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Merge pull request #46 from Curabis/fix/bc-mcp-bridge-proactive-session-refresh

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[bc-mcp-bridge] Reactive + proactive session self-heal
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Michael Dieringer 2026-08-07 08:36:34 +02:00 • committed by GitHub
commit 73e5a01a36
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1 changed files with 50 additions and 5 deletions
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55
custom/setup/bc-mcp-bridge.js
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@ -50,7 +50,18 @@ function loadConfig() {
}
const cfg = loadConfig();
let token = null, tokenExp = 0, sessionId = null;
let token = null, tokenExp = 0, sessionId = null, lastInitializeMsg = null, lastActivityAt = 0;
// 2026-08-07: the reactive re-initialize below only fires after BC has already
// rejected a request. It self-heals invisibly to the caller, but still burns
// two round trips (reject, initialize, retry) on the first call after any idle
// gap. A client that opens a fresh session per call (e.g. a Power Automate
// flow) never hits this at all, which is why it reads as more stable than a
// long-lived interactive session that caches sessionId for its whole
// lifetime. Proactively refreshing before a call that has been idle a while
// gets the same effective robustness without waiting for BC to reject first.
// No API exposes the session's actual TTL, so this threshold is a heuristic,
// not a documented guarantee.
const SESSION_IDLE_THRESHOLD_MS = 3 * 60 * 1000; // 3 min
async function getToken() {
if (token && Date.now() < tokenExp - 60000) return token; // forny 1 min foer udloeb
@ -118,8 +129,23 @@ async function forwardOnce(msg) {
}
async function forward(msg) {
if (msg.method === "initialize") lastInitializeMsg = msg;
if (sessionId && msg.method !== "initialize" && lastActivityAt &&
Date.now() - lastActivityAt > SESSION_IDLE_THRESHOLD_MS) {
process.stderr.write(`[bc-mcp-bridge] session idle ${Math.round((Date.now() - lastActivityAt) / 1000)}s, refreshing proactively\n`);
sessionId = null;
if (lastInitializeMsg) {
try {
return await forwardOnce(msg);
await forwardOnce(lastInitializeMsg);
} catch (initErr) {
process.stderr.write(`[bc-mcp-bridge] proactive re-initialize failed: ${initErr.message || initErr}\n`);
}
}
}
try {
const result = await forwardOnce(msg);
lastActivityAt = Date.now();
return result;
} catch (e) {
// 2026-08-04: one retry with a forced-fresh BC session (sessionId cleared).
// A long-idle Claude Code session can leave the cached Mcp-Session-Id or
@ -127,11 +153,30 @@ async function forward(msg) {
// until REQUEST_TIMEOUT_MS, or as an "Internal_CompanyNotFound" that was
// actually a dead session, not a real company problem. Quick, frequent
// calls never idle long enough to hit this; a long session with gaps
// between calls does. One retry self-heals without the developer noticing;
// if the retry also fails, this is a real error and should surface as one.
// between calls does.
process.stderr.write(`[bc-mcp-bridge] retrying after: ${e.message || e}\n`);
sessionId = null;
return await forwardOnce(msg);
// 2026-08-05: clearing sessionId is not enough on its own. BC's own error
// is explicit -- "A new session can only be created by an initialize
// request" -- so simply resending the original non-initialize message
// with no session header reproduces the exact same error, not a fresh
// session. Replay the client's actual initialize message first (cached
// above, the only thing BC will accept to hand out a new session), THEN
// retry the original call with the session that establishes. If there's
// no cached initialize yet (this failure IS the very first call, or is
// itself the initialize), skip straight to the plain retry below.
if (msg.method !== "initialize" && lastInitializeMsg) {
try {
await forwardOnce(lastInitializeMsg);
} catch (initErr) {
process.stderr.write(`[bc-mcp-bridge] re-initialize failed: ${initErr.message || initErr}\n`);
// Fall through anyway -- retrying the original message will still
// surface a clear, real error if the session truly can't be restored.
}
}
const result = await forwardOnce(msg);
lastActivityAt = Date.now();
return result;
}
}