fix: read session/message lists from OpenAI-list data shape

[coolswood]

Summary

Fixes #18.

listSessions() and getMessages() in src/server/hermes-api.ts read resp.items, but the Hermes gateway (v0.18/0.20) returns the OpenAI-list shape:

GET /api/sessions?limit=50&offset=0
→ 200 {"object":"list","data":[{"id":"...","source":"api_server","message_count":2,...}]}

GET /api/sessions/{id}/messages
→ 200 {"object":"list","session_id":"...","data":[{"id":70,"role":"user",...}]}

So resp.items was undefined, the session history rendered empty on page reload, and message history never loaded — even though the data stayed intact in the gateway database. The same .items assumption in src/routes/api/context-usage.ts (~lines 95 and 161) zeroed out the context-usage estimate for sessions without cache_read_tokens.

This is the same class of bug as the closed issue #5 (closed without a fix landing in main).

Changes

Adds a small extractList() helper that returns the first array it finds across items | data | messages | results (and the payload itself when it is already an array), then uses it in listSessions() and getMessages(). context-usage.ts does the same resilient lookup inline in its two spots. This mirrors what fetchHermesModels in src/routes/api/models.ts already does (payload.data ?? payload.models) and stays compatible if the gateway ever changes the list key again.

• src/server/hermes-api.ts — extractList() helper + listSessions/getMessages use it
• src/routes/api/context-usage.ts — resilient list lookup (2 spots)

Note

getSession/createSession/updateSession read resp.session, and the gateway does return { session: {...} } for those single-resource endpoints — so only the list endpoints are affected. The single-object shape is correct and left untouched.

Verification

Against Hermes Agent v0.20.0 with a populated session DB:

Endpoint (via Studio proxy)	Before	After
GET /api/sessions	{ source: "gateway", sessions: [] } (0)	{ source: "gateway", sessions: [...] } (8)
Session message history	empty	loads
Context-usage indicator	stuck at 0%	reflects conversation size

• npx tsc --noEmit: no new errors (the 4 pre-existing errors on main are unrelated — the missing remark-math/rehype-katex deps and two untouched files)
• npx vitest run: 190/190 tests pass (including operations-aggregator.test, which mocks listSessions — the call signature is unchanged)
• prettier --check: passes on both changed files

Related: #19 (separate bug — proxy routes missing Authorization).

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