Greptile Summary

This PR fixes a critical crash-loop bug in the Matrix gateway by removing the .toLowerCase() call applied to group/channel peer IDs in buildAgentPeerSessionKey. Because Matrix room IDs are case-sensitive opaque identifiers, the previous lowercasing caused delivery-recovery retries to use an invalid room ID, receiving a 403 from the homeserver and permanently crashing the sync loop.

• src/routing/session-key.ts: Correctly removes .toLowerCase() from the non-direct peer ID path; the direct/DM path retains lowercasing (Matrix user IDs are case-insensitive).
• src/routing/session-key.continuity.test.ts: Two new regression tests confirm channel and group session keys preserve original case.
• Inconsistency introduced: The sibling buildGroupHistoryKey function (line 230) still calls .toLowerCase() on peerId. Now that session keys preserve case but history keys do not, any code that correlates the two for the same Matrix room will produce mismatched keys — likely causing history-lookup failures for group channels.

Confidence Score: 4/5

Safe to merge after addressing the residual .toLowerCase() call in buildGroupHistoryKey, which creates a case-mismatch between session keys and history keys for Matrix rooms.

The core fix is correct and well-tested. However, the sibling buildGroupHistoryKey function still lowercases peerId, which will produce a key inconsistency with the now-case-preserving session keys for the same Matrix rooms. This is a present defect on the changed path that should be resolved before merging.

src/routing/session-key.ts — line 230 in buildGroupHistoryKey still calls .toLowerCase() on peerId.

This is a comment left during a code review.
Path: src/routing/session-key.ts
Line: 230

Comment:
**`buildGroupHistoryKey` still lowercases `peerId`**

`buildGroupHistoryKey` at line 230 still calls `.toLowerCase()` on `peerId`, applying the same case-mangling to Matrix room IDs that this PR fixes in `buildAgentPeerSessionKey`.

This creates an immediate inconsistency: after this fix, the session key for a Matrix group room like `!IEjZDNPucuFvKLrAQC:server` will use the original-case ID (correct), but any history key built for the same room via `buildGroupHistoryKey` will still be lowercased. Any code that joins or correlates session keys with history keys for Matrix rooms will therefore fail to match across the two.

```suggestion
  const peerId = params.peerId.trim() || "unknown";
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (1): Last reviewed commit: "fix(matrix): preserve case in group/chan..." | Re-trigger Greptile}

Thank you for the fix attempt here.

I am not merging this as-is.

Why:

• preserving Matrix room-id case in buildAgentPeerSessionKey and buildGroupHistoryKey is directionally right
• but the session-store stack still canonicalizes keys to lowercase on read/write (src/channels/session.ts, src/config/sessions/store.ts, and related callers)
• that means this PR would preserve mixed-case IDs in one builder while persistence and continuity paths still collapse them, which can split session identity instead of fixing it

So this needs a broader Matrix-safe session-key strategy, not just a local builder change.

Thank you for pushing on a real problem and for adding the continuity tests. The linked issue remains valid: #57321

Closing in favor of a more targeted approach. As @vincentkoc correctly noted, fixing case normalization in the session key builders without addressing the store/persistence layer would create split session identity.

New PR incoming with a narrower fix: treating the Matrix "User not in room" 403 as a permanent delivery error so delivery-recovery moves the poisoned entry to failed/ immediately instead of crash-looping the sync. This prevents the catastrophic failure while the broader case-normalization strategy is worked out separately.