Add StepPersistence capability for step-event durability across delegates

.gitignore

@@ -2,6 +2,8 @@
 .mcp.json
 .DS_Store
 .agents/settings.local.json
+.agents/skills/branch-context/
+AGENTS.local.md
 CLAUDE.local.md
 LOCAL_WORKTREES.md
 

pydantic_ai_harness/__init__.py

@@ -1,4 +1,4 @@
-"""Pydantic AI capability library."""
+"""The batteries for your Pydantic AI agent -- the official capability library."""
 
 from typing import TYPE_CHECKING
 
@@ -7,8 +7,63 @@
     from .filesystem import FileSystem
     from .logfire import ManagedPrompt
     from .shell import Shell
+    from .step_persistence import (
+        ContinuableSnapshot,
+        EventKind,
+        FileStepStore,
+        InMemoryStepStore,
+        RunRecord,
+        SqliteStepStore,
+        StepEvent,
+        StepPersistence,
+        StepStore,
+        ToolEffectRecord,
+        ToolEffectStatus,
+        annotate_tool_effect,
+        continue_run,
+        fork_run,
+        is_provider_valid,
+    )
 
-__all__ = ['CodeMode', 'FileSystem', 'ManagedPrompt', 'Shell']
+__all__ = [
+    'CodeMode',
+    'ContinuableSnapshot',
+    'EventKind',
+    'FileStepStore',
+    'FileSystem',
+    'InMemoryStepStore',
+    'ManagedPrompt',
+    'RunRecord',
+    'Shell',
+    'SqliteStepStore',
+    'StepEvent',
+    'StepPersistence',
+    'StepStore',
+    'ToolEffectRecord',
+    'ToolEffectStatus',
+    'annotate_tool_effect',
+    'continue_run',
+    'fork_run',
+    'is_provider_valid',
+]
+
+_STEP_PERSISTENCE_NAMES = {
+    'ContinuableSnapshot',
+    'EventKind',
+    'FileStepStore',
+    'InMemoryStepStore',
+    'RunRecord',
+    'SqliteStepStore',
+    'StepEvent',
+    'StepPersistence',
+    'StepStore',
+    'ToolEffectRecord',
+    'ToolEffectStatus',
+    'annotate_tool_effect',
+    'continue_run',
+    'fork_run',
+    'is_provider_valid',
+}
 
 
 def __getattr__(name: str) -> object:
@@ -28,4 +83,8 @@ def __getattr__(name: str) -> object:
         from .shell import Shell
 
         return Shell
+    if name in _STEP_PERSISTENCE_NAMES:
+        from . import step_persistence
+
+        return getattr(step_persistence, name)
     raise AttributeError(f'module {__name__!r} has no attribute {name!r}')

pydantic_ai_harness/media/__init__.py

@@ -0,0 +1,39 @@
+"""Content-addressed media stores for offloading large binary parts.
+
+Used by `pydantic_ai_harness.step_persistence` to keep snapshots small when
+messages carry `BinaryContent` payloads. Public API is intentionally small
+and stable; a forthcoming `MediaExternalizer` capability will reuse these
+stores for in-flight wire-payload reduction (rewriting `BinaryContent` to
+URL parts before the model sees them).
+"""
+
+from pydantic_ai_harness.media._s3 import S3MediaStore
+from pydantic_ai_harness.media._store import (
+    DiskMediaStore,
+    KeyStrategy,
+    MediaContext,
+    MediaStore,
+    PublicUrlResolver,
+    SqliteMediaStore,
+    default_key_strategy,
+    make_static_public_url,
+    media_uri_for,
+    parse_media_uri,
+)
+from pydantic_ai_harness.media._walker import externalize_media, restore_media
+
+__all__ = [
+    'DiskMediaStore',
+    'KeyStrategy',
+    'MediaContext',
+    'MediaStore',
+    'PublicUrlResolver',
+    'S3MediaStore',
+    'SqliteMediaStore',
+    'default_key_strategy',
+    'externalize_media',
+    'make_static_public_url',
+    'media_uri_for',
+    'parse_media_uri',
+    'restore_media',
+]