fix(quickjs): resolve BigInt serialization crashes in REPL results an… by noishey · Pull Request #559 · langchain-ai/deepagentsjs

Arjun Shenoy (noishey) · 2026-05-30T14:36:33Z

…d logs

Description

Resolves Issue #558: BigInt values crash QuickJS interpreter result serialization.

This PR adds safe BigInt serialization and formatting within the @langchain/quickjs code interpreter. Prior to this fix, the interpreter would throw a TypeError: Do not know how to serialize a BigInt inside standard host-side stringification paths (formatReplResult, setupConsole, extractToolText), and return "[object Object]" for nested objects containing bigints due to Emscripten bridge JSON limitations.

Key Changes

Safe JSON Stringifier: Introduced stringifyJson in utils.ts to cleanly stringify nested objects containing bigint primitives by mapping them to strings instead of crashing.
Primitive BigInt Support: Updated formatReplResult to print primitive BigInt cell evaluations without surrounding quotes (matching standard number styling).
Resilient safeDump VM Bridge:
- Implemented a custom safeDump(handle) on ReplSession in session.ts.
- When standard context.dump() encounters serialization limits for objects containing BigInt and falls back to returning "[object Object]", safeDump automatically invokes a custom guest-side stringifier to prefix bigints with a sentinel ("__BIGINT__:").
- The host cleanly parses and revives these sentinel string patterns back into native host-side bigint values.
- Avoids relying on context.isEqual, preserving support for the asyncify WASM variant.
Direct Safe Stringification in Host-Paths: Replaced standard JSON.stringify inside host console listeners and tool result extractions with stringifyJson.

Verification & Tests

Automated Tests Added

Unit Tests (utils.test.ts):
- Validated that primitive bigint cell results are formatted cleanly without quotes.
- Validated that nested arrays/objects containing bigint types serialize to formatted JSON.
Integration Tests (session.test.ts):
- Validated that evaluating 9007199254740993n + 7n yields a native host bigint (9007199254741000n).
- Validated that evaluating objects/arrays containing bigints correctly returns the fully revived host object with native bigint properties.
- Validated that console logging deep objects containing bigint properties behaves correctly.

Results

All 206 unit/integration tests and type-checks successfully passed.

pnpm --filter @langchain/quickjs typecheck  # Success (0 errors)
pnpm --filter @langchain/quickjs test       # Success (206/206 passed)
pnpm test                                   # Success (1500+ monorepo tests passed)

…d logs

changeset-bot · 2026-05-30T14:36:39Z

🦋 Changeset detected

Latest commit: f90e3ef

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@langchain/quickjs	Patch

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commit: f90e3ef

Arjun Shenoy (noishey) · 2026-05-30T14:48:53Z

Please Review The PR.

…rwrite error by adding paths mapping

Hunter Lovell (hntrl) · 2026-06-02T22:54:10Z

+  private safeDump(handle: QuickJSHandle): unknown {
+    const context = this.context!;
+    const value = context.dump(handle);
+    if (value === "[object Object]") {
+      try {
+        const stringifyFn = context.evalCode(`
+          (val) => JSON.stringify(val, (k, v) => typeof v === "bigint" ? "__BIGINT__:" + v.toString() : v)
+        `);
+        if (stringifyFn.error) {
+          stringifyFn.error.dispose();
+          return value;
+        }
+        const stringified = context.callFunction(
+          stringifyFn.value,
+          context.undefined,
+          handle,
+        );
+        stringifyFn.value.dispose();
+
+        if (stringified.error) {
+          stringified.error.dispose();
+          return value;
+        }
+
+        const typeofStringified = context.typeof(stringified.value);
+        if (typeofStringified === "undefined") {
+          stringified.value.dispose();
+          return value;
+        }
+
+        const jsonStr = context.getString(stringified.value);
+        stringified.value.dispose();
+
+        return JSON.parse(jsonStr, (_k, v) => {
+          if (typeof v === "string" && v.startsWith("__BIGINT__:")) {
+            return BigInt(v.slice(11));
+          }
+          return v;
+        });
+      } catch {
+        return value;
+      }
+    }
+    return value;
+  }


what is this for? Context values don't get serialized at .dump so we shouldn't need to indirect to bigint handling here?

Co-authored-by: Hunter Lovell <40191806+hntrl@users.noreply.github.com>

Signed-off-by: Arjun Shenoy <arjunshenoy23@gmail.com>

Arjun Shenoy (noishey) · 2026-06-16T12:16:42Z

Hunter Lovell (@hntrl) please check the merging of this PR #559

fix(quickjs): resolve BigInt serialization crashes in REPL results an…

0f47e22

…d logs

Arjun Shenoy (noishey) added 2 commits May 30, 2026 20:08

chore(changeset): add patch changeset for @langchain/quickjs

f8a25f3

chore: trigger security checks

8f16977

langsmith-fleet Bot added the triage: high-impact label May 31, 2026

fix(deepagents): resolve tsconfig duplicate definition index.d.ts ove…

3408e1a

…rwrite error by adding paths mapping

langsmith-fleet Bot added bug Something isn't working needs review labels Jun 1, 2026

Hunter Lovell (hntrl) reviewed Jun 2, 2026

View reviewed changes

Hunter Lovell (hntrl) added the needs-response label Jun 2, 2026

github-actions Bot removed the needs-response label Jun 3, 2026

Arjun Shenoy (noishey) and others added 6 commits June 3, 2026 18:43

Merge branch 'main' into fix/bigint-quickjs-serialization

cc38d32

fix(quickjs): fast-path BigInt in safeDump to avoid guest JSON fallback

fd36a37

Update libs/deepagents/tsconfig.json

a87b13b

Co-authored-by: Hunter Lovell <40191806+hntrl@users.noreply.github.com>

Merge branch 'main' into fix/bigint-quickjs-serialization

bd325ce

Merge branch 'main' into fix/bigint-quickjs-serialization

4473465

Signed-off-by: Arjun Shenoy <arjunshenoy23@gmail.com>

chore(quickjs): remove unused SkillsContext import

f90e3ef

Arjun Shenoy (noishey) force-pushed the fix/bigint-quickjs-serialization branch from 2355cfc to f90e3ef Compare June 16, 2026 12:09

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Arjun Shenoy (noishey) commented May 30, 2026

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