feat: add context compaction to the rlm harness

verifiers/v1/harnesses/bash/harness.py

@@ -1,5 +1,8 @@
 import os
 
+from pydantic import PositiveInt
+from pydantic_config import BaseConfig
+
 from verifiers.v1.clients import ModelContext
 from verifiers.v1.configs.harness import HarnessConfig
 from verifiers.v1.harness import Harness
@@ -24,6 +27,14 @@
 )
 
 
+class CompactionConfig(BaseConfig):
+    """Context compaction policy for the bash agent loop."""
+
+    summarize_at_tokens: PositiveInt | None = None
+    """Compact at this token count. When unset, compact when 16k tokens remain below the
+    model context window when the provider advertises it."""
+
+
 class BashHarnessConfig(HarnessConfig):
     edit: bool = True
     """Offer the local `edit` tool (single-occurrence string replacement in a file) alongside
@@ -34,6 +45,9 @@ class BashHarnessConfig(HarnessConfig):
     eval environment; the key is handed to the program over argv (like the interception secret) so
     the agent's `bash` subprocesses don't inherit it."""
 
+    compaction: CompactionConfig | None = None
+    """Context compaction policy. Set an empty config to use automatic thresholds."""
+
 
 class BashHarness(Harness[BashHarnessConfig]):
     APPENDS_SYSTEM_PROMPT = True
@@ -69,6 +83,11 @@ async def launch(
         args = ["--bash"]
         if tool_interception_url:
             args.append(f"--tool-interception-url={tool_interception_url}")
+        if self.config.compaction is not None:
+            args.append("--compaction")
+            threshold = self.config.compaction.summarize_at_tokens
+            if threshold is not None:
+                args.append(f"--summarize-at-tokens={threshold}")
         if self.config.edit:
             args.append("--edit")
         if self.config.search: