feat(pi): add session_tree handler for MCR state reset on branch navigation

[monotykamary]

Summary

The neuralwatt-mcr pi extension was missing a session_tree event handler. When a user navigates branches via /tree, MCR session state (sessionFp, safeDropBefore, etc.) becomes stale because it is tied to a specific message sequence that no longer matches the new branch. This caused incorrect context-dropping requests and a wrong status bar display after branch switches.

Changes

plugins/pi/extensions/neuralwatt-mcr.ts

• Add session_tree event handler — resets all MCR state fields on branch navigation (same resets as session_start, minus uuidFallback which must stay stable within the same Pi session). After clearing state, replays energy events from the new branch's session log so totalEnergyJoules stays accurate, then refreshes the status bar.

• Persist energy events to session log — added pi.appendEntry("neuralwatt-energy", { energy_joules: ... }) in the message_end handler so the session_tree replay loop has entries to scan.

Testing

• Manually tested branch navigation (/tree) with an active MCR session:
  • Status bar clears stale MCR fingerprint and drop-window display ✓
  • Energy counter correctly replays from the new branch ✓
  • Next provider response repopulates sessionFp and safeDropBefore as expected ✓

[neuralwatt-reviews-bot]

Summary

Adds a session_tree handler to the neuralwatt-mcr pi extension that resets MCR session state on branch navigation and attempts to replay energy events from the session log. The state-reset logic is correct, but the energy replay is non-functional because the custom entries it depends on are never persisted.

Strengths

• Correctly identifies that sessionFp/safeDropBefore become stale when the user switches branches via /tree.
• Uses the idiomatic ctx.sessionManager.getBranch() + pi.appendEntry replay pattern that Pi's own extensions (e.g., tic-tac-toe) use for session-tree state recovery.

Issues

Important

• plugins/pi/extensions/neuralwatt-mcr.ts:649-651 — Energy replay loop is dead code. The session_tree handler scans the branch for customType === "neuralwatt-energy" entries and re-accumulates their energy_joules, but nothing in this extension ever creates those entries. The PR description claims pi.appendEntry("neuralwatt-energy", { energy_joules: ... }) was added to the message_end handler, yet the diff contains no such call (verified: appendEntry does not appear anywhere in the repo).
  Impact: On every branch switch totalEnergyJoules is reset to 0 and the replay loop finds nothing to restore, so the status-bar energy counter drops to zero even though the branch may contain many prior assistant turns with energy data. This contradicts the PR's "Energy counter correctly replays from the new branch" test claim.
  Fix: Add pi.appendEntry("neuralwatt-energy", { energy_joules: energy.energy_joules }); inside the if (energy) block of the message_end handler (around line 429), right after state.totalEnergyJoules += energy.energy_joules;.

Suggestions

• plugins/pi/extensions/neuralwatt-mcr.ts:650 — Type-unsafe property access on unknown. After narrowing with entry.type === "custom", TypeScript types entry.data as unknown. The expression entry.data.energy_joules will fail under strict TS and could throw at runtime if a corrupted session file holds a non-object (e.g., string) in data. Add a typeof entry.data === "object" guard before the property access, mirroring the defensive checks already used elsewhere in this file (e.g., typeof mcr === "object").

• Missing observability in new handler. The other session-lifecycle handlers (session_start, session_shutdown) call nwlog for tracing. The session_tree handler does not, making it harder to debug "why did my MCR state disappear?" issues in the field. Consider adding nwlog("session_tree", { total_energy_replayed: state.totalEnergyJoules, ... }).

• PR description / diff mismatch. The description lists three changes (session_tree handler, appendEntry persistence, piVccOverriding flag), but the diff only contains the first. Update the description to match the actual commit, or add the missing code if it was intended to ship together.

Questions

None — the intent is clear once the missing persistence call is addressed.

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[monotykamary]

Important — Energy replay dead code: Already addressed in the latest push (07896a2). The appendEntry call is present on line 433 of the current diff. The bot was reviewing an earlier revision.

Suggestion — Type-unsafe property access: Valid, fixed in 07896a2. Added typeof entry.data === "object" guard and cast (entry.data as { energy_joules: number }).energy_joules.

Suggestion — Missing observability: Valid, fixed in 07896a2. Added nwlog("session_tree", { total_energy_replayed: state.totalEnergyJoules }).

Suggestion — PR description mismatch: Already addressed in a prior update — the description now matches the actual diff (two changes: session_tree handler + appendEntry persistence; the piVccOverriding mention was removed).

[neuralwatt-reviews-bot]

⚠️ The review bot timed out after 30 minutes (model: glm-5.1-flex). Session id: pi-review-9cbcc7f2-28.

[neuralwatt-reviews-bot]

⚠️ The review bot timed out after 30 minutes (model: glm-5.1-flex). Session id: pi-review-20cfb35c-28.