Agent Session Protocol

Fidelity

Declared per-axis fidelity and resume profiles

Declared, not promised

ASP's core stance: conversion fidelity is declared, never assumed. Every importer/exporter declares, per axis, a fidelity level and a loss list.

levelmeaning
preservedsurvives round-trip
partialdegraded (merged, re-encoded)
evidence-onlykept in evidence, not in the canonical projection
droppeddropped with a declared reason
not-in-sourcethe source harness does not record this axis

Measured (4 harnesses)

axispiclaudecodex
messages / orderpreservedpreserved (block-append merged)preserved (dual-stream dedup)
tool chainpreservedpreservedpreserved
thinkingpreserved (signature)preserved (signature)partial (summary→thinking; encrypted blob → unknown passthrough)
run/turn boundariespartialpartialpreserved (turn_context)

Resume profiles

Handoff fidelity means the exporter knows what the target harness needs to resume. Missing required fields → refuse to export (never silently degrade); non-required → declare loss.

The evidence layer

Round-trip fidelity comes from the evidence layer (the full ordered event stream), not the projection: exporters replay the importer's native payloads verbatim, synthesizing only when absent.

Full detail: asp/spec/fidelity.md.

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