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Rewrite docs and READMEs in Google developer documentation style

Browse Source 
Trim em dashes, convert first-person plural to second person, and
tighten sentences in README.md, docs/GUIDE.md, docs/self-review.md,
and frontend/README.md, matching the style already applied to code
comments. No technical content, numbers, or code blocks changed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N7vUFpYkLrJnuSgwcRjqSx
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parththakkar106
2026-08-26 16:07:34 +05:30
committed by Parth
co-authored by Claude Sonnet 5
parent e7d75c3b05
commit 446ceb6cab
4 changed files with 331 additions and 325 deletions
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@@ -108,19 +108,19 @@ player input
Two design choices are visible in that list before any of the details.
**The prompt is snapshotted, not reconstructed.** Every AI action stores the exact text
that was sent to the model. That's what powers the Insights panel — open any turn and see
that was sent to the model. That's what powers the Insights panel: open any turn and see
each context component, its token cost, and why it was included. It's also what makes
prompt bugs findable. The cost is storage (~74 KB per turn), which turns into a real
performance problem later — see [2.5](#25-the-189x-egress-fix).
performance problem later. See [2.5](#25-the-189x-egress-fix).
**Every node records the state it leaves behind.** `state_after` and `world_state_after`
are stapled onto the action once its hooks and its delta have run, so a node carries the
scoreboard and the RPG stats as they stood when that turn finished. Rewinding to *before*
a turn is then a read of the node in front of it, which is the same move as switching to
another branch — one mechanism, and it is the whole reason undo, retry and branch
switching all put the numbers back rather than only rewriting text. (These were `*_before`
pictures originally; a tree wants the *after*, because a branch's tip is what a reader
standing on it should see.)
are attached to the action once its hooks and its delta have run, so a node carries the
stats and the RPG values as they stood when that turn finished. Rewinding to *before*
a turn is then a read of the node in front of it, which is the same operation as switching
to another branch: one mechanism, and the reason undo, retry, and branch switching all put
the numbers back instead of only rewriting text. (These were `*_before` fields originally; a
tree needs the *after* value, because a branch's tip is what a reader standing on it should
see.)
---
@@ -138,7 +138,7 @@ whether the story stays coherent.
Send the last N turns. That breaks in two directions: N turns of short exchanges wastes the
window, and N turns of long ones overflows it. It also throws away the things that matter
most — the premise, the character sheet, the fact that you promised the innkeeper you'd
most: the premise, the character sheet, the fact that you promised the innkeeper you'd
return.
### What this app does
@@ -149,12 +149,12 @@ Fixed (always included, whatever they cost):
| Section | What it is |
|---|---|
| `narrator` | The system prompt — how to write. |
| `narrator` | The system prompt: how to write. |
| `world_state_guide` | The stat legend: what each stat means, its range, its bands. |
| `world_state` | Current values of every stat, plus NPCs in scene. |
| `world_state_rule` | How to report changes. |
| `ai_instructions` | Per-adventure steering. |
| `plot_essentials` | AI Dungeon's "Memory" — the premise. |
| `plot_essentials` | AI Dungeon's "Memory": the premise. |
| `story_summary` | The auto-maintained running summary. |
| `used_memories` | Top-K retrievals from the memory bank. |
@@ -184,7 +184,7 @@ of "the model has no idea what just happened". Cards that don't fit are still *r
to Insights with `included: false`, so the UI can show the lore that got squeezed out.
**History fills newest-first and stops.** Oldest turns fall out. This is the right
direction because the old material is not actually lost — it has been summarized into
direction because the old material is not actually lost: it has been summarized into
memories and the running summary, which are in the fixed section.
**If even the single newest turn is over budget, it gets hard-truncated** rather than
@@ -193,8 +193,8 @@ of the last turn produces something.
**The author's note is injected 3 actions from the end**, not at the top.
`AUTHORS_NOTE_DEPTH = 3`. Instructions placed near the end of a prompt have more influence
on what comes next than instructions at the top — recency. The author's note is a steering
control ("keep it tense"), so it goes where steering works.
on what comes next than instructions at the top, because of recency. The author's note is a
steering control ("keep it tense"), so it goes where steering works.
**The world-state reminder goes dead last.** The full emit rule lives up in the system
block, hundreds of tokens away from where the model starts writing. A one-line reminder
@@ -203,15 +203,15 @@ forgotten.
**Past AI turns get their state block re-attached.** The state block is stripped from the
text before it's stored, so a replayed history would show the model twenty of its own past
turns that *contain no state block* — which teaches it, by imitation, to stop emitting one.
turns that *contain no state block*. That teaches it, by imitation, to stop emitting one.
So `_history_text()` reconstructs the block from the stored delta and re-appends it when
building history. The model sees its own pattern and keeps following it.
### The performance trap hiding in this
Building the context needs the newest ~6,000 tokens of story. The obvious implementation
reads `adventure.actions` — which loads every row of the adventure — and then throws 90%
of it away. At turn 200 that was 839 KB of database reads to use maybe 70 KB, and it grew
reads `adventure.actions`, which loads every row of the adventure, and then throws 90% of
it away. At turn 200 that was 839 KB of database reads to use maybe 70 KB, and it grew
every single turn.
`backend/app/context/history.py` fixes it by serving three shapes directly from SQL: a
@@ -225,13 +225,13 @@ projected = int(budget / average * 1.15) + 8
```
Each round fetches only what it doesn't already hold, so no row is read twice. Result: the
same turn costs 129 KB instead of 839 KB, and stops growing at around turn 50 — the cost
is bounded by the context budget instead of by the length of the story.
same turn costs 129 KB instead of 839 KB, and stops growing at around turn 50. The cost is
bounded by the context budget instead of by the length of the story.
There's a second rule in that module worth naming: **if the actions are already loaded in
memory, slice them instead of querying.** The scripting pipeline hands the whole history to
user scripts (AI Dungeon's API requires it), so on a scripted adventure the rows are
already there — issuing a query beside them would mean paying twice.
user scripts (AI Dungeon's API requires it), so on a scripted adventure the rows are already
there. Issuing a query beside them would mean paying twice.
---
@@ -241,19 +241,19 @@ Source: `backend/app/worldstate/engine.py`, `plan/12-phase-rpg-world-state.md`.
### The problem
You want an RPG layer — hit points, trust, quest progress. Who owns the numbers?
You want an RPG layer: hit points, trust, quest progress. Who owns the numbers?
### Three options, and why two lose
**Option A: a deterministic dice engine.** The player types "attack the goblin", the
engine rolls, applies damage, and the model narrates the result. This is what a real RPG
does. It loses here because the action space is unbounded — the player can type anything,
and mapping arbitrary natural language onto a fixed rules system is a harder problem than
the one being solved.
does. It loses here because the action space is unbounded: the player can type anything, and
mapping arbitrary natural language onto a fixed rules system is a harder problem than the
one being solved.
**Option B: the model owns the numbers.** Let it track hp in the prose and trust it. This
fails immediately. Models are bad at arithmetic, worse at remembering a number across
twenty turns, and completely unable to obey their own frequency rules — tell one "only
twenty turns, and completely unable to obey their own frequency rules. Tell one "only
change this every 5 turns" and it will change it every turn.
**Option C, chosen: the model proposes, the engine disposes.** The model narrates and
@@ -279,10 +279,10 @@ The engine then applies, in order:
| `max_delta_per_turn` | Losing 90 hp to a stubbed toe |
| Clamp to `min`/`max` | Negative hp, trust above 100 |
| Milestones are sticky, `true` only | Un-completing a quest |
| Flags are two-way booleans | (Deliberately unrestricted — that's what flags are for) |
| Flags are two-way booleans | (Deliberately unrestricted: that's what flags are for) |
Everything it rejects is *reported*, not silently swallowed — the Insights panel shows
applied, clamped and rejected paths per turn, and the chip under each narration shows what
Everything it rejects is *reported*, not silently swallowed. The Insights panel shows
applied, clamped, and rejected paths per turn, and the chip under each narration shows what
actually changed.
### The reliability mechanism: word bands
@@ -295,33 +295,33 @@ A stat can carry **bands**:
[60,90,"healthy"],[90,100,"full health"]] }
```
Two things use them. The live state block shows the current band label — `hp 55/100 (minor
damage)` — so the model reads a *word*, not just a number. And the stat guide shows the
Two things use them. The live state block shows the current band label, `hp 55/100 (minor
damage)`, so the model reads a *word*, not just a number. And the stat guide shows the
whole ladder once per turn, so the model can see the full scale it's reasoning across.
The point: models reason well over semantics and badly over arithmetic. "He's badly hurt,
so a solid hit should take him to very weak" is a judgement a model can make. "55 minus 22
is 33" is one it will get wrong often enough to matter.
so a solid hit should take him to very weak" is a judgment a model can make. "55 minus 22 is
33" is one it will get wrong often enough to matter.
### The failure philosophy
Nothing in the world-state engine raises. A malformed delta returns `{}` and the turn
continues. The parser is deliberately tolerant — it strips trailing commas and leading `+`
continues. The parser is deliberately tolerant: it strips trailing commas and leading `+`
signs on numbers, both of which weaker free models emit and strict JSON rejects. It accepts
a fence labelled `state`, one labelled `json`, or an unlabelled one, and falls back to a
bare JSON object hugging the end of the text — but only if it parses into something that
looks like a delta, so prose ending in `}` is never eaten.
a fence labeled `state`, one labeled `json`, or an unlabeled one, and falls back to a bare
JSON object at the end of the text, but only if it parses into something that looks like a
delta, so prose ending in `}` is never eaten.
This matters because the hosted demo runs on free-tier models. A stricter parser would mean
a good model works and a free one doesn't.
### One call, not two
The model narrates *and* emits the delta in a single request. The alternative — narrate,
then a second call to extract structured state — is more reliable per call and costs twice
the latency and twice the rate-limit budget. On the free tier (20 requests/minute) that
would halve the playable turn rate. The tolerant parser plus the terminal reminder was the
cheaper way to buy the same reliability.
The model narrates *and* emits the delta in a single request. The alternative, narrating and
then making a second call to extract structured state, is more reliable per call and costs
twice the latency and twice the rate-limit budget. On the free tier (20 requests/minute)
that would halve the playable turn rate. The tolerant parser plus the terminal reminder was
the cheaper way to buy the same reliability.
---
@@ -339,9 +339,9 @@ Tell the model its budget: *"keep this turn under about N words"*.
### What the measurement showed
Average turn length went from **174 words to 246** — every run longer than every unhinted
run (n=5). Phrased as a budget, the number reads as a *target to fill*. The hint pushed
turns toward the very wall it existed to protect.
Average turn length went from **174 words to 246**, and every run was longer than every
unhinted run (n=5). Phrased as a budget, the number reads as a *target to fill*. The hint
pushed turns toward the very wall it existed to protect.
### The fix
@@ -361,12 +361,12 @@ Average came back to 170 words, and the state block survived at tight caps.
words = int((max_output_tokens - 50) * 0.75 * 0.90)
```
- `- 50` (`LENGTH_HEADROOM`) — tokens held back for the state block itself.
- `* 0.75` (`WORDS_PER_TOKEN`) — models can't count their own tokens, but they do follow a
- `- 50` (`LENGTH_HEADROOM`): tokens held back for the state block itself.
- `* 0.75` (`WORDS_PER_TOKEN`): models can't count their own tokens, but they do follow a
word budget. English prose is roughly 0.75 words per token.
- `* 0.90` (`LENGTH_BUFFER`) — a word budget is a suggestion the model overshoots; the cap
- `* 0.90` (`LENGTH_BUFFER`): a word budget is a suggestion the model overshoots, and the cap
it protects is a hard wall. Aim 10% short so the overshoot lands in slack.
- Below 40 words the hint is dropped entirely — it stops earning its tokens.
- Below 40 words the hint is dropped entirely: it stops earning its tokens.
---
@@ -377,7 +377,7 @@ Source: `backend/app/memorybank.py`.
### The problem
Story history falls out of the context window as the adventure grows. Turn 4 said you
promised the innkeeper you'd return. At turn 90 that's long gone from the prompt — but if
promised the innkeeper you'd return. At turn 90 that's long gone from the prompt, but if
you walk back into the inn, it should come back.
### The three layers
@@ -401,23 +401,23 @@ back into the prompt.
### The decisions inside it
**A memory hangs off the node whose block it ends on.** Not off the adventure, and not off
a *position* in a list of actions — off a `(branch_id, depth)` coordinate. That is what
**A memory attaches to the node whose block it ends on.** Not to the adventure, and not to
a *position* in a list of actions, but to a `(branch_id, depth)` coordinate. That is what
makes "which memories described this turn?" an indexed lookup rather than a scan for rows
whose covered range has fallen off the end of the story, and it is what makes memories
inherit correctly across a fork: the ones above the fork point already sit on ancestors
both lines read.
It is also the repair. When a turn's text is replaced or removed — a retry, an undo, a
deleted action — `forget_node` withdraws the memory hanging off that coordinate *and*
This is also how repair works. When a turn's text is replaced or removed (a retry, an undo,
a deleted action), `forget_node` withdraws the memory attached to that coordinate and
rewinds both marks to just before the stretch it covered, so the ground is summarized again
from what the story now says. An earlier version instead held the newest action back a turn
so it could never be summarized before it stopped being retryable; that is no longer needed,
because the repair exists whether or not the invalidation happens at the tip.
so it could never be summarized before it stopped being retryable. That is no longer
needed, because the repair exists whether or not the invalidation happens at the tip.
**Cursors only advance on success.** Every AI call in this module is best-effort. If
summarization fails, the function returns and the cursor is unchanged, so the same block is
retried on a later turn. There is no retry loop, no dead-letter queue, no backoff — the
retried on a later turn. There is no retry loop, no dead-letter queue, and no backoff: the
cadence *is* the retry mechanism. Failures are logged to the debug page.
**Summarization is fire-and-forget, in a background task with its own DB session.** The
@@ -437,7 +437,7 @@ truncate and score garbage silently. An explicit length check returns 0.0 instea
**Eviction is LRU-ish, and evicted memories are kept.** Over capacity (default 200), the
least-used, least-recently-used unpinned memories are marked `forgotten` rather than
deleted — so the UI can still show them and you can un-forget one.
deleted, so the UI can still show them and you can un-forget one.
**Background calls never spend the shared demo key.** The summarization and embedding
providers are built directly from the user's own settings and never from the demo config,
@@ -454,7 +454,7 @@ anything makes a 20-second generation feel broken.
**Server-Sent Events (SSE)** is the mechanism: an HTTP response that stays open and pushes
`data: {...}` lines as they become available. It's one-directional (server → browser),
which is exactly what's needed here — WebSockets would be a bidirectional connection for a
which is exactly what's needed here. WebSockets would be a bidirectional connection for a
unidirectional problem.
The chain:
@@ -473,7 +473,7 @@ text), `stopped` (a script blocked the turn), `error`, `done`.
Two production details that only show up when hosted:
- `X-Accel-Buffering: no` — nginx-style reverse proxies buffer responses by default, which
- `X-Accel-Buffering: no`: nginx-style reverse proxies buffer responses by default, which
turns a stream into one big delivery at the end. This header tells them to flush each
event.
- The security-headers and body-size middlewares are written as **pure ASGI** rather than
@@ -481,7 +481,7 @@ Two production details that only show up when hosted:
break streaming.
**The empty-reply case is diagnosed, not reported as "empty".** If a reasoning model
streams thinking but no story text, it spent its whole budget thinking — the error says so
streams thinking but no story text, it spent its whole budget thinking. The error says so
and tells you which three settings to change.
---
@@ -498,18 +498,18 @@ The safety properties are mostly structural:
| Property | How |
|---|---|
| No filesystem, network, or process access | QuickJS has none by default — nothing was removed, nothing was added |
| No filesystem, network, or process access | QuickJS has none by default: nothing was removed, nothing was added |
| Memory cap | 16 MB per run |
| CPU cap | 2 seconds per run |
| No shared state between runs | A fresh `Context` per hook execution |
| A broken script can't break a turn | Every failure comes back as `.error` with text/state/cards unchanged; the pipeline logs it and continues |
Data crosses the boundary as JSON — Python serializes `{state, text, history, storyCards,
Data crosses the boundary as JSON: Python serializes `{state, text, history, storyCards,
info}` in, and the script's results out. There is no object bridge to exploit.
One deliberate bug-compatibility: `addStoryCard` returns the new card's *index*, so the
first card returns `0`, which is falsy, so `if (!addStoryCard(...))` misfires. That's
upstream AI Dungeon's behaviour. It's documented in the code and left alone, because
upstream AI Dungeon's behavior. It's documented in the code and left alone, because
matching real scripts is the whole point of the feature.
---
@@ -517,7 +517,7 @@ matching real scripts is the whole point of the feature.
## 1.8 Why there is no agent framework
Graph-based agent frameworks (LangGraph and similar) earn their complexity with
**branching, cyclic, multi-step control flow** — a graph of nodes where the path depends on
**branching, cyclic, multi-step control flow**: a graph of nodes where the path depends on
what the model decides, with loops, retries, tool calls, and persisted state between steps.
This turn pipeline is a **fixed linear sequence with exactly one model call**. There is no
@@ -533,13 +533,13 @@ abstraction, its serialization model, and its debugging surface to express a str
There is also a specific reason a framework's context handling wouldn't fit: **the
budgeting logic is the product.** Buffer-window and summary-memory abstractions are
opinionated about how to fit history into a window. Here the Insights panel exposes each
context component, its token cost, and the trigger word that pulled it in — which means the
assembly has to be explicit and inspectable.
context component, its token cost, and the trigger word that pulled it in, so the assembly
has to be explicit and inspectable.
**When it would be the right call:** if the design went toward the two-call version —
narrate, then a separate structured-extraction step, with a retry branch when extraction
fails and a tool-calling path for dice — that is a graph, and hand-rolling it would get
ugly fast.
**When it would be the right call:** if the design went toward the two-call version, where
narration is followed by a separate structured-extraction step, with a retry branch when
extraction fails and a tool-calling path for dice, that is a graph, and hand-rolling it
would get ugly fast.
---
@@ -576,8 +576,8 @@ behind it.
### The problem
The story used to be a list, and a mutable one. Retry rewrote the last entry in place;
undo and delete removed entries from the middle. Everything derived from the story —
the memories, the running summary, the two marks saying how far each had got — was
undo and delete removed entries from the middle. Everything derived from the story, such as
the memories, the running summary, and the two marks saying how far each had got, was
indexed by *position in that list*, and a position means something different after
anything in front of it is deleted.
@@ -603,8 +603,8 @@ Make the story a tree, and none of them are reachable.
Every action is a **node** with a `branch_id` and a `depth`. A **branch** is one line
through the tree; it holds the nodes played on it and *borrows* everything before its
fork point from its ancestors. Nothing is ever copied and — apart from an explicit
delete — nothing is ever removed.
fork point from its ancestors. Nothing is ever copied, and apart from an explicit delete,
nothing is ever removed.
```
branches(id, adventure_id, parent_branch_id, fork_depth, lineage, name)
@@ -636,38 +636,38 @@ keep the shape they already had.
### The lineage, and why fork count doesn't cost anything
The OR-clause above is not reconstructed per read. It is stored on the branch row as
`lineage` — `[(C, ∞), (B, 5), (A, 3)]` — computed once when the fork happens, from the
parent's lineage plus one entry. `context/lineage.py` is the only module that knows how
to turn it into a query, which is deliberate: one forgotten clause shows the wrong story
and reports nothing.
`lineage`, for example `[(C, ∞), (B, 5), (A, 3)]`, computed once when the fork happens,
from the parent's lineage plus one entry. `context/lineage.py` is the only module that
knows how to turn it into a query, which is deliberate: one forgotten clause shows the
wrong story and reports nothing.
Two properties of the shape do the real work:
- **The ranges are disjoint and descending.** A branch's own nodes always sit deeper than
its fork point, and each ancestor is capped at the fork depth of the branch beneath it.
So ordering the whole clause by `depth DESC` reads entry 0's nodes, then entry 1's,
then entry 2's — which means a tail read can use the newest few entries and stop.
then entry 2's, which means a tail read can use the newest few entries and stop.
- **Clause count is bounded by the context window, not by fork count.** A 200-fork story
whose newest branch is 40 turns long reads with *one* clause, because the window is
covered before the second entry is reached.
A branch stores no story of its own, so a fork costs an id, a parent, a fork depth and a
cached ancestry. Measured on a 40-turn story forked twenty times against the same story
flat: a page load of **31,652 B against 31,433 B — 1.007×**, or about **103 bytes per
branch**. No migration, no vacuum, no copy.
flat: a page load of **31,652 B against 31,433 B, a 1.007× ratio**, or about **103 bytes
per branch**. No migration, no vacuum, no copy.
### What a player actually does
None of the above is what the screen shows. In the player's words:
> Any turn can gain another **take**. On an AI turn that means regenerate; on your own
> message it means type something else. Stepping between takes with `‹ 2/4 ›` is free —
> message it means type something else. Stepping between takes with `‹ 2/4 ›` is free:
> the story below simply empties, because that take has no children yet. **A branch is
> created when you write below a take that is not the live one**, never before.
That rule collapses two operations into one and deletes a distinction from the UI. The
first version of this screen had a chip that *switched* at the tip and only *previewed*
above it, with a second button to take that line — one control whose meaning depended on
above it, with a second button to take that line: one control whose meaning depended on
where the reader was standing. The rule above replaced it with a pager that only ever
steps, a fork button on every turn, and no tip-versus-past distinction at all. The
distinction survives in the implementation, where it decides whether a write needs a
@@ -678,7 +678,7 @@ switch and no branch is created.
The load-bearing detail, and the one that is not obvious.
The natural way to find "the other takes of this turn" is by coordinate — same branch,
The natural way to find "the other takes of this turn" is by coordinate: same branch,
same depth. It is wrong in both directions:
```
@@ -693,8 +693,8 @@ land on different branches. It gets `C` wrong: once C has been forked onto a bra
its own it is alone at its coordinate and reads `1/1`, having lost C1 and C2 from a pager
that must still say `1/3`.
So a node carries `parent_id`, read for nothing but this. The alternative — making a
branch's fork point a *node* rather than a depth, so a promoted take never moves — was
So a node carries `parent_id`, read for nothing but this. The alternative, making a
branch's fork point a *node* rather than a depth so a promoted take never moves, was
rejected: the whole point of `lineage` is that a read is an OR-clause per branch instead
of a walk up parent pointers, and re-pointing the fork at a node changes path resolution
itself, dragging in the cursors, memory depths and both bundle formats. `parent_id` is
@@ -702,7 +702,7 @@ one indexed lookup, never a walk, and nothing about how a path resolves changes.
### Cursors become anchors
The two marks — how far the memory bank has got, how far the summary has got — used to
The two marks, how far the memory bank has got and how far the summary has got, used to
be counts. A count is a position in a list, and every rule about sliding them, rewinding
them and translating between positions and `Action.index` existed to patch up the fact
that the list moves.
@@ -720,23 +720,23 @@ existed because a retry could rewrite an action the mark had already passed.
### Derived work attaches to the node that produced it
Generalise the rule and a lot falls out: *anything derived hangs off the node that
produced it*. A memory covering depths 37–42 hangs off that branch's node 42 and is
Generalize the rule and a lot falls out: *anything derived attaches to the node that
produced it*. A memory covering depths 37–42 attaches to that branch's node 42 and is
invisible to any path that does not run through it. Shared ancestors are therefore shared
automatically, so **a fork needs nothing recreated** — the memories above the fork point
automatically, so **a fork needs nothing recreated**: the memories above the fork point
are already on the ancestors both lines read.
The subtle case is the memory sitting *at* the forked coordinate. The first cut moved it
onto the new branch and re-anchored the marks naming it. Both are wrong for the same
reason: that memory describes whichever attempt was live at that coordinate, which is the
one staying on the parent. The right answer needs no code — the lineage caps the parent
one depth short of the fork, so the memory is simply out of range from the new branch,
one staying on the parent. The right answer needs no code: the lineage caps the parent one
depth short of the fork, so the memory is simply out of range from the new branch,
invisible to both the retrieval clause and the anchor read. The new line summarizes that
ground again, from the text it actually tells.
Hand-written memories obey the same rule. One used to carry a NULL depth, described as
"belongs to the adventure rather than to a path" — which sounds harmless and is not: a
NULL is a coordinate no fork can cap, so a note typed on one line followed the reader onto
"belongs to the adventure rather than to a path". That sounds harmless and is not: a NULL
is a coordinate no fork can cap, so a note typed on one line followed the reader onto
branches whose events it never described. They are anchored at the head instead: *the
story you were reading when you wrote it*.
@@ -747,7 +747,7 @@ also why branch management could not be a nice-to-have: without a way to delete
storage grows without limit.
The delete rule has two halves and the second is easy to miss. Refusing to delete the
line being read is obvious. The other half is refusing any line it was **forked from** —
line being read is obvious. The other half is refusing any line it was **forked from**:
`parent_branch_id` cascades, so deleting an ancestor takes the head with it and leaves
`head_branch_id` pointing at a row that is gone. One membership test against the head's
own lineage covers both, because a lineage already names itself and every branch it
@@ -757,7 +757,7 @@ button can say so before it is pressed.
### The migration, and what it deliberately did not do
There is no feature flag. **A linear story is a tree with one branch**, so the
intermediate states were not half-migrated — they were the same product with a superset
intermediate states were not half-migrated: they were the same product with a superset
schema underneath, which made "existing adventures are unaffected" a literal, testable
pass condition at every step. A flag would have bought two live code paths through the
context builder, the memory bank, undo and retry at once.
@@ -767,8 +767,8 @@ were kept unread for a release rather than dropped with the migration that stopp
them, so that a redeploy of the previous build is still a way out. Dropping columns is the
one step that isn't.
One operational note that generalises: on Postgres, a migration that rewrites every row of
`actions` roughly doubles the table and only `VACUUM FULL` gives it back — 79 MB reclaimed
One operational note that generalizes: on Postgres, a migration that rewrites every row of
`actions` roughly doubles the table, and only `VACUUM FULL` gives it back: 79 MB reclaimed
in 5.5 s on one occasion. But bloat scales with the **heap**, and `context_snapshot` is 94%
of this table and lives out of line, so a migration touching only small columns reuses the
existing TOAST pointer and costs a tenth of that. Read the sizes from `sum(octet_length())`
@@ -779,14 +779,14 @@ makes bloat look smaller.
- **The two marks are one pair on the adventure**, not one per branch. Switching branches
makes the mark on the line being left unreadable from the new one, and that ground is
summarized again. It answers "nothing covered", which is the safe direction — redo the
work, never skip it — but switching back and forth costs AI calls. Per-branch cursors
summarized again. It answers "nothing covered", which is the safe direction: redo the
work, never skip it. But switching back and forth costs AI calls. Per-branch cursors
are the fix if it ever matters.
- **Story cards stay adventure-wide.** A card invented on branch B shows on branch A.
Event-sourcing card changes onto nodes was considered and rejected.
- **Editing an already-summarized action still leaves its memory stale.** The machinery to
fix it now exists — an edit could write a sibling take and switch to it, which is a retry
the player typed — but it does not do that yet.
fix it now exists: an edit could write a sibling take and switch to it, which is a retry
the player typed. It does not do that yet.
## 2.3 Undo and retry that actually rewind
@@ -794,17 +794,17 @@ Most implementations of undo delete the last message. That's wrong here, because
mutates three things: the text, the scripting scoreboard (`script_state`), and the RPG
stats (`world_state`).
**The mechanism:** every node carries `state_after` and `world_state_after` — deep copies
**The mechanism:** every node carries `state_after` and `world_state_after`, deep copies
of what the adventure looked like once that turn had played. Rewinding to before a turn is
a read of the node in front of it, so undo, retry and a branch switch are the same
restore. The cooldown clock comes along for free: it lives inside the world state, in
`_meta.last_changed`, so each line of the story carries its own without anything having to
know there is one.
**Nothing a retry replaces is thrown away.** The old attempt stays as another **take** of
that turn — a sibling node at the same coordinate, `live` false — and the pager steps
between them. Which is to say retry is not a special case: it is the tree, with the branch
not yet created. See [2.2](#22-the-story-is-a-tree).
**Nothing a retry replaces is discarded.** The old attempt stays as another **take** of
that turn, a sibling node at the same coordinate with `live` set to false, and the pager
steps between them. Retry is not a special case: it is the tree, with the branch not yet
created. See [2.2](#22-the-story-is-a-tree).
Three details that are easy to get wrong:
@@ -825,9 +825,10 @@ take belonging to a line nobody asked about. Anything that reads a take group an
*writes* has to say whether it means the turn or the coordinate.
**If the regeneration fails, the rollback is reversed.** `generate_turn` wraps the
generator in a `try/finally`: if it ends without saving — a provider error, an empty reply,
a script `stop`, or the browser hanging up — the previous take is put back in charge.
Otherwise the state on the server would drift from the text still on the user's screen.
generator in a `try/finally`: if it ends without saving, whether from a provider error, an
empty reply, a script `stop`, or the browser hanging up, the previous take is put back in
charge. Otherwise the state on the server would drift from the text still on the user's
screen.
## 2.4 The turn lock
@@ -854,11 +855,11 @@ async def with_turn_lock(adventure_id, gen): # wraps the SSE generator
```
In-memory, so it's a single-process guarantee. That's honest for the deployment this
targets — one Render web service. Two processes would need the lock in the database.
targets: one Render web service. Two processes would need the lock in the database.
## 2.5 The 189x egress fix
**The setup:** `Action.context_snapshot` holds the entire assembled prompt for a turn —
**The setup:** `Action.context_snapshot` holds the entire assembled prompt for a turn,
about 74 KB per row, 94% of the database.
**The bug:** every adventure load pulled that column for every action, to read two small
@@ -869,7 +870,7 @@ report). SQLAlchemy loads all columns by default.
1. Move the two small things that *are* needed for every action into their own column
(`Action.world_delta`).
2. Mark the heavy columns `deferred` — `context_snapshot`, `variants`, `reasoning` — so
2. Mark the heavy columns `deferred` (`context_snapshot`, `variants`, `reasoning`), so
they're only fetched when explicitly asked for.
3. Backfill the new column with dialect-specific server-side SQL, so the old data is
extracted inside the database and never crosses the wire.
@@ -883,7 +884,7 @@ not on a timing.
One more detail from that test's design: the count query is written as a real
`SELECT count(...)` rather than `query.count()`, because SQLAlchemy's `.count()` wraps the
entity select in a subquery, so the emitted SQL names every column — including the deferred
entity select in a subquery, so the emitted SQL names every column, including the deferred
ones. No bytes come back either way, but the database still has to read them, and a guard
that greps SQL cannot tell the two apart.
@@ -899,7 +900,7 @@ No Alembic. An append-only list of `(version, SQL)` pairs, with the current vers
in SQLite's `PRAGMA user_version` or a one-row table on Postgres. 64 versions so far.
- A **fresh** database is created by `Base.metadata.create_all()` (always current) and
stamped at the latest version — it never replays history.
stamped at the latest version; it never replays history.
- An **existing** database runs every migration above its stored version, in order.
Why this and not Alembic: for a single-file SQLite app that a user might have been running
@@ -909,9 +910,9 @@ environment. This is 250 lines and you can read all of it.
The constraint it creates is written at the top of the file: change `models.py` (so fresh
databases are current) *and* append a pair here (so existing ones upgrade). Migrations 2–23
predate Postgres support and use SQLite-only syntax — harmless, because every Postgres
database starts fresh and never replays them, but anything added since must run on both
dialects.
predate Postgres support and use SQLite-only syntax. This is harmless, because every
Postgres database starts fresh and never replays them, but anything added since must run
on both dialects.
One migration worth reading (#10, repairing duplicate action indexes) uses `UPDATE … FROM`
with a window function rather than a correlated subquery, because SQLite may evaluate a
@@ -929,7 +930,7 @@ correlated subquery against partially-updated rows and produce duplicates again
| | Local (default) | Hosted |
|---|---|---|
| Users | One auto-created "local user" | Guest on first visit, optional account |
| Auth | None — no cookies, no login UI | Signed session cookie |
| Auth | None: no cookies, no login UI | Signed session cookie |
| Rate limits | Off | On |
| Row caps | Off | On |
| API docs (`/docs`) | On | Off |
@@ -941,13 +942,13 @@ deployment needs all four of those to be the opposite. Rather than two builds, t
differences are gated at each site.
**Guests upgrade in place.** A visitor gets a guest `User` row on first load. Registering
sets `email` and `password_hash` on that *same row* — so every adventure they played as a
sets `email` and `password_hash` on that *same row*, so every adventure they played as a
guest survives with no re-parenting and no migration step. Three kinds of row share the
users table: local (email NULL, not guest), guest (email NULL, guest), registered (email
set).
**Guests expire; accounts don't.** One row per curious visitor adds up, so `cleanup.py`
deletes guests idle for `AIDND_GUEST_RETENTION_DAYS` (default 5) — measured as
deletes guests idle for `AIDND_GUEST_RETENTION_DAYS` (default 5), measured as
`COALESCE(last_seen_at, created_at)`, because `_touch` only writes `last_seen_at` hourly
and a guest minted by `/auth/me` has NULL until its second request. The filter requires
both `is_guest` *and* `email IS NULL`, so upgrading in place is also how you opt out of
@@ -957,7 +958,7 @@ every few hours.
It's a single Core `DELETE`, not `db.delete(user)`: the ORM path would SELECT every
adventure, action and memory into Python purely to delete them, and the FK graph is
`ON DELETE CASCADE` from `users` all the way down, so the database can do the whole graph
in one statement. Nothing a guest owns is visible to anyone else either — `is_public` is
in one statement. Nothing a guest owns is visible to anyone else either: `is_public` is
output-only, so shared content is exactly the seeded scenarios, which have `user_id NULL`
and never match the filter.
@@ -969,11 +970,11 @@ is a spending surface, so it's the most defended code in the project.
`resolve_provider_config()` is the single place the BYOK-vs-demo decision is made, and on
the demo branch it pins **two** things:
- **The model** — to a whitelist. A caller-supplied override or a hand-edited settings row
can't aim a server-funded key at an expensive model. Anything unrecognised falls back to
the first whitelisted model.
- **The endpoint** — to the configured demo URL. Otherwise the key could be redirected to a
URL the user controls and harvested.
- **The model**, pinned to a whitelist. A caller-supplied override or a hand-edited
settings row can't aim a server-funded key at an expensive model. Anything unrecognized
falls back to the first whitelisted model.
- **The endpoint**, pinned to the configured demo URL. Otherwise the key could be
redirected to a URL the user controls and harvested.
Plus a daily per-user turn cap (default 20), checked *before* the player's input is stored
so a capped player doesn't get their message saved with no reply, and counted only after a
@@ -982,12 +983,12 @@ successful turn.
There's a defensive `__post_init__` on the config object that raises if a demo config
somehow carries a non-whitelisted model. The comment on it records a real bug: the check
tests `using_demo`, **not** `api_key == DEMO_API_KEY`. Keying on the key value looks
stricter but is wrong — the demo key is an ordinary OpenRouter key, so a user can
stricter but is wrong: the demo key is an ordinary OpenRouter key, so a user can
legitimately paste that same key into their own settings as BYOK, and then every resolution
raised, 500ing even `GET /auth/me` and taking the whole SPA down. `using_demo` is what
actually means "the server is paying".
Background work (summarization, embeddings) is excluded from the demo key entirely — those
Background work (summarization, embeddings) is excluded from the demo key entirely: those
are unmetered calls, and unmetered calls on a server-funded key is a bill.
## 3.3 Secrets
@@ -997,11 +998,11 @@ Everything derives from one server-side secret (`AIDND_SECRET_KEY`).
| Thing | Mechanism |
|---|---|
| Passwords | `hashlib.scrypt`, N=2^14, r=8, p=1, per-password salt, constant-time compare. Stdlib, so no extra dependency. |
| Sessions | `v1.<user_id>.<HMAC-SHA256>`, no expiry — long-lived guest sessions are the point. A cookie can outlive a swept guest row; that resolves to a 401, which the frontend already turns into a fresh session. |
| Stored LLM API keys | Fernet (AES) encryption at rest, key derived from the secret, `enc:` prefix so legacy plaintext rows are recognisable and migratable. |
| Sessions | `v1.<user_id>.<HMAC-SHA256>`, no expiry: long-lived guest sessions are the point. A cookie can outlive a swept guest row; that resolves to a 401, which the frontend already turns into a fresh session. |
| Stored LLM API keys | Fernet (AES) encryption at rest, key derived from the secret, `enc:` prefix so legacy plaintext rows are recognizable and migratable. |
The secret auto-generates into a file next to the database for local installs (zero config),
but **multi-user mode refuses to start without the env var** — with an error message that
but **multi-user mode refuses to start without the env var**, with an error message that
explains why and gives you the command to generate one. Hosted filesystems are ephemeral; a
regenerated secret on every deploy would silently log out every user and orphan their stored
API keys.
@@ -1025,11 +1026,11 @@ rather than raising, so the user just re-enters their key instead of hitting a 5
Rate limits are keyed per user when one is known (accounts survive IP changes) and per IP
otherwise, in fixed windows held in memory, with a pruning pass so the per-IP dict can't
grow without bound. Import endpoints check bundle list lengths against the same caps live
creation enforces — otherwise the cap is trivially bypassed by uploading a file.
creation enforces, otherwise the cap is trivially bypassed by uploading a file.
Security headers on every response: `nosniff`, `X-Frame-Options: DENY`,
`Referrer-Policy: same-origin`, and a CSP allowing exactly what the SPA uses — same-origin
everything, inline styles (React needs them), Google Fonts.
`Referrer-Policy: same-origin`, and a CSP allowing exactly what the SPA uses: same-origin
everything, inline styles (React needs them), and Google Fonts.
## 3.5 Deployment
@@ -1053,13 +1054,13 @@ push.
A hosted demo raises a question a local app never does: is anyone using it, and do they get
anywhere? The answer is an owner-only dashboard at `/analytics`, gated on
`AIDND_ANALYTICS_EMAILS` — a list kept separate from `AIDND_POWER_USERS`, since an unmetered
`AIDND_ANALYTICS_EMAILS`, a list kept separate from `AIDND_POWER_USERS`, since an unmetered
tester is not automatically someone who should see the traffic.
**Why it isn't a third-party script.** The CSP allows `script-src 'self'`, so a tracker would
mean loosening it; adblockers eat the popular ones, which silently biases exactly the
technical audience this project is shown to; and none of them can see the measurement that
matters here — a *turn*. The interesting funnel step is not a pageview.
mean loosening it. Ad blockers block the popular ones, which silently biases exactly the
technical audience this project is shown to. And none of them can see the measurement that
matters here: a *turn*. The interesting funnel step is not a pageview.
**Egress is the budget.** After the 189x fix (§2.5) it would be perverse to add a feature
that reads rows per request. So counts accumulate in a process-local dict and flush every 60
@@ -1068,23 +1069,23 @@ seconds as UPSERTs: **a visit is a write and never a read**. Storage is a generi
Every dashboard query is a `GROUP BY` that returns tens of rows regardless of the traffic
behind it, so a month costs a few kilobytes to read back. The cost of the buffer is that a
hard restart can lose up to a minute; the flusher also runs on shutdown, and on a tier that
sleeps when idle the buffer it sleeps on is empty anyway.
sleeps when idle, the buffer it sleeps on is empty anyway.
**The numbers are the server's, not the browser's.** The client reports one fact — which page
was viewed — and even that is normalized to a route (`/play/12` → `/play/:id`) against a
**The numbers are the server's, not the browser's.** The client reports one fact, which page
was viewed, and even that is normalized to a route (`/play/12` → `/play/:id`) against a
whitelist, so the page list cannot be polluted by anything a stranger posts. Everything that
means something — a turn, an adventure, a sign-up — is recorded by the code that performs it.
That also fixes a blind spot: a failed turn is an HTTP 200 with a bad ending, so a
status-code tally cannot see it, and a demo whose model has started refusing looks perfectly
healthy from outside. `turn_error` is counted where the SSE error is written.
means something, such as a turn, an adventure, or a sign-up, is recorded by the code that
performs it. That also fixes a blind spot: a failed turn is an HTTP 200 with a bad ending, so
a status-code tally cannot see it, and a demo whose model has started refusing looks
perfectly healthy from outside. `turn_error` is counted where the SSE error is written.
The funnel counts **people, not clicks** — a player who starts six adventures is one person
who started an adventure — which is the entire reason the per-visitor-day table exists.
The funnel counts **people, not clicks**: a player who starts six adventures is one person
who started an adventure, which is the entire reason the per-visitor-day table exists.
One smaller decision worth naming: error buckets are labelled by the matched *route template*,
never the requested path. That gives one bucket per endpoint instead of one per adventure id,
and — the reason it isn't merely tidier — an unmatched path is entirely attacker-chosen, so
labelling by it would let anyone mint rows.
One smaller decision worth naming: error buckets are labeled by the matched *route
template*, never the requested path. That gives one bucket per endpoint instead of one per
adventure id. The reason it isn't merely tidier is that an unmatched path is entirely
attacker-chosen, so labeling by it would let anyone mint rows.
---
@@ -1092,9 +1093,9 @@ labelling by it would let anyone mint rows.
For the parts that are just how the web works, not decisions.
**Frontend and backend are two programs.** In development they're two servers — Vite on
5173 serving React, FastAPI on 8000 serving the API — and Vite proxies `/api` to FastAPI so
the browser thinks it's all one origin (which avoids CORS entirely). In production there's
**Frontend and backend are two programs.** In development they're two servers: Vite on 5173
serving React, and FastAPI on 8000 serving the API. Vite proxies `/api` to FastAPI so
the browser thinks it's all one origin, which avoids CORS entirely. In production there's
one server: FastAPI serves the built React files as static assets from the same port.
**SPA routing.** React Router handles URLs like `/play/3` in the browser without a round
@@ -1105,7 +1106,7 @@ unaffected.
**Sessions.** A cookie is a small value the browser stores and automatically attaches to
every request to that site. Here it holds `v1.<user_id>.<signature>`. The server doesn't
store sessions anywhere — it re-verifies the signature on each request, which is why there's
store sessions anywhere; it re-verifies the signature on each request, which is why there's
no session table.
**The 401 retry.** If the cookie is missing or stale, any API call returns 401. The frontend
@@ -1136,7 +1137,7 @@ text appears to type itself.
| Context defaults | author's note at depth 3, cards capped at 40% of elastic budget |
| Memory cadence | memory / 6 turns, summary / 15 turns, top-5 retrieval |
Two of the tests encode a performance property rather than a behaviour:
Two of the tests encode a performance property rather than a behavior:
`test_egress.py` asserts on the SQL the ORM emits, and `test_history_window.py` asserts
that the read cost stops growing with story length.
@@ -1150,7 +1151,7 @@ nobody has to discover them the hard way.
lock) and the rate limiter in Redis.
- **No vector index.** Retrieval does cosine similarity in Python over the whole bank. Fine
at the 200-memory cap; at 10,000 it would want pgvector.
- **Prompt snapshots are heavy** even after the egress fix — they're deferred, not smaller.
- **Prompt snapshots are heavy** even after the egress fix; they're deferred, not smaller.
Compressing them or expiring old ones is the real fix.
- **In-memory rate-limit windows reset on restart**, so a restart grants a brief extra
allowance.
@@ -1160,7 +1161,7 @@ nobody has to discover them the hard way.
detect after the fact by string-matching the 429 body.
- **The two memory marks are one pair on the adventure, not one per branch.** Switching
lines makes the mark on the line being left unreadable from the new one, so that ground is
summarized again. It fails in the safe direction — redo, never skip — but switching back
summarized again. It fails in the safe direction: redo, never skip. But switching back
and forth costs AI calls. Per-branch cursors are the fix if it matters.
- **Story cards are adventure-wide**, so a card invented on one branch shows on all of them.
- **Editing an already-summarized turn leaves its memory stale.** Replacing a turn withdraws
@@ -1168,8 +1169,8 @@ nobody has to discover them the hard way.
## Cleanup backlog
`docs/self-review.md` carries an open list of non-bugs — reuse, simplification and
efficiency items — kept deliberately separate from the correctness list, which is empty.
`docs/self-review.md` carries an open list of non-bugs (reuse, simplification, and
efficiency items) kept deliberately separate from the correctness list, which is empty.
The largest ones:
- `Section.tokens` is uncached, so the context gets tokenized two or three times a turn.