SDK: add includeCurrentDatetime flag to suppress datetime injection

Adds an opt-in `includeCurrentDatetime?: boolean` session/resume option
across all language bindings (Node, Python, Go, .NET, Rust, Java). When
`false`, the SDK forwards `includeCurrentDatetime: false` to the runtime,
which suppresses the injected `<current_datetime>` tag on model-facing
user messages. Defaults to true for backwards compatibility.

This is the SDK-side counterpart to copilot-agent-runtime PR
github/copilot-agent-runtime#8130, which is what actually does the
suppression work in the runtime. The combination is needed when short
prompts (e.g. session-name summarisation) are confused by datetime
context, or when the user's own prompt contains a date/time that
collides with the injected tag.

Surface added per language:

- Node:   `SessionConfigBase.includeCurrentDatetime?: boolean`
- Python: `create_session(..., include_current_datetime=...)` and
          `resume_session(..., include_current_datetime=...)`
- Go:     `SessionConfig.IncludeCurrentDatetime` /
          `ResumeSessionConfig.IncludeCurrentDatetime` (*bool)
- .NET:   `SessionConfigBase.IncludeCurrentDatetime` (bool?)
- Rust:   `SessionConfig.include_current_datetime` /
          `ResumeSessionConfig.include_current_datetime` plus
          `with_include_current_datetime` builder + wire fields
- Java:   `SessionConfig.includeCurrentDatetime` /
          `ResumeSessionConfig.includeCurrentDatetime` plus
          `SessionRequestBuilder.includeCurrentDatetime`, wire fields,
          and clone/jackson/builder unit tests

The wire field name is `includeCurrentDatetime` everywhere, matching
the runtime PR's request schema.

Verified locally with CONTRIBUTING.md test commands:

- nodejs: `npm test` 416 / 7 skipped; `npm run lint` 0 errors
- python: unit 145, ruff clean, e2e 283 / 7 pre-existing auth fails / 6
  skipped (failures unrelated to this change)
- go: `go test ./...` all pass; `golangci-lint run` 1 pre-existing
  govet in `definetool.go:210`
- dotnet: `dotnet test` 463 / 2 skipped
- rust: `cargo test --features test-support` all + 18 doctests pass
- java: custom E2E driver against gpt-5.2 (Halcyonhal9/lumi2 fork)

Refs: github/copilot-agent-runtime#8130

Co-authored-by: Copilot <[email protected]>

Author: Halcyonhal9

dotnet/src/Client.cs

@@ -618,7 +618,8 @@ public async Task<CopilotSession> CreateSessionAsync(SessionConfig config, Cance
                 GitHubToken: config.GitHubToken,
                 RemoteSession: config.RemoteSession,
                 Cloud: config.Cloud,
-                InstructionDirectories: config.InstructionDirectories);
+                InstructionDirectories: config.InstructionDirectories,
+                IncludeCurrentDatetime: config.IncludeCurrentDatetime);
 
             var rpcTimestamp = Stopwatch.GetTimestamp();
             var response = await InvokeRpcAsync<CreateSessionResponse>(
@@ -778,7 +779,8 @@ public async Task<CopilotSession> ResumeSessionAsync(string sessionId, ResumeSes
                 GitHubToken: config.GitHubToken,
                 RemoteSession: config.RemoteSession,
                 ContinuePendingWork: config.ContinuePendingWork,
-                InstructionDirectories: config.InstructionDirectories);
+                InstructionDirectories: config.InstructionDirectories,
+                IncludeCurrentDatetime: config.IncludeCurrentDatetime);
 
             var rpcTimestamp = Stopwatch.GetTimestamp();
             var response = await InvokeRpcAsync<ResumeSessionResponse>(
@@ -1866,7 +1868,8 @@ internal record CreateSessionRequest(
         string? GitHubToken = null,
         RemoteSessionMode? RemoteSession = null,
         CloudSessionOptions? Cloud = null,
-        IList<string>? InstructionDirectories = null);
+        IList<string>? InstructionDirectories = null,
+        bool? IncludeCurrentDatetime = null);
 
     internal record ToolDefinition(
         string Name,
@@ -1928,7 +1931,8 @@ internal record ResumeSessionRequest(
         string? GitHubToken = null,
         RemoteSessionMode? RemoteSession = null,
         bool? ContinuePendingWork = null,
-        IList<string>? InstructionDirectories = null);
+        IList<string>? InstructionDirectories = null,
+        bool? IncludeCurrentDatetime = null);
 
     internal record ResumeSessionResponse(
         string SessionId,

dotnet/src/Types.cs

@@ -2214,6 +2214,7 @@ protected SessionConfigBase(SessionConfigBase? other)
         OnUserInputRequest = other.OnUserInputRequest;
         Provider = other.Provider;
         EnableSessionTelemetry = other.EnableSessionTelemetry;
+        IncludeCurrentDatetime = other.IncludeCurrentDatetime;
         ReasoningEffort = other.ReasoningEffort;
         CreateSessionFsProvider = other.CreateSessionFsProvider;
         GitHubToken = other.GitHubToken;
@@ -2292,6 +2293,12 @@ protected SessionConfigBase(SessionConfigBase? other)
     /// </summary>
     public bool? EnableSessionTelemetry { get; set; }
 
+    /// <summary>
+    /// When false, suppresses current_datetime injection in the model-facing user message.
+    /// Defaults to true (datetime is included) when null.
+    /// </summary>
+    public bool? IncludeCurrentDatetime { get; set; }
+
     /// <summary>Handler for permission requests from the server.</summary>
     public Func<PermissionRequest, PermissionInvocation, Task<PermissionDecision>>? OnPermissionRequest { get; set; }
 

go/client.go

@@ -612,6 +612,7 @@ func (c *Client) CreateSession(ctx context.Context, config *SessionConfig) (*Ses
 	req.ExcludedTools = config.ExcludedTools
 	req.Provider = config.Provider
 	req.EnableSessionTelemetry = config.EnableSessionTelemetry
+	req.IncludeCurrentDatetime = config.IncludeCurrentDatetime
 	req.ModelCapabilities = config.ModelCapabilities
 	req.WorkingDirectory = config.WorkingDirectory
 	req.MCPServers = config.MCPServers
@@ -796,6 +797,7 @@ func (c *Client) ResumeSessionWithOptions(ctx context.Context, sessionID string,
 	req.Tools = config.Tools
 	req.Provider = config.Provider
 	req.EnableSessionTelemetry = config.EnableSessionTelemetry
+	req.IncludeCurrentDatetime = config.IncludeCurrentDatetime
 	req.ModelCapabilities = config.ModelCapabilities
 	req.AvailableTools = config.AvailableTools
 	req.ExcludedTools = config.ExcludedTools

go/types.go

@@ -870,6 +870,10 @@ type SessionConfig struct {
 	// regardless of this setting. This is independent of the OpenTelemetry
 	// configuration in ClientOptions.Telemetry.
 	EnableSessionTelemetry *bool
+	// IncludeCurrentDatetime includes the current local datetime in model-facing user messages.
+	// When false, suppresses the injected <current_datetime> tag. When nil, defaults
+	// to true for backwards compatibility.
+	IncludeCurrentDatetime *bool
 	// ModelCapabilities overrides individual model capabilities resolved by the runtime.
 	// Only non-nil fields are applied over the runtime-resolved capabilities.
 	ModelCapabilities *rpc.ModelCapabilitiesOverride
@@ -1084,6 +1088,10 @@ type ResumeSessionConfig struct {
 	// regardless of this setting. This is independent of the OpenTelemetry
 	// configuration in ClientOptions.Telemetry.
 	EnableSessionTelemetry *bool
+	// IncludeCurrentDatetime includes the current local datetime in model-facing user messages.
+	// When false, suppresses the injected <current_datetime> tag. When nil, defaults
+	// to true for backwards compatibility.
+	IncludeCurrentDatetime *bool
 	// ModelCapabilities overrides individual model capabilities resolved by the runtime.
 	// Only non-nil fields are applied over the runtime-resolved capabilities.
 	ModelCapabilities *rpc.ModelCapabilitiesOverride
@@ -1374,6 +1382,7 @@ type createSessionRequest struct {
 	ExcludedTools                  []string                       `json:"excludedTools,omitempty"`
 	Provider                       *ProviderConfig                `json:"provider,omitempty"`
 	EnableSessionTelemetry         *bool                          `json:"enableSessionTelemetry,omitempty"`
+	IncludeCurrentDatetime         *bool                          `json:"includeCurrentDatetime,omitempty"`
 	ModelCapabilities              *rpc.ModelCapabilitiesOverride `json:"modelCapabilities,omitempty"`
 	RequestPermission              *bool                          `json:"requestPermission,omitempty"`
 	RequestUserInput               *bool                          `json:"requestUserInput,omitempty"`
@@ -1428,6 +1437,7 @@ type resumeSessionRequest struct {
 	ExcludedTools                  []string                       `json:"excludedTools,omitempty"`
 	Provider                       *ProviderConfig                `json:"provider,omitempty"`
 	EnableSessionTelemetry         *bool                          `json:"enableSessionTelemetry,omitempty"`
+	IncludeCurrentDatetime         *bool                          `json:"includeCurrentDatetime,omitempty"`
 	ModelCapabilities              *rpc.ModelCapabilitiesOverride `json:"modelCapabilities,omitempty"`
 	RequestPermission              *bool                          `json:"requestPermission,omitempty"`
 	RequestUserInput               *bool                          `json:"requestUserInput,omitempty"`

java/src/main/java/com/github/copilot/sdk/SessionRequestBuilder.java

@@ -112,6 +112,7 @@ static CreateSessionRequest buildCreateRequest(SessionConfig config, String sess
         request.setExcludedTools(config.getExcludedTools());
         request.setProvider(config.getProvider());
         config.getEnableSessionTelemetry().ifPresent(request::setEnableSessionTelemetry);
+        config.getIncludeCurrentDatetime().ifPresent(request::setIncludeCurrentDatetime);
         if (config.getOnUserInputRequest() != null) {
             request.setRequestUserInput(true);
         }
@@ -203,6 +204,7 @@ static ResumeSessionRequest buildResumeRequest(String sessionId, ResumeSessionCo
         request.setExcludedTools(config.getExcludedTools());
         request.setProvider(config.getProvider());
         config.getEnableSessionTelemetry().ifPresent(request::setEnableSessionTelemetry);
+        config.getIncludeCurrentDatetime().ifPresent(request::setIncludeCurrentDatetime);
         if (config.getOnUserInputRequest() != null) {
             request.setRequestUserInput(true);
         }

java/src/main/java/com/github/copilot/sdk/json/CreateSessionRequest.java

@@ -55,6 +55,9 @@ public final class CreateSessionRequest {
     @JsonProperty("enableSessionTelemetry")
     private Boolean enableSessionTelemetry;
 
+    @JsonProperty("includeCurrentDatetime")
+    private Boolean includeCurrentDatetime;
+
     @JsonProperty("requestPermission")
     private Boolean requestPermission;
 
@@ -241,6 +244,25 @@ public void clearEnableSessionTelemetry() {
         this.enableSessionTelemetry = null;
     }
 
+    /** Gets include current datetime flag. @return the flag */
+    public Boolean getIncludeCurrentDatetime() {
+        return includeCurrentDatetime;
+    }
+
+    /**
+     * Sets include current datetime flag. @param includeCurrentDatetime the flag
+     */
+    public void setIncludeCurrentDatetime(Boolean includeCurrentDatetime) {
+        this.includeCurrentDatetime = includeCurrentDatetime;
+    }
+
+    /**
+     * Clears the includeCurrentDatetime setting, reverting to the default behavior.
+     */
+    public void clearIncludeCurrentDatetime() {
+        this.includeCurrentDatetime = null;
+    }
+
     /** Gets request permission flag. @return the flag */
     public Boolean getRequestPermission() {
         return requestPermission;

java/src/main/java/com/github/copilot/sdk/json/ResumeSessionConfig.java

@@ -46,6 +46,7 @@ public class ResumeSessionConfig {
     private List<String> excludedTools;
     private ProviderConfig provider;
     private Boolean enableSessionTelemetry;
+    private Boolean includeCurrentDatetime;
     private String reasoningEffort;
     private ModelCapabilitiesOverride modelCapabilities;
     private PermissionHandler onPermissionRequest;
@@ -279,6 +280,46 @@ public ResumeSessionConfig clearEnableSessionTelemetry() {
         return this;
     }
 
+    /**
+     * Gets whether the current local datetime is included in model-facing user
+     * messages.
+     *
+     * @return an {@link java.util.Optional} containing {@code true} to include the
+     *         current datetime or {@code false} to suppress it, or
+     *         {@link java.util.Optional#empty()} to use the runtime default
+     */
+    @JsonIgnore
+    public Optional<Boolean> getIncludeCurrentDatetime() {
+        return Optional.ofNullable(includeCurrentDatetime);
+    }
+
+    /**
+     * Sets whether to include the current local datetime in model-facing user
+     * messages.
+     * <p>
+     * When {@code false}, suppresses the injected {@code <current_datetime>} tag.
+     * Default: {@code true}.
+     *
+     * @param includeCurrentDatetime
+     *            {@code true} to include the current datetime, {@code false} to
+     *            suppress it, or {@code null} to use the runtime default
+     * @return this config for method chaining
+     */
+    public ResumeSessionConfig setIncludeCurrentDatetime(Boolean includeCurrentDatetime) {
+        this.includeCurrentDatetime = includeCurrentDatetime;
+        return this;
+    }
+
+    /**
+     * Clears the includeCurrentDatetime setting, reverting to the default behavior.
+     *
+     * @return this instance for method chaining
+     */
+    public ResumeSessionConfig clearIncludeCurrentDatetime() {
+        this.includeCurrentDatetime = null;
+        return this;
+    }
+
     /**
      * Gets the reasoning effort level.
      *
@@ -937,6 +978,7 @@ public ResumeSessionConfig clone() {
         copy.excludedTools = this.excludedTools != null ? new ArrayList<>(this.excludedTools) : null;
         copy.provider = this.provider;
         copy.enableSessionTelemetry = this.enableSessionTelemetry;
+        copy.includeCurrentDatetime = this.includeCurrentDatetime;
         copy.reasoningEffort = this.reasoningEffort;
         copy.modelCapabilities = this.modelCapabilities;
         copy.onPermissionRequest = this.onPermissionRequest;

java/src/main/java/com/github/copilot/sdk/json/ResumeSessionRequest.java

@@ -56,6 +56,9 @@ public final class ResumeSessionRequest {
     @JsonProperty("enableSessionTelemetry")
     private Boolean enableSessionTelemetry;
 
+    @JsonProperty("includeCurrentDatetime")
+    private Boolean includeCurrentDatetime;
+
     @JsonProperty("requestPermission")
     private Boolean requestPermission;
 
@@ -245,6 +248,25 @@ public void clearEnableSessionTelemetry() {
         this.enableSessionTelemetry = null;
     }
 
+    /** Gets include current datetime flag. @return the flag */
+    public Boolean getIncludeCurrentDatetime() {
+        return includeCurrentDatetime;
+    }
+
+    /**
+     * Sets include current datetime flag. @param includeCurrentDatetime the flag
+     */
+    public void setIncludeCurrentDatetime(Boolean includeCurrentDatetime) {
+        this.includeCurrentDatetime = includeCurrentDatetime;
+    }
+
+    /**
+     * Clears the includeCurrentDatetime setting, reverting to the default behavior.
+     */
+    public void clearIncludeCurrentDatetime() {
+        this.includeCurrentDatetime = null;
+    }
+
     /** Gets request permission flag. @return the flag */
     public Boolean getRequestPermission() {
         return requestPermission;

java/src/main/java/com/github/copilot/sdk/json/SessionConfig.java

@@ -48,6 +48,7 @@ public class SessionConfig {
     private List<String> excludedTools;
     private ProviderConfig provider;
     private Boolean enableSessionTelemetry;
+    private Boolean includeCurrentDatetime;
     private PermissionHandler onPermissionRequest;
     private UserInputHandler onUserInputRequest;
     private SessionHooks hooks;
@@ -334,6 +335,46 @@ public SessionConfig clearEnableSessionTelemetry() {
         return this;
     }
 
+    /**
+     * Gets whether the current local datetime is included in model-facing user
+     * messages.
+     *
+     * @return an {@link java.util.Optional} containing {@code true} to include the
+     *         current datetime or {@code false} to suppress it, or
+     *         {@link java.util.Optional#empty()} to use the runtime default
+     */
+    @JsonIgnore
+    public Optional<Boolean> getIncludeCurrentDatetime() {
+        return Optional.ofNullable(includeCurrentDatetime);
+    }
+
+    /**
+     * Sets whether to include the current local datetime in model-facing user
+     * messages.
+     * <p>
+     * When {@code false}, suppresses the injected {@code <current_datetime>} tag.
+     * Default: {@code true}.
+     *
+     * @param includeCurrentDatetime
+     *            {@code true} to include the current datetime, {@code false} to
+     *            suppress it, or {@code null} to use the runtime default
+     * @return this config instance for method chaining
+     */
+    public SessionConfig setIncludeCurrentDatetime(Boolean includeCurrentDatetime) {
+        this.includeCurrentDatetime = includeCurrentDatetime;
+        return this;
+    }
+
+    /**
+     * Clears the includeCurrentDatetime setting, reverting to the default behavior.
+     *
+     * @return this instance for method chaining
+     */
+    public SessionConfig clearIncludeCurrentDatetime() {
+        this.includeCurrentDatetime = null;
+        return this;
+    }
+
     /**
      * Gets the permission request handler.
      *
@@ -1033,6 +1074,7 @@ public SessionConfig clone() {
         copy.excludedTools = this.excludedTools != null ? new ArrayList<>(this.excludedTools) : null;
         copy.provider = this.provider;
         copy.enableSessionTelemetry = this.enableSessionTelemetry;
+        copy.includeCurrentDatetime = this.includeCurrentDatetime;
         copy.onPermissionRequest = this.onPermissionRequest;
         copy.onUserInputRequest = this.onUserInputRequest;
         copy.hooks = this.hooks;

java/src/test/java/com/github/copilot/sdk/ConfigCloneTest.java

@@ -215,6 +215,25 @@ void sessionConfigEnableSessionTelemetryDefaultIsNull() {
         assertTrue(cloned.getEnableSessionTelemetry().isEmpty());
     }
 
+    @Test
+    void sessionConfigIncludeCurrentDatetimeCopied() {
+        SessionConfig original = new SessionConfig();
+        original.setIncludeCurrentDatetime(false);
+
+        SessionConfig cloned = original.clone();
+
+        assertFalse(cloned.getIncludeCurrentDatetime().orElse(true));
+    }
+
+    @Test
+    void sessionConfigIncludeCurrentDatetimeDefaultIsNull() {
+        SessionConfig original = new SessionConfig();
+
+        SessionConfig cloned = original.clone();
+
+        assertTrue(cloned.getIncludeCurrentDatetime().isEmpty());
+    }
+
     @Test
     void resumeSessionConfigEnableSessionTelemetryCopied() {
         ResumeSessionConfig original = new ResumeSessionConfig();
@@ -234,6 +253,25 @@ void resumeSessionConfigEnableSessionTelemetryDefaultIsNull() {
         assertTrue(cloned.getEnableSessionTelemetry().isEmpty());
     }
 
+    @Test
+    void resumeSessionConfigIncludeCurrentDatetimeCopied() {
+        ResumeSessionConfig original = new ResumeSessionConfig();
+        original.setIncludeCurrentDatetime(false);
+
+        ResumeSessionConfig cloned = original.clone();
+
+        assertFalse(cloned.getIncludeCurrentDatetime().orElse(true));
+    }
+
+    @Test
+    void resumeSessionConfigIncludeCurrentDatetimeDefaultIsNull() {
+        ResumeSessionConfig original = new ResumeSessionConfig();
+
+        ResumeSessionConfig cloned = original.clone();
+
+        assertTrue(cloned.getIncludeCurrentDatetime().isEmpty());
+    }
+
     @Test
     void clonePreservesNullFields() {
         CopilotClientOptions opts = new CopilotClientOptions();