Merge branch 'fix/large-download-paths'

Concurrent-transfer limits, with the queue, the pause and the flag day.

A node now caps how many transfers it runs at once (8 downloads, 8 uploads,
node-wide) and how many one member may run in one group (2 by default,
operator-signed). Beyond that the node answers "queued" and the client waits its
turn, visibly, in the transfers panel — and a slot that frees starts whatever is
next, skipping past a member who is at their own cap rather than letting them
stall everyone behind them.

Browsing is never subject to a slot: not the poster grid, not the covers, not
opening a photo to look at it. That is structural — a transfer is what the
transfers widget shows — and the exemption is bounded rather than open, at two
files in flight per session, because an exemption with no bound is a leaseless
branch under another name.

Transfers can be cancelled, and now paused and resumed. A paused one holds
nothing: its slot goes back at once and resuming rejoins the queue at the tail.
Uploads survive the connection that started them and resume where the node
stopped, asked for inside the seal rather than on a clear message. What they
leave behind when they are abandoned is reaped, which closes a disk leak that
predates this work.

MNP 3.0 makes the lease compulsory and refuses 2.x at the handshake, with the
desktop client checking `client.minimum` before connecting so an un-updated one
says "update" instead of failing every connection in a protocol vocabulary.

Fourteen defects were found on the way, eight of them by a person clicking
Download and pasting a console — none of which 2075 tests could reach. Section
12 of ~/next/improve-downloads.md is that report, including the three this work
introduced itself and the one that turned out to be caused by an instruction to
hard-reload after each deployment.

Node suite 1209 passed, hub suite 866 passed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HCGdheDLxGReuKHga3BtST

1 files changed, 24 insertions, 2 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/api/webapp.py b/packages/meshbay-hub/src/meshbay_hub/api/webapp.py
index 3cfb208..96b93bb 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/webapp.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/webapp.py
@@ -111,8 +111,30 @@ CSP = "; ".join([
     "font-src 'self'",
     "connect-src 'self' https: wss:",
     "worker-src 'self'",
-    f"frame-src {_RECAPTCHA_SRC}",
-    "frame-ancestors 'none'",
+    # `'self'` is not decoration: the streamed-download path works by navigating
+    # a hidden iframe to `/_mbdl/<id>` so the service worker is asked for the
+    # response it is holding. Without it Chrome refuses the frame, the worker is
+    # never asked, and the page waits out its timeout for a download that cannot
+    # happen — on Firefox and Safari that is the *only* way to write a large
+    # file to disk, so the whole path was dead. Added when reCAPTCHA needed a
+    # frame, which is why nobody connected the two.
+    f"frame-src 'self' {_RECAPTCHA_SRC}",
+    # `'self'`, not `'none'`, and the difference is one same-origin iframe.
+    #
+    # The threat frame-ancestors answers is clickjacking: a *foreign* page
+    # framing this one and stealing clicks. `'self'` refuses every foreign
+    # origin exactly as `'none'` does — what it additionally allows is this
+    # origin framing itself, which is precisely how a streamed download works
+    # (a hidden iframe navigates to `/_mbdl/<id>` so the service worker is
+    # asked for the response it holds).
+    #
+    # Under `'none'` Firefox blocked that frame, the worker was never asked,
+    # and every large download waited out two 15-second timeouts and then fell
+    # through — on Firefox and Safari that is the only way to write a large
+    # file to disk. Chrome did not show it: its worker intercepts the
+    # navigation before the network response and its CSP are ever considered,
+    # which is why this looked like a Firefox-only problem for an afternoon.
+    "frame-ancestors 'self'",
     "base-uri 'none'",
     "form-action 'none'",
 ])