Release v0.26.4

What's Changed

• fix(local): report registered model context windows by @cpacker in #2575
• fix(bootstrap): calibrate conversation relevance threshold by @kianjones9 in #2581
• fix(nix): nix flake fixes and improvements by @michaelBelsanti in #2517
• feat(hooks): allow hooks to rewrite tool input by @michaelBelsanti in #2518
• fix(local): reject default conversation renames by @cpacker in #2580
• fix(local): lazy-load transcripts on startup by @cpacker in #2582
• feat(headless): wire bidirectional reflection by @devanshrj in #2435
• feat(local): support extension providers in local models by @carenthomas in #2587
• fix(local): keep provider registry replacement semantics by @carenthomas in #2589
• feat(telemetry): segment Letta Code usage events by @overlord-letta in #2568
• feat(models): add Claude Opus 4.8 by @overlord-letta in #2584
• feat(local): persist v2 session transcripts by @cpacker in #2585
• feat(cli): add skill management commands by @sarahwooders in #2588
• docs: add skill install source table by @sarahwooders in #2591
• Update README.md by @sarahwooders in #2593
• fix(telemetry): use correct relative import and add lint rule by @christinatong01 in #2595
• fix(auth): fix stale credential reauth flow by @cpacker in #2592
• feat(local): support OAuth extension providers by @carenthomas in #2590
• ci: sync src/tools changes to letta-cloud via Amelia by @carenthomas in #2597
• feat(extensions): add tool_start event by @carenthomas in #2598
• chore: bump version to 0.26.4 by @github-actions[bot] in #2594

Full Changelog: v0.26.3...v0.26.4