The memory bank and the story summary each kept a cursor: how many story
actions they had already covered. A count is a position in a list, and this
list moves — delete an action in front of the mark and every later one slides
down a slot, so the mark now covers one it has never read. All the cursor
bookkeeping existed to patch that up.
Both marks are now (branch_id, depth): the node up to and including which the
work is done. A depth is a coordinate along a path, not an offset into a list,
so nothing in front of it can move it. That deletes rather than rewrites
`position_of_index`, `note_action_removed`, `_rewind_cursors_to_index`,
`prune_dangling_memories` and the every-pass clamp in `run_post_turn`.
A memory hangs off the node its block ends on, so a fork inherits its
ancestors' memories without copying any, and retrieval selects through the
branch clause over the *whole* lineage — recall is long-range by definition and
cannot be windowed. Measured: 1,807 B on a story forked twenty times against
1,823 B on a flat one of the same length.
Migrations 53-56 translate the old counts into nodes. They rewrite `adventures`
and not `actions`, so this one needs no VACUUM FULL.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
Phase 14 SP1. The tree goes into the schema and nothing reads it yet: a
`branches` table, `branch_id`/`depth` on actions and memories, a head pointer
on adventures, migrations 46-52, and a server-side backfill that re-reads every
existing adventure as a tree with one branch. `depth` holds the number `index`
already held, gaps included, so no story changes — a linear story *is* a tree
with one branch, which is what makes the SP0 baseline passing unmodified the
pass condition rather than a hope.
The writer had to come with it. No migration will ever visit a row written
after it ran, so columns backfilled today and populated next subphase would
leave a hole exactly the width of one deploy, and from SP2 on a row without a
branch is a row no read can see. `app/tree.py` owns that: one module, because a
node written without a branch fails by disappearing rather than by raising.
Three things the schema itself insisted on:
- `adventures.head_branch_id` is a plain integer, not a foreign key. Pointing
both ways makes the two tables a cycle create_all cannot order, and its
escape hatch needs an ALTER SQLite does not have. It is a cache, and a head
naming a branch that is gone recovers onto the root.
- `lineage` is NOT NULL, so the backfill inserts `'[]'` and fills it in a
second pass guarded on `json_array_length(lineage) = 0` — not `= '[]'`,
because Postgres `json` has no equality operator.
- SQLite will not drop a column a foreign key names, which is how two existing
tests broke: they simulated an old database by rewinding the stamp while
leaving the new columns in place. Every ADD COLUMN migration is now
idempotent, and `tests/test_tree_migration.py` builds a genuine schema 45 by
rebuilding three tables from frozen DDL so the real ALTERs run.
297 tests green, 14 of them new. `branches` costs 0.1 kB of a 733.5 kB turn;
page load and index are byte-identical to the recorded figures.
The deploy that ships this needs one `VACUUM FULL actions;` on the direct
endpoint afterwards — it rewrites every row.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
The stress fixture is sized from production and exists to weigh bytes, so it
leaves every column it does not weigh at its default. Checked against a freshly
built one, that is exactly the set phase 14 has to migrate: state_before and
world_state_before NULL on all 600 rows, no scenario and so no RPG layer, no
adventure scripts, both cursors 0, and a hundred retry histories whose two
attempts carry byte-identical text with variant_index pinned at 0.
That last one matters most. "Which attempt is live?" is the question SP4's
migration answers when it decides which sibling node becomes the head of a
turn, and against that fixture the question had no observable answer -- a
migration that picked wrong would have looked correct.
--rich fills in those columns and no others. A real RPG scenario read from the
seed data rather than invented, with a world state played forward so hp
declines and flags flip; monotonic per-action state snapshots, so a rollback
that does not happen reads as a wrong number instead of as nothing; a gold
script, story cards, non-zero cursors, pinned and forgotten memories; retry
attempts with distinct texts, counts of two and three, and a live attempt that
is often not the last written. Plus a second adventure, because a branch clause
that forgot its adventure still looks right on a database holding one.
The invariant SP4 reads -- text mirrors variants[variant_index] -- is asserted
at build time rather than assumed.
The plain fixture is untouched and re-measured unchanged at 1.8 kB, so the
egress ceilings stay comparable. All six shapes run clean on --rich, including
the turn path with the RPG layer and script pipeline now live. 283 tests pass.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
The harness already built a production-shaped 600-action adventure and then
threw it away with the temp file. The one open gap in plan/13 is that nothing
has ever driven the scroll in a browser, and part of why is that there was
never a long adventure to drive it with.
--keep PATH writes the fixture somewhere durable and makes the app able to
serve it. Two edits are needed for that, both of which cost an hour to
rediscover:
- create_all() builds the current schema but leaves the version stamp at its
default, and bootstrap() reads a populated-but-unstamped database as
ancient — it replays every migration against a schema that already has the
columns, and fails on the first.
- the fixture's user is a registered one, but local mode looks for the row
with email IS NULL and is_guest false, so without clearing the email the
app opens on an empty library.
--keep is read before argparse exists, because where the database lives has to
be settled before app.database is imported. That is the same constraint the
AIDND_STRESS_DATABASE_URL block already lives under. SQLite only; combining it
with a Postgres target is rejected rather than half-honoured.
Verified end to end: the fixture boots with no manual step, action_count 600,
a 60-action first payload, and before_id walks back nine more pages to the
start. Nothing about the default path changed; 259 tests pass.
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
One column is 89% of the database and the free tier allows 512 MB. Reads were
already solved -- the column is deferred, so a page load never touches it and
one screen fetches one row at a time -- but nothing had costed storage, and
storage is the constraint with a cliff: 99.6 MB used, ~94 kB of disk per
action, so the ceiling arrives around 5,400 actions and 944 are stored.
Postgres already compresses it and only gets 1.7x. pglz is tuned for fast
decompression of data a query might filter on, and nothing has ever filtered
on an assembled prompt -- it is written once and read whole, rarely, by the
Insights viewer. zlib gets 3.5x on the same text for a decompress on a request
that already made an LLM call.
Done as a TypeDecorator rather than a second column, so every call site still
writes a dict and reads a dict back, and deferred/undefer/load_only keep
naming the same attribute. Only the storage format moves.
Migrations 43-45: add the bytea, convert into it, drop the original, rename.
The backfill is the one destructive step in the file -- 44 removes the only
other copy -- so it decompresses every row and compares it against what went
in, and a row that fails aborts the run. The whole loop is one transaction, so
an abort rolls the DROP back and the prompts are still there.
Verified on real Postgres, replaying 43-45 from a pre-43 schema on a throwaway
Neon database: 720,864 B of JSON became 204,293 B of bytea, 3.53x, the column
came out named context_snapshot, every snapshot compared equal and the one
NULL stayed NULL.
Postgres does not return the disk by itself: DROP COLUMN only marks the column
gone and the backfill leaves a dead tuple per row, so the table peaks near
twice its size before settling. The deploy needs one VACUUM FULL to collect
it; the migration comment says so.
The egress fixture's snapshots are prose now rather than "x" * 20_000, and the
prose generator moved to tools/fakeprose.py so the harness and the tests share
one definition. A repeated character compresses a thousandfold: against the
old fixture a compressed column looked free and the byte ceilings would have
been guarding nothing.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
The old fixture was wrong in both directions at once and happened to land near
the right total. Actions were modelled at ~2.1 KB against a real 886 B of
text, and adventures at 200 actions against a real 607. Width flattered,
length did not, and length is what a page load pays for.
Re-sized from the 2026-08-17 measurements: 600 actions, 1700 B of narration
alternating with a one-line player input, 232 KB of context_snapshot a row.
The page-load shape now reports 606.0 kB against the 589.5 kB measured on
production's longest adventure -- 2.8% out, where the old defaults were 28%
out on a story a third of the length.
Filler text is now generated word by word instead of one sentence repeated.
That matters for what comes next: the repeated string compresses 313x and the
generated prose 3.7x, so any compression ratio measured against the old
fixture would have been fiction, and shrinking context_snapshot is the open
question it exists to answer.
context_snapshot also gains a flag of its own rather than being hardcoded, and
the 74 KB figure in the comment -- inherited from models.py -- is corrected:
the real column averages 163 KB a row across the table.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
Everything measured so far ran on SQLite against a synthetic fixture, so two
claims were still on trust: that migration 38 spells BYTEA correctly for a real
server, and that the byte figures survive psycopg's encodings.
Both hold. Production reads schema_version 41 with embedding_blob bytea and
embedded boolean present, the backfill is complete at 134/134, and the packed
vectors are 5.04x smaller than the JSON on real data -- 30,971 to 6,144 bytes a
memory, as predicted. stress_session now takes AIDND_STRESS_DATABASE_URL, and
against a throwaway Neon database every shape lands within 0.5% of the SQLite
run: the warm turn is 121.1 kB against 122.3, with memories down to 1.7 kB of
it.
The harness writes, so it refuses any target whose name does not say stress or
scratch -- pointed at the production database it stops rather than seeding it
with a fake user and 200 fake turns. It also empties a Postgres target before
building, which a fresh SQLite temp file never needed.
Two corrections fall out, both recorded in plan/13. The page-load model has the
wrong shape: real actions are half the fixture's weight but real stories run to
607 actions, not 200, so the worst real page load is 589.5 kB. And the decision
to leave context_snapshot in the database costed egress but never storage --
it is 88.9 MB of a 99.6 MB database against a 512 MB free tier, which is the
ceiling this deploy will hit first.
Measured with counts and octet_length sums only. No user content was read.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Dvvqn9ZDR4ixeFPHNbww7
Retrieval walked adventure.memories, so every turn loaded every row of the
bank with its vector attached -- 3.1 MB, 96% of everything a turn read. It
now asks SQL which memories are in play (an id and a flag per row), ranks
against vectors held in process, and fetches text only for the five it picks.
Two more callers were doing the same thing and the production SQL could not
see them: _evict_over_capacity walked the bank to count it, and _embed_pending
walked it to find the rows with no vector. Both are counts and filters the
database can do without sending anything back.
one turn 3,258.7 kB -> 723.4 kB cold, 122.3 kB warm
run_post_turn 3,139.1 kB -> 0.7 kB
Insights 3,223.7 kB -> 117.9 kB
Memories drawer ~3.1 MB -> 23.6 kB
A played turn is turn plus post-turn work: 6.4 MB down to 123 kB.
The cache needs no invalidation callbacks, which is what makes it safe. A
vector can only change through set_vector, which drops that one entry;
anything that removes a memory from play leaves the catalogue query, and
entries missing from the catalogue are dropped on the next read. So eviction,
deletion and pruning have nothing to remember to call.
memories.embedded joins the blob, for the same reason actions.variant_count
sits beside actions.variants: with the vector deferred, every "is this
embedded?" check would otherwise be a 6 KB lazy load, once per row.
Capacity drops 200 -> 80, on retrieval quality as much as cost -- ranking two
hundred memories to pick five buries the five. Eviction was measured at scale
first: trimming 100 to 80 costs 0.8 kB and reads no vectors.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CYEJKobJ2Re4Dv7qUoSA7
A 1536-dimension vector spelled out as JSON decimals is ~31 KB. The same
numbers packed as float32 are 6,144 bytes, and the whole bank is read on
every turn, so those bytes are paid over and over.
It is a format change, not a precision trade: the endpoints compute in
float32 and render that into JSON, so converting back recovers the original
bits exactly. Nothing is re-embedded and no API call is made -- migration 38
is a pure repack of what is already stored.
Unlike migrations 36 and 37 this backfill cannot be expressed in portable
SQL, so it comes through Python, batched, and pays a one-time read of every
vector to stop paying three megabytes a turn.
The JSON column stays, still written through set_vector, so a rollback finds
the vectors intact. Reading from the blob comes next; a follow-up migration
drops the old column once that is verified.
Migration SQL can now be a {dialect: sql} map -- BLOB and BYTEA have no
common spelling, and every Postgres deploy replays this one.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CYEJKobJ2Re4Dv7qUoSA7
Both egress blowouts this project has had were one query fetching a column
nobody read, and a statement count would have shown nothing wrong in either.
So the meter counts bytes, at the DBAPI cursor -- everything that crosses
that line crossed the wire.
tools/stress_session.py drives a production-shaped adventure through the real
routes with only the network faked. It reproduces both figures measured
directly on production: 426.7 kB for a 200-action page load against 423 KB,
and 3,258.7 kB for one turn against 3,153 kB.
The memory bank is on by default, which is the whole point -- the previous
harness ran without an embedding model, so retrieval returned early and the
heaviest read in a turn never happened. --no-embeddings reproduces that
deliberately, and the gap is 29x.
It also turned up two callers the production SQL could not see: run_post_turn
walks the whole bank again every turn, and Insights pays for it a third time.
A played turn costs ~6.4 MB, not 3.2.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CYEJKobJ2Re4Dv7qUoSA7
