Health survives a door, and experience needs you to be there

Arriving anywhere set health to maximum, so a run cost nothing: walk in,
take what you could, walk out, walk back in whole. Current health now
lives on the character record for the same reason the inventory does --
SimWorld builds a blank player on every instance change, so anything that
must survive a door has to be written down -- and it is banked at every
transfer, every disconnect, and on every item transaction, since a potion
moves an item and hit points in one action.

The hub is where that damage is paid off, at 10% of maximum per second:
about ten seconds from nothing, fast enough not to be a chore and slow
enough to be a decision before walking back in. The dungeon rate is
unchanged, so waiting one out is still not a plan. Regeneration is a
property of the world now rather than a constant.

adopt() no longer touches current health. It is called mid-session by
on_choose_upgrade, and reading health from the record there would snap a
player back to whatever was last written to disk; recompute_max_hp still
clamps downwards so Glass Cannon takes the hit points above the new
ceiling with it. ServerRuntime._adopt_character stays the one place a
record becomes a live player.

Experience is still undivided, but now only among players within
XP_AWARD_RADIUS of the kill -- ten percent past what a player can see, so
anyone who watched it die is inside and someone parked in the entrance
room is not. The death events carry a position for this, and deliberately
do not put it on the wire: encode_events still writes the id alone.

diag_progression covers the whole chain end to end -- wounded in a
dungeon, escaped to the hub with the wound intact, healing there, and
walking back in still hurt -- because a unit test cannot transfer a peer.
Both halves were mutation-tested against it; the unit suite alone missed
the arrival heal entirely.

The Proving Grounds is recorded in the roadmap as a debugging tool that
does not ship: it pays full experience for a boss with 8% health.

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

docs/DECISIONS.md

@@ -147,10 +147,19 @@ removed from the instance and left at the roster screen. The one exception is a
 linkdead player, which has nobody to show a roster to, so its body is left for
 the escape channel to resolve as before.
 
-**Experience is shared across the party, undivided.** Everyone alive in the
-instance receives the full amount for a kill. Splitting it would make bringing a
-friend cost you progress, which is the opposite of what the hub roster exists to
-encourage.
+**Experience is shared across the party, undivided — among everyone who was
+there.** Everyone alive receives the full amount for a kill. Splitting it would
+make bringing a friend cost you progress, which is the opposite of what the hub
+roster exists to encourage.
+
+Presence is a separate question from the split, and it has a radius:
+`SimConfig.XP_AWARD_RADIUS`, ten percent past `FOG_VIEW_RADIUS`. Anyone who
+watched something die is inside it; a player parked in the entrance room while
+the party clears the dungeon is not, and used to collect the whole run. Ten
+percent past sight rather than exactly on it, so the edge of the fog is
+comfortably inside and nobody loses a kill they actually saw. One consequence
+worth knowing: an upgraded shot outranges this several times over, so a kill
+made somewhere you cannot see pays nothing.
 
 **A level-up heals by the amount it added.** Gaining a level mid-fight should
 feel like relief, not like the bar you were watching got further from full.
@@ -168,12 +177,23 @@ than the one-second escape channel, and it would make that channel pointless.
 The menu greys the button out so the rule is visible, but the server refuses
 regardless of what any client's UI allows.
 
-**Health regenerates at 0.5% of MAXIMUM per second, with no out-of-combat
-gate.** A percentage rather than a flat rate, so it does not become irrelevant
-at level 15 — a capped character regains 1.2 hp/s against a level 1's 0.5, and
-both take about 200 seconds to heal from nothing. No combat gate because at this
-rate it cannot out-heal anything actually shooting at you, and a trickle that
-never stops is easier to reason about than a timer players have to learn.
+**Health regenerates at 0.5% of MAXIMUM per second in a dungeon, with no
+out-of-combat gate.** A percentage rather than a flat rate, so it does not become
+irrelevant at level 15 — a capped character regains 1.2 hp/s against a level 1's
+0.5. No combat gate because at this rate it cannot out-heal anything actually
+shooting at you, and a trickle that never stops is easier to reason about than a
+timer players have to learn.
+
+**The hub regenerates at 10% per second, and health is carried through a door.**
+Arriving anywhere used to set health to maximum, which meant a run cost nothing:
+walk in, take what you can, walk out, walk back in whole. Current health now
+lives on the character record — the same reason the inventory does, since
+`SimWorld` builds a blank player on every instance change — and the hub is where
+it is paid off, over about ten seconds. Fast enough that recovering is not a
+chore, slow enough that it is a decision to make before walking back in. The
+dungeon rate is unchanged, so waiting inside one is still not a plan.
+
+More friction is expected here later; this is the floor, not the design.
 
 **A dead character is gone, as far as the player is concerned.** Retirement is
 the server's own bookkeeping for archival and troubleshooting; the roster the

docs/ROADMAP.md

@@ -142,6 +142,15 @@ couple of minutes instead of a quarter of an hour, and because it is a portal
 rather than a launch flag you can compare it to a real run without restarting
 the server.
 
+**It is a debugging tool and does not ship.** It pays exactly the same
+experience a real run does — `Progression.xp_for_boss` ignores its argument and
+`xp_for_enemy` keys on the enemy id, which the difficulty multipliers do not
+touch — while its boss has 8% of its health and its trash drops ten times as
+often. That makes it strictly the best place to level and to farm, which is
+correct for a harness and would be ruinous in a release. Remove it from
+`Dungeons.ORDER` (and its `P` marker from the lobby stamp) before shipping, or
+give `DungeonDef` an `xp_mult` alongside the three multipliers it already has.
+
 Adding a dungeon is one entry in `Dungeons.ORDER` plus one more `P` marker in
 the lobby stamp — the Nth marker, in reading order, opens the Nth entry, so the
 two have to stay in the same order.