcher policy’s runtime.deadlineMilliseconds, which the host contract caps at 10800000 (three hours).

Because the effective value is a minimum across four sources, raising the host setting cannot lift a smaller candidate, composition, or package ceiling. Three of those four are digest-sealed governance assets, so widening the envelope means re-sealing the chain, not editing an environment variable.

DOCSFAB_COMPOSITION_EXECUTION_MAX_PROVIDER_TURNS also sizes the per-step tool budget, which is not independent of it: the execution-lease contract requires maxProviderTurns >= hardToolCallCeiling + maxLeases, so the turn budget is a hard cap on how many tool calls a step can make. The shape is fitted to whichever turn budget a lane actually seals, so the number differs per lane: a lane sealed at 512 turns yields a policy ceiling of 400 tool calls, and one sealed at 128 yields 126. Compare that with a measured P100 of 54 tool calls and 24 provider turns per step across twelve models (packages/runtime/docs/internal/evidence/model-comparison-single-mode-2026-08-27/).

Whether a step reaches its lane’s 126- or 400-call policy ceiling also depends on cumulative tokens and the attempt deadline. DOCSFAB_COMPOSITION_EXECUTION_MAX_CUMULATIVE_INPUT_TOKENS defaults to 16777216, and DOCSFAB_COMPOSITION_EXECUTION_MAX_CUMULATIVE_OUTPUT_TOKENS defaults to 4194304. Both budgets apply to one step attempt. These defaults use their existing catalog maxima by operator choice. The historical model measurements do not establish these amounts as sufficient for every workload. Use the recorded usage and stopping reason to identify the bound that a run actually reaches.

The previous default of 4 yielded a 3-call ceiling and could not complete create-documentation for any model. Steps that exhaust either budget now fail rather than reporting succeeded; before that change a truncated run was indistinguishable from a finished one, so an envelope sized below every real workflow produced confident, empty successes.

DOCSFAB_COMPOSITION_EXECUTION_MAX_RESPONSE_BYTES bounds the raw provider response on the wire, not the decoded document. Per-token JSON framing means the wire bytes greatly exceed the document bytes, by a ratio that varies with the provider’s streaming format and token size. The content this setting admits therefore differs by model even when the setting does not. Size it against the wire, and measure your own lane rather than assuming a ratio.

For scale, the one retained measurement: a nemotron-3.5-lightning-30b-a3b composition-execution step exceeded a 65,536-byte cap at 65,834 wire bytes across 199 SSE events while producing a document far smaller than that (packages/runtime/docs/internal/evidence/pi-client-instrumentation-2026-08-24/report.md). That probe records wire bytes and event counts only (model output is never written to evidence), so the probe bounds the wire side and not the ratio.