Summary

Fixes a Solid stale <Show> accessor read in SessionContextUsage by avoiding callback accessors for context usage tooltip content.

Why

Production v2026.5.29 can throw Stale read from <Show> while switching sessions. The issue was first filed as #985. The release regression was exposed by PR #969 keeping the composer mounted during session opening; Claude's read-only review agreed that restoring the composer guard would be a symptom fix that regresses #969, and that the smaller root fix is to stop passing volatile context accessors through non-keyed <Show> children inside the composer subtree.

Related Issue

Fixes #985

Human Review Status

Pending

Review Focus

Please check that the tooltip still renders the same context/cost information while no longer using callback-form <Show> accessors for values that can disappear during session transitions.

Risk Notes

Low risk. This keeps the #969 composer mount behavior intact and only changes the render shape inside the context usage tooltip. Review follow-up replaced the brittle source-string render contract with a browser-condition test that renders SessionContextUsage itself and clears the mocked session messages so context metrics disappear. Platform/packaging surfaces were not touched. Docs, dependencies, permissions, generated files, and local file behavior were not touched.

How To Verify

Diff check: git diff --check passed
Focused tests: bun test --preload ./happydom.ts ./src/components/session/session-context-metrics.test.ts ./src/components/session-context-usage.test.ts passed, 13 tests, including a SessionContextUsage render regression for disappearing context metrics
Typecheck: bun run typecheck passed in packages/app
Visual check: bun run snap session-context-cache passed; reviewed docs/design/preview/screenshots/session-context-cache.png

Screenshots or Recordings

Visual snap checked locally: docs/design/preview/screenshots/session-context-cache.png (session-context-cache).

Checklist

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