halo-format-openai 0.4.0

Halo host adapter for the OpenAI Agents SDK (Python): a call_model_input_filter that swaps large tool results for a shape map (out of context) plus a halo_fetch navigation tool. install_halo() wires it in one call.

halo-format-openai

Halo host adapter for the OpenAI Agents SDK (Python). install_halo() wires it in one call:

• a call_model_input_filter — the interception seam on this host. The OpenAI Agents SDK has no tool-return output-replacement hook (on_tool_end is observational), so this filter, which rewrites the assembled model input before each model call, is the only generic point that catches every tool — including external/MCP/hosted tools your app does not own. Above a size threshold it replaces a large tool result with a halo shape map (root kind + one line per field: ref, kind, and a bounded preview), so the payload stays out of the model's context while it still sees what's there;
• a single halo_fetch function tool the model uses to pull back only the leaves it needs, verified on read — a ref that lands on a branch returns that branch's sub-refs, so one batch API both pulls and expands (there is no separate halo_walk).

from agents import Agent, Runner, RunConfig
from halo_format_openai import install_halo

result = install_halo(tools=my_tools)
agent = Agent(name="assistant", tools=result.tools)
out = await Runner.run(
    agent, "…",
    run_config=RunConfig(call_model_input_filter=result.call_model_input_filter),
)
# result.session holds the shared store for audit/inspection

Because the filter fires before every model call over the whole input list (not once per tool return), the adapter correlates each function_call_output to its function_call by call_id — both to skip halo_fetch's own output (the mandatory no-re-encode rule) and to feed entity accumulation the real tool name/args — and caches each encoded result by call_id so repeated firings stay idempotent. The filter is deterministic plumbing (it always runs, for every tool); the Halo Skill (or prompt-mode guidance) is the navigation behavior. Pass store=FileStore(dir) for the heavy/persistent deployment. The core engine is halo-format; this package is only the shim.