diff --git a/src/mcp.ts b/src/mcp.ts
index 6ee9f91..8f91941 100644
--- a/src/mcp.ts
+++ b/src/mcp.ts
@@ -60,6 +60,14 @@ export function resolveProxyOrigin(): string {
 const TOOL_TIMEOUT_MS = 60_000;
 const CONVERSATION_FROM_ENV = process.env.CLAUDE_CODE_SESSION_ID?.trim() || process.env.BILI_CONVERSATION_ID?.trim() || undefined;
 const IDENTITY_BINDING = Boolean(process.env.CLAUDE_CODE_SESSION_ID?.trim());
+// #656: hosts that resume a session (claude --resume forks a NEW session id)
+// do so after MCP children were spawned — the env-captured id goes stale and
+// every tool call 404s forever. When that exact failure is seen, adopt the
+// proxy's most-recent active conversation (status?fallback=latest) and retry
+// once. Only armed for identity-bound hosts (claude code); opt out with
+// BILI_MCP_NO_ORPHAN_ADOPT=1 when several host sessions share one proxy and
+// the resumed one must not adopt a sibling's conversation.
+const ORPHAN_ADOPT = IDENTITY_BINDING && process.env.BILI_MCP_NO_ORPHAN_ADOPT !== "1";
 let manifestTools: McpToolDef[] = [];
 let conversationId = CONVERSATION_FROM_ENV;
 let registered = false;
@@ -98,21 +106,55 @@ function ensureManifest(): Promise<void> {
 }
 
 export async function forwardTool(tool: string, args: unknown, timeoutMs: number = TOOL_TIMEOUT_MS): Promise<string> {
-    let res: Response;
+    for (let attempt = 0; ; attempt++) {
+        let res: Response;
+        try {
+            res = await fetch(`${resolveProxyOrigin()}/__bili/plugin/tool`, {
+                method: "POST",
+                headers: { "content-type": "application/json" },
+                body: JSON.stringify({ conversationId, tool, args }),
+                signal: AbortSignal.timeout(timeoutMs),
+            });
+        } catch (err) {
+            if (err instanceof Error && err.name === "TimeoutError") throw new Error(`tool forward timed out after ${timeoutMs}ms: ${tool}`);
+            throw err;
+        }
+        const data = (await res.json()) as { ok?: boolean; result?: string; error?: string };
+        if (res.ok && data.ok) return data.result ?? "";
+        // #656: the shim's captured id was never registered — the host likely
+        // resumed its session and forked a new id after this shim spawned.
+        // Adopt the proxy's latest active conversation and retry once.
+        if (
+            res.status === 404 && attempt === 0 && ORPHAN_ADOPT && conversationId &&
+            typeof data.error === "string" && data.error.includes("no model request has arrived")
+        ) {
+            if (await adoptLatestActiveConversation()) continue;
+        }
+        throw new Error(data.error ?? `tool forward failed: ${res.status}`);
+    }
+}
+
+/** One-shot recovery for a stale shim id (#656): resolve the proxy's
+ *  most-recent ACTIVE conversation via the status endpoint's fallback=latest
+ *  and adopt it for all subsequent tool calls. Returns true when an adoption
+ *  happened (caller should retry the tool call). */
+async function adoptLatestActiveConversation(): Promise<boolean> {
     try {
-        res = await fetch(`${resolveProxyOrigin()}/__bili/plugin/tool`, {
-            method: "POST",
-            headers: { "content-type": "application/json" },
-            body: JSON.stringify({ conversationId, tool, args }),
-            signal: AbortSignal.timeout(timeoutMs),
-        });
-    } catch (err) {
-        if (err instanceof Error && err.name === "TimeoutError") throw new Error(`tool forward timed out after ${timeoutMs}ms: ${tool}`);
-        throw err;
+        const res = await fetch(
+            `${resolveProxyOrigin()}/__bili/plugin/status?conversationId=${encodeURIComponent(conversationId ?? "")}&fallback=latest`,
+            { signal: AbortSignal.timeout(5000) },
+        );
+        if (!res.ok) return false;
+        const data = (await res.json()) as { ok?: boolean; conversationId?: string; fallback?: boolean };
+        if (data.ok !== true || data.fallback !== true || !data.conversationId || data.conversationId === conversationId) return false;
+        process.stderr.write(
+            `[bili-mcp] conversation id no longer known by the proxy (host resumed its session?); adopting latest active conversation ${data.conversationId}\n`,
+        );
+        conversationId = data.conversationId;
+        return true;
+    } catch {
+        return false;
     }
-    const data = (await res.json()) as { ok?: boolean; result?: string; error?: string };
-    if (!res.ok || !data.ok) throw new Error(data.error ?? `tool forward failed: ${res.status}`);
-    return data.result ?? "";
 }
 
 const ERR_TOOL = -32602;
diff --git a/src/plugin.ts b/src/plugin.ts
index d83ede5..8a62ba6 100644
--- a/src/plugin.ts
+++ b/src/plugin.ts
@@ -359,12 +359,31 @@ export type PluginToolDeps = {
     log: (level: string, msg: string) => void;
 };
 
+/** Reverse-lookup the conversation id bound to a session id. #656: the
+ *  status endpoint's fallback branch picks the latest active SESSION, but a
+ *  caller that needs to ADOPT it (an MCP shim whose captured conversation id
+ *  went stale after the host resumed) must be told the session's conversation
+ *  id, not have its own stale id echoed back. Most-recently-seen binding wins
+ *  when several conversations share one session. */
+function conversationIdForSession(sessionId: string): string | undefined {
+    let bestId: string | undefined;
+    let bestSeen = -Infinity;
+    for (const [cid, entry] of conversations) {
+        if (entry.sessionId === sessionId && entry.lastSeen > bestSeen) {
+            bestId = cid;
+            bestSeen = entry.lastSeen;
+        }
+    }
+    return bestId;
+}
+
 /** Context-level visibility for plugin UIs (status bars / slash commands):
  *  the same usage the nudge decision sees, keyed by conversation id. */
 export function handlePluginStatus(conversationId: string, res: import("node:http").ServerResponse, deps: PluginToolDeps, fallbackLatest = false): void {
     let entry = conversations.get(conversationId);
     let session = entry ? peekSession(entry.sessionId) : undefined;
     let viaFallback = false;
+    let resolvedConversationId = conversationId;
     if ((!entry || !session) && fallbackLatest) {
         // #404: only sessions with real activity in THIS process qualify.
         // Before the fix every boot-restored session carried lastSeen =
@@ -376,6 +395,9 @@ export function handlePluginStatus(conversationId: string, res: import("node:htt
         if (latest) {
             session = latest;
             viaFallback = true;
+            // #656: name the conversation that was actually resolved — the
+            // caller asked with a stale id and must learn the real one.
+            resolvedConversationId = conversationIdForSession(latest.id) ?? conversationId;
         } else {
             res.writeHead(404, { "content-type": "application/json" });
             res.end(JSON.stringify({ ok: false, error: "no session with activity since boot — issue a model request or pass the conversation id" }));
@@ -441,7 +463,7 @@ export function handlePluginStatus(conversationId: string, res: import("node:htt
     res.writeHead(200, { "content-type": "application/json" });
     res.end(JSON.stringify({
         ok: true,
-        conversationId,
+        conversationId: resolvedConversationId,
         fallback: viaFallback || undefined,
         label: session.meta.label ?? null,
         pluginAgent: session.metadata.pluginAgent ?? null,
@@ -481,8 +503,18 @@ export async function handlePluginTool(
     const entry = conversations.get(conversationId);
     const session = entry ? peekSession(entry.sessionId) : undefined;
     if (!entry || !session) {
+        // #656: two distinct failures shared one message before. An id that was
+        // NEVER registered is the classic stale-shim-id case (host resumed its
+        // session after the MCP shim captured CLAUDE_CODE_SESSION_ID) — say so,
+        // and log it: these 404s used to be invisible in bili.log.
+        deps.log("warn", `[plugin] tool "${tool}" rejected for conversation ${conversationId}: ${entry ? "id registered but session not resident in this proxy instance" : "id never registered (stale shim session id after host resume?)"}`);
         res.writeHead(404, { "content-type": "application/json" });
-        res.end(JSON.stringify({ ok: false, error: "unknown plugin conversation (no model request has arrived with this conversation id yet)" }));
+        res.end(JSON.stringify({
+            ok: false,
+            error: !entry
+                ? "unknown plugin conversation (no model request has arrived with this conversation id yet)"
+                : "unknown plugin conversation (id registered but its session is not resident in this proxy instance — a fresh model request re-binds it)",
+        }));
         return;
     }
     // Absorb enablement is per-session (last resolved config), so the gate
diff --git a/tests/plugin-protocol.test.ts b/tests/plugin-protocol.test.ts
index e304a4b..ac352cb 100644
--- a/tests/plugin-protocol.test.ts
+++ b/tests/plugin-protocol.test.ts
@@ -186,6 +186,25 @@ async function callPluginAnthropic(
     return { raw, events: parseAnthropicSse(raw), json: undefined };
 }
 
+async function claudeIdentityRequest(h: Harness, sessionId: string, messages: AnthropicMessage[]): Promise<number> {
+    const resp = await fetch(`http://127.0.0.1:${h.proxyPort}/bili/http://127.0.0.1:${h.upstreamPort}/v1/messages`, {
+        method: "POST",
+        headers: {
+            "content-type": "application/json",
+            "x-claude-code-session-id": sessionId,
+        },
+        body: JSON.stringify({
+            model: "claude-test",
+            max_tokens: 1024,
+            stream: true,
+            system: UPSTREAM_SYSTEM,
+            messages,
+        }),
+    });
+    if (resp.body) for await (const _ of resp.body) {}
+    return resp.status;
+}
+
 test("plugin manifest serves the exact wire tool schemas, headers and version", async () => {
     const h = await startHarness([textScript()]);
     try {
@@ -405,6 +424,85 @@ test("plugin tool API error paths: bad JSON, unknown tool, unknown conversation"
         const errJson = (await unknownConv.json()) as { ok: boolean; error: string };
         assert.equal(errJson.ok, false);
         assert.match(errJson.error, /unknown plugin conversation/i);
+        // #656: a never-registered id must say so explicitly (stale shim id
+        // after host resume) — not the generic wording.
+        assert.match(errJson.error, /no model request has arrived/);
+    } finally {
+        await h.close();
+    }
+});
+
+test("#656: status fallback=latest resolves the active conversation for a stale shim id, and the adopted id then works for tool calls", async () => {
+    const h = await startHarness([textScript()]);
+    try {
+        const conv = "plug-conv-after-resume";
+        // The host resumed and now sends traffic under a NEW id; the shim
+        // still holds the pre-resume one ("stale-shim-id").
+        await callPluginAnthropic(h, conv, [{ role: "user", content: "hello after resume" }]);
+
+        // Shim adoption step 1: status asked with the stale id falls back to
+        // the latest active conversation and reports the adoption.
+        const statusResp = await fetch(`http://127.0.0.1:${h.proxyPort}/__bili/plugin/status?conversationId=stale-shim-id&fallback=latest`);
+        assert.equal(statusResp.status, 200);
+        const status = (await statusResp.json()) as { ok: boolean; conversationId: string; fallback?: boolean };
+        assert.equal(status.ok, true);
+        assert.equal(status.fallback, true);
+        assert.equal(status.conversationId, conv);
+
+        // Shim adoption step 2: the retry with the adopted id succeeds.
+        const adopted = await fetch(`http://127.0.0.1:${h.proxyPort}/__bili/plugin/tool`, {
+            method: "POST",
+            headers: { "content-type": "application/json" },
+            body: JSON.stringify({ conversationId: conv, tool: "acp_status", args: {} }),
+        });
+        assert.equal(adopted.status, 200);
+        const adoptedJson = (await adopted.json()) as { ok: boolean };
+        assert.equal(adoptedJson.ok, true);
+    } finally {
+        await h.close();
+    }
+});
+
+test("#656 identity binding: a stale x-claude-code-session-id recovers via status fallback=latest", async () => {
+    const h = await startHarness([textScript()]);
+    try {
+        const OLD = "claude-session-before-resume";
+        const NEW = "claude-session-after-resume";
+        // Identity binding (#162): the shell registers its captured id; after
+        // a resume the host forks NEW and the shell re-registers it, leaving
+        // the stale OLD id with no model traffic.
+        queuePluginRegister(OLD, "mcp", true);
+        queuePluginRegister(NEW, "mcp", true);
+        assert.equal(await claudeIdentityRequest(h, NEW, [{ role: "user", content: "after resume" }]), 200);
+
+        const toolOld = await fetch(`http://127.0.0.1:${h.proxyPort}/__bili/plugin/tool`, {
+            method: "POST",
+            headers: { "content-type": "application/json" },
+            body: JSON.stringify({ conversationId: OLD, tool: "acp_status", args: {} }),
+        });
+        assert.equal(toolOld.status, 404);
+        const toolOldJson = (await toolOld.json()) as { ok: boolean; error: string };
+        assert.equal(toolOldJson.ok, false);
+        assert.match(toolOldJson.error, /no model request has arrived/);
+
+        // Adoption step 1: status with the stale id falls back to the latest
+        // active conversation and reports NEW (the resolved id), not the stale one.
+        const statusResp = await fetch(`http://127.0.0.1:${h.proxyPort}/__bili/plugin/status?conversationId=${OLD}&fallback=latest`);
+        assert.equal(statusResp.status, 200);
+        const status = (await statusResp.json()) as { ok: boolean; conversationId: string; fallback?: boolean };
+        assert.equal(status.ok, true);
+        assert.equal(status.fallback, true);
+        assert.equal(status.conversationId, NEW);
+
+        // Adoption step 2: the retry with the adopted id succeeds.
+        const toolNew = await fetch(`http://127.0.0.1:${h.proxyPort}/__bili/plugin/tool`, {
+            method: "POST",
+            headers: { "content-type": "application/json" },
+            body: JSON.stringify({ conversationId: NEW, tool: "acp_status", args: {} }),
+        });
+        assert.equal(toolNew.status, 200);
+        const toolNewJson = (await toolNew.json()) as { ok: boolean };
+        assert.equal(toolNewJson.ok, true);
     } finally {
         await h.close();
     }