diff --git a/src/hooks/start-work/session-plan-affinity.ts b/src/hooks/start-work/session-plan-affinity.ts
new file mode 100644
index 000000000..9ba14c291
--- /dev/null
+++ b/src/hooks/start-work/session-plan-affinity.ts
@@ -0,0 +1,92 @@
+import { isAbsolute, resolve } from "node:path"
+import type { PluginInput } from "@opencode-ai/plugin"
+import { normalizeSDKResponse } from "../../shared"
+import { log } from "../../shared/logger"
+
+const PLAN_PATH_PATTERN = /[A-Za-z0-9_./\\:-]*\.sisyphus[\\/]plans[\\/][A-Za-z0-9._/\\-]+\.md/gi
+
+interface SessionMessagePart {
+  text?: string
+  output?: string
+  input?: Record<string, unknown>
+}
+
+interface SessionMessage {
+  parts?: SessionMessagePart[]
+}
+
+function normalizePlanPath(directory: string, candidate: string): string {
+  const trimmedCandidate = candidate.trim().replace(/^["'`]+|["'`]+$/g, "")
+  if (isAbsolute(trimmedCandidate) || /^[A-Za-z]:[\\/]/.test(trimmedCandidate)) {
+    return resolve(trimmedCandidate)
+  }
+
+  return resolve(directory, trimmedCandidate)
+}
+
+function extractPlanPathsFromText(directory: string, text: string): string[] {
+  const matches = text.match(PLAN_PATH_PATTERN) ?? []
+  return matches.map((match) => normalizePlanPath(directory, match))
+}
+
+function extractPlanPathsFromInput(directory: string, input: Record<string, unknown> | undefined): string[] {
+  if (!input) {
+    return []
+  }
+
+  const directCandidates = [input.filePath, input.path, input.file]
+    .filter((value): value is string => typeof value === "string")
+    .flatMap((value) => extractPlanPathsFromText(directory, value))
+
+  if (directCandidates.length > 0) {
+    return directCandidates
+  }
+
+  return extractPlanPathsFromText(directory, JSON.stringify(input))
+}
+
+export async function findRecentSessionPlanPath(input: {
+  client: PluginInput["client"]
+  directory: string
+  sessionID: string
+  availablePlans: string[]
+}): Promise<string | null> {
+  if (typeof input.client.session?.messages !== "function") {
+    return null
+  }
+
+  const availablePlans = new Set(input.availablePlans.map((planPath) => resolve(planPath)))
+  if (availablePlans.size === 0) {
+    return null
+  }
+
+  try {
+    const response = await input.client.session.messages({ path: { id: input.sessionID } })
+    const messages = normalizeSDKResponse(response, [] as SessionMessage[])
+
+    for (let messageIndex = messages.length - 1; messageIndex >= 0; messageIndex -= 1) {
+      const parts = messages[messageIndex]?.parts ?? []
+
+      for (let partIndex = parts.length - 1; partIndex >= 0; partIndex -= 1) {
+        const part = parts[partIndex]
+        const planCandidates = [
+          ...extractPlanPathsFromText(input.directory, part.text ?? ""),
+          ...extractPlanPathsFromText(input.directory, part.output ?? ""),
+          ...extractPlanPathsFromInput(input.directory, part.input),
+        ]
+
+        const matchedPlan = planCandidates.find((planPath) => availablePlans.has(resolve(planPath)))
+        if (matchedPlan) {
+          return resolve(matchedPlan)
+        }
+      }
+    }
+  } catch (error) {
+    log("[start-work] Failed to inspect session history for preferred plan", {
+      sessionID: input.sessionID,
+      error: String(error),
+    })
+  }
+
+  return null
+}
diff --git a/src/hooks/start-work/start-work-hook.ts b/src/hooks/start-work/start-work-hook.ts
index ec8a5011b..8a1d7c2b5 100644
--- a/src/hooks/start-work/start-work-hook.ts
+++ b/src/hooks/start-work/start-work-hook.ts
@@ -20,6 +20,7 @@ import { detectWorktreePath } from "./worktree-detector"
 import { parseUserRequest } from "./parse-user-request"
 import { buildStartWorkContextInfo } from "./context-info-builder"
 import { createWorktreeActiveBlock } from "./worktree-block"
+import { findRecentSessionPlanPath } from "./session-plan-affinity"
 
 export const HOOK_NAME = "start-work" as const
 const START_WORK_TEMPLATE_MARKER = "You are starting a Sisyphus work session."
@@ -93,6 +94,14 @@ export function createStartWorkHook(ctx: PluginInput) {
 
     const { planName: explicitPlanName, explicitWorktreePath } = parseUserRequest(promptText)
     const { worktreePath, block: worktreeBlock } = resolveWorktreeContext(explicitWorktreePath)
+    const preferredPlanPath = explicitPlanName
+      ? null
+      : await findRecentSessionPlanPath({
+          client: ctx.client,
+          directory: ctx.directory,
+          sessionID: sessionId,
+          availablePlans: findPrometheusPlans(ctx.directory),
+        })
 
     const contextInfo = buildStartWorkContextInfo({
       ctx,
@@ -103,6 +112,7 @@ export function createStartWorkHook(ctx: PluginInput) {
       activeAgent,
       worktreePath,
       worktreeBlock,
+      preferredPlanPath,
     })
 
     const idx = output.parts.findIndex((p) => p.type === "text" && p.text)
@@ -114,11 +124,12 @@ export function createStartWorkHook(ctx: PluginInput) {
       output.parts[idx].text += `\n\n---\n${contextInfo}`
     }
 
-    log(`[${HOOK_NAME}] Context injected`, {
-      sessionID: input.sessionID,
-      hasExistingState: !!existingState,
-      worktreePath,
-    })
+      log(`[${HOOK_NAME}] Context injected`, {
+        sessionID: input.sessionID,
+        hasExistingState: !!existingState,
+        preferredPlanPath,
+        worktreePath,
+      })
   }
 
   return {