fix: handle compaction boundaries without metadata

[MattPua]

Problem

Codex emits _posthog/compact_boundary without Claude's optional trigger, preTokens, and contextSize metadata. The UI treated those fields as required, so Codex compactions rendered as Conversation compacted · undefined · ~NaNK tokens.

With Codex

Changes

• Make compaction metadata optional through the conversation builder and render types.
• Render only metadata that exists while preserving the existing detailed Claude output.
• Share the compaction boundary types instead of repeating the payload shape.
• Add coverage for metadata-free Codex boundaries and both UI label formats.

How did you test this?

• pnpm --dir packages/ui exec vitest run src/features/sessions/components/session-update/CompactBoundaryView.test.ts src/features/sessions/components/buildConversationItems.test.ts
• pnpm --filter @posthog/ui typecheck
• Commit hook: pnpm typecheck
• Biome checks on touched files

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

---

Created with PostHog Code

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[github-actions]

React Doctor found 2 issues in 1 file · 2 warnings.

2 warnings

src/features/sessions/components/session-update/CompactBoundaryView.tsx

• ⚠️ src/features/sessions/components/session-update/CompactBoundaryView.tsx:34 Non-component export in component file only-export-components
• ⚠️ src/features/sessions/components/session-update/CompactBoundaryView.tsx:50 Non-component export in component file only-export-components

_{Reviewed by React Doctor for commit 4cb16f2.}

[greptile-apps]

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[greptile-apps]

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