test: property-check context-overflow classification and synthetic SSE

[ndycode]

Summary

• Adds a fast-check property suite for lib/context-overflow.ts — the recovery path that turns "prompt too long" 400s into a synthetic SSE notice so the host session doesn't lock. The headline property is a round-trip oracle: the synthesizer's own output must parse as the Responses-API dialect and never re-classify as overflow.

What Changed

New test/property/context-overflow.property.test.ts (4 properties):

1. Phrase contract — the seven documented overflow phrases classify at any casing and any position inside generated noise, but only behind the 400 status gate. The phrase list is pinned verbatim, so silently dropping a pattern from the SUT fails here.
2. Negative space — noise-only bodies (hex + JSON punctuation, constructed so no pattern can occur) and empty bodies never classify, at any status 100–599.
3. Round-trip oracle — createContextOverflowResponse(model) returns a 200 with the synthetic headers, whose body parses line-by-line as valid SSE JSON in the Responses-API shape (response.created first, response.completed last, model echoed, the /compact notice in the terminal output payload — the recovery-01 dialect guarantee), and which is never re-classified as overflow by either the classifier or handleContextOverflow — the recovery path cannot recurse on its own output.
4. Interception exactness — handleContextOverflow handles exactly the classifier-positive 400s, and when it declines, the original response body remains readable (it reads a clone), so downstream error handling isn't starved.

No SUT bugs found.

Validation

• npm test -- test/property/context-overflow.property.test.ts test/context-overflow.test.ts — 26/26 (new 4 + existing 22 untouched)
• npm run typecheck (also via pre-commit hook)
• npx eslint test/property/context-overflow.property.test.ts --max-warnings=0

Docs and Governance Checklist

• Test-only; no behavior or docs surface changed

Risk and Rollback

• Risk level: minimal — additive test file; conventions match the existing test/property/ suites.
• Rollback plan: revert the single commit.

https://claude.ai/code/session_01XNtnkLbBiXZxfQQYLMpucB

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Generated by Claude Code

note: greptile review for oc-chatgpt-multi-auth. cite files like lib/foo.ts:123. confirm regression tests + windows concurrency/token redaction coverage.

Greptile Summary

additive property test suite for lib/context-overflow.ts — four fast-check properties covering phrase classification, negative-space safety, SSE round-trip correctness, and interception exactness. no sut changes.

• phrase contract + negative space (tests 1–2): arbNoise is restricted to hex chars + json punctuation, which provably excludes every overflow phrase, so false positives in the noise-only property are impossible by construction.
• round-trip oracle (test 3): correctly async/awaits the asyncProperty; body-consumption ordering is safe because handleContextOverflow short-circuits on status !== 400 before any clone, so calling synthetic.text() first doesn't leave the response unusable.
• interception exactness (test 4): accurately exercises the clone-not-consume contract; upstream.text() is only asserted in the decline path, consistent with the sut's response.clone().text() approach.

Confidence Score: 5/5

safe to merge — additive test file only, no sut changes, all four properties correctly awaited

single new test file with no production code changes. all async properties are properly awaited, the noise alphabet provably excludes every overflow phrase, body-consumption ordering is safe due to the status short-circuit in handleContextOverflow, and the round-trip oracle correctly validates the full SSE dialect contract including non-recursion. no regressions are possible from this change.

no files require special attention

Important Files Changed

Filename	Overview
test/property/context-overflow.property.test.ts	adds 4 fast-check property tests covering phrase contract, negative space, SSE round-trip oracle, and interception exactness; all four properties are correctly async-awaited, the noise alphabet provably excludes all overflow patterns, and the body-consumption ordering in the round-trip test is safe because the status guard short-circuits before any clone is attempted

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[property test invocation] --> B{test case}
    B --> C[test 1: phrase contract]
    B --> D[test 2: negative space]
    B --> E[test 3: round-trip oracle]
    B --> F[test 4: interception exactness]

    C --> C1[fc.constantFrom OVERFLOW_PATTERNS]
    C1 --> C2[arbCasing x3]
    C2 --> C3[arbNoise prefix + suffix]
    C3 --> C4[isContextOverflowError\nexpect true iff status=400]

    D --> D1[arbNoise only\nhex+JSON chars]
    D1 --> D2[fc.integer 100-599]
    D2 --> D3[isContextOverflowError\nexpect false always]

    E --> E1[createContextOverflowResponse model]
    E1 --> E2[parse SSE data lines]
    E2 --> E3{structure checks}
    E3 --> E4[payloads 0 = response.created]
    E3 --> E5[terminal = response.completed\nmodel echoed + /compact present]
    E3 --> E6[isContextOverflowError 200 body\nnever re-classifies]
    E3 --> E7[handleContextOverflow synthetic\nhandled=false, no recursion]

    F --> F1[new Response noise+pattern, status]
    F1 --> F2[handleContextOverflow]
    F2 --> F3{shouldHandle =\nstatus=400 && includePattern}
    F3 -->|true| F4[outcome.handled=true\nstatus=200 synthetic header]
    F3 -->|false| F5[outcome.handled=false\nupstream.text still readable]

Loading

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
test/property/context-overflow.property.test.ts:119-126
**test 4 noise suffix gap**

the body construction in this test is always `noise + pattern` (prefix-only), while test 1 wraps the pattern with both a `before` and `after` noise segment. because `arbNoise` is hex + punctuation and none of the overflow patterns are constructable from that alphabet, this never causes a spurious failure — but it does mean fast-check shrinks toward the fully suffix-free case and any future pattern that starts with hex chars (e.g., hypothetical `"404 token exceeded"`) could silently make this test fragile. adding a suffix via a second `arbNoise` arbitrary would match the test-1 pattern and future-proof against SUT changes that expand the phrase list.

_{Reviews (2): Last reviewed commit: "test: await the async round-trip propert..." | Re-trigger Greptile}

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 0d8e6e5d-c802-42c9-877b-5b18d1f89db6

📥 Commits

Reviewing files that changed from the base of the PR and between dae10cb and 203fd2b.

📒 Files selected for processing (1)

• test/property/context-overflow.property.test.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/audit-81-context-overflow-property

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch claude/audit-81-context-overflow-property

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