[BUG] /insights silently uses stale session-meta snapshots for grown/continued sessions; report prose re-rolls, masking the staleness

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

Note

I have searched existing issues. The closest match, #26358, describes the same root cause but is either closed or locked to collaborators, so I could not add this detail there — filing here with additional evidence and a second symptom.

What's Wrong?

/insights reads cached session statistics from ~/.claude/usage-data/session-meta/*.json. These snapshots are written once — in my install they all share a single mtime, i.e. generated in a batch at /insights time rather than at session creation — and are never refreshed when the session's .jsonl transcript keeps growing (e.g. via claude --continue across multiple days). All activity after the snapshot is therefore silently excluded from every report.

Concrete instance — one long-running session continued over several days:

| | cached session-meta | live .jsonl |
|---|---|---|
| last written (mtime) | 2026-06-06 16:30 | 2026-06-11 19:15 |
| user_message_count | 40 | 539 |

The cache undercounts this session by 499 user messages and is ~5 days stale. Notably, the snapshot's mtime is still Jun 6 even though I ran /insights again later on Jun 6 and again today (Jun 11) — so re-running /insights does not invalidate or refresh an existing snapshot; it is effectively write-once.

Second symptom — misleading freshness: across three /insights runs (two on Jun 6, one today), the narrative report prose is re-generated each time — wording and framing vary — but the substance is identical, because the inputs are frozen. That cosmetic variation makes a stale report look freshly computed, with no cue that the meaningful content has actually not been updated.

What Should Happen?

The underlying issue is a cache-invalidation gap. Any of the following resolves it (in order of preference):

1. Regenerate a session-meta entry when the matching .jsonl mtime/size has advanced since the snapshot, so /insights always reflects the full session.
2. Failing that, surface a visible staleness warning when a snapshot predates its .jsonl (e.g. "Note: N messages recorded after the last metadata snapshot are not reflected in this report").
3. Do not re-generate the narrative report prose when the underlying data is unchanged, so the report stops misleadingly implying a freshness it doesn't have.

Likely the same "metadata captured once, never refreshed" class as #20406 (gitBranch metadata). Related but distinct: #22030 (stale sessions-index.json undercounts messages on --resume).

Error Messages/Logs

# session-meta cache vs. live transcript for one continued session (ids truncated)
$ stat -c '%y %n' session-meta/b96ca6ab-*.json projects/-workspace/b96ca6ab-*.jsonl
2026-06-06 16:30   session-meta/b96ca6ab-*.json          # cache, frozen
2026-06-11 19:15   projects/-workspace/b96ca6ab-*.jsonl  # live transcript, grew 5 days later

cached user_message_count : 40
live   user message count : 539      # Δ = 499 unrecorded

# No error is emitted — the staleness is silent.

Steps to Reproduce

1. Start a session, do some work, and run /insights.
2. Continue the same session with claude --continue over one or more later days, adding many more messages.
3. Run /insights again (even days later).
4. Observe: that session's session-meta/*.json mtime and counts are unchanged from step 1; the report's stats and the meaning of its prose are identical, while the live .jsonl has grown substantially.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.173

Platform

Anthropic API

Operating System

Other Linux - A Docker devcontainer running Linux 6.12.76-linuxkit

Terminal/Shell

Other - A Docker devcontainer launched from Windows Command Prompt (not Windows Terminal)

Additional Information