feat: pin the agent to a chosen browser profile (#16)

* feat: pin the agent to a chosen browser profile (#15)

Harness tabs were created with a bare Target.createTarget, which places
them in Chrome's defaultBrowserContextId — and that value follows window
focus. Which profile the agent acted as therefore depended on which
browser window the user last clicked, so the same task could run as a
work account on one run and a personal account on the next.

/browser-profile lists the connected browser's profiles as "Name (email)"
and pins one to ~/.pi/agent/browser-harness.json, so the choice outlives
the session. The same picker appears on first browser_setup when nothing
is pinned; with no interactive UI, or on cancel, setup continues with a
note and the previous behavior.

Chrome offers no direct route to another profile: Target.createTarget
rejects a foreign browserContextId, and openerId does not inherit the
opener's context. The window is opened through the browser's own command
line (--profile-directory, handed to the running browser by Chromium's
ProcessSingleton) and identified by a unique file:// sentinel page, since
a bare about:blank#token argument is discarded. Further tabs come from
window.open evaluated with userGesture: true — the only CDP-reachable way
to place a tab in a non-default browser context — correlated by a unique
token so concurrent isolated tabs stay distinct. A failed handshake is
reported, never silently redirected to another profile.

All four tab-creation sites now funnel through cdp/target-factory, so
open_urls and the isolated tabs behind web_search / read_page cannot run
with a different profile's cookies than the visible tabs.

Also fixed along the way: snap Chromium is discovered, Windows uses
%LOCALAPPDATA%, browsers launched with an explicit --user-data-dir are
found, the running browser is chosen by ranking candidates against the
connected user-data-dir rather than taking the first process found, and
an installed-but-closed browser no longer reads as running.

CI runs the profile suites and a real-browser end-to-end test on ubuntu,
macOS, and Windows — profile discovery is the one part of the harness
whose behavior genuinely differs per OS.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: single-flight harness window creation

Isolated tabs run concurrently (browser_read_page is registered
unserialized), so several could each find "no harness window" and create
one — two blank windows before this feature, two LAUNCHED profile windows
after it. ensureHarnessWindow now shares one in-flight creation per
client.

Sharing introduces a second hazard: freshlyCreated is a claim on the seed
tab, and if every waiter received it, they would all drive the same tab.
Only the caller that started the creation keeps the claim; the rest open
their own tab beside it.

Covered by test/manual/profile-concurrency-test.ts (five concurrent
isolated tabs, pinned and unpinned: distinct targets, one window, correct
profile), wired into CI on Linux only — the coordination is pure JS and
identical across platforms.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix: tilde expansion differs by purpose on Windows

CI on windows-latest caught this: join("~", "x") yields "~\x" there, and
expandTilde only handled "~/".

The two uses are not the same, so they no longer share a helper. The
agent dir stays byte-compatible with pi's own expandTildePath ("~/" only,
every platform) — being more lenient would put the pin file somewhere pi
never looks. $CHROME_USER_DATA_DIR is ours to interpret, so it accepts
"~\" as well, which is what a Windows user would type.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/skills/pi-browser-harness/SKILL.md b/skills/pi-browser-harness/SKILL.md
index 60e23e0..fa76a2e 100644
--- a/skills/pi-browser-harness/SKILL.md
+++ b/skills/pi-browser-harness/SKILL.md
@@ -54,6 +54,21 @@ connects to Chrome, and opens a test tab. The user sees a single "Allow Remote
 Debugging" prompt the first time. After that, all sessions reuse the same connection.
 `browser_setup` is idempotent — safe to call even when already connected.
 
+## Browser profile
+
+Every harness tab opens in one chosen browser profile, which determines the logins,
+cookies, and extensions you're working with. The user picks it once via
+`/browser-profile`; the choice persists across sessions in `~/.pi/agent/`.
+
+The first `browser_setup` in a fresh install shows that picker, so the tool may pause
+briefly on user input — this is expected, and the result appears in the tool output as
+`Browser profile: <name> (<email>)`.
+
+If setup reports `couldn't open a window in "…" automatically`, the harness could not
+open the pinned profile's window. Tell the user to open that profile from their browser's
+profile menu and retry, or to run `/browser-profile` to choose another. Never work around
+it by opening tabs elsewhere — a different profile means different accounts.
+
 ## Connection
 
 You're attached to the user's real Chrome — never launch your own. If auth is required, stop and ask the user. If `browser_page_info` returns a dialog, handle it first with `browser_handle_dialog`.