feat(memory): add incremental transcript compaction

artemis/memory/__init__.py

@@ -0,0 +1,84 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Shared step-memory runtime for background summarization across profiles."""
+
+from artemis.memory.chunking import (
+    ChunkCapsuleService,
+    HistoryChunkManager,
+    StepCapsuleLens,
+    build_action_ledger,
+)
+from artemis.memory.context_policy import (
+    CONTEXT_POLICIES,
+    ContextPolicy,
+    build_history_for,
+    resolve_policy,
+)
+from artemis.memory.step_memory import StepLens, StepMemoryService
+from artemis.memory.transcript import TranscriptLedger, format_session_offset
+
+
+def ensure_step_memory(ctx):
+    """Return the session's shared step-memory service, creating it on demand.
+
+    Composition root for ``ctx.step_memory`` (history redesign §6.2): the
+    first caller — FlashRunner, the Pro SummarizerNode, or the Pro operator's
+    transcript path — instantiates the visual-transition lens service and
+    publishes it on the context so every profile shares one runtime.
+    """
+    service = getattr(ctx, "step_memory", None)
+    if service is not None:
+        return service
+
+    from artemis.agents.flash.summarizer import VisualStepSummarizer
+
+    kwargs: dict = {}
+    model_name = None
+    try:
+        from artemis.config import load_agent_config
+
+        cfg = load_agent_config()
+        model_name = cfg.flash.step_summarizer.model
+        kwargs = {
+            "retry_limit": cfg.memory.runtime.retry_limit,
+            "max_concurrency": cfg.memory.runtime.max_concurrency,
+            "flush_timeout_s": cfg.memory.runtime.flush_timeout_s,
+        }
+    except Exception:
+        pass
+
+    service = VisualStepSummarizer(ctx, model_name=model_name, **kwargs)
+    try:
+        ctx.step_memory = service
+    except Exception:
+        pass
+    return service
+
+
+__all__ = [
+    "CONTEXT_POLICIES",
+    "ChunkCapsuleService",
+    "ContextPolicy",
+    "HistoryChunkManager",
+    "StepCapsuleLens",
+    "build_history_for",
+    "resolve_policy",
+    "StepLens",
+    "StepMemoryService",
+    "TranscriptLedger",
+    "build_action_ledger",
+    "ensure_step_memory",
+    "format_session_offset",
+]