fix(mcp): count resolved isError tool results as breaker failures and error completions

[murdore]

Base: release. Single commit, rebased onto current release HEAD
(75db63d41c58cf2f121cb51590e0e20f3c13c2ca) at 5fc3021921c83b17ea3b7ec2b9e425fddeb3291c.
Part of the curator→NeuroLink MCP ownership series. Merges cleanly onto
current release HEAD.

Note: open PR #1683 also touches src/lib/mcp/externalServerManager.ts and
is being kept independent of this PR; whichever of the two merges second
will need a rebase against the other.

Why / what

Root cause: the MCP client does not throw on a protocol error — it resolves
{ isError: true, content: [...] }. Inside MCPCircuitBreaker.execute(),
toolDiscoveryService.executeTool() only set the tracing span status on a
resolved isError result and returned; Promise.race saw a clean resolve, so
recordCall(true, ...) ran unconditionally afterwards. A tool that only ever
"fails" by resolving an error therefore could never trip its own breaker, and
updateToolStats(toolKey, true, ...) counted every one of those calls as a
completion-telemetry success.

Reproduced before the fix: a stdio fixture server (added at
test/fixtures/mcp-breaker-resolved-errors-server.mjs) whose only tool always
resolves { isError: true } was called 10 times through the shipped
ExternalServerManager -> ToolDiscoveryService -> MCPCircuitBreaker path; the
breaker's getStats().state stayed "closed" and failedCalls stayed 0.

Fix: MCPCircuitBreaker.execute() now hands its operation callback a
recordResolvedFailure(reason?) function. Calling it flags the call's
outcome as a logical failure without throwing — the resolved value is still
returned to the caller unchanged; no transport error is synthesized. The
inline failure bookkeeping that used to live only in the catch block
(recordCall(false, ...), the callFailure emit, and the half-open/closed
state-transition checks) is extracted into a shared private
recordFailureOutcome() so both the thrown-error path and the new
resolved-failure path run identical bookkeeping.
toolDiscoveryService.executeTool() calls recordResolvedFailure() in the
branch that already detects isError === true on the resolved MCP result,
and passes !isErrorResultDetected into updateToolStats() so completion
telemetry now labels a resolved isError call as a failed completion (the
wrapper above it still returns success:true / data:result unchanged —
flipping that would make ExternalServerManager.executeTool() throw instead
of returning the resolved MCP error, which this fix must not do).

Does: opens the breaker for a tool that only fails by resolving isError,
corrects completion telemetry for that case, keeps the resolved value
reaching the caller unchanged in both the open- and closed-breaker cases
(an open breaker still rejects with the existing CircuitBreakerOpenError,
proven by the fixture's own call-count log never advancing past 10).

Does not: change behavior for any operation that throws (unchanged
catch-path bookkeeping), change the generation/AI-SDK tool-calling path, or
change the shape of the resolved MCP result returned to callers.

Test: test/continuous-test-suite-mcp-breaker-resolved-errors.ts, driven
through the real ExternalServerManager -> ToolDiscoveryService ->
MCPCircuitBreaker path against a real stdio child-process MCP server (no
network, no AI provider — fully deterministic). Two cases: 10 consecutive
resolved-isError calls open the breaker (minimumCallsBeforeCalculation=10)
and the 11th is rejected by CircuitBreakerOpenError before ever reaching the
server process; a single resolved-isError call is counted as a breaker
failure but does not open the breaker on its own. Wired into
package.json's test:unit via test:mcp-breaker-resolved-errors.

Review follow-up (CodeRabbit, MINOR): ExternalServerManager labelled every
success:true wrapper as a successful mcp_tool_calls_total sample,
including resolved { isError: true } results. ExternalMCPToolResult gains
an additive, optional isErrorResult flag that ToolDiscoveryService sets
from the same detection the breaker uses; the manager records
recordMCPToolCall(..., success=false) for those calls. The wrapper's
success:true / data contract is unchanged. The suite is added to the
neurolink/e2e-tests-only allow list in eslint.config.js for one deep
../dist/telemetry/telemetryService.js import (TelemetryService is not a
root export); the reason is stated there and in the suite header.

Files

 eslint.config.js                                   |  10 +
 package.json                                       |   3 +-
 src/lib/mcp/externalServerManager.ts               |  11 +-
 src/lib/mcp/mcpCircuitBreaker.ts                   |  86 +++++--
 src/lib/mcp/toolDiscoveryService.ts                | 250 ++++++++++---------
 src/lib/types/externalMcp.ts                       |   8 +
 ...nuous-test-suite-mcp-breaker-resolved-errors.ts | 265 +++++++++++++++++++++
 .../mcp-breaker-resolved-errors-server.mjs         |  43 ++++
 8 files changed, 538 insertions(+), 138 deletions(-)
 (plus generated docs/api updates, regenerated for this head)

Testing evidence

Head sha: a58bef223b9d9a274bac64271e5db52b9b6194c3
Release sha (rebase base): 75db63d41c58cf2f121cb51590e0e20f3c13c2ca

Commands (run in the PR worktree, on the committed HEAD):

pnpm run build
pnpm exec tsx test/continuous-test-suite-mcp-breaker-resolved-errors.ts

Break-on-purpose: reverted the fix's actual behavioral hunk in
src/lib/mcp/toolDiscoveryService.ts (the isErrorResultDetected = true; /
recordResolvedFailure(...) call in the isError === true branch — the two
lines that tell the breaker about a resolved MCP error), rebuilt, reran, then
restored with git checkout HEAD -- src/ and rebuilt again.

Run	Command	Passed	Failed	Total	Exit
fixed (HEAD)	pnpm exec tsx test/continuous-test-suite-mcp-breaker-resolved-errors.ts	2	0	2	0
broken (fix hunk reverted)	same	0	2	2	1
restored (git checkout HEAD -- src/)	same	2	0	2	0

Fixed-run summary (real lines from the log):

  ✓ 10 consecutive resolved isError results still reach the caller unchanged, and open the breaker
  ✓ a single resolved isError call is counted as a failure but does not open the breaker on its own
  Passed:  2
  Total:   2
  RESULT: PASS

Broken-run summary (real lines from the log — targeted assertions fail as ✗, not skipped):

  ✗ 10 consecutive resolved isError results still reach the caller unchanged, and open the breaker
    → the breaker should be open after 10 resolved-isError calls (minimumCallsBeforeCalculation=10, failureThreshold=3)
  ✗ a single resolved isError call is counted as a failure but does not open the breaker on its own
    → a resolved isError result must be recorded as success=false, not counted as a successful tool call
  Passed:  0
  Failed:  2
  Total:   2
  RESULT: FAIL

Restored-run summary (matches fixed):

  ✓ 10 consecutive resolved isError results still reach the caller unchanged, and open the breaker
  ✓ a single resolved isError call is counted as a failure but does not open the breaker on its own
  Passed:  2
  Total:   2
  RESULT: PASS

Additional touched suite, fixed-HEAD only (exercises ToolDiscoveryService /
MCPCircuitBreaker broadly, not this PR's own suite, so no break/restore
cycle was run against it): pnpm exec tsx test/continuous-test-suite-mcp-infra.ts
-> Passed 97, Total 97, exit 0.

git status --porcelain is empty and HEAD is unchanged
(5fc3021921c83b17ea3b7ec2b9e425fddeb3291c) after the cycle.

Finalize gates on this commit (finalize-commit.sh, exit codes captured):
build, docs-api regen, check (tsc --noEmit), lint (format-check + eslint),
check:tools-tests, check:test-parse — all exit 0, plus the Husky pre-commit
hook (format:staged, codegen:catalog --check, check, validate:all) passed,
not bypassed.

Review follow-ups

• CodeRabbit (2026-09-02T06:51:27Z, COMMENTED) — actionable comment on
  test/continuous-test-suite-mcp-breaker-resolved-errors.ts:157: keep the
  resolved-result assertion message to structural diagnostics only, no
  JSON.stringify(result), so a real failure can't be misclassified as a
  provider-side skip by defineSuite. Already-fixed: the message at
  that line is exactly `call ${i}: expected a resolved isError result (isError !== true)` with a comment stating the reason — present
  verbatim in this same commit, no change needed this pass.
• Yama (Tara-ag) review (2026-09-09T09:49:46Z, APPROVED): no action
  items.
• Both review threads on this PR (2/2) are resolved; nothing outstanding to
  reply to.
• Rebase: rebased the single commit onto current release HEAD. The
  non-generated diff applied cleanly with git apply --3way; the only
  difference from the original diff is a context-line shift in
  package.json's test:unit/script list (release gained more test:*
  entries since this PR's original base) — same content, different
  neighboring context line. No hand conflict resolution was needed.
• PR fix(mcp): let the process exit and SIGTERM terminate it #1683 dependency noted above per this repo's parallel-PR tracking.

Pre-merge gate

An independent pre-merge review checked this PR's diff, its CI signal, and its review-thread state before merge. Two findings were confirmed by a checker and not refuted by an independent verifier; both were minor.

1. ExternalServerManager's totalErrors metric (and the public getExternalMCPStatistics() it feeds) was not updated for a resolved isError result, unlike the three sibling failure counters this PR already fixes — disposition: fixed. executeTool()'s result.success branch now increments instance.metrics.totalErrors whenever resolvedError is true, so getStatistics()/getExternalMCPStatistics().totalErrors agrees with the circuit breaker, TelemetryService, and ToolDiscoveryService's failedCalls on the same event instead of silently staying at 0. Covered by a new case in test/continuous-test-suite-mcp-breaker-resolved-errors.ts asserting getStatistics().totalErrors increments by exactly 1 after one resolved-isError call. Verified test-first: the new assertion failed (1 failed / 2 passed) before the one-line fix, and passed (3/3) after it.
2. The latest "Yama PR Review" CI check run on this PR's pinned commit is red, but not because of any unresolved review item — disposition: answered-no-code-change. Both review threads are resolved (2/2 isResolved:true) and a formal Tara-ag APPROVED review stands for this exact commit. The red run is juspay/neurolink#1754's known silent no-op (Yama's GitHub client reading the wrong repo slug), evidenced by that check run's own failure annotation quoting issue Yama PR Review reports success after reviewing nothing — its GitHub reads 404 against juspay/juspay #1754. "Yama PR Review" is not a required status check on release in either the ruleset or classic branch protection, so it cannot block this merge. No code in this PR is implicated.

Testing evidence (this pass)

Head sha: a58bef223b9d9a274bac64271e5db52b9b6194c3

pnpm run build
pnpm exec tsx test/continuous-test-suite-mcp-breaker-resolved-errors.ts

Break-on-purpose (F2 fix only, working tree only — never committed): replaced
the if (resolvedError) { instance.metrics.totalErrors++; } block in
src/lib/mcp/externalServerManager.ts with a single comment, rebuilt, reran,
then restored with git checkout HEAD -- src/lib/mcp/externalServerManager.ts
and rebuilt again.

Run	Passed	Failed	Total	Exit
fixed (new HEAD)	3	0	3	0
broken (totalErrors increment reverted in the working tree only)	2	1	3	1
restored (git checkout HEAD -- src/lib/mcp/externalServerManager.ts)	3	0	3	0

The broken run's one failing test is exactly the new F2 assertion — "a
resolved isError call is reflected in getStatistics()'s totalErrors, matching
the breaker/telemetry/ToolDiscoveryService failure count" — reported as a
genuine ✗ (not a skip), exit 1.

pnpm run build was re-run standalone for all three states (fixed/broken/
restored) and exits 0 every time — the defect is behavioral/observability-only,
not a compile error.

Also re-run against the new HEAD, unchanged: pnpm exec tsx test/continuous-test-suite-mcp-infra.ts -> Passed 97, Total 97, exit 0.

Two of the gate's user-level scripts drive this fix through the public SDK
surface (dist/index.js) against real stdio MCP fixture servers, independent
of the PR's own suite (full detail in usertest-rerun.md):

Script	Result	Exit
happy-path.mjs	PASS	0
edge-and-unaffected.mjs	PASS	0

happy-path.mjs additionally logs getExternalMCPStatistics() after the
run — "totalErrors":11 for 10 resolved-isError calls plus the 1
breaker-rejected 11th call — making the F2 fix observable end-to-end, not
just through the unit-level suite.

git status --porcelain is empty and HEAD is unchanged
(a58bef223b9d9a274bac64271e5db52b9b6194c3) after the full cycle.

Finalize gates on this commit (finalize-commit.sh, exit codes captured):
build, docs-api regen, check (tsc --noEmit --strict, svelte-check), lint
(prettier --check + eslint), check:tools-tests, check:test-parse — all exit
0, plus the Husky pre-commit hooks, not bypassed.

Summary by CodeRabbit

• Bug Fixes

  • MCP tool calls that return resolved errors are now correctly counted as failures by the circuit breaker and telemetry.
  • Resolved MCP error results remain available to callers without being converted into transport errors.
  • Repeated resolved failures now open the circuit and prevent subsequent calls from reaching the server.
  • Tool results now identify resolved MCP errors separately from successful calls.

• Tests

  • Added coverage for resolved MCP errors and circuit-breaker behavior.

• Documentation

  • Updated API documentation for resolved-error reporting and result metadata.

[github-actions]

✅ Single Commit Policy - COMPLIANT

Status: Policy requirements met • 1 commit • Valid format • Ready for merge

📊 View validation details

📝 Commit Details

• Hash: a58bef223b9d9a274bac64271e5db52b9b6194c3
• Message: fix(mcp): count resolved isError tool results as breaker failures and error completions
• Author: Sachin Sharma

✅ Validation Results

• Single commit requirement met
• No merge commits in branch
• Semantic commit message format verified
• Ready for squash merge to release branch

---

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📝 Walkthrough

Walkthrough

The MCP circuit breaker now records resolved { isError: true } results as failures while returning them unchanged. Tool statistics and telemetry reflect the failure. End-to-end tests verify breaker opening and call suppression.

Changes

MCP resolved error handling

Layer / File(s)	Summary
Breaker resolved failure recording src/lib/mcp/mcpCircuitBreaker.ts	execute accepts recordResolvedFailure. Resolved failures share bookkeeping with thrown failures and return the original value.
Tool discovery, result typing, and telemetry src/lib/types/externalMcp.ts, src/lib/mcp/toolDiscoveryService.ts, src/lib/mcp/externalServerManager.ts	Resolved MCP errors set isErrorResult, notify the breaker, update tool statistics as failed calls, and record failed telemetry while preserving success: true and the protocol result.
Resolved error end-to-end validation test/fixtures/mcp-breaker-resolved-errors-server.mjs, test/continuous-test-suite-mcp-breaker-resolved-errors.ts, package.json, eslint.config.js	The fixture, tests, scripts, and lint exception validate failure counting, breaker opening, unchanged results, telemetry status, and blocked calls.
API documentation refresh docs/api/classes/*, docs/api/type-aliases/*, docs/api/variables/*	The API documentation describes the new callback and isErrorResult field and updates generated source references.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant ExternalServerManager
  participant ToolDiscoveryService
  participant MCPCircuitBreaker
  participant MCPFixtureServer
  ExternalServerManager->>ToolDiscoveryService: executeTool(resolve_error)
  ToolDiscoveryService->>MCPCircuitBreaker: execute(operation)
  ToolDiscoveryService->>MCPFixtureServer: invoke resolve_error
  MCPFixtureServer-->>ToolDiscoveryService: resolve {isError: true}
  ToolDiscoveryService->>MCPCircuitBreaker: recordResolvedFailure(error text)
  MCPCircuitBreaker-->>ToolDiscoveryService: return unchanged result
  ToolDiscoveryService-->>ExternalServerManager: record failed telemetry and return result

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Suggested reviewers: pdogra1299

Merge Risk: ⚪ Minimal · up to c0429

The change preserves resolved MCP results while correctly counting failures and updating telemetry; the validated test and cleanup paths introduce no remaining merge-blocking risk.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 7 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: resolved MCP isError tool results are counted as circuit-breaker failures and failed completions.

Full details: Docstring Coverage

Explanation

Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 7 files. (1 skipped: 1 unsupported.)

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Actionable comments posted: 1

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Inline comments:
In `@src/lib/mcp/toolDiscoveryService.ts`:
- Around line 738-744: Update executeTool’s telemetry handling to pass the
resolved MCP error state, such as isErrorResultDetected, to updateToolStats so {
isError: true } results count as failed calls. Preserve the existing successful
return wrapper and MCP payload, without changing the external execution flow to
throw.

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📒 Files selected for processing (5)

• package.json
• src/lib/mcp/mcpCircuitBreaker.ts
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• test/continuous-test-suite-mcp-breaker-resolved-errors.ts
• test/fixtures/mcp-breaker-resolved-errors-server.mjs

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🚀 Documentation validation passed!

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[Tara-ag]

Approved. The change correctly records resolved { isError: true } MCP results as breaker failures while preserving the returned protocol payload (a resolved result is a resolve, not a rejection, so not throwing keeps transport/parse semantics intact).

The only inline finding (CodeRabbit, toolDiscoveryService.ts:744 — pass isErrorResultDetected to updateToolStats) is now implemented exactly as requested via this.updateToolStats(toolKey, !isErrorResultDetected, duration);; the thread is resolved.

Checked and clean:

• Backward compatibility (Rule 5): MCPCircuitBreaker.execute gained an optional recordResolvedFailure callback; the only other callers (mcpClientFactory.ts, tool discovery) pass zero-arg callbacks that remain assignable — no unmodified caller breaks.
• Rule 1: no static provider imports introduced.
• No secrets, no CLI/SDK leak (Rule 4).
• Test (test/continuous-test-suite-mcp-breaker-resolved-errors.ts) drives dist/ at runtime with src/ imports limited to type — end-to-end only (Rule 15), single module graph.

[Tara-ag]

Superseded — this was an early summary. The canonical verdict for this PR lives in the single up-to-date summary comment (<!-- yama:summary -->); this one is kept for history only and is no longer a summary.

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Inline comments:
In `@test/continuous-test-suite-mcp-breaker-resolved-errors.ts`:
- Line 157: Update the assertion message in the resolved-result check to omit
JSON.stringify(result) and include only structural diagnostics such as the call
number, preventing recovered provider error text from affecting defineSuite
classification.

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• docs/api/classes/CircuitBreakerManager.md
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• docs/api/type-aliases/ExternalMCPServerEvents.md
• docs/api/type-aliases/ExternalMCPToolResult.md
• docs/api/type-aliases/RuntimeMCPServerInfo.md
• docs/api/variables/globalCircuitBreakerManager.md
• eslint.config.js
• src/lib/mcp/externalServerManager.ts
• src/lib/mcp/toolDiscoveryService.ts
• src/lib/types/externalMcp.ts
• test/continuous-test-suite-mcp-breaker-resolved-errors.ts

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Superseded — early recurring-review note. Its content (both review findings accepted) is fully covered by the single canonical summary comment (the current <!-- yama:summary --> on this PR). Kept for history only.

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Note

GitHub couldn't provide a complete incremental comparison for this pull request, so CodeRabbit is performing a full review instead. This review may take a little longer.

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Superseded — an earlier full-review summary. Superseded by the single canonical summary comment (the current <!-- yama:summary --> on this PR). Kept for history only.

[Tara-ag]

Superseded — an earlier full-review summary. Superseded by the single canonical summary comment (the current <!-- yama:summary --> on this PR). Kept for history only.

[Tara-ag]

Approving on the current head (186f946).

The resolved { isError: true } MCP results are correctly recorded as circuit-breaker failures and failed-completion telemetry while the original resolved payload is returned unchanged (treated as a resolve, not a rejection — correct since these arrive on the success path).

This is the consolidated current verdict of the recurring review; the canonical summary is the <!-- yama:summary --> comment on this PR. State set to approve to keep the PR review state in sync with the verdict.

[Tara-ag]

Superseded — an earlier copy of the summary verdict. The single canonical <!-- yama:summary --> for this PR is the current one (the later summary comment, which also folds in murdore's rebase triage). Kept for history only; this is no longer a standalone summary.

[murdore]

Rebase + re-triage: rebased this PR's single commit onto current release HEAD (release picked up additional commits since this PR's original base; git apply --3way applied cleanly, only a package.json context-line shift, no content conflicts). Re-checked both resolved review threads and the latest CodeRabbit review (COMMENTED) against current code: the one actionable comment (test/continuous-test-suite-mcp-breaker-resolved-errors.ts:157 — keep the resolved-result assertion message to structural diagnostics only, no JSON.stringify(result)) is already implemented verbatim in the merged commit, so no further change was needed. Yama's latest review is APPROVED with no action items. Noting for the record: open PR #1683 also touches src/lib/mcp/externalServerManager.ts and is being kept independent of this one; whichever merges second will need a rebase against the other.

[Tara-ag]

Verdict: APPROVE

Recurring review of fix/mcp-resolved-error-breaker on HEAD 5fc3021 (rebase of the previously-reviewed content onto current release). The resolved { isError: true } MCP results are counted as circuit-breaker failures and failed-completion telemetry while the original resolved payload is still returned to the caller unchanged — treating such a result as a resolve (not a rejection) is correct because it arrives on the protocol's success path. The rebase introduced no content changes (per murdore's triage: clean git apply --3way, only a package.json context-line shift); the single-commit policy bot confirms one valid commit.

Accepted resolved findings (not re-raised)

Finding	State
toolDiscoveryService.ts — pass isErrorResultDetected to updateToolStats. Verified in current code: this.updateToolStats(toolKey, !isErrorResultDetected, duration); thread resolved. ✅
test/continuous-test-suite-mcp-breaker-resolved-errors.ts — assertion-message interpolation. Verified structural-only (isError !== true, no payload interpolated); thread resolved. ✅

New findings

None. This matches the four prior approvals; my independent re-check of the current HEAD adds nothing new.

What was checked and found clean

• Backward compatibility (Rule 5): MCPCircuitBreaker.execute's new (recordResolvedFailure) => Promise<T> signature accepts the existing zero-arg () => Promise<T> callbacks at the only other call sites (mcpClientFactory.createClientOperation, discoverTools); only executeTool passes the callback. ExternalMCPToolResult.isErrorResult? is optional-additive and consumed only by the telemetry label. No unmodified caller breaks.
• No double-count: recordFailureOutcome is behaviourally identical to the old inline catch bookkeeping and runs exactly once per path (resolved path returns after it; a caller that flags a resolved failure and also throws still lands only in the catch). Half-open re-open is correctly handled.
• Telemetry coherence: breaker failedCalls, updateToolStats(…, false), and recordMCPToolCall(success=false) all agree for a resolved error.
• Test math: tool-execution breaker (failureThreshold: 3, default minimumCallsBeforeCalculation: 10) → 10 resolved failures open the circuit; the fixture call-log proves the 11th call is short-circuited before reaching the server.
• Concurrency: isErrorResultDetected and resolvedFailureReason are per-invocation locals — concurrent execute calls on the same breaker can't cross-contaminate outcomes.
• Rule 15 / e2e: the new suite drives dist/; the one deep dist/telemetry/telemetryService.js import is documented in the file header and covered by the eslint.config.js allow-list.
• Security / Rule 1 / Rule 4: no static provider imports; no secrets added; MCP params/output continue through redactForPreview before span attributes; no CLI concern leaks into the SDK path.

Non-blocking notes

1. Merge state is "blocked" — not a code defect. Likely tooling/branch-protection or the overlap with open PR fix(mcp): let the process exit and SIGTERM terminate it #1683 (also touching src/lib/mcp/externalServerManager.ts); as murdore noted, whichever merges second needs a rebase. Worth checking the branch-protection requirements before merging.
2. CodeRabbit pre-merge check flagged a Docstring Coverage warning (33.33% vs 80%) on functions touched by the diff. Soft/administrative; not blocking, but adding docstrings for the new callback signature and isErrorResult consumer would clear it.
3. Awareness (carried from prior reviews): every resolved isError now counts toward the tool-execution-* breaker regardless of severity, so a server legitimately answering { isError: true } for benign "not found"-style cases will trip after minimumCallsBeforeCalculation and be blocked for the reset window. That is the stated intent, but isError is not severity-classified; worth a follow-up if real servers resolve errors on their happy path.

No new blocking findings — clean approve. Review state set to approve to stay in sync with the verdict.

[Tara-ag]

Approve

Recurring review of fix/mcp-resolved-error-breaker on rebased HEAD 5fc3021. The resolved { isError: true } MCP results are now counted as circuit-breaker failures and failed-completion telemetry while the original resolved payload is returned unchanged. The rebase introduced no content changes, both previously-resolved finding threads remain fixed in the current code, and the latest CodeRabbit review is clean.

No new or outstanding findings — matches the prior approvals. (See the summary comment for the full assessment and two non-blocking notes: the "blocked" merge state likely tied to overlapping PR #1683 / branch protection, and CodeRabbit's soft docstring-coverage warning.)

Good to merge from my side.

[murdore]

Closing and reopening to re-run the pull_request workflows against the new release (#1763 landed the reproducible search-index generator), without a force-push.

[Tara-ag]

Superseded — this was a recurring-review status note, not the canonical summary. The single canonical <!-- yama:summary --> for this PR is the comprehensive assessment comment from 2026-09-24 (5824210994), which this note deferred to. Kept for history only; the de-duplicated marker lives on the canonical summary.

Verdict: APPROVE (recurring — unchanged)

At the time of writing, this was a recurring review of fix/mcp-resolved-error-breaker on an unchanged head. The most recent activity was a close/re-open solely to re-run the pull_request workflows against the new release; the single commit 5fc3021 was byte-identical to the content already reviewed. No code changed since the prior approval, so there was nothing new to inspect.

Accepted resolved findings (not re-raised)

Finding	State
toolDiscoveryService.ts — pass isErrorResultDetected to updateToolStats. In current code: this.updateToolStats(toolKey, !isErrorResultDetected, duration); thread resolved. ✅
test/continuous-test-suite-mcp-breaker-resolved-errors.ts — assertion-message interpolation. Now structural-only (no JSON.stringify(result)); thread resolved. ✅

New findings

None. Both review threads are resolved, and the latest CodeRabbit review generated no actionable comments.

[murdore]

Pre-merge gate results for this PR — 2 confirmed findings, both minor:

1. ExternalServerManager's totalErrors metric (and getExternalMCPStatistics()) wasn't updated for a resolved isError result, unlike the three sibling counters this PR already fixes — FIXED. executeTool() now increments instance.metrics.totalErrors when resolvedError is true. Test-first: the new assertion in test/continuous-test-suite-mcp-breaker-resolved-errors.ts failed 2/3 passed (1 failed) before the one-line fix, and passed 3/3 after it. Verified broken/fixed/restored on the new commit (a58bef223b9d9a274bac64271e5db52b9b6194c3): fixed 3 passed/0 failed/exit 0, broken 2 passed/1 failed/exit 1 (the F2 assertion fails as a genuine ✗, not a skip), restored 3 passed/0 failed/exit 0. Also re-run end-to-end through the public SDK surface (dist/index.js, not just the PR's own suite): both gate user-level scripts (happy-path.mjs, edge-and-unaffected.mjs) pass at the new HEAD, and happy-path.mjs's logged getExternalMCPStatistics() shows totalErrors:11 (10 resolved-isError calls + the 1 breaker-rejected call), which is exactly this fix made observable through the public API.
2. The latest "Yama PR Review" check run on this PR's pinned commit is red, but not from any unresolved review item — ANSWERED, NO CODE CHANGE. Both review threads are resolved and a formal APPROVED review stands for the exact commit; the red run is the known silent no-op from Yama PR Review reports success after reviewing nothing — its GitHub reads 404 against juspay/juspay #1754 (Yama's GitHub client reads the wrong repo slug), per that check run's own failure annotation. "Yama PR Review" is not a required status check on release, so it does not block merge.

All finalize-commit.sh gates (build, docs-api regen, check, lint, check:tools-tests, check:test-parse) and the Husky pre-commit hooks passed, un-bypassed, before this was committed as a single amended commit at a58bef223b9d9a274bac64271e5db52b9b6194c3.

[Tara-ag]

Verdict: APPROVE (recurring — unchanged)

Recurring review of fix/mcp-resolved-error-breaker on an already-merged PR (merged 2026-09-26). Both review threads (2/2) are resolved and this pass adds no new findings. The fix is sound: a resolved { isError: true } MCP result is counted as a breaker failure and a failed-completion telemetry sample, while the resolved payload is still returned to the caller unchanged (no synthesized transport error) — correct because such a result arrives on the protocol's success path.

Accepted resolved findings (not re-raised)

Finding	State
toolDiscoveryService.ts — pass isErrorResultDetected to updateToolStats. Verified in current code: this.updateToolStats(toolKey, !isErrorResultDetected, duration); thread resolved. ✅
test/continuous-test-suite-mcp-breaker-resolved-errors.ts — assertion-message interpolation. Now structural-only (isError !== true, no JSON.stringify(result)); thread resolved. ✅

Re-checked and clean

• Backward compatibility: execute() now accepts (recordResolvedFailure) => Promise<T>. Only executeTool passes the callback; the other call sites (mcpClientFactory.createClientOperation, discoverTools) pass zero-arg callbacks that still type-check and work. No unmodified caller breaks.
• No double-count: resolvedFailureReason is call-scoped; the resolved path returns right after recordFailureOutcome, and a callback that flags a resolved failure and throws still lands only in the catch path. recordFailureOutcome is behaviourally identical to the old inline catch bookkeeping.
• Telemetry coherence: breaker failedCalls, updateToolStats(…, false), recordMCPToolCall(success=false), and the externalServerManager totalErrors increment all agree on a resolved error.
• Concurrency: isErrorResultDetected/resolvedFailureReason are per-invocation locals — parallel execute calls on the same breaker can't cross-contaminate outcomes.
• Test math: failureThreshold: 3, minimumCallsBeforeCalculation: 10 → 10 resolved failures open the breaker; the fixture call-log proves the 11th call is short-circuited before reaching the server.

Non-blocking notes (carried, not new)

1. Every resolved isError now counts toward the tool-execution-* breaker regardless of severity — isError is not severity-classified, so a server legitimately resolving { isError: true } for benign "not found"-style cases will trip after minimumCallsBeforeCalculation and be blocked for the reset window. That is the stated intent; worth a follow-up if real servers resolve errors on their happy path.
2. CodeRabbit's docstring-coverage warning (33% vs 80%) on diff-touched functions remains soft/administrative.

No new or outstanding findings — clean approve on the merged state.

[github-actions]

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