0.1.29

fix: reattach to orphaned K8s Jobs across Paperclip restarts (FAR-124)

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "paperclip-adapter-claude-k8s",
-  "version": "0.1.27",
+  "version": "0.1.29",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "paperclip-adapter-claude-k8s",
-      "version": "0.1.27",
+      "version": "0.1.29",
       "license": "MIT",
       "dependencies": {
         "@kubernetes/client-node": "^1.0.0",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "paperclip-adapter-claude-k8s",
-  "version": "0.1.27",
+  "version": "0.1.29",
   "description": "Paperclip adapter plugin that runs Claude Code agents as Kubernetes Jobs",
   "license": "MIT",
   "repository": {

src/server/config-schema.test.ts

@@ -42,6 +42,14 @@ describe("getConfigSchema", () => {
     expect(field!.default).toBe(true);
   });
 
+  it("reattachOrphanedJobs defaults to true", () => {
+    const schema = getConfigSchema();
+    const field = schema.fields.find((f: ConfigFieldSchema) => f.key === "reattachOrphanedJobs");
+    expect(field).toBeDefined();
+    expect(field!.type).toBe("toggle");
+    expect(field!.default).toBe(true);
+  });
+
   it("has imagePullPolicy as select with correct options", () => {
     const schema = getConfigSchema();
     const field = schema.fields.find((f: ConfigFieldSchema) => f.key === "imagePullPolicy");

src/server/config-schema.ts

@@ -89,6 +89,13 @@ export function getConfigSchema(): AdapterConfigSchema {
       label: "Retain Jobs",
       hint: "Skip cleanup of completed Jobs for debugging purposes.",
     },
+    {
+      type: "toggle",
+      key: "reattachOrphanedJobs",
+      label: "Reattach to Orphaned Jobs",
+      hint: "If a prior K8s Job for the same agent/task/session is still running (e.g. Paperclip restarted mid-run), attach to it and stream its output instead of deleting it and starting a new pod. Default: on.",
+      default: true,
+    },
     // Resource Limits
     {
       type: "text",

src/server/execute.test.ts

@@ -0,0 +1,188 @@
+import { describe, it, expect } from "vitest";
+import type * as k8s from "@kubernetes/client-node";
+import { isK8s404, buildPartialRunError, isReattachableOrphan } from "./execute.js";
+
+function makeJob(opts: {
+  runId?: string;
+  agentId?: string;
+  taskId?: string;
+  sessionId?: string;
+  adapterType?: string;
+  terminal?: boolean;
+}): k8s.V1Job {
+  const labels: Record<string, string> = {
+    "paperclip.io/adapter-type": opts.adapterType ?? "claude_k8s",
+  };
+  if (opts.agentId) labels["paperclip.io/agent-id"] = opts.agentId;
+  if (opts.runId) labels["paperclip.io/run-id"] = opts.runId;
+  if (opts.taskId) labels["paperclip.io/task-id"] = opts.taskId;
+  if (opts.sessionId) labels["paperclip.io/session-id"] = opts.sessionId;
+  return {
+    metadata: { name: "ac-job", namespace: "paperclip", labels },
+    status: opts.terminal
+      ? { conditions: [{ type: "Complete", status: "True" }] }
+      : { conditions: [] },
+  } as k8s.V1Job;
+}
+
+describe("isK8s404", () => {
+  it("returns false for non-Error values", () => {
+    expect(isK8s404(null)).toBe(false);
+    expect(isK8s404(undefined)).toBe(false);
+    expect(isK8s404("string error")).toBe(false);
+    expect(isK8s404(404)).toBe(false);
+  });
+
+  it("returns false for unrelated errors", () => {
+    expect(isK8s404(new Error("something went wrong"))).toBe(false);
+    expect(isK8s404(new Error("HTTP-Code: 500 Message: Internal Server Error"))).toBe(false);
+  });
+
+  it("detects 404 from v1.0+ message format", () => {
+    const err = new Error("HTTP-Code: 404 Message: Unknown API Status Code! Body: ...");
+    expect(isK8s404(err)).toBe(true);
+  });
+
+  it("detects 404 from v0.x response.statusCode", () => {
+    const err = Object.assign(new Error("Not Found"), {
+      response: { statusCode: 404 },
+    });
+    expect(isK8s404(err)).toBe(true);
+  });
+
+  it("detects 404 from v1.0+ response.status", () => {
+    const err = Object.assign(new Error("Not Found"), {
+      response: { status: 404 },
+    });
+    expect(isK8s404(err)).toBe(true);
+  });
+
+  it("detects 404 from direct statusCode property", () => {
+    const err = Object.assign(new Error("Not Found"), { statusCode: 404 });
+    expect(isK8s404(err)).toBe(true);
+  });
+
+  it("does not match non-404 status codes on response", () => {
+    const err = Object.assign(new Error("Forbidden"), {
+      response: { statusCode: 403 },
+    });
+    expect(isK8s404(err)).toBe(false);
+  });
+});
+
+describe("buildPartialRunError", () => {
+  const initLine = JSON.stringify({
+    type: "system",
+    subtype: "init",
+    model: "claude-sonnet-4-6",
+    session_id: "sess_abc",
+  });
+
+  it("returns parse-failure message when exitCode is 0", () => {
+    expect(buildPartialRunError(0, "", "")).toBe("Failed to parse Claude JSON output");
+    expect(buildPartialRunError(0, "claude-sonnet-4-6", initLine)).toBe(
+      "Failed to parse Claude JSON output",
+    );
+  });
+
+  it("returns generic exit message when stdout is empty", () => {
+    expect(buildPartialRunError(1, "", "")).toBe("Claude exited with code 1");
+    expect(buildPartialRunError(null, "", "")).toBe("Claude exited with code -1");
+  });
+
+  it("skips system/init events and returns generic message when only init captured", () => {
+    const msg = buildPartialRunError(1, "claude-sonnet-4-6", initLine);
+    expect(msg).toBe(
+      "Claude started but did not produce a result (model: claude-sonnet-4-6) — check API credentials, model support, and adapter config",
+    );
+  });
+
+  it("includes model from parsedStream when stdout is init-only", () => {
+    const msg = buildPartialRunError(null, "MiniMax-M2.7", initLine);
+    expect(msg).toContain("MiniMax-M2.7");
+    expect(msg).not.toContain("type");
+    expect(msg).not.toContain("system");
+  });
+
+  it("uses first non-system line as content when present", () => {
+    const stdout = [initLine, "Error: no API key configured"].join("\n");
+    const msg = buildPartialRunError(1, "claude-sonnet-4-6", stdout);
+    expect(msg).toBe("Claude exited with code 1: Error: no API key configured");
+  });
+
+  it("uses first non-system JSON event as content", () => {
+    const resultLike = JSON.stringify({ type: "result", subtype: "error", result: "rate limit" });
+    const stdout = [initLine, resultLike].join("\n");
+    const msg = buildPartialRunError(2, "claude-sonnet-4-6", stdout);
+    expect(msg).toContain("rate limit");
+    expect(msg).toContain("code 2");
+  });
+
+  it("null exitCode renders as -1 in message", () => {
+    const msg = buildPartialRunError(null, "", "Some plain error text");
+    expect(msg).toBe("Claude exited with code -1: Some plain error text");
+  });
+
+  it("skips multiple consecutive system events", () => {
+    const anotherSystem = JSON.stringify({ type: "system", subtype: "other" });
+    const stdout = [initLine, anotherSystem, "real error line"].join("\n");
+    const msg = buildPartialRunError(1, "model-x", stdout);
+    expect(msg).toBe("Claude exited with code 1: real error line");
+  });
+});
+
+describe("isReattachableOrphan", () => {
+  const agentId = "agent-abc";
+  const taskId = "task-xyz";
+  const sessionId = "sess-123";
+
+  it("returns true when agent/task/session all match and Job is not terminal", () => {
+    const job = makeJob({ agentId, taskId, sessionId, runId: "old-run" });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(true);
+  });
+
+  it("returns false when the Job is already Complete", () => {
+    const job = makeJob({ agentId, taskId, sessionId, runId: "old-run", terminal: true });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+
+  it("returns false when expected taskId is null (caller couldn't derive one)", () => {
+    const job = makeJob({ agentId, taskId, sessionId });
+    expect(isReattachableOrphan(job, { agentId, taskId: null, sessionId })).toBe(false);
+  });
+
+  it("returns false when expected sessionId is null", () => {
+    const job = makeJob({ agentId, taskId, sessionId });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId: null })).toBe(false);
+  });
+
+  it("returns false when agent id doesn't match", () => {
+    const job = makeJob({ agentId: "agent-other", taskId, sessionId });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+
+  it("returns false when task id doesn't match", () => {
+    const job = makeJob({ agentId, taskId: "task-other", sessionId });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+
+  it("returns false when session id doesn't match", () => {
+    const job = makeJob({ agentId, taskId, sessionId: "sess-other" });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+
+  it("returns false when the Job is from a different adapter type", () => {
+    const job = makeJob({ agentId, taskId, sessionId, adapterType: "claude_local" });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+
+  it("returns false when Job has no task-id label (labels were introduced in FAR-124)", () => {
+    const job = makeJob({ agentId, sessionId });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+
+  it("returns false when Job has no session-id label", () => {
+    const job = makeJob({ agentId, taskId });
+    expect(isReattachableOrphan(job, { agentId, taskId, sessionId })).toBe(false);
+  });
+});

src/server/execute.ts

@@ -7,7 +7,8 @@ import {
   isClaudeUnknownSessionError,
 } from "./parse.js";
 import { getSelfPodInfo, getBatchApi, getCoreApi, getLogApi } from "./k8s-client.js";
-import { buildJobManifest } from "./job-manifest.js";
+import { buildJobManifest, sanitizeLabelValue } from "./job-manifest.js";
+import { LogLineDedupFilter } from "./log-dedup.js";
 import type * as k8s from "@kubernetes/client-node";
 import { Writable } from "node:stream";
 
@@ -19,8 +20,9 @@ const MAX_LOG_RECONNECT_ATTEMPTS = 50;
 /**
  * Detect a Kubernetes 404 (Not Found) error from @kubernetes/client-node.
  * Works for both v0.x (response.statusCode) and v1.0+ (response.status, message).
+ * Exported for unit tests.
  */
-function isK8s404(err: unknown): boolean {
+export function isK8s404(err: unknown): boolean {
   if (!(err instanceof Error)) return false;
   const e = err as unknown as Record<string, unknown>;
   const resp = e.response as Record<string, unknown> | undefined;
@@ -29,6 +31,71 @@ function isK8s404(err: unknown): boolean {
   return /HTTP-Code:\s*404\b/.test(err.message);
 }
 
+/**
+ * Build the error message when Claude's stdout contains no result event.
+ * Skips system/init event lines so the UI doesn't display the raw init JSON.
+ * Exported for unit tests.
+ */
+export function buildPartialRunError(
+  exitCode: number | null,
+  model: string,
+  stdout: string,
+): string {
+  if (exitCode === 0) return "Failed to parse Claude JSON output";
+
+  // Walk stdout lines, skip system events, return the first real content line.
+  const firstContentLine = stdout.split(/\r?\n/)
+    .map((l) => l.trim())
+    .find((l) => {
+      if (!l) return false;
+      try {
+        const obj = JSON.parse(l);
+        if (typeof obj === "object" && obj !== null && (obj as Record<string, unknown>).type === "system") return false;
+      } catch {
+        // not JSON — treat as content
+      }
+      return true;
+    }) ?? "";
+
+  // If we only have system/init events and nothing else, surface the model
+  // name so the operator can diagnose missing credentials or unsupported model.
+  const initOnlyOutput = stdout.trim() !== "" && model !== "" && !firstContentLine;
+  if (initOnlyOutput) {
+    const modelHint = model ? ` (model: ${model})` : "";
+    return `Claude started but did not produce a result${modelHint} — check API credentials, model support, and adapter config`;
+  }
+
+  return firstContentLine
+    ? `Claude exited with code ${exitCode ?? -1}: ${firstContentLine}`
+    : `Claude exited with code ${exitCode ?? -1}`;
+}
+
+/**
+ * Evaluate an orphaned K8s Job (one whose `paperclip.io/run-id` label does
+ * not match the current runId) as a potential reattach target.  A Job is
+ * reattachable when it belongs to the same agent, same task, and same resume
+ * session as the current run — meaning the previous Paperclip instance was
+ * mid-stream on the exact piece of work this new run was dispatched to do.
+ * Exported for unit tests.
+ */
+export function isReattachableOrphan(
+  job: k8s.V1Job,
+  expected: { agentId: string; taskId: string | null; sessionId: string | null },
+): boolean {
+  if (!expected.taskId || !expected.sessionId) return false;
+  const labels = job.metadata?.labels ?? {};
+  if (labels["paperclip.io/adapter-type"] !== "claude_k8s") return false;
+  if (labels["paperclip.io/agent-id"] !== expected.agentId) return false;
+  if (labels["paperclip.io/task-id"] !== expected.taskId) return false;
+  if (labels["paperclip.io/session-id"] !== expected.sessionId) return false;
+  const conditions = job.status?.conditions ?? [];
+  const terminal = conditions.some(
+    (c) => (c.type === "Complete" || c.type === "Failed") && c.status === "True",
+  );
+  if (terminal) return false;
+  return true;
+}
+
 /**
  * Wait for the Job's pod to reach a terminal or running state.
  * Returns the pod name once logs can be streamed, or throws on failure.
@@ -150,6 +217,7 @@ async function streamPodLogsOnce(
   onLog: AdapterExecutionContext["onLog"],
   kubeconfigPath?: string,
   sinceSeconds?: number,
+  dedup?: LogLineDedupFilter,
 ): Promise<string> {
   const logApi = getLogApi(kubeconfigPath);
   const chunks: string[] = [];
@@ -158,7 +226,12 @@ async function streamPodLogsOnce(
     write(chunk: Buffer, _encoding, callback) {
       const text = chunk.toString("utf-8");
       chunks.push(text);
-      void onLog("stdout", text).then(() => callback(), callback);
+      const emitted = dedup ? dedup.filter(text) : text;
+      if (!emitted) {
+        callback();
+        return;
+      }
+      void onLog("stdout", emitted).then(() => callback(), callback);
     },
   });
 
@@ -198,6 +271,9 @@ async function streamPodLogs(
   // reconnects use a tight window instead of an ever-growing one anchored
   // at stream start.  This is the primary fix for FAR-105 duplicative logs.
   let lastLogReceivedAt = Math.floor(Date.now() / 1000);
+  // Shared across reconnects so replayed lines inside the `sinceSeconds`
+  // overlap window are dropped before they reach the streaming UI (FAR-123).
+  const dedup = new LogLineDedupFilter();
 
   while (!stopSignal?.stopped) {
     if (attempt >= MAX_LOG_RECONNECT_ATTEMPTS) {
@@ -217,7 +293,7 @@ async function streamPodLogs(
     }
 
     const preStreamTs = Math.floor(Date.now() / 1000);
-    const result = await streamPodLogsOnce(namespace, podName, onLog, kubeconfigPath, sinceSeconds);
+    const result = await streamPodLogsOnce(namespace, podName, onLog, kubeconfigPath, sinceSeconds, dedup);
     if (result) {
       allChunks.push(result);
       // Update last-received timestamp to now (the stream just ended,
@@ -237,6 +313,11 @@ async function streamPodLogs(
     await new Promise((resolve) => setTimeout(resolve, LOG_STREAM_RECONNECT_DELAY_MS));
   }
 
+  // Flush any buffered partial line so the final assistant/result chunk
+  // isn't dropped when the stream ends mid-line.
+  const tail = dedup.flush();
+  if (tail) await onLog("stdout", tail);
+
   return allChunks.join("");
 }
 
@@ -356,10 +437,18 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
   // Guard: claude_k8s must not run concurrently for the same agent (shared PVC/session).
   // After a server restart, orphaned K8s Jobs from previous (now-failed) runs may
   // still be running.  We detect those by comparing the Job's run-id label against
-  // the current runId and clean them up so this execution can proceed.
+  // the current runId.  When reattachOrphanedJobs is enabled and the orphan matches
+  // the current agent+task+session, we attach to it instead of deleting it (FAR-124).
   const agentId = ctx.agent.id;
   const selfPod = await getSelfPodInfo(kubeconfigPath);
   const guardNamespace = asString(config.namespace, "") || selfPod.namespace;
+  const reattachOrphanedJobs = asBoolean(config.reattachOrphanedJobs, true);
+  const runtimeSessionParams = parseObject(runtime.sessionParams);
+  const currentSessionIdRaw = asString(runtimeSessionParams.sessionId, runtime.sessionId ?? "");
+  const currentSessionLabel = currentSessionIdRaw ? sanitizeLabelValue(currentSessionIdRaw) : null;
+  const currentTaskIdRaw = asString(ctx.context.taskId, "") || asString(ctx.context.issueId, "");
+  const currentTaskLabel = currentTaskIdRaw ? sanitizeLabelValue(currentTaskIdRaw) : null;
+  let reattachTarget: { jobName: string; namespace: string; priorRunId: string; image: string } | null = null;
   try {
     const batchApi = getBatchApi(kubeconfigPath);
     const existing = await batchApi.listNamespacedJob({
@@ -379,10 +468,42 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
         (j) => (j.metadata?.labels?.["paperclip.io/run-id"] ?? "") === runId,
       );
 
-      if (orphaned.length > 0) {
-        const orphanNames = orphaned.map((j) => j.metadata?.name).join(", ");
-        await onLog("stdout", `[paperclip] Cleaning up ${orphaned.length} orphaned K8s Job(s) from previous run(s): ${orphanNames}\n`);
-        for (const j of orphaned) {
+      // Pick the most recent reattachable orphan — same agent + task + session,
+      // not terminal.  Only one target is chosen; any other orphans get
+      // cleaned up as before.
+      if (reattachOrphanedJobs && orphaned.length > 0) {
+        const candidates = orphaned
+          .filter((j) =>
+            isReattachableOrphan(j, {
+              agentId,
+              taskId: currentTaskLabel,
+              sessionId: currentSessionLabel,
+            }),
+          )
+          .sort((a, b) => {
+            const at = new Date(a.metadata?.creationTimestamp ?? 0).getTime();
+            const bt = new Date(b.metadata?.creationTimestamp ?? 0).getTime();
+            return bt - at;
+          });
+        const chosen = candidates[0];
+        const chosenName = chosen?.metadata?.name;
+        if (chosen && chosenName) {
+          reattachTarget = {
+            jobName: chosenName,
+            namespace: chosen.metadata?.namespace ?? guardNamespace,
+            priorRunId: chosen.metadata?.labels?.["paperclip.io/run-id"] ?? "",
+            image: chosen.spec?.template?.spec?.containers?.[0]?.image ?? "unknown",
+          };
+        }
+      }
+
+      const toDelete = orphaned.filter(
+        (j) => !reattachTarget || j.metadata?.name !== reattachTarget.jobName,
+      );
+      if (toDelete.length > 0) {
+        const orphanNames = toDelete.map((j) => j.metadata?.name).join(", ");
+        await onLog("stdout", `[paperclip] Cleaning up ${toDelete.length} orphaned K8s Job(s) from previous run(s): ${orphanNames}\n`);
+        for (const j of toDelete) {
           const name = j.metadata?.name;
           if (name) {
             await cleanupJob(guardNamespace, name, onLog, kubeconfigPath);
@@ -420,84 +541,120 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
     };
   }
 
-  // Build Job manifest
-  const { job, jobName, namespace, prompt, claudeArgs, promptMetrics, promptSecret } = buildJobManifest({
-    ctx,
-    selfPod,
-  });
-
-  // Report invocation metadata
-  if (onMeta) {
-    await onMeta({
-      adapterType: "claude_k8s",
-      command: `kubectl job/${jobName}`,
-      cwd: namespace,
-      commandArgs: claudeArgs,
-      commandNotes: [
-        `Image: ${job.spec?.template.spec?.containers[0]?.image ?? "unknown"}`,
-        `Namespace: ${namespace}`,
-        `Timeout: ${timeoutSec}s`,
-      ],
-      prompt,
-      ...(promptMetrics ? { promptMetrics } : {}),
-      context: ctx.context,
-    } as Parameters<typeof onMeta>[0]);
-  }
-
-  // If the prompt is large, create a Secret to hold it (avoids the ~1 MiB
-  // PodSpec limit).  The Secret is cleaned up in the finally block.
   const coreApi = getCoreApi(kubeconfigPath);
-  if (promptSecret) {
-    try {
-      await coreApi.createNamespacedSecret({
-        namespace: promptSecret.namespace,
-        body: {
-          apiVersion: "v1",
-          kind: "Secret",
-          metadata: {
-            name: promptSecret.name,
-            namespace: promptSecret.namespace,
-            labels: {
-              "app.kubernetes.io/managed-by": "paperclip",
-              "paperclip.io/adapter-type": "claude_k8s",
-              "paperclip.io/run-id": runId,
+  const batchApi = getBatchApi(kubeconfigPath);
+
+  let jobName: string;
+  let namespace: string;
+  let promptSecret: { name: string; namespace: string; data: Record<string, string> } | null = null;
+
+  if (reattachTarget) {
+    jobName = reattachTarget.jobName;
+    namespace = reattachTarget.namespace;
+
+    // Announce reattach metadata.  Prompt and args aren't known here — they
+    // belong to the prior run that created this pod and are already present
+    // on the running container.
+    if (onMeta) {
+      await onMeta({
+        adapterType: "claude_k8s",
+        command: `kubectl job/${jobName}`,
+        cwd: namespace,
+        commandArgs: [],
+        commandNotes: [
+          `Image: ${reattachTarget.image}`,
+          `Namespace: ${namespace}`,
+          `Reattached from prior run: ${reattachTarget.priorRunId || "unknown"}`,
+          `Timeout: ${timeoutSec}s`,
+        ],
+        prompt: "",
+        context: ctx.context,
+      } as Parameters<typeof onMeta>[0]);
+    }
+
+    await onLog("stdout", `[paperclip] Reattaching to in-flight K8s Job ${jobName} in namespace ${namespace} (prior run ${reattachTarget.priorRunId || "unknown"})\n`);
+  } else {
+    // Build Job manifest
+    const built = buildJobManifest({ ctx, selfPod });
+    const job = built.job;
+    jobName = built.jobName;
+    namespace = built.namespace;
+    const prompt = built.prompt;
+    const claudeArgs = built.claudeArgs;
+    const promptMetrics = built.promptMetrics;
+    promptSecret = built.promptSecret;
+
+    // Report invocation metadata
+    if (onMeta) {
+      await onMeta({
+        adapterType: "claude_k8s",
+        command: `kubectl job/${jobName}`,
+        cwd: namespace,
+        commandArgs: claudeArgs,
+        commandNotes: [
+          `Image: ${job.spec?.template.spec?.containers[0]?.image ?? "unknown"}`,
+          `Namespace: ${namespace}`,
+          `Timeout: ${timeoutSec}s`,
+        ],
+        prompt,
+        ...(promptMetrics ? { promptMetrics } : {}),
+        context: ctx.context,
+      } as Parameters<typeof onMeta>[0]);
+    }
+
+    // If the prompt is large, create a Secret to hold it (avoids the ~1 MiB
+    // PodSpec limit).  The Secret is cleaned up in the finally block.
+    if (promptSecret) {
+      try {
+        await coreApi.createNamespacedSecret({
+          namespace: promptSecret.namespace,
+          body: {
+            apiVersion: "v1",
+            kind: "Secret",
+            metadata: {
+              name: promptSecret.name,
+              namespace: promptSecret.namespace,
+              labels: {
+                "app.kubernetes.io/managed-by": "paperclip",
+                "paperclip.io/adapter-type": "claude_k8s",
+                "paperclip.io/run-id": runId,
+              },
             },
+            stringData: promptSecret.data,
           },
-          stringData: promptSecret.data,
-        },
-      });
-      await onLog("stdout", `[paperclip] Created prompt Secret: ${promptSecret.name} (${Math.round(Buffer.byteLength(prompt, "utf-8") / 1024)} KiB)\n`);
+        });
+        await onLog("stdout", `[paperclip] Created prompt Secret: ${promptSecret.name} (${Math.round(Buffer.byteLength(prompt, "utf-8") / 1024)} KiB)\n`);
+      } catch (err) {
+        const msg = err instanceof Error ? err.message : String(err);
+        await onLog("stderr", `[paperclip] Failed to create prompt Secret: ${msg}\n`);
+        return {
+          exitCode: null,
+          signal: null,
+          timedOut: false,
+          errorMessage: `Failed to create prompt Secret: ${msg}`,
+          errorCode: "k8s_prompt_secret_create_failed",
+        };
+      }
+    }
+
+    // Create the Job
+    try {
+      await batchApi.createNamespacedJob({ namespace, body: job });
     } catch (err) {
       const msg = err instanceof Error ? err.message : String(err);
-      await onLog("stderr", `[paperclip] Failed to create prompt Secret: ${msg}\n`);
+      await onLog("stderr", `[paperclip] Failed to create K8s Job: ${msg}\n`);
       return {
         exitCode: null,
         signal: null,
         timedOut: false,
-        errorMessage: `Failed to create prompt Secret: ${msg}`,
-        errorCode: "k8s_prompt_secret_create_failed",
+        errorMessage: `Failed to create Kubernetes Job: ${msg}`,
+        errorCode: "k8s_job_create_failed",
       };
     }
-  }
 
-  // Create the Job
-  const batchApi = getBatchApi(kubeconfigPath);
-  try {
-    await batchApi.createNamespacedJob({ namespace, body: job });
-  } catch (err) {
-    const msg = err instanceof Error ? err.message : String(err);
-    await onLog("stderr", `[paperclip] Failed to create K8s Job: ${msg}\n`);
-    return {
-      exitCode: null,
-      signal: null,
-      timedOut: false,
-      errorMessage: `Failed to create Kubernetes Job: ${msg}`,
-      errorCode: "k8s_job_create_failed",
-    };
+    await onLog("stdout", `[paperclip] Created K8s Job: ${jobName} in namespace ${namespace} (deadline: ${timeoutSec > 0 ? `${timeoutSec}s` : "none"})\n`);
   }
 
-  await onLog("stdout", `[paperclip] Created K8s Job: ${jobName} in namespace ${namespace} (deadline: ${timeoutSec > 0 ? `${timeoutSec}s` : "none"})\n`);
-
   let stdout = "";
   let exitCode: number | null = null;
   let jobTimedOut = false;
@@ -511,8 +668,23 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
     const scheduleTimeoutMs = 120_000; // 2 minutes for scheduling
     let podName: string;
     try {
-      podName = await waitForPod(namespace, jobName, scheduleTimeoutMs, onLog, kubeconfigPath);
-      await onLog("stdout", `[paperclip] Pod running: ${podName}\n`);
+      if (reattachTarget) {
+        // Pod is already running from the prior run — look it up directly.
+        const podList = await coreApi.listNamespacedPod({
+          namespace,
+          labelSelector: `job-name=${jobName}`,
+        });
+        const pod = podList.items[0];
+        const name = pod?.metadata?.name;
+        if (!name) {
+          throw new Error(`Reattach target Job ${jobName} has no pod`);
+        }
+        podName = name;
+        await onLog("stdout", `[paperclip] Reattached to pod ${podName}\n`);
+      } else {
+        podName = await waitForPod(namespace, jobName, scheduleTimeoutMs, onLog, kubeconfigPath);
+        await onLog("stdout", `[paperclip] Pod running: ${podName}\n`);
+      }
 
       // Notify the server that execution has started.  This sets
       // processStartedAt and refreshes updatedAt in the DB, which the
@@ -526,13 +698,14 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
       }
     } catch (err) {
       const msg = err instanceof Error ? err.message : String(err);
-      await onLog("stderr", `[paperclip] Pod scheduling failed: ${msg}\n`);
+      const phase = reattachTarget ? "reattach" : "scheduling";
+      await onLog("stderr", `[paperclip] Pod ${phase} failed: ${msg}\n`);
       return {
         exitCode: null,
         signal: null,
         timedOut: false,
-        errorMessage: `Pod scheduling failed: ${msg}`,
-        errorCode: "k8s_pod_schedule_failed",
+        errorMessage: `Pod ${phase} failed: ${msg}`,
+        errorCode: reattachTarget ? "k8s_pod_reattach_failed" : "k8s_pod_schedule_failed",
       };
     }
 
@@ -640,13 +813,27 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
       stdout = logResult.value;
     }
 
-    // If the follow stream missed output (container exited quickly), do a
-    // one-shot log read as fallback before the pod is cleaned up.
-    if (!stdout.trim()) {
-      await onLog("stdout", `[paperclip] Log stream returned empty — reading pod logs directly...\n`);
-      stdout = await readPodLogs(namespace, podName, kubeconfigPath);
-      if (stdout.trim()) {
+    // One-shot log fallback: handles two failure modes with a single read.
+    // Mode 1 — empty stream: the follow stream returned nothing (fast exit before connection).
+    // Mode 2 — partial stream: we have some output but no result event (follow stream raced
+    //   with container exit and captured only the init line before the connection dropped).
+    // A one-shot readPodLogs is more reliable for already-terminated containers and reads
+    // from the beginning of the log, giving us the full output.
+    // We use a cheap string scan for the result-event guard (avoids a full JSON parse here;
+    // the authoritative parse happens once below after all fallbacks complete).
+    const hasResultEvent = stdout.includes('"type":"result"');
+    const needsOneShot = !stdout.trim() || (stdout.trim() && !hasResultEvent);
+    if (needsOneShot) {
+      if (!stdout.trim()) {
+        await onLog("stdout", `[paperclip] Log stream returned empty — reading pod logs directly...\n`);
+      }
+      const oneShotLogs = await readPodLogs(namespace, podName, kubeconfigPath);
+      if (!stdout.trim() && oneShotLogs.trim()) {
+        stdout = oneShotLogs;
         await onLog("stdout", stdout);
+      } else if (oneShotLogs && oneShotLogs.length > stdout.length) {
+        await onLog("stdout", `[paperclip] Log stream captured partial output — supplemental one-shot read returned more content.\n`);
+        stdout = oneShotLogs;
       }
     }
 
@@ -739,16 +926,11 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
   }
 
   if (!parsed) {
-    const stderrLine = stdout.split(/\r?\n/).map((l) => l.trim()).find(Boolean) ?? "";
     return {
       exitCode,
       signal: null,
       timedOut: false,
-      errorMessage: exitCode === 0
-        ? "Failed to parse Claude JSON output"
-        : stderrLine
-          ? `Claude exited with code ${exitCode ?? -1}: ${stderrLine}`
-          : `Claude exited with code ${exitCode ?? -1}`,
+      errorMessage: buildPartialRunError(exitCode, parsedStream.model, stdout),
       resultJson: { stdout },
     };
   }
@@ -762,8 +944,7 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
     };
   })();
 
-  const runtimeSessionParams = parseObject(runtime.sessionParams);
-  const fallbackSessionId = asString(runtimeSessionParams.sessionId, runtime.sessionId ?? "");
+  const fallbackSessionId = currentSessionIdRaw;
   const resolvedSessionId = parsedStream.sessionId
     ?? (asString(parsed.session_id as string, fallbackSessionId) || fallbackSessionId);
   const model = asString(config.model, "");

src/server/job-manifest.test.ts

@@ -1,6 +1,6 @@
 import { describe, it, expect, beforeEach } from "vitest";
 import type { AdapterExecutionContext } from "@paperclipai/adapter-utils";
-import { buildJobManifest, buildRtkSetupCommands } from "./job-manifest.js";
+import { buildJobManifest, buildRtkSetupCommands, sanitizeLabelValue } from "./job-manifest.js";
 import type { SelfPodInfo } from "./k8s-client.js";
 
 function makeCtx(overrides: Partial<AdapterExecutionContext> = {}): AdapterExecutionContext {
@@ -136,6 +136,36 @@ describe("buildJobManifest", () => {
       expect(job.metadata?.labels?.env).toBe("prod");
       expect(job.metadata?.labels?.["paperclip.io/adapter-type"]).toBe("claude_k8s");
     });
+
+    it("adds task-id label when context provides taskId", () => {
+      ctx.context = { taskId: "task-xyz-789" };
+      const { job } = buildJobManifest({ ctx, selfPod });
+      expect(job.metadata?.labels?.["paperclip.io/task-id"]).toBe("task-xyz-789");
+    });
+
+    it("falls back to issueId when taskId absent", () => {
+      ctx.context = { issueId: "issue-42" };
+      const { job } = buildJobManifest({ ctx, selfPod });
+      expect(job.metadata?.labels?.["paperclip.io/task-id"]).toBe("issue-42");
+    });
+
+    it("adds session-id label when runtime provides sessionId", () => {
+      ctx.runtime = { ...ctx.runtime, sessionId: "sess-abc-1234" };
+      const { job } = buildJobManifest({ ctx, selfPod });
+      expect(job.metadata?.labels?.["paperclip.io/session-id"]).toBe("sess-abc-1234");
+    });
+
+    it("reads sessionId from runtime.sessionParams when sessionId prop missing", () => {
+      ctx.runtime = { ...ctx.runtime, sessionParams: { sessionId: "sess-from-params" } };
+      const { job } = buildJobManifest({ ctx, selfPod });
+      expect(job.metadata?.labels?.["paperclip.io/session-id"]).toBe("sess-from-params");
+    });
+
+    it("omits task-id and session-id labels when neither is provided", () => {
+      const { job } = buildJobManifest({ ctx, selfPod });
+      expect(job.metadata?.labels?.["paperclip.io/task-id"]).toBeUndefined();
+      expect(job.metadata?.labels?.["paperclip.io/session-id"]).toBeUndefined();
+    });
   });
 
   describe("annotations", () => {
@@ -729,3 +759,32 @@ describe("buildJobManifest", () => {
     });
   });
 });
+
+describe("sanitizeLabelValue", () => {
+  it("passes through already-valid UUIDs and slugs", () => {
+    expect(sanitizeLabelValue("abc-123-def")).toBe("abc-123-def");
+    expect(sanitizeLabelValue("0d8b4472-c42c-4052-aab1-e32897909afa")).toBe("0d8b4472-c42c-4052-aab1-e32897909afa");
+  });
+
+  it("strips characters outside [a-zA-Z0-9._-]", () => {
+    expect(sanitizeLabelValue("task:xyz/123")).toBe("taskxyz123");
+    expect(sanitizeLabelValue("abc 123")).toBe("abc123");
+  });
+
+  it("trims leading/trailing non-alphanumeric characters", () => {
+    expect(sanitizeLabelValue("--abc--")).toBe("abc");
+    expect(sanitizeLabelValue("...123...")).toBe("123");
+  });
+
+  it("truncates to the configured maxLen", () => {
+    const long = "a".repeat(200);
+    const out = sanitizeLabelValue(long, 63);
+    expect(out?.length).toBe(63);
+  });
+
+  it("returns null when no alphanumeric characters remain", () => {
+    expect(sanitizeLabelValue("---")).toBeNull();
+    expect(sanitizeLabelValue("")).toBeNull();
+    expect(sanitizeLabelValue("   ")).toBeNull();
+  });
+});

src/server/job-manifest.ts

@@ -202,6 +202,17 @@ function sanitizeForK8sName(value: string, maxLen = 16): string {
   return value.toLowerCase().replace(/[^a-z0-9-]/g, "").slice(0, maxLen);
 }
 
+/**
+ * Sanitize a string for use as a Kubernetes label value (RFC 1123 subset:
+ * `[a-zA-Z0-9]([-_.a-zA-Z0-9]*[a-zA-Z0-9])?`, max 63 chars).  Returns `null`
+ * when no usable characters remain — the caller should omit the label.
+ */
+export function sanitizeLabelValue(value: string, maxLen = 63): string | null {
+  const cleaned = value.replace(/[^a-zA-Z0-9._-]/g, "").slice(0, maxLen);
+  const trimmed = cleaned.replace(/^[^a-zA-Z0-9]+/, "").replace(/[^a-zA-Z0-9]+$/, "");
+  return trimmed.length > 0 ? trimmed : null;
+}
+
 /**
  * Build a short deterministic hash suffix from the raw inputs to avoid
  * collisions when sanitized slugs happen to be identical.
@@ -428,6 +439,15 @@ export function buildJobManifest(input: JobBuildInput): JobBuildResult {
     "paperclip.io/company-id": agent.companyId,
     "paperclip.io/adapter-type": "claude_k8s",
   };
+  // Reattach-target labels: let a future execute() identify this Job as the
+  // continuation of the same logical unit of work (same task + same resume
+  // session) so it can attach to the running pod across a Paperclip restart
+  // instead of deleting it and starting over (FAR-124).
+  const taskIdRaw = asString(context.taskId, "") || asString(context.issueId, "");
+  const taskLabel = taskIdRaw ? sanitizeLabelValue(taskIdRaw) : null;
+  if (taskLabel) labels["paperclip.io/task-id"] = taskLabel;
+  const sessionLabel = runtimeSessionId ? sanitizeLabelValue(runtimeSessionId) : null;
+  if (sessionLabel) labels["paperclip.io/session-id"] = sessionLabel;
   for (const [key, value] of Object.entries(extraLabels)) {
     labels[key] = value;
   }

src/server/log-dedup.test.ts

@@ -0,0 +1,173 @@
+import { describe, it, expect } from "vitest";
+import { LogLineDedupFilter, eventDedupKey } from "./log-dedup.js";
+
+function assistantEvent(id: string, text: string): string {
+  return JSON.stringify({
+    type: "assistant",
+    session_id: "sess_1",
+    message: {
+      id,
+      content: [{ type: "text", text }],
+    },
+  });
+}
+
+function userToolResultEvent(toolUseId: string, content: string): string {
+  return JSON.stringify({
+    type: "user",
+    session_id: "sess_1",
+    message: {
+      content: [{ type: "tool_result", tool_use_id: toolUseId, content }],
+    },
+  });
+}
+
+function systemInitEvent(sessionId: string): string {
+  return JSON.stringify({
+    type: "system",
+    subtype: "init",
+    session_id: sessionId,
+    model: "claude-opus-4-7",
+  });
+}
+
+function resultEvent(sessionId: string): string {
+  return JSON.stringify({
+    type: "result",
+    subtype: "success",
+    session_id: sessionId,
+    result: "done",
+    total_cost_usd: 0.01,
+    usage: { input_tokens: 1, output_tokens: 1, cache_read_input_tokens: 0 },
+  });
+}
+
+describe("eventDedupKey", () => {
+  it("keys assistant events by message.id", () => {
+    const key = eventDedupKey(JSON.parse(assistantEvent("msg_abc", "hi")));
+    expect(key).toBe("assistant:msg_abc");
+  });
+
+  it("keys user tool_result events by tool_use_id", () => {
+    const key = eventDedupKey(JSON.parse(userToolResultEvent("toolu_1", "ok")));
+    expect(key).toBe("user:tool_result:toolu_1");
+  });
+
+  it("keys system init events by session_id", () => {
+    const key = eventDedupKey(JSON.parse(systemInitEvent("sess_xyz")));
+    expect(key).toBe("system:init:sess_xyz");
+  });
+
+  it("keys result events by session_id", () => {
+    const key = eventDedupKey(JSON.parse(resultEvent("sess_xyz")));
+    expect(key).toBe("result:sess_xyz");
+  });
+
+  it("returns null for assistant events missing message.id", () => {
+    const event = { type: "assistant", message: { content: [] } };
+    expect(eventDedupKey(event)).toBeNull();
+  });
+
+  it("returns null for unknown event types", () => {
+    expect(eventDedupKey({ type: "unknown" })).toBeNull();
+    expect(eventDedupKey({})).toBeNull();
+  });
+});
+
+describe("LogLineDedupFilter", () => {
+  it("passes unique lines through unchanged", () => {
+    const filter = new LogLineDedupFilter();
+    const a = assistantEvent("msg_1", "hello");
+    const b = assistantEvent("msg_2", "world");
+    expect(filter.filter(`${a}\n${b}\n`)).toBe(`${a}\n${b}\n`);
+  });
+
+  it("drops assistant events replayed with the same message.id", () => {
+    const filter = new LogLineDedupFilter();
+    const a = assistantEvent("msg_1", "Three nits to fix.");
+    filter.filter(`${a}\n`);
+    expect(filter.filter(`${a}\n`)).toBe("");
+  });
+
+  it("drops user tool_result events replayed with the same tool_use_id", () => {
+    const filter = new LogLineDedupFilter();
+    const a = userToolResultEvent("toolu_abc", "file contents");
+    filter.filter(`${a}\n`);
+    expect(filter.filter(`${a}\n`)).toBe("");
+  });
+
+  it("drops system init and result events on replay", () => {
+    const filter = new LogLineDedupFilter();
+    const init = systemInitEvent("sess_1");
+    const result = resultEvent("sess_1");
+    filter.filter(`${init}\n${result}\n`);
+    expect(filter.filter(`${init}\n${result}\n`)).toBe("");
+  });
+
+  it("buffers incomplete trailing lines across chunks", () => {
+    const filter = new LogLineDedupFilter();
+    const line = assistantEvent("msg_1", "hello");
+    const mid = Math.floor(line.length / 2);
+    const out1 = filter.filter(line.slice(0, mid));
+    const out2 = filter.filter(line.slice(mid) + "\n");
+    expect(out1).toBe("");
+    expect(out2).toBe(`${line}\n`);
+  });
+
+  it("flush() emits a final incomplete line that was not replayed", () => {
+    const filter = new LogLineDedupFilter();
+    const line = assistantEvent("msg_tail", "no newline");
+    filter.filter(line);
+    expect(filter.flush()).toBe(line);
+  });
+
+  it("flush() drops an incomplete line that was already seen with a newline", () => {
+    const filter = new LogLineDedupFilter();
+    const line = assistantEvent("msg_same", "x");
+    filter.filter(`${line}\n`);
+    filter.filter(line);
+    expect(filter.flush()).toBe("");
+  });
+
+  it("passes non-JSON lines through every time (does not dedup paperclip status)", () => {
+    const filter = new LogLineDedupFilter();
+    const status = "[paperclip] keepalive — job foo running\n";
+    expect(filter.filter(status)).toBe(status);
+    expect(filter.filter(status)).toBe(status);
+  });
+
+  it("dedups structurally identical JSON with identical content (raw fallback)", () => {
+    const filter = new LogLineDedupFilter();
+    // No recognized type → raw fallback key.
+    const line = JSON.stringify({ foo: "bar", baz: 1 });
+    filter.filter(`${line}\n`);
+    expect(filter.filter(`${line}\n`)).toBe("");
+  });
+
+  it("handles multiple complete lines in a single chunk with partial trailing", () => {
+    const filter = new LogLineDedupFilter();
+    const a = assistantEvent("msg_a", "a");
+    const b = assistantEvent("msg_b", "b");
+    const c = assistantEvent("msg_c", "c");
+    // a and b are complete, c is partial (no trailing newline).
+    const out = filter.filter(`${a}\n${b}\n${c}`);
+    expect(out).toBe(`${a}\n${b}\n`);
+    // Completing c later should emit exactly c.
+    expect(filter.filter("\n")).toBe(`${c}\n`);
+  });
+
+  it("drops the classic FAR-123 replay scenario across reconnects", () => {
+    const filter = new LogLineDedupFilter();
+    const assistantNits = assistantEvent("msg_nits", "Three nits to fix. Let me look at an existing test file...");
+    const assistantWrite = assistantEvent("msg_write", "Now I need to write unit tests");
+    // First stream attempt emits both events.
+    const out1 = filter.filter(`${assistantNits}\n${assistantWrite}\n`);
+    expect(out1).toBe(`${assistantNits}\n${assistantWrite}\n`);
+    // Reconnect replays both within the sinceSeconds overlap — filter should drop them.
+    const out2 = filter.filter(`${assistantNits}\n${assistantWrite}\n`);
+    expect(out2).toBe("");
+    // And a genuinely new event after the replay should still pass through.
+    const assistantFresh = assistantEvent("msg_fresh", "next turn");
+    expect(filter.filter(`${assistantFresh}\n`)).toBe(`${assistantFresh}\n`);
+  });
+});

src/server/log-dedup.ts

@@ -0,0 +1,146 @@
+/**
+ * Line-level dedup filter for the K8s log stream.
+ *
+ * The K8s log follow stream can reconnect with an overlapping `sinceSeconds`
+ * window (integer-second granularity + a safety buffer), which replays a few
+ * seconds of recent output on every reconnect. Without dedup those replayed
+ * lines appear as duplicate events in the streaming UI — the same assistant
+ * text block shows up between every subsequent tool call (FAR-123).
+ *
+ * The filter operates at the chunk → line level: chunks are split on `\n`,
+ * incomplete trailing content is buffered until the next chunk, and each
+ * complete line is emitted at most once. JSON-shaped Claude stream-json
+ * events are keyed by their stable structural IDs; non-JSON lines pass
+ * through unchanged so genuinely-repeated status lines are not swallowed.
+ */
+
+type Parsed = Record<string, unknown>;
+
+function asString(value: unknown): string {
+  return typeof value === "string" ? value : "";
+}
+
+function asRecord(value: unknown): Parsed | null {
+  if (typeof value !== "object" || value === null || Array.isArray(value)) return null;
+  return value as Parsed;
+}
+
+/**
+ * Build a stable dedup key for a Claude stream-json event.  Returns `null`
+ * when the event is not a recognized Claude event — those lines fall back to
+ * raw-content hashing so non-JSON output (paperclip status lines, shell
+ * output) is never deduped by identity.
+ */
+export function eventDedupKey(event: Parsed): string | null {
+  const type = asString(event.type);
+
+  if (type === "system") {
+    const subtype = asString(event.subtype);
+    const sessionId = asString(event.session_id);
+    if (subtype === "init" && sessionId) return `system:init:${sessionId}`;
+    return null;
+  }
+
+  if (type === "assistant") {
+    const message = asRecord(event.message);
+    const id = message ? asString(message.id) : "";
+    if (id) return `assistant:${id}`;
+    return null;
+  }
+
+  if (type === "user") {
+    const message = asRecord(event.message);
+    const content = message && Array.isArray(message.content) ? message.content : [];
+    const toolUseIds: string[] = [];
+    for (const entry of content) {
+      const block = asRecord(entry);
+      if (!block) continue;
+      const toolUseId = asString(block.tool_use_id);
+      if (toolUseId) toolUseIds.push(toolUseId);
+    }
+    if (toolUseIds.length > 0) return `user:tool_result:${toolUseIds.join(",")}`;
+    return null;
+  }
+
+  if (type === "result") {
+    const sessionId = asString(event.session_id);
+    return sessionId ? `result:${sessionId}` : "result:unknown";
+  }
+
+  return null;
+}
+
+/**
+ * Stateful line-level dedup filter.  Emits `filter(chunk)` output through
+ * the caller — preserves original chunk formatting (including trailing
+ * newlines) for lines that pass the dedup check.
+ */
+export class LogLineDedupFilter {
+  private buffer = "";
+  private readonly seenKeys = new Set<string>();
+
+  /**
+   * Process a chunk and return the subset that should be forwarded.
+   * Incomplete trailing content (no terminating newline) is buffered and
+   * emitted on the next chunk that completes the line (or on flush()).
+   */
+  filter(chunk: string): string {
+    if (!chunk) return "";
+    const combined = this.buffer + chunk;
+    const endsWithNewline = combined.endsWith("\n");
+    const parts = combined.split("\n");
+
+    if (endsWithNewline) {
+      // Discard the final empty element — last line was complete.
+      parts.pop();
+      this.buffer = "";
+    } else {
+      // Last element is an incomplete line — hold it for the next chunk.
+      this.buffer = parts.pop() ?? "";
+    }
+
+    const out: string[] = [];
+    for (const line of parts) {
+      if (this.shouldEmit(line)) out.push(line);
+    }
+    if (out.length === 0) return "";
+    return out.join("\n") + "\n";
+  }
+
+  /**
+   * Flush any incomplete trailing content.  Called when the stream ends
+   * without a terminating newline so the final partial line isn't lost.
+   */
+  flush(): string {
+    const pending = this.buffer;
+    this.buffer = "";
+    if (!pending) return "";
+    return this.shouldEmit(pending) ? pending : "";
+  }
+
+  private shouldEmit(line: string): boolean {
+    const trimmed = line.trim();
+    if (!trimmed) return true;
+
+    // Only attempt dedup on JSON-shaped lines; pass shell/text output through.
+    if (!trimmed.startsWith("{") || !trimmed.endsWith("}")) return true;
+
+    let parsed: unknown;
+    try {
+      parsed = JSON.parse(trimmed);
+    } catch {
+      return true;
+    }
+
+    const event = asRecord(parsed);
+    if (!event) return true;
+
+    // Recognized Claude stream-json event → structural key.
+    const structuralKey = eventDedupKey(event);
+    const key = structuralKey ?? `raw:${trimmed}`;
+
+    if (this.seenKeys.has(key)) return false;
+    this.seenKeys.add(key);
+    return true;
+  }
+}