diff --git a/packages/core/src/v1/config/config.ts b/packages/core/src/v1/config/config.ts
index 7ebb4b69b023..03ea98af299c 100644
--- a/packages/core/src/v1/config/config.ts
+++ b/packages/core/src/v1/config/config.ts
@@ -187,6 +187,14 @@ export const Info = Schema.Struct({
       }),
     }),
   ),
+  session: Schema.optional(
+    Schema.Struct({
+      auto_resume: Schema.optional(Schema.Boolean).annotate({
+        description:
+          "Automatically resume sessions that were active when opencode crashed (default: false)",
+      }),
+    }),
+  ).annotate({ description: "Session crash recovery configuration" }),
 }).annotate({ identifier: "Config" })
 
 export type Info = DeepMutable<Schema.Schema.Type<typeof Info>>
diff --git a/packages/opencode/src/cli/cmd/run.ts b/packages/opencode/src/cli/cmd/run.ts
index 3927f615a080..a041b520e8a5 100644
--- a/packages/opencode/src/cli/cmd/run.ts
+++ b/packages/opencode/src/cli/cmd/run.ts
@@ -18,6 +18,7 @@ import path from "path"
 import { pathToFileURL } from "url"
 import { open } from "node:fs/promises"
 import { Effect } from "effect"
+import { ActiveManifest } from "@/session/active-manifest"
 import { UI } from "../ui"
 import { effectCmd } from "../effect-cmd"
 import { EOL } from "os"
@@ -491,6 +492,30 @@ export const RunCommand = effectCmd({
 
         const base = args.continue ? (await sdk.session.list()).data?.find((item) => !item.parentID) : undefined
 
+        if (!args.continue && !args.session) {
+          const crashed = await Effect.runPromise(ActiveManifest.hasCrashed()).catch(() => false)
+          if (crashed) {
+            const cfg = await sdk.config.get().catch(() => undefined)
+            if (cfg?.data?.session?.auto_resume) {
+              const active = await Effect.runPromise(ActiveManifest.read()).catch(() => [])
+              if (active.length > 0) {
+                const candidate = active[active.length - 1]
+                const existing = await sdk.session.get({ sessionID: candidate.id }).catch(() => undefined)
+                if (existing?.data) {
+                  UI.println(UI.Style.TEXT_WARNING_BOLD + "!" + UI.Style.TEXT_NORMAL + ` crash detected — resuming last active session`)
+                  await Effect.runPromise(ActiveManifest.clear()).catch(() => {})
+                  return {
+                    id: candidate.id,
+                    title: existing.data.title,
+                    directory: existing.data.directory,
+                  }
+                }
+              }
+            }
+            await Effect.runPromise(ActiveManifest.clear()).catch(() => {})
+          }
+        }
+
         if (base && args.fork) {
           const forked = await sdk.session.fork({
             sessionID: base.id,
diff --git a/packages/opencode/src/index.ts b/packages/opencode/src/index.ts
index 13540a73a36f..8e421c1708bb 100644
--- a/packages/opencode/src/index.ts
+++ b/packages/opencode/src/index.ts
@@ -29,6 +29,8 @@ import { DbCommand } from "./cli/cmd/db"
 import { errorMessage } from "./util/error"
 import { PluginCommand } from "./cli/cmd/plug"
 import { Heap } from "./cli/heap"
+import { ActiveManifest } from "./session/active-manifest"
+import { Effect } from "effect"
 
 const args = hideBin(process.argv)
 
@@ -134,6 +136,9 @@ try {
   }
   process.exitCode = 1
 } finally {
+  // Clean shutdown: clear the active-sessions manifest so the next startup
+  // knows the previous process exited cleanly (not a crash).
+  await Effect.runPromise(ActiveManifest.clear()).catch(() => {})
   // Some subprocesses don't react properly to SIGTERM and similar signals.
   // Most notably, some docker-container-based MCP servers don't handle such signals unless
   // run using `docker run --init`.
diff --git a/packages/opencode/src/session/active-manifest.ts b/packages/opencode/src/session/active-manifest.ts
new file mode 100644
index 000000000000..feb09700d7d4
--- /dev/null
+++ b/packages/opencode/src/session/active-manifest.ts
@@ -0,0 +1,91 @@
+import path from "node:path"
+import fs from "node:fs/promises"
+import fsSync from "node:fs"
+import { Global } from "@opencode-ai/core/global"
+import { Effect } from "effect"
+
+export type ActiveSession = {
+  id: string
+  timestamp: number
+}
+
+type Manifest = { sessions: ActiveSession[] }
+
+let manifestDir = Global.Path.data
+
+export function setManifestDir(dir: string) {
+  manifestDir = dir
+}
+
+export function manifestPath() {
+  return path.join(manifestDir, "active-sessions.json")
+}
+
+// Best-effort: manifest errors must never crash the session lifecycle
+async function readRaw(): Promise<Manifest> {
+  const file = Bun.file(manifestPath())
+  if (!(await file.exists())) return { sessions: [] }
+  const parsed = await file.json().catch(() => null)
+  if (!parsed || !Array.isArray(parsed.sessions)) return { sessions: [] }
+  return { sessions: parsed.sessions }
+}
+
+async function writeRaw(manifest: Manifest): Promise<void> {
+  const tmp = manifestPath() + ".tmp"
+  await Bun.write(tmp, JSON.stringify(manifest))
+  await fs.rename(tmp, manifestPath())
+}
+
+const write = Effect.fn("ActiveManifest.write")(function* (entry: ActiveSession) {
+  yield* Effect.promise(async () => {
+    const manifest = await readRaw()
+    const without = manifest.sessions.filter((s) => s.id !== entry.id)
+    without.push(entry)
+    await writeRaw({ sessions: without })
+  })
+})
+
+const remove = Effect.fn("ActiveManifest.remove")(function* (sessionID: string) {
+  yield* Effect.promise(async () => {
+    const manifest = await readRaw()
+    const without = manifest.sessions.filter((s) => s.id !== sessionID)
+    if (without.length === 0) {
+      const file = Bun.file(manifestPath())
+      if (await file.exists()) await file.unlink()
+      return
+    }
+    await writeRaw({ sessions: without })
+  })
+})
+
+const read = Effect.fn("ActiveManifest.read")(function* () {
+  const manifest = yield* Effect.promise(() => readRaw())
+  return manifest.sessions
+})
+
+const clear = Effect.fn("ActiveManifest.clear")(function* () {
+  yield* Effect.promise(async () => {
+    const file = Bun.file(manifestPath())
+    if (await file.exists()) await file.unlink()
+  })
+})
+
+const hasCrashed = Effect.fn("ActiveManifest.hasCrashed")(function* () {
+  return yield* Effect.promise(() => Bun.file(manifestPath()).exists())
+})
+
+export const ActiveManifest = {
+  write: (entry: ActiveSession) => write(entry).pipe(Effect.catch(() => Effect.void)),
+  remove: (sessionID: string) => remove(sessionID).pipe(Effect.catch(() => Effect.void)),
+  read: () => read().pipe(Effect.catch(() => Effect.succeed([] as ActiveSession[]))),
+  clear: () => clear().pipe(Effect.catch(() => Effect.void)),
+  hasCrashed: () => hasCrashed().pipe(Effect.catch(() => Effect.succeed(false))),
+}
+
+// Synchronous cleanup on process.exit() — runs for clean exits but not for
+// SIGKILL/crashes, which is exactly the desired crash-detection behavior.
+process.on("exit", () => {
+  try {
+    fsSync.unlinkSync(manifestPath())
+  } catch {}
+})
diff --git a/packages/opencode/src/session/status.ts b/packages/opencode/src/session/status.ts
index 11140acfeef5..96a956ad21d3 100644
--- a/packages/opencode/src/session/status.ts
+++ b/packages/opencode/src/session/status.ts
@@ -4,6 +4,7 @@ import { SessionID } from "./schema"
 import { Effect, Layer, Context } from "effect"
 import { EventV2Bridge } from "@/event-v2-bridge"
 import { SessionStatusEvent } from "@opencode-ai/schema/session-status-event"
+import { ActiveManifest } from "./active-manifest"
 
 export const Info = SessionStatusEvent.Info
 export type Info = SessionStatusEvent.Info
@@ -42,9 +43,11 @@ const layer = Layer.effect(
       if (status.type === "idle") {
         yield* events.publish(Event.Idle, { sessionID })
         data.delete(sessionID)
+        yield* ActiveManifest.remove(sessionID)
         return
       }
       data.set(sessionID, status)
+      yield* ActiveManifest.write({ id: sessionID, timestamp: Date.now() })
     })
 
     return Service.of({ get, list, set })
diff --git a/packages/opencode/test/session/active-manifest.test.ts b/packages/opencode/test/session/active-manifest.test.ts
new file mode 100644
index 000000000000..8f7c2a1aeeca
--- /dev/null
+++ b/packages/opencode/test/session/active-manifest.test.ts
@@ -0,0 +1,156 @@
+import { expect, test } from "bun:test"
+import { Effect } from "effect"
+import fs from "fs/promises"
+import os from "os"
+import path from "path"
+import { ActiveManifest, setManifestDir } from "@/session/active-manifest"
+
+const sampleEntry = {
+  id: "session-001",
+  timestamp: Date.now(),
+}
+
+async function withTmpDir(fn: (dir: string) => Promise<void>) {
+  const dir = path.join(os.tmpdir(), "opencode-test-" + Math.random().toString(36).slice(2))
+  await fs.mkdir(dir, { recursive: true })
+  try {
+    await fn(dir)
+  } finally {
+    await fs.rm(dir, { recursive: true, force: true })
+  }
+}
+
+test("writeActiveSession creates manifest with session", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(1)
+    expect(sessions[0].id).toBe("session-001")
+  })
+})
+
+test("writeActiveSession adds to existing manifest", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    await Effect.runPromise(
+      ActiveManifest.write({
+        id: "session-002",
+        timestamp: Date.now(),
+      }),
+    )
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(2)
+  })
+})
+
+test("writeActiveSession updates existing session", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    await Effect.runPromise(ActiveManifest.write({ ...sampleEntry, timestamp: 999 }))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(1)
+    expect(sessions[0].timestamp).toBe(999)
+  })
+})
+
+test("removeActiveSession removes from manifest", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    await Effect.runPromise(ActiveManifest.remove("session-001"))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(0)
+  })
+})
+
+test("removeActiveSession deletes manifest file when last session removed", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    await Effect.runPromise(ActiveManifest.remove("session-001"))
+    const crashed = await Effect.runPromise(ActiveManifest.hasCrashed())
+    expect(crashed).toBe(false)
+  })
+})
+
+test("clearActiveSessions deletes the manifest file", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    await Effect.runPromise(ActiveManifest.clear())
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(0)
+  })
+})
+
+test("hasCrashed returns false when no manifest exists", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    const crashed = await Effect.runPromise(ActiveManifest.hasCrashed())
+    expect(crashed).toBe(false)
+  })
+})
+
+test("hasCrashed returns true when manifest exists", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    const crashed = await Effect.runPromise(ActiveManifest.hasCrashed())
+    expect(crashed).toBe(true)
+  })
+})
+
+test("read returns empty array when manifest does not exist", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(0)
+  })
+})
+
+test("read returns empty array for valid-but-wrong-shape JSON", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    const manifestPath = path.join(dir, "active-sessions.json")
+    await fs.writeFile(manifestPath, JSON.stringify({}))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(0)
+  })
+})
+
+test("read returns empty array for valid array JSON", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    const manifestPath = path.join(dir, "active-sessions.json")
+    await fs.writeFile(manifestPath, JSON.stringify([]))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(0)
+  })
+})
+
+test("write after corrupt-shape manifest recovers gracefully", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    const manifestPath = path.join(dir, "active-sessions.json")
+    await fs.writeFile(manifestPath, JSON.stringify({ sessions: "not-an-array" }))
+    await Effect.runPromise(ActiveManifest.write(sampleEntry))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(1)
+    expect(sessions[0].id).toBe("session-001")
+  })
+})
+
+test("multi-session manifest preserves write order", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+    await Effect.runPromise(ActiveManifest.write({ id: "s1", timestamp: 1000 }))
+    await Effect.runPromise(ActiveManifest.write({ id: "s2", timestamp: 2000 }))
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(2)
+    expect(sessions[0].id).toBe("s1")
+    expect(sessions[sessions.length - 1].id).toBe("s2")
+  })
+})
diff --git a/packages/opencode/test/session/crash-recovery-e2e.test.ts b/packages/opencode/test/session/crash-recovery-e2e.test.ts
new file mode 100644
index 000000000000..64ee7277f5ba
--- /dev/null
+++ b/packages/opencode/test/session/crash-recovery-e2e.test.ts
@@ -0,0 +1,111 @@
+import { expect, test } from "bun:test"
+import { Effect } from "effect"
+import fs from "fs/promises"
+import os from "os"
+import path from "path"
+import { ActiveManifest, setManifestDir } from "@/session/active-manifest"
+
+async function withTmpDir(fn: (dir: string) => Promise<void>) {
+  const dir = path.join(os.tmpdir(), "opencode-e2e-" + Math.random().toString(36).slice(2))
+  await fs.mkdir(dir, { recursive: true })
+  try {
+    await fn(dir)
+  } finally {
+    await fs.rm(dir, { recursive: true, force: true })
+  }
+}
+
+test("E2E: crash leaves manifest, clean shutdown clears it", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+
+    // 1. Simulate sessions going busy
+    await Effect.runPromise(ActiveManifest.write({ id: "s1", timestamp: Date.now() }))
+    await Effect.runPromise(ActiveManifest.write({ id: "s2", timestamp: Date.now() }))
+
+    // 2. Crash: manifest should persist
+    const afterCrash = await Effect.runPromise(ActiveManifest.read())
+    expect(afterCrash).toHaveLength(2)
+    const crashed = await Effect.runPromise(ActiveManifest.hasCrashed())
+    expect(crashed).toBe(true)
+
+    // 3. Simulate one session going idle
+    await Effect.runPromise(ActiveManifest.remove("s1"))
+    const afterIdle = await Effect.runPromise(ActiveManifest.read())
+    expect(afterIdle).toHaveLength(1)
+    expect(afterIdle[0].id).toBe("s2")
+
+    // 4. Simulate last session going idle
+    await Effect.runPromise(ActiveManifest.remove("s2"))
+    const afterLastIdle = await Effect.runPromise(ActiveManifest.read())
+    expect(afterLastIdle).toHaveLength(0)
+
+    // 5. After all sessions idle, manifest file should be deleted
+    const fileExists = await Effect.runPromise(ActiveManifest.hasCrashed())
+    expect(fileExists).toBe(false)
+  })
+})
+
+test("E2E: crash with multiple sessions, then clean shutdown clears all", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+
+    // 1. Multiple sessions active
+    await Effect.runPromise(ActiveManifest.write({ id: "s1", timestamp: Date.now() }))
+    await Effect.runPromise(ActiveManifest.write({ id: "s2", timestamp: Date.now() }))
+    await Effect.runPromise(ActiveManifest.write({ id: "s3", timestamp: Date.now() }))
+
+    // 2. Crash — manifest persists with all sessions
+    expect(await Effect.runPromise(ActiveManifest.hasCrashed())).toBe(true)
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(3)
+
+    // 3. Clean shutdown — manifest cleared
+    await Effect.runPromise(ActiveManifest.clear())
+    expect(await Effect.runPromise(ActiveManifest.hasCrashed())).toBe(false)
+    expect(await Effect.runPromise(ActiveManifest.read())).toHaveLength(0)
+  })
+})
+
+test("E2E: manifest survives corrupt JSON (graceful degradation)", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+
+    // Write corrupt JSON to manifest file
+    const manifestPath = path.join(dir, "active-sessions.json")
+    await fs.writeFile(manifestPath, "{ broken json")
+
+    // Read should return empty array, not throw
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(0)
+
+    // hasCrashed should still return true (file exists)
+    expect(await Effect.runPromise(ActiveManifest.hasCrashed())).toBe(true)
+
+    // After clear, file is gone
+    await Effect.runPromise(ActiveManifest.clear())
+    expect(await Effect.runPromise(ActiveManifest.hasCrashed())).toBe(false)
+  })
+})
+
+test("E2E: write-update cycle preserves only latest entry per session", async () => {
+  await withTmpDir(async (dir) => {
+    setManifestDir(dir)
+
+    // Write session with timestamp T1
+    await Effect.runPromise(ActiveManifest.write({ id: "s1", timestamp: 1000 }))
+
+    // Update same session with timestamp T2
+    await Effect.runPromise(ActiveManifest.write({ id: "s1", timestamp: 2000 }))
+
+    // Should have only one entry with latest timestamp
+    const sessions = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions).toHaveLength(1)
+    expect(sessions[0].timestamp).toBe(2000)
+
+    // Write a second session
+    await Effect.runPromise(ActiveManifest.write({ id: "s2", timestamp: 3000 }))
+    const sessions2 = await Effect.runPromise(ActiveManifest.read())
+    expect(sessions2).toHaveLength(2)
+  })
+})