{"record":{"id":"7b1130fefdef0408","repo":"github/copilot-sdk","slug":"failed-to-write-a-frame-to-the-in-process-runtime-7b1130","errorCode":null,"errorMessage":"Failed to write a frame to the in-process runtime connection.","messagePattern":"Failed to write a frame to the in-process runtime connection\\.","errorType":"exception","errorClass":"IOException","httpStatus":null,"severity":"critical","filePath":"java/sdk/src/main/java/com/github/copilot/ffi/FfiOutputStream.java","lineNumber":57,"sourceCode":"            throw new IndexOutOfBoundsException(\"Invalid off/len for buffer of length \" + b.length);\n        }\n        if (len == 0) {\n            return;\n        }\n\n        operationLock.lock();\n        try {\n            if (closing.get()) {\n                throw new IOException(\"The in-process runtime connection is closed.\");\n            }\n            int id = connectionId.get();\n            if (id == 0) {\n                throw new IOException(\"The in-process runtime connection is closed.\");\n            }\n\n            byte[] payload = (off == 0 && len == b.length) ? b : Arrays.copyOfRange(b, off, off + len);\n            if (!nativeBinding.connectionWrite(id, payload, payload.length)) {\n                throw new IOException(\"Failed to write a frame to the in-process runtime connection.\");\n            }\n        } finally {\n            operationLock.unlock();\n        }\n    }\n}\n","sourceCodeStart":39,"sourceCodeEnd":64,"githubUrl":"https://github.com/github/copilot-sdk/blob/cd8cf15dc3f9e762615790aaed0a771a0f392755/java/sdk/src/main/java/com/github/copilot/ffi/FfiOutputStream.java#L39-L64","documentation":"FfiOutputStream.write throws this IOException when the native binding connectionWrite(id, payload, length) returns false — the frame was not delivered to the in-process runtime. The Java side had a valid connection id, but the native layer refused or failed the write (e.g., broken pipe into the runtime, runtime shutting down, backpressure/serialization failure).","triggerScenarios":"connectionWrite returning false during a write after (or during) runtime shutdown, a crashed embedded runtime, or a native-side connection reset — even though the Java-side connectionId is nonzero and closing is false.","commonSituations":"Embedded runtime process dying mid-stream while the Java host keeps writing; oversized frames the native layer rejects; racing close on the native side with in-flight writes from multiple threads (the operationLock only serializes Java-side calls).","solutions":["Check the runtime's health/liveness before writing; detect crash and reconnect/restart the host","Retry the write once on transient failure, then fail the stream if the runtime is down","Catch this IOException and stop the producer rather than looping on a dead connection","Inspect native-side logs to confirm whether the runtime rejected the frame or the connection reset"],"exampleFix":"// before\nstream.write(frame); // throws when runtime died\n// after\ntry {\n    stream.write(frame);\n} catch (IOException e) {\n    if (String.valueOf(e.getMessage()).contains(\"Failed to write a frame\")) {\n        host.restart();\n    } else {\n        throw e;\n    }\n}","handlingStrategy":"retry","validationCode":"// health-check the runtime before writing\nif (!host.isRuntimeAlive()) { host.restart(); }","typeGuard":null,"tryCatchPattern":"try {\n    stream.write(data);\n} catch (IOException e) {\n    if (String.valueOf(e.getMessage()).contains(\"Failed to write a frame\")) {\n        host.restart();\n        // single retry, then give up\n    } else throw e;\n}","preventionTips":["Monitor the embedded runtime process health","Bound frame sizes to what the native layer accepts","Stop producers after the first frame-write failure","Capture native-side logs to diagnose delivery failures"],"tags":["io","ffi","native","network"],"backgroundTag":"broken-pipe","analyzedSha":"cd8cf15dc3f9e762615790aaed0a771a0f392755","analyzedAt":"2026-09-09T18:32:31.973Z","contentChangedAt":"2026-09-09T18:32:31.973Z","schemaVersion":2},"datasetVersion":"2026-09-15T23:17:13.987Z"}