fix(deepseek): apply DeepSeek compatibility to OpenCode Go routes

[SantiagoDePolonia]

Fixes #984.

DeepSeek request handling ran only on the deepseek provider, so DeepSeek models served by opencode_go (directly or via a virtual model) failed with reasoning_content and response_format errors. The handling runs in the provider request hook, which already fires after virtual-model routing, so no new routing phase is needed.

• Shared deepseek.AdaptCompatibility, applied by deepseek and by opencode_go for model IDs starting with deepseek.
• reasoning_content is now filled in on every earlier assistant turn when tools are present (not just tool-call turns), matching DeepSeek's thinking-mode docs. Client values are preserved.
• response_format: json_schema (including Responses text.format) follows new DEEPSEEK_JSON_SCHEMA_MODE:
  • downgrade (default): sends json_object and adds the schema as a system message, since DeepSeek JSON mode needs the prompt to describe the shape. Output is JSON but not schema-enforced.
  • error: returns invalid_request_error naming the provider and model.

The shared Responses → Chat translation is unchanged (it still attaches real reasoning to tool-call turns only) to avoid affecting other chat-translated providers; the padding covers DeepSeek.

Summary by CodeRabbit

• New Features

  • Added DeepSeek compatibility for structured JSON schema requests.
  • Requests can either downgrade to JSON object output with schema guidance or return an error, configurable through DEEPSEEK_JSON_SCHEMA_MODE.
  • Improved DeepSeek tool-call handling by preserving required reasoning information.
  • Applied the same behavior to DeepSeek models accessed through OpenCode Go.

• Documentation

  • Documented DeepSeek tool calls, reasoning behavior, structured outputs, and configuration options.
  • Added DeepSeek model and compatibility details to the OpenCode Go provider documentation.

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[coderabbitai]

📝 Walkthrough

Walkthrough

The change adds route-aware DeepSeek compatibility handling. It pads missing reasoning_content, adapts json_schema requests, supports configurable error or downgrade behavior, and applies these transformations to direct DeepSeek and OpenCode Go routes.

Changes

DeepSeek compatibility

Layer / File(s)	Summary
Compatibility adaptation internal/providers/deepseek/compat.go, internal/providers/deepseek/compat_test.go	Adds model detection, reasoning-content padding for tool requests, configurable JSON-schema downgrade or rejection, system instructions, and coverage for Chat Completions and Responses requests.
Provider and route integration internal/providers/deepseek/..., internal/providers/opencodego/..., .env.template, docs/providers/*.mdx	Applies compatibility handling to direct DeepSeek and resolved OpenCode Go DeepSeek models. Documents the DEEPSEEK_JSON_SCHEMA_MODE setting and the related behavior.

Priority: ➖ Normal

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

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant OpenCodeGo
  participant DeepSeekCompatibility
  participant DeepSeekAPI
  Client->>OpenCodeGo: Submit request for resolved model
  OpenCodeGo->>DeepSeekCompatibility: Apply DeepSeek compatibility
  DeepSeekCompatibility->>DeepSeekAPI: Send adapted request

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Merge Risk: 🟡 Moderate · up to 7999f

DeepSeek models routed through OpenCode Go’s Messages API do not receive the new tool-history or JSON-schema compatibility handling, so supported requests can fail instead of using the configured behavior. Resolve this routing gap before merging.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	Issue #984 requires the default behavior to avoid silently changing a client output contract unless the downgrade is explicitly configured. LoadJSONSchemaMode in `internal/providers/deepseek/compat.…	Make the safe behavior the default, such as JSONSchemaError, and require an explicit DEEPSEEK_JSON_SCHEMA_MODE=downgrade to change json_schema to json_object. Update the related tests and documentation to match.
Docstring Coverage	⚠️ Warning	Docstring coverage is 52.63% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 7 files. (3 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: applying DeepSeek compatibility handling to OpenCode Go routes.
Description check	✅ Passed	The description explains the problem, the affected providers and routes, the compatibility changes, configuration modes, and the reason for preserving Responses-to-Chat behavior. It does not include t…
Out of Scope Changes check	✅ Passed	The changed compatibility adapter, provider integrations, tests, environment documentation, and provider documentation all support issue #984 objectives. No unrelated change is demonstrated.

Full details: Linked Issues check

Explanation

Issue #984 requires the default behavior to avoid silently changing a client output contract unless the downgrade is explicitly configured. LoadJSONSchemaMode in internal/providers/deepseek/compat.go defaults unset and invalid DEEPSEEK_JSON_SCHEMA_MODE values to JSONSchemaDowngrade. This silently converts json_schema to json_object. The other requested behavior is implemented: AdaptCompatibility preserves existing reasoning_content, pads every historical assistant message when tools exist, and is applied to DeepSeek models in both the deepseek and route-aware opencode_go adapters. The structured-output error includes the provider and model.

Full details: Docstring Coverage

Explanation

Docstring coverage is 52.63% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 7 files. (3 skipped: 3 unsupported.)

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_{A rabbit saw schemas hop in line
Reasoning spaces kept the sign
DeepSeek routes now know the way
JSON modes choose what to say
OpenCode joins the gentle stream}

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Codecov Report

❌ Patch coverage is 92.45283% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/providers/deepseek/compat.go	93.18%	6 Missing ⚠️
internal/providers/deepseek/deepseek.go	81.81%	2 Missing ⚠️

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Actionable comments posted: 1

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Inline comments:
In `@internal/providers/opencodego/opencodego.go`:
- Line 123: Update Provider.ChatCompletion and Provider.StreamChatCompletion so
DeepSeek models selected through OPENCODE_GO_MESSAGES_MODELS still pass through
chatRequestAdapter and deepseek.AdaptCompatibility instead of calling p.messages
directly. Preserve DeepSeek reasoning_content padding for tool requests and its
configured JSON Schema handling for response_format requests.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 1e639077-62ad-4430-aeca-ce98398f7199

📥 Commits

Reviewing files that changed from the base of the PR and between b1de0a9 and 7999f05.

📒 Files selected for processing (10)

• .env.template
• docs/providers/deepseek.mdx
• docs/providers/opencode-go.mdx
• internal/providers/deepseek/compat.go
• internal/providers/deepseek/compat_test.go
• internal/providers/deepseek/deepseek.go
• internal/providers/deepseek/deepseek_test.go
• internal/providers/opencodego/deepseek.go
• internal/providers/opencodego/deepseek_test.go
• internal/providers/opencodego/opencodego.go

Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review.

[greptile-apps]

Confidence Score: 5/5

Safe to merge: the affected provider request paths preserve model-specific behavior and configuration choices.

What we checked:

• T-Rex compared the pre-change behavior to the post-change behavior, noting that before PR fix(deepseek): apply DeepSeek compatibility to OpenCode Go routes #985 the probe used unmodified json_schema, no reasoning_content, and DeepSeek-target assertions failed.
• T-Rex verified that after PR fix(deepseek): apply DeepSeek compatibility to OpenCode Go routes #985 DeepSeek paths now send json_object along with a schema system instruction, and reasoning_content is set to a single space.
• T-Rex confirmed that GLM paths retain json_schema and omit the reasoning_content field after the change.
• T-Rex validated that error-mode DeepSeek requests return HTTP 400 with an explicit unsupported-schema message and that OpenCode GLM reaches upstream with HTTP 200 OK.

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