fix(assistant): stop cross-user conversation access, bricked threads and lost sessions (#1209)

* fix(assistant): stop cross-user conversation access, bricked threads and lost sessions

Hotfix batch (PR1 of the assistant UI makeover, dev_docs/assistant_redesign_plan.md
section 7). No visual change; each of these is wrong today regardless of which
design lands, and three are unrecoverable per incident.

/api/agent/invoke never checked who owns a resumed conversation_id. RLS on
agent_conversations/agent_messages is company-scoped, not user-scoped
(20260517204000), so a member could post a colleague's conversation id, have
their history loaded into the prompt and read it back, while their own turns
were appended to that thread. The conversations list route filters on user_id
for exactly this reason. Also pins company and intent: resuming a thread from
another company would mix ledgers, and resuming under a different intent would
swap the tool whitelist under history the model has already seen.

A turn persists the assistant message carrying tool_use blocks before the tools
run, and their results only after the batch finishes. Dying in between (client
disconnect terminating the function, a deploy, a slow tool) left history ending
on an unanswered tool_use, which the Messages API rejects on replay: every later
turn 400s, and agent_messages is append-only for the BFL trail, so nothing could
repair it. History is now patched on read by synthesizing is_error tool_results,
leaving the stored trail untouched.

check_and_increment_agent_quota is SECURITY DEFINER in public with a
caller-chosen p_user_id, so any authenticated user could drain a colleague's
minute/day budget and lock them out of every agent endpoint. A plain REVOKE
would break the limiter (all three callers use the user's RLS client) and, as it
fails open, silently remove the spend cap: the function now refuses to act for
anyone but the caller, while service-role connections keep passing an explicit
id.

The single reject route re-read status and then wrote unguarded, so losing the
race with commit's atomic pending -> committing claim stamped `rejected` over an
operation that had already posted a verifikat, invisible to the committing-state
recovery sweep. Guarded on status like bulk-reject already is; a lost race is
now a 409.

The sheet's Escape handler listened on window with no defaultPrevented or target
check while the sheet is deliberately non-modal, so pressing Esc to dismiss the
reject-reason Select inside an approval card, the command palette or any dialog
unmounted the sheet and discarded the conversation, the streaming turn and the
un-actioned proposal. It now yields to open overlays and to focus outside the
sheet.

Verified: 9526 unit tests pass, lint clean on touched files, guards pass, and
the new pg-real test proves the quota guard against real Postgres (attacker
raises 42501, victim counters stay at 0). The four unrelated pg-real failures on
this machine reproduce identically with these changes stashed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* fix(assistant): close anon path on the quota RPC, order the ownership check ahead of writes

Review follow-ups on the hotfix batch.

The caller guard used auth.uid() alone, which is NULL for the `anon` role just
as it is for backend roles, so an unauthenticated caller holding the public anon
key (it ships in the browser bundle) could still pick any p_user_id and drain
that user's quota. The guard now keys on the request role: anon and
authenticated may only ever spend their own quota, backend roles keep passing an
explicit id. The default PUBLIC execute grant is revoked as a second layer, with
execute granted only to authenticated and service_role. Covered by a new pg test
for the anon path.

The ownership check ran after the onboarding.intake stamp, so a request that was
about to be rejected could still write intake_completed_at. It now sits directly
after the capability gate, ahead of every side effect and ahead of the company
and profile reads, which also makes a rejected request cheaper.

The tool-result repair matched ids anywhere in the history, but the API needs
results in the message IMMEDIATELY after the tool_use. A result persisted after
an intervening turn (two turns racing on one conversation) left a shape that
still 400s. The repair is now positional, and orphaned or late-duplicate
tool_results are dropped, since an unmatched tool_result is rejected just as an
unanswered tool_use is.

The Escape guard matched the Radix popper wrapper, which stays mounted when a
popper is force-mounted; it now requires data-state="open" so a closed popper
cannot block Escape for the rest of the session.

Both new route errors are Swedish, per the user-facing error rule.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

app/api/agent/invoke/route.ts

@@ -117,6 +117,43 @@ export async function POST(request: Request) {
   const capBlocked = await requireCapability(supabase, companyId, CAPABILITY.ai)
   if (capBlocked) return capBlocked
 
+  // Resolve the conversation BEFORE any side effect below (the onboarding
+  // intake stamp): a request that is about to be rejected must not write.
+  let conversationId = body.conversation_id ?? null
+  if (conversationId) {
+    // A resumed conversation id comes straight from the client, so ownership
+    // has to be proven here. RLS on agent_conversations/agent_messages is
+    // COMPANY-scoped (migration 20260517204000), not user-scoped, so RLS alone
+    // would happily load a colleague's thread into the prompt and append this
+    // user's turns to it. The conversations list route filters on user_id for
+    // exactly this reason; the same rule applies to the turn itself.
+    //
+    // The company check matters too: a user who belongs to several companies
+    // must not resume a thread from company B while the turn runs with company
+    // A's ledger, tools and staged operations.
+    const { data: conv } = await supabase
+      .from('agent_conversations')
+      .select('id, user_id, company_id, intent_id')
+      .eq('id', conversationId)
+      .maybeSingle()
+
+    if (!conv || conv.user_id !== user.id || conv.company_id !== companyId) {
+      // Same response for "doesn't exist" and "isn't yours": a 403 here would
+      // confirm that someone else's conversation id is real.
+      return NextResponse.json({ error: 'Konversationen hittades inte.' }, { status: 404 })
+    }
+
+    // The intent decides the tool loadout and the system prompt. Letting a
+    // resumed thread switch intent mid-conversation would swap the tool
+    // whitelist under history the model has already been shown.
+    if (conv.intent_id !== body.intent_id) {
+      return NextResponse.json(
+        { error: 'Konversationen hör till ett annat sammanhang.' },
+        { status: 400 },
+      )
+    }
+  }
+
   // onboarding.intake completion signal: once the user has actually
   // engaged (typed a real reply, not the auto-fired greeting prompt that
   // mounts the chat), stamp intake_completed_at on the profile so re-entry
@@ -149,8 +186,7 @@ export async function POST(request: Request) {
   const companyName = company?.name ?? ''
   const firstName = profile?.full_name?.split(' ')[0] ?? null
 
-  // Resolve / create the conversation row.
-  let conversationId = body.conversation_id ?? null
+  // Create the conversation row when this is a fresh thread.
   if (!conversationId) {
     const { data: newConv, error: convErr } = await supabase
       .from('agent_conversations')