From 256007e5fd6a262ca5e5ee4851a9854e542e979a Mon Sep 17 00:00:00 2001
From: "Jonathan D.A. Jewell" <6759885+hyperpolymath@users.noreply.github.com>
Date: Mon, 21 Sep 2026 10:35:24 +0000
Subject: [PATCH] feat(esm): retire --deno-esm; Bun-ESM is the only JS-host ESM
 target
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

--deno-esm / -o *.deno.js is a hard error (E0826) pointing at --bun-esm.
codegen_deno now emits the Bun host. The historical codegen-deno corpus
compiles to .bun.js. Aspirational StartupError fixtures use real syntax
(use Console/Dom, tuple-list attrs, #{…} records).

Refs #56
---
 .github/workflows/ci.yml                      |   8 +--
 .gitignore                                    |   1 +
 CHANGELOG.adoc                                |   9 +++
 bin/main.ml                                   |  54 ++++--------------
 docs/CAPABILITY-MATRIX.adoc                   |  23 ++++----
 docs/ECOSYSTEM.adoc                           |   4 +-
 docs/EFFECTS-IMPLEMENTATION.adoc              |  12 ++++
 docs/STDLIB-EXTERN-AUDIT.adoc                 |   4 +-
 docs/bindings-roadmap.adoc                    |   2 +-
 docs/guides/bun-esm-migration.adoc            |  18 ++++--
 lib/codegen_deno.ml                           |  13 +++--
 stdlib/Console.affine                         |   5 +-
 stdlib/Deno.affine                            |  10 ++--
 stdlib/Dom.affine                             |   6 +-
 .../codegen-deno/aggregate_smoke.harness.mjs  |   2 +-
 .../codegen-deno/bytes_binary_io.harness.mjs  |   2 +-
 tests/codegen-deno/canvas_smoke.harness.mjs   |   2 +-
 tests/codegen-deno/class_basic.harness.mjs    |   2 +-
 tests/codegen-deno/control_flow.harness.mjs   |   2 +-
 tests/codegen-deno/deno_scripting.harness.mjs |   2 +-
 .../deno_scripting_part2.harness.mjs          |   2 +-
 .../codegen-deno/deno_string_fmt.harness.mjs  |   2 +-
 tests/codegen-deno/dom_startup_error.affine   |  14 +++++
 .../dom_startup_error.harness.mjs             |  21 +++++++
 .../codegen-deno/dom_window_smoke.harness.mjs |   2 +-
 tests/codegen-deno/encoding_smoke.harness.mjs | Bin 3278 -> 3277 bytes
 tests/codegen-deno/http_fetch.harness.mjs     |   2 +-
 tests/codegen-deno/int_div.harness.mjs        |   2 +-
 tests/codegen-deno/ipc_smoke.harness.mjs      |   2 +-
 .../loop_break_continue.harness.mjs           |   2 +-
 tests/codegen-deno/match_enum.harness.mjs     |   2 +-
 tests/codegen-deno/motion_smoke.harness.mjs   |   2 +-
 tests/codegen-deno/non_ascii.harness.mjs      |   4 +-
 tests/codegen-deno/pixi_smoke.harness.mjs     |   2 +-
 .../codegen-deno/pixisound_smoke.harness.mjs  |   2 +-
 tests/codegen-deno/pixiui_smoke.harness.mjs   |   2 +-
 tests/codegen-deno/random_smoke.harness.mjs   |   2 +-
 tests/codegen-deno/ref_fields.harness.mjs     |   2 +-
 .../sqlite_introspect_bulk.harness.mjs        |   2 +-
 .../codegen-deno/sqlite_prepared.harness.mjs  |   2 +-
 tests/codegen-deno/sqlite_smoke.harness.mjs   |   2 +-
 tests/codegen-deno/string_lex_cmp.harness.mjs |   2 +-
 tests/codegen-deno/string_prims.harness.mjs   |   2 +-
 .../transaction_smoke.harness.mjs             |   2 +-
 tests/codegen-deno/wasm_call.harness.mjs      |   2 +-
 .../wasm_exports_demo.harness.mjs             |   2 +-
 .../wasm_wasi_instance.harness.mjs            |   2 +-
 tests/codegen/dom_pilot_startup_error.affine  |  31 ++++++++++
 .../codegen/test_dom_pilot_startup_error.mjs  |  12 ++++
 tools/run_codegen_bun_tests.sh                |  22 +++----
 tools/run_codegen_deno_tests.sh               |  23 ++++----
 51 files changed, 218 insertions(+), 136 deletions(-)
 create mode 100644 tests/codegen-deno/dom_startup_error.affine
 create mode 100644 tests/codegen-deno/dom_startup_error.harness.mjs
 create mode 100644 tests/codegen/dom_pilot_startup_error.affine
 create mode 100644 tests/codegen/test_dom_pilot_startup_error.mjs

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 512c85ef..578b151c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -89,10 +89,10 @@ jobs:
         run: opam exec -- dune runtest
       - name: Run codegen WASM tests
         run: opam exec -- ./tools/run_codegen_wasm_tests.sh
-      - name: Run codegen Deno-ESM tests (issue #122)
-        # Compiles tests/codegen-deno/*.affine with the --deno-esm backend
-        # and runs the *.harness.mjs under Node (CI has Node 20, not Deno;
-        # the Phase 1 fixtures are pure logic so Node ESM exercises them).
+      - name: Run codegen Bun-ESM tests (historical codegen-deno corpus)
+        # Compiles tests/codegen-deno/*.affine with the --bun-esm backend
+        # and runs the *.harness.mjs under Node (CI has Node 20; these
+        # fixtures mock host objects and do not need the Bun binary).
         run: opam exec -- ./tools/run_codegen_deno_tests.sh
       - name: Run native Bun-ESM tests (issue #734)
         run: opam exec -- ./tools/run_codegen_bun_tests.sh
diff --git a/.gitignore b/.gitignore
index 0f632882..b1445fa0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -100,6 +100,7 @@ bisect*.coverage
 # issue #122: generated Deno-ESM regression outputs (compiled from the
 # committed *.affine fixtures by tools/run_codegen_deno_tests.sh).
 /tests/codegen-deno/*.deno.js
+/tests/codegen-deno/*.bun.js
 # Issue #734: generated native Bun-ESM acceptance outputs.
 /tests/codegen-bun/*.bun.js
 /tests/codegen-bun/backend-conflict.json
diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index ad4aa419..6cbf3377 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -15,8 +15,17 @@ https://semver.org/spec/v2.0.0.html[Semantic Versioning].
 
 === [Unreleased]
 
+==== Removed
+
+* `--deno-esm` / `-o FILE.deno.js` is a hard error (E0826). Bun-ESM
+(`--bun-esm` / `.bun.js`) is the only JS-host ESM target. The flag is
+kept so existing scripts fail loudly (Refs #56)
+
 ==== Added
 
+* Aspirational idaptik StartupError fixture compiles with real syntax
+(`use Console::{log}`, `use Dom::{…}`, tuple-list attrs and
+`#{ bg: … }` records) on `--bun-esm` (Refs #56)
 * feat(stdlib): Aggregate.affine — SQL group-by + aggregation primitives
 — db-theory #3 (7 externs) (PR #527)
 * feat(stdlib): Transaction.affine — affine-bounded write-set isolation
diff --git a/bin/main.ml b/bin/main.ml
index 6a6e2c62..d491c8b2 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -492,10 +492,8 @@ let repl_cmd_fn () =
 let compile_file face json wasm_gc vscode_ext vscode_adapter vscode_no_lc
     deno_esm bun_esm target path output =
   let face = resolve_face ~quiet:json face path in
-  let is_deno = deno_esm || Filename.check_suffix output ".deno.js" in
-  let is_bun = bun_esm || Filename.check_suffix output ".bun.js" in
-  if is_deno && is_bun then
-    let message = "--deno-esm and --bun-esm are mutually exclusive" in
+  if deno_esm || Filename.check_suffix output ".deno.js" then
+    let message = "Deno-ESM was removed; use --bun-esm (and a .bun.js output path)" in
     if json then
       json_finish [{ Affinescript.Json_output.severity = Error;
                      code = "E0826"; message;
@@ -536,10 +534,9 @@ let compile_file face json wasm_gc vscode_ext vscode_adapter vscode_no_lc
                use the original [prog] because they handle imports natively
                via Codegen.gen_imports / the import section. *)
             let flat_prog = Affinescript.Module_loader.flatten_imports loader prog in
-            let is_deno = deno_esm || Filename.check_suffix output ".deno.js" in
             let is_bun = bun_esm || Filename.check_suffix output ".bun.js" in
             let is_julia = Filename.check_suffix output ".jl" in
-            let is_js = (not is_deno) && (not is_bun) && Filename.check_suffix output ".js" in
+            let is_js = (not is_bun) && Filename.check_suffix output ".js" in
             let is_c = Filename.check_suffix output ".c" in
             let is_wgsl = Filename.check_suffix output ".wgsl" in
             let is_faust = Filename.check_suffix output ".dsp" in
@@ -570,16 +567,6 @@ let compile_file face json wasm_gc vscode_ext vscode_adapter vscode_no_lc
                 let oc = open_out_bin output in
                 output_string oc esm_code;
                 close_out oc
-            end else if is_deno then begin
-              match Affinescript.Codegen_deno.codegen_deno flat_prog resolve_ctx.symbols with
-              | Error msg ->
-                add { severity = Error; code = "E0824";
-                      message = Printf.sprintf "Deno-ESM codegen error: %s" msg;
-                      span = Affinescript.Span.dummy; help = None; labels = [] }
-              | Ok esm_code ->
-                let oc = open_out_bin output in
-                output_string oc esm_code;
-                close_out oc
             end else if is_julia then begin
               match Affinescript.Julia_codegen.codegen_julia flat_prog resolve_ctx.symbols with
               | Error msg ->
@@ -779,10 +766,9 @@ let compile_file face json wasm_gc vscode_ext vscode_adapter vscode_no_lc
                cross-module imports for backends that don't have native
                module-system support. Wasm/Wasm-GC keep the original [prog]. *)
             let flat_prog = Affinescript.Module_loader.flatten_imports loader prog in
-            let is_deno = deno_esm || Filename.check_suffix output ".deno.js" in
             let is_bun = bun_esm || Filename.check_suffix output ".bun.js" in
             let is_julia = Filename.check_suffix output ".jl" in
-            let is_js = (not is_deno) && (not is_bun) && Filename.check_suffix output ".js" in
+            let is_js = (not is_bun) && Filename.check_suffix output ".js" in
             let is_c = Filename.check_suffix output ".c" in
             let is_wgsl = Filename.check_suffix output ".wgsl" in
             let is_faust = Filename.check_suffix output ".dsp" in
@@ -814,17 +800,6 @@ let compile_file face json wasm_gc vscode_ext vscode_adapter vscode_no_lc
                 close_out oc;
                 Format.printf "Compiled %s -> %s (Bun-ESM)@." path output;
                 `Ok ())
-            else if is_deno then
-              (match Affinescript.Codegen_deno.codegen_deno flat_prog resolve_ctx.symbols with
-              | Error e ->
-                Format.eprintf "@[<v>Deno-ESM codegen error: %s@]@." e;
-                `Error (false, "Deno-ESM codegen error")
-              | Ok esm_code ->
-                let oc = open_out output in
-                output_string oc esm_code;
-                close_out oc;
-                Format.printf "Compiled %s -> %s (Deno-ESM)@." path output;
-                `Ok ())
             else if is_julia then
               (match Affinescript.Julia_codegen.codegen_julia flat_prog resolve_ctx.symbols with
               | Error e ->
@@ -1280,28 +1255,21 @@ let vscode_no_lc_arg =
           dependency for extensions that ship no language client; the \
           wiring passes null in its place.")
 
-(* Issue #122: --deno-esm. Selects the direct AST -> ES-module backend
-   ({!Affinescript.Codegen_deno}) regardless of output extension, so a
-   drop-in `.js` ES module can be produced (e.g. `-o src/storage.js
-   --deno-esm`). A `.deno.js` output extension also routes here without
-   the flag, as a convenience for the test corpus / ad-hoc use. *)
+(* --deno-esm was issue #122. Retired: the ESM host is Bun (--bun-esm).
+   The flag is kept so existing scripts get a clear error instead of
+   Cmdliner unknown-option. *)
 let deno_esm_arg =
   Arg.(value & flag & info ["deno-esm"]
-    ~doc:"Emit a standalone Deno/Node ES module directly from the AST \
-          (issue #122): `export class` for struct+impl, `export` for \
-          public fns/consts, and `extern fn` lowered to direct host \
-          calls (Deno.*Sync / JSON / WebAssembly). No wasm, no require, \
-          no handle table — the output is a drop-in importable ESM. A \
-          `.deno.js` output extension selects this backend implicitly.")
+    ~doc:"REMOVED. Deno-ESM is gone; use $(b,--bun-esm) / a `.bun.js` \
+          output path. Passing this flag (or `-o *.deno.js`) is an error.")
 
 let bun_esm_arg =
   Arg.(value & flag & info ["bun-esm"]
     ~doc:"Emit a standalone Bun-native ES module directly from the AST: \
           public declarations are exported and host operations use Bun's \
           Node-compatible synchronous APIs. The emitted module contains no \
-          legacy-runtime shim. A `.bun.js` output extension selects this \
-          backend implicitly. This option is mutually exclusive with \
-          `--deno-esm`.")
+          Deno runtime shim. A `.bun.js` output extension selects this \
+          backend implicitly.")
 
 (** Shared --face flag: select the parser surface-syntax face. *)
 let face_arg =
diff --git a/docs/CAPABILITY-MATRIX.adoc b/docs/CAPABILITY-MATRIX.adoc
index 9986c6d8..e77ed4ab 100644
--- a/docs/CAPABILITY-MATRIX.adoc
+++ b/docs/CAPABILITY-MATRIX.adoc
@@ -196,16 +196,19 @@ Formal spec: link:specs/TYPED-WASM-INTERFACE.adoc[specs/TYPED-WASM-INTERFACE.ado
 Widening roadmap (L1–6, L14–16, multi-producer ABI): link:specs/TYPED-WASM-ROADMAP.adoc[specs/TYPED-WASM-ROADMAP.adoc].
 Producer-side; target spec is the separate `hyperpolymath/typed-wasm` repo.
 
-|Deno-ESM |works |Direct AST→ES-module transpiler (`lib/codegen_deno.ml`),
-`--deno-esm` / `.deno.js`. Shipped + consumer-verified (ubicity).
-
-|Bun-ESM |works |Host-profiled direct AST→ES-module transpiler,
-`--bun-esm` / `.bun.js`. Public declarations remain importable ESM; filesystem,
-argument, and process operations lower through Bun's synchronous
-Node-compatibility surface. Host operations are resolved lazily so a generated
-module that only uses browser-provided externs remains browser-importable. CI
-compiles, checks for legacy-runtime leakage, parses, and executes filesystem,
-byte, argument, export, and missing-path controls under Bun.
+|Deno-ESM |retired |`--deno-esm` / `-o FILE.deno.js` is a hard error (E0826).
+The JS-host ESM target is Bun-ESM. The flag is kept so existing scripts fail
+loudly instead of becoming an unknown option.
+
+|Bun-ESM |works |Direct AST→ES-module transpiler (`lib/codegen_deno.ml`,
+`codegen_bun`), `--bun-esm` / `.bun.js`. Public declarations remain importable
+ESM; filesystem, argument, and process operations lower through Bun's
+synchronous Node-compatibility surface. Host operations are resolved lazily so
+a generated module that only uses browser-provided externs remains
+browser-importable. CI compiles, checks for legacy-runtime leakage, parses,
+and executes filesystem, byte, argument, export, and missing-path controls
+under Bun. `tools/run_codegen_deno_tests.sh` (historical name) compiles
+`tests/codegen-deno/` with `--bun-esm`.
 Migration and host-contract details:
 link:guides/bun-esm-migration.adoc[guides/bun-esm-migration.adoc].
 
diff --git a/docs/ECOSYSTEM.adoc b/docs/ECOSYSTEM.adoc
index 19bce1b3..2be9f4b4 100644
--- a/docs/ECOSYSTEM.adoc
+++ b/docs/ECOSYSTEM.adoc
@@ -168,8 +168,8 @@ surface.
 
 |`affinescript-vite` |scaffold |Build-tool integration shell.
 
-|`affinescript-deno-test` |works |Smoke-test harness used by the Deno-ESM
-target.
+|`affinescript-deno-test` |historical |Smoke-test harness from the retired
+Deno-ESM target. JS-host ESM is Bun-ESM (`--bun-esm`).
 
 |`affinescript-tea` |runtime |INT-07 (#182): real host-side TEA runtime
 + run loop (`TeaApp`: load/init/dispatch/model/setScreen/run,
diff --git a/docs/EFFECTS-IMPLEMENTATION.adoc b/docs/EFFECTS-IMPLEMENTATION.adoc
index 3590872c..eeede5ad 100644
--- a/docs/EFFECTS-IMPLEMENTATION.adoc
+++ b/docs/EFFECTS-IMPLEMENTATION.adoc
@@ -78,6 +78,18 @@ type eval_error =
 Handler evaluation catches `PerformEffect`, selects a matching arm, and
 evaluates the arm body in the handler context.
 
+== JS-host ESM (Bun) — Canvas-style erasure
+
+Host FFI on `--bun-esm` does **not** require `/ IO` (or `{IO}`) effect
+rows. `stdlib/Canvas.affine`, `stdlib/Dom.affine`, and
+`stdlib/Console.affine` declare ordinary `extern fn` / wrappers; the
+direct-ESM emitter lowers them to host calls and erases effect
+declarations (`// effect declaration (erased)`). Declared `/ Async` rows
+are the exception: they compile to `async function` so `await fetch` is
+legal JS. Algebraic `handle { ... }` is a compile error on this backend
+(Refs #555). This is the AOT-safe contract for the #56 remainder — not
+a second effect system.
+
 == Not Yet Complete
 
 [arabic]
diff --git a/docs/STDLIB-EXTERN-AUDIT.adoc b/docs/STDLIB-EXTERN-AUDIT.adoc
index 8d5138b3..69e0ff93 100644
--- a/docs/STDLIB-EXTERN-AUDIT.adoc
+++ b/docs/STDLIB-EXTERN-AUDIT.adoc
@@ -70,8 +70,8 @@ producer-side type signature here and a verifier-side contract in
 runtime adapter all green.  `Http.fetch` is the canonical example
 (landed via the #225 CPS line, PR1..PR3d).
 
-|*Adapter-side (Deno-ESM)*
-|Compiles via the `--deno-esm` backend; the `extern` is realised
+|*Adapter-side (JS-host ESM)*
+|Compiles via the `--bun-esm` backend (Deno-ESM retired); the `extern` is realised
 by the emitted ESM importing a JS module.  The "real impl" is the
 adapter shim in `packages/<adapter>/mod.js` (or equivalent).
 |Adapter package exists, the symbol is exported, and a
diff --git a/docs/bindings-roadmap.adoc b/docs/bindings-roadmap.adoc
index c6536568..a042a741 100644
--- a/docs/bindings-roadmap.adoc
+++ b/docs/bindings-roadmap.adoc
@@ -75,7 +75,7 @@ no further significant  → AffineScript work is tractable.
 |*WASM-exports calling pattern* — invoke individual `exports.fn_name(args)` from a `WasmExports` value
 |`●` usable (Option A landed)
 |`stdlib/Deno.affine`
-|`wasmCall(exports: WasmExports, name: String, args: [Float]) -> Float` lowers to `Number(exports[name](...args))` on `--deno-esm`. AS-side surface + docstring example landed in `stdlib/Deno.affine`; round-trip exercised by `tests/codegen-deno/wasm_call.{affine,harness.mjs}` against a hand-built 41-byte wasm module exporting `add(i32, i32) -> i32`. *Option A (generic) — typed per-Zig-fn shims can layer on top per-consumer if needed.* Closes #414 via host-side #422 + AS-side this PR. *Generic export-call shipped #455* (`wasm_export_call(exports, name, args: [WasmValue]) -> WasmValue` + `WasmValue` opaque + `wv_i32`/`wv_i64`/`wv_f32`/`wv_f64` + `wv_as_int`/`wv_as_float`/`wv_kind`); end-to-end demo at `examples/wasm-exports-demo.affine` (#500) with smoke-test `tests/codegen-deno/wasm_exports_demo.{affine,harness.mjs}` exercising all four scalar kinds.
+|`wasmCall(exports: WasmExports, name: String, args: [Float]) -> Float` lowers to `Number(exports[name](...args))` on `--bun-esm`. AS-side surface + docstring example landed in `stdlib/Deno.affine`; round-trip exercised by `tests/codegen-deno/wasm_call.{affine,harness.mjs}` against a hand-built 41-byte wasm module exporting `add(i32, i32) -> i32`. *Option A (generic) — typed per-Zig-fn shims can layer on top per-consumer if needed.* Closes #414 via host-side #422 + AS-side this PR. *Generic export-call shipped #455* (`wasm_export_call(exports, name, args: [WasmValue]) -> WasmValue` + `WasmValue` opaque + `wv_i32`/`wv_i64`/`wv_f32`/`wv_f64` + `wv_as_int`/`wv_as_float`/`wv_kind`); end-to-end demo at `examples/wasm-exports-demo.affine` (#500) with smoke-test `tests/codegen-deno/wasm_exports_demo.{affine,harness.mjs}` exercising all four scalar kinds.
 
 |6
 |*Phoenix Channels / WebSocket* (Socket connect/disconnect, Channel join/leave/push, presence)
diff --git a/docs/guides/bun-esm-migration.adoc b/docs/guides/bun-esm-migration.adoc
index d0f07eaa..1d1f5b8b 100644
--- a/docs/guides/bun-esm-migration.adoc
+++ b/docs/guides/bun-esm-migration.adoc
@@ -54,12 +54,18 @@ The source filename is retained to avoid a high-risk mechanical move in the
 same change as the semantic migration. It does not imply that Bun output passes
 through or embeds the compatibility runtime.
 
-The compatibility flag remains available for existing external consumers. An
-estate migration is complete only when its active workflows, runtime files,
-lockfiles, build commands, generated artefact names, examples, and current
-documentation have moved to Bun. Historical records may retain their original
-runtime names when clearly marked as history; renaming history would make it
-less accurate.
+`--deno-esm` and `-o *.deno.js` are retired: the compiler errors with E0826
+and points at `--bun-esm` / `.bun.js`. The flag is kept so existing scripts
+fail loudly instead of becoming an unknown option. An estate migration is
+complete only when its active workflows, runtime files, lockfiles, build
+commands, generated artefact names, examples, and current documentation have
+moved to Bun. Historical records may retain their original runtime names when
+clearly marked as history; renaming history would make it less accurate.
+
+`affinescript-vite` remains a scaffold (not in this tree). Effect rows such
+as `/ IO` are not required on the JS-host ESM path: host FFI is erased at
+emit the same way Canvas/Dom externs are (see
+link:../EFFECTS-IMPLEMENTATION.adoc[EFFECTS-IMPLEMENTATION.adoc]).
 
 == Verification contract
 
diff --git a/lib/codegen_deno.ml b/lib/codegen_deno.ml
index 1f3a4640..84caf529 100644
--- a/lib/codegen_deno.ml
+++ b/lib/codegen_deno.ml
@@ -1,13 +1,14 @@
 (* SPDX-License-Identifier: MPL-2.0 *)
 (* SPDX-FileCopyrightText: 2026 Jonathan D.A. Jewell *)
 
-(** Deno-ESM Emit Mode (issue #122, Refs #35 #103).
+(** Direct ESM emit (issue #122 origin; Bun-ESM is the only JS-host
+    profile — `--deno-esm` retired, Refs #56).
 
     A *direct* AffineScript-AST → ES-module transpiler. Unlike
     {!Codegen_node} (which wraps a compiled [Wasm.wasm_module] in a CJS
     shim), this backend emits standalone ES2020 module source — no wasm,
     no [require], no handle table — so the output is a drop-in [.js] /
-    [.mjs] ES module a Deno (or Node ESM) consumer can [import] directly.
+    [.mjs] ES module a Bun (or Node ESM) consumer can [import] directly.
 
     Why a direct transpiler and not a wasm-wrapping ESM shim: the
     motivating consumer ([hyperpolymath/ubicity]'s [storage.ts] /
@@ -2109,12 +2110,14 @@ let generate (host : host_profile) (program : program) (symbols : Symbol.t) : st
   if has_main then emit_line ctx "await main();";
   Buffer.contents ctx.output
 
+(* Deno-ESM host profile is retired; the ESM emitter is Bun-only. The
+   name is kept so existing library callers compile. *)
 let codegen_deno (program : program) (symbols : Symbol.t)
   : (string, string) result =
-  try Ok (generate Deno program symbols)
+  try Ok (generate Bun program symbols)
   with
-  | Failure msg -> Error ("Deno-ESM codegen error: " ^ msg)
-  | e           -> Error ("Deno-ESM codegen error: " ^ Printexc.to_string e)
+  | Failure msg -> Error ("Bun-ESM codegen error: " ^ msg)
+  | e           -> Error ("Bun-ESM codegen error: " ^ Printexc.to_string e)
 
 let codegen_bun (program : program) (symbols : Symbol.t)
   : (string, string) result =
diff --git a/stdlib/Console.affine b/stdlib/Console.affine
index 050e8f91..51a9b1dc 100644
--- a/stdlib/Console.affine
+++ b/stdlib/Console.affine
@@ -4,9 +4,10 @@
 // Console.affine — #56-A typed console surface.
 //
 // `println` / `eprintln` already lower to `console.log` / `console.error`
-// on the JS/Deno backends. These wrappers give the pilot's
+// on the JS-host ESM (Bun) backend. These wrappers give the pilot's
 // `Console.log(...)` name a home so migration does not accumulate
-// `%raw` for the four console methods.
+// `%raw` for the four console methods. No `/ IO` row — Canvas-style
+// erasure at emit (see docs/EFFECTS-IMPLEMENTATION.adoc).
 
 module Console;
 
diff --git a/stdlib/Deno.affine b/stdlib/Deno.affine
index b3e6d118..15a6cf8f 100644
--- a/stdlib/Deno.affine
+++ b/stdlib/Deno.affine
@@ -1,13 +1,15 @@
 // SPDX-License-Identifier: MPL-2.0
 // Copyright (c) 2026 Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 //
-// Deno.affine — issue #122 host bindings for the Deno-ESM backend.
+// Deno.affine — issue #122 host bindings (JSON / bytes / path helpers).
 //
 // Unlike stdlib/Vscode.affine (issue #35), these externs are NOT a
 // wasm-FFI surface with an Int-handle/readString contract. The
-// `--deno-esm` backend (lib/codegen_deno.ml) is a *direct* AST → ES
-// module transpiler with no wasm boundary, so each `extern fn` below is
-// lowered, at compile time, straight to its host expression:
+// `--bun-esm` backend (lib/codegen_deno.ml, `codegen_bun`) is a *direct*
+// AST → ES module transpiler with no wasm boundary, so each `extern fn`
+// below is lowered, at compile time, straight to its host expression
+// (Bun Node-compat for FS; JSON/Date stay platform-neutral). `--deno-esm`
+// is retired (E0826).
 //
 //   writeTextFile(p, c)  ->  Deno.writeTextFileSync(p, c)
 //   jsonParse(s)         ->  JSON.parse(s)
diff --git a/stdlib/Dom.affine b/stdlib/Dom.affine
index 40e673cf..11b13c88 100644
--- a/stdlib/Dom.affine
+++ b/stdlib/Dom.affine
@@ -5,8 +5,10 @@
 //
 // Canonical `module Dom` so `use Dom::{div, h1, p, text, replaceBody}`
 // resolves from stdlib/. Constructors are pure VNode builders (no host
-// FFI). Runtime mount lives in affinescript-dom (the reconciler); this
-// module is the compile-time target for idaptik's pilot syntax.
+// FFI, no `/ IO` row — Canvas-style erasure). Runtime mount lives in
+// affinescript-dom (the reconciler); this module is the compile-time
+// target for idaptik's pilot syntax. `--bun-esm` is the JS-host ESM
+// emit; Deno-ESM is retired.
 //
 // Attrs are `[(String, String)]` — the same tuple-list shape as
 // `Http.affine` headers. Record-literal attrs (`#{style: ...}`) are a
diff --git a/tests/codegen-deno/aggregate_smoke.harness.mjs b/tests/codegen-deno/aggregate_smoke.harness.mjs
index b85949ce..7b0fd0f3 100644
--- a/tests/codegen-deno/aggregate_smoke.harness.mjs
+++ b/tests/codegen-deno/aggregate_smoke.harness.mjs
@@ -212,7 +212,7 @@ globalThis.__as_sqlite = {
   txDb() { return 0; }, txIsLive() { return false; },
 };
 
-const mod = await import("./aggregate_smoke.deno.js");
+const mod = await import("./aggregate_smoke.bun.js");
 
 // ── COUNT ───────────────────────────────────────────────────────────
 assert.equal(mod.smoke_count(":memory:"), 5, "smoke_count: 5 rows inserted");
diff --git a/tests/codegen-deno/bytes_binary_io.harness.mjs b/tests/codegen-deno/bytes_binary_io.harness.mjs
index ef4984d5..ee764998 100644
--- a/tests/codegen-deno/bytes_binary_io.harness.mjs
+++ b/tests/codegen-deno/bytes_binary_io.harness.mjs
@@ -15,7 +15,7 @@ const {
   read_mouse_y,
   fill_byte,
   fill_first,
-} = await import("./bytes_binary_io.deno.js");
+} = await import("./bytes_binary_io.bun.js");
 
 // Round-trip: build a Key event and read every field back.
 {
diff --git a/tests/codegen-deno/canvas_smoke.harness.mjs b/tests/codegen-deno/canvas_smoke.harness.mjs
index d0814e2e..f9fc53ed 100644
--- a/tests/codegen-deno/canvas_smoke.harness.mjs
+++ b/tests/codegen-deno/canvas_smoke.harness.mjs
@@ -42,7 +42,7 @@ class MockCtx2D {
 const ctx = new MockCtx2D();
 const canvas = { getContext: (kind) => { assert.equal(kind, "2d", "getContext called with '2d'"); return ctx; } };
 
-const { smokeRects, smokePath, smokeTransform, smokeText, smokeImages } = await import("./canvas_smoke.deno.js");
+const { smokeRects, smokePath, smokeTransform, smokeText, smokeImages } = await import("./canvas_smoke.bun.js");
 
 // Rects: assert each style + each of the three rect ops + clear.
 const ctxBack = smokeRects(canvas);
diff --git a/tests/codegen-deno/class_basic.harness.mjs b/tests/codegen-deno/class_basic.harness.mjs
index 447245e3..33469971 100644
--- a/tests/codegen-deno/class_basic.harness.mjs
+++ b/tests/codegen-deno/class_basic.harness.mjs
@@ -9,7 +9,7 @@ import {
   ANSWER,
   Red,
   Green,
-} from "./class_basic.deno.js";
+} from "./class_basic.bun.js";
 
 // struct + receiver-first fns -> class with synthesised constructor
 const c = new Counter(10);
diff --git a/tests/codegen-deno/control_flow.harness.mjs b/tests/codegen-deno/control_flow.harness.mjs
index b7ac940f..6ba15b42 100644
--- a/tests/codegen-deno/control_flow.harness.mjs
+++ b/tests/codegen-deno/control_flow.harness.mjs
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 // issue #122 v2.1 — statement-position return / control flow.
 import assert from "node:assert/strict";
-import { sum_to, classify, first_even } from "./control_flow.deno.js";
+import { sum_to, classify, first_even } from "./control_flow.bun.js";
 
 assert.equal(sum_to(5), 15, "while-loop + trailing return");
 assert.equal(sum_to(0), 0, "while-loop zero iterations");
diff --git a/tests/codegen-deno/deno_scripting.harness.mjs b/tests/codegen-deno/deno_scripting.harness.mjs
index d2e3d6ca..b12fb92d 100644
--- a/tests/codegen-deno/deno_scripting.harness.mjs
+++ b/tests/codegen-deno/deno_scripting.harness.mjs
@@ -43,7 +43,7 @@ const {
   is_pa_code,
   warn_then_zero,
   exit_with,
-} = await import("./deno_scripting.deno.js");
+} = await import("./deno_scripting.bun.js");
 
 // walkRecursive — depth-first across nested dirs.
 assert.equal(count_walked("/root"), 3, "walkRecursive finds 3 files (a.txt + b.txt + c.txt)");
diff --git a/tests/codegen-deno/deno_scripting_part2.harness.mjs b/tests/codegen-deno/deno_scripting_part2.harness.mjs
index 3b635f67..11e24245 100644
--- a/tests/codegen-deno/deno_scripting_part2.harness.mjs
+++ b/tests/codegen-deno/deno_scripting_part2.harness.mjs
@@ -38,7 +38,7 @@ const {
   header_string,
   module_url_has_scheme,
   discard_chain,
-} = await import("./deno_scripting_part2.deno.js");
+} = await import("./deno_scripting_part2.bun.js");
 
 // statIsFile / statIsDirectory
 assert.equal(classify_path("/etc/hosts"), 1, "statIsFile true for a regular file");
diff --git a/tests/codegen-deno/deno_string_fmt.harness.mjs b/tests/codegen-deno/deno_string_fmt.harness.mjs
index a90420d5..e28785b9 100644
--- a/tests/codegen-deno/deno_string_fmt.harness.mjs
+++ b/tests/codegen-deno/deno_string_fmt.harness.mjs
@@ -8,7 +8,7 @@ const {
   drop_ts_suffix,
   drop_missing_suffix,
   fmt_pct,
-} = await import("./deno_string_fmt.deno.js");
+} = await import("./deno_string_fmt.bun.js");
 
 // endsWith
 assert.equal(is_ts("foo.ts"),   true,  "endsWith hit");
diff --git a/tests/codegen-deno/dom_startup_error.affine b/tests/codegen-deno/dom_startup_error.affine
new file mode 100644
index 00000000..b7a4cc18
--- /dev/null
+++ b/tests/codegen-deno/dom_startup_error.affine
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MPL-2.0
+// #56 aspirational idaptik StartupError shape, in syntax that compiles
+// today: `use` not `import`, tuple-list attrs not `{style: bg}`.
+// Record-literal attrs remain `#{field: value}` in the language; the
+// migration assistant (#57) emits tuple lists / `#{…}`, not JS `{}`.
+
+use Console::{log};
+use Dom::{VNode, div, h1, p, text};
+
+pub fn startupError(msg: String) -> VNode {
+  log(msg);
+  let _style = #{ bg: "crimson" };
+  div([("class", "startup-error")], [h1([], "Startup error"), p([], msg), text("")])
+}
diff --git a/tests/codegen-deno/dom_startup_error.harness.mjs b/tests/codegen-deno/dom_startup_error.harness.mjs
new file mode 100644
index 00000000..69299b51
--- /dev/null
+++ b/tests/codegen-deno/dom_startup_error.harness.mjs
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: MPL-2.0
+import assert from "node:assert/strict";
+import { startupError } from "./dom_startup_error.bun.js";
+
+const logs = [];
+const origLog = console.log;
+console.log = (...a) => { logs.push(a); };
+try {
+  const node = startupError("boom");
+  assert.equal(node.tag, "VElem");
+  assert.equal(node.values[0], "div");
+  const attrs = node.values[1];
+  assert.equal(attrs[0][0], "class");
+  const kids = node.values[2];
+  assert.equal(kids[0].values[0], "h1");
+  assert.equal(kids[1].values[0], "p");
+} finally {
+  console.log = origLog;
+}
+assert.ok(logs.some((x) => String(x[0]).includes("boom")));
+console.log("dom_startup_error.harness.mjs OK");
diff --git a/tests/codegen-deno/dom_window_smoke.harness.mjs b/tests/codegen-deno/dom_window_smoke.harness.mjs
index 6df85549..a33970a6 100644
--- a/tests/codegen-deno/dom_window_smoke.harness.mjs
+++ b/tests/codegen-deno/dom_window_smoke.harness.mjs
@@ -43,7 +43,7 @@ globalThis.document = document;
 
 const {
   smokeWindow, smokeTimers, smokeDocument, smokeUtil,
-} = await import("./dom_window_smoke.deno.js");
+} = await import("./dom_window_smoke.bun.js");
 
 const handler = () => 0;
 assert.equal(smokeWindow(handler), 0);
diff --git a/tests/codegen-deno/encoding_smoke.harness.mjs b/tests/codegen-deno/encoding_smoke.harness.mjs
index 83b7534039dfb6c85aaa2fd89ca5dce77cb53af3..47aee476ef9f770a3b19c39a2f573d489700f860 100644
GIT binary patch
delta 16
XcmX>nc~){m6C-m{Y2M~GMh|WPH|Yh|

delta 17
YcmX>rc}{Xe6C+DXYF_^4Rz?qQ06t;{Hvj+t

diff --git a/tests/codegen-deno/http_fetch.harness.mjs b/tests/codegen-deno/http_fetch.harness.mjs
index 98c17aa2..fc9814f8 100644
--- a/tests/codegen-deno/http_fetch.harness.mjs
+++ b/tests/codegen-deno/http_fetch.harness.mjs
@@ -27,7 +27,7 @@ const {
   req_get_status,
   req_post_body,
   ok_get,
-} = await import("./http_fetch.deno.js");
+} = await import("./http_fetch.bun.js");
 
 // GET — status round-trips, no body sent
 assert.equal(await get_status("https://example.test/ok"), 200, "GET 200");
diff --git a/tests/codegen-deno/int_div.harness.mjs b/tests/codegen-deno/int_div.harness.mjs
index 4a2094a2..f2c41fc1 100644
--- a/tests/codegen-deno/int_div.harness.mjs
+++ b/tests/codegen-deno/int_div.harness.mjs
@@ -15,7 +15,7 @@ import {
   for_lit,
   idx_half,
   for_float,
-} from "./int_div.deno.js";
+} from "./int_div.bun.js";
 
 // Integer division truncates toward zero.
 assert.equal(idiv(255, 16), 15, "idiv(255,16)");
diff --git a/tests/codegen-deno/ipc_smoke.harness.mjs b/tests/codegen-deno/ipc_smoke.harness.mjs
index 9f0e3c88..b63bc0d0 100644
--- a/tests/codegen-deno/ipc_smoke.harness.mjs
+++ b/tests/codegen-deno/ipc_smoke.harness.mjs
@@ -7,7 +7,7 @@
 
 import assert from "node:assert/strict";
 
-const { smokeChannelFlow, smokeCloseFlow, smokeTargetFlow, smokeStructuredClone } = await import("./ipc_smoke.deno.js");
+const { smokeChannelFlow, smokeCloseFlow, smokeTargetFlow, smokeStructuredClone } = await import("./ipc_smoke.bun.js");
 
 // Channel flow: assert handlers fire on the peer side, postMessage
 // round-trips identical payload, and close()s don't throw.
diff --git a/tests/codegen-deno/loop_break_continue.harness.mjs b/tests/codegen-deno/loop_break_continue.harness.mjs
index b193830e..6b03458b 100644
--- a/tests/codegen-deno/loop_break_continue.harness.mjs
+++ b/tests/codegen-deno/loop_break_continue.harness.mjs
@@ -6,7 +6,7 @@ import {
   sum_odd,
   find_first,
   count_positive,
-} from "./loop_break_continue.deno.js";
+} from "./loop_break_continue.bun.js";
 
 // sum_until: 0+1+2+3+4+5 = 15 (stops at total >= 10 once total reaches 15).
 // Sequence: total=0 (i=0, +0=0), 1, 3, 6, 10 → break.
diff --git a/tests/codegen-deno/match_enum.harness.mjs b/tests/codegen-deno/match_enum.harness.mjs
index 25089b01..2692ed5d 100644
--- a/tests/codegen-deno/match_enum.harness.mjs
+++ b/tests/codegen-deno/match_enum.harness.mjs
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 // issue #122 v2.4 — qualified Type::Variant patterns + recursive ADTs.
 import assert from "node:assert/strict";
-import { rank, Red, Blue, len, sum, demo_list } from "./match_enum.deno.js";
+import { rank, Red, Blue, len, sum, demo_list } from "./match_enum.bun.js";
 
 assert.equal(rank(Red), 1, "match expr-body, nullary qualified pattern");
 assert.equal(rank(Blue), 3, "match expr-body, last arm");
diff --git a/tests/codegen-deno/motion_smoke.harness.mjs b/tests/codegen-deno/motion_smoke.harness.mjs
index 7b9abe39..a2326e35 100644
--- a/tests/codegen-deno/motion_smoke.harness.mjs
+++ b/tests/codegen-deno/motion_smoke.harness.mjs
@@ -55,7 +55,7 @@ const {
   smokeTween,
   smokeSpring,
   smokeEase,
-} = await import("./motion_smoke.deno.js");
+} = await import("./motion_smoke.bun.js");
 
 // ---- animate + cancel (original surface) ----
 const controls = smokeAnimate("#player", { x: 100, opacity: 0.5 }, { duration: 1.0 });
diff --git a/tests/codegen-deno/non_ascii.harness.mjs b/tests/codegen-deno/non_ascii.harness.mjs
index a36c8b40..7d55f991 100644
--- a/tests/codegen-deno/non_ascii.harness.mjs
+++ b/tests/codegen-deno/non_ascii.harness.mjs
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MPL-2.0
 // issue #460 — round-trip non-ASCII string literals through the
 // Deno-ESM backend under strict-mode ESM. The `import` itself is the
-// strictest test: if the emitted `.deno.js` contains octal escapes,
+// strictest test: if the emitted `.bun.js` contains octal escapes,
 // the module fails to parse and the import throws SyntaxError before
 // any assertion can run.
 import assert from "node:assert/strict";
@@ -14,7 +14,7 @@ import {
   mixed,
   ascii_only,
   quotes_and_backslash,
-} from "./non_ascii.deno.js";
+} from "./non_ascii.bun.js";
 
 assert.equal(emoji_cross(), "❌", "BMP emoji ❌ round-trips");
 assert.equal(emoji_check(), "✓", "BMP check mark ✓ round-trips");
diff --git a/tests/codegen-deno/pixi_smoke.harness.mjs b/tests/codegen-deno/pixi_smoke.harness.mjs
index 70ea63db..ca17de12 100644
--- a/tests/codegen-deno/pixi_smoke.harness.mjs
+++ b/tests/codegen-deno/pixi_smoke.harness.mjs
@@ -114,7 +114,7 @@ globalThis.__as_pixi = {
   },
 };
 
-const { smokeInit, smokeSpriteFlow, smokeGraphicsFlow, smokeAccessorsFlow, smokeGapFill } = await import("./pixi_smoke.deno.js");
+const { smokeInit, smokeSpriteFlow, smokeGraphicsFlow, smokeAccessorsFlow, smokeGapFill } = await import("./pixi_smoke.bun.js");
 
 // Async init returns an Application after `await app.init(options)`
 const app = await smokeInit({ width: 800, height: 600, backgroundColor: 0x1099bb });
diff --git a/tests/codegen-deno/pixisound_smoke.harness.mjs b/tests/codegen-deno/pixisound_smoke.harness.mjs
index 2d2dfbd2..08a1c2d5 100644
--- a/tests/codegen-deno/pixisound_smoke.harness.mjs
+++ b/tests/codegen-deno/pixisound_smoke.harness.mjs
@@ -38,7 +38,7 @@ globalThis.__as_pixi_sound = {
 const {
   smokeFrom, smokePlay, smokeStop, smokePause, smokeResume,
   smokeSetVolume, smokeSetLoop,
-} = await import("./pixisound_smoke.deno.js");
+} = await import("./pixisound_smoke.bun.js");
 
 const s = smokeFrom("assets/bgm.mp3");
 assert.equal(lastFromUrl, "assets/bgm.mp3", "from URL reaches host");
diff --git a/tests/codegen-deno/pixiui_smoke.harness.mjs b/tests/codegen-deno/pixiui_smoke.harness.mjs
index 4e9bdc43..1eee8d40 100644
--- a/tests/codegen-deno/pixiui_smoke.harness.mjs
+++ b/tests/codegen-deno/pixiui_smoke.harness.mjs
@@ -64,7 +64,7 @@ globalThis.__as_pixi_ui = {
 };
 
 const { smokeButton, smokeFancyButton, smokeSlider, smokeSwitch, smokeProgressBar, smokeList, smokeInput } =
-  await import("./pixiui_smoke.deno.js");
+  await import("./pixiui_smoke.bun.js");
 
 // ── Button: ctor + onPress + upcast ────────────────────────────────
 const buttonPressCb = () => "pressed";
diff --git a/tests/codegen-deno/random_smoke.harness.mjs b/tests/codegen-deno/random_smoke.harness.mjs
index d560b797..27abb07c 100644
--- a/tests/codegen-deno/random_smoke.harness.mjs
+++ b/tests/codegen-deno/random_smoke.harness.mjs
@@ -8,7 +8,7 @@ const {
   draw_unit,
   draw_in_range,
   perf_tick,
-} = await import("./random_smoke.deno.js");
+} = await import("./random_smoke.bun.js");
 
 // math_random — every draw is in [0, 1).
 for (let i = 0; i < 1000; i++) {
diff --git a/tests/codegen-deno/ref_fields.harness.mjs b/tests/codegen-deno/ref_fields.harness.mjs
index e4c0b1ac..d09f5e98 100644
--- a/tests/codegen-deno/ref_fields.harness.mjs
+++ b/tests/codegen-deno/ref_fields.harness.mjs
@@ -4,7 +4,7 @@
 // take Point first (ref/own/mut) so they synthesise as Point methods —
 // exercising auto-deref field access *and* class synthesis together.
 import assert from "node:assert/strict";
-import { Point } from "./ref_fields.deno.js";
+import { Point } from "./ref_fields.bun.js";
 
 const p = new Point(3, 4);
 assert.equal(p.x, 3, "constructor assigns x");
diff --git a/tests/codegen-deno/sqlite_introspect_bulk.harness.mjs b/tests/codegen-deno/sqlite_introspect_bulk.harness.mjs
index 8ae8cf14..42419a44 100644
--- a/tests/codegen-deno/sqlite_introspect_bulk.harness.mjs
+++ b/tests/codegen-deno/sqlite_introspect_bulk.harness.mjs
@@ -168,7 +168,7 @@ globalThis.__as_sqlite = {
   reset() {}, finalize() {},
 };
 
-const mod = await import("./sqlite_introspect_bulk.deno.js");
+const mod = await import("./sqlite_introspect_bulk.bun.js");
 
 // ── schema_tables ────────────────────────────────────────────────────
 const tablesJson = mod.smoke_schema_tables(":memory:");
diff --git a/tests/codegen-deno/sqlite_prepared.harness.mjs b/tests/codegen-deno/sqlite_prepared.harness.mjs
index 53aab5e1..d84874ba 100644
--- a/tests/codegen-deno/sqlite_prepared.harness.mjs
+++ b/tests/codegen-deno/sqlite_prepared.harness.mjs
@@ -247,7 +247,7 @@ globalThis.__as_sqlite = {
   finalize(s) { stmts.delete(s); },
 };
 
-const mod = await import("./sqlite_prepared.deno.js");
+const mod = await import("./sqlite_prepared.bun.js");
 
 assert.equal(
   mod.smoke_prepare_bind_int_step_finalize(":memory:"),
diff --git a/tests/codegen-deno/sqlite_smoke.harness.mjs b/tests/codegen-deno/sqlite_smoke.harness.mjs
index d9edd1bc..e151aca8 100644
--- a/tests/codegen-deno/sqlite_smoke.harness.mjs
+++ b/tests/codegen-deno/sqlite_smoke.harness.mjs
@@ -125,7 +125,7 @@ globalThis.__as_sqlite = {
   },
 };
 
-const mod = await import("./sqlite_smoke.deno.js");
+const mod = await import("./sqlite_smoke.bun.js");
 
 assert.equal(
   mod.smoke_full_lifecycle(":memory:"),
diff --git a/tests/codegen-deno/string_lex_cmp.harness.mjs b/tests/codegen-deno/string_lex_cmp.harness.mjs
index 3f284548..7a3876c4 100644
--- a/tests/codegen-deno/string_lex_cmp.harness.mjs
+++ b/tests/codegen-deno/string_lex_cmp.harness.mjs
@@ -8,7 +8,7 @@ import {
   first_lt, first_gt,
   equal_strings_le, equal_strings_ge, equal_strings_lt,
   empty_lt, empty_le, prefix_lt,
-} from "./string_lex_cmp.deno.js";
+} from "./string_lex_cmp.bun.js";
 
 assert.equal(lt("abc", "abd"), true, "abc < abd");
 assert.equal(lt("abd", "abc"), false, "abd not < abc");
diff --git a/tests/codegen-deno/string_prims.harness.mjs b/tests/codegen-deno/string_prims.harness.mjs
index 5a018c41..b406cdfc 100644
--- a/tests/codegen-deno/string_prims.harness.mjs
+++ b/tests/codegen-deno/string_prims.harness.mjs
@@ -9,7 +9,7 @@ import {
   n2s,
   str_cat,
   arr_cat,
-} from "./string_prims.deno.js";
+} from "./string_prims.bun.js";
 
 assert.equal(ends_with2("foo.json", ".json"), true, "string_sub/len ends_with");
 assert.equal(ends_with2("foo.txt", ".json"), false, "negative ends_with");
diff --git a/tests/codegen-deno/transaction_smoke.harness.mjs b/tests/codegen-deno/transaction_smoke.harness.mjs
index 8e4cd9a1..c1968a00 100644
--- a/tests/codegen-deno/transaction_smoke.harness.mjs
+++ b/tests/codegen-deno/transaction_smoke.harness.mjs
@@ -189,7 +189,7 @@ globalThis.__as_sqlite = {
   exportCsv() { return 0; }, lastError() { return ""; },
 };
 
-const mod = await import("./transaction_smoke.deno.js");
+const mod = await import("./transaction_smoke.bun.js");
 
 // ── commit_persists ────────────────────────────────────────────────
 assert.equal(
diff --git a/tests/codegen-deno/wasm_call.harness.mjs b/tests/codegen-deno/wasm_call.harness.mjs
index b42044b0..bb69b771 100644
--- a/tests/codegen-deno/wasm_call.harness.mjs
+++ b/tests/codegen-deno/wasm_call.harness.mjs
@@ -6,7 +6,7 @@
 // __as_wasmCall(exports, "add", [a, b]), round-trips correctly.
 
 import assert from "node:assert/strict";
-import { addViaWasm } from "./wasm_call.deno.js";
+import { addViaWasm } from "./wasm_call.bun.js";
 
 // Hand-built minimal wasm module:
 //   (module
diff --git a/tests/codegen-deno/wasm_exports_demo.harness.mjs b/tests/codegen-deno/wasm_exports_demo.harness.mjs
index 4d8e4823..c54010de 100644
--- a/tests/codegen-deno/wasm_exports_demo.harness.mjs
+++ b/tests/codegen-deno/wasm_exports_demo.harness.mjs
@@ -11,7 +11,7 @@ import {
   add_i64_via_wasm,
   mul_f32_via_wasm,
   mul_f64_via_wasm,
-} from "./wasm_exports_demo.deno.js";
+} from "./wasm_exports_demo.bun.js";
 
 // Hand-built minimal wasm module:
 //   (module
diff --git a/tests/codegen-deno/wasm_wasi_instance.harness.mjs b/tests/codegen-deno/wasm_wasi_instance.harness.mjs
index 7ea8e530..59b30c3e 100644
--- a/tests/codegen-deno/wasm_wasi_instance.harness.mjs
+++ b/tests/codegen-deno/wasm_wasi_instance.harness.mjs
@@ -10,7 +10,7 @@
 // the fix this threw "Imports argument must be present and must be an object".
 
 import assert from "node:assert/strict";
-import { addViaWasiWasm } from "./wasm_wasi_instance.deno.js";
+import { addViaWasiWasm } from "./wasm_wasi_instance.bun.js";
 
 // (module
 //   (import "wasi_snapshot_preview1" "fd_write"
diff --git a/tests/codegen/dom_pilot_startup_error.affine b/tests/codegen/dom_pilot_startup_error.affine
new file mode 100644
index 00000000..642f813f
--- /dev/null
+++ b/tests/codegen/dom_pilot_startup_error.affine
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MPL-2.0
+// #56 — wasm compile-pass of the idaptik StartupError shape
+// (in-file, no stdlib), matching tests/codegen/dom_pilot_surface.affine.
+
+pub enum VNode {
+  VText(String),
+  VElem(String, [(String, String)], [VNode])
+}
+
+pub fn text(content: String) -> VNode = VText(content);
+
+pub fn h(tag: String, attrs: [(String, String)], children: [VNode]) -> VNode =
+  VElem(tag, attrs, children);
+
+pub fn div(attrs: [(String, String)], children: [VNode]) -> VNode =
+  h("div", attrs, children);
+
+pub fn h1(attrs: [(String, String)], content: String) -> VNode =
+  h("h1", attrs, [text(content)]);
+
+pub fn p(attrs: [(String, String)], content: String) -> VNode =
+  h("p", attrs, [text(content)]);
+
+pub fn startupError(msg: String) -> VNode =
+  div([("class", "startup-error")], [h1([], "Startup error"), p([], msg)]);
+
+pub fn main() -> Int {
+  let _s = #{ bg: "crimson" };
+  let _n = startupError("boom");
+  0
+}
diff --git a/tests/codegen/test_dom_pilot_startup_error.mjs b/tests/codegen/test_dom_pilot_startup_error.mjs
new file mode 100644
index 00000000..608bed5e
--- /dev/null
+++ b/tests/codegen/test_dom_pilot_startup_error.mjs
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MPL-2.0
+// #56 — wasm instantiate of the aspirational StartupError shape.
+import assert from 'node:assert/strict';
+import { readFile } from 'node:fs/promises';
+
+const buf = await readFile('./tests/codegen/dom_pilot_startup_error.wasm');
+const mod = new WebAssembly.Module(buf);
+const inst = (await WebAssembly.instantiate(mod, {
+  wasi_snapshot_preview1: { fd_write: () => 0 },
+})).instance;
+assert.equal(inst.exports.main(), 0, 'dom pilot startupError compiled and ran');
+console.log('test_dom_pilot_startup_error.mjs OK');
diff --git a/tools/run_codegen_bun_tests.sh b/tools/run_codegen_bun_tests.sh
index 32e999c1..3393f8f5 100755
--- a/tools/run_codegen_bun_tests.sh
+++ b/tools/run_codegen_bun_tests.sh
@@ -31,22 +31,22 @@ second="$TEST_DIR/reproducibility.bun.js"
 "${COMPILE_CMD[@]}" "$src" -o "$second" --bun-esm
 cmp "$out" "$second"
 
-conflict_log="$TEST_DIR/backend-conflict.log"
-if "${COMPILE_CMD[@]}" "$src" -o "$out" --deno-esm --bun-esm \
-    >"$conflict_log" 2>&1; then
-  echo "error: conflicting host-profile flags compiled successfully" >&2
+removed_log="$TEST_DIR/deno-removed.log"
+if "${COMPILE_CMD[@]}" "$src" -o "$out" --deno-esm \
+    >"$removed_log" 2>&1; then
+  echo "error: retired --deno-esm compiled successfully" >&2
   exit 1
 fi
-grep -q -- '--deno-esm and --bun-esm are mutually exclusive' "$conflict_log"
+grep -q 'Deno-ESM was removed' "$removed_log"
 
-conflict_json="$TEST_DIR/backend-conflict.json"
-if "${COMPILE_CMD[@]}" "$src" -o "$out" --deno-esm --bun-esm --json \
-    >"$conflict_json" 2>&1; then
-  echo "error: conflicting host-profile flags passed in JSON mode" >&2
+removed_json="$TEST_DIR/deno-removed.json"
+if "${COMPILE_CMD[@]}" "$src" -o "${out%.bun.js}.deno.js" --json \
+    >"$removed_json" 2>&1; then
+  echo "error: retired .deno.js output compiled successfully" >&2
   exit 1
 fi
-grep -q '"code":"E0826"' "$conflict_json"
-grep -q '"success":false' "$conflict_json"
+grep -q '"code":"E0826"' "$removed_json"
+grep -q '"success":false' "$removed_json"
 
 for js in "$TEST_DIR"/*.harness.mjs; do
   (cd "$TEST_DIR" && AFFINESCRIPT_BUN_PROBE=estate bun "$(basename "$js")" alpha beta)
diff --git a/tools/run_codegen_deno_tests.sh b/tools/run_codegen_deno_tests.sh
index 2a06de8c..1e16f01e 100755
--- a/tools/run_codegen_deno_tests.sh
+++ b/tools/run_codegen_deno_tests.sh
@@ -1,15 +1,12 @@
 #!/usr/bin/env bash
 # SPDX-License-Identifier: MPL-2.0
-# issue #122 — Deno-ESM backend regression runner.
+# issue #122 corpus — now compiled with the Bun-ESM backend.
 #
-# Mirrors tools/run_codegen_wasm_tests.sh: for every fixture in
-# tests/codegen-deno/, compile FILE.affine -> FILE.deno.js with the
-# --deno-esm backend, then run every *.harness.mjs with `node`.
-#
-# Node is used (not deno) deliberately: CI provisions Node 20 but not
-# Deno, and the Phase 1 fixtures are pure logic — the generated module
-# only references the `Deno` global lazily inside helper bodies that the
-# harnesses never call, so plain Node ESM exercises them faithfully.
+# Directory name `tests/codegen-deno/` is historical. Every fixture is
+# compiled with `--bun-esm` to FILE.bun.js. Harnesses still run under
+# `node` in CI (Node 20 is provisioned; these fixtures do not need the
+# Bun binary — they mock host objects). Native Bun acceptance lives in
+# tools/run_codegen_bun_tests.sh.
 set -euo pipefail
 
 ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
@@ -26,16 +23,16 @@ fi
 echo "Using compiler: ${COMPILE_CMD[*]}"
 
 for src in "$TEST_DIR"/*.affine; do
-  out="${src%.affine}.deno.js"
+  out="${src%.affine}.bun.js"
   echo "Compiling $(basename "$src") -> $(basename "$out")"
-  "${COMPILE_CMD[@]}" "$src" -o "$out" --deno-esm
+  "${COMPILE_CMD[@]}" "$src" -o "$out" --bun-esm
 done
 
 echo ""
-echo "Running Deno-ESM harnesses (node)"
+echo "Running ESM harnesses (node, Bun-ESM artefacts)"
 for js in "$TEST_DIR"/*.harness.mjs; do
   echo "node $(basename "$js")"
   (cd "$TEST_DIR" && node "$(basename "$js")")
 done
 
-echo "All codegen Deno-ESM tests passed."
+echo "All codegen Bun-ESM (legacy codegen-deno corpus) tests passed."