[davesnx]

browser_ppx is replaced by its own package, ppx_platform, and this repo moves to its 0.3.0 syntax. server-reason-react.browser_ppx is removed.

• Breaking: replace server-reason-react.browser_ppx with ppx_platform in dune pps. Flags stay the same, for example (pps ppx_platform -js server-reason-react.ppx -melange) for Melange.

• Breaking: ppx_platform 0.3.0 renames the syntax. The old names give a compile error that names the replacement, for example [@platform js] was removed in 0.3.0, use [@melange_only].

  Removed	Use
  let%browser_only, [%browser_only ...]	let%melange_only, [%melange_only ...]
  [@browser_only], [@platform js]	[@melange_only]
  [@platform native]	[@native_only]
  Server / Client in switch%platform	Native / Melange
  [@alert "-browser_only"]	[@alert "-melange_only"]

• Breaking: effect bodies are no longer wrapped automatically. Effects never run on the server (native React.useEffect* is a no-op), so this only matters at compile time: an effect body that uses Melange-only modules must be wrapped explicitly, React.useEffect0([%melange_only () => ...]). server-reason-react.ppx does not touch effects and does not depend on ppx_platform.

• Breaking: Runtime.platform (Server | Client) is removed. ppx_platform matches case names, not the scrutinee, and nothing used the type.

• melange.ppx lets externals through when they carry [@melange_only] (was [@platform js] / [@browser_only]), and its error hints use the new names.

• Generated native code calls Ppx_platform.fail_melange_only. Runtime.Impossible_in_ssr and Runtime.fail_impossible_action_in_ssr are aliases of Ppx_platform.Melange_only and Ppx_platform.fail_melange_only, so existing with Runtime.Impossible_in_ssr _ handlers still catch it.

• Requires ppx_platform >= 0.3.0 from opam-repository. There is no pin-depends and no ppx_platform pin in make pin.

• The browser_ppx docs page is removed. The general syntax lives in the ppx_platform README. The parts specific to server-reason-react (dune setup with -melange, the Runtime.Impossible_in_ssr alias) are in documentation/get-started.mld. The guides list in index.mld keeps "Exclude client code from the native build", linked to that section.

Tests

At 37f7c1f, OCaml 5.4.0, against ppx_platform 0.3.0 installed from opam-repository (not pinned):

• dune build, dune build @runtest --force, dune build @fmt: exit 0. The demo and router browser tests ran with node_modules from an existing checkout.
• opam lint server-reason-react.opam: passed.
• git grep for browser_only, [@platform js|native], Runtime.Server|Client|platform and Server => / Client => finds nothing outside CHANGES.md.
• dune describe pp on demo/universal/native/shared/RR.re drops the [@melange_only] item and keeps the [@native_only] one. On ServerActionWithFormData.re, switch%platform keeps the Native branch.
• packages/server-reason-react-ppx/cram/effect.t: server-reason-react.ppx leaves React.useEffect* calls as written; with ppx_platform in the same driver, an explicit [%melange_only ...] effect body becomes Ppx_platform.fail_melange_only.
• packages/server-reason-react-ppx/cram/runtime_alias.t: a let%melange_only function called on native is caught by with Runtime.Impossible_in_ssr _. With Runtime declaring its own exception instead of the alias, the test fails (mutation check run at 149abc4).
• A scratch file with [@@platform js] under (pps ppx_platform) fails with [ppx_platform] [@platform js] was removed in 0.3.0, use [@melange_only].

Risk: two-way door for this repo. Reverting restores browser_ppx and the old names. Downstream projects that already migrated to ppx_platform 0.3.0 names would need to switch back.

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Project	Deployment	Actions	Updated
server-reason-react	Ready	Preview	Oct 20, 2026 3:55pm UTC

[github-actions]

Benchmarks

Comparison against main (0b1e0bb). Higher is better.

Benchmark	main (ops/sec)	PR (ops/sec)	Change
trivial/renderToStaticMarkup	2,579,364	4,084,831	+58.4% 🟢
trivial/renderToString	2,197,236	2,617,840	+19.1% 🟢
depth/10	63,829	98,001	+53.5% 🟢
depth/25	25,103	39,079	+55.7% 🟢
depth/50	12,778	20,193	+58.0% 🟢
depth/100	6,422	9,872	+53.7% 🟢
width/10	38,656	60,694	+57.0% 🟢
width/100	3,958	6,394	+61.6% 🟢
width/500	726.85	1,184	+62.8% 🟢
width/1000	366.45	605.7	+65.3% 🟢
table/10	25,715	40,583	+57.8% 🟢
table/50	5,494	8,792	+60.0% 🟢
table/100	2,365	3,845	+62.6% 🟢
table/500	509.53	815.29	+60.0% 🟢
props/small	9,923	17,030	+71.6% 🟢
props/medium	3,465	5,931	+71.1% 🟢
props/large	1,181	2,199	+86.2% 🟢
realworld/ecommerce24	6,454	10,471	+62.2% 🟢
realworld/ecommerce48	3,444	5,564	+61.6% 🟢
realworld/dashboard	26,383	44,492	+68.6% 🟢
realworld/blog50	4,145	6,617	+59.7% 🟢
realworld/form	13,699	23,267	+69.8% 🟢
primitive/React.string	17,697,485	32,564,472	+84.0% 🟢
primitive/React.int	8,741,776	17,182,728	+96.6% 🟢
primitive/React.null	28,906,299	50,963,597	+76.3% 🟢
primitive/createElement_empty	10,857,634	21,323,355	+96.4% 🟢
primitive/createElement_children	935,560	1,702,441	+82.0% 🟢
primitive/React.array_10	909,098	1,700,371	+87.0% 🟢
primitive/React.array_100	102,692	193,524	+88.5% 🟢
primitive/React.list_10	930,413	1,705,556	+83.3% 🟢
primitive/React.list_100	103,599	190,967	+84.3% 🟢
rsc/trivial	311,427	512,563	+64.6% 🟢
rsc/depth/50	4,804	8,112	+68.9% 🟢
rsc/width/100	509.16	850.25	+67.0% 🟢
rsc/width/500	91.42	155.66	+70.3% 🟢
rsc/width/1000	41.2	70	+69.9% 🟢
rsc/table/100	257.55	437.15	+69.7% 🟢
rsc/table/500	45.85	79.39	+73.2% 🟢
streaming/renderToStream/wide100	3,576	4,153	+16.2% 🟢
streaming/renderToStream/suspense-drained	35,986	63,160	+75.5% 🟢
rsc/render_html/wide100	508.73	853.47	+67.8% 🟢
rsc/render_html/suspense	15,449	28,290	+83.1% 🟢
rsc/render_model/wide100	1,077	1,683	+56.3% 🟢
router/match/static-small-first	20,276,623	35,620,942	+75.7% 🟢
router/match/static-small-last	30,485,465	51,377,848	+68.5% 🟢
router/match/static-large-first	31,340,073	54,355,924	+73.4% 🟢
router/match/static-large-last	30,771,709	54,598,849	+77.4% 🟢
router/match/static-large-miss	2,802,079	4,432,011	+58.2% 🟢
router/match/dynamic-large-first	1,976,813	3,106,930	+57.2% 🟢
router/match/dynamic-large-last	2,121,451	3,445,045	+62.4% 🟢
router/endpoint/static-large-last	17,291,066	29,485,033	+70.5% 🟢
router/endpoint/dynamic-large-last	2,014,781	3,215,778	+59.6% 🟢
router/parse/path-plain	2,124,415	3,341,616	+57.3% 🟢
router/parse/path-encoded	1,413,520	2,601,347	+84.0% 🟢
router/parse/search	2,342,107	4,310,028	+84.0% 🟢

_{Changes within ±5% are likely noise from the CI runner.}