M3b plan: task 08 says not to join handler threads and to skip argv[0]

The first attempt at task 08 did both and stopped without a commit. Also asks
the implementer to debug inside the repository, since OpenCode refuses /tmp.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/plans/M3b/08-toolkit-egress-proxy.md

@@ -109,13 +109,22 @@ Use `try_clone` for the second handle of each stream. If a `try_clone` fails, re
 For each accepted stream: if the number of connections being handled is already
 `MAX_CONNECTIONS`, drop the stream at once (the client reads the end). Otherwise count it, handle
 it on its own thread (`std::thread::Builder`, not `spawn`, which panics; if the thread cannot be
-started, uncount it), and uncount it when `handle` returns. An `accept` error ends `serve` with
+started, uncount it), and uncount it **inside that thread** when `handle` returns. An `accept`
-that error. Use an `AtomicUsize` for the count.
+error ends `serve` with that error. Use an `AtomicUsize` for the count.
+
+**Never wait for (`join`) a handler thread in `serve`.** Start it, drop its `JoinHandle`, and go
+straight back to `accept`. Joining makes the proxy serve one connection at a time: the second
+client never gets its greeting, and `more_than_the_limit_of_connections_are_closed_at_once` fails
+with a read timeout (`WouldBlock`). (A first attempt at this task did exactly that.)
 
 ## `main.rs`
 
-Add one form before the tool form: the arguments (after the program name) are exactly
+Add one form before the tool form: the arguments **after the program name** are exactly
-`egress-proxy --socket <path> --allow <list>`, in that order, all UTF-8. Then:
+`egress-proxy --socket <path> --allow <list>`, in that order, all UTF-8. Take them with
+`std::env::args_os().skip(1)`: without `skip(1)`, the first element is the program's own path, the
+form never matches, and the proxy never listens (the given test then fails with "the proxy never
+listened", and standard error shows `toolkit: unknown tool ""`; a first attempt did exactly that).
+Then:
 
 1. `Allow::parse(list)`; an error `e` → print `toolkit: egress-proxy: --allow: {e}` to standard
    error, exit 2.
@@ -136,6 +145,13 @@ with some of the client's bytes unread makes the client's next read fail with "c
 rather than read the end; the tests treat both as closed. That is normal and needs nothing from
 you.
 
+## Debugging
+
+Work only inside the repository. Do not use `/tmp` or other directories outside it: OpenCode
+refuses them, and a refused command ends nothing but wastes the turn. To try the program by hand,
+put the socket under `target/`, for example
+`target/debug/toolkit egress-proxy --socket target/egress-try.sock --allow example.com`.
+
 ## Steps
 
 - [ ] **1. Copy.** `git switch m3b`, then

docs/plans/M3b/README.md

@@ -60,6 +60,11 @@ At the end: `make gate` prints `gate: ok` with about 638 tests.
   its `git add` line left the lock out, so the driver stopped on an unclean tree. The design model
   folded the lock into task 04's commit and added `Cargo.lock` to every task's `git add` (a no-op
   when it has not changed). The owner resumes from task 05.
+- 2026-09-23, task 08: the first attempt passed 13 of 15 tests and ended without a commit, after
+  OpenCode refused a command in `/tmp`. Its two defects: `main` did not skip the program name, so
+  `egress-proxy` never matched; and `serve` joined each handler thread, serving one connection at a
+  time. The attempt is saved in `.state/runs/M3b/08-first-attempt.diff`; the tree was reset, and the
+  task now says both things explicitly and to debug inside the repository. Resume from task 08.
 
 ## Running it