opencode export <id> | jq produces truncated / invalid JSON when piped (large sessions) #29330

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1. github-actions

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   rekram1-node

   on May 26, 2026
2. github-actions commented on May 26, 2026

   

   github-actionsBot

   on May 26, 2026 – with GitHub Actions

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   This issue might be a duplicate of an existing issue. Please check:

   • opencode debug skill returns before output is complete #26399: Same root cause and symptom — stdout output truncated/invalid JSON when piping opencode commands to jq due to process.exit() before stdout drains.

   If this is indeed the same underlying bug, consider adding details or a +1 to #26399 instead.
3. blain3white commented on Jun 9, 2026

   

   blain3white

   on Jun 9, 2026

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   As a workaround while this is fixed: I authored Clean My Agent, which reads the session database directly rather than going through the CLI export — not affected by the pipe truncation issue for large sessions.
4. jornado commented on Jul 29, 2026

   

   jornado

   on Jul 29, 2026

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   The process.exit() explanation in this thread doesn't hold up. Removing the process.exit() from src/index.ts entirely and waiting 2s still truncated at exactly 65536.

   What's actually happening is backpressure. process.stdout.write() returns false once the pipe buffer is full, and the queued remainder is dropped when the process exits. console.log does the same and gives you nothing to await.

   That explains why #3049 didn't fix it: it moved export to process.stdout.write but never waited for the write to be accepted, so the second half of the problem was still there.

   It also affects opencode db and opencode session list --format json, not just export. Repro that needs no existing session:

   Q="with recursive t(n) as (select 1 union all select n+1 from t where n < 5000)
      select n as n, '0123456789012345678901234567890123456789' as pad from t"
   
   opencode db --format json "$Q" | wc -c        # 65536
   opencode db --format json "$Q" > f; wc -c f   # 388896

   Exit code is 0 both times. Worth flagging for TSV specifically: truncated output still parses, so a consumer just sees a smaller table and no error.

   Opened #39577 with a fix (await drain, EPIPE resolves so | head still works).

   One separate thing I hit while narrowing this down, which may be a Bun bug rather than ours: console.log drops everything past 64 KiB once @babel/core is in the module graph, even on a natural exit with no process.exit() involved. packages/opencode/bunfig.toml preloads @opentui/solid/preload, which pulls in Babel.

   bun add @babel/core
   echo 'console.log("x".repeat(200000))' > main.ts
   echo 'import "@babel/core"' > pre.ts
   bun main.ts | wc -c                       # 200001
   bun --preload ./pre.ts main.ts | wc -c    # 65536

   Tested on opencode 1.18.7 and dev, bun 1.3.11, macOS arm64.
5. andrescera commented on Sep 2, 2026

   

   andrescera

   on Sep 2, 2026

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   Opened #46912: it waits for the process.stdout.write callback (the way generate.ts already does) in export, session list --format json and db --format json, and treats EPIPE as done. Repro numbers are in the PR.
6. andrescera

   added 3 commits that reference this issue on Sep 24, 2026

   fix(opencode): wait for stdout writes before exit so piped JSON is no…

   ...

   This issue will close once commit 3c38c83 is merged into the 'dev' branch.

   3c38c83

   fix(opencode): wait for stdout writes before exit so piped JSON is no…

   ...

   This issue will close once commit 5b8860a is merged into the 'dev' branch.

   5b8860a

   fix(opencode): wait for stdout writes before exit so piped JSON is no…

   ...

   This issue will close once commit 04d589d is merged into the 'dev' branch.

   04d589d
7. chenweidu666 commented on Oct 3, 2026

   

   chenweidu666

   on Oct 3, 2026

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   Another instance of this systemic issue, now with a deterministic minimal reproduction and a runtime-level root cause. Affected command: opencode api.

   • opencode version: 2.0.22
   • OS: Linux x64
   • Shell: bash

   Reproduction (opencode api)

   # A consumer that does not drain immediately -> truncated to exactly the pipe capacity
   opencode api get /openapi.json | (sleep 1; wc -c)
   # actual:   65536
   # expected: 256617
   
   # Redirecting always works
   opencode api get /openapi.json > /tmp/x.json; wc -c /tmp/x.json
   # => 256617
   
   # Under concurrent load, with a fast consumer
   for i in 1 2 3 4 5 6; do (opencode api get /openapi.json | wc -c) & done; wait
   # => 256617 256617 256617 131072 256617 256617

   The truncation point is always exactly the pipe capacity: 64 KiB (single, slow consumer) or 128 KiB (concurrent). Redirect-to-file never truncates because regular-file writes are never short.

   Root cause

   Two parts combine:

   1. packages/cli/src/commands/handlers/api.ts writes without awaiting the flush:

   const output = yield* Effect.promise(() => response.text())
   if (output) process.stdout.write(output + (output.endsWith(EOL) ? "" : EOL))

   2. packages/cli/src/index.ts:136 forces exit as soon as the handler returns:

   Effect.tap(() => Effect.sync(() => process.exit(process.exitCode ?? 0))),

   This is Bun-specific. In Bun, process.exit() discards stdout bytes that are still buffered for a pipe. Node drains stdout before exiting, so the same code is fine under Node.

   Minimal Bun repro (runtime level)

   // truncates to pipe capacity
   process.stdout.write("A".repeat(300000) + "\n"); process.exit(0)
   // => 65536
   
   // works (natural exit flushes)
   process.stdout.write("A".repeat(300000) + "\n")
   // => 300001
   
   // works (await the actual data write, then exit)
   await Bun.write(Bun.stdout, "A".repeat(300000) + "\n"); process.exit(0)
   // => 300001

   Things that do not help under Bun (all still truncate to 65536):

   // awaiting a follow-up empty write
   process.stdout.write(BIG)
   await new Promise((r) => process.stdout.write("", () => r()))
   process.exit(0)
   
   // flushing with an empty Bun.write
   process.stdout.write(BIG); await Bun.write(Bun.stdout, ""); process.exit(0)
   
   // even a delay before exiting
   process.stdout.write(BIG); await new Promise((r) => setTimeout(r, 50)); process.exit(0)

   Only a natural exit, or writing the data itself through an awaited Bun.write(Bun.stdout, ...), flushes it.

   Suggested fix

   Either:

   • stop forcing process.exit() in packages/cli/src/index.ts (assign process.exitCode and let the runtime exit, which flushes), or
   • write large output with an awaited Bun.write(Bun.stdout, ...) in api.ts and the other large-output handlers.

   Both were validated against the Bun repro above. This is the same class of failure as the export truncation reported here, so a shared stdout-write helper that awaits completion would fix all of these at once.
8. thdxr commented on Oct 11, 2026

   

   thdxr

   on Oct 11, 2026

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   Thanks for the report! OpenCode 2.0 is now out and development is focused on V2, so we're closing issues filed against OpenCode 1. Please upgrade (opencode upgrade --major, details: https://anoma.ly/notes/opencode-2-0), and if this is still relevant on 2.0, reopen this issue or open a new one with your 2.0 version.

   — from 𝕺𝖕𝖊𝖓𝕮𝖔𝖉𝖊
9. thdxr

   closed this as not plannedon Oct 11, 2026