diff --git a/lib/hooks.ts b/lib/hooks.ts
index 6d6f3862..1e9edc07 100644
--- a/lib/hooks.ts
+++ b/lib/hooks.ts
@@ -36,7 +36,13 @@ import {
 } from "./commands"
 import { type HostPermissionSnapshot } from "./host-permissions"
 import { compressPermission, syncCompressPermissionState } from "./compress-permission"
-import { checkSession, ensureSessionInitialized, saveSessionState, syncToolCache } from "./state"
+import {
+    checkSession,
+    deleteSessionState,
+    ensureSessionInitialized,
+    saveSessionState,
+    syncToolCache,
+} from "./state"
 import { cacheSystemPromptTokens } from "./ui/utils"
 
 const INTERNAL_AGENT_SIGNATURES = [
@@ -300,6 +306,19 @@ export function createTextCompleteHandler() {
 
 export function createEventHandler(state: SessionState, logger: Logger) {
     return async (input: { event: any }) => {
+        // Deleting a session leaves its persisted prune state behind forever,
+        // and the orphan still counts towards the all-time stats (#557).
+        if (input.event?.type === "session.deleted") {
+            const deletedSessionId = input.event.properties?.info?.id
+            if (typeof deletedSessionId === "string" && deletedSessionId.length > 0) {
+                await deleteSessionState(deletedSessionId, logger)
+                if (state.sessionId === deletedSessionId) {
+                    state.sessionId = null
+                }
+            }
+            return
+        }
+
         const eventTime =
             typeof input.event?.time === "number" && Number.isFinite(input.event.time)
                 ? input.event.time
diff --git a/lib/state/persistence.ts b/lib/state/persistence.ts
index 882e7dad..92600afe 100644
--- a/lib/state/persistence.ts
+++ b/lib/state/persistence.ts
@@ -252,6 +252,15 @@ export async function saveManualModeSetting(
     await writePersistedSessionState(sessionId, state, logger)
 }
 
+export async function deleteSessionState(sessionId: string, logger: Logger): Promise<void> {
+    try {
+        await fs.unlink(getSessionFilePath(sessionId))
+        logger.debug("Removed state file for deleted session", { sessionId })
+    } catch {
+        // The file may never have been written, or may already be gone.
+    }
+}
+
 export interface AggregatedStats {
     totalTokens: number
     totalTools: number
diff --git a/tests/session-cleanup.test.ts b/tests/session-cleanup.test.ts
new file mode 100644
index 00000000..25508167
--- /dev/null
+++ b/tests/session-cleanup.test.ts
@@ -0,0 +1,117 @@
+import assert from "node:assert/strict"
+import test from "node:test"
+import { existsSync, readdirSync, rmSync, writeFileSync } from "node:fs"
+import { join } from "node:path"
+import { mkdtempSync } from "node:fs"
+import { tmpdir } from "node:os"
+
+const root = mkdtempSync(join(tmpdir(), "dcp-session-delete-"))
+process.env.XDG_DATA_HOME = join(root, "data")
+process.env.XDG_CONFIG_HOME = join(root, "config")
+process.env.OPENCODE_CONFIG_DIR = join(root, "config", "opencode")
+
+const { Logger } = await import("../lib/logger")
+const { createSessionState, saveSessionState } = await import("../lib/state")
+const { createEventHandler } = await import("../lib/hooks")
+
+const logger = new Logger(false)
+const STORAGE_DIR = join(root, "data/opencode/storage/plugin/dcp")
+
+test.after(() => rmSync(root, { recursive: true, force: true }))
+
+// A deleted session used to leave its state file on disk forever, and the orphan
+// kept contributing to the all-time stats (#557).
+test("deleting a session removes its persisted state file", async () => {
+    const sessionId = `ses_delete_${Date.now()}`
+    const state = createSessionState()
+    state.sessionId = sessionId
+    state.stats.totalPruneTokens = 12_345
+    await saveSessionState(state, logger)
+
+    const filePath = join(STORAGE_DIR, `${sessionId}.json`)
+    assert.ok(existsSync(filePath), "precondition: the state file was written")
+
+    const handler = createEventHandler(state, logger)
+    await handler({ event: { type: "session.deleted", properties: { info: { id: sessionId } } } })
+
+    assert.equal(existsSync(filePath), false, "the orphaned state file survived")
+})
+
+test("deleting another session leaves the active one intact", async () => {
+    const keep = `ses_keep_${Date.now()}`
+    const drop = `ses_drop_${Date.now()}`
+    const state = createSessionState()
+    state.sessionId = keep
+    await saveSessionState(state, logger)
+
+    const dropState = createSessionState()
+    dropState.sessionId = drop
+    await saveSessionState(dropState, logger)
+
+    const handler = createEventHandler(state, logger)
+    await handler({ event: { type: "session.deleted", properties: { info: { id: drop } } } })
+
+    assert.ok(existsSync(join(STORAGE_DIR, `${keep}.json`)))
+    assert.equal(existsSync(join(STORAGE_DIR, `${drop}.json`)), false)
+    assert.equal(state.sessionId, keep)
+})
+
+test("deleting the active session detaches the in-memory state", async () => {
+    const sessionId = `ses_active_${Date.now()}`
+    const state = createSessionState()
+    state.sessionId = sessionId
+    await saveSessionState(state, logger)
+
+    const handler = createEventHandler(state, logger)
+    await handler({ event: { type: "session.deleted", properties: { info: { id: sessionId } } } })
+
+    assert.equal(state.sessionId, null)
+})
+
+test("a delete event for an unknown session is harmless", async () => {
+    const state = createSessionState()
+    state.sessionId = "ses_current"
+    const handler = createEventHandler(state, logger)
+
+    await handler({ event: { type: "session.deleted", properties: {} } })
+    await handler({ event: { type: "session.deleted" } })
+    await handler({ event: { type: "session.deleted", properties: { info: { id: "" } } } })
+
+    assert.equal(state.sessionId, "ses_current")
+})
+
+test("the delete branch does not swallow the compression timing branch", async () => {
+    // message.part.updated must still be routed to the timing handler.
+    const state = createSessionState()
+    state.sessionId = "ses_timing"
+    const handler = createEventHandler(state, logger)
+
+    await handler({
+        event: {
+            type: "message.part.updated",
+            time: 1_000,
+            properties: {
+                part: {
+                    type: "tool",
+                    tool: "compress",
+                    callID: "call_x",
+                    messageID: "msg_x",
+                    state: { status: "pending" },
+                },
+            },
+        },
+    })
+
+    assert.equal(state.compressionTiming.startsByCallId.size, 1)
+})
+
+test("unrelated events leave the storage directory alone", async () => {
+    const state = createSessionState()
+    const handler = createEventHandler(state, logger)
+    const before = readdirSync(STORAGE_DIR).sort()
+
+    await handler({ event: { type: "session.updated", properties: { info: { id: "ses_x" } } } })
+    await handler({ event: { type: "storage.write" } })
+
+    assert.deepEqual(readdirSync(STORAGE_DIR).sort(), before)
+})