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Mentioning/Opening large xlsx file crashes session #50336
Description
Description
- Mentioning a larger xlsx file 12MB with
@foo.xlsxcrashes the session. - Workaround - use sth. like
"foo.xlsx" how big?
timestamp=2026-09-21T09:56:44.764Z level=INFO run=1638ac46 message=event event.id=evt_0c365825c001i9glaoT4GrZf6D event.created=1789984604764 event.type=provider.updated event.location.directory=/private/var/folders/9l/l_jnc13s4rj9nr7ylz0_ypdr0000gn/T/opencode event.location.workspaceID=undefined event.data={}
timestamp=2026-09-21T09:56:44.779Z level=INFO run=1638ac46 message=event event.id=evt_0c365826b001TJDtRbm0U152Yg event.created=1789984604779 event.type=model.updated event.location.directory=/private/var/folders/9l/l_jnc13s4rj9nr7ylz0_ypdr0000gn/T/opencode event.location.workspaceID=undefined event.data={} http.span=300065 role=server
timestamp=2026-09-21T09:56:45.352Z level=INFO run=fb99b67b message="cli starting" version=2.0.11 channel=latest local=false args=[] role=cli
timestamp=2026-09-21T09:56:45.392Z level=INFO run=fb99b67b message="event stream connecting" component=client attempt=0 role=cli
timestamp=2026-09-21T09:56:45.395Z level=INFO run=fb99b67b message="event stream connected" component=client role=cli
timestamp=2026-09-21T09:56:45.400Z level=INFO run=fb99b67b message="plugin reconciliation started" component=plugin id=1 role=cli
timestamp=2026-09-21T09:56:45.406Z level=INFO run=fb99b67b message="plugin reconciliation completed" component=plugin id=1 durationMs=6 plugins=12 role=cli
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timestamp=2026-09-21T09:56:45.432Z level=INFO run=fb99b67b message="plugin reconciliation started" component=plugin id=3 role=cli
timestamp=2026-09-21T09:56:45.432Z level=INFO run=fb99b67b message="plugin reconciliation completed" component=plugin id=3 durationMs=0 plugins=12 role=cli
timestamp=2026-09-21T09:56:45.447Z level=INFO run=fb99b67b message="plugin reconciliation started" component=plugin id=4 role=cli
timestamp=2026-09-21T09:56:45.452Z level=INFO run=fb99b67b message="plugin reconciliation completed" component=plugin id=4 durationMs=5 plugins=12 role=cli
timestamp=2026-09-21T09:56:45.862Z level=INFO run=fb99b67b message="update check" current=2.0.11 latest=2.0.12 role=cli
timestamp=2026-09-21T09:56:45.863Z level=INFO run=fb99b67b message="OpenCode update available" current=2.0.11 latest=2.0.12 action=notify role=cli
timestamp=2026-09-21T09:56:46.412Z level=INFO run=1638ac46 message="spawning process" command=/opt/homebrew/bin/rg args="[\"--no-config\",\"--files\",\"--glob=!**/.git/**\",\".\"]" cwd=/private/tmp/br0ken http.span=4 role=server
timestamp=2026-09-21T09:56:48.335Z level=INFO run=1638ac46 cause="Error: Schema validation failed\n at <anonymous> (/$bunfs/root/chunk-5tvdqet6.js:4:36213)\n at <anonymous> (/$bunfs/root/chunk-f79f68bn.js:122:299)\n at SessionPrompt.normalizeImageAttachment (/$bunfs/root/chunk-f79f68bn.js:122:23)\n at SessionPrompt.normalizeImageAttachment (definition) (/$bunfs/root/chunk-f79f68bn.js:122:193)\n at SessionPrompt.materializeAttachment (/$bunfs/root/chunk-fzekn76j.js:24:19733)\n at SessionPrompt.materializeAttachment (definition) (/$bunfs/root/chunk-f79f68bn.js:120:1878)\n at SessionPrompt.prepare (/$bunfs/root/chunk-f79f68bn.js:137:4860)\n at SessionPrompt.prepare (definition) (/$bunfs/root/chunk-f79f68bn.js:120:834)\n at Session.prompt (/$bunfs/root/chunk-pa155s7f.js:432:7403)\n at Session.prompt (definition) (/$bunfs/root/chunk-f79f68bn.js:137:4621)\n at Effect.fn (/$bunfs/root/chunk-pa155s7f.js:56:6933)\n at Effect.fn (definition) (/$bunfs/root/chunk-pa155s7f.js:432:7363) {\n [cause]: Error: {\"~effect/SchemaIssue/Issue\":\"~effect/SchemaIssue/Issue\",\"_tag\":\"Composite\",\"ast\":{\"~effect/Schema\":\"~effect/Schema\",\"checks\":[{\"_tag\":\"Filter\",\"annotations\":{\"expected\":\"a string matching the RegExp ^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$\",\"representation\":{\"id\":\"effect/schema/isPattern\",\"payload\":{\"source\":\"^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$\",\"flags\":\"\"}},\"arbitrary\":{\"constraint\":{\"patterns\":[\"^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$\"]}},\"identifier\":\"Prompt.Base64\"},\"aborted\":false}],\"_tag\":\"String\"},\"issues\":[{\"~effect/SchemaIssue/Issue\":\"~effect/SchemaIssue/Issue\",\"_tag\":\"Filter\",\"filter\":{\"_tag\":\"Filter\",\"annotations\":{\"expected\":\"a string matching the RegExp ^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$\",\"representation\":{\"id\":\"effect/schema/isPattern\",\"payload\":{\"source\":\"^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$\",\"flags\":\"\"}},\"arbitrary\":{\"constraint\":{\"patterns\":[\"^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$\"]}},\"identifier\":\"Prompt.Base64\"},\"aborted\":false},\"issue\":{\"~effect/SchemaIssue/Issue\":\"~effect/SchemaIssue/Issue\",\"_tag\":\"InvalidValue\"}}]}\n}" http.span=66 role=server http.method=POST http.url=/api/session/ses_f3c9a701dffe1oxiskq13lE21O/prompt http.status=500
timestamp=2026-09-21T09:57:04.132Z level=INFO run=1638ac46 message=event event.id=evt_0c365ce03001T6kgO6az9e0kkC event.created=1789984624132 event.type=provider.updated event.location.directory=/private/tmp/foo event.location.workspaceID=undefined event.data={}
timestamp=2026-09-21T09:57:04.144Z level=INFO run=1638ac46 message=event event.id=evt_0c365ce10001vKJXLp3nHZb2BM event.created=1789984624144 event.type=model.updated event.location.directory=/private/tmp/foo event.location.workspaceID=undefined event.data={} http.span=1199984 role=server
Plugins
No response
OpenCode version
v2.0.12
Steps to reproduce
@foo.xlsxlarge xlsx file
Screenshot and/or share link
Operating System
macOS latest
Terminal
Ghostty
Activity
darellchua2 commentedon Sep 25, 2026
Same root cause as #45558: the
Prompt.Base64pattern check inpackages/schema/src/prompt.tsuses a(?:X{4})*regex that fails on multi-MB strings (silently returnsfalseunder Bun/JSC, the runtime the shipped binary embeds; throws RangeError under V8).materializeAttachmentruns it on the base64 of any@-mentioned file up to 20 MB, which is why a 12 MB xlsx crashes the prompt while small files work. Analysis, repro, and a parity-safe replacement in #45558 — a PR referencing both issues is on the way.atsyplenkov commentedon Oct 7, 2026
Thanks for the report — I hit the same crash and while narrowing it down I think I found the missing piece. It does not seem to be specific to xlsx, and it is not really about the attachment size either: the
Prompt.Base64schema pattern itself silently fails on long strings.I can reproduce it without OpenCode at all, just Bun 1.4.0 and a regex test on base64 that
Bufferproduced (so the input is valid base64 by construction — it round-trips throughBuffer.from(b64, "base64")without loss):nb64.lengthre.test(b64)truetruefalsefalseBisecting the length (in steps of 4) gives 8 257 528 as the longest passing string and 8 257 532 as the shortest failing one — suspiciously close to 2^23 − 2^17 = 8 257 536. The string stays valid base64 throughout; the regex just gives up. On Node 26 (V8) the same call throws
RangeError: Maximum call stack size exceeded, so the pattern looks pathological on both engines — JSC fails silently, which then surfaces as the schemaInvalidValuefrom the logs above.This matches the OpenCode behavior exactly. Minimal repro through the API, no plugins, no first-message requirement — any message carrying the attachment does it:
A 6 150 000-byte file goes through, a 6 200 000-byte file returns
HTTP 500every time, so the effective limit is ~6.19 MB of raw bytes per binary attachment (I tried .docx and .png;text/plainfiles go through the Read path and are unaffected). For what it is worth, when the big attachment happens to be in the first message the TUI reports this as "Failed to set up session — UnexpectedStatus: 500", which sent me looking in completely the wrong direction at first.I suspect the same validation is also what breaks #45558 and #51350, although those look like genuinely non-base64 input (a
data:prefix and such) rather than the length limit here.If the diagnosis looks right, a fix could be to validate with something linear instead of the quantified-group pattern, e.g.
/^[A-Za-z0-9+/]*={0,2}$/together with a separatelength % 4 === 0check — I believe the two are equivalent for the standard alphabet, and neither engine has to backtrack. A size cap would only move the cliff, since the pattern is what chokes.Happy to prepare a PR if that helps.