diff --git a/packages/plugins/plugin-missions/src/mission-runtime.ts b/packages/plugins/plugin-missions/src/mission-runtime.ts
index 763949e6723..4619805009b 100644
--- a/packages/plugins/plugin-missions/src/mission-runtime.ts
+++ b/packages/plugins/plugin-missions/src/mission-runtime.ts
@@ -487,20 +487,33 @@ async function appendDecisionLog(
   ctx: PluginContext,
   companyId: string,
   issueId: string,
-  existingBody: string,
   entry: { marker: string; body: string },
 ) {
-  const nextBody = appendDecisionLogEntry(existingBody, entry);
-  if (nextBody === existingBody.trim()) return nextBody;
-  await ctx.issues.documents.upsert({
-    issueId,
-    companyId,
-    key: "decision-log",
-    title: "Decision Log",
-    body: nextBody,
-    changeSummary: "Recorded mission decision",
-  });
-  return nextBody;
+  for (let attempt = 0; attempt < 2; attempt += 1) {
+    const existing = await ctx.issues.documents.get(issueId, "decision-log", companyId);
+    const existingBody = existing?.body ?? "";
+    const nextBody = appendDecisionLogEntry(existingBody, entry);
+    if (nextBody === existingBody.trim()) return nextBody;
+
+    try {
+      await ctx.issues.documents.upsert({
+        issueId,
+        companyId,
+        key: "decision-log",
+        title: "Decision Log",
+        body: nextBody,
+        changeSummary: "Recorded mission decision",
+        baseRevisionId: existing?.latestRevisionId ?? null,
+      });
+      return nextBody;
+    } catch (error) {
+      const message = stringifyError(error);
+      if (attempt === 0 && message.includes("updated by someone else")) continue;
+      throw error;
+    }
+  }
+
+  throw new Error("Unable to append mission decision log entry");
 }
 
 async function ensureFixIssue(
@@ -590,7 +603,7 @@ export async function advanceMission(
     actorRunId: input.actorRunId ?? null,
   };
   const actorLabel = buildActorLabel(actor);
-  const { mission, summary, featuresDocument, decisionLogBody } = await buildSummaryInternal(
+  const { mission, summary, featuresDocument } = await buildSummaryInternal(
     ctx,
     input.companyId,
     input.issueId,
@@ -626,7 +639,6 @@ export async function advanceMission(
       ctx,
       input.companyId,
       input.issueId,
-      decisionLogBody,
       buildMissionEventEntry({
         markerKey: `advance:paused:${stopReason}:${summary.latestValidationRound}`,
         title: `Advance Paused ${summary.missionIdentifier ?? input.issueId}`,
@@ -655,13 +667,11 @@ export async function advanceMission(
     createdFixIssues.push(fixIssue);
   }
 
-  let decisionLogBodyAfterFixes = decisionLogBody;
   if (createdFixIssues.length > 0) {
-    decisionLogBodyAfterFixes = await appendDecisionLog(
+    await appendDecisionLog(
       ctx,
       input.companyId,
       input.issueId,
-      decisionLogBodyAfterFixes,
       buildMissionEventEntry({
         markerKey: `advance:fixes:${createdFixIssues.map((issue) => issue.id).join(",")}`,
         title: `Advance Created Fixes ${summary.missionIdentifier ?? input.issueId}`,
@@ -699,7 +709,6 @@ export async function advanceMission(
       ctx,
       input.companyId,
       input.issueId,
-      decisionLogBodyAfterFixes,
       buildMissionEventEntry({
         markerKey: `advance:wakeup:${wokenIssueIds.join(",")}`,
         title: `Advance Woke Issues ${summary.missionIdentifier ?? input.issueId}`,
@@ -765,7 +774,7 @@ export async function waiveMissionFinding(
     actorRunId: input.actorRunId ?? null,
   };
   const actorLabel = buildActorLabel(actor);
-  const { summary, decisionLogBody } = await buildSummaryInternal(ctx, input.companyId, input.issueId);
+  const { summary } = await buildSummaryInternal(ctx, input.companyId, input.issueId);
   const finding = summary.findings.find((candidate) => candidate.id === input.findingId);
   if (!finding) {
     throw new Error(`Mission finding not found: ${input.findingId}`);
@@ -778,7 +787,7 @@ export async function waiveMissionFinding(
     actorLabel,
     createdAt,
   });
-  await appendDecisionLog(ctx, input.companyId, input.issueId, decisionLogBody, waiverEntry);
+  await appendDecisionLog(ctx, input.companyId, input.issueId, waiverEntry);
   await ctx.state.set(
     { scopeKind: "issue", scopeId: input.issueId, stateKey: `waiver:${input.findingId}` },
     {
diff --git a/packages/plugins/plugin-missions/tests/plugin.spec.ts b/packages/plugins/plugin-missions/tests/plugin.spec.ts
index 7192dc1396f..184614e6279 100644
--- a/packages/plugins/plugin-missions/tests/plugin.spec.ts
+++ b/packages/plugins/plugin-missions/tests/plugin.spec.ts
@@ -527,6 +527,19 @@ describe("missions plugin worker", () => {
       });
     }
 
+    const originalUpsert = harness.ctx.issues.documents.upsert;
+    const documentUpdates: Array<{ key: string; baseRevisionId: string | null | undefined }> = [];
+    harness.ctx.issues.documents.upsert = async (input) => {
+      const existing = await harness.ctx.issues.documents.get(input.issueId, input.key, input.companyId);
+      if (existing && input.baseRevisionId !== existing.latestRevisionId) {
+        throw new Error(
+          input.baseRevisionId ? "Document was updated by someone else" : "Document update requires baseRevisionId",
+        );
+      }
+      documentUpdates.push({ key: input.key, baseRevisionId: input.baseRevisionId });
+      return originalUpsert(input);
+    };
+
     const first = await harness.performAction<{ createdFixIssueIds: string[] }>("advance", {
       companyId,
       issueId: rootIssueId,
@@ -542,12 +555,35 @@ describe("missions plugin worker", () => {
     const generated = await harness.ctx.issues.list({ companyId, limit: 50 });
     expect(generated.filter((item) => item.originKind === "plugin:paperclip.missions:fix")).toHaveLength(1);
 
-    await expect(harness.performAction("waive", {
+    const summaryResponse = await plugin.definition.onApiRequest?.({
+      routeKey: "summary",
+      method: "GET",
+      path: `/issues/${rootIssueId}/missions/summary`,
+      params: { issueId: rootIssueId },
+      query: {},
+      body: null,
+      actor: { actorType: "agent", actorId: workerAgentId, agentId: workerAgentId, runId: "run-test" },
       companyId,
-      issueId: rootIssueId,
-      findingId: "FINDING-MISSION-001",
-      rationale: "Accepted temporarily for test coverage.",
-    })).resolves.toMatchObject({
+      headers: {},
+    });
+    expect(summaryResponse?.body).toMatchObject({
+      validationSummary: expect.objectContaining({
+        findings: [expect.objectContaining({ id: "FINDING-MISSION-001", computedStatus: "fix_created" })],
+      }),
+    });
+
+    const waiverResponse = await plugin.definition.onApiRequest?.({
+      routeKey: "waive",
+      method: "POST",
+      path: `/issues/${rootIssueId}/missions/findings/FINDING-MISSION-001/waive`,
+      params: { issueId: rootIssueId, findingKey: "FINDING-MISSION-001" },
+      query: {},
+      body: { rationale: "Accepted temporarily for test coverage." },
+      actor: { actorType: "agent", actorId: workerAgentId, agentId: workerAgentId, runId: "run-test" },
+      companyId,
+      headers: {},
+    });
+    expect(waiverResponse?.body).toMatchObject({
       findingId: "FINDING-MISSION-001",
       waived: true,
     });
@@ -555,5 +591,10 @@ describe("missions plugin worker", () => {
     const decisionLog = await harness.ctx.issues.documents.get(rootIssueId, "decision-log", companyId);
     expect(decisionLog?.body).toContain("paperclip:mission-finding-waiver:FINDING-MISSION-001");
     expect(decisionLog?.body).toContain("Accepted temporarily for test coverage.");
+    expect(documentUpdates.filter((update) => update.key === "decision-log")).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({ baseRevisionId: expect.any(String) }),
+      ]),
+    );
   });
 });
diff --git a/packages/plugins/sdk/src/protocol.ts b/packages/plugins/sdk/src/protocol.ts
index dc325452076..5b4c13d4566 100644
--- a/packages/plugins/sdk/src/protocol.ts
+++ b/packages/plugins/sdk/src/protocol.ts
@@ -776,6 +776,7 @@ export interface WorkerToHostMethods {
       title?: string;
       format?: string;
       changeSummary?: string;
+      baseRevisionId?: string | null;
     },
     result: IssueDocument,
   ];
diff --git a/packages/plugins/sdk/src/types.ts b/packages/plugins/sdk/src/types.ts
index 367905a1ded..ca66e580b25 100644
--- a/packages/plugins/sdk/src/types.ts
+++ b/packages/plugins/sdk/src/types.ts
@@ -878,7 +878,7 @@ export interface PluginIssueDocumentsClient {
    *
    * Requires the `issue.documents.write` capability.
    *
-   * @param input - Document data including issueId, key, body, and optional title/format/changeSummary
+   * @param input - Document data including issueId, key, body, and optional title/format/changeSummary/baseRevisionId
    */
   upsert(input: {
     issueId: string;
@@ -888,6 +888,7 @@ export interface PluginIssueDocumentsClient {
     title?: string;
     format?: string;
     changeSummary?: string;
+    baseRevisionId?: string | null;
   }): Promise<IssueDocument>;
 
   /**
diff --git a/packages/plugins/sdk/src/worker-rpc-host.ts b/packages/plugins/sdk/src/worker-rpc-host.ts
index 3f1f5a9d057..426028cbf9e 100644
--- a/packages/plugins/sdk/src/worker-rpc-host.ts
+++ b/packages/plugins/sdk/src/worker-rpc-host.ts
@@ -775,6 +775,7 @@ export function startWorkerRpcHost(options: WorkerRpcHostOptions): WorkerRpcHost
               title: input.title,
               format: input.format,
               changeSummary: input.changeSummary,
+              baseRevisionId: input.baseRevisionId,
             });
           },
 
diff --git a/server/src/services/plugin-host-services.ts b/server/src/services/plugin-host-services.ts
index 9976e04cfc0..8ea55e83dda 100644
--- a/server/src/services/plugin-host-services.ts
+++ b/server/src/services/plugin-host-services.ts
@@ -1558,6 +1558,7 @@ export function buildHostServices(
           title: params.title ?? null,
           format: params.format ?? "markdown",
           changeSummary: params.changeSummary ?? null,
+          baseRevisionId: params.baseRevisionId ?? null,
         });
         await logPluginActivity({
           companyId,