fix(server): Claude 5-series models always run 1M context

[juliusmarminge]

Closes #16904
Closes #8405
Follow-up to #16903.

The Claude Context Window option (200k / 1M) was a no-op on the 5-series. Picking 200k sent the bare slug, but Claude Code runs those models at 1M anyway, so the session ran 1M while T3 reported a 200k limit.

On the 4.6 models the option does work, so it stays there. Measured live with claude -p on Claude Code 2.1.293 (modelUsage.contextWindow):

Model	Bare slug	[1m]	Now
Fable 5 / 5.1, Opus 5.5 / 5, Sonnet 5.5 / 5, Haiku 5.5	1M	n/a	fixed 1M, option removed
Opus 4.8 / 4.7	1M	n/a	unchanged (already fixed 1M)
Opus 4.6	200k	1M	unchanged, option kept
Sonnet 4.6	200k	1M (needs API access)	unchanged, option kept
Opus 4.5, Haiku 4.5	200k	n/a	now declare fixed 200k

• The manifest drops the option, modelSuffixes, and contextWindowTokens from the five 5-series profiles and declares fixedContextWindowTokens: 1000000. Opus 4.5 and Haiku 4.5 declare 200k so the meter has a number.
• ClaudeAdapterV2 reads the window from the catalog instead of hard-coded Opus 4.6/4.7 checks and a 200k fallback. That fallback was wrong for any 1M model whose option was unset.
• A saved contextWindow selection on a 5-series thread is ignored, not an error. The web picker only shows the option when the model declares it. Mobile has no context window picker.
• No schema or resolver change, so released servers that fetch this manifest from main read it exactly as this build does.

Verified: Claude catalog, manifest, model options, text generation, and ClaudeAdapterV2 tests (197 pass), plus tsc --noEmit for apps/server with no errors.

Done by Claude Opus 5.5 in Claude Code.

🤖 Generated with Claude Code

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Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — The manifest changes product-facing context-window defaults and runtime token-limit reporting across multiple Claude models. Remote manifest refresh behavior also creates a plausible compatibility issue for older servers, particularly around Opus 4.6 model IDs and context limits.

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• apps/server/src/claudeModelOptions.test.ts
• apps/server/src/provider/ClaudeModelCatalog.ts

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📝 Walkthrough

Walkthrough

Claude model profiles replace selectable context-window options with fixed token counts. ClaudeAdapterV2 now returns the configured token count or null. The combined-options test checks Opus 4.6 with max effort, Fast Mode, and the [1m] model suffix.

Changes

Claude context-window configuration

Layer / File(s)	Summary
Fixed context-window profile configuration apps/server/src/provider/model-manifest.json	Claude profiles replace selectable context-window options and per-option token mappings with fixed counts of 1,000,000 or 200,000 tokens. Opus 4.6 uses a fixed [1m] suffix. The manifest timestamp advances.
Adapter resolution and model-option test apps/server/src/provider/ClaudeModelCatalog.ts, apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts, apps/server/src/claudeModelOptions.test.ts	ClaudeAdapterV2 returns the catalog token count or null. The context-window resolver is no longer exported. The combined-options test checks Opus 4.6 with max effort, Fast Mode, and the [1m] suffix.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~12 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: 🟡 Moderate · up to f496b

Released servers that refresh the manifest may report a 1M window for Opus 4.6 while invoking it without the suffix identified as necessary for 1M. Resolve that mismatch before merging.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The implementation does not fully match the requirements stated for linked issue #16904. That issue requires removing the context-window option from Opus 4.6 and Sonnet 4.6, while this pull request ke…	Reconcile the implementation with issue #16904 by removing the options and declaring fixed 1M windows for Opus 4.6 and Sonnet 4.6, or update the linked issue and obtain explicit maintainer approval for the changed scope.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Out of Scope Changes check	✅ Passed	The changes remain focused on Claude context-window configuration, catalog resolution, adapter behavior, and related tests. No unrelated changes are present.
Title check	✅ Passed	The title clearly summarizes the primary change: Claude 5-series models now use a fixed 1M context window.
Description check	✅ Passed	The description explains the problem, implementation, scope, linked issues, affected models, and focused verification results. It omits the template headings and does not include an explicit maintaine…

Full details: Linked Issues check

Explanation

The implementation does not fully match the requirements stated for linked issue #16904. That issue requires removing the context-window option from Opus 4.6 and Sonnet 4.6, while this pull request keeps both options.

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Inline comments:
Review comments at @apps/server/src/provider/model-manifest.json:
- Line 407: Update the Opus 4.6 manifest profile so servers that ignore
modelSuffix cannot pair the unsuffixed model ID with a 1M context window; gate
the 1M profile on suffix support or provide a compatible 200k context count for
older servers.

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📒 Files selected for processing (8)

• apps/server/src/claudeModelOptions.test.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
• apps/server/src/provider/ClaudeModelCatalog.test.ts
• apps/server/src/provider/ClaudeModelCatalog.testFixtures.ts
• apps/server/src/provider/ClaudeModelCatalog.ts
• apps/server/src/provider/ClaudeModelManifest.ts
• apps/server/src/provider/model-manifest.json
• apps/server/src/textGeneration/ClaudeTextGeneration.test.ts

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• apps/server/src/textGeneration/ClaudeTextGeneration.test.ts

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Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ The exact PR base did not have a successful artifact. Baseline uses the latest successful main measurement shown below.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	4.9 KiB	5.0 KiB	+23 B (+0.5%)	6.8 KiB	✅
Codex	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Codex	Live turn WebSocket wire	1.2 KiB	1.2 KiB	+23 B (+1.9%)	2.0 KiB	✅
Codex	Live turn WebSocket decoded	20.8 KiB	20.9 KiB	+41 B (+0.2%)	29.3 KiB	✅
Codex	Live turn messages	1	2	+1 (+100.0%)	8	✅
Claude	Total thread wire	5.0 KiB	5.0 KiB	−17 B (−0.3%)	6.8 KiB	✅
Claude	Thread snapshot wire	3.8 KiB	3.8 KiB	0 B (0.0%)	4.9 KiB	✅
Claude	Live turn WebSocket wire	1.2 KiB	1.2 KiB	−17 B (−1.4%)	2.0 KiB	✅
Claude	Live turn WebSocket decoded	21.2 KiB	21.2 KiB	0 B (0.0%)	29.3 KiB	✅
Claude	Live turn messages	2	2	0 (0.0%)	8	✅

Baseline: 250e052 · PR result: f496b59 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.