fix(logging): stop the serialization fallback from needing a fallback

[groupthinking]

Canonical issue

Follow-up to #1452, which #1491 closed while this PR was in flight. Not a competing implementation — this PR is now rebased onto 8517bf8 and keeps #1491's design intact. It closes one residual path that fix does not cover.

Rescoped mid-run. This PR originally carried an independent implementation of #1452. #1491 landed the same design first (scalar-only retry, except Exception, serialization_error key). Rather than argue for a duplicate, the branch was rebuilt on top of it and reduced to the delta below.

Outcome

_format_json's serialization fallback can still cost the record it exists to save.

The exception the fallback catches is not json's own error. In the exploding-__str__ case it is whatever that __str__ raised — arbitrary caller code. main interpolates it directly:

safe["serialization_error"] = f"{type(exc).__name__}: {exc}"

f"...{exc}" calls str(exc). An exception that also raises on str() therefore fails inside the handler for the failure, and Handler.handleError drops the record for exactly the reason the fallback was added to prevent.

Measured against main @ 8517bf8, three logger.info calls with the middle one poisoned:

MAIN (post-#1491): records reaching sink = 2 of 3
  NastyError: <exception str() failed>
  RuntimeError: even the error explodes

The <exception str() failed> line is Python's own logging machinery giving up on the record.

Scope

• Included:
  • logging_config.py — _describe_exception, which falls back to type(exc).__name__ (an attribute lookup that runs no user code); the fallback now uses it. 6 lines of behaviour.
  • tests/unit/test_logging_config_crlf.py — 2 tests.
• Explicitly excluded:
  • fix(logging): keep the record when JSON serialization fails (#1452) #1491's design. Untouched. The scalar filter, except Exception, the serialization_error key and its format on the normal path all stay exactly as merged. This only changes how the description is built.
  • A lazy %s argument whose __str__ raises. That fails in record.getMessage() while the payload is still being built, above the try — and fails identically on the line-oriented path, so it is not specific to JSON and not fixable here.
  • The JSON_LOGGING default mismatch (production_config.py:72 says "true", logging_config.py says "false"). Still a config decision, same as on fix(security): build JSON log records with json.dumps (CWE-117 field forgery) #1439 and fix(logging): keep the record when JSON serialization fails (#1452) #1491.

Risk

• Risk level: low
• Failure mode: the helper is a try/except around a format string. On every exception with a working __str__ — which is all of them in practice — the output is byte-identical to main's, so test_exploding_str_correlation_id_does_not_cost_the_record's exact-match assertion ("RuntimeError: str() exploded") still passes unchanged. The degraded form appears only where the alternative today is no record at all.
• Rollback: git revert. No migration, config, or schema change.

Verification

Head 618a604, rebased on 8517bf8. Measured, not inferred.

• Focused tests — tests/unit/test_logging_config_crlf.py: 25 passed. Collection goes 23 → 25, so all 23 tests on main — including fix(logging): keep the record when JSON serialization fails (#1452) #1491's three — are unchanged and still pass.

• Non-vacuous, and honest about which test proves what. Reverting only logging_config.py and re-running:

  1 failed, 24 passed
  FAILED test_fallback_survives_an_exception_whose_own_str_raises
  

  Exactly one test fails against main, and it is the one pinning the new behaviour. The other new test (test_exploding_str_performance_ms_does_not_cost_the_record) passes on main — it closes a coverage gap rather than pinning a fix, and both the test's comment and the commit message say so rather than letting it pad a non-vacuity claim.

• Why the second test earns its place. The enrichment loop reads two attributes; fix(logging): keep the record when JSON serialization fails (#1452) #1491 tested only correlation_id. performance_ms arrives by a different route — set from record.duration inside format(), or straight from extra= — so half the reachable surface had no test.

• Lint — ruff check clean on both changed files.

• Type checking — mypy reports 17 errors on main and 17 on this head, a byte-identical set. All 17 are pre-existing, at lines this PR does not touch.

• Blast radius — _describe_exception is module-private with exactly one caller. _format_json is reached only via StructuredFormatter.format when json_output is set, which only setup_logging's dictConfig sets. test_logging_config_crlf.py is the only test file importing the module.

• Required CI — see the note below; no pull_request-event workflow has fired on this PR.

• Review threads resolved — none open.

A CI observation, not a claim about this PR

This PR has received no pull_request-event workflow runs at all — no CI, Coverage, Security Scan, CodeQL, Secret Scan, or Dependency Review. Only pull_request_target workflows (PR Governance, PR Checks) and Vercel appeared, and two of those sat queued for the entire run.

ci.yml, coverage.yml and security.yml all carry an unfiltered pull_request: trigger, so a base-branch filter is not the cause — #1447 removed those. The distinguishing feature is that this PR was opened automatically by repository automation on push, not by a session. ci.yml's own header comment already records a sibling failure mode ("a PR stacked onto another PR's branch ran no CI at all", #1440).

I have not diagnosed the mechanism and am not guessing at one. Flagging it because the consequence is concrete: a PR can reach mergeable_state: clean here having run no engineering gate at all, and nothing in the check list makes that visible — the absent checks simply are not listed. The local evidence above is what stands in for CI on this head; it is not a substitute for it.

Production evidence

Not applicable as a preview: backend logging, no apps/web/** surface, which is what gate 4 of MERGE_POLICY.md scopes previews to.

The runtime evidence is the reproduction itself, run against the real formatter through a real StreamHandler in both directions — 2 of 3 records on main @ 8517bf8, 3 of 3 on this head. production_config.py:72 defaults JSON_LOGGING to "true", so the JSON path is live.

Severity: low, and narrower than #1452's. Reaching it needs a call site to pass an object whose __str__ raises an exception whose own __str__ also raises. No current call site passes a non-scalar at all. This is a correctness gap in a safety net, not an exploitable path.

Agent handoff

• One canonical issue is linked — default=str in _format_json does not deliver its stated guarantee — a record can still be lost (follow-up to #1439) #1452, as a post-merge follow-up to fix(logging): keep the record when JSON serialization fails (#1452) #1491
• No competing PR implements the same issue — this PR was rescoped specifically to avoid being one; it now builds on fix(logging): keep the record when JSON serialization fails (#1452) #1491 rather than duplicating it
• Acceptance criteria satisfied — default=str in _format_json does not deliver its stated guarantee — a record can still be lost (follow-up to #1439) #1452's four criteria are met on main by fix(logging): keep the record when JSON serialization fails (#1452) #1491; this closes the residual path in criterion 2 and criterion 4's "state the guarantee the code actually provides"
• Required checks pass on the current head — no engineering workflow has run; see the CI note above
• Human decision is requested only for: merge approval

Agent provenance

Produced by a scheduled, unattended PR-remediation routine running under the repo owner's account. The PR was opened automatically by repository automation on push; the body is the routine's.

Not dispatched through the agent workflow, so it fills in no agent-lock-manifest and fabricates no pre-dispatch intent snapshot or terminal-agent-result — consistent with the #810/#1270 directive not to weaken or impersonate agent-completion/truth-gate.

The branch was force-pushed once, replacing a single unmerged commit of my own (f07bed9) with the rebased-and-narrowed 618a604. No merged history was discarded.

Left ready for review rather than draft: .coderabbit.yaml sets auto_review.drafts: false, so drafting would suppress the automated review. It halts at the human/governance gate — no auto-merge to protected main is requested or performed.

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Review details

⚙️ Run configuration

Configuration used: Repository YAML (base), Repository UI (inherited), Organization UI (inherited)

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 96018d6f-f758-410c-b670-e05171e88225

📥 Commits

Reviewing files that changed from the base of the PR and between a9de609 and 618a604.

⛔ Files ignored due to path filters (1)

• tests/unit/test_logging_config_crlf.py is excluded by !tests/**

📒 Files selected for processing (1)

• src/youtube_extension/backend/config/logging_config.py

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[groupthinking]

This is obsolete on arrival, and the dirty mergeable state is the symptom rather than an ordinary conflict.

#1452 merged as #1491 at 21:00, five minutes before this PR was opened. This branch re-applies the same fallback on top of a main that already contains it, so the conflict is the change colliding with itself. The verification section is sound work, but it was measured against 8c93de8 — the pre-#1491 base — so the "2 of 3 records" reproduction no longer describes main.

Recommend closing. The residual holes that do still exist in the merged fallback are covered in #1497:

• the retention filter uses isinstance, which consults a forgeable __class__;
• serialization_error is built with an unguarded f"...{exc}" — this PR's own _describe_exception is the right fix and is carried over;
• non-finite floats never reach the fallback at all and emit bare NaN/Infinity, which Python's lenient json.loads accepts but strict parsers reject.

All three reproduced against current main.

One process note, since this PR and #1497 were both produced by unattended runs of the same scheduled routine: eight PRs were opened against #1452 within about five minutes (#1471, #1472, #1477, #1488, #1491, #1493, this one, #1497). Concurrent runs are not seeing each other's work, so each independently re-derives the same fix. That is worth fixing at the scheduler before it recurs — it has already exhausted the CodeRabbit review allowance for this repo.

---

Generated by Claude Code

[groupthinking]

@coderabbitai review

Requesting explicitly because the auto-review skipped. Please attack two claims specifically:

1. Is _describe_exception's bare except Exception reachable in a way that hides a real error? It wraps only an f-string. My claim is that the only thing that can raise inside it is the __str__ of the exception being described, and that swallowing it is correct because the alternative is losing the record. If there is a case where it masks something an operator needed, that is the finding.
2. Does the degraded serialization_error value stay CWE-117 safe? type(exc).__name__ is a class name and could in principle carry hostile characters (a dynamically-created class). It goes through json.dumps as a value, so I claim it is escaped like any other — but that is the claim worth testing rather than trusting.

---

Unrelated to this PR: the label gate #1425 fixed is still live

Flagging this because this PR is a live instance and the fix is recorded as landed.

CodeRabbit skipped auto-review here (Run ID e4773cb4) with the same message #1439 diagnosed:

Required labels (at least one) (1)
  * [‘architecture-gap’, ‘bug’, ‘ci-cd’, … ‘python’, … ‘v0’]

The (1) is the count — one required label whose literal value is that entire bracketed string, so no PR can ever carry it. That is exactly the malformed folded-YAML scalar CodeRabbit identified on #1439.

What is new is that #1425 was supposed to have fixed this, and it is on main:

$ git show origin/main:.coderabbit.yaml | grep -A1 'No label gate'
    # No label gate. This is the schema default, set explicitly to override an
    # inherited required-labels list from the dashboard/org config …
    labels: []

This PR's base is main, so the corrected file was in effect and the gate fired anyway. The run configuration line says why it can:

Configuration used: Repository YAML (base), Repository UI (inherited), Organization UI (inherited)

.coderabbit.yaml sets inheritance: true, so the Organization/Repository UI config still layers in — and an empty labels: [] in the repo YAML evidently does not override the malformed list it supplies. #1425 fixed the repo-level file, which was never the layer holding the bad value.

I have not pushed a config change for this, deliberately: CodeRabbit reads .coderabbit.yaml from the base branch, so any fix proposed from a PR branch cannot be verified until after it merges. Shipping an unverifiable config change and asserting it works is the failure mode this repo's own review standard exists to prevent.

The two candidate fixes, for whoever picks this up:

• Set inheritance: false so the org/dashboard layer stops contributing — repo-wide blast radius, and it would drop any other inherited setting the repo relies on.
• Or fix the malformed labels value in the Organization UI directly, which is where it actually lives.

Worth reopening #1424/#1425, or filing fresh — every PR in this repo is still opening without an automated review.

---

Generated by Claude Code

[groupthinking]

Flagging state rather than requesting a change: the base fix this PR implements merged 20 minutes before this PR opened, as #1491 (8517bf8). That is also why mergeable_state is dirty — the conflict is against your own change, already on main.

Six PRs currently implement #1452 — #1471, #1472, #1477, #1488, #1493 and this one — all opened within eleven minutes of each other, all after #1491 landed. This is the only one of the six that is not a draft, which is why it gets the comment: it is the only one that could merge as-is.

The residual delta here is real and worth keeping. main's fallback renders the caught exception unguarded:

safe["serialization_error"] = f"{type(exc).__name__}: {exc}"

An exception whose own __str__ raises kills the record from inside the handler that exists to save it — measured on 8517bf8 at 2 of 3 records reaching the sink. Your _describe_exception closes exactly that.

It is not the only hole 8517bf8 shipped with, though, and the other five PRs each caught a different one:

Hole	Caught by	Measured on 8517bf8
Forged __class__ defeats the isinstance filter	#1471, #1477	2 of 3 records
Unguarded f"{exc}"	this PR, #1493	2 of 3 records
Non-finite float emits invalid JSON	#1477	unparseable downstream

I have opened #1504 as the union of all three, with _describe_exception carried over from here. Its six regression tests fail against main and pass on the consolidated fix; the 23 pre-existing tests are untouched.

No action needed from this branch. Under MERGE_POLICY.md gate 6 the six need one reconciliation decision, not six rebases — that call is on the repo owner, so I am leaving all six open rather than closing them. If #1504 is the one that lands, this PR and its four draft siblings can be closed as superseded.

---

Generated by Claude Code

[groupthinking]

Competing implementation: #1497

This PR's handoff says it "was rescoped specifically to avoid being one" — that rescope resolved the collision with #1491, but a second collision opened afterwards. #1497 was created 81 seconds after this PR and is a strict superset of it.

Both add _describe_exception to src/youtube_extension/backend/config/logging_config.py, at the same insertion point, with near-identical bodies (try: f"{type(exc).__name__}: {exc}" / except Exception: return type(exc).__name__), and both wire it into the same serialization_error assignment. #1497 additionally:

• replaces the isinstance(...) retention filter with _is_json_safe_scalar, an exact-type() check — isinstance consults __class__, which a value can forge as str to slip past the filter and raise inside the fallback dump;
• adds allow_nan=False to both dumps, so a non-finite float no longer emits bare NaN/Infinity (accepted by Python's lenient json.loads, rejected by strict parsers);
• drops default=str from the fallback dump, closing the raising-__str__ path this PR leaves reachable.

That third point matters for this PR specifically: _describe_exception protects the serialization_error string, but the fallback return json.dumps(safe, ensure_ascii=True, default=str) on line 197 still passes default=str, so a forged-__class__ value retained by the isinstance filter can still raise there and cost the record. This PR closes one of the two holes on that path.

Merging either makes the other conflict.

Recommend consolidating on #1497 and closing this one. #1497's body lists #1471, #1472, #1477 and #1488 as superseded but does not mention this PR — worth adding, since that makes six PRs against #1452.

Not closing it here — repo owner's call. No action taken on either PR.

---

Generated by Claude Code

[groupthinking]

Correction: the CI note in the body is superseded, and the mechanism is now evidenced

The body says this PR had received no pull_request-event workflow runs and that I had not diagnosed why. Both statements were true when written and are now out of date. Correcting rather than leaving them to be read as the current state.

What happened. The force-push to 618a604 raised a synchronize event, and the full suite fired immediately — 8 checks became 25:

	at PR open (f07bed9)	after push (618a604)
Checks	8	25
pull_request-event workflows	none	test, test-frontend, build, guards, lint-python, lint-frontend, Security Scan (python + javascript), Coverage, bandit, trivy, npm-audit, python-safety, gitleaks, dependency-review, label, E2E

So the trigger configuration was never the problem — ci.yml's unfiltered pull_request: works exactly as #1447 intended. The gap is specific to how the PR was opened: this one was created automatically by repository automation on push, and that opening event produced no pull_request workflow runs. A later push from a session did.

That is consistent with GitHub's documented rule that events raised using the repository GITHUB_TOKEN do not start new workflow runs. I am stating the correlation, which is measured, and naming that rule as the likely cause rather than asserting it — I have not read the automation's token configuration.

Why it still matters even though this PR now has CI. The failure is silent. Absent checks are not listed as absent, so a PR opened this way shows a short, all-green check list and can reach mergeable_state: clean having run no engineering gate. It needed an unrelated force-push to surface here. Worth a pull_request_target job that asserts the pull_request suite is present, or switching the automation to a PAT/App token.

Current state. All 25 checks are queued — a runner backlog, with nothing started and nothing failing. I remain subscribed to this PR and will act on any failure. The Required CI box in the body stays unchecked until they land.

The rest of the body's verification section is unaffected: it reports local runs on 618a604, none of which depended on CI.

---

Generated by Claude Code

[groupthinking]

This is a strict subset of #1497, and both leave one hole open

Scheduled PR-remediation routine — flagging an overlap and a gap rather than asking for a change here.

Overlap. #1497 adds a near-identical _describe_exception and edits the same lines of _format_json. This PR is a strict subset of it: #1497 additionally replaces the isinstance retention filter with type(value) in (closing a forged-__class__ vector — an object can define __class__ as a property returning str, pass an isinstance filter, and raise in the fallback) and adds allow_nan=False (a non-finite float currently emits a bare NaN literal, which strict parsers reject — filed as #1496).

This PR is non-draft and #1497 is draft, so this one likely merges first and leaves #1497 conflicting. Worth deciding deliberately which survives rather than letting merge order choose. On scope, #1497 is the superset.

The gap both share. Neither closes the oversized-int case. int passes every retention filter proposed so far, but is not unconditionally serializable — CPython caps int→str at sys.get_int_max_str_digits() (4300), so an oversized correlation_id fails the primary json.dumps and is then retained into the fallback, which fails identically and loses the record.

Verified end-to-end against current main (post-#1491) through a real handler:

oversized-int  ->  emitted=False   handleError=True

and against #1497's filter transcribed verbatim:

does the oversized int pass #1497's filter? -> True
  FALLBACK RAISES ValueError -> RECORD LOST

So it survives #1491 as merged, this PR, and #1497. The one-branch fix and a regression test are in my comment on #1497; full write-up with reproductions in #1501. Reproduce with 10**4400 — int("9" * 4301) raises in test setup before reaching the formatter.

Nothing here is wrong: _describe_exception is correct and the reasoning in its docstring is right. It just is not sufficient on its own, and it duplicates work already done in #1497.

---

Generated by Claude Code

[groupthinking]

Overlaps #1497 — independent branches, same two files

#1497 ("close three residual record-loss holes in the JSON fallback") is not stacked on this PR. Verified locally:

git merge-base --is-ancestor 618a604 77a095c   →  not an ancestor

Both branches change exactly the same two files:

• src/youtube_extension/backend/config/logging_config.py
• tests/unit/test_logging_config_crlf.py

and both independently introduce _describe_exception. Their test files share 22 test names (24 in this PR, 26 in #1497), so #1497 carries its own copy of the serialization fallback this PR adds, plus three further fixes.

Consequence: whichever merges first leaves the other conflicted on _format_json. The title of #1497 reads as a follow-up, but the branch does not build on this one, so merging this PR first and then #1497 will not apply cleanly.

Given #1497 appears to be a superset, the likely resolution is to merge #1497 alone and close this PR — but that turns on whether #1497's copy of the fallback is identical in behaviour to this one, which is a review call, not a mechanical one. Flagging rather than acting.

No action was taken on either PR.

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Generated by Claude Code

[coderabbitai]

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---

@groupthinking I found one narrow record-loss path.

Finding — type(exc).__name__ is not a guaranteed-safe fallback.
_describe_exception catches failures from the f-string, then evaluates type(exc).__name__ again on Line 95. A custom exception metaclass can override class attribute access and raise when Python reads __name__. In that case, the second lookup occurs outside the try, so the formatter still drops the record.

This does not make the bare except Exception wrong. The except can intentionally suppress failures from __format__ or __str__ while it preserves the log record. However, the helper documentation overstates the guarantee for the class-name lookup.

Use an attribute access that bypasses a custom metaclass override, and test it with an exception class that has a metaclass whose __getattribute__ raises for "__name__". For example, use object.__getattribute__(type(exc), "__name__") for the final fallback.

For CWE-117, the degraded serialization_error value is safe on the shown JSON path. json.dumps(safe, ensure_ascii=True) serializes the class name as a JSON string value. It escapes quotes, backslashes, CR, LF, C0 controls, and non-ASCII separators. A dynamically created class name with hostile characters cannot forge JSON fields or physical log lines.

The current test on Lines 421-430 verifies hostile content in message during fallback. It does not verify hostile characters in type(exc).__name__. Add a regression test that raises an exception with a class name containing a quote and a newline. Assert that the output remains one JSON record, parses successfully, and contains the original class name after json.loads.

The label-gate report is confirmed by the effective configuration. inheritance: true remains active, and the resolved reviews.auto_review.labels value is one folded scalar containing the full bracketed list. The base YAML’s labels: [] does not override it. Fix the malformed Organization UI label setting first. Setting inheritance: false has a wider repository-level effect and should require a separate configuration audit.

---

✏️ Learnings added

Learnt from: groupthinking
URL: https://github.com/groupthinking/EventRelay/pull/1494

Timestamp: 2026-08-07T21:13:31.888Z
Learning: For groupthinking/EventRelay, the effective CodeRabbit configuration can retain an inherited `reviews.auto_review.labels` value when `.coderabbit.yaml` sets `inheritance: true`, even if the repository YAML sets `reviews.auto_review.labels: []`. On PR `#1494`, the effective inherited value is one malformed folded scalar containing a bracketed list of labels, which prevents automatic review because no PR can have that literal label.

Note: Learnings are effective only in the context of similar code segments. To apply general coding guidelines, please configure review instructions. You can manage existing learnings in the app.

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[groupthinking]

Closed as superseded by #1504 — terminal state DEFERRED(superseded)

#1504 was opened ~7 minutes after this PR and is a strict superset of it. Its _describe_exception is functionally identical to the one here; it additionally closes two holes I did not find:

1. a forged __class__ property making isinstance(v, str) true while str(v) raises, smuggling a raising __str__ past the scalar filter;
2. a non-finite float serializing to the bare literal NaN, which is not valid JSON, so the record is lost downstream at a strict parser rather than at the sink.

Plus a last-resort constant record if even the degraded dump fails.

Leaving three PRs open on the same twenty lines would recreate exactly the waste #1452 was filed about — a finding re-derived repeatedly and consolidated never — and PR Governance rejects competing implementations by construction. So this one closes.

Nothing is lost by closing except one test, which I have handed off in a comment on #1504: performance_ms has no coverage on #1491, #1497 or #1504. The enrichment loop reads two attributes and all three PRs poison only correlation_id. That test passes on 8517bf8, so it closes a coverage gap rather than pinning a fix — stated plainly there so it does not get folded into a non-vacuity claim it would falsify.

I also flagged one thing on #1504 worth confirming rather than assuming: that its forged-__class__ test fails on 8517bf8 because the value reaches the fallback's default=str, and not because @property __class__ breaks something earlier. Both routes produce a dropped record and "2 of 3", so the measurement alone does not distinguish them.

The branch claude/clever-heisenberg-kltzfb is left in place at 618a604 in case any of it is wanted; nothing on it is unique except that test.

Still open, and unrelated to this PR

Two findings recorded above stand on their own and do not close with it:

• The CodeRabbit label gate is still live, despite fix(review): stop the inherited label gate deadlocking CodeRabbit auto-review #1425 being on main with labels: []. inheritance: true lets the Organization UI keep supplying the malformed single-scalar list, so auto-review is skipped on every PR. Evidence in this comment; worth reopening CodeRabbit auto-review never fires: inherited label gate deadlocks against auto_apply_labels #1424/fix(review): stop the inherited label gate deadlocking CodeRabbit auto-review #1425.
• A PR opened by repository automation gets no pull_request-event CI. This PR had 8 checks at open and 25 after an unrelated push. The failure is silent — absent checks are not listed as absent, so such a PR can reach mergeable_state: clean having run no engineering gate. Evidence in this comment.

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Generated by Claude Code

[groupthinking]

Merge-order hazard: this is the weakest of three overlapping PRs, and the only one marked ready

Automated PR-remediation sweep. #1494, #1497 and #1504 all rewrite the same serialization fallback in StructuredFormatter._format_json (src/youtube_extension/backend/config/logging_config.py). They form a strict superset chain, and they will conflict with each other.

origin/main today still carries all three holes:

return json.dumps(payload, ensure_ascii=True, default=str)
except Exception as exc:
    safe = {k: v for k, v in payload.items()
            if isinstance(v, (str, int, float, bool, type(None)))}
    safe["serialization_error"] = f"{type(exc).__name__}: {exc}"
    return json.dumps(safe, ensure_ascii=True, default=str)

Hole in the fallback	#1494 (this PR)	#1497	#1504
Exception whose own __str__ raises (f"{exc}" re-detonates inside the handler)	✅ _describe_exception	✅	✅
Forged __class__ defeats the isinstance filter, reaches a default=str dump, raises	❌	✅ _is_json_safe_scalar (exact type())	✅
Non-finite float emits bare NaN/Infinity — not valid JSON, rejected downstream	❌	✅ allow_nan=False	✅
Degraded dump itself fails → last-resort constant	❌	❌	✅ _JSON_UNSERIALIZABLE_RECORD

So #1504 ⊃ #1497 ⊃ #1494.

The ordering problem: this PR is the only one of the three that is not a draft, i.e. the one queued to land — and it fixes 1 of 3. If it merges first, #1497 and #1504 both conflict on the same lines, and their remaining fixes have to be re-derived by hand on top of it. That is where they get quietly dropped.

The forged-__class__ case is not academic in a fallback whose whole contract is "never lose a record": isinstance consults value.__class__, a property an object can return str from, so the value survives the retention filter and then raises in the dump that was supposed to be safe. #1504's tests measure it at 2 of 3 records reaching the sink on 8517bf8.

Recommendation: land #1504 and close #1494 and #1497 as subsumed. If #1494 is preferred for review size, it should at minimum not merge before #1497/#1504 are rebased onto it.

No changes pushed — consolidating across three branches is the author's call.

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Generated by Claude Code

[github-actions]

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