Problem

When using compaction.mode: "safeguard", the compaction summarization fails because ctx.model is undefined in the session_before_compact event handler.

This happens because compact.js calls createAgentSession directly without going through ExtensionRunner.initialize(), which is the only place that sets ctx.model.

As a result, compaction falls back to a static summary instead of LLM-generated summarization, causing context loss.

Solution

Pass the model through the runtime registry (same pattern used for contextWindowTokens and maxHistoryShare):

1. Add model field to CompactionSafeguardRuntimeValue type
2. Store params.model in setCompactionSafeguardRuntime() call
3. Fall back to runtime?.model when ctx.model is undefined

Testing

Tested locally with compaction.mode: "safeguard" - compaction now produces proper LLM summaries instead of falling back to static text.

AI-assisted (Claude) - fully tested on local OpenClaw instance.

Greptile Overview

Greptile Summary

This PR threads the selected model into the compaction safeguard runtime so the session_before_compact handler can still perform LLM summarization when ctx.model is unset (notably in the compact.js workflow that bypasses ExtensionRunner.initialize()). Concretely, it (1) adds a model field to the session-scoped CompactionSafeguardRuntimeValue, (2) stores params.model when building embedded extension paths, and (3) falls back to runtime?.model in compaction-safeguard when ctx.model is undefined.

This fits the existing “session-scoped runtime registry keyed by sessionManager identity” pattern already used for compaction/pruning runtimes, and should reduce fallback-to-static-summary behavior when compaction runs outside the normal initialization path.

Confidence Score: 4/5

• This PR is likely safe to merge and addresses a real initialization-path gap, with minor risk around tests/typing edge cases.
• Changes are small and follow an existing runtime-registry pattern. Main risk is that existing tests or strict equality checks against the runtime object may break now that the runtime type includes an extra field, and that storing model in runtime could introduce subtle identity/serialization assumptions elsewhere (though none are evident in the reviewed code).
• src/agents/pi-extensions/compaction-safeguard.test.ts (update expectations if failing); src/agents/pi-extensions/compaction-safeguard-runtime.ts (type import usage)

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