flan/FIX.org

• Stuff I've found
  • Why do I need to call flan to open another window?
  • I can't eval a toplevel defvar, need to eval-defun (C-c C-c)
  • I can't eval a top level Vec
  • The edn module seems to need a struct declaration, it should do both; go into a struct but also return a Map with Vecs and Sets when we don't provide a type
  • defenum needs optional autoincrementing discriminants
  • We need a javascript backend so we can reach the world
  • We need to have C-style unions, maybe those are called defunion, and then sum types are defdata or deftype
• Decisions, 2026-09-17
  • 1. Re-runnable main — DISPATCHED
  • 2. C-x C-e on a top-level form — QUEUED behind 1
  • 3. Runtime-loaded owning globals — DISPATCHED
  • 4. edn both typed and dynamic — REDIRECTED to arenas, drop parked
  • 5. defenum autoincrement — DISPATCHED
  • 6. JavaScript backend — HELD
  • 7. defdata and defunion — QUEUED last
• Open, found while working the list
  • A transient signal -11 on the globals daemon
• Status, end of 2026-09-17
  • Parked branches, kept deliberately
  • Open, carried forward
• Landed on dev-loop
  • Re-run is merged, and does not work under –x86
  • C-x C-e answers against a parked program
  • The headline complaint is verified fixed on sand.flan
• Evening of 2026-09-17 — the review, and four lanes off it
  • All four lanes merged, end of 2026-09-17 evening
• The repeal, 2026-09-18
• The second round, 2026-09-18 — Pool, move-only, and the gen word
• End of 2026-09-18 — the hunt closed out
• Late 2026-09-18 — the last two lanes
• The dynamic half of item 4, finished
• Session close, 2026-09-20 — dynamic-first M1 landed
  • Still in flight, worktree branches to merge when they report
  • Open, author's call
• M2 queue, decided with the author 2026-09-20 — in order
  • The two models, named 2026-09-19
  • Arithmetic semantics do not fork across the two spaces, decided 2026-09-20
  • handler-case, decided 2026-09-19
  • The JS backend answers string equality wrongly, parked 2026-09-19
  • Sweep policy, decided 2026-09-19
• handler-case, decided 2026-09-19
• Surface syntax discussion, 2026-09-19
• The x86 backend tracks LLVM -O0, decided 2026-09-20
  • The aspiration: tests that say x86 still tracks -O0

Stuff I've found

Why do I need to call flan to open another window?

let: flan: the program exited; restart flan dev

I can't eval a toplevel defvar, need to eval-defun (C-c C-c)

For Flan’s intended live-program workflow, C-x C-e on any complete top-level form should do the natural thing:

• expression → compile/run temporary thunk; print its value
• defn, defvar, defmacro, etc. → compile/install it; report what changed

The compiler already has both paths. The current split is an editor/UI artifact: C-x C-e is wired directly to eval-expr, while C-c C-c is wired to declaration reload. It is not a fundamental limitation.

A good fix would make C-x C-e context-aware: if the enclosing form is top-level, send it through the declaration evaluator; otherwise use expression evaluation. Then C-c C-c can remain a convenient explicit “reload this definition” alias, but not the only way defvar works.

I can't eval a top level Vec

slurp returns (Vec u8), an owning, move-only buffer. Flan currently forbids every move-only global because it has no global ownership/lifetime model: any function could read and free it, while ownership tracking only exists within one function.

For data that is fixed at build time, use an embedded immutable array instead:

(defconst the-data (embed "game-data.edn"))

That produces a fixed [u8], not a heap-owning Vec, so it can live globally. It also resolves relative to sand.flan.

If game-data.edn genuinely must be loaded at runtime, then today it has to be owned by a local—typically load it in main and pass it through the functions that need it. For a game-wide runtime-owned data asset, that is a missing language/runtime feature, not a bad use case on your part.

The edn module seems to need a struct declaration, it should do both; go into a struct but also return a Map with Vecs and Sets when we don't provide a type

defenum needs optional autoincrementing discriminants

We need a javascript backend so we can reach the world

We need to have C-style unions, maybe those are called defunion, and then sum types are defdata or deftype

Decisions, 2026-09-17

1. Re-runnable main — DISPATCHED

The process does not actually die. [flan_exit_hook] is [flan_merged_exit] (lib/dev.ml:2669): it flushes, reclaims fd 1, and parks in [for (;;) pause()]. What is missing is a way to wake it. The park becomes a condvar wait, a daemon op signals it, and the main thread — not a new one, because raylib wants the main thread — re-enters [flan_program_main]. [alive] gains a third state, parked-and-re-runnable, and each of the ten guard sites decides for itself whether it accepts one.

Globals are NOT reset between runs. That is the CL/Clojure semantics asked for: the process never died, so a second (main) sees what the first one left.

2. C-x C-e on a top-level form — QUEUED behind 1

Same file as 1 (emacs/flan.el), so it waits rather than merging by hand. No design questions; the note specifies it.

3. Runtime-loaded owning globals — DISPATCHED

Not a missing global ownership model. One rule: a move-only global is legal, and reading one is always a borrow, never a move. Nothing takes ownership, nothing frees it, its lifetime is the process's. Sound precisely because the lifetime question has a constant answer.

Mutable in place as well — a global Vec can be pushed to. Aliasing follows whatever locals already do; no new borrow regime for globals that locals lack.

[embed] (lib/check.ml:4265) still covers build-time data and is untouched.

4. edn both typed and dynamic — REDIRECTED to arenas, drop parked

Two projects, not one. (read-edn T bytes) does not exist — vendor/edn/edn.flan is only a tokenizer, and the compile-time struct walk is NEXT.md item 9.

[drop] was dispatched to unblock the dynamic half and is being PARKED unmerged on its branch, not reverted, because the premise was wrong. The refusal at check.ml:599 is about teardown, not ownership: the type-erased runtime releases slots bytewise and cannot walk a move-only element. An arena never releases a slot — [free-all] takes the whole region — so the premise does not hold there.

That is also what Odin does, which NEXT.md:1620 already recorded: no destructors, no drop, no finalizers; [delete] frees container memory and nothing else. core:encoding/json ships a hand-written recursive [destroy_value] in the library, and the idiomatic alternative is to parse against temp_allocator and [free_all]. Neither is a language feature. Building [drop] was a departure from NEXT.md:1589's settled "defer stays the answer", taken on the assistant's prompting and withdrawn.

So: lift check.ml:599 for arena-allocated containers, and let read-edn take an allocator — which is already the idiom, since spec-memory.md:283 makes the allocator part of the calling convention with an explicit override.

The real cost, stated because it is not free: [can-free] is a RUNTIME capability on the allocator value while check.ml:599 is a COMPILE-TIME refusal, and the compiler cannot generally know statically that a construction site's allocator is an arena. The spec's answer for the analogous drop case is a check at the point of construction, one branch per container — a runtime branch. This likely becomes a runtime trap rather than a static guarantee.

Ownership tracking itself is untouched. Moves are still tracked; what is given up is freeing one element individually, which is the point of an arena.

5. defenum autoincrement — DISPATCHED

C's rule: no value means previous+1, the first is 0, explicit and implicit mix.

Duplicates: an explicitly written one is an intended alias and is allowed. One produced by autoincrement walking into a value another member holds is an accident and is refused, naming both members.

6. JavaScript backend — HELD

wasm32 already works: test/wasm-run.mjs is a WASI host, the test table runs wasm32 builds, web/index.html is in the tree. A second backend beside emit.ml and x86.ml is the largest item here and the dev loop comes first.

7. defdata and defunion — QUEUED last

Today's [defunion] is already the tagged sum type. It is renamed [defdata], and [defunion] becomes the C-style untagged one. Serves both FFI and type punning, and cimport verifies it against the header where one exists — cimport.ml:295 currently skips any record holding an anonymous union, leaving the defstruct beside it unchecked.

Last, because the rename sweeps parse/check/emit/prelude/docs and every .flan file, and would conflict with everything above.

Open, found while working the list

A transient signal -11 on the globals daemon

Seen once, in one of three consecutive test runs, by the agent doing the C-x C-e work; the runs either side of it were clean. Not reproduced since — three forced full runs (dune test –force) are green, 232 checks, 0 failures.

Worth remembering rather than chasing, because the daemon it appeared on is one the move-only-global work (c124df3) changed: test_reload's fixture gained a host global Vec and a run-time-new one. A teardown or a reload module that defines rather than declares a global Vec would strand the block the live process is using, which is exactly the shape a rare SIGSEGV takes. If it comes back, start there.

Status, end of 2026-09-17

Six of seven items are merged on dev-loop and green (dune build, dune test –force, @x86, @page). One agent is still running: the arena work for item 4.

item	what	state
1	re-runnable main after the window closes	merged
2	C-x C-e installs a top-level form	merged
3	move-only globals, borrowed never moved	merged
4	edn dynamic value	merged (arena route)
5	defenum autoincrement	merged
6	javascript backend	first lane IN FLIGHT, 2026-09-17 evening
7	defdata rename + C-style defunion	merged

Also merged, not from the list: macro-module symbol visibility, which unblocked [flan dev –x86] in one process. sand.flan –x86 builds in 292ms against 985ms on LLVM.

Parked branches, kept deliberately

• worktree-agent-a18e9e62485eaedb5 — [drop] and recursive teardown. Finished and green, not merged. See docs/handoffs/HANDOFF-drop.md, which is the part worth keeping. Withdrawn because the refusal it answered is about teardown, and an arena has none; see item 4 above.

Open, carried forward

• A transient signal -11 on the globals daemon, seen once, not reproduced. Recorded below.
• [drop]'s handoff flags that the [clone] / [get] / [map-next] refusals are needed by the arena route too — they are about a copy of a header, which an arena does not make safe — and that a Map has no operation answering where a value lives, which is what reading an arena-parsed EDN document back would need. Both were relayed to the arena agent.
• [Tast.Addr (Tast.Pfield …)] on an Option: closed, and closed as unreachable rather than fixed. Nothing in the source language builds it. [.field] goes through [struct_target], which admits a struct and a pointer to one and refuses everything else by name with a location — "(Option Point) is not a struct, so it has no fields" — so [(addr (.x o))] never reaches a place for [addr] to take. The node the drop lane hit was one the compiler built for itself. Two rows in test_flan.ml pin the refusal, on the bare field and on the address of one. What is still asymmetric, and is a note rather than a bug: [x86.ml]'s [field_loc] does lay out an Option's tag and value, and [emit.ml]'s [place] admits only a named struct. Neither is reachable, so neither is tested, and growing the LLVM side to match would be untestable code written to balance a path nothing takes.
• Re-run still does not work under –two-process: a finished child is genuinely gone. It now works under –x86 because –x86 runs merged.
• sand.flan still holds an uncommitted experiment line that is refused with a message naming the fix: use (defvar the-data (Vec u8)) and fill it in a function.

Landed on dev-loop

Items 1, 2, 3 and 5 are merged and green (dune test –force, 232 elisp checks, 0 failures). Items 4 (drop) and 7 (defdata) are still being written. Item 6 is held.

Re-run is merged, and does not work under –x86

Park and re-run live in the merged entry point's main(), and –x86 refuses the merged daemon by design: a merged host exports every flan.* body for -rdynamic and so interposes the prelude bodies of the LLVM-built macro module the compiler loads into itself. –x86 therefore runs –two-process, where the program is a child, and a child that finishes is genuinely Gone — there is nothing to wake. [Program.rerun] answers with the two-process refusal rather than the merged one, and a test pins it.

Re-run on x86 needs the merged daemon to accept –x86 first. Separate work.

C-x C-e answers against a parked program

The complaint: (+ 1 1) at the top of a buffer was refused with "an expression is evaluated at a frame boundary, and a parked program reaches none". True, and about the wrong thing — the expression needs nothing from the program, and the ones that do need globals the parked process is still holding.

The fix adds a second place a thunk can run rather than loosening what a place has to be. [flan_merged_park] now waits on two flags: [program_asked] leaves the park and runs main, and [program_poll] — set by [Program.wake], which [eval_expr] calls after the delivery — drains the agent's ring and waits again. The thread stays PROGRAM_PARKED throughout, so [:parked t] rides on the reply that carries the value.

Why this is safe without a new concurrency model: while parked there is no concurrency at all. The program's thread is asleep on a condvar, no frame is executing, no global is being written — which is precisely what a frame boundary provides. The break loop is the precedent, a thread servicing the same ring while it is not running frames. Common Lisp answers the same question by giving evaluation a thread of its own (SWANK's [thread-for-evaluation]) and documents the resulting race as the programmer's problem; there is no race here to document.

Merged-build only, and for the reason re-run is: [liveness_of] maps a finished child to Gone under –two-process, so there is no parked thread to wake.

What became answerable with it: a thunk can now stop in the break loop on the parked thread, so backtrace, break, restart, restart-at, abort, locals/inspect and globals stop refusing on the state alone and refuse on [parked_break] instead — a paused expression against the park would otherwise be unresumable. Refused still, because their cause is not the park: nothing else.

The headline complaint is verified fixed on sand.flan

Window opened, closed, the daemon reported parked, (:op "rerun") returned ok, and xdotool found a live window from the second run.

The earlier claim that [flan dev sand.flan] failed with "unknown function begin-drawing" was true only on the stale base the work started from, and was retracted after a re-test. Nothing to chase.

Evening of 2026-09-17 — the review, and four lanes off it

docs/REVIEW-production-readiness.md is the production-readiness review, written to be implemented from. Item 4 (arena EDN) merged green before it was written, so the FIX list proper is six of seven done and one in flight.

Four agent lanes are running off the review, each in its own worktree:

• Tier 1 + the runtime half of Tier 4: overflow guards, map removal (Odin's backward-shift), the registry race, the scratch buffer, Addr-on-Option, the dev-runtime aborts. One lane because they share runtime/*.c.
• Tier 3: clock, math, getenv, basic file ops. Appends to flan_rt.c in its own section so the merge with the lane above stays clean.
• Tier 4 without the runtime: CLI error arms, flan run flags and -O, CI, the stale DISCUSS.md x86 table, README's missing subcommands and env-var table.
• The JS backend's first slice, per docs/DISCUSS.md §5's settled decisions: #_ first, then one function under node, then the corpus with a MATCH/DIFFER/REFUSED survey. New reference clones for it are recorded in docs/REFERENCES.md ("Compiling to JavaScript").

Tier 2 (install and shipping) was explicitly passed over. Package visibility is skipped in every lane — it needs a syntax decision from the author.

All four lanes merged, end of 2026-09-17 evening

Tier 1 (runtime correctness + the runtime strays of Tier 4), Tier 3 (clock, libm, getenv, file verbs), Tier 4 (CLI arms, flags, CI, docs) and the JS dialect's first slice are all on dev-loop. Verified together: dune test –force 232/0, @x86 116 MATCH / 0 DIFFER, @js 0 DIFFER, @sanitize clean.

Left for the author, recorded where each lives:

• Package visibility needs a syntax decision (review Tier 4 item 5).
• The v->gen word: spec-memory.md mandates it, nothing reads it; delete or implement is a spec amendment (BUILT.md records the two options).
• sand.flan:167 still holds the refused defconst experiment; the diagnostic now prints in full and names the fix.
• Tier 2 (install and shipping) deliberately not started.

The repeal, 2026-09-18

The ownership flow analysis is removed: the per-function dead set, the borrow flag, the loop-iteration diff, and the borrowed-never-moved rule for globals. Use-after-move and double-free are no longer compile errors. What stands: move-only as a type property (assignment hands over the header, clone is the only copy), the struct/union/pool ownership rules, defconst-vs-defvar for move-only globals, defer, all allocator capabilities, and the dev build's generation checks — now the primary net, which is the Odin position the memory design came from.

Decided after the bug hunt put four of its ten lanes inside this machinery. An unsound checker is worse than none, because it is believed. The door back is spec-memory.md's provenance pass: removal widened acceptance without changing any accepted program's meaning, so a stricter pass can return additively. spec-memory.md "The repeal" is the amendment; BUILT.md and NEXT.md are annotated at their live claims.

Two of the day's fix lanes were cancelled with this (borrowed-flag, region element); the while-condition fix merged in the morning is deleted again by the repeal, and its pin with it.

The second round, 2026-09-18 — Pool, move-only, and the gen word

Ordered by the author after the ownership repeal, on the same argument: the Odin position, full stop.

• Pool and (Handle T) are gone — types, checker arms, runtime section, fixtures. Two containers are enough; a slab with generational handles is a library over a Vec when a program wants one.
• The move-only concept is gone: everything copies as its header, copyable? left the predicate list (four remain), and the struct/defdata/defunion owning-field refusals are lifted. The region rule stands untouched — a container of owning elements is still built against a region and released by one free-all.
• The gen word left both container headers (read by nothing since it was written). A Vec is ptr len cap allocator epoch; the epoch trap stays.
• Container globals keep both declaration rules, reworded: they start zeroed (a global initialiser is a compile-time constant, and a container's only constant is the empty one), and a defconst container is refused since a constant is not an assignable place. sand.flan's experiment line would now be refused with the reworded sentence.

Everything verified together: dune test –force 232/0 with zero suite FAILs, @x86 122 MATCH / 0 DIFFER, @sanitize clean, and the whole-repo check sweep against the parent differs only where it should: the two negative fixtures now accepted (vec-in-struct, the clause-less generics corpus), the two pool fixtures deleted.

End of 2026-09-18 — the hunt closed out

Ten bug lanes and three demolitions, all on dev-loop and verified together: 232 checks / 0 failures, @x86 122 MATCH / 0 DIFFER, @sanitize clean.

• Fixed: while-condition move (then repealed with the machinery), defenum i32 range, the Emacs client's framing/poll/point-min/quit bugs, the session NULL-cell rollback, the stdout pipe drains, x86 shift masking, the reversed slice traps in every build, NaN prints unsigned, the registry answers honestly under churn, and reg at's stopped-only race.
• Removed by decision: ownership flow tracking, Pool and Handle, the move-only concept, the v->gen word. spec-memory.md carries the repeal.
• Still recorded, not scheduled: trap paths that bypass the break loop, parked orphans outliving dead daemons, emit.ml's transient test and globals, map-grow's stale quote, x86's slice-from-ptr sentence, the float->int UB divergence, the narrowed-buffer C-x C-e quirk, and the JS backend's items (deprioritised).

Late 2026-09-18 — the last two lanes

• Six trap paths park instead of killing the session — merged (e6d85c8). All six park for inspection; transfer-fail and restart-unarmed refuse the resume with the trap's sentence. New flan_trap_hook beside flan_break_hook, whose contract could not carry these. Standalone builds die as before.
• Parked orphans exiting with their daemon — merged. PDEATHSIG on the two-process child, armed in the agent, with a spawn-SIGKILL-reap test. Found in passing: the eight orphans split 4/4 — four are MERGED daemons whose editor vanished, a separate defect (accept_loop has no client liveness), recorded here. The eight were killed by hand on 2026-09-18.
• That second defect is now fixed too. accept_loop keeps a grace since the last client let go of the socket, and ends the session when it runs out. The connection is per session and not per request — Emacs holds one make-network-process for the whole of flan-dev and every deliberate teardown sends [close] first — so an editor left open and idle is an editor still attached, and the clock cannot run under it. Armed only after a first client has connected, so a headless daemon waiting for one is untouched. Two graces: 5 minutes parked, 30 minutes live, because a parked program is invisible (which is why four piled up) and a live one is a window somebody may be watching. FLAN_DEV_CLIENT_GRACE overrides in seconds; non-positive turns it off. Six unit rows on the decision and one end-to-end daemon whose client drops without a [close].

The dynamic half of item 4, finished

Item 4 above is the complaint at line 23: the edn module should read into a struct and answer a dynamic value when no type is given. The dynamic half is now the package's rather than a test program's.

• [#{}] is read, not refused. The tokenizer's stated reason ("needs a hash set to even represent") was a claim about a reader, and a tokenizer represents nothing; [#{] pushes [}] on the same balance stack [{] does, one new token kind, and [err-set] is gone rather than kept with a new message.
• [vendor/edn/read.flan] holds the [Value] data type and [(edn/read bytes)], which answers an [(Option Value)] against the calling convention's allocator. A set is [Value.Set] holding a deduplicated [(Vec Value)] — [(Map Value bool)] does not typecheck, because [keyable] refuses a key holding a Vec or a Map, and restricting set elements to keyable Values would refuse [#{[0 0] [1 0]}], which is the file this was built for.
• A Value COPIES every string into the allocator; a Token stays a view. The two layers diverge deliberately and both headers say so. A view handed out of the function that owns the buffer is a dangling pointer no free-all would even take back.
• Needed one compiler change to be possible at all: an imported [defdata] was a refusal in load.ml ("not implemented yet, milestone 4"). It is a rename of the type's name plus the [Type.Case] half of a constructor symbol; a match pattern resolves its case against the scrutinee's type and never needed one.

Still not built, still item 9 on docs/PORTING.md's list: [(read-edn T bytes)], the typed half. It wants a compile-time walk over a struct's fields and there is no run-time type information to do it with at run time.

Session close, 2026-09-20 — dynamic-first M1 landed

Merged on dev-loop, all green (dune test –force 0 failures, @x86 130 match, @sanitize clean): the dyn type (unannotated defn params/returns are dyn, NaN-boxed runtime, mark-sweep GC, –no-gc refuses residual dyn by location), the provider macros (defedn/defjson off macro-slurp; NEXT.md item 9 closed), computed global initialisers on both backends, x86 frame pushes (inspector works under the x86 default), the !-suffix retirement, and the flan-dev→flan rename. typed-flan branch freezes the static language pre-dyn.

Still in flight, worktree branches to merge when they report

• x86 dyn lowering + the x86/LLVM invoke-restart divergence (one lane, two commits) — the author is waiting on this one to start playing.
• The writable inspector (SLY-style set + editable render buffer).
• docs/SPIKE-DUPLICITY.md, the dyn/native boundary audit (report only).

Open, author's call

• sand.flan holds uncommitted WIP: a defvar initialiser reading game-data.edn at startup aborts the headless import (unhandled FileError at the test's CWD). Options on the table: embed, handler-bind fallback, or harness dep.
• Signature pairing's cold-rebuild edge: a later type definition can silently re-pair an unannotated parameter vector; a changed-pairing warning between compiles was proposed and not yet queued.

M2 queue, decided with the author 2026-09-20 — in order

1. dyn maps + keywords (interned, O(1) equality). Retires edn/Value after.
2. Per-type descriptors: dyn fields in structs/conditions become markable.
3. Typed containers into dyn as VIEWS — one descriptor word in the box, reads box the element, writes tag-check. Rides on 2. No copies. DECIDED 2026-09-19: the descriptor is its own thing, not the slice type reused. Two reasons. A dyn value is a single word and a slice is two, so reusing the slice buys no allocation back — the descriptor goes on the heap either way. And a slice carries where and how many but not of what, which is the one fact dyn needs, since boxing a read and tag-checking a write both require the element type. The descriptor is therefore pointer, length, and element type: a slice plus the piece a slice is missing. Left open until the lane is built: whether the descriptor points at the container or is a fattened slice stored beside it. That only bites if the container can grow and move, which would leave a push through dyn holding a stale pointer. — LANDED. Settled: a Vec view holds the address of the Vec's own header and reads its ptr/len live on every operation, so a push that reallocates cannot go stale — there is no snapshot to invalidate, because flan_vec_grow overwrites that same header in place. A slice and a fixed array cannot grow, so a flat view snapshots pointer and length once, which is sound for both and is not the weaker half of an asymmetric choice — pointing a flat view at its own value's slot instead would be worse, since a slot's lifetime is not the slice's. The element set is i64, f64 and bool only: a string element's dyn form is a pointer into the collector's heap, and a typed container's storage is memory the collector never scans, so a wider set would let a write plant a live reference nothing traces. (Vec string) and (Map K V) keep the refusal [box] already gave every container. Both backends, runtime/flan_dyn.c and .h, checker tests, an acceptance row per backend, and a survey program (dyn-view.flan) proving the view against both a growing Vec and a fixed array/slice, plus its own two trap modes. REVIEW, 2026-09-20: relocation was proved sound but relocation was not the hazard that mattered — a view can outlive the frame its Vec header sits in, which nothing could reach before this lane because [box] refused every container outright. Three routes, all newly constructible, all stack-use-after-return: returning a view, stashing one in a dyn global, leaving one behind across a condition transfer. AUTHOR'S RULE: on the dynamic side Flan aims where Clojure and Common Lisp are — holding a value should not hand you garbage — so a container may cross into dyn as a view only when its own storage is permanent — a global's. [permanent_root] in check.ml decides it: a global, a field of one, an element of a permanent ARRAY (an element of a slice is NOT — a slice holds only ptr+len, and what they point at can be a frame already gone; the [At] arm steps every index of a multi-index [(at g i j)] the way [indexed] does and demands an array at each level, because the whole index list rides on one node and reading the target's type alone settled level zero only), or a slice cut directly from one at the call (the trace is lost the moment it is bound to a name first). Everything else — a local, a parameter, a temporary, anything behind a (Ptr T) — is refused by name, pointing at the defvar spelling that works. A heap-held header is not expressible soundly at this milestone for a structural reason rather than a missing feature: a (Ptr (Vec i64)) taken off a heap block and one taken off a local are the same type, so admitting a Ptr as permanent would readmit the exact hole this closes. The rule is a narrowing, not a proof, and flan_dyn.h states the property that actually holds: a view is exactly as stale-safe as the thing it is a view of, no more and no less. A global [i64] whose data was cut from a frame that has since returned still passes [permanent_root] and still reads a dead frame. What the guard closes is the routes the checker can see, not every route. An arena-held header is not a separate case for [permanent_root] — an arena changes where a Vec's elements live, never where its own header (the binding) lives, so the cases above already decide it — but that is coverage of the HEADER's lifetime only, and releasing the arena under a live view is a separate hazard handled at RUN time, not here. [view_vec_check] in flan_dyn.c is what handles it: a Vec records its allocator's epoch and every view operation re-checks it, so (free-all ar) with a live view over an arena-grown global Vec traps cleanly and by name at the next read — verified. (arena-destroy ar) is the gap: it frees the allocator block itself, so the epoch [view_vec_check] goes to read is freed memory. Run plainly it happens to trap anyway — the freed block still held the bumped epoch — but that is the allocator not having reused it yet, not a check that held; under ASan the same program is a heap-use-after-free in [view_vec_check] before it decides anything. Left standing rather than fixed with this lane: the typed side has it identically in [flan_vec_check], flan_rt.c, which reads the same freed allocator's epoch, so it is a repo-level question about arena-destroy's ordering and not about views. Three more, all in the runtime rather than the boundary: [view_vec_check] recursed into itself rendering the very view it had just declared unsafe to read (fixed by never rendering it — the sentence names the epochs and nothing else); [dyn_equal]'s VEC arm read raw [len]/[items] regardless of kind, so two views with different contents compared equal and a map keyed by a view collided with every other view (fixed with view-aware length/element readers, [vecish_len]/[vecish_at]); and the three restatements of flan_vec's layout (flan_rt.c, flan_dyn.c, dyn_ops.c) had nothing tying them together despite a comment's claim that they did — a [layout] probe on each, compared field by field in dyn_ops.c's new "layout" mode, makes a disagreement a FAIL line instead of a silent corruption.
4. nil: arrives with maps. nil <-> None at (Option T) boundaries, trap at bare T, (Some nil) unconstructible. — LANDED, 3c1fb1b. The bare-T trap is split: a literal nil the checker can see is refused at compile time, in expect itself; a dyn only known nil at run time still reaches flan_dyn_need_i64's existing trap unchanged. (Option (Option T)) does not cross either direction, same ambiguity as (Some nil). (Option dyn) is a legal type the boundary code already treats correctly — the payload is the identity, box and unbox both — but not yet a storable value anywhere: the per-type-descriptor pass (item 2) refuses it the way it refuses (Vec dyn), and item 4 does not lift that gate.
5. Typed = and != grow strings: bytewise, length + same-pointer fast paths, both backends, one survey program. Ordering stays refused. — LANDED, daed039
6. defclass = named dyn map + shape tag; CLOS class dispatch AND Clojure-style arbitrary dispatch functions. After 1.

7. dyn if: truthiness (nil/false are false, all else true). Typed stays strict bool. — LANDED, 264765a

   Reaches when, cond, if's own condition, and's condition, or's condition, not and while for free or by hand, all through one funnel in check.ml (check_truthy). Two things fell out of it that nobody had decided going in, one fixed on review and one left as the author's call:

   • Neither and nor or handed back the operand that decided it. Clojure's rule is that both do; each answered a bare bool sentinel on its deciding path instead. and's "false" sat in the else arm, so check_if typed the real branch first and boxed the sentinel to match: an all-truthy and did carry its last dyn operand through, but a falsey one answered false where Clojure answers the falsey operand — (and (box 1) (box nil) x) printed false, not nil. or's "true" sat in the then arm, the one check_if types first, so the sentinel decided the whole expression's type and a later non-bool dyn answer hit the strict bool boundary and trapped: (or nil "x"), the canonical (or x default) idiom, crashed rather than answering "x". FIXED for or in ad0f1fb and for and in this pass: both now bind the test to a temp and answer the temp on the deciding path, Clojure's own expansion — (let [t a] (if t t b)) for or and (let [t a] (if t b t)) for and — evaluating each test exactly once. The asymmetry between the two forms is fully closed; the survey program (test/programs/dyn-if-truthy.flan) pins both, short-circuit and single-evaluation included, and test_flan.ml pins both desugarings down to the bound name and the bound value. Two things came with that pass. The temp binding and the if it feeds now carry the operand's loc rather than the whole form's, which ad0f1fb had lost for or: (or (vec-new i32) v) blamed the enclosing form at 3:13 and now points at the operand at 3:18, and and's second operand gained the same precision. And, noted and not acted on: with both arms of the desugared if now holding real values, a dyn operand mixed with a typed bool one makes check_if unify them by the then arm, so a non-bool dyn value on the losing side traps at the strict bool boundary — (or false (box "s")) and (and (box nil) some-bool) both do. Each form used to be safe in exactly one of those directions, because the sentinel it answered was a bool literal that boxed to fit the real branch; neither is now, and they are at least symmetric about it. (and (box nil) some-bool) printing false is the one previously-compiling behaviour this pass changed. Making a bool arm and a dyn arm join as dyn is a check_if question and the author's call, not settled here.
   • A bare keyword condition used to be checked with want:Bool from the start and refused by the keyword arm's enum-or-refuse case: ":kw is an enum member where an enum is expected and a dyn keyword elsewhere, but bool is expected here", there being no enum in play. Checked with no expectation first, as every scrutinee now is, it resolves as the dyn keyword instead, and a dyn keyword is unconditionally truthy — a typed if with a bare keyword condition now compiles and always takes the then branch. The author's call: lispy truthiness wins here, the lost diagnostic is not brought back. Pinned in test_flan.ml so it does not regress by accident.

   Also noted at check_truthy (check.ml) and not acted on: check_truthy's own retry-on-failure, needed to keep a refused literal's or None's message unchanged, re-runs the whole failing subtree rather than only the leaf that needs it, which is exponential in how deep a chain of nested not gets on a program that does not type-check. Moot for anything that compiles; visible only around twenty levels deep, and only the dev daemon's half-typed-form recompiles could ever feel it. A cheaper retry was tried and shelved — it would need to thread want exactly as far as the full retry already does, or it changes which literal further inside a compound condition gets the nicer message, not just the speed.

8. Return slot stays mandatory (dyn or ()) — the parse ambiguity it closes is real; revisit only if it grates. SETTLED 2026-09-19, reconfirmed with the author: both spellings stay legal, () is not collapsing into dyn. No work follows from this one.

All of it dispatches after the x86-dyn lane lands. The struct dyn-field refusal (01e60fa) is the stopgap 2 lifts.

The two models, named 2026-09-19

With a collector in the runtime, the direction has a shorter statement than it used to. The dynamic paths mimic Clojure. The static paths mimic Odin. Both carry a little more ML than either of them does.

That is a tiebreaker, not a slogan. A question on the dyn side that Clojure has already answered takes Clojure's answer unless there is a reason to depart, and the same holds for Odin on the static side. Keywords, maps and nil landed under that reasoning without it being written down yet.

Common Lisp is consulted alongside Clojure on the dynamic side, and on some questions it is the better authority of the two. The condition system is the standing proof: handler-bind, the restarts and invoke-restart are Common Lisp, and Clojure has nothing resembling them. handler-case is the same lineage — Clojure's try/catch is the shape most reached for, but the form being added is Common Lisp's, and it is named for the Lisp rather than the Clojure because it is the unwinding half of a pair whose other half is already CL's.

Where the two disagree, the question is which one the rest of Flan already agrees with. Conditions say Common Lisp. Maps, keywords and nil say Clojure. Neither answer generalises to the other's territory.

The ML share is the part neither model supplies — the type system, the options, the exhaustive matching, and whatever a second ML surface would eventually add if the deferred syntax question ever reopens.

Arithmetic semantics do not fork across the two spaces, decided 2026-09-20

One operator, one meaning, both sides. `/` on integers truncates toward zero and `%` is its remainder, sign following the dividend — LLVM's sdiv/srem, the x86 backend's cqo/idiv, and flan_dyn.c's arith all already agree, and that agreement is now the rule rather than a coincidence. The author's call: this sort of semantics is normalized across the dynamic and static spaces, so the Clojure tiebreaker above does not reach it. Clojure's flooring `mod` (sign of the divisor) is NOT to be added as a dyn-side-only behavior of `%`; if a flooring mod is ever wanted it is a second, separately named operation available to both spaces, the way Common Lisp keeps `rem` and `mod` side by side. Division by zero and INT64_MIN / -1 trap identically on both sides, and float `%` is fmod on both backends and in dyn.

handler-case, decided 2026-09-19

Flan has handler-bind, which is the resuming handler: it runs where the condition was signalled, with the stack still standing, and carries on by invoking a restart. What it has no spelling for is the other half — unwind, and answer the whole form with a value. Clojure spells that try/catch and reaches for it constantly; the closest thing here is a handler-bind plus a use-value dance that is far heavier than the intent, or a pre-check that races the read it guards.

The gap showed itself when edn/read-file stopped returning an Option. The caller that used to write or-else against a None had nothing left to write, because the missing file now arrives as a FileError condition and the only concise way to answer a condition with a default did not exist. The shape wanted is:

(handler-case (edn/read-file "game-data.edn") [(FileError [c] nil)])

which keeps read-file's decision intact — the caller still says what a missing file means — while costing one form instead of a machine. Until it lands, sand.flan guards the read with file-exists?, which is a stopgap and racy, and should be rewritten the moment this exists.

The JS backend answers string equality wrongly, parked 2026-09-19

Typed = and != grew strings in daed039, and the JS dialect was not taught the case. A string there is a view object and the arm at lib/js.ml:856 compares with =, which asks whether two views are the same object rather than whether their bytes agree. The arm was unreachable for strings until the checker stopped refusing them, so the lane made an existing hole live without touching the file. Equal literals still answer true, because equal literals intern to one view, which is what makes the wrong answer quiet rather than obvious: (= s (string (slice (bytes s) 0 3))) is true natively and false under –target=js.

The author parked it. JS stays deprioritised and the fix is not queued. The option on the table when it is picked up again is a loud refusal in that arm rather than a real implementation, so the dialect says it cannot do this instead of saying something false.

Sweep policy, decided 2026-09-19

A lane runs the fast check and nothing more. `dune test` is the whole of a lane's obligation. It used to be judged by reading the printed output rather than by trusting the exit status, on the theory that some path through the acceptance runner could print a FAIL and still exit 0. That theory did not hold up: test_acceptance.ml is one match on whether clang is on PATH, the wasmtime/raylib/lldb probes inside it are ordinary `if`s that fall through to the same tail rather than branches that leave early, and the tail already turned a nonzero failure count into exit 1 — so did every other test binary's tail, checked the same way. test_acceptance.ml now also carries an `at_exit` guard, but it closes no open gap; it is insurance against a future case leaving past the tail instead of through it. The exit status was already trustworthy and stays that way, so either check does. Running one program directly to capture its real output for an acceptance row is still expected; that is cheap. What a lane may no longer do is sweep.

The x86 survey and the sanitizer sweep run once, after several lanes have landed, and whatever they turn up is dispatched as fixes in a single batch. The reason is arithmetic: a survey walks all 156 programs across three modes, and a lane that touches a handful of them was paying that cost in full to learn nothing about the rest. Paid once for several lanes, the same sweep answers the same question at a fraction of the wall clock. The consequence to accept is that a lane is reviewed on its code rather than on sweep numbers it no longer produces, which is what the review before a merge is for.

handler-case, decided 2026-09-19

Built, both backends, and it needed no backend work at all: it is a handler-bind whose clause invokes a restart the form established around itself, which is spec-conditions.md's one open question about the operator answered in the affirmative. The shape is (handler-case BODY [(T [c] …)]), body first and clauses after, the opposite of handler-bind's order because a handler-bind reads as something put around a body and this one reads as a body with answers hung off it.

Everything the unwinding form needs it inherits. Defers and the with-allocator restore run on the way out because a transfer already runs them for every frame it leaves. The body and every clause agree on one type because §3 already says a restart-case's do, and a clause that disagrees is refused with the same message an if with disagreeing arms gets. A condition no clause lists installs no matching frame and carries on outward untouched. A clause runs at the form, so it sees the establishing function's locals, which a handler-bind clause cannot — that is the whole difference, and it falls out of where a restart clause runs rather than being arranged for.

The one wart, noted and left: the restart the form makes up for itself is on the restart stack like any other, so a break loop entered underneath one lists it. Choosing it there is refused loudly rather than answered wrongly, and hiding it would mean a new field in a frame layout written out in emit.ml, in x86.ml and in flan_rt.c.

Surface syntax discussion, 2026-09-19

The author wants an F#-ish indentation-based ML surface living side by side with s-expressions, not replacing them. The languages that disappear for the author, in the order named: Python first, then Odin, then F#. That ordering is the case for why Flan's own parens might be costing more than they look like they cost.

The architecture agreed if it is ever built: one AST, the existing forms unchanged, and a second reader in front of it. Macros stay usable from either surface, since they operate on the same AST either way. A Nim-style quote-block was floated as the way a macro's own body could be written in the ML syntax rather than in s-expressions, without needing a third representation.

Middle options came up and were set aside rather than chosen. Parinfer stays an editor trick — it never changes the language, only how parens are typed, so it does not touch the actual complaint. Wisp and sweet-expressions (indentation implying the parens) were considered and are closer to a real second surface than Parinfer, but still read as a compromise rather than the ML syntax the author actually wants. A simplified in-paren syntax was also on the table and rejected on the same grounds — it thins the parens without removing them. Rhombus was named as the maximal reference point: whatever a full second surface costs, Rhombus is roughly what it costs to do properly.

Decided: deferred, no spike queued. The author's working hypothesis is that the friction with Clojure may not be the parens at all — it may be immutability, and the discipline of planning a shape ahead of time that comes with it. The plan is to write imperative Flan as it stands and see whether the parens still grate once that variable is gone. Revisit this once that evidence exists.

The x86 backend tracks LLVM -O0, decided 2026-09-20

The ruling, in the author's words: the x86 backend must behave as closely to LLVM at -O0 as possible. A construct LLVM compiles, x86 compiles, and the two must agree on what the program observably does. The backend is allowed to refuse a node it does not lower — that is what X86.Unsupported is for and it is how the survey reports a gap — but a refusal is a bug to be closed, not a position. "LLVM takes this and x86 does not" is by itself a defect report.

What made it a ruling was typed float %. emit.ml's prim arm emits frem for Rem on a float, so (% 7.5 2) compiled under LLVM and printed 1.5; the matching arm in x86.ml had no float Rem case and died at build time with an unlocated internal error, "x86: that operator on f64". Dyn % on floats worked on both backends the whole time — flan_dyn.c's arith implements the fmod identity — so deleting the annotations made the program build again, which is exactly backwards. x86 is the dev loop's default backend, which is what turned a backend gap into a thing the author hit while writing ordinary code.

Fixed by calling the same function LLVM calls. There is no SSE remainder instruction and LLVM does not invent one: a frem that reaches the code generator becomes a call to fmod or fmodf, which objdump shows as a call to the PLT stub — fourteen of them in a build of the probe whose operands come through globals, and none at all in one written with float literals, where the pair is folded to its answer before any call exists. x86.ml now loads the two operands into xmm0 and xmm1 — already the SysV argument registers — and calls fmod or fmodf by width. Agreement is then by construction rather than by a second hand-written identity that would have to get every rounding, every signed zero and every infinity right on its own. Nothing new had to be arranged for the link: the prelude already declares both symbols as fmod-f32 and fmod-f64, and every link passes -lm.

Rem was the only gap. Walking emit.ml's prim arm against x86.ml's: the whole float surface is Add, Sub, Mul, Div, Rem and the six comparisons. x86 had four of the five arithmetic operators and all six comparisons, and the comparisons match LLVM's ordered predicates — oeq and one are built there from a setcc against ucomis plus the setnp that rules out the unordered case, which is what the o in the LLVM predicate means. The bitwise and shift arms are integer-only on both sides. So nothing else was missing.

The aspiration: tests that say x86 still tracks -O0

Wanted, and half of it exists. @x86 (test/dune:239) is already the diff: it builds every program in test/programs, spike/x86 and spike/js twice — once through LLVM, once through –x86 — runs both, and compares stdout, stderr and the exit status. SURVEY_STRICT makes a DIFFER or a by-name refusal a failing build. So a corpus program that exercises a construct is already a test that the two backends agree about it, and the float % cases added to math3.flan are in that set by being in test/programs.

What @x86 does not do is pin the LLVM side at -O0. It builds both sides at the default -O2, so a construct LLVM folds at compile time — a % over two float literals is one: that build contains no fmod call — is compared as a constant against the x86 backend's actual lowering. The float % block in math3.flan goes through globals for that reason, the same reason arith.flan gives for its own. Two things would close the rest of the gap: an -O0 pass of the sweep, so the LLVM side emits the calls and branches rather than the answers — the script already has SURVEY_FLAGS, which hands the same extra flags to both sides, and both sides do accept -O0 — and something that walks the two prim match arms mechanically rather than relying on somebody reading them side by side, which is how this gap survived. Neither is queued.